Lead and Lead Compounds; Lowering of Reporting Thresholds; Community Right-to-Know Toxic Chemical Release Reporting

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 372

[OPPTS-400140D; FRL-6722-4]

RIN 2070-AD38

Lead and Lead Compounds; Lowering of Reporting Thresholds; Community Right-to-Know Toxic Chemical Release Reporting

AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Final rule.

SUMMARY:

EPA is lowering the reporting thresholds for lead and lead compounds which are subject to reporting under section 313 of the Emergency Planning and Community Right-to-Know Act of 1986 (EPCRA) and section 6607 of the Pollution Prevention Act of 1990 (PPA). The reporting thresholds are being lowered to 100 pounds. The lower reporting thresholds apply to lead and all lead compounds except for lead contained in stainless steel, brass, and bronze alloys. EPA is taking these actions pursuant to its authority under EPCRA section 313(f)(2) to revise reporting thresholds. Today's actions also include modifications to certain reporting exemptions and requirements for lead and lead compounds.

DATES:

This rule shall take effect on February 16, 2001; with the first reports at the lower thresholds due on or before July 1, 2002, for the 2001 calendar year.

FOR FURTHER INFORMATION CONTACT:

For technical information on this final rule contact: Daniel R. Bushman, Petitions Coordinator, Environmental Protection Agency, Mail Code 2844, 1200 Pennsylvania Ave., NW., Washington, DC 20460; telephone number 202-260-3882, e-mail address: bushman.daniel@epa.gov. For general information on EPCRA section 313, contact the Emergency Planning and Community Right-to-Know Hotline, Environmental Protection Agency, Mail Code 5101, 1200 Pennsylvania Ave., NW., Washington, DC 20460, Toll free: 1-800-535-0202, in Virginia and Alaska: 703-412-9877 or Toll free TDD: 1-800-553-7672. Information concerning this action is also available on EPA's Web site at http://www.epa.gov/tri.

SUPPLEMENTARY INFORMATION:

I. General Information

A. Does this notice apply to me?

You may be potentially affected by this action if you manufacture, process, or otherwise use lead or lead compounds. Potentially affected categories and entities may include, but are not limited to:

Category

Examples of Potentially Affected Entities

Industry

SIC major group codes 10 (except 1011, 1081, and 1094), 12 (except 1241); or 20 through 39; or industry codes 4911 (limited to facilities that combust coal and/or oil for the purpose of generating power for distribution in commerce); or 4931 (limited to facilities that combust coal and/or oil for the purpose of generating power for distribution in commerce); or 4939 (limited to facilities that combust coal and/or oil for the purpose of generating power for distribution in commerce); or 4953 (limited to facilities regulated under the Resource Conservation and Recovery Act, subtitle C, 42 U.S.C. section 6921

et seq.

); or 5169; or 5171; or 7389 (limited to facilities primarily engaged in solvent recovery services on a contract or fee basis)

Federal Government

Federal facilities

This table is not intended to be exhaustive, but rather provides a guide for readers regarding entities likely to be affected by this action. Other types of entities not listed in the table could also be affected. To determine whether your facility would be affected by this action, you should carefully examine the applicability criteria in part 372 subpart B of Title 40 of the Code of Federal Regulations. If you have questions regarding the applicability of this action to a particular entity, consult the person listed in the preceding of

FOR FURTHER INFORMATION CONTACT

section.

B. How can I get additional information or copies of this document or other support documents?

1.

Electronically

. You may obtain electronic copies of this document from the EPA internet Home Page at http://www.epa.gov/. On the Home Page select “Laws and Regulations” and then look up the entry for this document under the “

Federal Register

—Environmental Documents.” You can also go directly to the “

Federal Register

” listings at http://www.epa.gov/fedrgstr/.

2.

In person

. The Agency has established an official record for this action under docket control number OPPTS-400140. The official record consists of the documents specifically referenced in this action, any public comments received during an applicable comment period, and other information related to this action, including any information claimed as confidential business information (CBI). This official record includes the documents that are physically located in the docket, as well as the documents that are referenced in those documents. The public version of the official record does not include any information claimed as CBI. The public version of the official record, which includes printed, paper versions of any electronic comments submitted during an applicable comment period, is available for inspection in the TSCA Nonconfidential Information Center, North East Mall Rm. B-607, Waterside Mall, 401 M St., SW., Washington, DC. The Center is open from noon to 4 p.m., Monday through Friday, excluding legal holidays. The telephone number of the Center is (202) 260-7099.

II. What is EPA's Statutory Authority for Taking These Actions?

EPA is finalizing these actions under sections 313(f)(2), 313(g), 313(h), and 328 of EPCRA, 42 U.S.C. 11023(f)(2), 11023(g), 11023(h), and 11048; and section 6607 of PPA, 42 U.S.C. 13106. Section 313 of EPCRA requires certain facilities manufacturing, processing, or otherwise using a listed toxic chemical in amounts above reporting threshold levels, to report certain facility specific information about such chemicals, including the annual releases and other quantities entering each environmental medium. These reports must be filed by July 1 of each year for the previous calendar year. Such facilities also must report recycling and other waste management data and source reduction activities for such chemicals, pursuant to section 6607 of PPA.

A. What is EPA's Statutory Authority To Lower EPCRA Reporting Thresholds?

EPA is finalizing these actions pursuant to its authority under EPCRA section 313(f)(2) to revise reporting thresholds. EPCRA section 313

establishes default reporting thresholds, which are set forth in section 313(f)(1). Section 313(f)(2), however, provides that EPA:

may establish a threshold amount for a toxic chemical different from the amount established by paragraph (1). Such revised threshold shall obtain reporting on a substantial majority of total releases of the chemical at all facilities subject to the requirements of this section. The amounts established by EPA may, at the Administrator's discretion, be based on classes of chemicals or categories of facilities.

This provision provides EPA with broad, but not unlimited, authority to establish thresholds for particular chemicals, classes of chemicals, or categories of facilities, and commits to EPA's discretion the determination that a different threshold is warranted. Congress also committed the determination of the levels at which to establish any alternate thresholds to EPA's discretion, requiring only that any “revised threshold shall obtain reporting on a substantial majority of total releases of the chemical at all facilities subject to the requirements” of section 313. 42 U.S.C. 11023(f)(2).

For purposes of determining what constitutes a “substantial majority of total releases,” EPA interprets the language in section 313(f)(2), “facilities subject to the requirements of [section 313],” to refer to those facilities that fall within the category of facilities described by sections 313 (a) and (b), i.e., the facilities currently reporting. Subsection (a) lays out the general requirement that “the owner or operator of facilities subject to the requirements of this section shall” file a report under EPCRA section 313. Subsection (b) then defines the facilities subject to the requirements of this section:

[t]he requirements of this section shall apply to owners and operators of facilities that have 10 or more full-time employees and that are in Standard Industrial Classification Codes 20-39, . . . and that manufactured, processed, or otherwise used a toxic chemical listed under subsection (c) of this section in excess of the quantity of that toxic chemical established under subsection (f) of this section during the calendar year for which a toxic chemical release form is required under this section.

Thus, in revising the reporting thresholds, EPA must ensure that, under the new thresholds, a substantial majority of releases currently being reported will continue to be reported. No further prerequisites for exercising this authority appears in the statute.

B. What is EPA's Statutory Authority for Making Modifications to Other EPCRA section 313 Reporting Requirements?

Today's actions also include modifications to certain reporting exemptions and requirements for lead and lead compounds. Congress granted EPA rulemaking authority to allow the Agency to fully implement the statute. EPCRA section 328 provides that the “Administrator may prescribe such regulations as may be necessary to carry out this chapter” (28 U.S.C. 11048).

III. Background Information

A. What is the General Background for this Action?

Under EPCRA section 313, Congress set the initial parameters of the Toxics Release Inventory (TRI), but also gave EPA clear authority to modify reporting in various ways, including authority to change the toxic chemicals subject to reporting, the facilities required to report, and the threshold quantities that trigger reporting. By providing this authority, Congress recognized that the TRI program would need to evolve to meet the needs of a better informed public and to refine existing information. EPA has, therefore, undertaken a number of actions to expand and enhance TRI. These actions include expanding the number of reportable toxic chemicals by adding 286 toxic chemicals and chemical categories to the EPCRA section 313 list in 1994. Further, a new category of facilities was added to EPCRA section 313 on August 3, 1993, through Executive Order 12856, which requires Federal facilities meeting threshold requirements to file annual EPCRA section 313 reports. In addition, in 1997 EPA expanded the number of private sector facilities that are required to report under EPCRA section 313 by adding seven new industrial groups to the list of covered facilities. At the same time, EPA has sought to reduce the burden of EPCRA section 313 reporting by actions such as delisting chemicals it has determined do not meet the statutory listing criteria and establishing an alternate reporting threshold of 1 million pounds for facilities with 500 pounds or less of production-related releases and other wastes. Facilities meeting the requirements of this alternate threshold may file a certification statement (Form A) instead of reporting on the standard EPCRA section 313 form, the Form R.

On October 29, 1999 (64 FR 58666), EPA finalized enhanced reporting requirements that focused on a unique group of toxic chemicals that persist and bioaccumulate in the environment. These chemicals are commonly referred to as persistent bioaccumulative toxic chemicals or PBT chemicals. Until that action, with the exception of the alternate threshold certification on Form A, EPA had not altered the statutory reporting threshold for any listed chemicals. However, as the TRI program has evolved over time and as communities identify areas of special concern, thresholds and other aspects of the EPCRA section 313 reporting requirements may need to be modified to assure the collection and dissemination of relevant, topical information and data. Toxic chemicals that persist and bioaccumulate are of particular concern because they remain in the environment for significant periods of time and concentrate in the organisms exposed to them. The October 29, 1999, PBT chemical final rule set forth criteria to be used by the EPCRA section 313 program for evaluating whether a listed toxic chemical persists or bioaccumulates in the environment. EPA has evaluated lead and lead compounds using these criteria, and has concluded that lead and lead compounds are PBT chemicals. Thus, as with the PBT chemical final rule, today's action further increases the utility of TRI to the public by lowering the reporting thresholds for lead and lead compounds. Lowering the reporting thresholds for lead and lead compounds will ensure that the public has important information on the quantities of these chemicals released or otherwise managed as waste, that would not be reported under the 10,000 and 25,000 pound/year thresholds that apply to most other listed toxic chemicals.

B. What Outreach Has EPA Conducted?

EPA has engaged in a comprehensive outreach effort relating to this action. This outreach served to inform interested parties, including industries and small businesses affected by the rule, state regulatory officials, environmental organizations, labor unions, community groups, and the general public of EPA's intention to lower the applicable EPCRA section 313 reporting thresholds for lead and lead compounds. EPA held three public meetings (in Los Angeles, CA (November 30, 1999); Chicago, IL (December 2, 1999); and Washington, DC (December 14, 1999)) during the comment period for the proposal. Participants included a range of industry representatives, trade associations (representing both small and large businesses), law firms representing industry groups, environmental groups, the general public, plus other groups and organizations. For state and tribal governments, EPA attended the regularly-held public meetings of the Forum on State and Tribal Toxics

Action (FOSTTA) to discuss the proposed rule. EPA also received substantial public comment on the proposed rule, to which EPA is responding in this Final Rule and the Response to Comments document (Ref. 1). In response to the strong interest in the proposed rule, and to allow more individuals and groups to submit their comments, EPA extended the public comment period. The comment period was first extended from September 17 to November 1, 1999 (at 64 FR 51091, September 21, 1999) (FRL-6382-9) and then again from November 1 to December 16, 1999 (at 64 FR 58370, October 29, 1999) (FRL-6391-8) to allow commenters time to supplement or revise their comments in light of the decisions made in the final PBT chemical rulemaking (64 FR 58666). Additional information regarding EPA's outreach may be found in supporting documents included in the public version of the official record.

IV. Summary of Proposal

A. What Persistence and Environmental Fate Data were Presented for Lead and Lead Compounds?

A chemical's persistence refers to the length of time the chemical can exist in the environment before being destroyed (i.e., transformed) by natural processes. The environmental media for which persistence is measured or estimated include air, water, soil, and sediment; however, water is the medium for which persistence values are most frequently available. It is important to distinguish between persistence in a single medium (air, water, soil, or sediment) and overall environmental persistence. Persistence in an individual medium is controlled by transport of the chemical to other media, as well as transformation to other chemical species. Persistence in the environment as a whole is a distinct concept. It is based on the observations that the environment behaves as a set of interconnected media, and that a chemical substance released to the environment will become distributed in these media in accordance with the chemical's intrinsic (physical/chemical) properties and reactivity. For overall persistence, only irreversible transformation contributes to net loss of a chemical substance.

Although metals and metal compounds, including lead and lead compounds, may be converted from the metal to a metal compound or from one metal compound to another in the environment, the metal cannot be destroyed. Thus, metals are obviously persistent in the environment in some form. The form of the metal that exists in the environment depends on its environmental fate. Environmental fate refers to the ultimate result of physical, chemical, and biological processes acting upon a metal or metal compound once it is released into the environment. The environmental fate determines the extent to which the metal or the metal from a metal compound will be available for exposure to organisms once released into the environment. The environmental fate of a metal or metal compound varies depending on the environmental conditions and the physical/chemical properties of the metal in question.

The information summarized in the proposed rule for the environmental fate of lead in each environmental medium represented the key elements influencing the transport, transformation, and bioavailability of lead in air, soil, water and sediments. This information, as well as a more extensive review of the existing data on the environmental fate of lead are contained in

The Environmental Fate of Lead and Lead Compounds

(Ref. 2) and in the references contained therein. Based on this information, EPA concluded that processes commonly observed in the environment can result in the release of available (ionic) lead where it can be bioaccumulated by organisms. These processes may occur in soil and aquatic environments with low pH and low levels of clay and organic matter. Under these conditions, the solubility of lead is enhanced and if there are no sorbing surfaces and colloids, lead ion can remain in solution for a sufficient period to be taken up by biota. Lead sorption to soil organic matter has been shown to be pH dependent. Decreasing pH can lead to increasing concentrations of lead in soil water; while increasing pH can lead to decreasing concentrations of lead in soil water.

The Agency's analysis of the environmental fate of lead and lead compounds showed that under many environmental conditions lead is available to express its toxicity and to bioaccumulate. In the EPCRA section 313 program, the issue of the environmental availability of metals from metal compounds is broader than just its implications for whether a chemical is a PBT. The issue of both the environmental availability and bioavailability has been addressed for EPCRA section 313 chemical assessments through EPA's policy and guidance concerning petitions to delist individual members of the metal compound categories listed under EPCRA section 313 (May 23, 1991, 56 FR 23703). This policy states that if the metal in a metal compound cannot become available as a result of biotic or abiotic processes then the metal will not be available to express its toxicity. If the intact metal compound is not toxic and the metal is not available from the metal compound then such a chemical is a potential candidate for delisting from the EPCRA section 313 list of toxic chemicals. EPA developed this petition policy specifically to address such circumstances.

