Water Quality Standards; Establishment of Numeric Criteria for Priority Toxic Pollutants for the State of California

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 131

[WH-FRL-5866-9]

RIN 2040-AC44

Water Quality Standards; Establishment of Numeric Criteria for

Priority Toxic Pollutants for the State of California

AGENCY: Environmental Protection Agency.

ACTION: Proposed rule.

-----------------------------------------------------------------------

SUMMARY: This rule proposes for the State of California, numeric water

quality criteria for priority toxic pollutants necessary to fulfill the

requirements of section 303(c)(2)(B) of the Clean Water Act (CWA) in

the State of California. This rule also proposes an authorizing

compliance schedule provision.

EPA is proposing this rule based on the Administrator's

determination that criteria are necessary in the State of California to

meet the requirements of CWA section 303(c)(2)(B). This section of the

CWA requires states to adopt numeric water quality criteria for

priority toxic pollutants for which EPA has issued CWA section 304(a)

criteria guidance and whose presence or discharge could reasonably be

expected to interfere with designated uses. Priority toxic pollutants

are identified in 40 CFR 131.36.

EPA is proposing this rule to fill a gap in California water

quality standards that was created in 1994 when a State Court

overturned the State's water quality control plans which contained

water quality criteria for priority toxic pollutants for which EPA had

issued CWA section 304(a) criteria guidance. Thus, the State of

California is currently without numeric water quality criteria for many

priority toxic pollutants as required by the CWA, necessitating this

action by EPA.

When these proposed federal criteria take effect, they will create

legally applicable water quality standards in the State of California

for inland surface waters, enclosed bays and estuaries for all purposes

and programs under the CWA.

DATES: All written comments received on or before September 26, 1997

will be considered in the preparation of the final rule. A public

hearing will be held on September 17, 1997, in San Francisco,

California, and on September 18, 1997, in Los Angeles, California. Both

oral and written comments will be accepted at the hearings.

ADDRESSES: Written comments should be addressed to Diane E. Frankel,

P.E., Esq., California Toxics Rule Project Manager, U.S. Environmental

Protection Agency, Region 9 (WTR-5), Water Management Division, 75

Hawthorne Street, San Francisco, California 94105.

Written comments are encouraged on paper or computer disk by mail.

Faxed comments will not be accepted. For comments on paper, an original

and two copies must be submitted. For computerized comments,

Wordperfect or ASCII format must be used. Comments previously submitted

for other Federal Register notices which are relevant to this notice

must be resubmitted in their entirety to be considered for this

proposed action.

A public hearing will be held at USEPA Region 9, 75 Hawthorne

Street, San Francisco, California, 94105, from 1-5 p.m. on September

17, 1997. A public hearing will also be held at the Los Angeles

Department of Water and Power, 111 North Hope Street, Los Angeles,

California, 90012, from 1-5 p.m. on September 18, 1997.

The public may inspect the administrative record for this

rulemaking, including documentation supporting the aquatic life and

human health criteria, at the U.S. Environmental Protection Agency,

Region 9, Water Management Division, 75 Hawthorne Street, San Francisco

94105 (telephone: 415-744-2125) on weekdays during the Agency's normal

business hours of 8:00 a.m. to 4:30 p.m. A reasonable fee will be

charged for photocopies.

FOR FURTHER INFORMATION CONTACT: Diane E. Frankel, P.E., Esq. or Philip

Woods, U.S. Environmental Protection Agency, Region 9 (WTR-5), Water

Management Division, 75 Hawthorne Street, San Francisco, California

94105, 415-744-2004 or 415-744-1997, respectively.

SUPPLEMENTARY INFORMATION: This preamble is organized according to the

following outline:

A. Introduction and Overview

1. Introduction

2. Overview

B. Statutory and Regulatory Background

C. State of California Actions and Compliance Regarding Section

303(c)(2)(B) of the Clean Water Act (CWA)

1. California Regional Water Quality Control Board Basin Plans,

and the Inland Surface Waters Plan (ISWP) and the Enclosed Bays and

Estuaries Plan (EBEP) of April 1991

2. EPA's Review of California Water Quality Standards for

Priority Toxic Pollutants in the ISWP and EBEP, and the National

Toxics Rule

3. Status of Implementation of CWA Section 303(c)(2)(B)

4. State-Adopted Site-Specific Priority Toxic Pollutant Criteria

D. Rationale and Approach For Developing the Proposed Rule

1. Legal Basis

2. Approach for Developing the Proposed Rule

E. Derivation of Criteria

1. Section 304(a) Criteria Guidance Process

2. Aquatic Life Criteria

a. Freshwater Criteria

b. Freshwater Acute Selenium Criterion

c. Dissolved Metals Criteria

d. Application of Metals Criteria

e. Saltwater Copper Criteria

f. Chronic Averaging Period

g. Hardness

3. Human Health Criteria

a. 2,3,7,8-TCDD (Dioxin) Criteria

b. Arsenic Criteria

c. Mercury Criteria

d. Polychlorinated Biphenyls (PCBs) Criteria

e. Section 304(a) Human Health Criteria Excluded

f. Cancer Risk Level

F. Description of the Proposed Rule

1. Scope

2. EPA Criteria for Priority Toxic Pollutants

3. Implementation

4. Wet Weather Flows

5. Schedules of Compliance

G. Executive Order (E.O.) 12866, Regulatory Planning and Review

1. Baselines

2. Costs

3. Benefits

H. Executive Order (E.O.) 12875, Enhancing the Intergovernmental

Partnership

I. The Unfunded Mandates Reform Act of 1995

J. The Regulatory Flexibility Act

K. The Paperwork Reduction Act

L. The Endangered Species Act

Potentially Affected Entities: Citizens concerned with water

quality in California may be interested in this rulemaking. Entities

discharging pollutants to waters of the United States in California

could be indirectly affected by this rulemaking since water quality

criteria are used to create water quality standards which in turn are

used in developing National Pollutant Discharge Elimination System

(NPDES) permit limits. Categories and entities which may ultimately be

indirectly affected include:

------------------------------------------------------------------------

Examples of potentially

Category indirectly affected entities

------------------------------------------------------------------------

Industry............................... Industries discharging

pollutants to surface waters

in California.

Municipalities......................... Publicly-owned treatment works

discharging pollutants to

surface waters in California.

------------------------------------------------------------------------

[[Page 42161]]

This table is not intended to be exhaustive, but rather provides a

guide for readers regarding NPDES regulated entities likely to be

indirectly affected by this action. This table lists the types of

entities that EPA is now aware could potentially be indirectly affected

by this action. If you have questions regarding this section consult

the person listed in the preceding FOR FURTHER INFORMATION CONTACT

section.

A. Introduction and Overview

1. Introduction

This section of the preamble introduces the topics which are

addressed below and provides a brief overview of EPA's basis and

rationale for proposing federal criteria for the State of California.

Section B briefly describes the evolution of the efforts to control

toxic pollutants; these efforts include the changes enacted in the 1987

CWA Amendments which are the basis for this rule. Section C summarizes

California's efforts since 1987 to implement the requirements of CWA

section 303(c)(2)(B) and describes EPA's procedure and actions for

determining whether California has fully implemented CWA section

303(c)(2)(B). Section D provides the rationale and approach for

developing the proposed rule, including a discussion of EPA's legal

basis for this proposal. Section E describes the development of the

criteria included in this rule. Section F summarizes the provisions of

the proposed rule and discusses implementation issues. Sections G, H,

I, J, K, and L briefly address the requirements of Executive Orders

12866 and 12875, the Unfunded Mandates Reform Act of 1995, the

Regulatory Flexibility Act, the Paperwork Reduction Act, and the

Endangered Species Act, respectively.

Since detailed information concerning many of the topics in this

preamble was published previously in the Federal Register in preambles

for other rulemakings, references are frequently made to those

preambles. Those rulemakings include: Water Quality Standards;

Establishment of Numeric Criteria for Priority Toxic Pollutants, 57 FR

60848, December 22, 1992 (referred to as the National Toxics Rule or

NTR); and the NTR as amended by Administrative Stay of Federal Water

Quality Criteria for Metals and Interim Final Rule, Water Quality

Standards; Establishment of Numeric Criteria for Priority Toxic

Pollutants; States' Compliance--Revision of Metals Criteria, 60 FR

22228, May 4, 1995 (referred to as the National Toxics Rule [NTR], as

amended). The NTR, as amended, is codified at 40 CFR 131.36. A copy of

the NTR, as amended, and its preambles are contained in the

administrative record for this rulemaking.

2. Overview

This proposed rule would establish ambient water quality criteria

for priority toxic pollutants in the State of California. The criteria

in this proposal would supplement the water quality criteria

promulgated for California in the NTR, as amended. In 1991, EPA

approved a number of water quality criteria (discussed in section C,

below), for the State of California. Since EPA had approved these

criteria, it was not necessary to include them in the NTR. However, the

EPA-approved criteria were subsequently invalidated in State

litigation. Thus, this proposal contains criteria to fill the gap

created by the State litigation.

This proposed rule does not change or supersede any criteria

previously promulgated for the State of California in the NTR, as

amended. Criteria which EPA promulgated for California in the NTR, as

amended, are footnoted in the proposed table at 131.38(b)(1), so that

when this proposed rule is promulgated, readers may see the criteria

promulgated in the NTR, as amended, for California and the criteria

promulgated through this rulemaking for California in the same table.

This proposed rule is not intended to apply to waters within Indian

Country. EPA recognizes that there are possibly waters located wholly

or partly in Indian Country that are included in the State's basin

plans. EPA will work with the State and Tribes to identify any such

waters and to seek comment from those entities on whether EPA should

include those waters in the final rulemaking or take other actions to

protect water quality in Indian Country. EPA also solicits comment from

the public on this approach.

This rule is important for several environmental, programmatic and

legal reasons. Control of toxic pollutants in surface waters is

necessary to achieve the CWA's goals and objectives. Many of

California's monitored river miles, lake acres, and estuarine waters

have elevated levels of toxic pollutants. Recent studies on California

water bodies indicate that elevated levels of toxic pollutants exist in

fish tissue which result in fishing advisories or bans. These toxic

pollutants can be attributed to, among other sources, industrial and

municipal discharges.

Water quality standards for toxic pollutants are important to State

and EPA efforts to address water quality problems. Clearly established

water quality goals enhance the effectiveness of many of the State's

and EPA's water programs including permitting, coastal water quality

improvement, fish tissue quality protection, nonpoint source controls,

drinking water quality protection, and ecological protection. Numeric

criteria for toxic pollutants allow the State and EPA to evaluate the

adequacy of existing and potential control measures to protect aquatic

ecosystems and human health. Numeric criteria also provide a more

precise basis for deriving water quality-based effluent limitations in

National Pollutant Discharge Elimination System (NPDES) permits to

control toxic pollutant discharges. Congress recognized these issues

when it enacted section 303(c)(2)(B) to the CWA.

While California recognizes the need for applicable water quality

standards for toxic pollutants, its adoption efforts have been stymied

by a variety of factors. The Administrator has determined that it must

exercise its CWA authorities to move forward the toxic control program,

consistent with the CWA and with the State of California's water

quality standards program.

EPA's action will also help restore equity among the states. The

CWA is designed to ensure all waters are sufficiently clean to protect

public health and/or the environment. The CWA allows some flexibility

and differences among states in their adopted and approved water

quality standards, but it should be implemented in a manner that

ensures a level playing field among states. Although California has

made important progress toward satisfying CWA requirements, it has not

satisfied CWA section 303(c)(2)(B) by adopting water quality standards

for toxic pollutants. This section was added to the CWA by Congress in

1987. The State of California is the only state in the Nation for which

CWA section 303(c)(2)(B) remains substantially unimplemented after

EPA's promulgation of the NTR in December of 1992. Section 303(c)(4) of

the CWA authorizes the EPA Administrator to promulgate standards where

necessary to meet the requirements of the Act. EPA has determined that

this rule is a necessary and important component for the implementation

of CWA section 303(c)(2)(B) in California.

EPA acknowledges that the State of California is working to satisfy

CWA section 303(c)(2)(B). When the State formally adopts criteria

consistent with its statutory requirements, as envisioned by Congress

in the CWA, EPA will act to stay its rule. When any judicial

[[Page 42162]]

review of such State standards is complete and sustains the State

standards, EPA will act to withdraw its rule.

B. Statutory and Regulatory Background

Section 303(c) of the 1972 Federal Water Pollution Control Act

Amendments (FWPCA) established the statutory basis for the current

water quality standards program. Although the major innovation of the

1972 FWPCA was technology-based controls, Congress maintained the

concept of water quality standards both as a mechanism to establish

goals for the Nation's waters and as a regulatory requirement when

standardized technology controls for point source discharges and/or

nonpoint source controls were inadequate.

Another major innovation in the 1972 FWPCA was the establishment of

the National Pollutant Discharge Elimination System (NPDES) which

requires point source dischargers to obtain a permit before legally

discharging to waters of the United States. In addition to the permit

limits established on the basis of technology (e.g. effluent

limitations guidelines), the Act requires permits to include more

stringent limits as necessary to meet instream water quality standards.

See CWA section 301(b)(1)(C).

Water quality standards are comprised of designated uses, criteria

to meet those uses, and an antidegradation policy. Water quality

standards serve two main functions: they allow for assessment of water

quality in a water body and they provide a basis for determining what

effluent discharge limitations may be allowed in order to protect the

designated uses of the water body.

In its initial efforts to control toxic pollutants, the FWPCA,

pursuant to section 307, required EPA to designate a list of toxic

pollutants and to establish toxic pollutant effluent standards based on

a formal rulemaking record. Such rulemaking required formal hearings.

EPA struggled with this unwieldy process and ultimately promulgated

effluent standards for six toxic pollutants, pollutant families or

mixtures. See 40 CFR Part 129. Congress amended section 307 in the 1977

CWA Amendments by endorsing the Agency's alternative procedure of

regulating toxic pollutants by use of technology-based effluent

limitations guidelines for toxic pollutants, by amending the procedure

for establishing toxic pollutant effluent standards to provide for more

flexibility in the hearing process for establishing a record, and by

directing the Agency to include sixty-five specific pollutants or

classes of pollutants on the toxic pollutant list. EPA published the

required list on January 31, 1978 (43 FR 4109). This toxic pollutant

list was the basis on which EPA focused its efforts on criteria

development for toxic pollutants.

EPA selected key chemicals of concern within the sixty-five

families of pollutants and identified a more specific list of 129

priority toxic pollutants. Two volatile chemicals and one water

unstable chemical were removed from the list (see 46 FR 2266, January

8, 1981; 46 FR 10723, February 4, 1981), so that at present, there are

126 priority toxic pollutants. This list appears in 40 CFR 131.36.

Another critical section of the 1972 FWPCA was section 304(a). CWA

section 304(a)(1) provides, in part, that EPA develop and publish

criteria guidance for water quality reflecting the latest scientific

knowledge on the kind and extent of all identifiable effects on health

and welfare including, but not limited to, plankton, fish, shellfish,

wildlife, plant life, shorelines, beaches, esthetics, and recreation

which may be expected from the presence of pollutants, and on the

effects of pollutants on biological community diversity, productivity,

etc.

In order to avoid confusion, it must be recognized that the CWA

uses the term ``criteria'' in two separate ways. In CWA section 303(c),

which is discussed above, the term is part of the definition of a water

quality standard. That is, a water quality standard is comprised of

designated uses and the criteria necessary to protect those uses. The

term ``criteria'' refers to the ambient component of the water quality

standard contained in state or federal law. However, CWA section

304(a)(1) directs EPA to publish water quality ``criteria'' guidance

which encompass scientific assessments of the health and ecological

effects of various pollutants listed pursuant to CWA section 307(a)(1)

and which are used to support development of ambient criteria as part

of water quality standards. CWA section 304(a) criteria guidance are

intended as guidance only and have no binding effect. States may

consider these criteria guidance in adopting regulatory criteria.

To implement CWA section 304(a)(1), EPA initially produced a series

of scientific water quality criteria guidance documents. EPA's most

recently published criteria documents are summarized in one document

entitled, Quality Criteria for Water 1986 (1986 ``Gold Book''). EPA has

updated many of the criteria since publication of the 1986 Gold Book.

EPA's criteria guidance (both the earlier documents and updates

including those in the Agency's Integrated Risk Information System

[IRIS]), provide a comprehensive toxicological evaluation of each

chemical and the individual criteria recommendations, as updated, are

the official guidance. For toxic pollutants, the recommendations

tabulate the relevant acute and chronic toxicity information for

aquatic life and derive the criteria maximum concentrations (acute

criteria) and criteria continuous concentrations (chronic criteria)

which the Agency recommends to protect aquatic life resources. For

human health criteria, the recommendations provide the appropriate

reference doses, and if appropriate, the carcinogenic slope factors,

and derives recommended criteria. The details of this process are

discussed in a later part of this preamble.

