Organobromine Production Wastes; Identification and Listing of Hazardous Waste; Land Disposal Restrictions; Listing of CERCLA Hazardous Substances, Reportable Quantities
Federal RegisterMay 4, 1998
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SUMMARY: The EPA is adding two new hazardous waste codes to its current
lists of hazardous waste found in 40 CFR part 261. One waste type to be
added and designated by the hazardous waste code K140 is floor
sweepings, off-specification product and spent filter media from the
production of 2,4,6-tribromophenol. The second waste is 2,4,6-
tribromophenol and is being added both to the list of commercial
chemical products, designated by the hazardous waste code U408 and to
the list of hazardous constituents in Appendix VIII of 40 CFR part 261.
EPA is also modifying the land disposal treatment standards for
hazardous waste in 40 CFR part 268 by adding these new wastes. The
effect of listing this waste will be to subject it to stringent
management and treatment standards under RCRA, as well as to emergency
notification requirements for releases of hazardous substances to the
environment. These notifications are required under the Comprehensive
Environmental Response, Compensation, and Liability Act (CERCLA or
Superfund) and the Emergency Planning and Community Right to Know Act
(EPCRA). EPA is also issuing Reportable Quantity (RQ) requirements for
these notifications. EPA has made a final determination not to list as
hazardous ten waste streams from the production of bromochloromethane,
ethyl bromide, tetrabromobisphenol A, 2,4,6-tribromophenol wastewaters,
octabromodiphenyl oxide, and decabromodiphenyl oxide.
DATES: Effective Date: November 4, 1998.
ADDRESSES: The official record of this action is identified by Docket
number F-98-OBLF-FFFFF and is located at the following address: EPA
Docket Clerk, U.S. EPA, Crystal Gateway #1, 1st Floor, 1235 Jefferson
Davis Highway, Arlington, VA. The docket is open from 9 a.m. to 4 p.m.,
Monday through Friday, excluding Federal holidays. The public must make
an appointment to review docket materials by calling (703) 603-9230.
The public may copy 100 pages from the docket at no charge; additional
copies are $0.15 per page.
FOR FURTHER INFORMATION CONTACT: The RCRA/Superfund Hotline, at (800)
424-9346 (toll-free) or (703) 412-9810, in the Washington, DC
metropolitan area. The TDD Hotline number is (800) 553-7672, or (703)
486-3323, locally. For technical information on the final listing
determination, contact Anthony Carrell at (703) 308-0458, or
[email protected].
For technical information on the CERCLA aspects of this rule,
contact: Elizabeth Zeller, Office of Emergency and Remedial Response
(5204G), U.S. Environmental Protection Agency, 401 M Street, SW,
Washington, DC 20460, (703) 603-8744.
SUPPLEMENTARY INFORMATION:
This rule is available on the Internet. Please follow these
instructions to access the rule electronically: From the World Wide Web
(WWW), type http://www.epa.gov/epaoswer, then select option for Rules
and Regulations.
The official record for this action is kept in a paper format, and
is maintained at the address in the ADDRESSES section at the beginning
of this document.
I. Affected Entities
II. Legal Authority
III. Summary of the Proposed and Final Rules
A. Background Analysis
B. Summary of Proposed Rule
C. Additional Opportunity to Comment
D. Final Rule
IV. Response to Comments
A. Development of Structure-Activity Relationship (SAR) Analyses
B. Why the SAR Analysis of 2,4,6-TCP and 2,4,6-TBP Constitutes a
Scientific Study That Shows Toxic Effects
C. Issues Regarding the Use of Structure-Activity Relationship
(SAR) Analysis
D. Addition of Constituent to Appendix VIII
E. Plausible Mismanagement Scenario and Other Issues in the
Listing Determination for Waste Solids From the Production of 2,4,6-
Tribromophenol
F. Listing Determination for Wastes From the Production of
Tetrabromobisphenol-A
G. Other Issues
V. Conclusions
VI. Land Disposal Restrictions
A. Treatment Standards for Organobromine Waters
B. Applicable Technology
C. Capacity Analysis Results Summary
VII. Waste Minimization Opportunities in the Industry
VIII. State Program Implementation
A. Applicability of Rules in States
B. Effect on State Authorizations
IX. Compliance and Implementation
A. Section 3010 Notification
B. Compliance Dates for Facilities
X. Listing as CERCLA Hazardous Substances and RQ Adjustment
XI. Regulatory Impact Analysis and Compliance Costs
A. Regulatory Impact Analysis Pursuant to Executive Order 12866
B. Regulatory Flexibility Analysis
XII. Paperwork Reduction Act
XIII. Unfunded Mandates Reform Act
XIV. National Technology Transfer and Advancement Act
XV. Submission to Congress and the General Accounting Office
I. Affected Entities
Entities potentially affected by this action are those which handle
either the waste stream or the chemical being added to EPA's list of
hazardous wastes under RCRA, and to the CERCLA list of hazardous
substances, entities which need to respond to releases of hazardous
substances, states that are required to adopt RCRA hazardous waste
programs. Affected entities include:
------------------------------------------------------------------------
Category Affected entities
------------------------------------------------------------------------
Industry...................................... Generators of the listed
waste solids and filter
cartridges from the
production of 2,4,6-
tribromophenol; or the
product 2,4,6-
tribromophenol, or
entities that treat,
store, transport, or
dispose of these
wastes.
State, Local, Tribal Govt..................... State and Local
Emergency Planning
entities.
Federal Govt.................................. National Response
Center, and any Federal
Agency that handles the
listed waste or
chemical.
------------------------------------------------------------------------
This table is not intended to be exhaustive, but rather provides a
guide for readers regarding entities likely to be affected by this
action. This table lists those entities that EPA now is aware
potentially could be affected by this action. Other entities not listed
in the table also could be affected. To determine whether your facility
is regulated by this action, you should examine 40 CFR parts 260 and
261 carefully in concert with the amended
[[Page 24597]]
rules found at the end of this Federal Register document. If you have
questions regarding the applicability of this action to a particular
entity, consult the person listed in the preceding FOR FURTHER
INFORMATION CONTACT section.
II. Legal Authority
These regulations are promulgated under the Solid Waste Disposal
Act (SWDA), as amended by various other Acts over time. These statutes
are commonly referred to as the Resource Conservation and Recovery Act
(RCRA) and are codified at Volume 42 of the United States Code
(U.S.C.), sections 6901 through 6992k (42 U.S.C. 6901-6992k).
Section 3001(a) of RCRA, 42 U.S.C. 6921(a), requires EPA to
promulgate criteria for identifying characteristics of hazardous wastes
and for listing hazardous wastes. Section 3001(b) of RCRA requires EPA
to promulgate regulations, based on these criteria, identifying and
listing hazardous wastes which shall be subject to the requirements of
RCRA Subtitle C.
Hazardous waste is defined at section 1004(5) of RCRA, 42 U.S.C.
6903(5). There are two types of hazardous waste. First, hazardous
wastes are those solid wastes which may cause or significantly
contribute to an increase in mortality, serious irreversible illness,
or incapacitating reversible illness. In addition, hazardous wastes are
those solid wastes which may pose a substantial present or potential
hazard to human health or the environment when improperly managed.
EPA's regulations establishing criteria for listing hazardous
wastes are codified at volume 40 of the Code of Federal Regulations
(CFR) at Sec. 261.11 (40 CFR 261.11). Section 261.11 states three
criteria for identifying characteristics and for listing wastes as
hazardous.
First, wastes may be classified as ``characteristic'' wastes if
they have the properties described at 40 CFR 261.20 which would cause
them to be classified as having the characteristics of ignitability,
corrosivity, reactivity and toxicity.
Second, wastes may be classified as acute hazardous wastes if they
are fatal to humans at low doses, lethal in animal studies at
particular doses designated in the regulation, or otherwise capable of
causing or significantly contributing to an increase in serious
illness.
Third, wastes may be listed as hazardous if they contain hazardous
constituents identified in appendix VIII of 40 CFR part 261 and the
Agency concludes, after considering eleven factors enumerated in
Sec. 261.11(a)(3), that the waste is capable of posing a substantial
present or potential hazard to human health or the environment when
improperly managed. Under Sec. 261.11(a)(3), a substance is listed in
appendix VIII if it has been ``shown in scientific studies'' to have
toxic effects on life forms.
Wastes listed as hazardous are subject to federal requirements
under RCRA for persons who generate, transport, treat, store or dispose
of such waste. Facilities that must meet the hazard waste treatment,
storage and disposal requirements, including the need to obtain permits
to operate, are commonly referred to as RCRA Subtitle C or ``Subtitle
C'' facilities. Subtitle C is Congress' original statutory designation
for that part of RCRA that directs EPA to issue regulations for
hazardous wastes as may be necessary to protect human health or the
environment. Thus, facilities like incinerators or landfills that are
required to comply with RCRA requirements for hazardous waste are
referred to as Subtitle C incinerators or landfills.
Subtitle C is codified as Subchapter III of Chapter 82 (Solid Waste
Disposal) of Volume 42 of the United States Code, 42 U.S.C. 6921 thru
6939e. EPA standards and procedural regulations implementing subtitle C
are found generally at 40 CFR parts 260 through 272.
Section 3001(e)(2) of RCRA (42 U.S.C. 6921(e)(2)) requires EPA to
determine whether to list, as hazardous, wastes generated by various
chemical production processes, including the production of
organobromines.
Solid wastes which are not hazardous wastes may be disposed of at
facilities which are overseen by state and local governments. These are
the so-called subtitle D facilities. Subtitle D is Congress' original
statutory designation for that part of RCRA which deals with non-
hazardous solid waste.
Subtitle D is codified as Subchapter IV of Chapter 82 (Solid Waste
Disposal) of Volume 42 of the United States Code (42 U.S.C. 6941 thru
6949a). EPA regulations affecting subtitle D facilities are found
generally at 40 CFR parts 240 thru 247, and 255 thru 258.
In response to the mandate on organobromine production wastes in
RCRA section 3001(e)(2), the Agency undertook a two-year study of the
industry and, eventually, listed several wastes from the production of
ethylene dibromide (EDB) and methyl bromide.
The final rule listing wastes from the production of EDB was
published in the Federal Register on February 13, 1986 (51 FR 5327).
These wastes are listed in Title 40 of the Code of Federal Regulations
Sec. 261.32 (40 CFR 261.32) and are designated by EPA hazardous waste
numbers K117, K118, and K136. The final rule listing wastes from methyl
bromide production was published on October 6, 1989 (54 FR 41402).