B. What Aquatic Bioaccumulation Data was Presented for Lead and Lead Compounds?

Bioaccumulation is a general term that is used to describe the process by which organisms may accumulate chemical substances in their bodies. The term bioaccumulation refers to uptake of chemicals by organisms both directly from water and through their diet (Ref. 3). EPA has defined bioaccumulation as the net accumulation of a substance by an organism as a result of uptake from all environmental sources (60 FR 15366). The nondietary accumulation of chemicals in aquatic organisms is referred to as bioconcentration, and may be described as the process through which a chemical is distributed between the organism and environment based on the chemical's properties, environmental conditions, and biological factors such as an organism's ability to metabolize the chemical (Ref. 4). EPA has defined bioconcentration as the net accumulation of a substance by an aquatic organism as a result of uptake directly from the ambient water through gill membranes or other external body surfaces (60 FR 15366). A chemical's potential to bioaccumulate can be quantified by measuring or predicting the chemical's bioaccumulation factor (BAF). EPA has defined the BAF as the ratio of a substance's concentration in tissue of an aquatic organism to its 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 (60 FR 15366). A chemical's potential to bioaccumulate can also be quantified by measuring or predicting the chemical's bioconcentration factor (BCF). EPA has defined the BCF as the ratio of a substance's concentration in tissue of an aquatic organism to its concentration in the ambient water, in situations where the organism is exposed through water only and the ratio does not change substantially over time (60 FR 15366).

A review of the ecotoxicological literature indicates that bioconcentration values of lead and certain lead compounds ( lead salts) in aquatic plants and animals are often

above a bioconcentration/bioaccumulation factor of 1,000 and in some species at or greater than 5,000. Lead is bioaccumulated by aquatic organisms such as plants, bacteria, invertebrates, and fish. The principle form that is believed to be accumulated is divalent lead (i.e., lead in its plus 2 oxidation state (Pb +2 )). It has been shown that fish held in water at a pH of 6.0 accumulate three times as much lead as fish held in water at a pH of 7.5 (Ref. 5), thus as pH decreases the availability of divalent lead increases. Older organisms usually have the highest body burdens, and lead accumulates in bony tissues to the greatest extent.

The bioaccumulation data reviewed concerning the extent (magnitude) of lead bioaccumulation found to occur in many aquatic plants and animals and the lead bioconcentration factors (BCF) determined or measured from laboratory studies conducted for certain durations using BCF test methods, can be found in the bioaccumulation support document (Ref. 6). Concentrations of lead monitored in various organisms were determined by comparing concentrations in the environment (water) with concentrations measured in the organisms. In general, bioconcentration values for four freshwater invertebrate species ranged from 499 to 1,700 (Ref. 7). BCFs for two species of freshwater fish were much lower, 42 and 45. However, certain fish tissues have much higher BCF values, e.g., the BCF value for the intestinal lipids in rainbow trout were as high as 17,300. Freshwater phytoplankton and both marine and freshwater algae accumulate or concentrate lead to very high levels (e.g., greater than 10,000x). BCF values for marine bivalve organisms were as high as 4,985 for blue mussels. Eastern oysters also had BCF values greater than 1,000. These data indicate that many of the BCF values and measured environmental concentration factors for lead are above 1,000 with several species having BCF or observed concentration factors at or above 5,000. The references cited for blue mussels include a range of values, the upper end of which is essentially 5,000 (i.e., 4,985). There are also a few fish tissues that have BCFs greater than 10,000, though most of the available fish data are below 5,000.

C. What Human Bioaccumulation Data was Presented for Lead and Lead Compounds?

There is a great deal of information available on the bioaccumulation of lead in humans and the effects that such accumulation can have (Refs. 8, 9, 10, and 11). The bioaccumulation of lead in humans is well documented. Although lead has no known biological function in humans, it is readily absorbed through the gut and can be absorbed by inhalation and, to some extent by dermal contact. Absorption of lead can occur as a result of exposure to air-borne forms of lead, as well as ingestion or contact with contaminated soil and dust. Children and developing fetuses are known to absorb lead more readily than adults and to excrete it at a lower total rate. These findings are especially significant since young children are most susceptible to the adverse effects associated with lead exposure. Lead absorption varies from very low levels (e.g., 5%) up to essentially 100%. Lead absorption appears to be linked to particle size, the chemical composition, and other factors (Refs. 12 and 13). Long-lasting impacts on intelligence, motor control, hearing, and neurobehavioral development of children have been documented at levels of lead that are not associated with clinical intoxication and were once thought to be safe. An analysis of human blood-lead level data collected from the most recent publicly available National Health and Nutrition Examination Surveys (see Ref. 9), showed that approximately 4.4% of the nation's children aged 1-5 years have blood-lead concentrations at or above 10 micrograms per deciliter (mg/ dL), which is the current action level established by the Centers for Disease Control. While this is a significant improvement over the 88% of children who had blood lead levels above this threshold in 1976, before the phase-out of lead in gasoline, it is still cause for concern because it indicates that nearly 900,000 children aged 1-5 have unacceptably high blood-lead levels.

Once lead is absorbed in the body, it is primarily distributed to the blood, soft tissues (kidney, bone marrow, liver, and brain) and to the mineralizing tissue (bones and teeth). In one study it was shown that in adults, following a single dose of lead, one-half of the lead absorbed from the original exposure remained in the blood for approximately 25 days after exposure, in soft tissues for about 40 days, and in bone for more than 25 years (Ref. 14). Once in the bone, lead can re-enter the blood and soft tissues. Under certain circumstances, such as pregnancy and lactation, lead can more readily re-enter blood and soft tissues. Thus, accumulation of lead in bone can serve to maintain elevated blood lead levels years after exposure. The total amount of lead in long-term bone retention can approach 200 mg for adult males 60-70 years old (and even higher with occupational exposure). For adults, up to 94% of the total amount of lead in the body is contained in the bones and teeth but for children only about 73% is stored in their bones. While the increase in bone lead level across childhood may appear modest, the total accumulation rate is actually 80-fold. The increase is 80-fold because children undergo a 40-fold increase in skeletal mass. While lead absorption rates are influenced by several parameters, including route of exposure, chemical speciation, the physical/chemical characteristics of the lead and the exposure medium, as well as the age and physiological states of the exposed individual, there is substantial documentation that a significant amount of lead can be absorbed and accumulated in humans. Such absorbed and accumulated lead can cause significant deleterious health effects, particularly in children.

D. What Proposed Conclusions did EPA Reach from Its Proposal Review of the Available Data on Lead and Lead Compounds?

EPA's review of the available information on lead and lead compounds led EPA to conclude that lead and lead compounds are highly persistent and at the least, bioaccumulative. The persistence of lead in the environment is not in question since, as a metal, lead cannot be destroyed in the environment. With respect to whether lead or lead compounds released to the environment will result in lead that is available, the data indicate that under many environmental conditions lead does become available. The conclusion that lead is available in the environment is confirmed by the data on the bioaccumulation of lead in aquatic organisms and in humans as a result of environmental exposures. As for lead's bioaccumulation potential, lead has been shown to bioaccumulate in laboratory studies, has been found to bioaccumulate in organisms observed in the environment, and has been found to bioaccumulate in humans. EPA noted in its proposal that these data indicate that many of the BCF values and measured environmental concentration factors for lead are above 1,000 with several species having BCF or observed concentration factors at or above 5,000. The references cited for blue mussels include a range of values, the upper end of which is essentially 5,000 (i.e., 4,985). In addition, EPA explained that “[t]he bioaccumulation and persistence of lead in humans is well documented” and requested comment on how such

data should be regarded in classifying lead and lead compounds as highly bioaccumulative.

A high concern for the bioaccumulation potential for chemicals with BCF values above 1,000 is consistent with the discussion of BCF values in the proposed rule on PBT chemicals (January 5, 1999, 64 FR 688). In addition, there is considerable information on the accumulation of lead in humans, including children, who are the most susceptible to the toxic effects of lead. The data on lead's persistence and availability in the environment, the observed high bioaccumulation values in aquatic organisms, and lead's ability to accumulate in humans, provided the basis for EPA preliminarily concluding that lead and lead compounds are highly persistent and highly bioaccumulative.

E. What Changes to the Reporting Thresholds did EPA Propose for Lead and Lead Compounds?

In evaluating potential lower reporting thresholds for lead and lead compounds, EPA considered not only their persistence and bioaccumulation properties and the purposes of EPCRA section 313, but also the potential burden that might be imposed on the regulated community. Because PBT chemicals, including lead and lead compounds, persist and bioaccumulate in the environment, they have the potential to pose greater exposure to humans and the environment over a longer period of time. The nature of PBT chemicals, including lead and lead compounds, indicates that small quantities of such chemicals are of concern, which provides strong support for setting lower reporting thresholds than the current section 313 thresholds of 10,000 and 25,000 pounds. For determining how low reporting thresholds should be set for PBT chemicals, including lead and lead compounds, EPA adopted a two-tiered approach. Thus, EPA made a distinction between persistent bioaccumulative toxic chemicals and that subset of PBT chemicals that are highly persistent and highly bioaccumulative by setting lower reporting thresholds based on two levels of concern. As explained in the final PBT rule and in the proposed lead rule, this approach identifies as PBT chemicals those that are persistent (i.e., with half-lifes of at least 2 months) and those that are bioaccumulative (i.e., based on aquatic studies showing BAF/BCF values of at least 1,000 and/or human data showing evidence of bioaccumulation). Further, as also explained in the PBT rule and the proposed lead rule, highly PBT chemicals are identified as those that are highly persistent (i.e., with half-lifes of 6 months or greater) and those that are highly bioaccumulative (e.g., BAF/BCF values of 5,000 or greater). EPA preliminarily concluded that lead and lead compounds to be highly persistent and highly bioaccumulative toxic chemicals.

In determining the appropriate reporting thresholds to propose for lead and lead compounds, EPA started with the premise that low or very low reporting thresholds may be appropriate for these chemicals based on their persistence and bioaccumulation potentials only. EPA then considered the burden that would be imposed by lower reporting thresholds and the distribution of reporting across covered facilities. Using this approach and considering the factors described above and the purposes of EPCRA section 313, EPA proposed to lower the manufacture, process, and otherwise use thresholds to 10 pounds for lead and lead compounds. For purposes of section 313 reporting, threshold determinations for chemical categories, including lead compounds, are based on the total of all toxic chemicals in the category (see 40 CFR 372.25(d)).

F. What Other Reporting Issues Did EPA Consider for Lead and Lead Compounds?

1.

De minimis exemption

. In 1988, EPA promulgated the

de minimis

exemption because: (1) The Agency believed that facilities newly covered by EPCRA section 313 would have limited access to information regarding low concentrations of toxic chemicals in mixtures that are imported, processed, otherwise used or manufactured as impurities; (2) the Agency did not believe that these low concentrations would result in quantities that would significantly contribute to threshold determinations and release calculations at the facility (53 FR 4509, February 16, 1988); and (3) the exemption was consistent with information required by the Occupational Safety and Health Administration's (OSHA) Hazard Communication Standard (HCS). However, given that: (1) Covered facilities currently have several sources of information available to them regarding the concentration of PBT chemicals in mixtures; (2) even minimal releases of persistent bioaccumulative toxic chemicals may result in significant adverse effects and can reasonably be expected to significantly contribute to exceeding the proposed lower thresholds; and (3) the concentration levels chosen, in part, to be consistent with the OSHA HCS are inappropriately high for PBT chemicals, EPA's original rationale for the

de minimis

exemption does not apply to PBT chemicals. EPA therefore proposed to eliminate the

de minimis

exemption for lead and lead compounds based on their status as PBT chemicals. EPA did not propose, however, to modify the applicability of the

de minimis

exemption to the supplier notification requirements (40 CFR 372.45(d)(1)) because the Agency believed there was sufficient information available.

2.

Use of the Alternative threshold and Form A

. EPA stated its belief that use of the existing alternate threshold and reportable quantity for Form A would be inconsistent with the intent of expanded reporting for PBT chemicals such as lead and lead compounds. The general information provided in the Form A on the quantities of the chemical that the facility manages as waste is insufficient for conducting analyses on PBT chemicals and would be virtually useless for communities interested in assessing risk from releases and other waste management of PBT chemicals. EPA, therefore, proposed excluding lead and lead compounds from the alternate threshold of 1 million pounds.

3.

Proposed changes to the use of range reporting

. EPA stated its belief that use of ranges could misrepresent data accuracy for lead and lead compounds because the low or the high end range numbers may not really be that close to the estimated value, even taking into account any inherent error in reporting (i.e., errors in measurements and developing estimates). EPA believed this uncertainty would severely limit the applicability of release information where the majority of a facility's releases are within the amounts eligible for range reporting. Given EPA's belief that the large uncertainty that would be part of these data would severely limit their utility, EPA proposed to eliminate range reporting for lead and lead compounds.

4.

Proposed changes to the use of the half-pound rule and whole numbers

. EPA currently allows facilities to report whole numbers and to round releases of 0.5 pound or less to zero when reporting on EPCRA section 313 listed chemicals not designated as PBT chemicals in the October 29, 1999 final rule. EPA explained its concern that the combination of requiring the reporting of whole numbers and allowing rounding to zero would result in a significant number of facilities reporting their releases of lead and lead compounds as zero. EPA, therefore, proposed that all releases or other waste management quantities greater than

1/10

of a pound of lead and lead compounds be reported, provided that the appropriate activity threshold has been exceeded.

5.

Proposed exemption for the reporting of lead in certain alloys

. In the proposal, EPA proposed to defer making a final decision on lower reporting thresholds for lead contained in stainless steel, brass, and bronze alloys until the Agency could complete an ongoing scientific review of issues pertinent to the reporting of these types of alloys. This would result in no changes to the reporting requirements for lead contained in stainless steel, brass, and bronze alloys until EPA makes a final determination on whether there should be any changes to the reporting requirements for lead and other metals contained in these three types of alloys. EPA, therefore, proposed to include a qualifier to the listing for lead in 40 CFR 372.28. This qualifier would read “this lower threshold does not apply to lead when contained in a stainless steel, brass, or bronze alloy.”

V. Summary of the Final Rule

A. What Threshold Has EPA Established for Lead and Lead Compounds?

EPA is finalizing manufacture, process, and otherwise use thresholds of 100 pounds for lead and lead compounds, with the first reports at this lower threshold due on or before July 1, 2002, for the 2001 calendar year. This lower reporting threshold does not apply to lead contained in stainless steel, brass, and bronze alloys nor do any of the other changes discussed below in Unit V.B. However, lead contained in stainless steel, brass, and bronze alloys remains reportable under the 25,000 pound manufacture and process reporting threshold and the 10,000 pound otherwise use reporting threshold.