Criteria documents, along with any more recent scientific data and

information, may be used to interpret a state's narrative criterion

pursuant to 40 CFR 122.44(d)(1)(vi), and serve to establish State and

EPA permit discharge limits pursuant to CWA section 301(b)(1)(C) which

requires NPDES permits to contain limitations required to implement any

applicable water quality standard established in the CWA.

In support of the November, 1983 water quality standards

rulemaking, EPA issued program guidance entitled, Water Quality

Standards Handbook (December 1983) simultaneously with the publication

of the final rule. The forward to that guidance noted EPA's two-fold

water quality based approach to controlling toxic pollutants: chemical

specific numeric criteria and biological testing in whole effluent or

ambient waters to comply with narrative ``no toxics in toxic amounts''

standards. More detailed programmatic guidance on the application of

biological testing was provided in the Technical Support Document for

Water Quality-Based Toxics Control (TSD) (EPA 440/4-85-032, September

1985). This document provided the needed information to convert

chemical specific and biologically based criteria into water quality

standards for ambient receiving waters and permit limits for discharges

to those waters. The TSD focused on the use of toxicity testing of

effluent (whole effluent testing or WET methods) to develop effluent

limitations within discharge permits. Such effluent limits were

designed to implement the ``free from toxicity'' narrative standards in

state water quality standards. The TSD also focused on water quality

standards. Procedures and policy were presented

[[Page 42163]]

for appropriate design flows for EPA's section 304(a) acute and chronic

criteria. In 1991, EPA revised and expanded the TSD. (Technical Support

Document for Water Quality-Based Toxics Control (TSD), (EPA 505/2-90-

001, March 1991).) A notice of availability was published in the

Federal Register on April 4, 1991 (56 FR 13827). All references in this

preamble are to the revised TSD.

In 1987, Congress enacted stringent new water quality standard

provisions in the Water Quality Act amendments. The 1987 Amendments to

the CWA (P.L. 100-4) added section 303(c)(2)(B) which provides:

Whenever a State reviews water quality standards pursuant to

paragraph (1) of this subsection, or revises or adopts new standards

pursuant to this paragraph, such State shall adopt criteria for all

toxic pollutants listed pursuant to section 307(a)(1) of this Act

for which criteria have been published under section 304(a), the

discharge or presence of which in the affected waters could

reasonably be expected to interfere with those designated uses

adopted by the State, as necessary to support such designated uses.

Such criteria shall be specific numerical criteria for such toxic

pollutants. Where such numerical criteria are not available,

whenever a State reviews water quality standards pursuant to

paragraph (1), or revises or adopts new standards pursuant to this

paragraph, such State shall adopt criteria based on biological

monitoring or assessment methods consistent with information

published pursuant to section 304(a)(8). Nothing in this section

shall be construed to limit or delay the use of effluent limitations

or other permit conditions based on or involving biological

monitoring or assessment methods or previously adopted numerical

criteria.

The addition of this new requirement to the existing water quality

standards review and revision process of CWA section 303(c) did not

change the existing procedural or timing provisions. CWA section

303(c)(1) still required that states review their water quality

standards at least once each three year period and transmit the results

to EPA for review. EPA's oversight and promulgation authorities and

statutory schedules in CWA section 303(c)(4) were likewise unchanged.

Rather, the provision required the states to place heavy emphasis on

adopting numeric chemical-specific criteria for toxic pollutants

(rather than narrative approaches) during the next triennial review.

Congress was frustrated that states were not using the numerous CWA

section 304(a) criteria guidance that EPA had and was continuing to

develop, to assist states in controlling the discharge of priority

toxic pollutants. Accordingly, Congress explicitly mandated that states

adopt numeric criteria for toxic pollutants where the discharge or

presence of such pollutants could reasonably be expected to interfere

with such designated uses.

In response to this requirement, EPA strengthened its efforts to

assist state adoption of water quality standards for priority toxic

pollutants. This included developing and issuing guidance for states on

acceptable implementation procedures for several new sections of the

CWA, including sections 303(c)(2)(B) and 304(l). EPA, in devising

guidance for CWA section 303(c)(2)(B), attempted to provide states the

maximum flexibility that complied with the express statutory language

but also with the overriding Congressional objective: Prompt adoption

and implementation of numeric toxic pollutant criteria where necessary

to protect designated uses. EPA believed that flexibility was important

so that each state could satisfy CWA section 303(c)(2)(B) and to the

extent possible, accommodate its existing water quality standards

regulatory approach. EPA's program guidance was issued in final form on

December 12, 1988 and the availability of the guidance was published in

a Federal Register notice on January 5, 1989 (54 FR 346).

EPA's section 303(c)(2)(B) program guidance identified several

options that could be used by a state to meet the requirement that the

state adopt toxic pollutant criteria ``* * *the discharge or presence

of which in the affected waters could reasonably be expected to

interfere with those designated uses adopted by the State, as necessary

to support such designated uses.'' These options are fully discussed in

the guidance and in the preamble to the National Toxics Rule (NTR) at

57 FR 60853. One option is for a state to adopt statewide numeric

criteria for all section 307(a) toxic pollutants for which EPA has

developed section 304(a) criteria guidance, regardless of whether the

pollutants are known to be present. This option is the most

comprehensive approach to satisfy the statutory requirement, and

ensures comprehensive coverage of the priority toxic pollutants with

scientifically defensible criteria. This option would not impose more

effluent limits on dischargers than any other option, because permit

limits would only be based on the regulation of the particular toxic

pollutants in their discharge and not on the total listing in the water

quality standards. Actual permit limits should be the same under any

option.

EPA's December 1988 guidance also stated that all state standards

triennial reviews initiated after passage of the amended CWA must

include a consideration of numeric toxic criteria.

Beyond the increased Congressional and public concern about the

relative importance of toxic pollutant controls, there was increased

evidence of toxic pollution problems in our Nation's waters. In

response, in 1992, EPA promulgated the NTR pursuant to CWA section

303(c)(4)(B) and 40 CFR 131.22(b) to rectify program deficiencies in 14

states, including the State of California. The State of California was

included for specific pollutants and for specific water bodies which

corresponded with EPA's disapproval in November 1991 of a portion of

each of two statewide plans. EPA did not promulgate criteria for those

portions of the statewide plans which it approved.

Today's action proposes to add priority toxic pollutant criteria

applicable to inland surface waters, enclosed bays and estuaries within

the State of California.

C. State of California Actions and Compliance Regarding Section

303(c)(2)(B) of the Clean Water Act (CWA)

1. California Regional Water Quality Control Board Basin Plans, and the

Inland Surface Waters Plan (ISWP) and the Enclosed Bays and Estuaries

Plan (EBEP) of April 1991

The State of California regulates water quality through its State

Water Resource Control Board (SWRCB) and through nine Regional Water

Quality Control Boards (RWQCBs). Each of the nine RWQCBs represents a

different geographic area; area boundaries are generally along

watershed boundaries. Each RWQCB maintains a Basin Plan which contains

the designated uses of the water bodies within its respective

geographic area within California. These designated uses (or

``beneficial uses'' under State law) together with legally-adopted

criteria (or ``objectives'' under State law), comprise water quality

standards for the water bodies within each of the Basin areas. Each of

the nine RWQCBs undergoes a triennial Basin Planning review process, in

compliance with CWA section 303. The SWRCB provides assistance to the

RWQCBs.

Most of the Basin Plans contain conventional pollutant objectives

such as dissolved oxygen. None of the Basin Plans contains a

comprehensive list of priority toxic pollutant criteria to satisfy CWA

section 303(c)(2)(B). The nine RWQCBs and the SWRCB had intended that

the priority toxic pollutant criteria contained in the three SWRCB

statewide plans, the Inland Surface Water Plan (ISWP), the Enclosed Bay

and Estuary

[[Page 42164]]

Plan (EBEP), and the Ocean Plan, apply to all Basins and satisfy CWA

section 303(c)(2)(B).

On April 11, 1991, the SWRCB adopted two statewide water quality

control plans, the ISWP and the EBEP. These statewide plans contained

narrative and numeric water quality criteria for toxic pollutants, in

part to satisfy CWA section 303(c)(2)(B). The water quality criteria

contained in the SWRCB statewide plans, together with the designated

uses in each of the Basin Plans, created a set of water quality

standards for waters within for the State of California.

Specifically, the two plans established water quality criteria or

objectives for all fresh waters, bays and estuaries in the State. The

plans contained water quality criteria for some priority toxic

pollutants, provisions relating to whole effluent toxicity,

implementation procedures for point and nonpoint sources, and

authorizing compliance schedule provisions. The plans also included

special provisions affecting waters dominated by reclaimed water

(labeled as Category (a) waters), and waters dominated by agricultural

drainage and constructed agricultural drains (labeled as Category (b)

and (c) waters, respectively).

2. EPA's Review of California Water Quality Standards for Priority

Toxic Pollutants in the ISWP and EBEP, and the National Toxics Rule

The EPA Administrator has delegated the responsibility and

authority for review and approval or disapproval of all new or revised

state water quality standards to the EPA Regional Administrators (see

40 CFR 131.21). Thus, state actions under CWA section 303(c)(2)(B) are

submitted to the appropriate EPA Regional Administrator for review and

approval.

In mid-April 1991, the SWRCB submitted to EPA for review and

approval the two statewide water quality control plans--the ISWP and

the EBEP. On November 6, 1991, EPA Region 9 formally concluded its

review of the SWRCB's plans. EPA approved the narrative water quality

criterion and the toxicity criterion in each of the plans. EPA also

approved the numeric water quality criteria contained in both plans,

finding them to be consistent with the requirements of section

303(c)(2)(B) of the CWA and with EPA's national criteria guidance

published pursuant to section 304(a) of the CWA.

EPA noted the lack of criteria for some pollutants, and found that,

because of the omissions, the plans did not fully satisfy CWA section

303(c)(2)(B). The plans did not contain criteria for all listed

pollutants for which EPA had published national criteria guidance. The

ISWP contained human health criteria for only 65 pollutants, and the

EBEP contained human health criteria for only 61 pollutants for which

EPA had issued section 304(a) guidance criteria. Both the ISWP and EBEP

contained aquatic life criteria for all pollutants except cyanide and

chromium III (freshwater only) for which EPA has CWA section 304(a)

criteria guidance. The SWRCB's administrative record stated that all

priority pollutants with EPA criteria guidance were likely to be

present in California waters. However, the SWRCB's record contained

insufficient information to support a finding that the excluded

pollutants were not reasonably expected to interfere with designated

uses of the waters of the State.

Although EPA approved the statewide selenium objective in the ISWP

and EBEP, EPA disapproved the criteria for the San Francisco Bay and

Delta, because there was clear evidence that the criteria would not

protect the designated fish and wildlife uses (the California

Department of Health Services had issued waterfowl consumption

advisories due to selenium concentrations, and scientific studies had

documented selenium toxicity to fish and wildlife). EPA restated its

commitment to object to National Pollutant Discharge Elimination System

(NPDES) permits issued for San Francisco Bay that contained effluent

limits based on an objective greater than 5 ppb (four day average) and

20 ppb (1 hour average), the freshwater criteria. EPA reaffirmed its

disapproval of site-specific selenium criteria for portions of the San

Joaquin River, Salt Slough, and Mud Slough. EPA also disapproved of the

categorical deferrals and exemptions. These disapprovals included the

disapproval of the State's deferral of water quality objectives to

effluent dominated streams (Category a) and to streams dominated by

agricultural drainage (Category b), and the disapproval of the

exemption of water quality objectives to constructed agricultural

drains (Category c). EPA found the definitions of the categories

imprecise and overly broad which could have led to an incorrect

interpretation.

Since EPA had disapproved portions of each of the California

statewide plans which were necessary to satisfy CWA section

303(c)(2)(B), California was included in EPA's promulgation of the

National Toxics Rule (NTR) (40 CFR 131.36, 57 FR 60848). EPA

promulgated specific criteria for certain water bodies in California.

The NTR was amended, effective April 14, 1995, to stay certain

metals criteria which had been promulgated as total recoverable;

effective April 15, 1995, EPA promulgated interim final metals criteria

as dissolved concentrations for those metals which had been stayed

(Administrative Stay of Federal Water Quality Criteria for Metals and

Interim Final Rule, Water Quality Standards; Establishment of Numeric

Criteria for Priority Toxic Pollutants; States' Compliance--Revision of

Metals Criteria; 60 FR 22228, May 4, 1995 [the NTR, as amended]). The

stay was in response to a lawsuit against EPA challenging, among other

issues, metals criteria expressed as total recoverable concentrations.

A partial Settlement Agreement required EPA to stay specific metals

criteria in the NTR. EPA then promulgated certain metals criteria in

the dissolved form through the use of conversion factors. These factors

are listed in the NTR, as amended. A scientific discussion of these

criteria is found in the next section.

Since certain criteria have already been promulgated for specific

water bodies in the State of California in the NTR, as amended, they

are not within the scope of today's proposed rule. However, for clarity

in reading a comprehensive rule for the State of California, these

criteria are incorporated in proposed 40 CFR 131.38(d)(2). Footnotes to

the Table in proposed 40 CFR 131.38(b)(1) and proposed 40 CFR

131.38(d)(3) clarify which criteria (and for which specific water

bodies) have been promulgated by the NTR, as amended, and are therefore

excluded from this proposed rule. The appropriate (freshwater or

saltwater) aquatic life criteria which were promulgated in the NTR, as

amended, for all inland surface waters and enclosed bays and estuaries

include: chromium III and cyanide. The appropriate (water and organism

or organism only) human health criteria which were promulgated in the

NTR, as amended, for all inland surface waters and enclosed bays and

estuaries include: antimony; thallium; asbestos; acrolein;

acrylonitrile; carbon tetrachloride; chlorobenzene; 1,2-dichloroethane;

1,1-dichloroethylene; 1,3-dichloropropylene; ethylbenzene; 1,1,2,2-

tetrachloroethane; tetrachloroethylene; 1,1,2-trichloroethane;

trichloroethylene; vinyl chloride; 2,4-dichlorophenol; 2-methyl-4,6-

dinitrophenol; 2,4-dinitrophenol; benzidine; bis(2-chloroethyl)ether;

bis(2-ethylhexyl)phthalate; 3,3-dichlorobenzidine; diethyl phthalate;

[[Page 42165]]

dimethyl phthalate; di-n-butyl phthalate; 2,4-dinitrotoluene; 1,2-

diphenylhydrazine; hexachlorobutadiene; hexachlorocyclopentadiene;

hexachloroethane; isophorone; nitrobenzene; n-nitrosodimethylamine; and

n-nitrosodiphenylamine. Other pollutant criteria were promulgated in

the NTR, as amended, for specific water bodies, but not all inland

surface waters and enclosed bays and estuaries.

3. Status of Implementation of CWA Section 303(c)(2)(B)

Shortly after the SWRCB adopted the ISWP and EBEP, several

dischargers filed suit against the State alleging that it had not

adopted the two plans in compliance with State law. The plaintiffs in a

consolidated case included: the County of Sacramento, Sacramento County

Water Agency; Sacramento Regional County Sanitation District; the City

of Sacramento; the City of Sunnyvale; the City of San Jose; the City of

Stockton; and Simpson Paper Company.

The dischargers alleged that the State had not adopted the ISWP and

EBEP in compliance with the California Administrative Procedures Act

(Gov Code. Section 11340, et seq.), the California Environmental

Quality Act (Pub. Re Code, Section 21000, et seq.), and the Porter-

Cologne Act (Wat. Code, Section 13200, et seq.). The allegation that

the State did not sufficiently consider economics when adopting water

quality objectives, as allegedly required by Section 13241 of the

Porter Cologne Act, was an important issue in the litigation.

In October of 1993, the Superior Court of California, County of

Sacramento, issued a tentative decision in favor of the dischargers. In

March of 1994, the Court issued a substantively similar final decision

in favor of the dischargers. Final judgments from the Court in July of

1994 ordered the SWRCB to rescind the ISWP and EBEP. On September 22,

1994, the SWRCB formally rescinded the two statewide water quality

control plans. The State is currently in the process of readopting

water quality control plans for inland surface waters, enclosed bays

and estuaries.

CWA section 303(c)(2)(B) was fully implemented in the State of

California from December of 1992, when the NTR was promulgated, until

September of 1994, when the SWRCB was required to rescind the ISWP and

EBEP. The provisions for California in EPA's NTR together with the

approved portions of California's ISWP and EBEP implemented the

requirements of CWA section 303(c)(2)(B). However, since September of

1994, when the SWRCB rescinded the ISWP and EBEP, the requirements of

section 303(c)(2)(B) have not been fully implemented in California.