These wastes are listed at 40 CFR 261.32 and are designated by
hazardous waste codes K131 and K132. Methyl bromide and ethylene
dibromide are also on the Appendix VIII list of hazardous constituents.
In June of 1991, EPA entered into a proposed consent decree in a
lawsuit filed by the Environmental Defense Fund, et al. (EDF v. Reilly,
Civ. No. 89-0598 (D.D.C.)), in which the Agency agreed, among other
things, to publish proposed and final determinations whether to list
wastes from the production of the five other organobromine chemicals
evaluated in this rulemaking.
Under a recently lodged proposed consent order in that case, the
Agency is required to promulgate on or before April 15, 1998 a final
decision on whether or not to list these wastes as hazardous. The
Agency reserves the right to evaluate wastes from the production of
other organobromine compounds in the future, if and when such an
evaluation is deemed necessary.
III. Summary of the Proposed and Final Rules
A. Background Analysis
To provide a sound technical basis for this listing determination,
EPA conducted a study of the organobromine chemicals industry in 1991
and 1992. Six firms were identified as currently manufacturing
organobromine chemicals at eight facilities in the United States. The
majority of organobromine chemicals are currently sold as flame
retardants. Most are solid compounds that are incorporated into
polymers, which are then used in a variety of products. Smaller volumes
of organobromine chemicals are used as reagent chemicals and
pharmaceutical intermediates. Under the authority of RCRA Section 3007,
EPA sent questionnaires to these firms and four of them were selected
for engineering site visits. These four facilities account for over 99
percent of total domestic production. Samples of process residuals were
collected during the site visits to familiarize the Agency with the
types of materials generated by the industry. Later in the study,
record samples to be used as part of the technical basis to decide
whether a listing rule is appropriate were collected at facilities of
the two largest domestic producers. EPA published a proposed rule on
the listing of organobromine
[[Page 24598]]
wastes in the Federal Register on May 11, 1994 (59 FR 24530). The
Listing Background Document for this proposed listing determination
contains a detailed description of the Agency's basis for proposing to
list this waste stream, and for proposing not to list nine other waste
streams; EPA proposed to defer action on one waste. The public version
of this document, which does not contain confidential business
information, can be copied at the RCRA public docket. See ADDRESSES
section.
The third criterion described above for listing hazardous wastes in
40 CFR 261.11, is applicable to the listing of organobromine wastes.
That is, wastes may be listed if they contain hazardous constituents
identified in Appendix VIII of 40 CFR Part 261 and the Agency concludes
the waste is capable of posing a substantial present or potential
hazard to human health or the environment when improperly managed.
With respect to the other two criteria, the wastes under
consideration here are not acutely hazardous. Further,
``characteristic'' wastes, in general, are not listed separately, since
their classification depends upon whether, on a case-by-case basis,
they qualify as wastes based on various tests described in the
regulations. EPA notes that any of the organobromine wastes could be
classified as ``characteristic'' wastes if they ``fail'' the applicable
tests.
B. Summary of Proposed Rule
Consistent with its regulations, EPA, before proposing to list the
organobromine production wastes determined whether there were present
any Appendix VIII constituents and whether there was information on any
other constituents of the waste that could lead to health or
environmental concerns. The health effects data, along with other
factors (generally related to exposure) required to be considered under
40 CFR 261.11(a)(3), were then evaluated to decide whether the wastes
should be listed as hazardous wastes.
In this rulemaking EPA has considered all relevant factors for each
waste stream. The critical factors, which vary depending on the
individual waste stream, were identified in the rulemaking record for
the proposal and are summarized at 59 FR 24536 to 24541. The record for
this rule contains responses to all comments submitted on the relevant
factors.
EPA proposed not to list as hazardous nine waste streams from the
production of organobromine compounds. The Agency also proposed to
defer action on the listing determination for one waste stream from the
manufacture of tetrabromobisphenol A (TBBPA) because of inadequate
information on the process. In the proposal the Agency stated, ``Based
on comments received, including any data, EPA may choose, rather than
deferring, to promulgate a final determination either to list or not to
list tetrabromobisphenol A waste as a hazardous waste under RCRA'' (59
FR 24537).
EPA proposed to list as hazardous one waste stream from the
production of 2,4,6-tribromophenol (2,4,6-TBP). The listing of this
waste, as noted above, required consideration of whether an Appendix
VIII constituent was present. While none of the constituents had been
listed in Appendix VIII at the time of proposal, EPA did consider that
the 2,4,6-tribromophenol present in the waste would likely qualify for
Appendix VIII listing. Accordingly, along with the proposed hazardous
waste listing, EPA proposed to include 2,4,6-tribromophenol in Appendix
VIII.
The proposed addition to Appendix VIII is discussed at 59 FR 24531
and 24538. While EPA did not have a laboratory study directly showing
that 2,4,6-tribromophenol has toxic effects on life forms, the Agency
explored the use of structure-activity relationships to determine
whether, nevertheless, there are other types of scientific studies that
could indirectly show that this compound has toxic effects and,
thereby, qualify for listing on Appendix VIII under 40 CFR
261.11(a)(3). Structure-activity relationships involve the use of
health effects information for a compound with a chemical structure and
properties very similar to those of the chemical of concern. The Agency
determined that this technique could be used for 2,4,6-tribromophenol
because the chemical behavior and mechanism of action for this compound
is expected to be similar to its chlorinated analogue, 2,4,6-
trichlorophenol.
After considering the data supporting the Appendix VIII listing
determination and factors under 40 CFR 261.11(a)(3), EPA proposed to
list as hazardous waste solids and filter cartridges from the
production of 2,4,6-tribromophenol and designate it as K140. These
waste solids consisted of floor sweepings and off-specification product
from the production of 2,4,6-tribromophenol. EPA also proposed to add
2,4,6-tribromophenol to the list of commercial chemical products (as
U408) that are hazardous wastes if discarded (40 CFR 261.33).
Under section 102(b) of CERCLA, all hazardous wastes newly listed
under CERCLA have statutory reportable quantities (RQs) of one pound
unless and until adjusted by regulation. Waste U408 is 2,4,6-
tribromophenol, an individual hazardous substance. Based on its
evaluation, the Agency proposed an adjusted RQ of 100 pounds for 2,4,6-
tribromophenol.
The only hazardous constituent identified in the other waste
proposed for listing, K140, is 2,4,6-tribromophenol. In accordance with
the RQ adjustment methodology for hazardous waste streams, the RQ for
K140 is being adjusted to 100 pounds based on the 100 pound RQ of its
only hazardous constituent, 2,4,6-tribromophenol.
C. Additional Opportunities To Comment
In the original listing determination, EPA presumed that the
plausible management scenario for the 2,4,6-tribromophenol waste solids
was disposal in an unlined landfill. This was critical in the Agency's
determining that the waste presented a substantial risk. However,
comments on the rule by the only manufacturer of 2,4,6-tribromophenol
showed that these wastes had been sent voluntarily, over a period of
more than fifteen years, to a number of different Subtitle C landfills.
Accordingly, EPA reevaluated the management scenario to comport with
the actual Subtitle C disposal scenarios.
Since EPA's reexamination evaluated information not previously
placed in the record, the Agency provided notice of this new
information and its reevaluation in a letter dated September 3, 1997.
This letter, sent to three commenters on the original proposal who were
expected to have a direct interest in the listing of the particular
waste, added additional information to the rulemaking record and
explained the Agency's new rationale for listing the 2,4,6-
tribromophenol waste solids.
EPA received comments from the three entities that received the
notice letter. One commenter supported the decision to list 2,4,6-TBP
production wastes, and two opposed the listing. The substance of the
September 3 letter and EPA's response to the comments appears below in
Unit IV.E. The Unit IV.E. deals with response to comments on the
plausible mismanagement scenario for the 2,4,6-tribromophenol waste
solids.
The commenter supporting the listing decision also argued that EPA
underestimated the risks posed by disposal of the 2,4,6-TBP waste in a
Subtitle C landfill, because EPA had ignored the presence of other
toxic contaminants in the waste. The Agency reexamined the analytical
data for the waste samples from the 2,4,6-tribromophenol production
waste.
[[Page 24599]]
Based on that reexamination, EPA found that the waste contained another
toxic constituent (ethylene dibromide) that appeared to further support
the listing. EPA provided additional notice of this additional
constituent to the interested party that is the sole generator of the
waste in a letter dated January 14, 1998. The generator submitted
comments on this second notice letter, and Unit IV.E also discusses the
Agency's responses to these comments.
D. Final Rule
The final rule promulgated today is based on consideration of all
comments submitted on the proposed rule, including those submitted in
response to the reevaluation in the September 3 letter, and all
relevant information available in the rulemaking record. Today's rule
issues the final listing for 2,4,6-tribromophenol as a hazardous
constituent in Appendix VIII of 40 CFR part 261, promulgates the
listing of floor sweeping, off-specification product and spent filter
media from the production of 2,4,6-tribromophenol as hazardous waste
K140 (40 CFR 261.32) and lists the 2,4,6-tribromophenol commercial
chemical product as a hazardous waste when discarded, with a waste code
of U408 (40 CFR 261.33 (f)). These listings are based on the presence
in the waste of 2,4,6-tribromophenol. EPA also has determined not to
list any of the other wastes described in the proposed rule, including
wastes from the production of tetrabromobisphenol A, on which the
Agency had originally proposed to defer a final decision.
Also included in today's final rule, the Agency is adding 2,4,6-
tribromophenol and K140 to the list of CERCLA hazardous substances in
Table 302.4 of 40 CFR 302.4. CERCLA defines the term ``hazardous
substance'' chiefly by reference to various Federal environmental
statutes. For example, the term includes ``any hazardous waste having
the characteristics identified under or listed pursuant to RCRA Section
3001.'' Thus, on the effective date of today's rulemaking, when 2,4,6-
tribromophenol and K140 are added as RCRA hazardous wastes, these
wastes automatically become CERCLA hazardous substances. In today's
final rule, EPA also is adjusting the reportable quantities (RQs) for
2,4,6-tribromophenol (U408) and K140 to 100 pounds in Table 302.4 of 40
CFR part 302.
In the subsequent sections of today's notice, EPA responds to
public comments received on the proposal and on the reevaluations and
provides its reasons for changing the final rule from proposal or
declining to make changes suggested by commenters. Table 1 summarizes
the basis for the listing determinations.