B. What Exemptions and Other Reporting Issues is EPA Addressing for Lead and Lead Compounds?

EPA is eliminating the

de minimis

exemption for lead and lead compounds. However, this action will not affect the applicability of the

de minimis

exemption to the supplier notification requirements (40 CFR 372.45(d)(1)). In today's action, EPA is also excluding lead and lead compounds from eligibility for the alternate threshold of 1 million pounds and eliminating range reporting for on-site releases and transfers off-site for further waste management for lead and lead compounds. This will not affect the applicability of the range reporting of the maximum amount on-site as required by EPCRA section 313(g). EPA proposed to require reporting of all releases and other waste management quantities greater than

1/10

of a pound of lead and lead compounds. Also, EPA proposed that releases and other waste management quantities would continue to be reported to two significant digits. In addition, EPA proposed that for quantities of 10 pounds or greater, only whole numbers would be required to be reported. After reviewing all the comments on this issue, EPA is providing additional guidance on the level of precision at which facilities should report their releases and other waste management quantities of lead and lead compounds. Facilities should still report releases and other waste management quantities greater than 0.1 pound provided the accuracy and the underlying data on which the estimate is based supports this level of precision. Rather than reporting in whole numbers and to two significant digits, if a facility's release or other waste management estimates support reporting an amount that is more precise than whole numbers and two significant digits, then the facility should report that more precise amount. The Agency believes that, particularly for PBT chemicals such as lead and lead compounds, facilities may be able to calculate their estimates of releases and other waste management quantities to

1/10

of a pound and believes that such guidance is consistent with the reporting requirements of sections 313(g) and (h).

VI. Summary of Public Comments and EPA Responses

A. How is EPA Responding to Comments Relating to Generic Issues?

EPA received numerous comments relating to the generic issues raised and resolved in the first rulemaking on PBT chemicals, published on October 29, 1999 (64 FR 58666); for example, whether the Agency should select lower thresholds based on a risk assessment. Some commenters merely reiterate comments raised in the previous rulemaking. Other commenters rephrase, in terms of lead and lead compounds, comments that have been previously submitted on these generic issues, without presenting additional information or concerns specific to lead and lead compounds.

In its proposal to lower the thresholds for lead and lead compounds, EPA explicitly limited its request for comments to issues specific to lead and lead compounds, such as whether lead and lead compounds meet the EPCRA section 313 persistence and bioaccumulation criteria articulated in the PBT rule and proposed lead rule, and whether lead and lead compounds present such unique technical or policy issues that they merit different treatment than that established for either the class of PBT chemicals or the subset of highly persistent and highly bioaccumulative toxic chemicals (see 64 FR 42224 and 58666). Notwithstanding that EPA extended the comment period on this rulemaking to allow for an additional 48 days following publication of the final PBT chemical rule, commenters failed to present issues or information that persuades the Agency to revisit the decisions made with respect to generic issues in the PBT chemical rule, or that provides any basis for treating lead and lead compounds separately from how the Agency generally approachs PBT chemicals within the EPCRA section 313 program.

To the extent that commenters provide comments on the generic issues that were specific to lead and lead compounds, these comments are addressed in this preamble and in the Response to Comments (RTC) document for this final rule (Ref. 1). For responses to those comments on the generic issues that were not specific to lead and lead compounds the reader is referred to the PBT chemical final rule (64 FR 58666) and the associated Response to Comments document (Ref. 15). The remainder of this Unit contains responses to major comments on the issues of the EPCRA section 313 reporting thresholds for lead and lead compounds, the technical information regarding the persistence and bioaccumulation potential of lead and lead compounds, and the alloys reporting limitation for lead. Responses to major comments on EPA's economics analysis (Ref. 16) and regulatory assessment determinations are contained in Units VII and IX respectively. Additional responses to comments not addressed in this preamble are contained in the RTC document for this final rule (Ref. 1).

B. What Comments did EPA Receive on its Statutory Authority to Lower Reporting Thresholds for Lead and Lead Compounds?

Several commenters allege that under EPA's interpretation of EPCRA section 313(f)(2), Congress did not provide an “intelligible principle” for determining whether or how much to lower a statutory threshold, thereby rendering this provision unconstitutional as an improperly broad delegation of legislative power. The commenters raise several points in support of this contention; several commenters cite

EPA's statement in the proposal that “Congress provided no prerequisites to the exercise of EPA's authority to lower [EPCRA section 313] thresholds” to demonstrate that EPA does not have the authority to lower the thresholds without violating the non-delegation doctrine. Other commenters support this allegation merely by reference to the fact that EPCRA section 313(f)(2) does not prohibit the Agency from establishing a threshold of “0.” Another commenter contends that the unconstitutional delegation of authority is even more striking than it was in section 109(b)(1) of the Clean Air Act, which at least provided the Agency with the direction to set standards “requisite to protect the public health” and “with an adequate margin of safety.” EPCRA, the commenter states, sets forth no standard for establishing reduced reporting thresholds. To support their assertions, several of these commenters specifically cite the decision in

American Trucking Association v. EPA

, 175 F.3d 1027 (D.C. Circuit, 1999)

cert. granted sub nom. Browner v. American Trucking Association

, 120 S.Ct 2003 (US May 22, 2000)(No. 99-1247).

EPA disagrees. As a preliminary matter, EPA disagrees with the interpretation of the non-delegation doctrine articulated in

American Trucking

, and has appealed that decision to the Supreme Court. Nonetheless, EPA believes that Congress has provided an “intelligible principle” sufficient for the delegation of authority contained in EPCRA section 313(f)(2).

The commenters appear to have fundamentally misunderstood EPA's explanation of its rationale for selecting the specific thresholds adopted in the final PBT chemical rule, and the implications these actions had for the selection of the thresholds for lead and lead compounds. As part of the discussion in the final PBT chemical rule, EPA noted that for several reasons, it was establishing “two sets of revised thresholds based on two classes of PBT chemicals,” and stated its intention that “the revised thresholds establish a set of categories that would be generally applicable to future designated PBT chemicals.” (64 FR 58689). Thus, the selection of the specific threshold for lead and lead compounds is governed by the analyses laid out in EPA's preamble to the final PBT chemical rule and in the proposed lead rule. See also EPA's rationale for the specific threshold chosen for lead and lead compounds,

infra

at Unit VI.E. Under this construct, taking into account the aquatic and human data available.

In the preamble to the final PBT chemical rule, and the associated Response to Comments Document (Ref. 15) , EPA described at length the process by which it distilled Congressional guidance from various sources, such as the language and legislative history of EPCRA sections 313(f)(2) and (h), to guide its exercise of discretion in lowering the thresholds. See (e.g., (64 FR 58687-692). Specifically, EPA explained:

EPA relied on the language of EPCRA sections 313(f)(2) and (h), and the legislative history, to elicit the following principles to guide its exercise of discretion in lowering the thresholds, and in selecting the specific thresholds: (1) The purposes of EPCRA section 313; (2) the “verifiable, historical data” that convinces EPA of the need to lower the thresholds; (3) the chemical properties shared by the members of the class of toxic chemicals for which EPA is lowering the thresholds (i.e., the degree of persistence and bioaccumulation); and (4) the reporting burden imposed by revised thresholds to the extent that such consideration would not deny the public significant information from a range of covered industry sectors. Further, EPA believes that in the language of EPCRA § 313, and its legislative history, Congress provided direction on the appropriate weight to allocate to each of these considerations in implementing EPCRA section 313(f)(2). These considerations underlay the entire process by which EPA determined the appropriate thresholds. But the Agency's choice of revised thresholds was governed, and ultimately constrained, by EPCRA section 313's overriding purpose, which is to provide government agencies, researchers, and local communities, with a comprehensive picture of toxic chemical releases and potential exposures to humans and ecosystems. Id. at 58687.

EPA also disagrees with the analyses on which the commenters rely to support their assertions that Congress provided no intelligible principle to guide EPA's delegated authority under EPCRA section 313(f)(2). Whether the legislative guidance offered sufficiently constrains the discretion delegated to the Agency under EPCRA section 313(f)(2) must be evaluated against the actual “power to roam” that this provision confers on EPA.

Michigan v. EPA

, 213 F.3d 663, 680-81 (D.C. Cir. 2000). As discussed in Unit II.A., as EPA interprets the requirements in section 313(f)(2), the standard operates as an effective constraint when the Agency increases the thresholds, but as a practical matter, cannot provide the same level of constraint when the Agency decreases the thresholds. However, as previously explained, EPA relied on this standard to elicit factors to guide its exercise of discretion. See, 64 FR 58687-692.

But the mere fact that Congress provided neither explicit prerequisites in section 313(f)(2) to the Agency's determination that a lower threshold is warranted, nor a standard whose plain language effectively constrains EPA's discretion in selecting the appropriate lower threshold, does not necessarily render this provision unconstitutional. The issue is whether Congress granted the Agency too much discretion to

modify

the statutory thresholds—not merely whether Congress provided a standard to significantly constrain the Agency's discretion in lowering the thresholds. See

Michigan v. EPA

, 213 F.3d at 680;

International Union v. OSHA

, 37 F.3d 665 (D.C. Cir. 1994). Examination of the former issue demonstrates that in section 313(f)(2), EPA's “power to roam” is relatively narrow.

In section 313(f), Congress established thresholds as a baseline, and delegated authority to EPA to modify them provided that the “revised thresholds shall obtain reporting on a substantial majority of total releases of the chemical at all facilities subject to the requirements of this subsection.” As previously explained, EPA interprets this to require that any revised threshold obtain reporting on a substantial majority of the total releases reported by facilities reporting under the existing, baseline thresholds. See, Unit II.A.

supra

, and 64 FR 58673-676. This standard effectively constrains EPA's ability to increase the thresholds, and thereby deprive government agencies, researchers, and local communities of information that would provide them with a comprehensive picture of toxic chemical releases and potential exposures to humans and ecosystems, contrary to EPCRA section 313's overriding purpose. The discretion exercised in this rule is EPA's discretion to establish thresholds between 0 and 10,000 pounds or 25,000 pounds; this can hardly be characterized as an “immense power to roam.”

Moreover, the impact of any revised threshold is distinctly limited, which courts have recognized as a relevant factor in evaluating the degree of authority that Congress delegates to an Agency. See, e.g.,

Michigan

, 2000 WL 180,650 (“a mass of cases in courts had upheld delegations of effectively standardless discretion, and distinguished them precisely on the ground of the narrower scope within which the agencies could deploy that discretion”);

American Trucking

, 175

F.3d at 1037 (“The standards in question affect the whole economy, requiring a more precise delegation than would otherwise be the case” (citations omitted)). Here, that means within the context of all of the other prerequisites Congress established for TRI reporting, and of the other relevant statutory provisions constraining the Agency's ability to modify those requirements. Irrespective of the modified threshold, a facility must still employ more than ten full-time employees; its primary SIC code must fall within one of the listed SIC codes; and it must be manufacturing, processing, or otherwise using one (or more) of the currently listed chemicals. 42 U.S.C. § 11023 (b). And far from granting EPA unfettered discretion to expand these requirements, Congress selectively granted EPA carefully qualified authority to adjust individual parameters. For example, section 313(l) explicitly limits the Agency's authority to modify the reporting frequency, “. . . but the Administrator may not modify the frequency to be any more often than annually.” Similarly, Congress included no authority to amend the generally applicable employee threshold; thus facilities with fewer than ten employees are not subject to reporting under subsection 313(b)(1). In section 313(g)(2), Congress also specifically restricted the Agency's ability to require industry to collect data to report under TRI: “Nothing in [EPCRA section 313] requires the monitoring or measurement of the quantities, concentration, or frequency of any toxic chemical released into the environment . . .” Accordingly, the scope within which EPA may deploy its discretion under EPCRA section 313(f)(2) is fairly narrow, and its impact limited.

In light of the above, EPA does not believe that the mere fact that the Agency is authorized to potentially select a threshold of “0,” necessarily renders section 313(f)(2) unconstitutional. The issue underlying the non-delegation doctrine, as the DC Circuit has explained is “to make sure that the regulatory principles as applied have their origin in a judgement of the legislature,” not whether Congress authorized the Agency to establish extremely low thresholds.

International Union

v.

OSHA

, 37 F.3d at 669 (citations omitted). Nor does the fact that Congress did not require the Agency to make specific findings to determine it was appropriate to increase or decrease section 313 reporting thresholds, necessarily demonstrate that Congress failed to provide the Agency with adequate guidance in delegating its authority under section 313(f)(2).

One commenter further alleged that the Agency has failed to identify an intelligible principle “to channel its application of these factors,” quoting,

American Trucking Association v. EPA

. Another commenter asserts that EPA's reliance on the general purposes of EPCRA is insufficient, stating that “general purposes or factors cannot substitute for the constitutionally required “intelligible principle” by which to identify a stopping point” when setting levels or thresholds.

As noted above, the Supreme Court has granted EPA's request to review

American Trucking

. Nonetheless, EPA disagrees that EPCRA section 313(f)(2) falls afoul of the non-delegation doctrine, even as interpreted and applied in that case. As summarized above, in the preamble to the final PBT chemical rule, EPA identified and explained its application of the “intelligible principle” that Congress provided along with the delegation of authority in EPCRA section 313(f)(2). See, 64 FR 58687-692.

EPA also disagrees that its reliance on EPCRA section 313's general purposes to discern EPCRA section 313's overriding purpose, and thereby its intelligible principle, is insufficient. The DC Circuit upheld a broad delegation of legislative authority to OSHA based on the Agency's demonstration of legislative guidance found in the Act's “overriding purposes.” There, the Court noted

Were the six itemized criteria the full statement of OSHA's interpretation of its statutory mandate, we might have to vacate the rule, because the agency might still have too much freedom to “roam between the rigor of section 6(b)(5) standards and the laxity of unidentified alternatives. International Union I, 938 F.2d at 1317.

But OSHA has gone on to infer from various sections—that the Act's “overriding purpose” is “to provide a high degree of employee protection.”

58 FR 16, 614/3-15/1. Thus the Agency reads the Act to require it, once it has identified a “significant” safety risk to enact a safety standard that provides “a high degree of worker protection.”Id. at 16, 615/1. It is not permitted to “do nothing at all”, as we had earlier suggested. Id. (quoting International Union I, 938 F.2d at 1317).

Rather, OSHA reads the Act to permit it to deviate only modestly from the stringency required by section 6(b)(5) for health standards. Accordingly, as construed by OSHA, the Act guides its choice of safety standards enough to satisfy the demands of the nondelegation doctrine

. (citations omitted).

International Union v. OSHA

, 37 F.3d at 669 (emphasis added).

The Court also explained that the underlying purpose of non-delegation doctrine is “to make sure that the regulatory principles as applied have their origin in a judgement of the legislature.” Id. (citations omitted). EPA believes that its application of EPCRA section 313(f)(2) in this rule, as well as in the PBT rule, similarly satisfy the demands of the nondelegation doctrine.

C. What Science Issues Were Raised by Commenters on the Persistence and Bioaccumulation Criteria?

Several commenters contend that the criteria articulated in the PBT chemical rule to characterize the persistence and bioaccumulation of toxic chemicals should not be applied to metals because the development of the persistence and bioaccumulation criteria (as discussed in the PBT chemical rulemaking, see 64 FR 688-729) was based largely on data pertaining to organic substances. Thus they contend it is inappropriate to use these criteria to determine whether inorganic substances, including inorganic metal compounds, should be classified as PBT chemicals.