The scope of today's rule is to re-establish criteria for the

remaining priority toxic pollutants to meet the requirements of section

303(c)(2)(B) of the CWA. Pursuant to section 303(c)(4), the

Administrator has determined that it is necessary to include in today's

proposed action criteria for priority toxic pollutants, which are not

covered by the NTR, as amended, or by the State through site-specific

criteria, for waters of the United States in the State of California.

4. State-Adopted Site-Specific Priority Toxic Pollutant Criteria

The State has the discretion to develop site-specific criteria when

appropriate e.g., when statewide criteria appear over- or under-

protective of designated uses. Periodically, the State through its

RWQCBs will adopt site-specific criteria for priority toxic pollutants

within respective Basin Plans. These criteria are intended to be

effective throughout the Basin or throughout a designated water body.

Under California law, these criteria must be publicly reviewed and

approved by the RWQCB, the SWRCB, and the State's Office of

Administrative Law (OAL). Once this adoption process is complete, the

criteria become State law.

These criteria must be submitted to the EPA Regional Administrator

for review and approval under CWA section 303. These criteria are

usually submitted to EPA as part of a RWQCB Basin Plan Amendment, after

the Amendment has been adopted under the State's process and has become

State law.

State-Adopted Site-Specific Criteria Under EPA Review: Basin Plan

Updates: The State of California has recently reviewed and updated all

of its RWQCB Basin Plans. All of these Basin Plans have completed the

State review and adoption process and have been submitted to EPA for

review and approval. Some of the Basin Plans contain site-specific

criteria. In these cases, the State-adopted site-specific criteria are

used for water quality programs.

EPA Region 9 intends to make a determination on all State-adopted,

site-specific criteria that are currently under EPA review. If, after

this proposal, but before promulgation of this final rule, EPA approves

any State-adopted site-specific criteria, the EPA Administrator may

make a finding in the final rule that it will be unnecessary to

promulgate criteria for those site-specific pollutants and associated

water bodies. If EPA disapproves any State-adopted site-specific

criteria, today's proposed statewide criteria would apply for those

pollutants and associated water bodies.

However, if EPA promulgates statewide federal criteria as proposed

in this rule, prior to a decision on any State-adopted site-specific

criteria, the more stringent of the two criteria would be used for

water quality programs. Both federal and State water quality programs

must be satisfied, and application of the more stringent of the two

criteria would satisfy both.

Santa Ana River: EPA is currently reviewing State-adopted site-

specific criteria for copper, cadmium and lead for portions of the

Santa Ana River. These criteria are contained in the Santa Ana Region

Basin Plan Amendments (RWQCB for the Santa Ana Region). EPA intends to

complete its review and make a final determination on these site-

specific criteria prior to the promulgation of this rule.

If EPA approves the State-adopted site-specific criteria, the EPA

Administrator can make a finding in the final rule that it will be

unnecessary to promulgate federal criteria for those site-specific

pollutants and associated water bodies. If EPA disapproves the State-

adopted site-specific criteria, today's proposed statewide criteria,

when promulgated final, would apply for those pollutants and water

bodies.

State-Adopted Site-Specific Criteria with EPA Approval: In several

cases, the EPA Regional Administrator has reviewed and approved of

State-adopted site-specific criteria within the State of California.

Three of these cases are discussed below separately.

Unfortunately, EPA does not have a complete listing of all of the

site-specific criteria that may remain in place as State law after the

State court decision vacated the ISWP and the EBEP. Consequently, EPA

is proposing these criteria for all waters, except for those discussed

below in the preamble and cited in the regulatory text. If the State or

another member of the public, as confirmed by the State, indicates in

comments that there is a site-specific, State criterion that was

approved by EPA and continues to be an appropriate value, EPA would

amend the regulatory text of the final rule such that the otherwise

applicable criteria would not apply in that instance.

Sacramento River: EPA has approved site-specific criteria for

copper, cadmium and zinc in the Sacramento River, upstream of Hamilton

City, in the

[[Page 42166]]

Central Valley Region (RWQCB for the Central Valley Region) of the

State of California. EPA approved these site-specific criteria by

letter dated August 7, 1985. Specifically, EPA approved for the

Sacramento River (and tributaries) above Hamilton City, a copper

criterion of 5.6 g/l (maximum), a zinc criterion of 16

g/l (maximum) and a cadmium criterion of 0.22 g/l

(maximum), all in the dissolved form using a hardness of 40 mg/l as

CaCO3. (These criteria were actually adopted by the State

and approved by EPA as equations which vary with hardness.) These

``maximum'' criteria correspond to acute criteria in today's proposed

rule. Therefore, federal acute criteria for copper, cadmium, and zinc

for the Sacramento River (and tributaries) above Hamilton City are not

necessary to protect the designated uses and are not included in the

proposed rule. However, the EPA Administrator is making a finding that

it is necessary to include chronic criteria for copper, cadmium and

zinc for the Sacramento River (and tributaries) above Hamilton City, as

part of the proposed statewide criteria in today's proposed rule.

San Joaquin River: Site-specific selenium criteria in portions of

the San Joaquin River, in the Central Valley Region, are not included

in this proposed rule because they either have been previously approved

by EPA or promulgated by EPA as part of the NTR. EPA approved and

disapproved State-adopted site-specific selenium criteria in portions

of the San Joaquin River, in the Central Valley Region of the State of

California (RWQCB for the Central Valley Region). EPA's determination

on these site-specific criteria is contained in a letter dated April

13, 1990.

Specifically, EPA approved for the San Joaquin River, mouth of

Merced River to Vernalis, an aquatic life selenium criterion of 12

g/l (maximum with the understanding that the instantaneous

maximum concentration may not exceed the objective more than once every

three years). Today's proposed rule does not affect this federally-

approved, State-adopted site-specific acute criterion, and it remains

in effect for the San Joaquin River, mouth of Merced River to Vernalis.

Therefore, an acute criterion for selenium in the San Joaquin River,

mouth of Merced River to Vernalis is not necessary to protect the

designated use and thus is not included in the proposed rule.

By letter dated April 13, 1990, EPA also approved for the San

Joaquin River, mouth of Merced River to Vernalis, a State-adopted site-

specific aquatic life selenium criterion of 5 g/l (monthly

mean); however, EPA disapproved a State-adopted site-specific selenium

criterion of 8 g/l (monthly mean--critical year only) for

these waters. Subsequently, EPA promulgated a chronic selenium

criterion of 5 g/l (4 day average) for waters of the San

Joaquin River from the mouth of the Merced River to Vernalis in the

NTR. This chronic criterion applies to all water quality programs

concerning the San Joaquin River, mouth of Merced River to Vernalis.

Today's proposed rule does not affect the federally-promulgated chronic

selenium criterion of 5 g/l (4 day average) set forth in the

NTR. This previously federally-promulgated criterion remains in effect

for the San Joaquin River, mouth of Merced River to Vernalis.

Grassland Water District, San Luis National Wildlife Refuge, and

Los Banos State Wildlife Refuge: EPA approved for the Grassland Water

District, San Luis National Wildlife Refuge, and Los Banos State

Wildlife Refuge, a State-adopted site-specific aquatic life selenium

criterion of 2 g/l (monthly mean) by letter dated April 13,

1990. This federally-approved, State-adopted site-specific chronic

criterion remains in effect for the Grassland Water District, San Luis

National Wildlife Refuge and Los Banos State Wildlife Refuge. Therefore

it is not necessary to include in today's proposed rule, a chronic

criterion for selenium for the Grassland Water District, San Luis

National Wildlife Refuge and Los Banos State Wildlife Refuge.

D. Rationale and Approach for Developing the Proposed Rule

This section explains EPA's legal basis for today's proposed rule,

and discusses EPA's general approach for developing the specific

requirements for the State of California.

In addition to Congressional directive, there are a number of

environmental and programmatic reasons why establishing water quality

standards for toxic pollutants in California is important. Control of

toxic pollutants in surface waters is critical to the success of a

number of CWA programs and objectives, including permitting, fish

tissue quality protection, coastal water quality improvement, sediment

contamination control, certain nonpoint source controls, pollution

prevention planning, and ecological protection.

1. Legal Basis

CWA section 303(c) specifies that adoption of water quality

standards is primarily the responsibility of the states. However, CWA

section 303(c) also describes a role for the federal government to

oversee state actions to ensure compliance with CWA requirements. If

EPA's review of the states' standards finds flaws or omissions, then

the CWA authorizes EPA to correct the deficiencies (see CWA section

303(c)(4)). This water quality standards promulgation authority has

been used by EPA to issue final rules on several separate occasions,

including the NTR, as amended, which promulgated criteria similar to

those included here for a number of states. These actions have

addressed both insufficiently protective state criteria and/or

designated uses and failure to adopt needed criteria. Thus, today's

action is not unique.

The CWA in section 303(c)(4) provides two bases for promulgation of

federal water quality standards. The first basis, in paragraph (A),

applies when a state submits new or revised standards that EPA

determines are not consistent with the applicable requirements of the

CWA. If, after EPA's disapproval, the state does not amend its rules so

as to be consistent with the CWA, EPA is to promptly propose

appropriate federal water quality standards for that state. The second

basis for an EPA action is in paragraph (B), which provides that EPA

shall promptly initiate promulgation ``* * * in any case where the

Administrator determines that a revised or new standard is necessary to

meet the requirements of this Act.'' EPA is using section 303(c)(4)(B)

as the legal basis for this proposed rule.

As stated in the preamble to the NTR, the Administrator's

determination under CWA section 303(c)(4) that criteria are necessary

to meet the requirements of the Act could be supported in several ways.

EPA does not believe that it is necessary to support the criteria

proposed today on a pollutant-specific, water body-by-water-body basis.

For EPA to undertake an effort to conduct research and studies of each

stream segment or water body across the State of California to

demonstrate that for each toxic pollutant for which EPA has issued CWA

section 304(a) criteria guidance there is a ``discharge or presence''

of that pollutant which could reasonably ``be expected to interfere

with'' the designated use would impose an enormous administrative

burden and would be contrary to the statutory directive for swift

action manifested by the 1987 addition of section 303(c)(2)(B) to the

CWA.

Consistent with EPA's approach in the NTR, EPA interprets section

303(c)(2)(B) of the CWA to allow EPA to act where the State has not

succeeded in establishing numeric water quality standards for toxic

pollutants. This

[[Page 42167]]

inaction can be the basis for the Administrator's determination under

section 303(c)(4) that new or revised criteria are necessary to ensure

designated uses are protected. Here, this determination is buttressed

by the evidence in the record for the rule of the discharge or presence

of priority toxic pollutants in the State's waters for which the State

does not have numeric water quality criteria.

EPA's interpretation of section 303(c)(2)(B) is supported by the

language of the provision, the statutory framework and purpose of

section 303, and the legislative history. In adding section

303(c)(2)(B) to the CWA, Congress understood the existing requirements

in section 303(c)(1) for triennial water quality standards review and

submissions and in section 303(c)(4)(B) for promulgation. CWA section

303(c) includes numerous deadlines and section 303(c)(4) directs the

Administrator to act ``promptly'' where the Administrator determines

that a revised or new standard is necessary to meet the requirements of

the Act. Congress, by linking section 303(c)(2)(B) to the section

303(c)(1) three-year review period, gave States a last chance to

correct this deficiency on their own. The legislative history of the

provision demonstrates that chief Senate sponsors, including Senators

Stafford, Chaffee and others wanted the provision to eliminate State

and EPA delays and force quick action. Thus, to interpret CWA section

303(c)(2)(B) and (c)(4) to require such a cumbersome pollutant specific

effort on each stream segment would essentially render section

303(c)(2)(B) meaningless. The provision and its legislative background

indicate that the Administrator's determination to invoke her section

303(c)(4)(B) authority can be met by a generic finding of inaction by

the State without the need to develop pollutant specific data for

individual stream segments.

This determination is supported by information in the rulemaking

record showing the discharge or presence of priority toxic pollutants

throughout the State. While this data is not necessarily complete, it

constitutes a strong record supporting the need for numeric criteria

for priority toxic pollutants with section 304(a) criteria guidance

where the State does not have numeric criteria.

Today's proposed rule would not impose any undue or inappropriate

burden on the State of California or its dischargers. It merely puts in

place numeric criteria for toxic pollutants that are already utilized

in other states in implementing CWA programs. Under this rulemaking,

the State of California retains the ability to adopt alternative water

quality criteria simply by completing its criteria adoption process.

Upon EPA approval of those criteria, EPA will initiate action to stay

the federally-promulgated criteria.

2. Approach for Developing the Proposed Rule

In summary, EPA developed the criteria proposed in today's rule as

follows. Where EPA promulgated criteria for California in the NTR, as

amended, EPA has not acted to amend the criteria in the NTR, as

amended. Where criteria for California were not included in the NTR, as

amended, EPA used section 304(a) national criteria guidance documents

as a basis for the criteria proposed in this rule. EPA then determined

whether new information since the development of the national criteria

guidance documents warranted any changes. New information came from two

sources. For human health criteria, new or revised risk reference doses

and cancer potency factors on EPA's Integrated Risk Information System

(IRIS) as of October 1996 form the basis for criteria values different

from the national criteria guidance documents. For aquatic life

criteria, updated data sets resulting in revised criteria maximum

concentrations (CMCs) and criteria continuous concentrations (CCCs)

formed the basis for differences from the national criteria guidance

documents. Both of these types of changes are discussed in more detail

in the following section. This revised information was used to develop

the water quality criteria proposed here for the State of California.

E. Derivation of Criteria

1. Section 304(a) Criteria Guidance Process

Under CWA section 304(a), EPA has developed methodologies and

specific criteria guidance to protect aquatic life and human health.

These methodologies are intended to provide protection for all surface

waters on a national basis. The methodologies have been subject to

public review, as have the individual criteria guidance documents.

Additionally, the methodologies have been reviewed and approved by

EPA's Science Advisory Board (SAB) of external experts.

EPA has included in the record of this rule the aquatic life

methodology as described in ``Appendix B--Guidelines for Deriving Water

Quality Criteria for the Protection of Aquatic Life and Its Uses'' to

the ``Water Quality Criteria Documents; Availability'' (45 FR 79341,

November 28, 1980) as amended by the ``Summary of Revisions to

Guidelines for Deriving Numerical National Water Quality Criteria for

the Protection of Aquatic Organisms and Their Uses'' (50 FR 30792, July

29, 1985). (Note: Throughout the remainder of this preamble, this

reference is described as the 1985 Guidelines. Any page number

references are to the actual guidance document, not the notice of

availability in the Federal Register. A copy of the 1985 Guidelines is

available through the National Technical Information Service (PB85-

227049), is in the administrative record for this rule, and is

abstracted in Appendix A of Quality Criteria for Water, 1986.) EPA has

also included in the administrative record of this rule the human

health methodology as described in ``Appendix C--Guidelines and

Methodology Used in the Preparation of Health Effects Assessment

Chapters of the Consent Decree Water Criteria Documents'' (45 FR 79347,

November 28, 1980). (Note: Throughout the remainder of this preamble,

this reference is described as the Human Health Guidelines or the 1980

Guidelines.) EPA also recommends that the following be reviewed:

``Appendix D--Response to Comments on Guidelines for Deriving Water

Quality Criteria for the Protection of Aquatic Life and Its Uses,'' (45

FR 79357, November 28, 1980); ``Appendix E--Responses to Public

Comments on the Human Health Effects Methodology for Deriving Ambient

Water Quality Criteria'' (45 FR 79368, November 28, 1980); and

``Appendix B--Response to Comments on Guidelines for Deriving Numerical

National Water Quality Criteria for the Protection of Aquatic Organisms

and Their Uses'' (50 FR 30793, July 29, 1985). EPA placed into the

administrative record for this rulemaking the most current individual

criteria guidance for the priority toxic pollutants included in today's

rule. (Note: All references to appendices are to the associated Federal

Register publication.)

2. Aquatic Life Criteria

Aquatic life criteria may be expressed in numeric or narrative

form. EPA's 1985 Guidelines describe an objective, internally

consistent and appropriate way of deriving chemical-specific, numeric

water quality criteria for the protection of the presence of, as well

as the uses of, both fresh and marine water aquatic organisms.

An aquatic life criterion derived using EPA's CWA section 304(a)

method ``might be thought of as an estimate of the highest

concentration of a substance in water which does not present a

significant risk to the aquatic organisms

[[Page 42168]]

in the water and their uses.'' (45 FR 79341.) The term ``their uses''

refers to consumption by humans and wildlife (1985 Guidelines, page

48). EPA's guidelines are designed to derive criteria that protect

aquatic communities by protecting most of the species and their uses

most of the time, but not necessarily all of the species all of the

time (1985 Guidelines, page 1). EPA's 1985 Guidelines attempt to

provide a reasonable and adequate amount of protection with only a

small possibility of substantial overprotection or underprotection. As

discussed in detail below, there are several individual factors which

may make the criteria somewhat overprotective or underprotective. The

approach EPA is using is believed to be as well balanced as possible,

given the state of the science.