Table 1.--Basis for Listing Determinations
----------------------------------------------------------------------------------------------------------------
Product Waste stream Analysis Decision
----------------------------------------------------------------------------------------------------------------
Dibromomethane..................... Filters............... Very small volume (less No List.
than 1 kkg/yr) One
producer.
Wastewaters........... Deep-well injected at site No List.
with approved no-migration
petition (only one
producer).
Ethyl Bromide...................... Filters............... Very small volume stream No List.
(less than 1.5 kkg/yr).
Wastewaters........... Only constituent identified No List.
is ethanol at low
concentration.
Tetrabromobisphenol A.............. Wastewaters........... Stream is already listed as Already listed waste.
K131 for methyl bromide.
Also contains 15,000 ppm
tribromophenol.
Octabromodiphenyl oxide............ Filter cake........... Toluene and brominated No list.
dibenzofurans present at
levels below concern.
Assuming worst case for
leachate, risk for the
maximally exposed
individual estimated to be
below 10-6 for
octabromodiphenyl oxide.
Wastewaters........... Major constituent of No list.
concern, brominated
dibenzofurans, shows
minimal risk; solubility
of octabromodiphenyl oxide
is very low; modeling of
worst case for wastewaters
showed risk below 10-6 for
octabromodiphenyl oxide.
Decabromodiphenyl oxide............ Filter cake........... The major constituent in No list.
waste (decabromodiphenyl
oxide) could not be
quantified. Assuming worst
case for leachate, risk
below 10-6 level because
of very low solubility for
this chemical.
Wastewaters........... The major constituent in No list.
waste (decabromodiphenyl
oxide) could not be
quantified. Assuming worst
case for leachate, risk
below 10-6 level because
of very low solubility.
Tetrabromobisphenol A.............. Off-specification Tetrabromobisphenol A is of No list.
product. relatively low toxicity
and has limited mobility.
Levels of tribromophenol
in leachate are below
those for concern.
Tribromophenol..................... Wastewaters........... Used structure activity No list.
relationship analysis for
tribromophenol. Data
collected indicate
releases during deep-well
injection are not likely
to occur or would be of
low risk. Tribromophenol
not detected in
groundwater at site.
[[Page 24600]]
Floor sweepings, off- Used structure activity List as hazardous
specification product relationship analysis to waste (K140) and
and spent filter show carcinogenicity of commercial chemical
media from the tribromophenol. High product (U408).
production of 2,4,6- concentration of chemical
tribromophenol; in solids and TCLP
discarded commercial leachate. Mobile in
chemical product. leachate and would present
high risk if released from
landfill, even a Subtitle
C landfill.
----------------------------------------------------------------------------------------------------------------
IV. Response to Comments
Seven parties submitted comments on the proposed rulemaking.
Comments were received from two companies that manufacture bromine
products, one trade association representing industrial chemical
producers, two manufacturers of chemical products other than bromines,
one company involved in the treatment and destruction of hazardous and
toxic wastes, and one environmental interest group. The major issue
addressed by commenters to the original proposal was the Agency's use
of structure-activity relationship (SAR) analysis to support a listing
determination. The major issue addressed with respect to the September
3 reevaluation was on EPA's use of Subtitle C landfills as a
mismanagement scenario for modeling purposes and the assessment of risk
relating to Subtitle C landfills. EPA also discusses the January 14,
1998 reevaluation of additional constituents found in the 2,4,6-TBP
production wastes. More detailed summaries of the comments and complete
Agency responses are provided in the Public Comment Summary & Response
Document and the Supplementary Comment Summary & Response Document
prepared for comments on the September 3, 1997, and January 14, 1998
letters. These documents are included as appendices to the Listing
Background Document supporting today's rule (available in the public
docket--see ADDRESSES section).
Before addressing the public comments in detail, some of the basic
concepts related to the use of SAR analysis for this rulemaking are
addressed here.
A. Development of Structure-Activity Relationship (SAR) Analyses
1. Principles Related to SAR Analyses
In the preamble to the proposed rule, EPA briefly discussed the
basis for using SAR analyses for regulatory purposes. The scientific
process used in SAR analysis also was presented in Development of
Provisional Human Health Reference Value for 2,4,6-Tribromophenol and
the Listing Background Document for the proposed listing (henceforth
collectively termed ``the Listing Background Document.'') SAR analyses
are based on the observation that structurally similar compounds have
similar chemical properties. Thus, they may be absorbed, distributed,
and metabolized in similar ways, and may have similar mechanisms of
action and toxic properties. If two compounds or a group of compounds
are chemically related, toxicologic data for one or more compounds in
the group can be used to predict the toxicologic effects of other
compounds in the group. The more closely related two compounds are, the
more similar their toxic properties are likely to be.
The validity of SAR analysis is related to the degree of similarity
of the candidate (the compound for which adequate toxicity information
are lacking) and the surrogate (the chemical used as the basis for the
analysis), and the amount of information available on how any
differences between the two chemicals affects their activity. Because
chemical similarity plays a critical role in SAR analysis, this
discussion begins with a brief primer on chemical structure.
The periodic table of the elements arranges elements in order of
increasing atomic number, in a manner that shows their chemical
relatedness. Elements that are in the same column on the periodic table
have the same number of electrons in their outer shell, and are
chemically similar. Elements that lack one electron in their outer
shell are in the same column, and are called halogens. This group
includes fluorine, chlorine, bromine, and iodine, which react in
chemically similar ways. Bromine and chlorine are the most similar
halogens; fluorine binds to carbon much more strongly than do chlorine
or bromine, while the reactivity of iodine is also influenced by its
larger size. When chemical groups replace the hydrogen atoms in organic
(carbon-containing) molecules, the molecules are called
``substituted.'' The chemical groups that do the substituting are
called ``substituents,'' and play a large role in determining the
chemical reactivity of the compound.
Figure 1 compares the structures of the two compounds studied in
the SAR analysis, and shows the structure of the parent compound,
phenol. 2,4,6-Trichlorophenol (TCP) is phenol with chlorine
substitution at the 2-, 4-, and 6-positions. Similarly, 2,4,6-
tribromophenol (TBP) is phenol with bromine substitution at the 2-, 4-,
and 6-positions. Thus, the two compounds are phenols substituted with
closely related halogens at the same positions. Note that both the
position and number of substitutions are the same in the two compounds.
If the two compounds were substituted by different numbers of halogen
atoms, or at different positions from each other, they would be
expected to be less similar chemically and physically. This is because
both the type and location of the substitution contribute to the
electronic, steric, and other attributes of the molecule.1
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\1\ Waser J., N. Trueblood, and C. M. Knobler. 1976. Chem One.
New York, NY: McGraw-Hill pp. 25-29.
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2. Structure-Activity Relationship Analysis
In the proposed rule, EPA developed a Quantitative SAR (QSAR)
analysis for 2,4,6-TBP using 2,4,6-TCP as the surrogate, and attempting
to adjust the cancer slope factor based on the closely-related
electronic properties of bromine and chlorine. However, EPA received a
number of comments stating that this analysis was too oversimplified to
be reliable. In particular, commenters stated that additional
parameters should be used in such an analysis. It was suggested that
data on hydrophobicity (a description of the degree to which a compound
repels water) and steric effects be incorporated into the analysis.
Information on the hydrophobicity of a molecule is relevant to
understanding how a molecule distributes in the body (e.g., fatty
tissues versus blood), whether it accumulates in the fat, and the ease
or difficulty with which the molecule may move across cell membranes to
its site of action. This attribute of a molecule is often expressed as
the octanol-water partition coefficient, which quantitatively indicates
the degree to which the compound partitions to either water or lipid
materials. The water solubility of a molecule, i.e., the amount that
will dissolve in pure water, also influences the octanol-water
partition coefficient. Steric (spatial) effects, which are caused by
the different orientation of atoms in space relative to each other, are
important because they provide information on whether the molecule's
size and shape allow it to interact with receptors in biological
systems, such as enzymes, hormones, and genetic material.
EPA has re-evaluated the SAR analysis in light of these comments,
and agrees that additional parameters could have been considered;
however, available data are insufficient to adequately account for
these additional parameters. Despite the lack of adequate information
to evaluate all parameters affecting the relative toxicity of 2,4,6-TCP
and 2,4,6-TBP, the Agency believes that these compounds are so similar
that it is appropriate to use the 2,4,6-TCP slope factor as an
estimated slope factor for 2,4,6-TBP. Many of the toxicological
similarities are discussed further in the following sections. In
addition, the very factors suggested by comments for consideration, as
noted above, provide a further basis for showing how these two
chemicals are closely related. For example, when the Agency adjusted
the slope factor for electronic effects, the change was less than 1%.
Also, a key measure of hydrophobicity, the log of the octanol-water
partition coefficients (log Kow), is similar for these two
chemicals; the values of log Kow are 4.23 for 2,4,6-TBP and
3.69 for 2,4,6-TCP. All of these factors lead the Agency to conclude
that 2,4,6-TCP can be used as a direct surrogate for 2,4,6-TBP.
3. 2,4,6-TBP Slope Factor and Risk Estimate
Although EPA is using the 2,4,6-TCP cancer slope factor as a
default for 2,4,6-TBP, the Agency examined the impact of modifying the
cancer slope factor in response to public and favorable peer reviewer
comment, to account for the difference in molecular weight of 2,4,6-TCP
and 2,4,6-TBP.
The molecular weight of a compound is the weight in grams of a
specified number (a mole) of molecules of that compound, and is used to
convert between the weight of a sample of a compound and a measure of
the number of molecules in that sample.2 Because a bromine
atom is heavier than a chlorine atom, one gram of 2,4,6-TBP has fewer
molecules in it than does a gram of 2,4,6-TCP, and therefore a gram of
2,4,6-TBP would be less potent than a gram of 2,4,6-TCP, all other
things being equal. This is because chemically-induced cancer results
from molecules binding to DNA or to another molecule in the
body,3 and, therefore, a compound's cancer potency is
related most directly to the number of molecules administered (rather
than the weight alone). As a result, the 2,4,6-TCP slope factor may be
multiplied by the
[[Page 24602]]
ratio of the 2,4,6-TCP molecular weight (197) to the 2,4,6-TBP
molecular weight (331). Adjusting for molecular weight would result in
a default value for the 2,4,6-TBP CSF of 6.5 x 10-3 (mg/kg/
day)-1, compared with 1.1 x 10-2 (mg/kg/
day)-1 for 2,4,6-TCP. If this slope factor were applied in a
risk analysis in the preamble to the proposed rule, it would have
little effect on results. Using the corrected cancer risk factor, the
estimated individual risk from exposure to 2,4,6-TBP in groundwater
would be 4.2 x 10-4 and 1.2 x 10-5 for the off-
specification product and the filter cartridges, respectively, compared
with risks of 7 x 10-4 and 2 x 10-5 calculated
without the correction in the proposed rule. These changes are minor
and would not change the Agency's decision, i.e., the risks posed by
these wastes warrant control through listing.