The Agency disagrees with the commenters' statement that the PBT rule framework developed by EPA to assess the persistence and bioaccumulation of EPCRA section 313 listed toxic chemicals was designed only for organic substances and is being incorrectly applied to metals. The development of EPA's framework to assess persistence and bioaccumulation is described in detail in the PBT chemical rulemaking (see 64 FR 688-729) and in the proposed lead rule. This framework was not developed to assess only whether organic chemicals are persistent and/or bioaccumulative, but to assess whether

any

chemical substance is persistent and/or bioaccumulative, including metals and metal compounds. EPA notes that the public had the opportunity to comment on the applicability of the PBT rule criteria to metals in the PBT chemical rulemaking. Furthermore, in the PBT chemical rulemaking, the Agency applied these criteria to mercury and mercury compounds—a metal and metal compounds category. EPA also provided notice in the proposed PBT chemical rulemaking that it was continuing to evaluate the bioaccumulation data for lead and lead compounds, and for cobalt and cobalt compounds—also metals (64 FR 717). EPA made clear the PBT rule criteria were developed to apply to metals and metal compounds, as well as organic compounds and, in fact, has applied the criteria to metals and metal compounds in a previous notice and comment rulemaking. With respect to the half-life and BCF/BAF criteria, scientifically these criteria are quite applicable to metals. Finally in the

lead proposed rule, EPA identified an additional factor for use in determining whether a chemical is, at the least, bioaccumlative. EPA explained that there is clear and convincing evidence that lead is bioaccumulative in humans. However, EPA requested comment on how such human data should be considered in determining whether a chemical should be classified in that subset of PBT chemicals that are highly bioaccumulative. Commenters argue that the human data should not be used to classify lead as bioaccumulative because the quantities of lead that might be reported, they believe, would not reduce human exposures to lead that are of concern. As explained elsewhere, EPA does not believe that human data showing the bioaccumulation nature of lead in humans should be ignored in any assessment of lead's bioaccumulation potential simply on the theory that the level of lead to which humans are exposed and the levels observed in humans may not correlate to the additional information on land release collected under this rule.

Persistence, bioaccumulation, and toxicity are three distinct, independent characteristics. Although in the PBT chemical rulemaking the experimental evidence used to derive the environmental half-life, BAF and BCF criteria were obtained largely from studies that involved organic substances, this does not preclude the application of these criteria to inorganic substances such as metals and metal compounds (including lead and lead compounds). The basis for the concern and reason for lowering thresholds is based on the ability of the chemical, whether it is an organic chemical or a metal compound, to persist and bioaccumulate. The Agency believes that these criteria should and must be applicable to

all

chemical substances, including metals and metal compounds. EPA provided a detailed response to the issue of metals as PBT chemicals in the PBT chemical rulemaking. Persistence and bioaccumulation are not dependent upon whether a substance contains carbon (i.e., is organic). Substances that are inorganic can persist and bioaccumulate. The underlying molecular properties that determine whether a substance can persist and bioaccumulate are fundamentally the same for organic chemicals as they are for inorganic chemicals, including metals and metal compounds. These properties, as with most chemical and biological properties of a substance, are more dependent on the electronic and steric characteristics of the atoms comprising a substance, the specific arrangement of the atoms within the substance's molecular structure and, with regard to bioaccumulation, the pharmacokinetics of the substance within the exposed organism and the sensitivity of the organism to the substance.

In addition, it is scientifically valid to establish generic criteria that are applicable to all substances provided that the endpoint or purpose for which the criteria are being established provides a common thread that is not dependent upon the unique elements comprising any given substance. For example, it would be legitimate to establish a category based on a type of arsenic toxicity and include within that category any substance that contains arsenic and exhibits that toxicity regardless of whether individual substances are organic or inorganic. In fact, it is common practice for scientific organizations and regulatory agencies to use generic criteria of this type. One example is the criteria established by the National Toxicology Program (NTP) for characterizing chemical carcinogens. The NTP is required by law to establish a list of all substances which either are known to cause cancer in humans, or may reasonably be anticipated to cause cancer in humans. A criterion used by the NTP to characterize chemicals as known or possible human carcinogens include, among others, tumor incidences in humans or experimental animals. While the vast majority of substances reviewed and tested by the NTP for carcinogenicity are organic substances, and the criterion established by NTP was based largely from toxicological observations pertaining to organic substances, the criterion used by the NTP is the same for inorganic substances as it is for organic substances. The NTP does not use different criteria when evaluating inorganic substances. This is because the ability of a substance to cause cancer is not dependent upon whether the substance is organic. In fact, NTP's current list of substances that are known to be human carcinogens contains both inorganic (including metallic) and organic substances. The carcinogenicity of all of these substances were characterized by the same generic criterion. A detailed discussion of the criteria used by the NTP is available (Ref. 17).

1.

What comments did EPA receive on the persistence of metals and metal compounds

? EPA defines a chemical's persistence as the length of time the chemical can exist in the environment before being destroyed by natural processes. Numerous commenters suggested that EPA adopt a different definition of persistence for metals and metal compounds. They assert that the definition of persistence as applied to metals and metal compounds should include the transformation of individual metal compounds in the environment. As discussed in detail in the following response to comments on this issue, EPA believes that these factors are irrelevant to the persistence of metals and metal compounds in the environment. The factors that the commenters contend should be considered are those which address the conversion of one metal compound to another, which is irrelevant in determining whether metal compounds are persistent. While these are factors which control the transformation of one metal compound to another compound of the same metal, they are not factors which result in the destruction of the metal. There are no environmental factors which can or will result in the destruction of the metal.

Some commenters disagree with EPA's definition of persistence. They contend that the definition of persistence should be based on the availability of the metal in various environments and the length of time the metal is retained in an organism. One of these commenters stated that “persistence is the length of time an element or compound is available to and/or is retained in an organism or an ecological community, and that the mobility of metals [such as lead] deposited in soils or aquatic sediments becomes an important question when discussing persistence, since they are not persistent in biota unless they reach those environmental compartments and are cleared more slowly than they accumulate.”

EPA disagrees with the commenter's definition of persistence. In the PBT chemical rulemaking (64 FR 58666), EPA adopted a policy for use in classifying a toxic chemical as persistent under EPCRA section 313. In the proposed rule to lower the reporting thresholds of lead and lead compounds (64 FR 42222), EPA used this same policy to determine whether lead and lead compounds are persistent. Most of these comments address the issue of persistence generically rather than specifically to lead and lead compounds. EPA responded to these generic issues in the PBT chemical rulemaking (64 FR 58676) and in sections 2a-f of the associated Response to Comments document (Ref. 15). EPA is discussing these issues here as background for the individual issues specific to lead and lead compounds in order to assist in understanding EPA's responses. Persistence is the length of

time a chemical can exist in the environment before being destroyed by natural processes (64 FR 698 and 64 FR 42227). The environmental media for which persistence is measured or estimated include air, water, soil, and sediment. It is important to distinguish between persistence in a single medium (air, water, soil or sediment) and overall environmental persistence. Persistence in an individual medium is controlled by transport of the chemical to other media. Persistence in the environment as a whole, however, is a distinct concept. It is based on observations that the environment behaves as a set of interconnected media, and that a chemical substance released to the environment will become distributed in these media in accordance with the chemical's intrinsic properties and reactivity. For overall persistence, only irreversible transformation contributes to net loss of a chemical substance. With regard to metals, although metals and metal compounds, such as lead and lead compounds, may be converted from the metal to a metal compound or from one metal compound to another in the environment, the metal itself cannot be destroyed. A metal by its very nature cannot be destroyed and, therefore, is persistent in the environment as the metal or a metal compound.

The primary purpose of the persistence criterion is to establish how long a chemical substance will remain in the environment. The greater the length of time a substance persists in the environment, the greater is the potential for all forms of life to be exposed to the substance. Persistence is not limited to the duration of time a chemical is present in an organism and EPA does not believe it would be appropriate to incorporate this concept into its definition of persistence. It should be noted that, unlike the commenter's definition of persistence, EPA's definition of persistence does not specifically address the longevity of a substance in an organism. Persistence of a substance in the environment as a whole, or even in a particular environmental medium, is fundamentally unrelated to the substance's biological persistence (i.e., length of time a chemical exists in an organism before being destroyed or excreted). Although there are a few factors (physicochemical factors; e.g., water solubility, reactivity) that have a similar influence on environmental persistence as they do on the biological persistence of a substance, there are a number of other factors that influence biological persistence but not environmental persistence. These other factors are organism specific, and are related to the anatomical and physiological characteristics of the organism. The Agency believes its environmental persistence criterion should not be extended to include biological persistence because the factors that influence the two persistence types are largely unrelated. Biological persistence in a given organism does not provide any information as to how long a substance will remain in the environment, and therefore is not relevant to the definition of persistence for EPCRA section 313.

One commenter claims that there is a serious flaw in the Agency's reasoning in characterizing all elements, including metals, as being persistent. Specifically, this commenter claims that this reasoning implies that because elements are non-destructible, then any compounds that contain a particular element is also non-destructible. The commenter acknowledges that EPA makes the statement in the proposed lead rule that “specific metal compounds may or may not be persistent, depending on the form of the metal and environmental conditions, but the elemental metal itself obviously meets the definition of persistence.” The commenter claims that this statement begs the questions as to why EPA is not evaluating specific metal compounds when the Agency acknowledges that metal compounds differ in their “persistence” and also differ substantially with respect to toxicity and bioaccumulative potential. The commenter states that the above quoted statement could just as easily read “. . . specific

carbon

compounds may or may not be persistent, depending on the form of

carbon

and environmental conditions, but the elemental

carbon

itself obviously meets the definition of persistence.” The commenter asserts that, according to EPA, this would mean that all organic compounds are persistent because they contain carbon and carbon is persistent. The commenter states that the Agency does not adopt such reasoning regarding elemental carbon because it would render the PBT chemical assessment methodology useless as an assessment tool. The commenter recommends that the Agency not apply the persistence assessment methodology to metals for the same reasons.

Another commenter believes that EPA's criteria for persistence as it applies to characterizing the persistence of metals is unfair. Specifically, this commenter interprets EPA's persistence assessment methodology as saying “. . . since any metal is persistent in the environment by definition, every compound of that metal is evaluated and regulated by EPA like the parent metal, even if there are no data on that compound's persistence, even if the persistence in the environmental medium of its concern is very short, and even if that compound's bioavailability is insignificant.”

The Agency believes that both of these commenters have misinterpreted the PBT assessment methodology EPA applied to lead and lead compounds.

With respect to the commenter who questioned why EPA is not evaluating the persistence of compounds individually, EPA disagrees that it is either scientifically required, or necessary for purposes of EPCRA section 313, to evaluate the persistence of each lead compound individually. lead compounds are listed under EPCRA section 313 as a category; this means that all of the individual chemical compounds share common chemical characteristics, such that it is scientifically reasonable to conclude that lead compounds exhibit common toxicological properties/exhibit similar toxicity. For lead compounds, as for all metal compounds listed in an EPCRA section 313 metals category, the relevant common chemical property is the metal, because the toxic constituent is the metal itself, and this is what defines the category. Thus, in evaluating the persistence of lead compounds as an EPCRA section 313 chemical category, the relevant issue for purposes of EPCRA section 313 is the persistence of lead rather than the persistence of the other chemical constituents of the compounds in the category.

Similarly, EPA believes that this commenter's analogy to carbon and organic compounds is misguided. Organic compounds differ significantly from metal compounds in that the presence of carbon in a compound is not a controlling feature in the way that a metal contained in a metal compound is controlling. For example inorganic arsenic compounds are classified as known human carcinogens (Ref. 18). The toxicity is specific to the fact that the compounds contain arsenic and not to the other parts of the arsenic compounds. This is not the case with all groups of carbon compounds. For example, classes of organic chemicals that contain oxygen such as ketones, alcohols, ethers, and carboxylic acids exhibit significantly different physical and chemical properties and toxic effects. This is due to the differing arrangement of the carbon and oxygen within the compound. Even chemicals within the same class of organic chemicals, e.g., ketones, may not exhibit the same toxicity or similar physical

chemical properties. Further, while one arsenic compound will be converted in the environment or

in vivo

, it will not be converted into a substance that does not contain arsenic. In the environment or

in vivo

degradation of one member of a group of organic chemicals, e.g., ketones, carboxylic acids, will not consistently be converted into another chemical of the same class. They will often be converted into a different class of organic chemical.

Thus, while the Agency agrees that elemental carbon is persistent, the Agency would not conclude that all organic substances are persistent simply because they contain carbon. This is because the toxic effects of organic compounds are attributable to the structure of the compounds and

not

the carbon contained in the compounds. Thus EPA would not list a chemical category consisting of carbon and all carbon containing compounds, nor would it make a determination using the PBT assessment methodology that such compounds are PBT chemicals because they contain carbon. The same is true for any other element that is not toxic.

This approach is consistent with the Agency's approach to listing chemical categories, where, in the absence of data on a particular member of the category, EPA adds a chemical category, such as a metal compound category, based on their common chemical characteristics, and without demonstrating separately that each individual member of the category meets the section 313(d)(2) criteria. The D.C. Circuit specifically upheld this approach with respect to listing categories, finding that EPA's action was reasonable (

Troy v. Browner

, 120 F.3d 277, 288-89 (D.C. Cir. 1997).

In addition, the commenters imply that in using the PBT rule assessment methodology EPA would conclude that all metals and their compounds are persistent and bioaccumulative, and therefore the Agency would require that all metals and their compounds that are listed on the EPCRA section 313 list of toxic chemicals have reduced reporting thresholds. The Agency would like to emphasize that while all metals persist, many metals and their compounds would not be characterized by EPA as bioaccumulative and toxic. For a listed toxic chemical to be considered a PBT chemical, the toxic chemical must be sufficiently persistent and sufficiently bioaccumulative.

Several commenters disagree with the Agency's rationale for characterizing all metals as being persistent, and believe that the issue of persistence has little or no relevance to metals.

The Agency disagrees with the commenters' statement that the issue of persistence has little or no relevance to metals. EPA believes that persistence is relevant to the hazard potential of metals such as lead for the same reason persistence is relevant to the hazard potential of organic chemicals: for a chemical that persists in the environment, there is a greater potential for exposure and, therefore, a greater potential for the chemical to cause toxicity in an exposed organism or individual. However, in this rulemaking the Agency did not rely on the property of persistence by itself in lowering reporting thresholds for lead and lead compounds, nor does persistence alone necessarily mean that a substance is or can be a hazard to human health and the environment. As stated above, to be classified as a PBT chemical, a chemical must: (1) Be an EPCRA section 313 listed toxic chemical; (2) be sufficiently persistent; and (3) be sufficiently bioaccumulative. In this rulemaking EPA is addressing lead and lead compounds which are EPCRA section 313 listed toxic chemicals and is also considering the bioaccumulation potential of these chemicals.

One of the commenters believes that metals do not necessarily persist, and that the definition of persistence in relation to metals should be qualified to mean how long a metal can remain in a particular form or species (e.g., oxidation state). This commenter also recommends that the Agency should examine data pertaining to certain properties of metals to assess persistence in accordance with this definition, and to allow for the identification of those metals and metal species which are the most/least resistant to change and which are the most or least bioavailable. The properties raised by the commenters include: transformation/dissolution, oxidation, corrosion, sulfide binding, and first hydrolysis constant.