Numerical aquatic life criteria derived using EPA's 1985 Guidelines

are expressed as short-term and long-term numbers, rather than one

number, in order that the criteria more accurately reflect

toxicological and practical realities. The combination of a criteria

maximum concentration (CMC), a short-term concentration acute limit,

and a criteria continuous concentration (CCC), a four-day average

concentration chronic limit, provide protection of aquatic life and its

uses from acute and chronic toxicity to animals and plants, and from

bioconcentration by aquatic organisms, without being as restrictive as

a one-number criterion would have to be. (1985 Guidelines, pages 4, 5.)

The terms CMC and CCC are the scientifically correct names for the two

(acute and chronic) values of a criterion for a pollutant; however,

this document will also refer to acute criterion and chronic criterion

to which they are more commonly referred.

The two-number criteria are intended to identify average pollutant

concentrations which will produce water quality generally suited to

maintenance of aquatic life and their uses while restricting the

duration of excursions over the average so that total exposures will

not cause unacceptable adverse effects. Merely specifying an average

value over a time period is insufficient unless the time period is

short, because excursions higher than the average can kill or cause

substantial damage in short periods.

A minimum data set of eight specified families is required for

criteria development (details are given in the 1985 Guidelines, page

22). The eight specific families are intended to be representative of a

wide spectrum of aquatic life. For this reason it is not necessary that

the specific organisms tested be actually present in the water body.

States may develop site-specific criteria using native species,

provided that the broad spectrum represented by the eight families is

maintained. All aquatic organisms and their common uses are meant to be

considered, but not necessarily protected, if relevant data are

available.

EPA's application of guidelines to develop the criteria matrix in

the proposed rule is judged by the Agency to be applicable to all

waters of the United States, and to all ecosystems (1985 Guidelines,

page 4). There are waters and ecosystems where site-specific criteria

could be developed, as discussed below, but the State should identify

those waters and develop the appropriate site-specific criteria.

Fresh water and salt water (including both estuarine and marine

waters) have different chemical compositions, and freshwater and

saltwater species rarely inhabit the same water simultaneously. To

provide additional accuracy, criteria are developed for fresh water and

for salt water.

Limitations of the analyses which may make the criteria

underprotective include the fact that data for all species are not

available and therefore not considered; the analysis also applies to

criteria on an individual basis with no consideration of additive or

synergistic effects, and the analysis does not consider impacts on

wildlife, due principally to a lack of data. Chemical toxicity is often

related to certain receiving water characteristics (pH, hardness, etc.)

of a water body. Adoption of some criteria without consideration of

these parameters could result in the criteria being overprotective.

a. Freshwater Criteria

For this proposal, EPA updated freshwater aquatic life criteria

contained in CWA section 304(a) criteria guidance first published in

the early 1980's and later modified in the NTR, as amended, for the

following eleven pollutants: arsenic, cadmium, chromium (VI), copper,

mercury, dieldrin, endrin, lindane (gamma BHC), nickel,

pentachlorophenol, and zinc. These updates are explained in a technical

support document entitled, 1995 Updates: Water Quality Criteria

Documents for the Protection of Aquatic Life in Ambient Water, (U.S.

EPA-820-B-96-001, September 1996), available in the administrative

record to this rulemaking; this document presents the derivation of

each of the final CMCs and CCCs and the toxicity studies from which the

updated freshwater criteria for the eleven pollutants were derived. The

presentation of polychlorinated biphenyls (PCB) criteria in the

criteria matrix for this proposal differs from that in the NTR, as

amended; for this proposal, the criteria are expressed as a total of

all aroclors, while for the NTR, as amended, the criteria are expressed

for each aroclor. The mercury criteria also differ in this proposal due

to the Agency's movement away from aquatic life criteria based on the

Final Residue Value (FRV) procedure of the 1985 Guidance. Differences

between the eleven CMCs and CCCs as contained in CWA section 304(a)

criteria guidance documents and the CMCs and CCCs in this proposed rule

can be attributed to one or more of the following reasons.

First, EPA derived and published CWA section 304(a) criteria

guidance documents between 1980 and 1987. Some of the aquatic life

criteria in this proposed rule were calculated using data published

subsequent to the issuance of individual 304(a) criteria guidance

documents or using other new information. The pollutants for which this

applies are: arsenic, cadmium, chromium (VI), copper, mercury,

dieldrin, endrin, lindane, nickel, pentachlorophenol, and zinc. The use

of an updated database resulted in less restrictive acute and/or

chronic criteria for cadmium and zinc as compared to the published

criteria guidance documents. EPA believes that the differences between

the proposed updated criteria and the national published criteria

guidance documents are insignificant. However, EPA believes that it is

appropriate to propose criteria in this rule based on the most recent

data. The following table shows the differences between the proposed

criteria for this rule and the 304(a) criteria guidance which were

promulgated in the NTR, as amended. All values are in micrograms per

liter or g/l:

----------------------------------------------------------------------------------------------------------------

Proposed freshwater NTR freshwater

Compound -------------------------------------------------------

CMC CCC CMC CCC

----------------------------------------------------------------------------------------------------------------

Arsenic................................................. 1,2 340 1,2 150 1,3 360 1,3 190

[[Page 42169]]

Cadmium................................................. 1,2,4 4.3 1,2,4 2.2 1,5 3.7 1,5 1.0

Chromium (VI)........................................... 1,2 16 1,2 11 1,3 15 1,3 10

Copper.................................................. 1,2,4 13 1,2,4 9.0 1,5 17 1,5 11

Nickel.................................................. 1,2,4 470 1,2,4 52 1,5 1400 1,5 160

Zinc.................................................... 1,2,4 120 1,2,4 120 1,5 110 1,5 100

Pentachloro-phenol...................................... 2,6 19 2,6 15 6 20 6 13

Lindane (gamma-BHC)..................................... 2 0.95 ............ 7 2 0.08

Dieldrin................................................ 2 0.24 2 0.056 7 2.5 0.0019

Endrin.................................................. 2 0.086 2 0.036 7 0.18 0.0023

Mercury................................................. 1,2,3 1.4 1,2,3 0.77 1,3 2.1 0.012

PCBs.................................................... ............ 8,9 0.014 ............ 8,10 0.014

Mercury................................................. 1,3 1.8 1,3 0.94 1,3 1.8 0.025

PCBs.................................................... ............ 8,9 0.03 ............ 8,10 0.03

----------------------------------------------------------------------------------------------------------------

\1\ These freshwater and saltwater criteria for metals are expressed in terms of the dissolved fraction of the

metal in the water column, not the total recoverable fraction. Criterion values were calculated by using EPA's

CWA 304(a) criteria guidance values (described in the total recoverable fraction) and then applying conversion

factors as in the NTR, as amended, (60 FR 22228, May 4, 1995 and 40 CFR part 131).

\2\ This criterion has been recalculated pursuant to 1995 Updates: Water Quality Criteria Documents for the

Protection of Aquatic Life in Ambient Water (EPA-820-B-96-001, September 1996). See also the Great Lakes Water

Quality Initiative (40 CFR Parts 9, 122, 123, 131, and 132; Final Water Quality Guidance for the Great Lakes

System, Final Rule; 60 FR 15366, March 23, 1995) and Great Lakes Water Quality Initiative Criteria Documents

for the Protection of Aquatic Life in Ambient Water (EPA-820-B-95-004, March 1995).

\3\ Criteria for these metals are expressed as a function of the water-effect ratio (WER) as defined in 40 CFR

131.36(c).

\4\ These freshwater aquatic life criteria for metals are expressed as a function of total hardness (mg/l as

CaCO3 ) in the water body. The equations are provided in the proposed rule at 40 CFR 131.38(b)(2). Values

displayed above and in the proposed rule matrix correspond to a total hardness of 100 mg/l as CaCO3.

\5\ Freshwater aquatic life criteria for these metals are expressed as a function of total hardness (mg/l as

CaCO3), and as a function of the pollutant's water-effect ratio, WER, as defined in 40 CFR 131.36(c). The

equations are provided in the NTR, as amended, and values above and in the rule matrix correspond to a total

hardness of 100 mg/l as CaCO3 and a water-effect ratio of 1.0.

\6\ These freshwater aquatic life criteria for pentachlorophenol are expressed as a function of pH, and are

calculated as follows: (Values displayed above in the matrix correspond to a pH of 7.8.) CMC=exp(1.005 (pH)-

4.830). CCC=exp(1.005(pH)-5.290).

\7\ These aquatic life criteria for these pollutants were issued in 1980 utilizing the 1980 Guidelines for

criteria development. The acute values shown are final acute values (FAV) which by the 1980 Guidelines are

instantaneous values.

\8\ The CAS numbers for the PCB compounds are 53469219, 11097691, 11104282, 11141165, 12672296, 11096825, and

12674112, respectively.

\9\ This proposed criterion is the sum of all aroclors.

\10\ This criterion was listed for each aroclor in the matrix at 40 CFR 131.36(b)(1).

Secondly, some of the 304(a) criteria guidance documents were

derived using a methodology which preceded EPA's current methodology,

the 1985 Guidelines (pages 16 and 17).

In this proposed rule, where sufficient data existed to use the

1985 Guidelines, EPA recalculated the criteria. The chemicals for which

this applies are: dieldrin, endrin, and lindane (gamma BHC) (chronic

criterion only). The NTR, as amended, however, did not update the 1980

criteria using the 1985 Guidelines.

Third, EPA has deleted some of the data used in deriving three

criteria: specifically, the 1984 criterion for copper and the 1980

criteria for dieldrin and endrin, because under EPA's 1985 Guidelines,

the toxicity testing procedure was unacceptable.

Fourth, in several of the 304(a) criteria guidance documents, the

range of Species Mean Acute Values (SMAVs) or Species Mean Chronic

Values (SMCVs) was greater than a factor of five for some genera.

Because of this wide range, EPA set the Genus Mean Acute Values (GMAVs)

or Genus Mean Chronic Values (GMCVs) for those genera equal to the

lowest SMAV or SMCV for that genus in order to provide adequate

protection to all tested species in the genus. The pollutants for which

this applies are cadmium, copper and dieldrin.

In addition to the reasons cited earlier concerning differences

between NTR, as amended, criteria and proposed CMCs for this

rulemaking, several of the proposed CCCs are affected by a preference

of using freshwater Acute-Chronic Ratios (ACRs). In some of the 304(a)

criteria guidance documents, EPA had used saltwater ACRs in the

calculation of freshwater Final Chronic Values (FCVs) when available.

In updating criteria, EPA generally did not use saltwater ACRs when

there were a sufficient number of acceptable freshwater ACRs to

calculate a Final Acute-Chronic Ratio (FACR) because freshwater data is

preferable for freshwater criteria. When there was an insufficient

number of freshwater ACRs to calculate a FACR, EPA used saltwater ACRs

with any acceptable freshwater ACRs. The pollutants for which this

applies are: dieldrin, endrin and nickel. Removal of saltwater ACRs

from the data sets had a minor effect on the resultant criteria.

Today's rule utilizes the Final Residue Value (FRV) procedure of

the 1985 Guidelines for PCBs. The 1985 national methodology in the 1985

Guidelines indicates that the FRV is intended to prevent concentrations

of pollutants in commercial or recreational aquatic species from

affecting the marketability of those species or affecting wildlife that

consume aquatic life. While in today's rule the FRV is used to

calculate the chronic values for PCBs, EPA believes it may not be as

protective as criteria derived from the Final Chronic Value (FCV).

However, the use of the FRV in deriving the chronic values for PCBs

represents EPA's best available scientific approach. The NTR, as

amended, criteria for dieldrin, endrin, and mercury were based on FRVs

calculated from FDA action levels. EPA now believes that the human

health criteria proposed elsewhere in this notice will provide an

appropriate level of protection to humans consuming freshwater fish and

shellfish, but that use of the FDA action levels to protect aquatic

life (fish and propagation of fish) is inappropriate. In this rule, EPA

updated the chronic values for dieldrin, endrin and mercury based on

Final Chronic Values (FCVs) calculated by dividing a Final Acute Value

(FAV) by the Final Acute-Chronic Ratio (FACR).

The derivation of each of these criteria, and the toxicity studies

upon

[[Page 42170]]

which they are based, are discussed in a technical support document

entitled, 1995 Updates: Water Quality Criteria Documents for the

Protection of Aquatic Life in Ambient Water (EPA-820-B-96-001,

September 1996). This document is available in the administrative

record for this rulemaking.

b. Freshwater Acute Selenium Criterion

EPA is proposing a different freshwater acute aquatic life

criterion for selenium in this proposed rule than was promulgated in

the NTR, as amended. EPA's proposal here is consistent with EPA's

recent (proposed) selenium criterion maximum concentration for the

Water Quality Guidance for the Great Lakes System (61 FR 58444,

November 14, 1996). This proposal takes into account data showing that

selenium's two most prevalent oxidation states, selenite and selenate,

present differing potentials for aquatic toxicity, as well as new data

indicating that various forms of selenium are additive. Additivity

increases the toxicity of mixtures of different forms of the pollutant.

The new approach produces a different selenium acute criterion

concentration, or CMC, depending upon the relative proportions of

selenite, selenate, and other forms of selenium that are present. While

these revisions may produce either a less or a more stringent acute

criterion for selenium, depending on which form of the pollutant is

predominant in a water body, the proposed freshwater acute criterion

will protect aquatic life in fresh waters of the State of California.

Derivation of the Current Freshwater Criterion for Selenium: When

EPA published a recommended freshwater aquatic life criterion for

selenium in 1987, it considered both field data on chronic toxicity

from Belews Lake in North Carolina and laboratory data showing chronic

effects. A comparison of the data indicated that selenium was more

toxic to aquatic life in the field than in standard laboratory toxicity

tests. Consequently, to ensure that the criterion would protect aquatic

life, EPA derived a chronic criterion, or a CCC, of 5 g/l for

total recoverable selenium from the field data. Because the Belews Lake

study did not distinguish between selenite, selenate, and any other

form of selenium, and because some forms of selenium can convert to

other forms over time (U.S. EPA, 1987), EPA established a single CCC

for selenium rather than a separate CCC for selenite and/or selenate.

EPA reasoned that acute effects would also be more severe in the

field than in the laboratory. EPA, however, was not able to find any

field studies assessing acute effects. Consequently, EPA back-

calculated the CMC from the field-derived CCC for total selenium,

arriving at a value of 19.98 g/l, which it rounded to 20

g/l. When EPA proposed and promulgated selenium criteria for

the NTR, as amended, it used the same field-data approach and

calculated a CMC of 20 g/l and a CCC of 5 g/l for all

forms of selenium.

EPA noted that, had it concluded that laboratory data could serve

as a basis for the selenium criteria, there were sufficient laboratory

studies on acute effects to establish separate CMCs for both selenate

and selenite. EPA calculated that a CMC for selenite (selenium IV)

based on laboratory data might have been 185.9 g/l, while a

CMC for selenate (selenium VI) might have been 12.82 g/l. As

explained above, however, EPA chose to base the CMC on field data that

did not differentiate between selenite and selenate.

EPA is proposing a different approach to that used in the NTR,

amended, for the fresh waters of California covered by this proposed

rule. EPA is proposing a new CMC for total selenium based on more

recent studies which indicate that the toxicities of various forms of

selenium are additive. EPA is proposing an equation that will allow

calculation of a CMC for selenium based on the relative proportions of

selenite, selenate and other selenium forms present in a specific water

body. The toxicities for selenite and selenate used in this equation

are based on the laboratory studies cited in the 1987 and 1995 selenium

criteria documents, and are identical to the values calculated in those

documents.

EPA continues to believe that the field data support a CCC of 5

g/l for selenium. The chronic criterion addresses longer-term

exposures to selenium under field conditions, including exposure

through the food chain. EPA has no field data that can support

different chronic criteria for different forms of selenium.

Furthermore, EPA believes that current studies show that the various

forms of selenium ``interconvert'' to other forms over these longer

time frames, so that the relative proportions of the different forms

change during the exposure period. A form that exhibits low toxicity at

one point during the exposure period may convert to a different, more

toxic form at a different point.

Selenium Chemistry: Selenium takes several forms in ambient waters

which can significantly alter its toxicity to aquatic life, as shown

below. Inorganic selenium has two oxidation states (i.e., selenium IV,

or selenite, and selenium VI, or selenate), which can exist

simultaneously in aerobic surface water at pH 6.5 to 9.0. Chemical

conversion from one oxidation state to another often proceeds at such a

slow rate in aerobic surface water that thermodynamic considerations do

not determine the relative concentrations of the oxidation states.

Although selenate (selenium VI) is thermodynamically favored in

oxygenated alkaline water, substantial concentrations of both

organoselenium (selenium minus II) and selenite (selenium IV) are not

uncommon (Burton et al. 1980; Cutter and Bruland 1984; Measures and

Burton 1978; North Carolina Department of Natural Resources and

Community Development 1986; Robberecht and Van Gricken 1982; Takayanagi

and Cossa 1985; Takayanagi and Wong 1984a,b: Uchida et al. 1980).