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\2\ Waser, J., K.N. Trueblood, and C.M. Knobler. 1976. Chem One.
New York, NY: McGraw-Hill pp. 25-29.
\3\ William, G.M. and J.H. Weisburger. 1991. Chemical
carcinogenesis. In: Amdur, M.O., J. Doull, and C.D. Klaassen.
Casarett and Doull's Toxicology: The Basic Science of Poisons, 4th
ed. New York, NY: Pergamon Press. pp. 127-200.
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4. Notice and Comment for the Use of an SAR
To check its analysis, EPA subjected it to both internal Agency
review and external peer review. External peer review was solicited on
a draft of the Public Comment Summary & Response Document. As
background, the peer reviewers were provided the risk assessment
section of the Listing Background Document for the proposal and the
public comments on that part of the proposal. Three individuals with
experience in SAR analyses were asked: (1) Is the SAR presented for
2,4,6-TBP sufficiently rigorous to be scientifically defensible and
could the reviewers identify major areas of uncertainty with the
analysis? (2) Is it appropriate for the Agency to conclude that 2,4,6-
TCP and 2,4,6-TBP are similar and is 2,4,6-TCP an appropriate surrogate
for 2,4,6-TBP? (3) Was all of the available information about the
mechanism of toxicity for 2,4,6-TBP considered? (4) Is there any
genetic toxicity data that could be included in the analysis? and (5)
Could any additional information be provided to strengthen the Agency's
conclusions?
All three peer reviewers agreed that a SAR analysis was appropriate
for this rule. Additionally, the peer reviewers agreed that 2,4,6-TCP
is the most appropriate surrogate for 2,4,6-TBP, and that it is
appropriate to use the cancer potency factor for 2,4,6-TCP as a default
value for 2,4,6-TBP. (One commenter also suggested that the potency
factors be adjusted for the differences in molecular weight. This
confirmed EPA's analysis. EPA has addressed the substantive technical
issues raised by the commenters in a detailed memorandum to the file,
which is in the docket.
B. Why the SAR Analysis of 2,4,6-TCP and 2,4,6-TBP Constitutes a
Scientific Study That Shows Toxic Effects
1. Why This Is a Scientific Study
Although EPA usually uses controlled animal studies or
epidemiological studies of human exposure as the basis for its
regulations, 40 CFR 261.11(a)(3) does not preclude the use of other
types of scientific studies. Moreover, EPA's interpretation of its own
regulations to include SAR analysis as a scientific study is entitled
to substantial deference.
SAR analysis is interpreted by EPA to be a scientific study. The
scientific principles on which SAR analyses are based were developed
from many years of chemical review and analysis and, more recently,
toxicity studies on related compounds. For example, the SAR analysis
for 2,4,6-BP rests not only on the chemical similarity of 2,4,6-TBP and
2,4,6-TCP, but also on toxicity studies showing structurally similar
brominated and chlorinated compounds to be related in terms of whether
they are carcinogens. These studies are discussed in more detail in
Section III.C.3. of this preamble.
EPA has, in the past, relied on scientific studies in the form of
sophisticated statistical analyses that are one step removed from a
laboratory study much in the same way SAR analysis is. In addition, EPA
has used meta-analyses, a statistical tool for combining the data from
multiple studies, in several risk assessments, including the risk
assessment for environmental tobacco smoke.4
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\4\ USEPA. 1992. Respiratory health effects of passive smoking:
Lung cancer and other disorders. ORD, USEPA, Washington DC, 20460.
EPA/600/6-90/006F.
---------------------------------------------------------------------------
Furthermore, the controlled animal studies performed on 2,4,6-TCP
are indisputably scientific studies and these studies, with the aid of
SAR analysis, show that 2,4,6-TBP is a potential carcinogen, as
discussed below.
2. Does It ``Show'' Toxic Effects?
Section 40 CFR 260.11(a)(3) does not specify that EPA must conduct
laboratory studies that directly implicate the precise chemical. In
this case, the finding that 2,4,6-TCP is carcinogenic in animal
studies, together with the SAR analysis demonstrating the close
chemical similarity of 2,4,6-TCP and 2,4,6-TBP, shows that 2,4,6-TBP is
expected to be carcinogenic because they provide a sound basis for EPA
to infer the toxic effects of 2, 4, 6-TBP from the toxic effects
demonstrated for 2,4,6-TCP, as noted below.
It also is important to recognize that all scientific studies that
actually measure toxic effects in a laboratory have some level of
uncertainty when used as the basis for regulatory action. Uncertainty
is caused by:
a. Extrapolation from animal models to humans;
b. Variable responses among animals within a study;
c. Statistical variability of results between different studies
(i.e., if the experiment were to be repeated, one would not necessarily
observe exactly the same tumor incidences);
d. Extrapolation from high laboratory doses to low actual human
exposures; and
e. Extrapolation to humans from studies in animals that live for a
fraction of the human life span.
Uncertainty in carcinogen assessment is discussed in detail in
EPA's Proposed Guidelines for Carcinogen Risk Assessment, and articles
cited therein.5
---------------------------------------------------------------------------
\5\ Proposed Guidelines for Carcinogen Risk Assessment. Federal
Register 61(79): 17960-18011, Tuesday, April 23, 1996.
---------------------------------------------------------------------------
From a scientific perspective it is impossible to ``show'' anything
without some uncertainty. Therefore, EPA interprets the language of the
regulation as a requirement to ``show'' with a scientifically
reasonable level of uncertainty. In this case, the level of uncertainty
associated with this particular SAR is reasonable for the two chemicals
being compared in this rulemaking because:
2,4,6-TBP and 2,4,6-TCP are both tri-halogenated phenols
with substitutions at the same positions;
The physical and chemical properties, such as the octanol-
water partition coefficient and the water solubility, of the compounds
are similar;
Available genetic toxicity data show consistent results
for 2,4,6-TCP and 2,4,6-TBP; and
Examples in the literature and in Section C.3 of this
preamble (e.g., 1,2-dibromoethane and 1,2-dichloroethane) support the
idea that if a chlorinated compound is a carcinogen, the compound
formed by substitution of a chlorine with bromine will still be a
carcinogen.
Some commenters provided examples of chemical pairs where SAR
analysis would be inappropriate, such as benzene/toluene and methanol/
ethanol (see Figure 2 and the accompanying text for a further
discussion of these chemicals). EPA agrees that for these pairs, a SAR
analysis should not be used for regulatory purposes. However, the data
support a conclusion that the structural and chemical similarities
[[Page 24603]]
between 2,4,6-TBP and 2,4,6-TCP are much stronger than those in the
pairs in Figure 2, and thus the uncertainty for the current rulemaking
is much less than the uncertainty/error would be for a SAR analysis for
any of the chemical pairs in the counter example. EPA has determined
that these data support the regulation of 2,4,6-TBP under RCRA, because
they reasonably support a conclusion that 2,4,6-TBP has a level of
carcinogenicity comparable to that of 2,4,6-TCP, a known carcinogen.
C. Issues Regarding the Use of Structure-Activity Relationship (SAR)
Analysis
1. Use of SARs to Support Listing Constituents in Appendix VIII
All seven commenters addressed the use of structure-activity
relationships (QSARs) in this rulemaking. Two commenters stated that
SAR analysis cannot be used to support listing a constituent in
Appendix VIII, citing the language of 40 CFR 261.11(a)(3), which states
that constituents may be listed in Appendix VIII ``only if they have
been shown in scientific studies to have toxic, carcinogenic,
mutagenic, or teratogenic effects on humans or other life forms.'' The
commenters stated that SARs are not equivalent to empirical data, do
not represent ``scientific studies'' and do not show that 2,4,6-
tribromophenol has toxic effects on life forms. Therefore, the
commenters stated that information on structure-activity relationships
cannot be used to list constituents in Appendix VIII and, consequently,
may not be used to list hazardous wastes under EPA's regulation.
EPA disagrees with the commenters. The commenters interpret ``shown
in scientific studies'' to mean directly shown in laboratory studies
that pertain to the constituent in question. EPA does not interpret the
phrase so narrowly. SAR analysis represents a valid scientific approach
for assessing toxicity. As noted above, EPA has concluded that there is
sufficient similarity between 2,4,6-TBP and 2,4,6-TCP to justify using
a SAR analysis for this rulemaking.
EPA's use of SAR analysis in regulatory programs is not
unprecedented. EPA has used SAR analysis for assessing the hazards of
chemicals to human health and the environment for 15 years in the New
Chemicals Program under section 5 of TSCA. The process of using SAR
takes into account the similarity of the surrogate chemicals with
regard not only to chemical structure and functional reactive groups,
but physical/chemical properties as well (e.g., water solubility and
octanol/water partition coefficients). Physical/chemical properties
such as water solubility and octanol/water partition coefficients are
important because they are related to how a compound is absorbed and
distributed in the body. In particular, the octanol/water partition
coefficient is a measure of a compound's relative solubility in octanol
and water, and is related to how well a compound dissolves in fat
versus the blood. The octanol/water partition coefficient describes a
compound's hydrophobicity, which was mentioned in Section III.A.2. of
this preamble. In cases where direct chemical-specific toxicity data
are lacking and where appropriate analogue chemicals exist to allow
valid comparisons to be drawn, SAR analysis represents a scientifically
valid approach for assessing the potential toxicity of a chemical. As
discussed in Section III.B. of this preamble, EPA regards SAR as
``scientific studies'' and believes that the SAR analysis conducted for
this rulemaking does ``show'' toxic effects of 2,4,6-TBP sufficiently
to support its listing in Appendix VIII.
2. Use of SARs Is a Departure From Agency Policy
Two commenters stated that the use of SAR analysis in this
rulemaking represents a departure from Agency policy. The commenters
added that the use of SARs in making hazardous waste determinations
establishes a new criterion for identifying hazardous wastes and the
public was not given sufficient opportunity to comment on this new
criterion.