EPA agrees with the commenter's statement that metals, including lead, can exist as different species and compounds. These different species pertain to the oxidation states or, more specifically, the number of electrons missing from the outer orbital of the metal atom. Lead, for example, can exist in a neutral species, Pb

0

(no electrons are missing from the outer electron orbital of the lead nucleus), or as lead compounds in one of two oxidation states: Pb

+2

or Pb

+4

(2 and 4 electrons are missing from the outer electron orbital, respectively). As stated in the proposed rule, these species can convert from one to another under certain, commonly encountered environmental conditions. See also Unit VI.C.5. of this preamble. While there may be a conversion from one lead compound to another lead compound or to metallic lead, or from metallic lead to a lead compound (either in the Pb

+2

or Pb

+4

oxidation states), there is no possible conversion either in the environment or

in vivo

that will convert (or degrade) metallic lead or any lead compound into a substance that does not contain lead. Any conversion will always result in the presence of lead or a compound that contains lead. Conversion of a metal atom from one oxidation state to another does not change the number of protons in the nucleus of the atom and, therefore, does not change the metal into another metal or element. In the case of lead, each species of lead (Pb

0

, Pb

+2

, and Pb

+4

)

is still lead

because each contain the same number of protons (82) within their nuclei (See Refs. 19 and 20).

EPA disagrees with the commenter's assertion that the Agency consider transformation/dissolution, oxidation, corrosion, sulfide binding, and first hydrolysis constant in determining whether metal compounds are persistent. These are factors which address the conversion of one metal compound to another, which is irrelevant in determining whether metal compounds are persistent. While these are factors which control the transformation of one metal compound to another compound of the same metal, they are not factors which result in the destruction of the metal. There are no environmental factors which can or will result in the destruction of the metal. Therefore, EPA believes that the commenter's definition of persistence is not an appropriate alternative to EPA's definition.

One commenter who agrees with EPA's definition of persistence and, in particular the Agency's characterization of lead as being persistent states that the persistency of lead poses a significant threat to human health and the environment because this property allows lead to remain in the environment without being broken down by natural processes. This commenter disagrees with other commenters who claim that metals are not persistent or that persistence of toxic metals should not be of concern. This commenter believes that persistence enables a substance like lead to travel through ecosystems and through different media and, as such, threatens human health and the environment far beyond the geographic vicinity of the source from which it has been released.

The Agency agrees with the commenter's statement that lead is persistent. The Agency also agrees that

the persistence property of a substance contributes to the ability of the substance to be distributed through ecosystems and through different media to areas beyond the geographic vicinity from where the substance entered the environment. The property of persistence, however, pertains to longevity of a substance, and does not bestow an ability for the substance to partition throughout environmental media. However, the opportunity for exposure to a substance that is capable of partitioning throughout environmental media may be greater if the substance is also persistent, since the substance will remain in the environment for a longer period than a substance that is not persistent

2.

What comments did EPA receive on the availability and bioavailability of metal compounds

? Commenters suggest that EPA consider environmental availability (which they term “bioavailability”) in lieu of bioaccumulation. Many of these commenters assert that unless a metal compound is readily available in the environment, it will not be bioavailable or bioaccumulate. Some attempt to take a risk-based approach to metals and metal compounds in the environment by arguing that when environmental availability is considered, metals and metal compounds will not be present at levels high enough to cause adverse effects.

As discussed in detail below, the level of environmental availability or bioavailability is not a surrogate for bioaccumulation. Even metal compounds that have limited availability or bioavailability can bioaccumulate. The extent of environmental availability or bioavailability will not affect whether bioaccumulation will occur. For example, lead from a sparing soluble compound and lead from a readily soluble compound will both bioaccumulate. This is in contrast to the commenters' implication that only the lead from the readily soluble lead compound will bioaccumulate. Further as discussed below, the presence of a soluble metal compound is not the only factor, or in many cases the determining factor, that controls the potential for the metal compound to bioaccumulate. A metal compound may undergo various transformations in the environment resulting in a different metal compound which has a much higher availability and/or bioavailability. While metals and metal compounds need to be environmentally available and/or bioavailable as a prerequisite to bioaccumulation, there is not a quantitative relationship between environmental availability and/or bioavailability and the degree of bioaccumulation. Therefore, EPA believes that availability and bioavailability are not appropriate substitutes for bioaccumulation.

Further, requiring a particular level environmental availability would effectively be establishing a risk-based approach to lowering thresholds which EPA believes is inappropriate for the following reasons. The availability of lead in the environment will vary depending upon environmental conditions. Choosing one level of environmental availability and applying that individually to each metal compound is neither practical nor scientifically supportable because: (1) As discussed above environmental availability is not necessarily reflective of bioavailability; and (2) the environmental availability of a metal compound depends upon local environmental conditions. There is no “best” or adequately representative set of national environmental conditions. Further, the TRI program is primarily a hazard based program. Risks that may be acceptable at the national level may not be acceptable at a regional or local level.

EPA considers availability in the environment and bioavailability for metal and metal compounds for purposes of bioaccumulation only to determine whether it is impossible for the metal and metal compounds to bioaccumulate, i.e., a compound that is both environmentally and biologically inert cannot bioaccumulate. EPA believes that there are data that indicate that lead and lead compounds are available in the environment, are bioavailable, and bioaccumulate, e.g., data in humans and fish advisories. However, several commenters contended at public meetings on EPA's PBT chemical rulemaking that metals and metal compounds, such as lead and lead compounds, are not available in the environment and thus, cannot bioaccumulate. To address these comments, EPA chose to conduct an environmental fate assessment to describe the environmental availability of lead and lead compounds. Qualitative environmental fate assessments are generally part of a hazard assessment for a chemical. The qualitative environmental fate assessment for lead and lead compounds, however, was not developed, nor was it intended, to be part of an exposure assessment or risk assessment.

Several commenters claim that EPA should consider bioavailability in its assessment of metals and metal compounds, such as lead and lead compounds. These commenters contend that not all metal compounds and lead compounds in particular are bioavailable. According to the commenters, unless a compound is in a form that is bioavailable, it will present little risk to human health and the environment. One commenter made the following statement:

Because of metals' natural persistence, the weight of scientific opinion holds that bioavailability is a more appropriate criterion for assessing the environmental and health hazards associated with metals. While toxicity is obviously a relevant measure for assessing the hazard posed by a substance, the substance must be available for uptake [bioavailable] before it can exhibit an adverse effect. Bioavailability varies significantly among different species of metals, including lead compounds, and also is influenced by environmental media. Bioavailability can only occur if soluble metal compounds are released. Thus, the rate at which metals transform to soluble/bioavailable species is critical for hazard identification. Simply stated, the natural persistence of metals with toxic properties poses no special hazard if those metals generally are present in environmental media in forms that cannot be taken up by plants and animals.

Other commenters expressed similar views. These commenters believe that the availability of lead from lead compounds differs among lead compounds, and that lead is unavailable from certain lead compounds. Therefore, in the opinion of the commenters, lead compounds from which lead is not available and/or bioavailable cannot be PBT chemicals, and should not be included in this rulemaking.

The Agency disagrees with the commenters assertions that: (1) EPA did not consider bioavailability of lead in its assessment of lead and lead compounds as bioaccumulative substances; and (2) that bioavailability is only possible for released soluble metal compounds.

The basis for the Agency's disagreement with these comments concerns the commenters use of the terms “availability” and “bioavailability”, which differs significantly from EPA's definition of these terms. The commenters are using the term bioavailability interchangeably with availability, when in fact these two terms have totally different meanings and cannot be used interchangeably. In addition, the commenters have incorrectly concluded that: (1) If lead is not available in the environment, it is not bioavailable and will not bioaccumulate or cause toxicity; (2) lead is only bioavailable when in its ionic oxidation state; and (3) only those lead compounds that are water soluble as released are bioavailable. To respond to

these comments, the Agency needs to first clarify the distinction between “availability” of a metal, and “bioavailability” of a metal or metal compound, and the factors that influence availability and bioavailability of a metal or metal compound.

Availability

of a metal is the extent to which a metal, in either its neutral (MG

0

) or ionic (MG

+x

) oxidation state, can reach a state of atomic disaggregation. Inorganic metal compounds that are water soluble will completely dissociate in aqueous media, liberating the metal in its ionic oxidation state. In aqueous solution the metal atoms of the molecules of these substances are completely disaggregated from the rest of their molecular constituents. In this disaggregated state the metal is completely available. Water solubility is not a prerequisite, however, for a metal to become available from a metal compound. In the environment a metal can become available from organometallic substances or inorganic metal compounds that are poorly soluble in water, by undergoing environmental transformations that cause the metal atoms to dissagregate and become available. Environmental transformations that cause metals to become available are summarized below, and discussed in greater detail in Unit V.A. of the proposed lead rule (64 FR 42227-42228), and in

The Environmental Fate of Lead and Lead Compounds

(Ref. 2).

The extent to which a metal can become available from a metal compound in environmental media is dependent upon: (1) The physicochemical properties of the metal and the metal compound; (2) the structural characteristics of the metal compound; and (3) environmental factors, including, but not limited to: presence of aerobic or anaerobic bacteria, pH, moisture content, and organic matter content of soil or sediments. Some or all of these environmental factors can vary between specific terrestrial or aquatic environments. For different compounds that contain the same metal, the relative availability of the metal from each compound can vary within the same terrestrial or aquatic environment. It is also true that the availability of a metal from the same metal compound can vary between specific terrestrial or aquatic environments. Some metal compounds are more susceptible to environmental transformations and subsequent release of the metal than are other metal compounds.

Bioavailability

is the extent to which a substance is absorbed by an organism, and distributed to an area(s) within the organism. This is important because the substance can then exert a toxic effect or accumulate. As with availability, the physicochemical and structural characteristics of a substance play an important role in determining whether the substance is bioavailable and the extent to which it is bioavailable. Unlike availability, however, whether a substance is bioavailable and the extent to which it is bioavailable in a given organism also depends upon the anatomy and physiology of the organism, the route of exposure, and the pharmacokinetics of the substance in the organism (i.e., the extent to which the substance is or can be absorbed by the organism from the exposure site, its distribution and metabolism within the organism, and its excretion from the organism). It is important to stress that bioavailability does not by itself mean that a substance is a hazard to human health or the environment. A substance that has 100% bioavailability does not pose a hazard to human health or the environment if it is not intrinsically toxic. Conversely, for substances that are intrinsically toxic it is not necessary for the substance to be 100% bioavailable to cause toxicity. Depending upon the extent of exposure, toxic potency, and the nature of the toxic effect, even substances that have low bioavailability can still pose a hazard to human health or the environment. Similarly, a substance does not have to have 100% bioavailability in order for it to bioaccumulate. For some compounds, even very limited bioavailability (that is a very small percentage is bioavailable) can result in concern if it is bioaccumulated. Lead and lead compounds are one example. Polychlorinated biphenyls (PCBs) are another (64 FR 706).

Absorption of a substance is a critical component of its bioavailability. Absorption is the movement of a chemical substance from its site of exposure on a terrestrial or aquatic life form into its systemic circulation (bloodstream) or, in the case of unicellular organisms such as algae, inside the cell comprising the organism. In any case, absorption of a substance from any exposure site involves its passage across the biological membranes that compose the exposure site. Chemicals can cross a cell membrane by several mechanisms. These are: (1) Passive permeation (diffusion) through the membrane; (2) passive transport through membrane channels or pores; (3) active transport; facilitated transport; or (4) phagocytosis (also pinocytosis and endocytosis) (Ref. 21). Whether a substance can or will be absorbed, and the degree to which it can be absorbed depends largely upon the physicochemical properties of the substance, the anatomical makeup of the exposed organism and the site of exposure (Ref. 21). Substances released to the environment that are not absorbable by terrestrial or aquatic species may be transformed in the environment to metabolites that are absorbable and, hence, bioavailable.

An important point to stress regarding the bioavailability of metals is that availability of a metal is

not

a prerequisite for its bioavailability. Metals can be bioavailable in either their neutral (MG

0

) or ionic (MG

+x

) oxidation states; or as part of an intact inorganic or organic compound. When in ionic oxidation states many metals are generally absorbed by active transport processes. Here, cellular membrane-bound proteins carry the metal across the cell membrane and into the cell. While it would seem that most metal ions are sufficiently small and water soluble to simply pass through membrane channels, their hydrated ionic radii are usually too large to permit their passage by this mechanism. Metals in their neutral or ionic oxidation states may be taken up by organisms by phagocytic processes as well. Organometallic substances are substances in which the metal is bonded to carbon-containing substituents. These substances can be absorbed intact by passive diffusion. The absorption of poorly water soluble inorganic metallic substances can occur via phagocytosis, or by other mechanisms. In terrestrial or aquatic life forms that have digestive systems that secrete strong acids, a poorly water soluble inorganic metallic substance or a metal in its neutral oxidation state can react (following oral exposure to the substance) with the acid to form a water soluble salt of the metal. Under these circumstances the metal is made available within the digestive system, and is absorbed in its ionic oxidation state. See Refs. 21, 22, 23, and 24.

The distribution, metabolism, and rate of excretion of a metal or metal compound depends upon the nature of the metal or metal compound, and the anatomy, physiology and genetic makeup of the organism. Metals absorbed in their neutral or ionic oxidation state be excreted unchanged or react with endogenous substances to form a metal compound

in vivo

. Organometallic substances are typically more lipid soluble than is the metal in its neutral or ionic oxidation state, and can be distributed more readily to areas of the organism that otherwise may be

poorly accessible by the metal in its neutral or ionic oxidation state. Organometallic substances may also undergo metabolic transformations

in vivo

in which the metal is liberated from its organic constituents. The same is true for inorganic metallic substances absorbed intact. See Refs. 24, 25, and 26.

Generally the ionic oxidation states of metals are the most available and, for many life forms, the most bioavailable. For aquatic species the bioavailability of a metal is expected to be greater from those metal compounds in which the metal is readily available in aquatic environments than from metal compounds or complexes in which the metal is not readily available in aquatic environments. This is because the metal is in a completely disaggregated state and dissolved in the aqueous media of the aquatic environment, which favors uptake of the metal by aquatic organisms since they are typically immersed in the aqueous media. However, aquatic species can also absorb intact metal compounds (e.g., organometallic substances). Thus, metals may be bioavailable from metal compounds or metal complexes even where the metal is not available in aquatic environments. Many aquatic organisms such as mussels, clams, and oysters, for example, consume as food organic materials suspended in aqueous media. These molluscs use short, hairlike locomotory organelles (cilia) to take in suspended organic materials from the water. Water currents sweep the suspended organic materials into the open shells, where they become fastened to a film of mucus. The cilia sweep the mucus to the mouth of the mussel. Soft, fingerlike organs push the mucus and organic materials into the mouth of the mussel, where it is taken in and digested. As stated by EPA in the proposed rule regarding lead and lead compounds, and by many commenters, lead dissolved in aqueous media may be removed from solution through sorption to suspended organic matter. Although no longer available, the lead in these suspended complexes may still be

bioavailable

in aquatic life forms that consume solid organic materials as food. Another example is that fish can absorb organometallic substances (intact) via passive diffusion through their gill membranes. See Refs. 24, 27, and 28.