Various forms of organic selenium also occur in water (Besser et

al. 1994; Cutter 1991). Toxicity data for some organic selenium forms

are available and are compared below to toxicity data for selenite and

selenate:

[[Page 42171]]

------------------------------------------------------------------------

Daphnia

Compound Zebrafish C. riparius b, c, magnae

a (mg/l) d (mg/l) e (mg/

--------------------------------------------------------------------l)--

Selenate........................ 18. 16.2 10.5 2.84

Seleno-DL-cystine............... 12 ................. 2.01

Selenite........................ 1. 7.95 14.6 0.55

Seleno-DL-methionine............ 0.1 ................. 0.31

Seleno-L-methionine............. .......... 5.78 6.88 .......

------------------------------------------------------------------------

a 10-day LC50 (Niimi and LaHam 1976). d 48-hr LC50 (Maier et

al. 1993).

b 48-hr LC50 (Ingersoll et al. 1990). e 48-hr LC50

(Maier et al. 1993).

c River Water.

Cutter (1991) described methods for measuring total recoverable and

dissolved selenate, selenite, organoselenium, and selenium in water,

and other information concerning the measurement of selenium in water

has been published by Besser et al. (1994), McKeown and Marinas (1986),

Pitts et al. (1994), and Takayanagi and Cosa (1985).

EPA believes that recent studies demonstrate the acute toxicities

of selenate, selenite, and one form of organoselenium are additive;

that is, these forms are more toxic together then they are separately

(Hamilton and Buhl 1990; Maier et al. 1993). The studies demonstrated

additivity by comparing the toxicities of mixtures to the toxicities of

the separate toxicants. Thus, EPA believes that it would be appropriate

to establish separate CMCs for selenate and selenite only in situations

in which either selenate or selenite is the only form of selenium in

the water column. When more than one form occurs in the water,

additivity should be taken into account so that the CMC for selenium is

a function of the toxicities and concentrations of the forms. EPA is

proposing an equation that can be used to derive an appropriate

criterion for total selenium based on the relative concentrations of

selenite, selenate, and all other forms of selenium found in a

particular water body.

Toxicity of Three Categories of Selenium: Selenium (IV). EPA is

proposing to rely on the laboratory data contained in the 1987 and 1995

criteria documents to establish an acute toxicity of 185.9 g/l

for selenite.

Selenium (VI). EPA is proposing to rely on the laboratory data

contained in the 1987 and 1995 criteria documents to establish an acute

toxicity of 12.83 g/l for selenate.

Other Forms of Selenium. EPA has not found and believes that

sufficient toxicity data do not exist to allow derivation of CMCs for

other selenium compounds. Nevertheless, as indicated in the previous

table, the acute toxicity of such other forms of selenium appears to be

significant with toxicity increasing by as much as 180 times depending

on the form of selenium and the test organism. Toxicity tests conducted

on the other forms of selenium indicate that they can be more toxic

than selenate and selenite. Consequently, in order not to ignore the

toxicity of these other forms of selenium, EPA is proposing to assume

that half of the measured or derived concentration of ``other''

selenium forms is as toxic as selenate and half is as toxic as

selenite. EPA believes this default assumption is more reasonable than

assuming either that the entire quantity of ``other'' forms is as toxic

as either selenate or selenite, or that it is not toxic. Such

assumptions would be more likely to over-predict or under-predict the

toxicity of this ``other forms'' category. EPA is also reluctant to

compute any type of ``average'' from the toxicity data on ``other

forms'' presented in the table above. These data are quite sparse.

Moreover, they reflect only organic selenium forms, and the toxicities

of other inorganic forms and compounds may be quite different.

Equation: Additive toxicity means that the concentrations of the

different forms should be added together after adjusting for the

relative toxicity of each. For a single toxicant the goal is for the

concentration, c, to be less than or equal to the criterion, CMC; that

is, the ratio c/CMC 1. For additive toxicants the goal is

for the sum of such ratios to be less than or equal to 1. Thus, for two

forms of selenium with additive acute toxicities, the concentration of

each form should be controlled such that:

[GRAPHIC] [TIFF OMITTED] TP05AU97.000

where c1 is the concentration of selenite and other

selenium assumed to have the toxicity of selenite, c2 is the

concentration and selenate and other selenium assumed to have the

toxicity of selenate; and CMC1 and CMC2 are the

CMCs for selenite and selenate respectively. A Criterion Maximum

Concentration, CMCSe, for the combined additive forms of

selenium can then be calculated from the following equation, which is

derived from the previous one:

[GRAPHIC] [TIFF OMITTED] TP05AU97.001

where f1 and f2 are the fractions of total

selenium that are treated as selenite and selenate respectively (that

is, f1=c1/cSe and

cSe=c1+c2), and

f1+f2=1.

The above equations, when coupled with the assumption that half of

the other selenium (including organoselenium) has the toxicity of

selenite and half has the toxicity of selenate, behave as follows. If

the concentrations of selenite and other selenium are zero

(c1=0) then the Criterion Maximum Concentration

(CMCSe) would be calculated to be 12.82 g/l, the

CMC of selenate. On the other hand, if the concentrations of selenate

and other selenium are zero, then CMCSe would be calculated

to be 185.9 g/l, the CMC of selenite. In determining

compliance with this criterion, EPA expects that monitoring to

determine speciation will be necessary.

EPA is requesting comment on the data and approach for deriving the

proposed CMC for selenium applicable to California in this rulemaking.

Specifically, EPA is requesting comment on the scientific basis for

establishing the additivity of the toxicities of the various forms of

selenium (selenate, selenite, and other selenium compounds). EPA also

requests comments on the procedure used to account for the additivity

of the various forms of selenium in the criterion derivation algorithm.

If persons have filed comments on the November 1996 notice, cited

above, that they wish to submit for this rulemaking, they should submit

them as described above.

c. Dissolved Metals Criteria

In December of 1992, in the NTR, EPA promulgated water quality

criteria for several states that had failed to meet the requirements of

CWA section 303(c)(2)(B). Included among the water quality criteria

promulgated were numeric criteria for the protection of aquatic life

for 11 metals: arsenic,

[[Page 42172]]

cadmium, chromium (III), chromium (VI), copper, lead, mercury, nickel,

selenium, silver and zinc. Criteria for two metals applied to the State

of California: chromium III and selenium.

The Agency received extensive public comment during the development

of the NTR regarding the most appropriate approach for expressing the

metals criteria. The principal issue was the correlation between metals

that are measured and metals that are bioavailable and toxic to aquatic

life.

At the time of the NTR promulgation, Agency policy was to express

metals criteria, as recommended in the section 304(a) criteria guidance

documents, as total recoverable metal measurements. Agency guidance

prior to the NTR promulgation indicated that metals criteria may be

expressed either as total recoverable metal or dissolved metal. See

Interim Guidance on Interpretation and Implementation of Aquatic Life

Criteria for Metals, U.S. EPA, May 1992 (notice of availability

published at 57 FR 4041, June 5, 1992). Since the NTR covered a

substantial number of water bodies of varying water quality, EPA

selected what it considered a simple, conservative approach to

implement the metals criteria, namely, the total recoverable method.

EPA continued to work with the states and other interested parties

on the issue of metals bioavailability and toxicity. EPA held a

workshop of invited experts on the issue and as a result of the

consultations, the Agency issued a policy memorandum on October 1,

1993, entitled, Office of Water Policy and Technical Guidance on

Interpretation and Implementation of Aquatic Life Metals Criteria (the

Metals Policy). The Metals Policy states:

It is now the policy of the Office of Water that the use of

dissolved metal to set and measure compliance with water quality

standards is the recommended approach, because dissolved metal more

closely approximates the bioavailable fraction of the metal in the

water column than does total recoverable metal.

It further states:

Until the scientific uncertainties are better resolved, a range

of different risk management decisions can be justified. EPA

recommends that State water quality standards be based on dissolved

metal. EPA will also approve a State risk management decision to

adopt standards based on total recoverable metal, if those standards

are otherwise approvable as a matter of law.

The adoption of the Metals Policy did not change EPA's position

that the existing total recoverable criteria published under section

304(a) of the CWA were scientifically defensible. EPA believed, and

continues to believe, that when a state develops and adopts its

standards, the state, in making its risk management decision, may want

to consider sediment, food chain effects, and other fate-related issues

and decide to adopt total recoverable or dissolved metals criteria.

In 1993, a number of parties brought lawsuits challenging the NTR

metals criteria. See American Forest and Paper Ass'n, Inc. et al. v.

U.S. EPA (Consolidated Case No. 93-0694 (RMU), D.D.C.). The plaintiffs

in those lawsuits wanted the permitting authorities in the NTR states

to use criteria based on dissolved metal rather than total recoverable

metal. After careful consideration, EPA concluded that it was in the

public interest to revise the metals criteria promulgated in the NTR to

reflect the Office of Water's new metals policy. On February 15, 1995,

EPA and the plaintiffs filed a partial settlement agreement with the

Court. Pursuant to the terms of the agreement, EPA agreed to issue an

administrative stay of the numeric aquatic life water quality criteria

(expressed as total recoverable metal) for: arsenic; cadmium, chromium

(III); chromium (VI); copper; lead, mercury (acute only), nickel,

selenium (saltwater only), silver, and zinc. The stay was effective

April 14, 1995 (60 FR 22228, May 4, 1995), and was only intended to be

in effect until EPA took action to amend the NTR by promulgating new

metals criteria based on dissolved metal. EPA published an interim

final amendment to the NTR effective April 15, 1995; this amendment

promulgated new metals criteria for the metals listed in the stay (60

FR 22229, May 4, 1995).

The numeric criteria in the NTR, as amended, reflect the Office of

Water's current policy with respect to metals. The 1995 NTR amendment

promulgated dissolved metals criteria as substitutes for the total

recoverable metals criteria subject to the EPA's administrative stay.

The NTR promulgated freshwater chromium (III) criteria and freshwater

selenium criteria for the State of California. However, since the

amendments did not change the freshwater selenium criteria, only

California's chromium (III) criteria were changed to the dissolved form

through the NTR, as amended.

Since EPA's previous criteria guidance had been expressed as total

recoverable metal, to express the criteria as dissolved, conversion

factors were developed to account for the possible presence of

particulate metal in the laboratory toxicity tests used to develop the

total recoverable criteria. Initially, EPA included a set of

recommended freshwater conversion factors with the Metals Policy. Based

on additional laboratory evaluations that simulated the original

toxicity tests, EPA refined the procedures used to develop freshwater

conversion factors for aquatic life criteria. These new conversion

factors were made available for public review and comment in the

amendments to the NTR on May 4, 1995, at 60 FR 22229.

EPA also conducted saltwater laboratory simulation tests for the

development of conversion factors for saltwater metals criteria. The

saltwater tests results were first available in the amendments to the

NTR on May 4, 1995. The conversion factors in this proposed rule and

other technical reports are the same as those referenced in the May 4,

1995 amendments to the NTR and supersede the conversion factors in

Attachment 2 of the Metals Policy.

Freshwater Criteria Conversion Factors: The freshwater conversion

factors contained in today's proposed rule are contained in the

Derivation of Conversion Factors for the Calculation of Dissolved

Freshwater Aquatic Life Criteria for Metals, U.S. EPA, 1995, available

in the administrative record for this rulemaking. This study did not

include laboratory simulation tests for mercury or silver; therefore,

the freshwater conversion factors for mercury and silver used today are

from the Metals Policy, also in the record for this rule. These

conversion factors are presented in 40 CFR 131.38(b)(2) of today's

proposed rule.

The conversion factors for most freshwater metals were established

as constant values. For cadmium and lead however, EPA found that water

hardness mediated the conversion factor and should be taken into

account when converting total recoverable cadmium and lead criteria to

dissolved. 40 CFR 131.38(b)(2) of today's proposed rule presents the

hardness-dependent conversion factors for cadmium and lead.

Saltwater Criteria Conversion Factors: Acute saltwater conversion

factors were first promulgated in the amendments to the NTR, and are

again being proposed in this rule. The data and the acute criteria

conversion factors for salt water are contained in the Derivation of

Conversion Factors for the Calculation of Dissolved Saltwater Aquatic

Life Criteria for Metals, U.S. EPA, 1995. This summary report and its

supporting data are available in the administrative record. Saltwater

chronic conversion factors have not been developed separately and

therefore are not available in today's proposed rule. Based on close

similarities between the

[[Page 42173]]

freshwater acute and chronic conversion factors, EPA believes that, if

calculated, the chronic saltwater conversion factors would be nearly

the same as the acute saltwater factors. In the absence of these

chronic conversion factors, the saltwater acute conversion factors

would apply. Salt water simulation tests were not completed for mercury

or silver, therefore, the conversion factors from the Metals Policy

continue to apply. The saltwater conversion factors are presented in 40

CFR 131.38(b)(2) of today's proposed rule.

Calculation of Dissolved Metals Criteria: Metals criteria values in

today's proposed rule in the matrix at 131.38(b)(1) are shown as

dissolved metal. These criteria have been calculated in one of two

ways. For freshwater metals criteria that are hardness-dependent, the

dissolved metal criteria value is calculated separately for each

hardness using the table at proposed 40 CFR 131.38(b)(2). The hardness-

dependent freshwater values presented in the matrix at proposed 40 CFR

131.38(b)(1) have been calculated using a hardness of 100 mg/l as

CaCO3 for illustrative purposes only. Saltwater and

freshwater metals criteria that are not hardness-dependent are

calculated by taking the total recoverable criteria values (from EPA's

national section 304(a) criteria guidance documents, as updated as

described in section a. above) before rounding, and multiplying them by

the appropriate conversion factors. The final dissolved metals criteria

values, as they appear in the matrix at proposed 40 CFR 131.38(b)(1),

are rounded to two significant figures.

Translators for Dissolved to Total Recoverable Metals Limits: EPA's

National Pollutant Discharge Elimination System (NPDES) regulations

require that limits for metals in permits be stated as total

recoverable in most cases (see 40 CFR 122.45(c)) except when an

effluent guideline specifies the limitation in another form of the

metal, the approved analytical methods measure only dissolved metal, or

the permit writer expresses a metal's limit in another form (e.g.,

dissolved, specific valence, or total) when required to carry out

provisions of the CWA. This is because the chemical conditions in

ambient waters frequently differ substantially from those in the

effluent and there is no assurance that effluent particulate metals

would not dissolve after discharge. The NPDES permit regulations do not

require that water quality standards be expressed as total recoverable;

rather, the regulations require permit writers to develop permit limits

that are expressed in terms of metals concentrations and loadings that

are measured using the total recoverable method. Expressing criteria as

dissolved metal requires translation between different metal forms in

the calculation of the permit limit so that a total recoverable permit

limit can be established that will achieve water quality standards.

Thus, it is important that permitting authorities and other authorities

have the ability to translate between dissolved metal in ambient waters

and total recoverable metal in effluent.

EPA has completed guidance on the use of translators to convert

from dissolved metals criteria to total recoverable permit limits. The

document, The Metals Translator: Guidance for Calculating a Total

Recoverable Permit Limit From a Dissolved Criterion (EPA 823-B-96-007,

June 1996), is included in the administrative record for today's

proposed rule. This technical guidance examines how to develop a metals

translator which is defined as the fraction of total recoverable metal

in the downstream water that is dissolved, i.e., the dissolved metal

concentration divided by the total recoverable metal concentration. A

translator may take one of three forms: (1) It may be assumed to be

equivalent to the criteria guidance conversion factors; (2) it may be

developed directly as the ratio of dissolved to total recoverable

metal; and (3) it may be developed through the use of a partition

coefficient that is functionally related to the number of metal binding

sites on the adsorbent in the water column (e.g., concentrations of

total suspended solids or TSS). This guidance document discusses these

three forms of translators, as well as field study designs, data

generation and analysis, and site-specific study plans to generate

site-specific translators.

California Regional Water Quality Control Boards may use any of

these methods in developing water quality-based permit limits to meet

dissolved metals criteria. EPA encourages the State to adopt a

statewide policy on the use of translators so that the most appropriate

method or methods are used consistently within California.

d. Application of Metals Criteria

In selecting an approach for implementing the metals criteria, the

principal issue is the correlation between metals that are measured and

metals that are biologically available and toxic. In order to assure

that the metals criteria are appropriate for the chemical conditions

under which they are applied, EPA is providing for the adjustment of

the criteria through application of the ``water-effect ratio''

procedure. EPA notes that performing the testing to use a site-specific

water-effect ratio is optional on the part of the State.