The Agency agrees that this listing represents a new element in the
Agency's hazardous waste listing determination policy in that this is
the first listing to use SAR as a basis for listing a waste stream as
hazardous. However, the SAR analysis is consistent with 40 CFR
260.11(a)(3) of EPA's regulations, since EPA's decision to list a
constituent in Appendix VIII makes use of a scientific study that shows
the toxic effects of that constituent. There has been adequate
opportunity to comment on this issue, since the Agency explained in the
proposal that it was interpreting 40 CFR 260.11(a)(3) to allow use of
structure-activity relationships. Indeed, the bulk of comments on the
proposed rule dealt with the highly technical issue of whether SAR
could be used to list hazardous wastes. This is a strong indication
that commenters understood that they were being given the opportunity
to express their views on this matter. EPA takes the position that,
depending on the strength of the evidence, SAR-based listings are
appropriate to use for the hazardous waste listings program. SAR is an
available tool that can solve a problem the Agency faces in the case:
Making risk-based regulatory decisions (such as listing determinations)
in the absence of Agency-verified or provisional health benchmarks
(e.g., reference dose (RfD), reference concentration (RfC), or cancer
slope factor (CSF).
As described in further detail in other places in this preamble,
the evidence in this case rests on four points: 2,4,6-TCP is a close
structural analogue to 2,4,6-TBP; the physical and chemical properties
of the compounds are similar; the available genetic toxicity data also
show consistent results for 2,4,6-TCP and 2,4,6-TBP; and examples in
the literature support the idea that if a chlorinated compound is a
carcinogen, the compound formed by substitution of a chlorine with
bromine will still be a carcinogen.
SAR is one approach that was designed specifically to address this
problem. The use of SAR is particularly compelling in the
organobromines listing determination. The constituent 2,4,6-TBP has an
extremely close structural analogue (2,4,6-TCP) for which direct
toxicity data are available. Because of this, the Agency specifically
solicited comment on the policy implications of the use of QSAR/SAR in
the organobromines proposal.
The Agency has concluded that SAR currently is a viable approach
for making a human health impact determination for the waste stream of
concern. The strong technical argument involved, that the principal
toxicant of concern, 2,4,6-TBP, is a highly similar analogue of 2,4,6-
TCP, makes this listing the appropriate place to use SAR. It is
important to note, however, that the determination to list 2,4,6-TBP-
containing residuals as hazardous wastes is not based solely on the SAR
analysis for 2,4,6-TBP. Other factors were included in the risk
assessment, including the concentrations of 2,4,6-TBP in the waste, the
volumes of waste generated, the mobility of the 2,4,6-TBP in leachate
tests of the waste, plausible mismanagement scenarios, and potential
receptors.
3. Validity of SAR Analysis in Supporting the Hazardous Waste Listing
Determination for 2,4,6-TBP Production Wastes
All seven commenters addressed the general validity of the SAR
analysis employed in this rulemaking. One commenter supported the
Agency's use
[[Page 24604]]
of SARs and the inference that 2,4,6-TBP and 2,4,6-TCP are similar, but
the other six commenters raised scientific and procedural concerns
related to the use of SAR analysis to support a listing determination.
Some of the comments were specific to the SAR analysis in the proposed
rule. Specifically, two commenters objected to the analysis being based
on electronic effects alone, instead of also considering hydrophobic
and steric effects. Other comments addressed the general aspects of the
analysis, i.e., the appropriateness of 2,4,6-TCP as a surrogate for
2,4,6-TBP. In light of the quantitative uncertainties raised and other
issues, the Agency believes that a SAR analysis does show that 2,4,6-
TCP is an appropriate surrogate for 2,4,6-TBP, based on their high
degree of structural similarity, i.e., both are tri-substituted phenols
with the closely-related halogens chlorine (2,4,6-TCP) or bromine
(2,4,6-TBP) located at the 2-, 4-, 6-positions (see Section A1. for a
more detailed discussion of the structural similarity between 2,4,6-TBP
and 2,4,6-TCP).
As mentioned in Section III.A.3., the Agency is adopting one
quantitative manipulation suggested by both a commenter and a peer
reviewer. They noted that the differing molecular weights of the two
compounds should be taken into account in the slope factor projection;
this change has been adopted. When making this adjustment, however, the
Agency found that the change would not exert a significant change in
the risk results (i.e., a 40% decrease in risk). Even if EPA made the
change, the risk would still warrant listing.
As part of the support for SAR analysis, this discussion summarizes
the available data related to the carcinogenic activity of 2,4,6-TCP
and the genetic toxicity of 2,4,6-TCP and 2,4,6-TBP. 2,4,6-TCP
carcinogenicity was tested in mice and rats. Based on the results of
this study, 2,4,6-TCP is classified as a probable human carcinogen
(B2), and the CSF for 2,4,6-TCP was calculated based on leukemia in
male rats. No long-term animal studies that could detect cancer have
been conducted with 2,4,6-TBP.
Results from short-term genetic toxicity studies, such as those
described in the following paragraphs, provide information on whether
the compound of interest interacts with DNA and causes mutations or
other DNA damage, such as chromosome aberrations. These data are used
to predict whether a compound is likely to be carcinogenic, and to help
interpret results of cancer assays in animals. A variety of different
genetic toxicity tests commonly are used. Because no single test can
detect all types of damage, a battery of tests is necessary to assess
completely a compound's potential to cause DNA damage. Findings in
mammalian cells generally are considered more relevant than findings in
bacterial cells. For 2,4,6-TCP, genetic toxicity studies appear to
indicate that 2,4,6-TCP is positive in mammalian cell gene mutation
assays, and negative in a bacterial (Salmonella typhimurium) mutation
assay and in a mammalian cell chromosome aberration assay. Genetic
toxicity data for 2,4,6-TBP are limited to a negative result in a S.
typhimurium gene mutation assay.6 Although this single
negative result might appear to predict that 2,4,6-TBP is not
carcinogenic, 2,4,6-TCP also produced negative results in this
bacterial assay,7 but is carcinogenic in rats. Therefore,
the S. typhimurium gene mutation assay does not appear to accurately
predict whether this class of compounds is carcinogenic.
---------------------------------------------------------------------------
\6\ Zieger, E., B. Anderson, S. Halworth, T. Lawlor, K.
Mortelmans, and W. Speck. 1987. Salmonella mutagenicity tests. III.
Results from the testing of 225 chemicals. Environ Mutagen 9 (Suppl.
9) 1-109. As cited in Docket #F-94-OBLP-S0013.
\7\ Haworth, S., T. Lawlor, K. Mortelmans, W. Speck, and E.
Zeiger. 1983. Salmonella mutagenicity test result for 250 chemicals.
Environ Mutagen Suppl 1:3-142.
Rasanen, L., M. L. Hattula, and A. U. Arstila. 1977. The
mutagenicity of MCPA and its soil metabolities, chlorinated phenols,
catechols and some widley used slimicides in Finland. Bull Environ
Contam Toxicol 18:565-571.
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One commenter believed that the analysis should have compared
2,4,6-TBP to an entire class of compounds rather than to a single
chemical compound. The Agency believes that comparison with a single
compound is acceptable for SAR analysis in cases such as this, when the
structural similarities between the two compounds are so strong.
Comparisons across multiple chemicals are needed for larger structural
differences. This commenter also stated that the QSAR/SAR analysis
disregarded documented differences between the carcinogenicity of
chlorinated and brominated analogues. For example, the commenter noted
differences in the species and tissue (e.g., kidney or liver) in which
tumors develop following administration of trihalomethanes ranging from
chloroform (CHCl3) to bromoform (CHBr3). The
compounds in the series represent a series of replacements of chlorine
atoms by bromine atoms (i.e., 3 chlorines; 2 chlorines and 1 bromine;
etc.).
Because the trihalomethanes are such small molecules, the three
halogen atoms constitute a relatively large percentage of the total
volume of the molecule. Thus, substituting bromine for chlorine would
be expected to have a larger effect than the same substitution in the
large 2,4,6-TCP/2,4,6-TBP molecules. This difference in size may
explain the observed differences in target organs among the
trihalomethanes. An important point to note is that all four
trihalomethanes are carcinogens, regardless of the target tissue.
Regarding the issue of the appropriateness of SAR analyses based on
analogues in which a chlorine is substituted by a bromine, the Agency
notes that there are additional well-studied examples in which
substitution of a chlorine by a bromine has resulted in retention of
carcinogenic activity. For example, both 1,2-dichloroethane (ethylene
dichloride) 8 and 1,2-dibromoethane (ethylene dibromide)
9 are multi-target carcinogens, causing tumors in the lung,
the forestomach, the circulatory system, and the mammary gland. The
Agency recognizes that examples of bromine/chlorine substitutions in
which both the chlorinated analogue and the brominated analogue are
carcinogens are not sufficient to show that such substitutions in
general will not change a carcinogen into a noncarcinogen. However,
based on these examples and in light of the carcinogenicity of 2,4,6-
TCP in animal testing, it is plausible to conclude that 2,4,6-TBP is a
potential carcinogen. (For a more detailed discussion of many of the
scientific bases underlying SAR and the rationale behind the selection
of cancer as the endpoint for human exposure, see the Response to
Public Comment Document for this rulemaking, in the public docket.)
---------------------------------------------------------------------------
\8\ NCI. 1978. Bioassay of 1,2-dichloroethane for possible
carcinogenicity. National Cancer Institute, Bethesda Maryland. NCI-
CG-TR No. 66; DHEW/PUB/NIH-78-1361.
\9\ NTP. 1982. Carcinogenesis bioassay of 1,2-dibromoethane for
possible carcinogenicity F344 rats and B6C3F1 mice. U.S.
National Toxicology Program, Research Triangle Park, North Carolina.
NTP-TR No. 210; NIH/PUB 87-1766.
---------------------------------------------------------------------------
One commenter expressed concerns that the use of SAR analyses to
make predictions of the expected types of toxicity produced by a
compound can result in erroneous predictions. The commenter illustrated
the point by providing several cases (e.g., benzene/toluene, methanol/
ethanol, methyl n-butyl ketone/methyl isobutyl ketone (MnBK/MIBK)) in
which predictive errors would occur based on SAR analysis performed
with structurally similar chemicals. The Agency recognizes the
limitations to SAR
[[Page 24605]]
analysis and agrees that the choice of surrogate needs to carefully
take into account the degree of similarity between the chemical of
interest (the ``candidate'') and the surrogate (from which predictions
are made). The structural and chemical similarities between 2,4,6-TCP
and 2,4,6-TBP are greater than those in the pairs cited by the
commenter. Both 2,4,6-TBP and 2,4,6-TCP consist of a phenol molecule
with halogen substitutions at the 2-, 4-, and 6-positions,
and differ only in the identity of the halogen. As shown in Figure 2,
the differences in the pairs listed by the commenter are much larger.