The availability of a metal from the

same

metal compound may vary in different terrestrial or aquatic locations. Differences in environmental conditions lead to differences in the environmental fate of the compound in different environments. In an aquatic environment that contains metal ions of the same metal, the bioavailability of the metal in different aquatic species may vary even though the availability of the metal to each species is the same (i.e., the concentration of the metal in its ionic oxidation state is the same throughout the aquatic environment). These differences in bioavailability in different aquatic species are due to the differences in anatomy, physiology, and pharmacokinetic differences among the species. For different compounds that contain the same metal, the bioavailability of the metal ion in a given organism within a particular terrestrial or aquatic location may vary among different compounds. For a given organism, differences in bioavailability of a metal among compounds that contain the metal may be ascribed to differences in the physicochemical properties of the metal compounds and pharmacokinetic differences.

As mentioned above, metals or metal compounds released to the environment from anthropogenic sources are affected by prevailing environmental conditions, meaning broadly the wide variety of physical, chemical and biological processes that act upon them. These processes collectively determine the metal compounds in which the metal can exist in the environment. Lead can enter the environment as available or bioavailable compounds, or as compounds that are not available or bioavailable. However, lead that enters the environment as compounds that are not available or bioavailable can be converted in the environment to compounds that are available or bioavailable. As mentioned above, the ionic oxidation states of metals are generally the most available and, for many organisms, the most bioavailable. Hence, environmental factors that affect the availability of a metal may indirectly affect the bioavailability of metal. It is therefore important to consider those factors that influence the availability of a metal in the environment, when assessing physical or biological properties of the metal. However, as also discussed above, availability of a metal is not a prerequisite for its bioavailability. Interconversion of inorganic metal compounds can be quite rapid and as a result the metal compound in which the metal is released may not be the predominant metal compound post-release. Availability of a metal from an organometallic compound or insoluble inorganic compound is affected by many factors and its determination is complex, but many of the more important variables are discussed below for lead. A detailed discussion of the environmental fate of lead, that is illustrative of many of the more important environmental variables that affect availability and bioavailability of metals in general is provided in Unit V.A. of the proposed rule (64 FR 42227-42228), in

The Environmental Fate of Lead and Lead Compounds

(Ref. 2), and below.

In some instances, after deposition in the soil environment, lead may bind strongly by mechanisms such as the formation of insoluble complexes with organic material, clay minerals, phosphate, and iron-manganese oxides common in many soils. However, some of the lead in the soil environment (0.2 to 1%) may be water soluble. The extent of sorption appears to increase with increasing pH. Under acidic conditions, levels of lead in soil water can increase significantly. (The solubility of lead increases linearly in the pH range of 6 to 3.) Cation exchange capacity (CEC, related to soil clay content) and pH also influence the capacity of soil to immobilize lead. Using organic chelation as a model, the total capacity of soil to immobilize lead can be predicted by a linear relationship equation. Using this model to predict saturation capacity from CEC and pH it can be shown that a decrease in pH from 5.5 to 4.0 will reduce estimated soil capacity 1.5 times, thereby increasing the concentration of available lead in soil water (Ref. 2).

A number of field studies demonstrate the enhanced mobility of lead in soils under a range of environmental conditions. In all of these studies variables including pH, soil organic matter content and the chemical species of lead present played a significant role in increasing soil lead mobility. Limited data also indicate that organo lead compounds may be converted into water-soluble lead compounds in soil. Degradation products of tetramethyl and tetraethyl lead, the trialkyl lead oxides, are expected to be significantly more mobile in soils than the parent compounds (Ref. 2).

Levels of soluble lead in surface waters depend on the pH of the water and the dissolved salt content. Equilibrium calculations show that at a pH greater than 5.4 the total solubility of lead is approximately 30 micrograms per liter (μg/L) in hard water and approximately 500 μg/L in soft water. In soft water, sulfate ions limit the lead concentration in solution through the formation of lead sulfate. The lead carbonates limit lead in solution at a pH greater than 5.4 (Ref. 29). Concentrations as high as 330 μg/L could be stable in water at a pH near 6.5 and an alkalinity of about 25 milligrams (mg) bicarbonate ion per liter. Water

having these properties is common in runoff areas of New York state and New England.

Lead also forms complexes with organic matter in water. The organic matter includes humic and fulvic acids that are the primary complexing agents in soils and widely distributed in surface waters. The presence of fulvic acid in water has been shown to increase the rate of solution of lead sulfide 10 to 60 times (Refs. 30 and 31). At pH levels near neutral (i.e., about 7.0), soluble lead-fulvic acid complexes are present in solution. As pH levels increase, the complexes are partially decomposed, and lead hydroxide and carbonate are precipitated.

At neutral pH lead generally moves from the dissolved to the particulate form with ultimate deposition in sediments. There is evidence that in anaerobic sediments, lead can undergo biological or chemical methylation. This process could result in the remobilization and reintroduction of transformed lead into the water column where it could be available for uptake by biota, and volatilization to the atmosphere. However, tetramethyl lead may be degraded in aerobic water before reaching the atmosphere.

It can be concluded that many processes commonly observed in the environment result in the release of lead ion, which is available and bioavailable lead. These processes may occur in soil and aquatic environments with low pH and low levels of organic matter. Under these conditions, the solubility of lead is enhanced and in the absence of sorbing surfaces and colloids, lead ion can remain in solution for a sufficient period to be taken up by biota. Lead sorption to soil organic matter has been shown to be pH dependent. A decrease in soil pH can cause sorbed lead to desorb, and increase lead availability in soil water.

A few commenters contend that bioavailability is only possible for released soluble metal compounds. This position is incorrect: EPA has concluded that metal compounds, including lead compounds, that are released as metal compounds that are not soluble or bioavailable may be converted in the environment into metal compounds that are available or bioavailable. Furthermore, as discussed above, a metal compound may not be soluble, but may, nonetheless, be bioavailable.

Several commenters contend that EPA should consider each member of a metal compounds category (such as lead compounds) individually because the availability will vary from metal compound to metal compound within a category and some metal compounds will not be available at all.

EPA disagrees. As discussed above in Unit VI.C.1. with respect to evaluating persistence for metal compound categories, the Agency believes that it is reasonable to evaluate metal compound categories, such as lead compounds, as a category rather than individually. Moreover, in the case of lead compounds, the bioavailability of a lead compound is not necessarily dependant upon the availability of lead from the compound. That is, the parent lead compound may be bioavailable as is or, if not itself bioavailable, could be converted in the environment into a compound that is bioavailable or from which lead is bioavailable. As EPA has discussed elsewhere in this preamble, the environmental fate assessment indicates that there are many conditions under which lead from lead compounds can become available in the environment. Further, most lead compounds provide bioavailable lead when ingested. In addition, regardless of the relative environmental availability of lead from one lead compound to another, the lead compounds all add to the environmental loading of lead. Thus, even if under the same environmental conditions the lead from compound A is 10 times less available than the lead from compound B, compound A would introduce the same amount of available lead if its releases are 10 times greater. If lead compounds are evaluated individually based on relative environmental availability then the additive effect of the loading of lead from these compounds would be ignored.

Two commenters criticize EPA for not using the latest tools for assessing the availability of metals, including those tools in which the Agency was or is involved with developing. These commenters mention several Agency efforts that pertain to availability and the assessment of metals. These include the Environmental Sediment Guidelines and the Biotic Ligand Model development for the Water Quality Criteria.

The environmental processes that determine the complexation, speciation, and ultimately the availability of lead in the environment have been considered and addressed elsewhere in this preamble. In conducting its assessment of the availability of lead in the environment, EPA reviewed the available documentation on both the simultaneously extracted metals/acid volatile sulfide (SEM/AVS) methodology and the Biotic Ligand Model (BLM). EPA believes that the SEM/AVS methodology as applied to the Environmental Sediment Guidelines, and the BLM as applied to water quality criteria show great promise for use in conducting

site-specific

assessments of those metals for which it has been validated. However, to date neither the SEM/AVS methodology nor the BLM have been validated for lead, nor have the substantive technical comments provided by the EPA Science Advisory Board been incorporated into these approaches. In addition, EPA does not believe that a means currently exists to incorporate these methodologies into the technical analysis supporting a

nationally

applied regulation such as this rulemaking. While at this stage of their development these methods may be useful in site-specific assessments, they cannot be applied to support national Agency programs such as the TRI Program because of the variability in environmental conditions throughout the United States. On the other hand, the PBT methodology, as used by EPA in the characterization of lead as a PBT chemical, can be used to provide technical support to national regulatory programs such as the TRI Program because this methodology incorporates the environmental processes that determine the complexation, speciation, and the availability of lead in the environment, but does not require site-specific input. EPA believes that the PBT model is an appropriate methodology for assessing the persistence of metals, including lead.

3.

What comments did EPA receive on the bioaccumulation of metals and metal compounds?

Numerous commenters suggest that for metals and metal compounds bioaccumulation is not a relevant endpoint of concern. They contend that for metals and metal compounds: (1) Bioaccumulation is mitigated by environmental factors; (2) that metals and metals compounds are often essential nutrients and thus organisms have developed mechanisms to control their accumulation; (3) that BCF values for metals are dependent upon the concentration of the metal; and (4) that metals do not bioaccumulate at the concentration levels associated with toxicity. As discussed in detail in the following comment responses, EPA does not believe that any of the issues raised by the commenters call into question EPA's scientific and policy reasons for considering bioaccumulation for lead and lead compounds. Not all metals are essential nutrients and even those that are can be accumulated to unsafe levels. In particular, lead is not an essential nutrient. While some metal BCF values

vary with metal concentration this does not change the fact that the metals do bioaccumulate. In addition, bioaccumulation does not need to occur at concentrations that cause toxicity to be of concern, and in fact testing of bioaccumulation should not be conducted at concentrations that are detrimental to the test organism. Moreover, where there is extensive human data showing significant bioaccumulation of a listed toxic chemical, such as here, the bioaccumlation of the metal is obviously of concern. Therefore, EPA believes that bioaccumulation potential is a relevant endpoint of concern for metals, especially for lead and lead compounds.

Several commenters contend that the extent to which a metal bioaccumulates in aquatic organisms is dependent upon the metal's concentration in the aqueous habitat of the organism. Specifically, this commenter states that the BAF or BCF of a substance is inversely related to its concentration in the surrounding aqueous medium: that is, BAFs and BCFs become larger as the external concentration of the substance decreases. Thus, according to the commenter, because a metal's BCF or BAF value in a given aquatic organism will vary depending upon concentration, a single BAF or BCF value cannot be used to define whether a metal bioaccumulates. In effect the commenter is disagreeing with EPA's definition of BCF and BAF since the definitions do not require that all concentrations of the chemical result in the same BCF or BAF.

The Agency is in general agreement with the commenters' position that for a substance that bioaccumulates in aquatic species the degree to which it does so (i.e., the BAF and BCF of the substance) is related in part to the external concentration of the substance. The Agency also believes, however, that external concentration is not the only factor that influences bioaccumulation. As discussed previously, the propensity of a substance to bioaccumulate in a species depends largely upon the pharmacokinetics of the substance in that species. For further discussion on pharmacokinetics and bioavailability and bioconcentration see Unit VI.C.2.

In addition, the Agency believes that when analyzing test data, the conclusion that bioaccumulation decreases as external concentration of a substance increases may be erroneous. It is quite possible that as the concentration of the test substance is increased, biochemical changes that are precursor events to toxicity are initiated. While the increased concentration may not be sufficient to cause death to the organism, the initiation of the precursor events may cause a stasis in cell growth or function, and interfere with the organism's ability to absorb the metal. In a species where this is the case, it would therefore incorrectly appear that the bioaccumulation of the metal decreases as external concentrations increase. Thus, the Agency is in general agreement with the commenter's position that, for a substance that bioaccumulates in aquatic species, the degree to which it does so is related to the external concentration of the substance. The Agency, however, does not agree that the relationship for metal is always truly inversely related: i.e., that as external concentration increases bioaccumulation decreases. This is not a general phenomenon for all metals and metal compounds in all organisms as suggested by the commenter.

When discussing BCF and BAF values, distinction needs to be made between BAF or BCF values that are measured in a laboratory from those that are measured in an actual environmental setting. The Agency's definition of BCF and BAF (64 FR 42229) pertain to determinations of BAF and BCF under controlled experimental conditions where exposure of the aquatic species to the chemical is kept relatively constant (i.e., external concentration of the substance remains relatively constant). Thus, assays performed in laboratories to determine BAFs and BCFs are conducted under controlled conditions, and any sources of variability in conditions are minimized or eliminated. In a laboratory assay the test concentration is usually set at some percentage below the acute LC

50

(the concentration lethal to 50% of the test organisms following acute exposure); often

1/10

of the LC

50

of the metal is used. While there is no reason BCF tests cannot be conducted at other concentrations of the test chemical, it would serve no scientific purpose to use concentrations at which the test organism becomes stressed or dies before the test assay is completed or before the organism has the opportunity to bioaccumulate the test chemical. In an actual environmental setting, however, conditions can be variable. No commenter to this rule provided scientific data showing that these BCF values would not be found in the environment. Consequently, EPA believes that appropriately conducted bioaccumulation tests conducted at even at one concentration of lead are valid indicators of the potential for lead to bioaccumulate.

Two commenters claim that EPA dismisses the notion that bioavailable metals are often intentionally bioaccumulated as beneficial nutrients or are otherwise safely metabolized by plants and animals through biological mechanisms. One of the commenters states that while metals can bioaccumulate, the manner and rate at which they do so varies based upon the nutritional needs of the organism, external concentration of the metal, and speciation of the metal. The commenter also states that the bioaccumulation of metals is fundamentally different than the process by which organic compounds bioaccumulate.

EPA acknowledges that some metals are nutrients in some organisms, including humans, or are otherwise necessary for the subsistence of organisms. Thus, some metals need to be bioaccumulated by the organism. Clearly, such metals need to be bioavailable in the organisms that require these metals. As discussed in greater detail elsewhere in this document and as alluded to by one of the commenters, in many organisms the absorption or uptake of metals across cell membranes involves active (i.e., energy-requiring) processes, whereas absorption or uptake of organic substances is usually the result of passive diffusion across cell membranes. Active transport processes give the organism some ability to regulate the uptake of metals. It is also important to note that active transport across cell membranes is not the only means by which a metal can be absorbed. Organometallic substances, for example, are often absorbed by passive diffusion. Metals and metal containing substances may also be taken up by organisms through phagocytic processes. In addition, as one of the commenters states, metal speciation and concentration are factors that can influence uptake of metals into an organism.

While active transport processes are involved with the uptake of metals needed by the organisms, these processes do not always discriminate those metals that are needed by the organism from those metals that are harmful to the organism. Thus, organisms also have the ability to take up or absorb metals that are not nutrients and that are not necessary for subsistence. Thus, the processes that organisms use to absorb or take up needed metals do not necessarily prohibit or protect them from taking up toxic metals. In addition, even needed metals can be toxic to the organism if over exposure occurs. It is well established that metals that are not needed by an organism can be taken up by the organism, and bioaccumulated by the organism. lead and mercury, for

example, are not known to be essential metals in any species. Yet the uptake and bioaccumulation of these metals by organisms, including humans, is well established. EPA has therefore determined, insofar as commenters are suggesting that EPA consider the nutrient value of metals in this rulemaking, that such comments are irrelevant because lead has no known nutritive value to any species. The results of the studies investigating the bioconcentration of lead and lead compounds in aquatic organisms summarized in Table 1 (64 FR 42230) of the proposed lead rule and the table in Reference 10 of the proposed rule show that lead is taken up and bioaccumulated by many different aquatic organisms. Also, as discussed in Unit VI.D.3., EPA's fish advisory data base demonstrates that many species of fish and shellfish from various aquatic environments in different regions of the country contain lead (see http://fish.rti.org) indicating that fish and shellfish bioaccumulate lead under realistic environmental conditions.