In the NTR, as amended, EPA identified the water-effect ratio (WER)

procedure as a method for optional site-specific criteria development

for certain metals. The WER approach compares bioavailability and

toxicity of a specific pollutant in receiving waters and in laboratory

waters. A WER is an appropriate measure of the toxicity of a material

obtained in a site water divided by the same measure of the toxicity of

the same material obtained simultaneously in a laboratory dilution

water.

On February 22, 1994, EPA issued Interim Guidance on the

Determination and Use of the Water-Effect Ratios for Metals (EPA 823-B-

94-001) now incorporated into the updated Second Edition of the Water

Quality Standards Handbook, Appendix L. In accordance with the WER

guidance and where application of the WER is deemed appropriate, EPA

strongly encourages the application of the WER on a watershed or water

body basis in California as opposed to application on a discharger-by-

discharger basis. This approach is technically sound, an efficient use

of resources, and allowable for NPDES permitting authorities.

The rule proposes that a default WER value of 1.0 will be assumed,

if no site-specific WER will be determined. To use a WER other than the

default of 1.0, the rule proposes that the WER must be determined as

set forth in EPA's WER guidance or determined by another scientifically

defensible method that has been adopted by the State as part of its

water quality standards program and approved by EPA.

The WER is a more comprehensive mechanism for addressing

bioavailability issues than simply expressing the criteria in terms of

dissolved metal. Consequently, expressing the criteria in terms of

dissolved metal, as done in today's proposed rule for California, does

not completely eliminate the utility of the WER. This is particularly

true for copper, a metal that forms reduced-toxicity complexes with

dissolved organic matter.

The Interim Guidance on Determination and Use of Water-Effect

Ratios for Metals explains the relationship between WERs for dissolved

criteria and WERs for total recoverable criteria. Dissolved

measurements are to be used in the site-specific toxicity testing

underlying the WERs for dissolved criteria. Because

[[Page 42174]]

WERs for dissolved criteria generally are little affected by elevated

particulate concentrations, EPA expects those WERs to be somewhat less

than WERs for total recoverable criteria in such situations.

Nevertheless, after the site-specific ratio of dissolved to total metal

has been taken into account, EPA expects a permit limit derived using a

WER for a dissolved criterion to be similar to the permit limit that

would be derived from the WER for the corresponding total recoverable

criterion.

e. Saltwater Copper Criteria

The saltwater copper criteria for aquatic life in today's proposed

rule are 4.8 g/l (CMC) and 3.1 g/l (CCC) in the

dissolved form. New data including data collected from studies for the

New York/New Jersey Harbor and the San Francisco Bay indicated a need

to revise the copper criteria document to reflect a change in the

saltwater CMC and CCC aquatic life values. EPA conducted a

comprehensive literature search and added toxicity test data for seven

new species to the database for the saltwater copper criteria. EPA

believes these new data have national implications and the national

criteria guidance now contain a CMC of 4.8 g/l dissolved and a

CCC of 3.1 g/l dissolved. In the amendments to the NTR, EPA

noticed the availability of data to support these changes to the NTR,

and solicited comments. The data can be found in the draft document

entitled, Ambient Water Quality Criteria--Copper, Addendum 1995. This

document is available from the Office of Water Resource Center and is

available for review in the administrative record for this proposed

rule. EPA is now requesting comments on these revised criteria as

applied to the State of California. Commenters who wish to refer to

their comments on the Notice of Availability must resubmit a copy of

their previous comments.

f. Chronic Averaging Period

In establishing water quality criteria, EPA generally recommends an

``averaging period'' which reflects the duration of exposure required

to elicit effects in individual organisms (TSD, Appendix D-2.) The CCC

is intended to be the highest concentration that could be maintained

indefinitely in a water body without causing an unacceptable effect on

the aquatic community or its uses. (TSD, Appendix D-1). As aquatic

organisms do not generally experience steady exposure, but rather

fluctuating exposures to pollutants, and because aquatic organisms can

generally tolerate higher concentrations of pollutants over a shorter

periods of time, EPA expects that the concentration of a pollutant can

exceed the CCC without causing an unacceptable effect if (a) the

magnitude and duration of exceedences are appropriately limited and (b)

there are compensating periods of time during which the concentration

is below the CCC. This is done by specifying a duration of an

``averaging period'' over which the average concentration should not

exceed the CCC more often than specified by the frequency (TSD,

Appendix D-1).

EPA is proposing a 4-day averaging period for chronic criteria,

which means that measured or predicted ambient pollutant concentrations

should be averaged over a 4-day period to determine attainment of

chronic criteria. EPA acknowledges that the State may develop and adopt

an averaging period that differs from EPA's recommendation, so long as

it is scientifically supportable.

The most important consideration for setting an appropriate

averaging period is the length of time that sensitive organisms can

tolerate exposure to a pollutant at levels exceeding a criterion

without showing adverse effects on survival, growth, or reproduction.

EPA believes that the chronic averaging period must be shorter than the

duration of the chronic tests on which the CCC is based, since, in some

cases, effects are elicited before exposure of the entire duration.

Most of the toxicity tests used to establish the chronic criteria are

conducted using steady exposure to toxicants for a least 28 days. (TSD,

page 35). Some chronic tests, however, are much shorter than this (TSD,

Appendix D-2). EPA selected the 4-day averaging period based on the

shortest duration in which chronic test effects are sometimes observed

for certain species and toxicants. In addition, EPA believes that the

results of some chronic tests are due to an acute effect on a sensitive

life stage that occurs some time during the test, rather than being

caused by long-term stress or long-term accumulation of the test

material in the organisms.

Additional discussion of the rationale for the 4-day averaging

period is contained in Appendix D of the TSD. Balancing all of the

above factors and data, EPA believes that the 4-day averaging period

falls within the scientifically reasonable range of values for choice

of the averaging period, and is an appropriate length of time of

pollutant exposure to ensure protection of sensitive organisms.

EPA established a 4-day averaging period in the NTR. In settlement

of litigation on the NTR, EPA stated that it was ``in the midst of

conducting, sponsoring, or planning research related to the basis for

and application of'' water quality criteria and mentioned the issue of

averaging period. See Partial Settlement Agreement in American Forest

and Paper Ass'n, Inc. et al. v. U.S. EPA (Consolidated Case No. 93-0694

(RMU), D.D.C.). EPA is re-evaluating issues raised about averaging

periods and will, if appropriate, revise the 1985 Guidelines.

EPA received public comment relevant to the averaging period during

the comment period for the 1995 Amendments to the NTR (40 CFR 22228,

May 4, 1995), although these public comments did not address the

chronic averaging period separately from the allowable excursion

frequency and the design flow. These commenters argued that a once-in-

3-year excursion frequency for 4-day average concentrations, or a 7Q10

design flow, was unnecessarily restrictive. For chronic criteria, they

noted that EPA has approved the use of a 30Q3 design flow in Colorado,

a 30Q5 design flow in Maryland, and a 1 percent exceedance frequency in

Pennsylvania. Comments recommended that EPA use the 30Q5 design flow

for chronic criteria.

While EPA is undertaking analysis of the chronic design conditions

as part of the revisions to the 1985 Guidelines, EPA has not yet

completed this work. Until this work is complete, for the reasons set

forth in the TSD, EPA continues to believe that the 4-day chronic

averaging period represents a reasonable, defensible value for this

parameter.

g. Hardness

Freshwater aquatic life criteria for certain metals are expressed

as a function of hardness because hardness and/or water quality

characteristics that are usually correlated with hardness can reduce or

increase the toxicities of some metals. Hardness is used as a surrogate

for a number of water quality characteristics which affect the toxicity

of metals in a variety of ways. Increasing hardness has the effect of

decreasing the toxicity of metals. Water quality criteria to protect

aquatic life may be calculated at different concentrations of

hardnesses measured in mg/l as CaCO3.

Section 131.38(b)(2) of the proposed rule presents the hardness-

dependent equations for freshwater metals criteria. For example, using

the equation for zinc, the total recoverable CMCs at a hardness of 10,

50, 100 or 200 mg/l as CaCO3 are 17, 67, 120 and 220

g/l, respectively. Thus, the specific value in the table in

the proposed regulatory text is for illustrative purposes only. Most of

the data used to develop these hardness equations for deriving aquatic

life

[[Page 42175]]

criteria for metals were in the range of 25 mg/l to 400 mg/l as

CaCO3, and the formulas are therefore most accurate in this

range. The majority of surface waters nationwide and in California have

a hardness of less than 400 mg/l as CaCO3.

In the past, EPA generally recommended that 25 mg/l as

CaCO3 be used as a default hardness value in deriving

freshwater aquatic life criteria for metals when the ambient (or

actual) hardness value is below 25 mg/l as CaCO3. However,

use of the approach results in criteria that may not be fully

protective. Therefore, for waters with a hardness of less than 25 mg/l

as CaCO3, criteria should be calculated using the actual

ambient hardness of the surface water.

In the past, EPA generally recommended that if the hardness was

over 400 mg/l, two options were available: (1) Calculate the criterion

using a default WER of 1.0 and using a hardness of 400 mg/l in the

hardness equation; or (2) calculate the criterion using a WER and the

actual ambient hardness of the surface water in the equation. Use of

the second option is expected to result in the level of protection

intended in the 1985 Guidelines whereas use of the first option is

thought to result in a lower aquatic life criterion. At high hardness

there is an indication that hardness and related inorganic water

quality characteristics do not have as much of an effect on toxicity of

metals as they do at lower hardnesses. Related water quality

characteristics do not correlate as well at higher hardnesses as they

do at lower hardnesses. Therefore, if hardness is over 400 mg/l as

CaCO3, a hardness of 400 mg/l as CaCO3 should be

used with a default WER of 1.0; alternatively, the WER and actual

hardness of the surface water may be used.

EPA requested comments in the NTR amendments on the use of actual

ambient hardness for calculating criteria when the hardness is below 25

mg/l as CaCO3, and when hardness is greater than 400 mg/l as

CaCO3. Most of the comments received were in favor of using

the actual hardness with the use of the water-effect ratio (1.0 unless

otherwise specified by the permitting authority) when the hardness is

greater than 400 mg/l as CaCO3. A few commenters did not

want the water-effect ratio to be mandatory in calculating hardness,

and other commenters had concerns about being responsible for deriving

an appropriate water-effect ratio. Overall, the commenters were in

favor of using the actual hardness when calculating hardness-dependent

freshwater metals criteria for hardness between 0-400 mg/l as

CaCO3. EPA took those comments into account in proposing

today's proposed rule.

A hardness equation is most accurate when the relationships between

hardness and the other important inorganic constituents, notably

alkalinity and pH, are nearly identical in all of the dilution waters

used in the toxicity tests and in the surface waters to which the

equation is to be applied. If an effluent raises hardness but not

alkalinity and/or pH, using the hardness of the downstream water might

provide a lower level of protection than intended by the 1985

guidelines. If it appears that an effluent causes hardness to be

inconsistent with alkalinity and/or pH, the intended level of

protection will usually be maintained or exceeded if either (1) data

are available to demonstrate that alkalinity and/or pH do not affect

the toxicity of the metal, or (2) the hardness used in the hardness

equation is the hardness of upstream water that does not contain the

effluent. The level of protection intended by the 1985 guidelines can

also be provided by using the WER procedure.

In some cases, capping hardness at 400 mg/l might result in a level

of protection that is higher than that intended by the 1985 guidelines,

but any such increase in the level of protection can be overcome by use

of the WER procedure.

For metals whose criteria are expressed as hardness equations, use

of the WER procedure will generally be intended to account for effects

of such water quality characteristics as total organic carbon on the

toxicities of metals. The WER procedure is equally useful for

accounting for any deviation from a hardness equation in a site water.

3. Human Health Criteria

EPA's CWA section 304(a) human health criteria guidance provides

criteria recommendations to minimize adverse human effects due to

substances in ambient water. EPA's CWA section 304(a) criteria guidance

for human health are based on two types of biological endpoints: (1)

Carcinogenicity and (2) systemic toxicity (i.e., all other adverse

effects other than cancer). Thus, there are two procedures for

assessing these health effects: one for carcinogens and one for non-

carcinogens.

EPA's human health guidelines assume that carcinogenicity is a

``non-threshold phenomenon,'' that is, there are no ``safe'' or ``no-

effect levels'' because even extremely small doses are assumed to cause

a finite increase in the incidence of the effect (i.e., cancer).

Therefore, EPA's water quality criteria guidance for carcinogens are

presented as pollutant concentrations corresponding to increases in the

risk of developing cancer. See Human Health Guidelines at 45 FR 79347.

For pollutants that do not manifest any apparent carcinogenic

effect in animal studies (i.e., systemic toxicants), EPA assumes that

the pollutant has a threshold below which no effect will be observed.

This assumption is based on the premise that a physiological mechanism

exists within living organisms to avoid or overcome the adverse effect

of the pollutant below the threshold concentration.

The human health risks of a substance cannot be determined with any

degree of confidence unless dose-response relationships are quantified.

Therefore, a dose-response assessment is required before a criterion

can be calculated. The dose-response assessment determines the

quantitative relationships between the amount of exposure to a

substance and the onset of toxic injury or disease. Data for

determining dose-response relationships are typically derived from

animal studies, or less frequently, from epidemiological studies in

exposed populations.

The dose-response information needed for carcinogens is an estimate

of the carcinogenic potency of the compound. Carcinogenic potency is

defined here as a general term for a chemical's human cancer-causing

potential. This term is often used loosely to refer to the more

specific carcinogenic or cancer slope factor which is defined as an

estimate of carcinogenic potency derived from animal studies or

epidemiological data of human exposure. It is based on extrapolation

from test exposures of high doses over relatively short periods of time

to more realistic low doses over a lifetime exposure period by use of

linear extrapolation models. The cancer slope factor, q1*, is EPA's

estimate of carcinogenic potency and is intended to be a conservative

upper bound estimate (e.g. 95% upper bound confidence limit).

For non-carcinogens, EPA uses the reference dose (RfD) as the dose

response parameter in calculating the criteria. For non-carcinogens,

oral RfD assessments (hereinafter simply ``RfDs'') are developed based

on pollutant concentrations that cause threshold effects. The RfD is an

estimate (with uncertainty spanning perhaps an order of magnitude) of a

daily exposure to the human population (including sensitive subgroups)

that is likely to be without appreciable risk of deleterious effects

during a lifetime. See Human Health

[[Page 42176]]

Guidelines. The RfD was formerly referred to as an ``Acceptable Daily

Intake'' or ADI. The RfD is useful as a reference point for gauging the

potential effect of other doses. Doses that are less than the RfD are

not likely to be associated with any health risks, and are therefore

less likely to be of regulatory concern. As the frequency of exposures

exceeding the RfD increases and as the size of the excess increases,

the probability increases that adverse effect may be observed in a

human population. Nonetheless, a clear conclusion cannot be

categorically drawn that all doses below the RfD are ``acceptable'' and

that all doses in excess of the RfD are ``unacceptable.'' In

extrapolating non-carcinogen animal test data to humans to derive an

RfD, EPA divides a no-observed-effect dose observed in animal studies

by an ``uncertainty factor'' which is based on professional judgment of

toxicologists and typically ranges from 10 to 10,000.

For CWA section 304(a) human health criteria development, EPA

typically considers only exposures to a pollutant that occur through

the ingestion of water and contaminated fish and shellfish. Thus, the

criteria are based on an assessment of risks related to the surface

water exposure route only where designated uses are drinking water and

fish and shellfish consumption.

The assumed exposure pathways in calculating the criteria are the

consumption of 2 liters per day of water at the criteria concentration

and the consumption of 6.5 grams per day of fish and shellfish

contaminated at a level equal to the criteria concentration but

multiplied by a ``bioconcentration factor.'' The use of fish and

shellfish consumption as an exposure factor requires the quantification

of pollutant residues in the edible portions of the ingested species.

Bioconcentration factors (BCFs) are used to relate pollutant

residues in aquatic organisms to the pollutant concentration in ambient

waters. BCFs are quantified by various procedures depending on the

lipid solubility of the pollutant. For lipid soluble pollutants, the

average BCF is calculated from the weighted average percent lipids in

the edible portions of fish and shellfish, which is about 3%; or it is

calculated from theoretical considerations using the octanol/water

partition coefficient. For non-lipid soluble compounds, the BCF is

determined empirically. The assumed water consumption is taken from the

National Academy of Sciences publication Drinking Water and Health

(1977). (Referenced in the Human Health Guidelines.) This value is

appropriate as it includes a margin of safety so that the general

population is protected. See also EPA's discussion of the 2.0 liters/

day assumption at 61 FR 65183 (Dec. 11, 1996). The 6.5 grams per day

contaminated fish and shellfish consumption value was equivalent to the

average per-capita consumption rate of all (contaminated and non-

contaminated) freshwater and estuarine fish and shellfish for the U.S.

population. See Human Health Guidelines.