The pairs cited by the commenter differ in having/not having a
substituent group (benzene/toluene), or are positional isomers (1-/2-
naphthylamine), homologues (methanol/ethanol, n-hexane/n-heptane), or
structural isomers (MnBK/MIBK). These differences in the cited pairs
have greater potential to change the chemical properties of the
molecule. For example, the addition of the methyl group in the benzene/
toluene pair changes the way that the molecule is converted to other
molecules and removed from the body. Toluene is converted (metabolized)
to compounds with low toxicity (e.g., benzoic acid) that are dissolved
easily in water and removed from the body. Benzene's structure does not
allow the use of this pathway for removing the chemical. Instead,
benzene is converted and removed via a pathway that creates cancer-
producing compounds.10
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\10\ Andrews, L.S. and R. Snyder. 1991. Toxic effects of
solvents and vapors. In: Amdur, M.O., J. Doull, and C.D. Klaassen.
Casarett and Doull's Toxicology: The Basic Science of Poisons, 4th
ed. New York, NY: Pergamon Press. pp. 681-722.
BILLING CODE 6560-50-P
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[GRAPHIC] [TIFF OMITTED] TR04MY98.002
BILLING CODE 6560-50-C
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Thus, the structural similarities between 2,4,6-TCP and 2,4,6-TBP
are greater than those between pairs of chemicals cited by a commenter
in a counter-example. As described in the Listing Background Document
and the Response to Public Comment Document, the physical properties of
the compounds are also similar, with similar octanol/water partition
coefficients and solubility in the same solvents. The available genetic
toxicity data show consistent results for 2,4,6-TCP and 2,4,6-TBP,
although data for the latter compound are quite limited. Finally,
examples in the literature support the idea that if a chlorinated
compound is a carcinogen, the compound formed by substitution of a
chlorine with bromine still will be a carcinogen. Based on this line of
reasoning, the Agency believes that a SAR is appropriate in this case,
and the very strong chemical similarities between 2,4,6-TCP and 2,4,6-
TBP justify the use of the cancer slope factor for 2,4,6-TCP as a
default value for 2,4,6-TBP.
Two commenters expressed reservations regarding the use of QSAR/SAR
analysis to support listing determinations, but outlined conditions
under which the use of SARs may be acceptable. Both of these commenters
recommended that the Agency require some level of peer review of SAR
results as a standard procedure, including both internal reviews by
Agency senior scientists and external peer reviews. EPA is cognizant of
the novelty of the use of SAR analysis for this hazardous waste
determination and, therefore, has subjected its analysis to both
internal Agency review and external peer review, as described in
Section III.A.4.
4. Types of Data Appropriate to Support or Refute SAR Predictions
Five commenters responded to the Agency's request for information
on the types of data appropriate in supporting or refuting SAR results.
Three commenters stated that actual data should be used to confirm or
refute SAR predictions and that empirical evidence should take
precedence over modeling predictions. One commenter added that the
Agency should simplify delisting procedures for sole-constituent wastes
that were listed based on SAR analysis such that if actual data become
available that refute the SAR conclusions, the Agency could delist the
waste. EPA appreciates the commenters' response to its request for
information on the types of data appropriate for supporting or refuting
SAR analyses. If toxicity data for 2,4,6-TBP become available at some
point in the future and these data refute the results of the Agency's
SAR analysis for this rulemaking, EPA could take appropriate action at
that time to revisit the listing investigation for 2,4,6-TBP production
wastes.
D. Addition of Constituent to Appendix VIII
Two commenters stated that EPA cannot simultaneously propose to
list a constituent in Appendix VIII and propose to list a waste as
hazardous because it contains that constituent. The commenters
contended that this approach is illegal and violates the procedures
established in 40 CFR 261.11(a)(3), which require the Agency to list a
constituent in Appendix VIII based on the results of ``scientific
studies'' demonstrating that the substance has toxic or other adverse
effects. Following the listing of a constituent in Appendix VIII, the
Agency may use that constituent to justify a hazardous waste listing.
Therefore, they reasoned that EPA may not proceed with listing the
2,4,6-tribromophenol production wastes because the hazardous
constituent (2,4,6-tribromophenol) was proposed for inclusion in
Appendix VIII simultaneously with the proposed hazardous waste listing.
EPA disagrees and finds no basis in the regulation to support this
contention. Furthermore, this practice is long-standing. Other
simultaneous listings are found at 59 FR 24530 (May 11, 1994), 59 FR
458 (Jan. 4, 1994), 54 FR 50968 (Dec. 11, 1989), and 51 FR 6537 (Feb.
25, 1986).
The plain language of 40 CFR 261.11(a)(3) provides that a waste
shall be listed if it contains an Appendix VIII constituent and the
Administrator concludes it poses a hazard after considering the eleven
factors cited in the regulation. Neither the August 1986 preamble text
to which the commenter makes reference nor the regulatory language of
40 CFR 261.11(a)(3) suggest that a sequential determination is
required. In the August 1986 rule, the Agency stated that the
significance of placing a constituent in Appendix VIII includes the
fact that the constituent then can be cited as a basis for listing
toxic wastes (51 FR 28296, August 6, 1986). Nothing in this statement
suggests that an Appendix VIII listing must be proposed for public
comment and finalized separately from an associated hazardous waste
listing. The public was given ample opportunity to comment on all
relevant issues concerning both the hazardous waste listing and the
Appendix VIII listing on which it is based.
Not only is there nothing in the regulation that precludes EPA from
considering Appendix VIII and hazardous waste listings in the same
proposal but, in many instances, to do otherwise could lead to absurd
and futile results. In general, because listing a substance in Appendix
VIII and listing a substance or a waste stream as a hazardous waste
under 40 CFR 261.11(a)(3) involve consideration of a common factor,
toxicity, simultaneous listing is appropriate.
E. Plausible Mismanagement Scenario and Other Issues in the Listing
Determination for Waste Solids From the Production of 2,4,6-
Tribromophenol.
1. Comments on the Proposed Rule
In comments on the proposed rule published May 11, 1994 (59 FR
24530), one commenter disputed the plausible mismanagement scenario
used by the Agency to support the proposed listing of 2,4,6-TBP
production wastes (disposal in unlined Subtitle D landfills), and noted
that the proposed rule contained errors in the description of 2,4,6-TBP
waste quantities and management practices. The commenter stated that it
was the sole generator of TBP wastes covered by the proposed listing
and that all of its solid streams containing TBP are shipped to a
Subtitle C disposal facility. The generator subsequently submitted
information showing that it disposed of these wastes in Subtitle C
facilities for many years. (See letter to Anthony Carrell, EPA, from
Stephen M. Wallace, Great Lakes Chemical Corporation, dated April 23,
1997). The generator reported sending the waste to various Subtitle C
landfills since 1981 (1981-1990, Chemical Waste Management, Emelle, AL;
1991-1994, Chemical Waste Management, Carliss, LA; 1995-1996, American
Ecology, Winona, TX; 1997, Philips Environmental, Avalon, TX). The
commenter noted that the only waste from 2,4,6-TBP production disposed
in a Subtitle D landfill consists of 10 tons of empty soda ash bags
that do not contain any TBP. The commenter stated that the other
combined waste solids from TBP production (floor sweepings, off-
specification product and spent carbon from filters) total
approximately 34 tons annually. The commenter argued that EPA's
selection of an unlined Subtitle D landfill as a plausible
mismanagement scenario is erroneous and, therefore, EPA's risk analysis
significantly overstates the risk.
After considering these comments, EPA issued the September 3, 1997,
letter, noted above, which evaluated additional information to support
the
[[Page 24609]]
Agency's listing decision. The following paragraphs in this section
describe the substance of the September 3 letter, including the new
risk analysis and the new plausible mismanagement scenario of voluntary
disposal in a Subtitle C landfill for this waste stream. Responses to
the additional comments received on the September 3 letter are
discussed in the remaining sections of this Unit.
In the September 3 letter, EPA stated that based on the information
provided by the commenter, the Agency agrees that the quantity of waste
solids from 2,4,6-TBP production that contain 2,4,6-TBP levels of
concern should be approximately 34 tons, and should not include the 10
tons of empty bags. The Agency also acknowledges that the generator
apparently has a long record of disposing the wastes with high 2,4,6-
TBP content in a lined Subtitle C hazardous waste landfill. However,
EPA continues to believe that the waste solids from production of
2,4,6-TBP should be listed as hazardous, even if the waste continues to
be sent to Subtitle C landfills. EPA considered several critical
factors in deciding to list this waste stream.
First, Congress clearly expressed its intent that the Agency is not
to place excessive reliance on confidence in landfill design and liners
for problematic wastes. In the Hazardous and Solid Waste Amendments
(HSWA) of 1984, Congress explicitly added as one of the ``findings'' to
RCRA that ``land disposal facilities are not capable of assuring long-
term containment of certain hazardous wastes'' and that ``reliance on
land disposal should be minimized or eliminated.'' RCRA section
1002(b)(7), 42 U.S.C. 6902(b)(7). As a result of this finding, and
others, Congress added the land disposal restriction (LDR) program to
RCRA, which significantly restricts land disposal of hazardous wastes.
Further, it was made very clear in the Conference Report for HSWA that
the new findings in RCRA were intended to House Report No. 98-1133,
98th Cong., 2d Sess. at 80-81 (Oct. 3, 1984). EPA views the statute and
legislative history as sufficient justification to evaluate in a
listing determination all risks of land disposal, including in
appropriate cases risks from voluntary disposal in permitted Subtitle C
facilities. This is particularly true where risks presented by a waste
might be high if releases occur, and treatment of the waste under
Subtitle C would significantly reduce these risks.