Two commenters stated that bioaccumulation of metals does not necessarily indicate the presence of, or a potential for adverse effects. At the outset, EPA stresses that lead and lead compounds are EPCRA section 313 listed toxic chemicals. Therefore, as stated in the proposed rule and elsewhere in this preamble, the toxicity of lead and lead compounds is not at issue in this rulemaking. These commenters state that bioaccumulation of a substance is not an indicator of hazard, and should not be used as a hazard assessment criterion.

The Agency agrees that the ability of a substance to bioaccumulate does not by itself necessarily indicate the presence of, or potential for adverse effects. The Agency believes, however, that the concept of bioaccumulation is relevant to the hazard characterization of metals for the same reasons that it is relevant to the hazard characterization of organic substances: that low-level or sub-toxic exposures to a toxic substance that bioaccumulates could eventually lead to exposures of concern in the organism that bioaccumulates it or increased exposure potential for predator species. The Agency would also like to emphasize that while bioaccumulation of lead in a given aquatic organism may not necessarily be toxic to the organism, the accumulated lead may serve as a source of lead exposure and toxicity to predator species, including humans.

Thus, the high bioaccumulation potential of lead, an EPCRA section 313 listed toxic chemical, within an organism is anticipated to contribute a greater total body burden relative to a chemical with lower bioaccumulation potential, thereby increasing any toxicity to the organism. High bioaccumulation also increases lead exposure to other organisms that are predators of the organism that has accumulated the lead.

4.

What comments did EPA receive on the relationship of its persistence and bioaccumulation criteria to international criteria?

Two commenters claim that numerous international organizations such as the Organization for Economic Cooperation and Development (OECD) have approached the classification of PBT chemicals in a manner that calls into question EPA's use of persistence and bioaccumulation criteria for accurately identifying the human and environmental health hazards of metals. One of the commenters claims that the OECD Advisory Group on Harmonization of Classification and Labeling (which includes EPA participants) has made the following conclusion: “...For inorganic compounds and metals, the concept of degradability as applied to organic compounds has limited or no meaning. Rather, the substance may be transformed by normal environmental processes to either increase or decrease the bioavailability of the toxic species.” The commenter recommends that EPA reconsider its characterization of lead as a PBT chemical because, in the opinion of the commenter, there is a lack of scientific support for assessing a metal's PBT characteristics to determine its potential hazard to human health and the environment.

The Agency believes the commenter has misunderstood OECD's position on the applicability of general PBT criteria to metals. The quote is taken from the OECD document entitled

Harmonized Integrated Hazard Classification System for Human Health and Environmental Effects of Chemical Substances.

(Ref. 32) The pronouncements on metals are contained in paragraphs 22 and 23 of that document. Paragraph 22 reads as follows:

For inorganic compounds and metals, the concept of degradability as applied to organic compounds has limited or no meaning. Rather the substance may be transformed by normal environmental processes to either increase or decrease the bioavailability of the toxic species. Equally, the use of bioaccumulation data should be treated with care. Specific guidance will be [but has not yet been] provided on how these data for such materials may be used in meeting the requirements of the classification criteria.

By “degradability as applied to organic compounds” OECD means molecular degradation, most often by microbial degradation and/or hydrolysis or other abiotic processes, to progressively simpler organic chemical structures, leading eventually to inorganic substances like carbon dioxide and water. It is important to note that paragraph 22 does not in any way suggest that metals are not persistent. Moreover, it does not suggest that OECD hazard classification criteria cannot be applied to metals, only that “care” (e.g., professional judgment) is required in the interpretation of data relative to the classification criteria. In fact, EPA agrees that in order for a metal to bioaccumulate in an organism it must either be environmentally available or bioavailable. In response to the allegations that lead is not environmentally available, as part of the proposed rule, the Agency analyzed information on the environmental fate of lead, and, as noted above, determined that lead has the potential to become available from lead compounds under commonly encountered environmental conditions. In addition, as explained in Unit VI.D.3, EPA determined that lead and lead compounds are bioavailable. Therefore, the Agency's assessment of lead as a PBT chemical is consistent with the OECD's intent.

EPA does not interpret the above quote to indicate that OECD's position is that its or any PBT chemical criteria are not applicable to lead. As the commenter correctly states, EPA is a member of the OECD Advisory Group on Harmonization of Classification and Labeling. OECD does not recommend that metals and metal compounds be

excluded

from consideration as PBT chemicals, as the commenter implies. More specifically, OECD has not concluded that metals and metal compounds have no potential to bioaccumulate because they are never released as bioavailable compounds; or cannot be converted to bioavailable compounds under any foreseeable circumstances. On the contrary, EPA believes that the preceding language indicates that OECD's position is that any substance judged to be potentially bioavailable, whether organic or inorganic, should not be excluded as a candidate from some form of regulatory action. As discussed in Units VI.C.2. and VI.D.1., it is realistic to expect that, in general, released metals such as lead can encounter conditions in which they are (or can become) available at levels sufficient to bioaccumulate. Therefore, the Agency's use of the PBT criteria in its assessment of lead is consistent with

OECD's position on the general applicability of PBT criteria to metals.

5.

What comments did EPA receive on its metals policy?

Some commenters contend that EPA should not consider all members of the lead compounds category to be PBT chemicals because availability and bioavailability of the lead portion will vary among the compounds. These commenters further state that the toxicity can only be evaluated on a compound-by-compound basis and is dependent on bioavailability.

Members within the lead compounds category listed on the EPCRA section 313 list of toxic chemicals have a common moiety that bestows toxicity, i.e., lead. Consequently, it is reasonable to anticipate that once released into the environment: (1)The metal moiety in each member of the category will become available as a result of abiotic and/or biotic processes or (2) each member of the category will either be bioavailable or will convert into a compound that is bioavailable. For example, different inorganic lead compounds that are released into acidic surface waters will result in the formation of similar soluble inorganic lead compounds. Variation in the level of availability or bioavailability does not negate the consistency of effect across the members of the category.

EPA would like to remind the commenters that a mechanism already exists under EPCRA section 313 to address concerns for any metal compound for which the data show that the metal can never become available. Thus, the issue of availability, which is broader than the issue of a compound's potential to bioaccumulate, was addressed previously for EPCRA section 313 chemical assessments through EPA's policy and guidance concerning petitions to delist individual members of the metal compound categories listed under EPCRA section 313 (May 23, 1991, 56 FR 23703). If a petitioner has information demonstrating that a particular lead compound does not cause toxicity as the intact lead compound, and will not cause lead to be available in the environment to express its toxicity, they can submit a petition pursuant to EPCRA section 313(e)(1) to delete that specific lead compound from the EPCRA section 313 list of toxic chemicals. Under the metals policy EPA considers whether the metal from a metal compound can ever become bioavailable under abiotic or biotic conditions. An assessment of the availability and bioavailability of a lead compound would include processes such as: hydrolysis at various pHs; solubilization in the environment at various pHs; photolysis; aerobic transformations (both abiotic and biotic); anaerobic transformations (both abiotic and biotic); bioavailability when the compound is ingested (solubilization in and/or absorption from the gastrointestinal tract and solubilization in various organs); and bioavailability when the material is inhaled (solubilization in and/or absorption from lungs, especially taking into account the likelihood that the compound will lodge in the lungs and be converted a soluble compound by the lung's defense mechanism).

If the commenters have information demonstrating that a particular lead compound does not cause toxicity as the intact lead compound, and will not cause lead to be available in the environment to express the toxicity of the metal, the commenters can submit a petition pursuant to EPCRA section 313(e)(1) to delete that specific lead compound from the EPCRA section 313 list of toxic chemicals. EPA would address such a petition in accordance with the Agency's longstanding stated policy and guidance concerning petitions to delist individual members of the metal compounds categories (May 23, 1991, 56 FR 23703).

6.

What comments did EPA receive that pertain to natural vs. industrially produced lead and lead compounds?

Some commenters contend that natural forms of lead, as opposed to industrially produced lead compounds, should not be classified as PBT chemicals. Other commenters state that because lead occurs naturally, industrial activities involving lead do not change the total amount of lead in the earth: these activities only affect the form and location of the lead in the environment. These commenters believe that the forms of lead that are produced by industrial activity tend to be more hazardous and should be regulated more strictly than the natural forms, such as trace amounts of lead in natural minerals.

EPA disagrees that natural lead compounds should be treated differently than industrially produced lead compounds. While the comment was made specifically for lead it is general to all metals and metal compounds. Both naturally occurring and industrially produced lead and lead compounds, meet the persistence and bioaccumulation criteria. EPA's analysis of the environmental fate of lead demonstrates that it is reasonable to anticipate that under environmental conditions lead can become available from lead compounds, and that whether lead or lead compounds are obtained naturally or produced industrially does not change the potential for availability of lead. Whether a chemical comes directly from the ground or from a manufacturing plant will not affect whether the chemical is toxic, persistent, and bioaccumulative. These are the result of the inherent properties of the chemical, not from their origin (all other things being equal).

The Agency recognizes that lead and certain lead compounds occur naturally. EPA agrees that industrial activities involving lead do not change the total amount of lead in the earth, and that industrial activities involving lead only affect the type of lead compound and its location in the environment. The Agency believes, however, that while industrial activities do not increase the total quantity of lead in the earth, industrial activities transport lead and lead compounds from one environment to another environment in which the likelihood of exposure to lead in aquatic and terrestrial species, and humans is increased. As discussed in the PBT rulemaking (64 FR 688-729), environmental conditions can vary greatly among geographic locations, even those that are in close proximity to one another. There may be certain geographical areas in which the environmental conditions are such that lead availability from a naturally occurring lead compound may be equal to or greater than that from an industrially produced lead compound.

D.

What Comments Did EPA Receive Concerning the Persistence and Bioaccumulation of Lead and Lead Compounds?

In the proposed rule to lower the thresholds of lead and lead compounds, EPA discussed its scientific basis for preliminarily characterizing lead and all lead compounds as highly persistent and highly bioaccumulative. To summarize, the data on lead's persistence in the environment, the observed high bioaccumulation values in aquatic organisms, and lead's ability to accumulate in humans were the basis for EPA's preliminary conclusion that lead and lead compounds are highly persistent and highly bioaccumulative. EPA has also evaluated the bioavailability of lead and lead compounds and has concluded that lead is bioavailable. In the proposed rule the Agency specifically requested public comment on its discussion of the scientific information concerning: (1) The fate, transport and availability of lead in the environment and how this information should be considered in classifying lead as a PBT chemical (Unit V.A.); (2) the bioaccumulation of lead in aquatic organisms, and how this

information should be evaluated in assessing the bioaccumulative potential of lead and lead compounds (Unit V.B.); (3) the bioaccumulation of lead in humans, and how this information should be considered in classifying lead and lead compounds as highly bioaccumulative (Unit V.C.); and (4) abiotic factors (e.g. soil chemistry; pH; water hardness; presence of organic matter in aqueous media) that can diminish the bioavailability of lead in aquatic species.

The Agency received many comments regarding EPA's technical basis for preliminarily characterizing lead and lead compounds as highly persistent, and highly bioaccumulative. These comments were extensively reviewed and considered by the Agency in finalizing the rule. While some of the commenters agreed with the Agency's characterization of lead and lead compounds as highly persistent and highly bioaccumulative, the majority of the commenters disagreed. Most of the comments were similar in content, and pertained to general or specific issues dealing with persistence, bioaccumulation and toxicity, as well as EPA's use of persistence and bioaccumulation data pertaining to lead and lead compounds in characterizing these chemicals as PBT substances. Lead and lead compounds are included on the EPCRA section 313 list of toxic chemicals. EPA is not responding to comments on the toxicity of lead and lead compounds, because their inclusion on the EPCRA section 313 list of toxic chemicals is not at issue in this rulemaking. After consideration of all comments submitted in response to the proposed lead rule, EPA concludes that lead is highly persistent and, at the least, bioaccumulative and defers its determination as to whether lead is highly bioaccumulative. An explanation for EPA's conclusion that lead is at least bioaccumulative is provided below. The basis for EPA's conclusion that lead is highly persistent is provided elsewhere.

In the PBT chemical rulemaking, EPA described bioaccumulation as “the process by which organisms may accumulate chemical substances in their bodies” (64 FR 703) and defined the term as the “net accumulation of a substance by an organism as a result of uptake from all environmental sources.” (64 FR 703) EPA has a concern for those toxic chemicals that are bioaccumulative and a particular concern for that subset of PBT chemicals that are highly bioaccumulative.

There are extensive, high quality human data (64 FR at 42230-31) that clearly indicate that lead and lead compounds bioaccumulate in humans, i.e., humans accumulate lead as a result of uptake from environmental sources. These data include bioaccumulation data on a number of subpopulations of humans, such as children, pregnant women, postmenopausal women, and men. Therefore, these human data support EPA's conclusion, as discussed below, that lead and lead compounds are bioaccumulative. EPA believes that these data would tend to support a finding that lead is also highly bioaccumulative because (1) the data are human data and (2) these data conclusively demonstrate that lead bioaccumulates in humans. EPA believes that these two factors are relevant to a determination that lead and lead compounds are highly bioaccumulative because human data are generally more compelling than animal data, particularly where there are multiple, high quality studies on a broad range of individuals. Thus, these data are sufficiently conclusive that there is no question that lead and lead compounds bioaccumulate in humans.

While evaluation of these data might affect EPA's conclusion as to whether lead and lead compounds are highly bioaccumulative, EPA recognizes that it did not clearly articulate in the proposed rule how human data would be used to distinguish between bioaccumulative and highly bioaccumulative chemicals. Because of this, EPA is deferring at this time the classification of lead and lead compounds as highly bioaccumulative solely on the basis of the extensive human data.

A number of industry commenters have contended that BCFs and BAFs measured for metals (including lead), and in particular essential elements, are not representative of the potential of these substances to bioaccumulate. They claim that the variability of the measured BCFs/BAFs with changing water concentration of the chemical makes it difficult to determine the most representative BCF/BAF value for a particular species. Specifically, these commenters contend that there is an inverse relationship between the measured BCF/BAF values and water concentration. Some commenters assert that only the values measured at higher water concentrations should be used, i.e., the lower BCF/BAF values. Other commenters contend that BCFs and BAFs are not meaningful measures for the bioaccumulation of metals and, therefore, cannot be used.

EPA disagrees that this is the best characterization of the bioaccumulation data for metals, including lead, in aquatic species. While this type of relationship may exist for some species and/or some metals, for other species and/or metals other relationships are observed: (1) Constant BCFs/BAFs with increasing water concentration; (2) increasing BCFs/BAFs with increasing water concentration; and (3) varying BCFs/BAFs values with constant water concentration.