EPA assumes in calculating water quality criteria that the exposed

individual is an average adult with body weight of 70 kilograms. The

issue of concern is dose per kilogram of body weight. EPA assumes 6.5

grams per day of contaminated fish and shellfish consumption and 2.0

liters per day of contaminated drinking water consumption for a 70

kilogram person in calculating the criteria. Persons of smaller body

weight are expected to ingest less contaminated fish and shellfish and

water, so the dose per kilogram of body weight is generally expected to

be roughly comparable.

There may be subpopulations within a state, such as subsistence

anglers who as a result of greater exposure to a contaminant, are at

greater risk than the hypothetical 70 kilogram person eating 6.5 grams

per day of maximally contaminated fish and shellfish and drinking 2.0

liters per day of maximally contaminated drinking water. For example,

individuals that ingest ten times more of a carcinogenic pollutant than

is assumed in derivation of the criteria at a 10-6 risk

level will be protected to a 10-5 level, which EPA has

historically considered to be adequately protective. There may,

nevertheless, be circumstances where site-specific numeric criteria

that are more stringent than the statewide criteria are necessary to

adequately protect highly exposed subpopulations. Although EPA intends

to focus on promulgation of appropriate statewide criteria that will

reduce risks to all exposed individuals, including highly exposed

subpopulations, site-specific criteria may be developed subsequently by

the State where warranted to provide necessary additional protection.

See Human Health Guidelines, Issue 8.

EPA has a process to develop a scientific consensus on oral

reference dose assessments and carcinogenicity assessments (hereinafter

simply cancer slope factors or slope factors or q1*s). Through this

process, EPA develops a consensus of Agency opinion which is then used

throughout EPA in risk management decision-making. EPA maintains an

electronic data base which contains the official Agency consensus for

oral RfD assessments and carcinogenicity assessments which is known as

the Integrated Risk Information System (IRIS). It is available for use

by the public on the National Institutes of Health's National Library

of Medicine's TOXNET system, and through diskettes from the National

Technical Information Service (NTIS). (NTIS access number is PB 90-

591330.)

Section 304(a)(1) of the CWA requires EPA to periodically revise

its criteria guidance to reflect the latest scientific knowledge: ``(A)

on the kind and extent of all identifiable effects on health and

welfare * * * ; (B) on the concentration and dispersal of pollutants,

or their byproducts, through biological, physical, and chemical

processes; and (C) on the effects of pollutants on the biological

community diversity, productivity, and stability, including information

on the factors affecting eutrophication rates of organic and inorganic

sedimentation for varying types of receiving waters.'' In developing

up-to-date water quality criteria for the protection of human health,

EPA consistently relies upon the most recent IRIS values (RfDs and

q1*s) as the toxicological basis in the criterion calculation. IRIS

reflects EPA's most current consensus on the toxicological assessment

for a chemical. In developing the criteria in today's proposed rule,

the most recent IRIS values were used together with currently accepted

exposure parameters for bioconcentration, fish and shellfish and water

consumption, and body weight. The IRIS cover sheet for each pollutant

criteria included in today's proposed rule is contained in the

administrative record.

For the human health criteria included in today's proposed rule,

EPA used the Human Health Guidelines on which criteria recommendations

from the appropriate CWA section 304(a) criteria guidance document were

based. (These documents are also placed in the administrative record

for today's proposed rule.) Where EPA has changed any parameters in

IRIS used in criteria derivation since issuance of the criteria

guidance document, EPA recalculated the criteria recommendation with

the latest IRIS information. Thus, there are differences between the

original criteria guidance document recommendations, and those in this

proposed rule, but this proposed rule presents EPA's most current CWA

section 304(a) criteria recommendation. The basis (q1* or RfD/ADI) and

BCF for each pollutant criterion in today's proposed rule is contained

in the rule's Administrative Record Matrix which is included in the

administrative record for the proposed

[[Page 42177]]

rule. In addition, all recalculated human health numbers are denoted by

an ``a'' in the criteria matrix in 40 CFR 131.38(b)(1) of the proposed

rule. The pollutants for which a revised human health criterion has

been calculated since the December 1992 NTR include: mercury;

dichlorobromomethane; 1,2-dichloropropane; 1,2-trans-dichloroethylene;

2,4-dimethylphenol; acenaphthene; benzo(a)anthracene; benzo(a)pyrene;

benzo(b)flouranthene; benzo(k)flouranthene; 2-chloronaphthalene;

chrysene; dibenzo(a,h)anthracene; indeno(1,2,3-cd)pyrene; N-nitrosodi-

n-propylamine; alpha-endosulfan; beta-endosulfan; endosulfan sulfate;

2-chlorophenol; butylbenzyl phthalate; and polychlorinated biphenyls.

In November of 1991, the proposed NTR presented criteria for

several pollutants in parentheses. These were pollutants for which, in

1980, insufficient information existed to develop human health water

quality criteria, but for which, in 1991, sufficient information

existed. Since these criteria did not undergo the public review and

comment in a manner similar to the other water quality criteria

presented in the NTR (for which sufficient information was available in

1980 to develop a criterion, as presented in the 1980 criteria guidance

documents), they were not proposed for adoption into the water quality

criteria, but were presented to serve as notice for inclusion in future

state triennial reviews. Today's rule proposes criteria for these nine

pollutants: copper; 1, 2-dichloropropane; 1,2-trans-dichloroethylene;

2,4-dimethylphenol; acenaphthene; 2-chloronaphthalene; N-nitrosodi-n-

propylamine; 2-chlorophenol; butylbenzene phthalate. All the criteria

are based on IRIS values--either an RfD or q1*--which were listed on

IRIS as of November 1991, the date of the proposed NTR. These values

have not changed since the final NTR was published in December of 1992.

The rule's Administrative Record Matrix in the administrative record of

today's proposed rule contains the specific RfDs, q1*s, and BCFs used

in calculating these criteria.

Potential Changes to the Human Health Criteria Methodology: EPA

expects to propose in the near future several changes to the 1980

ambient water quality criteria derivation guidelines (the Human Health

Guidelines). The methodology revisions anticipated reflect significant

scientific advances that have occurred during the past several years in

such key areas as cancer and noncancer risk assessments, exposure

assessments and bioaccumulation. Some anticipated areas of major

change, which are being considered in this process include:

1. The new Proposed Guidelines on Carcinogen Risk Assessment

emphasize the consideration of mode of action and route of exposure. A

weight of evidence narrative will be used instead of the traditional

alphanumeric classification (e.g., A, B, C, D, E carcinogens). For dose

response assessments, two steps will be involved: determining the range

of observation (observed effect) and the range of extrapolation. To

characterize the cancer potency, a biologically-based chemical-specific

model will be used. In many cases, however, sufficient data may not

exist to apply a biological based model. In these cases, linear and

nonlinear defaults will be used. A linear default will be used for

those chemicals which indicate they are DNA reactive or when other

evidence supports linearity. In addition, if a chemical is not DNA

reactive but insufficient data exist to characterize a nonlinear mode

of action, linearity will be assumed and a linear default will be

recommended. The nonlinear default (margin of exposure approach) will

be used for those chemicals which are not DNA reactive and for those

for which sufficient data to characterize a nonlinear mode of action

exist.

2. For noncarcinogens, the concept of an expressing an RfD as a

range rather than a single value will be presented for comment. In

developing water quality criteria, EPA will provide a default RfD

which, in most cases, will be the midpoint of the range, commonly

referred to as the point estimate. Alternative approaches, such as the

benchmark dose and categorical regression analysis may be employed in

developing an RfD and analyzing the risk above the RfD point estimate.

3. Default fish and shellfish consumption values are presented for

the general population, for sportfishers, and for subsistence fishers,

replacing the single value of 6.5 grams/day used in the 1980 guidance.

States may use a fish and shellfish intake level derived from local

data on fish and shellfish consumption in place of the default values

provided. However, the fish and shellfish intake level chosen must be

protective of highly exposed individuals in the population.

4. All criteria should be derived using a bioaccumulation factor

(BAF); none should be derived using a bioconcentration factor (BCF),

which was used in the 1980 guidance.

5. As an alternative to expressing ambient water quality criteria

as a water concentration, criteria may also be expressed in terms of

fish tissue concentration. For some substances, particularly those that

are expected to exhibit substantial bioaccumulation, the ambient water

quality criteria derived may have extremely low values, possibly below

the practical limits for detecting and quantifying the substance in the

water column. It may be more practical and meaningful in these cases to

focus on the concentration of those substances in fish tissue, since

fish ingestion would be the predominant source of exposure for these

substances that bioaccumulate.

6. When deriving ambient water quality criteria for noncarcinogens

and nonlinear carcinogens, a factor (referred to as the relative source

contribution) should be included to account for other non-water

exposure sources so that the entire RfD will not be not allocated to

drinking water and fish consumption alone.

For more details on these changes and others, please refer to the

upcoming Federal Register notice.

It should be noted that the changes outlined above may result in

significant numeric changes in the ambient water quality criteria. For

example, for those chemicals which are bioaccumulative in nature (e.g.,

with bioconcentration factors (BCFs) of 300 or more), bioaccumulation

factors may be developed which are 1-3 orders of magnitude greater than

the BCFs developed in 1980. This would result in a criterion which is

1-3 orders of magnitude more stringent, if all other parameters (such

as RfDs and q1 *s) remain roughly unchanged.

EPA will continue to rely on existing criteria as the basis for

regulatory and non-regulatory decisions, until EPA revises and reissues

a 304(a) criteria guidance using the revised final human health

criterion methodology. The existing criteria are still viewed as

scientifically acceptable by EPA. The intention of the methodology

revisions is to present the latest scientific advancements in the areas

of risk and exposure assessment in order to incrementally improve the

already sound toxicological and exposure bases for these criteria. As

EPA's current human health criteria are the product of several years

worth of development, it is reasonable to assume that revisiting all

existing criteria could require comparable amounts of time and

resources. Given these circumstances, EPA is proposing a process for

revisiting these criteria as part of the overall revisions to the

methodology for deriving human health criteria that is expected to be

published in the Federal Register in 1997.

[[Page 42178]]

The State of California in its Ocean Plan, adopted in 1990 and

approved by EPA in 1991, established numerical water quality criteria

using an average fish and shellfish consumption rate of 23 grams per

day. This value is based on an earlier California Department of Health

Services estimate. The State is currently in the process of readopting

its water quality control plans for inland surface waters, enclosed

bays, and estuaries. The State intends to consider information on fish

and shellfish consumption rates evaluated and summarized in a recent

report prepared by the State's Office of Environmental Health Hazard

Assessment. The report, which is undergoing final evaluation, is

expected to be made public in 1997. EPA supports the State's use of any

appropriate higher state-specific fish and shellfish consumption rates

in its readoption of criteria in its statewide plans.

a. 2,3,7,8-TCDD (Dioxin) Criteria

In today's action, EPA is proposing human health water quality

criteria for 2,3,7,8-tetrachlorodibenzo-p-dioxin (``dioxin'') at the

same levels as promulgated in the NTR, as amended. These criteria are

derived from EPA's 1984 CWA section 304(a) criteria guidance document

for dioxin.

EPA has been evaluating the health threat posed by dioxin nearly

continuously for well over a decade. Following issuance of the 1984

criteria guidance document, evaluating the health effects of dioxin and

recommending human health criteria for dioxin, EPA prepared draft

reassessments reviewing new scientific information relating to dioxin

in 1985 and 1988. EPA's Science Advisory Board (SAB), reviewing the

1988 draft reassessment, concluded that while the risk assessment

approach used in 1984 criteria guidance document had inadequacies, a

better alternative was unavailable (see SAB's Dioxin Panel Review of

Documents from the Office or Research and Development relating to the

Risk and Exposure Assessment of 2,3,7,8-TCDD (EPA--SAB-EC-90-003,

November 28, 1989) included in the administrative record for today's

proposed rule). Between 1988 and 1990, EPA issued numerous reports and

guidances relating to the control of dioxin discharges from pulp and

paper mills. See e.g., EPA Memorandum, ``Strategy for the Regulation of

Discharges of PHDDs & PHDFs from Pulp and Paper Mills to the Waters of

the United States,'' from Asst. Administrator for Water to Regional

Water Mgmt Div. Directors and NPDES State Directors, dated May 21, 1990

(AR NL-16); EPA Memorandum, ``State Policies, Water Quality Standards,

and Permit Limitations Related to 2,3,7,8-TCDD in Surface Water,'' from

Assistant Administrators to Water Management Div. Directors, dated

January 5, 1990 (AR VA-66). These documents are available in the

administrative record for today's proposed rule.

In 1991, EPA's Administrator announced another scientific

reassessment of the risks of exposure to dioxin (see Memorandum from

Administrator William K. Reilly to Erich W. Bretthauer, Assistant

Administrator for Research and Development and E. Donald Elliott,

General Counsel, entitled Dioxin: Follow-Up to Briefing on Scientific

Developments, April 8, 1991, included in the administrative record for

today's proposed rule). At that time, the Administrator made clear that

while the reassessment was underway, EPA would continue to regulate

dioxin in accordance with existing Agency policy and existing risk

methodologies. Thereafter, the Agency proceeded to regulate dioxin in a

number of environmental programs, including standards under the Safe

Drinking Water Act and the Clean Water Act.

The Administrator's promulgation of the dioxin human health

criteria in the 1992 NTR affirmed his decision that the ongoing

reassessment should not defer or delay regulating this potent

contaminant, and further, that the risk assessment in the 1984 criteria

guidance document for dioxin continued to be scientifically defensible.

Until the reassessment process was completed, the Agency could not

``say with any certainty what the degree or directions of any changes

in the risk estimates might be'' (57 F. R. at 60863-64).

The basis for the dioxin criteria as well as the decision to

include the dioxin criteria in the 1992 NTR pending the results of the

reassessment were challenged. See American Forest and Paper Ass'n, Inc.

et al. v. U.S. EPA (Consolidated Case No. 93-0694 (RMU) D.D.C.). By

order dated September 4, 1996, the Court upheld EPA's decision. EPA's

brief and the Court's decision are included in the administrative

record for today's proposed rule.

EPA has undertaken significant effort toward completion of the

dioxin reassessment. On September 13, 1994, EPA released for public

review and comment a draft reassessment of toxicity and exposure to

dioxin. See Health Assessment Document for 2,3,7,8-Tetrachlorobenzo-p-

Dioxin (TCDD) and Related Compounds, U.S. EPA, 1994. EPA is currently

addressing comments made by the public and the SAB and anticipates that

the final revised reassessment will go to the SAB in the near future.

With today's proposal, the Administrator reaffirms that,

notwithstanding the on-going risk reassessment, EPA intends to continue

to regulate dioxin to avoid further harm to public health, and the

basis for the dioxin criteria, both in terms of the cancer potency and

the exposure estimates, remains scientifically defensible. The fact

that EPA is reassessing the risk of dioxin, virtually a continuous

process to evaluate new scientific information, does not mean that the

current risk assessment is ``wrong''. It continues to be EPA's position

that until the risk assessment for dioxin is revised, EPA supports and

will continue to use the existing risk assessment for the regulation of

dioxin in the environment. Accordingly, EPA today proposes dioxin

criteria based on the 1984 criteria guidance document for dioxin and

promulgated in the NTR in 1992.

Toxicity Equivalency: The State of California, in its 1991 water

quality control plans, adopted human health criteria for dioxin and

dioxin-like compounds based on the concept of toxicity equivalency

(TEQ) using toxicity equivalency factors (TEFs). EPA Region 9 reviewed

and approved the State's use of the TEQ concept and TEFs in setting the

State's human health water quality criteria for dioxin and dioxin-like

compounds.

In 1987, EPA formally embraced the TEQ concept as an interim

procedure to estimate the risks associated with exposures to 210

chlorinated dibenzo-p-dioxin and chlorinated dibenzofuran (CDD/CDF)

congeners, including 2,3,7,8-TCDD. This procedure uses a set of derived

TEFs to convert the concentration of any CDD/CDF congener into an

equivalent concentration of 2,3,7,8-TCDD. In 1989, EPA updated its TEFs

based on an examination of relevant scientific evidence and a

recognition of the value of international consistency. This updated

information can be found in EPA's 1989 Update to the Interim Procedures

for Estimating Risks Associated with Exposures to Mixtures of

Chlorinated Dibenzo-p-dioxins and -dibenzofurans (CDDs and CDFs) (EPA /

625/3-89/016, March 1989). EPA had been active in an international

effort aimed at adopting a common set of TEFs (International TEFs/89 or

I-TEFs/89), to facilitate information exchange on environmental

contamination of CDD/CDF. This document reflects EPA's support of an

internationally consistent set of TEFs, the I-TEFs/89.

EPA uses I-TEFs/89 in many of its regulatory programs, and

encourages

[[Page 42179]]

their use in state programs. EPA supports and encourages the State of

California's use of EPA's 1989 Interim Procedures in implementing the

2,3,7,8-TCDD water quality criteria contained in today's proposed rule.