Accordingly, EPA added to the rulemaking record additional data on
the effects of disposal in Subtitle C landfills and reevaluated its
analysis of the factors contained in 40 CFR 261.11(a)(3) that are
relevant to listing the 2,4,6-tribromophenol waste solids. The
following analysis describes the September 3 letter's evaluation of, in
particular, the inherent toxicity of the hazard constituent in the
waste (Sec. 261.11(a)(3)(i)), concentration of the hazardous
constituent in the waste (Sec. 261.11(a)(3)(ii)), the potential of the
hazardous constituent to migrate into the environment
(Sec. 261.11(a)(iii)), the relevance of the quantities of the waste
generated (Sec. 261.11(a)(3)(viii)) when compared with these other
factors, and how these factors are weighed when considered with the
plausible management scenario of voluntary disposal of the waste in a
Subtitle C landfill (Sec. 261.11(a)(3)(vii)). EPA concluded, after
balancing these factors in accordance with the Agency's listing
determination policy described in its December 22, 1994, proposed rule
listing certain wastes generated during the production of dyes and
pigments (59 FR 66073-78) that the 2,4,6-tribromophenol waste solids
are capable of posing a substantial present or potential hazard to
human health or the environment.
Review of the scientific data, particularly sample analysis and
Structure Activity Relationships (SAR), shows that evaluation of
disposal in subtitle C facilities is especially appropriate for
untreated 2,4,6-tribromophenol waste solids. The waste contains a
highly toxic chemical, 2,4,6-TBP, which may present significant
carcinogenic risk even at low concentrations. This chemical was also
found to be present in the wastes of concern at extremely high
concentrations. EPA's analytical data show levels up to 40% (equivalent
to 400,000 ppm) in the waste solids. Thus, while the volume of wastes
generated (approximately 34 tons annually) is not very large, the
extremely high levels of 2,4,6-TBP render this waste highly toxic. As a
general matter, when settings its own priorities, EPA would not
ordinarily consider it a priority to make a listing determination on a
small-volume waste from a single generator. However, EPA has a set of
statutory obligations to make a prescribed set of listing
determinations and a determination on this particular waste stream is
an obligation under the consent decree governing EPA's completion of
those obligations.
Furthermore, EPA's data show that 2,4,6-TBP is relatively mobile
and will leach out of the waste at high concentrations. In the
proposal, EPA used the TCLP method to estimate the potential
concentration of waste constituents that could be in leachate generated
from disposal of the waste in a landfill, and found up to 760 mg/L of
2,4,6-TBP in the TCLP leachate. This level is 76,000 times the health-
based criteria of 0.01 mg/L that corresponds to the 10-6
cancer risk level for ingestion. The proposed rule estimated risks of 7
x 10-4 from migration to groundwater, if this waste were
placed in an unlined landfill (see the proposed rule, 59 FR 24538).
Although the generator has sent this waste to a lined Subtitle C
facility in the past, EPA believes that the risks estimated from
migration from an unlined landfill provide an indication of the
potential risks that could occur if 2,4,6-TBP is released from the
lined landfill due to failure of the unit to contain the waste
leachate. The Agency agrees that the liner/leachate collection system
in a Subtitle C unit would serve to contain the waste, and would
substantially lessen the risk even in the case of liner failure.
However, EPA believes that the purpose of the RCRA hazardous waste
treatment requirements (as expressed by Congress) is to reduce the
uncertainty inherent in engineered containment approaches.
In past rulemakings EPA has assumed that waste containment systems
will tend to degrade with time. In the proposal for the Land Disposal
Restrictions (January 14, 1986, 51 FR 1641) EPA noted that in the long-
term (beyond the post-closure period) the efficiency of cover and liner
systems will degrade. Eventually synthetic liners will degrade and
leachate collection systems will cease operation. In the proposed Liner
and Leak Detection Rule (May 29, 1987; 52 FR 20218) EPA also stated
that no liner can be expected to remain impervious forever. As a result
of interactions with waste, environmental effects, installation
problems, and operating practices, liners eventually may degrade, tear,
or crack and allow liquids to migrate out of the unit. In evaluating
the benefits of this rule (see 52 FR 20270), EPA noted that a properly
installed double liner and leachate collection system, together with a
final cover placed at closure, substantially reduces release during the
operating life and post-closure care period. However, these
technologies may not effectively reduce the longer-term risk for
landfills, especially for persistent and mobile compounds, because the
containment system may only delay leachate release from the landfill
until after the post-closure period, when the cap and leachate
collection system begin to fail.
EPA has attempted to account for the effect of Subtitle C
containment (covers and liners) in the Regulatory Impact Analyses (RIA)
completed for other
[[Page 24610]]
recent rulemakings. (See the RIA for the Land Disposal Restrictions--
Phase II rule, pages 5-10, in the docket for the final Phase II rule,
published September 19, 1994, 59 FR 47980; and the RIA for the final
rule on Corrective Action Management Units, Appendix C, in the docket
for the rule published February 16, 1993, 58 FR 8658.) These documents
are incorporated by reference into the docket for this rule. As EPA
noted in the source document used in these RIAs (Technical Guidance
Document, ``Indexing of Long-Term Effectiveness of Waste Containment
Systems for a Regulatory Impact Analysis,'' Office of Solid Waste,
November 1992; this document has been placed in the public docket for
today's rule), the structural integrity of waste containment systems
degrades over time due to stresses on system components. EPA noted that
failures of multi-component liner systems have been reported in the
literature, and that some liners fail unpredictably with time. While
acknowledging the uncertainties in predicting long-term effectiveness,
EPA estimated that the effectiveness of Subtitle C composite liner
systems may decrease significantly with time.
Although it is difficult to quantify the impact of the long-term
degradation of liner systems, the high level of risk estimated from
disposal of this waste in an unlined landfill (7 x 10-4)
means that even a modest reduction in long-term liner effectiveness
would present risks of concern. For example, if the long-term
effectiveness of the landfill liner and containment system were on the
order of 95%, which would reduce the potential risks from releases to
groundwater by 20-fold, the residual risk would exceed 3 x
10-5. In fact, the containment systems would have to be in
excess of 98% effective for the estimated risk to drop below 1 x
10-5. The risks for this particular untreated waste,
therefore, would remain above EPA's presumptive level of concern for
listing (>10-5), whether they were sent to an unlined
landfill or a Subtitle C landfill (for a discussion in risk levels used
in listing determination see December 22, 1994, 59 FR 66075).
The Agency recognizes that a recent court decision (Dithiocarbamate
Task Force v. EPA, 98 F.3d 1394 (D.C. Cir. 1996), raised questions as
to what constitutes ``plausible'' mismanagement under the listing
regulations (Sec. 261.11(a)(3)). However, EPA has not yet fully
evaluated the recent court decision to determine how to weigh possible
future changes in management practices and is not relying on projecting
new management practices in this listing decision. For the purposes of
the analysis in the September 3 letter, EPA assumed that the current
waste management practices continue (i.e., disposal of the untreated
waste in Subtitle C landfills).
To respond to the commenter's concern related to waste solids that
do not contain 2,4,6-TBP, EPA is revising the regulatory language to
clarify that the wastes covered in the listing are those of concern,
i.e., those containing high levels of 2,4,6-TBP. This avoids capturing
the empty soda ash bags, and possibly other waste solids downstream
from the production unit that EPA did not intend to cover in the
listing. Therefore, the final listing reads as follows:
K140--Floor sweepings, off-specification product, and spent filter
media from the production of 2,4,6-tribromophenol.
Another commenter stated that the high concentrations of TBP in the
floor sweepings sampled by EPA provide singular justification for the
listing of these wastes. EPA agrees with the commenter that the high
concentration of the toxic chemical, 2,4,6-TBP, is a major concern.
However, EPA did not consider this factor in isolation, but also
considered the mobility of the waste and its inherent toxicity as
equally important factors, and balanced all of these factors in the
risk assessment. As noted above, the risk assessment predicts TBP
leaching from unlined and lined landfills to receptor drinking-water
wells at concentrations well above health-based levels of concern.
2. Comments on the September 3, 1997, Notice Letter
As noted previously in today's rule, EPA provided an opportunity
for further comment on the Agency's reevaluation, described above, of
the rationale for the listing determination for the waste solids from
the production of 2,4,6-TBP. EPA sent letters of notice to three
parties who commented on the proposed rule and could be expected to
have an interest in the final decision and the revised rationale for
listing. EPA received the comments noted below from the three entities
that received the notice letter; one supported the decision to list
2,4,6-TBP production wastes, and two opposed the listing. EPA's
response to these new comments are summarized below and are described
in more detail in the docket. (See ``Supplementary Response To Public
Comment'', April 1998)
a. Procedural Comments. One commenter challenged EPA's approach of
sending notice letters to only three commenters on procedural grounds,
and claimed that EPA was soliciting comments through a ``selective
notice procedure'' that fails to give the general public opportunity to
be heard on several issues. The commenter argued that others should
have a chance to comment on the idea that placement of waste in a
Subtitle C landfill that is in compliance with appropriate regulations
may be ``mismanagement,''because this may have significant
ramifications for individuals who did not previously comment and has
``far-reaching effects for those operating and using'' hazardous waste
facilities.
Another commenter argued that EPA cannot list wastes based on the
theory that Subtitle C disposal constitutes ``mismanagement'' without
amending its listing criteria, stating that EPA must first propose and
seek comment on the new theory of mismanagement before it can redefine
its basic approach to the listing process.
EPA does not agree that notice was inadequate, nor does the Agency
agree the listing criteria must be amended. Due to the limited time EPA
has for completing this action, the Agency decided that letters
providing actual notice to the parties who commented on the proposed
rule and could be expected to have a direct interest in the final rule
decision was appropriate. Those receiving the letter included the only
current generator of the waste, and the industry group and
environmental group that commented on the proposed rule. These are the
parties EPA decided were arguably affected by the recharacterization of
the rationale for listing. EPA is not aware of any other generators of
this waste or any other persons who would have a direct interest in
this decision. The actual notice given in this case is sufficient.
No reasons offered by the commenters indicate any need to go beyond
the actual notice EPA provided. The decision in this case does not have
``palpable effects upon a regulated industry or the public in
general.'' Instead, it affects this wastestream, alone, and those that
can argue they have an interest in the wastestream. To the extent a
similar analysis may be used for other wastestreams EPA may consider
listing in the future, the affected parties will have adequate
opportunity to comment then. Moreover, today's action does not
compromise their legal rights to challenge such EPA listing decisions
in the future.
Also, there are no ramifications for individuals who did not
previously comment. The fact of the matter is that the revised
rationale described in the letter will not have ``far-reaching
[[Page 24611]]
effects'' for those operating and using hazardous waste landfills.