EPA disagrees that the BCF/BAF data cannot be used to determine the potential for lead, which is not an essential element, to bioaccumulate. EPA recognizes that some data suggest that the relationship between bioaccumulation and water concentration of lead could be characterized as inverse for some organisms, such as fish, algae, and phytoplankton. Such a characterization, however, is incorrect for invertebrates such as snails and bivalves because there is little variation in BCF value with changing water concentration for these species. Further, EPA does not believe that even where the data suggest an inverse relationship, this precludes the use of BCFs and BAFs in assessing the bioaccumulative potential of lead. EPA notes that even for some species in which an inverse relationship is suggested (e.g., algae and phytoplankton), if EPA were to use the BCF or BAF at the highest water concentration measured (i.e., the lowest measured BCF/BAF value) the BCF/BAF values remain over 5,000.

EPA has determined that the data on oysters, snails, algae, phytoplankton, and blue mussels, as well as the human data, clearly support a conclusion that lead and lead compounds are bioaccumulative, and also believes that this information tends to support a finding that lead is highly bioaccumulative. However, during the public comment period and during inter-Agency review, questions were raised challenging the sufficiency of the data to support the conclusion that lead and lead compounds are highly bioaccumulative. Before determining whether lead and lead compounds are highly bioaccumulative, EPA believes that it would be appropriate to seek external scientific peer review from its Science Advisory Board, and EPA intends to do so. The external peer review would address the question of whether lead and lead compounds should be classified as highly bioaccumulative. The external peer review would address the issue of how lead and other, as yet unclassified, metals such as cadmium, should be evaluated using the PBT chemical framework, including which types of data (and which species) are most suitable for these determinations. After

the completion of the external scientific peer review, EPA will consider and take appropriate action, which could include characterizing lead and lead compounds as highly bioaccumulative and lowering the reporting thresholds for lead and lead compounds to 10 pounds. Therefore, at this time, EPA concludes that lead is, at the least, bioaccumulative and defers its determination as to whether lead is highly bioaccumulative until further review.

1.

What comments did EPA receive on the environmental fate of lead and lead compounds?

In the lead proposed rule (64 FR 42227) the Agency provided a qualitative environmental fate assessment of lead and lead compounds. Qualitative environmental fate assessments are generally part of a hazard assessment for a chemical. The qualitative environmental fate assessment was not developed, nor was it intended, to be part of an exposure assessment or risk assessment.

An environmental fate assessment for a metal and metal compounds, such as lead and lead compounds, describes the physical, chemical, and biological processes acting upon the metal and metal compound in the environment and the result of these processes. The environmental fate of a metal or metal compound varies depending on the environmental conditions and the physical/chemical properties of the metal in question.

The Agency received many comments on its assessment of the environmental fate of lead and lead compounds and the influence of environmental fate on the environmental availability of lead and lead compounds. Commenters contend that normal environmental processes control the availability of lead and lead compounds in water, soil and sediments and concluded that under most environmental conditions lead from lead and lead compounds would not be available for uptake by organisms due to processes including the pH dependent formation and precipitation of insoluble lead compounds in surface waters, and sorption of lead to organic matter and inorganic constituents in soil, surface waters and sediments.

EPA disagrees with these commenters and concludes that processes commonly observed in the environment can result in the formation of available lead where it can be bioaccumulated by organisms. EPA believes that these processes may occur in soil environments with low pH and low levels of clay and organic matter. Lead sorption to soils has been shown to be pH dependent. Decreasing pH can result in increasing concentrations of lead in soil water with greater availability for uptake by biota. In acidic aquatic environments, low levels of suspended solids and dissolved organic matter can result in increased levels of lead ion in solution where it can be taken up by biota.

One commenter believes that the environmental fate data that EPA used and cites in the proposed rule falls short of what is necessary for a scientifically valid approach to assessing the transformation, specification, and availability of lead in the environment. The commenter argues that the data cited by EPA indicate that very little of the lead released to the environment is likely to be present in a “bioavailable form” (i.e., EPA concluded that less than 1% of lead in soil may be water soluble).

EPA disagrees with the commenter's characterization of EPA's assessment of the environmental fate of lead and lead compounds. EPA asserts that it used reliable data from a variety of credible sources in concluding that lead can be available for uptake by organisms in the environment and that lead is environmentally available. EPA refers the commenter to the discussions of the transformation, speciation, availability and bioavailability of lead in the environment provided in

The Environmental Fate of Lead and Lead Compounds

(Ref. 2) and elsewhere in the RTC document for this final rule (Ref. 1). EPA disagrees with the commenter's interpretation of the statement “EPA concludes that less than 1% of lead in soil may be water soluble” to mean or indicate that very little of the lead released into the environment is likely to be present in a “bioavailable form”. Simple water solubility is

not

a prerequisite for a metal to become available from a metal compound. It is well established that certain environmental conditions can increase the solubility of a metal compound. Further, as discussed in Unit VI.C.2. of this preamble and in the RTC document (Ref. 1), availability of a metal is not a prerequisite for its bioavailability. Metals may be bioavailable from metal compounds or metal complexes that are not water soluble or in which the metal is not otherwise available. A classic example that illustrates these points are the well documented incidents of childrens' exposure to lead from consumption of soil that contains lead. While less than 1% of lead in soil is typically present as a lead compound that is water soluble (i.e., more than 99% is present as lead compounds that are water insoluble or bound to soils), the lead in soils is still bioavailable in humans.

EPA has concluded that lead released to the environment, whether under conditions where it is available or not, can reasonably be expected to be bioavailable in organisms. EPA's statement “that less than 1% of lead in soil may be water soluble” should not be interpreted to mean that the levels of lead in soils that is available are inconsequential or negligible. On the contrary, because exposure to even low levels of lead are expected to result in its bioaccumulation in many organisms, these levels are still of concern. It should be noted that if 1 percent of soil lead is soluble (i.e., available), this would mean that levels as high as 200 parts per billion (ppb) could be found in soil water (lead is present in many soils at 20 parts per million (Ref. 2) and one percent of this is 200 ppb.)

One commenter believes that the bioavailability of lead and lead compounds is only prevalent in those situations in which an organism would be exposed to continuous, localized influxes of lead compounds, such as near a lead smelter or a highway. The commenter believes that the proximity to sources of lead, such as smelters or highways (influenced by use of leaded fuels), is a prerequisite to high concentrations of the metal in the environment, and thus its potential to bioaccumulate. The commenter cites studies that provide data that show high levels of lead in waters and soils that are in close proximity to sources of lead releases (e.g., smelters, vehicular exhaust), and bioaccumulated lead in freshwater algae, invertebrates, and fish collected near industrialized areas, ponds with high numbers of lead shot, urban areas, lead mines and tailings ponds. The commenter states that although lead may be considered ubiquitous in the environment, its ecological impacts would appear to be significantly influenced by the proximity to sources of lead releases and the public should be aware of this. While the commenter used the term bioavailability, based on the context of the comment, EPA believes the commenter used the term interchangeably with the term environmental availability.

While the concentrations of lead in the environment are more likely to be higher in areas that are in close proximity to facilities that manufacture, process, or otherwise use lead and/or lead compounds, EPA disagrees with the commenter's contention that the availability of lead is only possible in such areas. EPA does not agree with the commenter's position that in order to be exposed to lead an organism needs to be in close proximity to points where lead

is released into the environment. As discussed in Unit V.A. of the proposed rule (64 FR 42227), and in

The Environmental Fate of Lead and Lead Compounds

(Ref. 2) many factors influence the mobility and disposition of lead in the environment. Under many environmental conditions lead may become mobile rather than remain stationary. Depending upon prevailing conditions and the method of environmental release, lead may travel within environmental media to areas that are not in close proximity to the point of release. Hence, EPA believes that the presence of lead in the environment, and therewith its availability, is not confined to the areas where lead is released from anthropogenic sources. In addition, any release of lead is important to local communities, because of lead's persistence and bioaccumulative properties. Although EPA disagrees with the commenter's conclusions, the commenter's statement that the ecological impacts of lead are influenced by the nearness to a source of release still provides support for the actions that EPA is taking in this rulemaking.

a. What comments did EPA receive on the abiotic factors that may affect the environmental availability of lead?

Several commenters stated that EPA either did not, or should have considered speciation, transformation and bioavailability in its assessment of the persistence of lead and lead compounds. Some of the commenters contend that in most environments lead is either not available or is transformed into forms that are less available. A number of the commenters claimed that the environmental conditions in which lead is mobile or available are rare.

EPA disagrees with the commenters claim that the Agency did not consider speciation, transformation and bioavailability in its characterization of lead and lead compounds as PBT chemicals. As discussed in detail in: Unit V. of the proposed lead rule (64 FR 42222-42243); in

The Environmental Fate of Lead and Lead Compounds

(Ref. 2); elsewhere in this preamble; and in the RTC document (Ref. 1), EPA performed a comprehensive assessment of the environmental fate of lead. The environmental fate assessment embodied an analysis of the environmental variables that affect speciation, transformation, and the availability of lead. These environmental variables include: pH; redox conditions; water hardness; dissolved organic carbon content; and soil properties including cation exchange capacity, organic carbon content, iron and manganese oxide and phosphorus content. As discussed in Unit VI.D.3., EPA has evaluated the bioavailability of lead and lead compounds and has concluded that lead is bioavailable. From its analysis of the environmental fate of lead, EPA concluded that environmental conditions exist in the United States in which lead may become available or that can increase the availability of lead, even from compounds in which lead, as released into the environment, is not available. From its analysis of the bioavailability of lead, EPA concluded that lead is bioavailable in many aquatic species, and in humans. EPA also concluded that lead compounds that are not available or bioavailable as released may be converted to lead compounds that are available or bioavailable. Thus, after an evaluation of the available data, EPA has determined that the weight of scientific evidence indicates that it is reasonable to conclude that lead in the environment will be available and/or bioavailable from lead and lead compounds.

EPA disagrees with the commenters who claim that the environmental conditions in which lead is mobile or available for uptake are rare. As detailed in Unit VI.C. of this preamble and in the RTC document (Ref. 1), EPA conducted several analyses of large databases containing information on the properties of rivers, streams, lakes, and soils in the United States, with a focus on the properties known to contribute to the availability of lead. Acidity is a particularly important determinant of lead availability: acid conditions (pH < 7) increase lead availability. In water, the solubility and, hence, availability of lead increases linearly as acidity is increased (i.e., from pH 6 to 3). EPA determined that waters of sufficient acidity to favor lead availability, especially in the Mid-Atlantic region of the United States, are not rare. In fact, estimates indicated that almost 11,000 kilometers of streams could have a pH of < 5.5. In addition, as detailed elsewhere is this document, a query of EPA's STORET water quality database indicated that in 1998 pH values of between 5.5 and 5.1 were found in 52 watersheds in the United States. Finally, the commenter asserts that acidic soils in which lead is likely to be available are rare. EPA's analysis of the database of the Soil Survey Laboratory, National Soil Survey Center, discussed in Units VI.C.1. and VI.D.1. of this preamble, found more than 10,000 surface soil samples with low cation exchange capacity and pH values of less than 5.5.

One commenter supports EPA's concern for cross media transport of chemicals, but believes that it is misleading for EPA to imply that lead is predisposed to find the medium in which it will be transformed into forms that have the “greatest bioavailability (in) man”. The commenter agrees that lead cannot be destroyed but, equates this attribute to most elements on the periodic table.

The commenter incorrectly asserts that EPA suggested that lead and lead compounds are released only to, or preferentially partitions to, those environments that are most favorable to enhancing availability or bioavailability of lead. EPA disagrees with the commenter. EPA has not made the claim that lead and lead compounds are released only into those environments where conditions are most favorable to the formation of the most soluble lead compounds. In EPA's discussion of the environmental fate of lead and lead compounds, EPA assessed the availability of the lead and lead compounds under a variety of conditions in water, sediments and soil. As discussed elsewhere, EPA believes that there are many environmental conditions in which lead and lead compounds will be available and/or bioavailable.

b. What comments did EPA receive on the availability of lead in surface waters and sediments.

One commenter stated that there are many studies that indicate that lead does not persist in soluble and bioavailable forms in aquatic environments. The commenter cited work reported by May and McKinney (Ref. 33) which, according to the commenter, has shown that the majority of lead entering natural waters will be precipitated to sediments as carbonates or hydroxides (i.e., will be unavailable). The commenter states that even in acidic lake waters, “which according to EPA's own reports are rare”, lead can precipitate out of the water, and cites work by White and Driscoll (Ref. 34) to support this position. Another commenter states that there is strong evidence to suggest that under conditions where organic material is present in the water column of an aquatic environment, the organic material will act to reduce the amount of potentially soluble and bioavailable lead. The commenter believes that the wide distribution of organic matter suggests that the potential for the reduction of soluble lead by complexation with organic material is high.

EPA disagrees with the argument that soluble and/or bioavailable lead compounds are irreversibly transformed into insoluble and un-bioavailable lead compounds. EPA discusses below and

elsewhere that many lead compounds that form as a result of conditions in the aquatic environment (e.g., lead-organic matter complexes, inorganic precipitates, carbonates and hydroxides ) are not necessarily permanently sequestered as a non-available lead compound, but are subject to processes that can result in their release back into solution. A review of the discussion of the fate of lead in natural waters in May and McKinney (Ref. 33) revealed a single sentence that says: “Upon entering natural waters, most lead is precipitated to the sediment bed as carbonates and hydroxides.” While this statement is true for some surface waters in the United States, EPA has concluded for the reasons discussed below and elsewhere in this preamble and in the RTC document (Ref. 1) that lead solubility is greater and precipitation as carbonate and hydroxide is less in acidic waters with low hardness.

White and Driscoll (Ref. 34) observed temporal and spatial variations in the concentration and transport of lead in the acidic Darts Lake in the Adirondacks of New York. Deposition of particulate lead was strongly correlated with aluminum and organic carbon deposition. Increasing metals deposition was observed during periods of increasing pH. The flux of lead into the lake was related to stream hydrology, pH and lead concentration. Stream pH varied seasonally, with a steady pH of 5.1 until spring snowmelt, where pH levels dropped to a minimum of 4.8 in April/May. Increases in pH occurred throughout the summer reaching a maximum of 5.4 in August. High flow periods in the fall and spring were marked by increases in the concentration of dissolved lead in the inlet and outlet streams. Lead flux to and from the lake was greatest during spring and fall periods of high lead concentrations, elevated water discharge, and low pH. The authors explain that even in acidic lake water containing a variety of particle types, oxides and organic films may determine the surface properties of suspended particulate matter. The solid matrix in the lake was probably composed of inorganic hydrous oxides (coatings) and adsorbed or coprecipitated organic matter. The interaction of lead with this matrix appears to be pH sensitive. Changes in pH may affect lead partitioning between the solid and solution through a number of possible mechanisms: matrix formation/dissolution, sorption/desorption of organic complexes and inorganic complexes, and hydrogen ion exchange reactions.

Contrary to the commenter's interpretation, EPA believes that the study by White and Driscoll (Ref. 34) provides evidence that even in the presence of dissolved organic carbon, soluble lead may be present in the water column of acidic waters, possibly through a process of sedimentation and decomposition of organic matter and/or dissolution of redox sensitive hydrous oxides.

Two commenters contend that the majority of lead entering aquatic systems will be removed from solution and become bound to sediments and/or susp

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