The concept of TEQ and the use of the I-TEFs/89, as outlined in EPA's

1989 Interim Procedures, provide valuable guidance in using the

2,3,7,8-TCDD water quality criteria in setting National Pollutant

Discharge Elimination System (NPDES) water quality-based permit limits

that are protective of human health for dioxin and dioxin-like

compounds.

b. Arsenic Criteria

EPA is not proposing human health criteria for arsenic in today's

proposed rule. EPA recognizes that EPA promulgated human health water

quality criteria for arsenic for a number of states in 1992 based on

EPA's 1980 section 304(a) criteria guidance for arsenic as updated in

IRIS. However, a number of issues and uncertainties have arisen

concerning the health effects of arsenic. These issues and

uncertainties (summarized in ``Issues Related to Health Risk of

Arsenic'' contained in the administrative record for today's proposed

rule) include arsenic exposure evaluations, metabolism and

detoxification processes, analytical methods, and effects at low doses.

EPA has determined that these issues and uncertainties are sufficiently

significant to necessitate a careful evaluation of the risks of arsenic

exposure before the Agency promulgates water quality criteria for

arsenic in additional states. Today's decision is consistent with the

recent decision by the Assistant Administrator for Water (Memorandum

from R. Perciasepe to Assistant and Regional Administrators dated

February 6, 1995, also included in the administrative record) deferring

the revision of the drinking water standard of 0.05 mg/l for arsenic

pending, among other things, the review of the risk assessment for

arsenic. This review is currently underway.

Given these circumstances, EPA has made a risk management decision

not to propose human health criteria for arsenic. Permitting

authorities in California should rely on existing narrative water

quality criteria to establish effluent limitations as necessary for

arsenic. California has previously expressed its science and policy

position by establishing a criterion level of 5 g/l for

arsenic; EPA recommends that permitting authorities refer to that value

in evaluating and interpreting the narrative water quality criteria.

c. Mercury Criteria

The criteria proposed here use the latest RfD in EPA's Integrated

Risk Information System (IRIS) and the weighted average practical

bioconcentration factor (PBCF) from the 1980 section 304(a) criteria

guidance document for mercury. EPA considered the approach used in the

Great Lakes Water Quality Initiative (GLI) incorporating

Bioaccumulation Factors (BAFs), but rejected this approach for reasons

stated below. The equation used here to derive an ambient water quality

criterion for mercury from exposure to organisms and water is the

following:

For organism and water consumption:

[GRAPHIC] [TIFF OMITTED] TP05AU97.002

Where:

RfD = Reference Dose

BW = Body Weight

WC = Water Consumption

FC = Total Fish and Shellfish Consumption per Day

PBCF = Practical Bioconcentration Factor (weighted average)

For mercury, the most current RfD from IRIS is 1 x 10-4

mg/kg/day. The RfD is derived from a benchmark dose analysis using a

parts per million (ppm) maternal hair concentration as the exposure

surrogate and the combination of all neurological effects in infants as

the response variable from the Marsh et. al (1987) study. A Weibel

model for extra risk was used. The resulting estimated dose at 10%

extra risk was 11 ppm of maternal hair, or about 1 x 10-3

mg/kg/day. An uncertainty factor of 10 was included to arrive at an RfD

of 1 x 10-4 mg/kg/day. This factor is composed of a half-log

of 10 for within-human variability and a half log of 10 for database

insufficiency, notably the lack of a two generation reproductive study.

The body weight used in the equation for the mercury criteria, as

discussed in the Human Health Guidelines, is a mean adult human body

weight of 70 kg. The drinking water consumption rate, as discussed in

the Human Health Guidelines, is 2.0 liters per day.

The fish and shellfish consumption for mercury takes into account

both average fish and shellfish consumption and average intake from

each body of water. The value for the fish and shellfish consumption is

based on the average total intake of fish and shellfish from fresh

water, estuarine coastal and open oceans (18.7 g/day). The average

individual fish and shellfish consumption from freshwater bodies is

1.72 g/day (0.00172 kg), from estuarine-coastal waters is 4.78 g/day

(0.00478 kg), and from open oceans is 12.2 g/day (0.0122 kg). Species

of fish and shellfish used in the calculation are those from which

information was available on human consumption on average mercury

concentration in edible tissue. See Ambient Water Quality Criteria for

Mercury (EPA 440/5-80-058).

The BCF is defined as the ratio of chemical concentration in the

organism to that in surrounding water. Bioconcentration occurs through

uptake and retention of a substance from water only, through gill

membranes or other external body surfaces. In the context of setting

exposure criteria it is generally understood that the terms ``BCF'' and

``steady-state BCF'' are synonymous. A steady-state condition occurs

when the organism is exposed for a sufficient length of time that the

ratio does not change substantially.

The BCFs that were used herein are the ``Practical Bioconcentration

Factors (PBCFs)'' that were derived in 1980: 5500 for fresh water, 3765

for estuarine coastal waters, and 9000 for open oceans. See pages C-

100-1 of Ambient Water Quality Criteria for Mercury (EPA 440/5-80-058)

for a complete discussion on the PBCF. Because of the way they were

derived, these PBCFs take into account uptake from food as well as

uptake from water. A weighted average PBCF was calculated to take into

account the average consumption from the three waters using the

following equation:

[[Page 42180]]

[GRAPHIC] [TIFF OMITTED] TP05AU97.003

Given the large value for the weighted average PBCF, the contribution

of drinking water to total daily intake is negligible so that

assumptions concerning the chemical form of mercury in drinking water

become less important. The human health mercury criteria proposed for

this rule are based on the latest RfD as listed in IRIS and a weighted

PBCF from the 1980 304(a) criteria guidance document for mercury.

On March 23, 1995 (60 FR 15366), EPA promulgated the Great Lakes

Water Quality Initiative (GLI). The GLI incorporated bioaccumulation

factors (BAFs) in the derivation of criteria to protect human health

because it is believed BAFs are a better predictor than BCFs of the

concentration of a chemical within fish tissue as it includes

consideration of the uptake of contaminants from all routes of

exposure. A bioaccumulation factor is defined as the ratio (in L/kg) of

a substance's concentration in tissue to the concentration in the

ambient water, in situations where both the organism and its food are

exposed and the ratio does not change substantially over time. The

final GLI establishes a hierarchy of four methods for deriving BAFs for

non-polar organic chemicals: (1) Field-measured BAFs; (2) predicted BAF

derived using a field-measured biota-sediment accumulation factor; (3)

predicted BAFs derived by multiplying a laboratory-measured BCF by a

food chain multiplier; and 4) predicted BAFs derived by multiplying a

BCF calculated from the log Kow by a food-chain multiplier. The final

GLI developed BAFs for trophic levels three and four fish of the Great

Lakes Basin. Respectively, the BAFs for mercury for trophic level 3 and

4 fish were: 27,900 and 140,000.

The BAF promulgated in the GLI was developed specifically for the

Great Lakes System. It is uncertain whether the BAFs of 27,900 and

140,000 are appropriate for use in California at this time, and thus,

this proposal does not use the BAF in setting the human health criteria

for mercury. To a considerable degree the magnitude of the BAF for

mercury in a given system depends on how much of the total mercury in

that system is present in the methylated form. Methylation rates very

widely from one aquatic system to another for reasons that are not

fully understood. Lacking the data, it is difficult to determine if the

BAF used in the GLI represent the potential for mercury bioaccumulation

in surface waters in California. It should be noted, however, that

there is no scientific reason to believe that a true average BAF in

California, were it known, would be lower than that developed for the

Great Lakes basin; that is, the true average for California could be

higher or lower than the BAF developed for the GLI.

EPA is developing a national BAF for mercury. The mercury BAF is

part of the Mercury Study Report to Congress: SAB Review Draft (The

Draft Report to Congress) . The Draft Report to Congress is currently

available through NTIS (EPA-452/R-96-001a-h) . The next step is for the

SAB to review the Draft Report to Congress. After the SAB reviews the

Draft Report and the Agency makes changes based on their comments, the

Report to Congress will be released with a final national BAF for

mercury. Once the Report to Congress has been publicly reviewed, and

finalized, the Agency will consider the science and could make changes

to the section 304(a) criteria guidance for mercury to reflect the

recommendation of the Report to Congress. If the section 304(a)

criteria guidance for mercury changes, states will be expected to

review their water quality standards for mercury and determine if their

standards are protective.

d. Polychlorinated Biphenyls (PCBs) Criteria

The NTR, as amended, calculated human health criteria for PCBs

using a cancer potency factor of 7.7 per (mg/kg)/day from the Agency's

IRIS. This cancer potency factor was derived from the Norback and

Weltman (1985) study which looked at rats that were fed Aroclor 1260.

The study used the linearized multistage model with a default cross-

species scaling factor (body weight ratio to the 2/3 power). Although

it is known that PCB congeners vary greatly as to their potency in

producing biological effects, for purposes of its carcinogenicity

assessment, EPA considered Aroclor 1260 to be representative of all PCB

mixtures. The Agency did not pool data from all available congener

studies or generate a geometric mean from these studies, since the

Norback and Weltman study was judged by EPA as acceptable, and not of

marginal quality, in design or conduct as compared with other studies.

Thereafter, the Institute for Evaluating Health Risks (IEHR, 1991)

reviewed the pathological slides from the Norback and Weltman study,

and concluded that some of the malignant liver tumors should have been

interpreted as nonmalignant lesions, and that the cancer potency factor

should be 5.1 per (mg/kg)/day as compared with EPA's 7.7 per (mg/kg)/

day.

The Agency's recent peer-reviewed reassessment of the cancer

potency of PCBs published in a final report, PCBs: Cancer Dose-Response

Assessment and Applications to Environmental Mixtures (EPA/600/P-96/

001F), adopts a different approach that distinguishes among PCB

mixtures by using information on environmental processes. (The report

is included in the administrative record of today's proposed rule.) The

report considers all cancer studies (which used commercial mixtures

only) to develop a range of cancer potency factors, then uses

information on environmental processes to provide guidance on choosing

an appropriate potency factor for representative classes of

environmental mixtures and different pathways. The reassessment

provides that, depending on the specific application, either central

estimates or upper bounds can be appropriate. Central estimates

describe a typical individual's risk, while upper bounds provide

assurance (i.e., 95% confidence) that this risk is not likely to be

underestimated if the underlying model is correct. Central estimates

are used for comparing or ranking environmental hazards, while upper

bounds provide information about the precision of the comparison or

ranking. In the reassessment, the use of the upper bound values were

found to increase cancer potency estimates by two or

[[Page 42181]]

three-fold over those using central tendency. Upper bounds are useful

for estimating risks or setting exposure-related standards to protect

public health, and are used by EPA in quantitative cancer risk

assessment. Thus, the cancer potency of PCB mixtures is determined

using a tiered approach based on environmental exposure routes with

upper-bound potency factors (using a body weight ratio to the 3/4

power) ranging from 0.07 (lowest risk and persistence) to 2 (high risk

and persistence) per (mg/kg)/day for average lifetime exposures to

PCBs. It is noteworthy that bioaccumulated PCBs appear to be more toxic

than commercial PCBs and appear to be more persistent in the body. For

exposure through the food chain, risks can be higher than other

exposures.

EPA issued the final reassessment report on September 27, 1996 and

updated IRIS to include the reassessment on October 1, 1996. For this

proposed rule, EPA derived the human health criteria for PCBs using a

cancer potency factor of 2 per (mg/kg)/day, an upper bound potency

factor reflecting high risk and persistence. This decision is based on

recent multimedia studies indicating that the major pathway of exposure

to persistent toxic substances such as PCBs is via dietary exposure

(i.e., contaminated fish and shellfish consumption).

Following is the calculation of the human health criterion (HHC)

for organism and water consumption:

[GRAPHIC] [TIFF OMITTED] TP05AU97.004

Where:

RF=Risk Factor=1 x 10 (-6)

BW=Body Weight=70 kg

q1*=Cancer slope factor=2 kg-day/mg

WC=Water Consumption=2 l/day

FC=Fish and Shellfish Consumption=0.0065 kg/day

BCF=Bioconcentration Factor=31,200

the HHC (g/l)=0.00017 g/l (rounded to two significant

digits).

Following is the calculation of the human health criterion for

organism only consumption:

[GRAPHIC] [TIFF OMITTED] TP05AU97.005

Where:

RF=Risk Factor=1 x 10 (-6)

BW=Body Weight=70 kg

q1*=Cancer slope factor=2 kg-day/mg

FC=Total Fish and Shellfish Consumption per Day=0.0065 kg/day

BCF=Bioconcentration Factor=31,200

the HHC (g/l)=0.00017 g/l (rounded to two significant

digits).

The criteria are both equal to 0.00017 g/l and apply to

the total PCBs or congener or isomer analyses (PCBs exposures should

not be characterized in terms of aroclors). See PCBs: Cancer Dose

Response Assessment and Application to Environmental Mixtures (EPA/600/

9-96-001F). For a discussion of the body weight, water consumption, and

fish and shellfish consumption factors, see the Human Health

Guidelines. For a discussion of the BCF, see the 304(a) criteria

guidance document for PCBs (included in the administrative record for

this proposed rulemaking).

e. Section 304(a) Human Health Criteria Excluded

As is the case in the NTR, as amended, today's proposed rule does

not propose criteria for certain priority pollutants for which CWA

section 304(a) criteria guidance exists because those criteria were not

based on toxicity to humans or aquatic organisms. The basis for these

particular criteria is organoleptic effects (e.g., taste and odor)

which would make water and edible aquatic life unpalatable but not

toxic. Because the basis for this rule is to protect the public health

and aquatic life from toxicity consistent with the language and intent

in CWA section 303(c)(2)(B), EPA is promulgating criteria only for

those priority toxic pollutants whose criteria recommendations are

based on toxicity. The CWA section 304(a) human health criteria based

on organoleptic effects for zinc and 3-methyl-4-chlorophenol are

excluded for this reason. See the 1992 NTR discussion at 57 FR 60864.

f. Cancer Risk Level

EPA's CWA section 304(a) criteria guidance documents for priority

toxic pollutants that are based on carcinogenicity present

concentrations for upper bound risk levels of 1 excess cancer case per

100,000 people (10-5), per 1,000,000 people

(10-6), and per 10,000,000 people (10-7).

However, the criteria documents do not recommend a particular risk

level as EPA policy.

In today's proposed rule, EPA is proposing criteria that protect at

an incremental cancer risk level of one in a million (10-6)

for all priority toxic pollutants regulated as carcinogens, consistent

with those criteria promulgated in the NTR, as amended, for the State

of California. The State had requested EPA to use a 10-6

risk level for carcinogenic pollutants in the NTR. In addition,

standards adopted by the State contained in the Enclosed Bays and

Estuaries Plan (EBEP), and the Inland Surface Waters Plan (ISWP),

partially approved by EPA on November 6, 1991, and the Ocean Plan

approved by EPA on June 28, 1990, contain a risk level of

10-6 for most carcinogens. Thus, the State has historically

protected at a 10-6 risk level for carcinogenic pollutants.

For today's proposed rule, the State has indicated a preference for EPA

to propose criteria for carcinogenic pollutants at a 10-6

risk level, but to also discuss and request comment on a

10-5 risk level. Therefore, EPA is explicitly requesting

comment on the adoption of a 10-5 risk level for

carcinogenic pollutants proposed in this rule for the State of

California. The effect of a 10-5 risk level will be to

increase carcinogenic pollutant criteria values (noted in today's

proposed matrix by footnote c) which are not already promulgated in the

NTR, as amended, by one order of magnitude. For example, the proposed

organism-only criterion for gamma BHC (pollutant number 105 in the

matrix) is 0.013 g/l; the criterion based on a 10-5

risk level would be 0.13 g/l.

The State, in its readoption of its statewide plans for inland

surface waters and enclosed bays and estuaries may consider other risk

levels for carcinogenic pollutants. EPA

[[Page 42182]]

recommends that states consider minimum risk levels in the range of

10-4 to 10-6 for carcinogenic priority toxic

pollutants to protect public health and welfare. See Human Health

Guidelines.

F. Description of the Proposed Rule

1. Scope

Subpart (a), entitled ``Scope'', states that this rule is a

proposed promulgation of criteria for priority toxic pollutants in the

State of California for inland surface waters, enclosed bays, and

estuaries. Subpart (a) also states that this rule contains an

authorizing compliance schedule provision.

2. EPA Criteria for Priority Toxic Pollutants

EPA's proposed criteria for California are presented in tabular

form that will appear at 40 CFR 131.38. For ease of presentation, the

table that appears in this proposed rule combines water quality

criteria promulgated in the NTR, as amended, that are outside the scope

of this rulemaking, with the proposed criteria that are within the

scope of today's proposed rule. This is intended to help readers

determine applicable wate

This text is long and has been trimmed here. Open the source document for the complete record.