Rather, this decision is being made on the basis of risk for one
specific waste with certain properties and does not reflect any new
policy direction towards any other operators or users of hazardous
waste landfills. No persons are expected to change their habits, for
example, in changing the operations of their landfills, as a result of
this decision. No persons who operate their landfills in accordance
with Agency regulations will be affected by this decision. In any
future circumstances in which EPA chooses to evaluate, as part of a
listing decision, the risk basis of voluntarily putting a waste in a
Subtitle C landfill ample opportunity for comment will be provided.
Further, the commenter's concern that disposal of untreated waste
in a Subtitle C landfill that complies with regulations may be
mismanagement is misleading. Disposal of untreated waste in any type of
landfill could be considered mismanagement, despite compliance with all
applicable landfill design and operation regulations. No one would want
highly dangerous materials voluntarily placed in a Subtitle C landfill.
Clearly, some untreated wastes could pose a potential hazard of such
magnitude that merely voluntarily placing them in a lined landfill
would not be sufficient. In this instance, applying the factors in
Sec. 261.11(a)(3), EPA has concluded that the disposal of this highly
toxic, untreated waste in a Subtitle C landfill is improper management
within the meaning of that subsection of the regulations. EPA is not
suggesting that the landfills in question have been mismanaged. On the
contrary, the voluntary use of Subtitle C landfills by the generator
has been laudable. However, for purposes of a listing determination,
the overall practice is improper management in that is does not
adequately control risks to human health and the environment.
EPA also does not agree that the listing criteria have to be
modified in any way to allow the Agency to make the listing
determination for the organobromine waste at issue. The regulations
(see Sec. 261.11(a)(3)) clearly permit EPA to render a listing decision
based on a variety of factors. These factors were weighed when
considered with the plausible management scenario of voluntary disposal
of the waste in a Subtitle C landfill without previous treatment. After
balancing these factors EPA concluded that the 2,4,6-tribromophenol
waste solids are capable of posing a substantial present or potential
hazard to human health or the environment. It is consistent with the
regulations to reason that, if voluntary Subtitle C landfilling (absent
treatment) presents a substantial present or potential hazard, the
practice constitutes improper management under Sec. 261.11(a)(3)(vii).
Therefore, a regulatory change is definitely not needed prior to making
this listing determination.
b. Risks Related To Plausible Mismanagement Scenario. One commenter
stated that EPA's proposed listing is based on a management scenario
that is unsupported and implausible, and further noted that the
evaluation of future failure rates of Subtitle C landfill containment
systems is not supported by evidence in the docket. The commenter
states that the one study relied upon by EPA fails to account for the
multi-component nature of liner systems and does not specify how it
accounts for these factors, making it impossible to determine the
validity of the assigned failure rates. The commenter claimed EPA's
sole reliance on this study is arbitrary and capricious. The commenter
also stated that EPA did not consider site-specific factors (e.g, liner
type, soil type, annual precipitation) to determine if leachate will
reach groundwater. The commenter claimed, therefore, that EPA has not
made a reasoned determination that the long-term effectiveness
evaluation is valid at these specific facilities.
The commenter is wrong for a number of reasons. The effectiveness-
time relationships given in the reference used by EPA (Indexing of
Long-Term Effectiveness of Waste Containment Systems for a Regulatory
Impact Analysis, USEPA, November 1992) was based on an examination of
the technical literature on the subject, and an evaluation of many
technical factors. The document evaluated the effectiveness of various
components of the containment system, and identified the likely
degradation mechanisms. For example, landfill containment systems may
leak due to improper installation, and may be degrade by subsidence,
drying/cracking, freeze-thaw cycles, burrowing of animals, leachate
incompatibility, and vehicle loads. This analysis considered the
composite clay/geomembrane liners and caps required under RCRA Subtitle
C regulations. The document also provided data and cited references
showing that even configurations like RCRA Subtitle C liners do, in
some cases, leak over time. Concerning the leachate collection system,
EPA notes that the regulations require operation and maintenance of
these collection and leak detection systems for 30 years after closure
of the landfill (see 40 CFR 264.117). Over the long-term, therefore,
EPA cannot rely on leachate collection systems to prevent the eventual
release of leachate of untreated waste from the landfill if the liner
system fails.
EPA agrees that the degradation of a containment system depends to
some extent on the systems design and other site-specific factors.
However, the commenter provided no specific data indicating what site-
specific factors would prevent release of constituents from the wastes
disposed, or what the long-term containment efficiencies might exist
for the landfills at the sites in question. Therefore, EPA has no
reason to alter its analysis on this basis. Furthermore, EPA does not
believe that such a site-specific analysis is appropriate in this case,
because the generator may use many different landfills for disposal. In
fact, the history of the generator's disposal practices (See letter
from Great Lakes Chemical Corporation to EPA dated April 23, 1997)
shows that the generator changed disposal sites quite often (e.g., the
generator sent the waste to three different landfills between 1994 and
1997).
One commenter stated that EPA has turned this inquiry from
determining whether dangerous ``mismanagement'' is plausible into an
inquiry into whether it can be ruled out completely, and cites EPA's
admission that there is at least a 95% chance that C landfills will not
leak. The commenter claims EPA argues that ``nothing lasts forever,''
and therefore Subtitle C disposal can be mismanagement. The commenter
argues that this type of logic was unacceptable in the Dithiocarbamate
case. The commenter states that EPA effectively writes the requirement
of a ``plausible mismanagement scenario'' out of the listing rule, and
that recent court decisions do not allow EPA to evaluate such a factor
so as to drain it of all content.
As a preliminary matter, EPA points out that this listing is wholly
consistent with the Dithiocarbamate Task Force case. The Agency has
found that the common practice of the only generator of the waste over
more than 15 years is the plausible management scenario. The assessment
of all relevant factors under Sec. 261.11(a)(3) led the Agency to
conclude that voluntary Subtitle C landfill disposal is improper
management.
Furthermore, the Agency has not turned this into an inquiry about
whether ``mismanagement'' can be ruled out completely. Rather, the
Agency has evaluated this particular waste under the conditions of
plausible management and reached a conclusion that there is
[[Page 24612]]
a substantial present or potential risk. The commenter is attempting to
turn the Agency's risk analysis into a narrow inquiry into plausible
mismanagement. This is simply incorrect.
With respect to the EPA's analysis of risk, the Agency did not
state that there is a 95% chance that C landfills will not leak.
Rather, EPA was indicating that even if the containment system was 95%
effective, the potential risks from the waste in question are so high
that it would still present a risk at levels of concern. Even if a
Subtitle C landfill was 98% effective in reducing risk relative to risk
in an unlined landfill (e.g., the Subtitle C landfill's effectiveness
decreased 2% from a combination of cap failure and abandonment of
active landfill management), the estimated risk would still exceed 1
x 10-5. The actual long-term efficiency is extremely difficult to
estimate, given the highly uncertain long-term integrity of liners/
leachate collection systems and landfill caps. The document cited by
EPA that attempts to evaluate the effectiveness of liner systems
estimated it would degrade to an efficiency well below 95% over the
long term (e.g., one hundred years). EPA is not attempting to
absolutely rule out certain management scenarios, but rather to account
for the likely degradation of a Subtitle C containment system over the
long-term. Certainly the available data (cited in the document used by
EPA) clearly show that the materials that make up liners and caps are
expected to degrade over time. Therefore, given this fact, in
conjunction with the available estimates of long-term effectiveness,
EPA believes that the highly toxic waste in question may present a
significant risk when placed in any landfill, even a Subtitle C unit.
One commenter stated that EPA's legislative references do not
support the idea that disposal in Subtitle C landfills constitutes
mismanagement, but rather relate to historic problems caused by
unregulated disposal, and expressed support for minimizing the
quantities and toxicity of wastes that must be disposed. The commenter
states Congress did not require all wastes to be treated before land
disposal, but only wastes that are hazardous, and notes that the fact
that treatment might reduce the hazardousness of a waste is not a
relevant factor in EPA's listing criteria.
EPA disagrees with the claim that Congress was concerned only with
unregulated land disposal. The statute itself clearly states
Congressional intent: ``certain classes of land disposal facilities are
not capable of assuring long-term containment of certain hazardous
wastes * * * and land disposal, particularly landfill and surface
impoundment, should be the least favored method for managing hazardous
wastes.'' (See RCRA, section 1002(b)(7)). EPA agrees that Congress did
not require all wastes to be treated prior to land disposal. However,
in this case EPA believes the waste in question presents a substantial
hazard when land filled, even in a Subtitle C landfill, in the form in
which it is generated (i.e., untreated). Therefore, EPA believes the
waste is, in fact, hazardous and should be subject to full regulation
under Subtitle C, including the land disposal restrictions.
One commenter stated that, while EPA is not relying on projecting
new management practices in this listing decision, the Dithiocarbamates
decision is still controlling. The commenter noted that when the court
struck down the K160 listing, it did not remand it to allow EPA to
reevaluate whether disposal in a Subtitle C landfill constitutes
``plausible mismanagement,'' as EPA is attempting to do here. The
commenter went on to say that, in striking down 24 other waste listing
(U-listings) in the Dithiocarbamate decision, the court refused to
accept as examples of mismanagement various past or future accidents,
and stated that EPA assertions that ``accidents will happen'' does not
constitute ``plausible mismanagement.'' The commenter claimed this
analysis is equally applicable to EPA's assumption that all landfills
will leak eventually, and the fact that some unquantified uncertainty
exists regarding long-term risks from Subtitle C disposal does not mean
that such disposal is mismanagement. The commenter argued that the only
change listing the waste would cause would be to require compliance
with land disposal treatment standards and it is difficult to see how a
listing would substantially reduce risks. The commenter stated that EPA
did not address the question of how much risk reduction would result
from treatment. The commenter also noted that the fact that treatment
might reduce the hazardousness of a waste is not a relevant factor
under Sec. 261.11(a)(3) in deciding whether to list a waste as
hazardous.
The commenter's reference to ``the Dithiocarbamate case'' is not
relevant in this context. In the Dithiocarbamate case, the court did
not address the issue of Subtitle C management in any substantive way.
The court stated that it was vacating the listing of K160 ``[b]ecause
EPA failed to identify a plausible mismanagement scenario * * *'' (98
F.3d at 1404) and did not reach the issue of whether voluntary disposal
in a Subtitle C landfill (absent treatment) would present a substantial
risk. The decision in no way limits the Agency from considering
potential risks from Subtitle C management. EPA had not raised the
issue in rulemaking because the Agency had determined that the
plausible management scenario was an unlined landfill. The Agency did
not conduct a risk assessment on the Subtitle C landfill because it did
not believe it had to.
The reference to consideration of the U wastes in the
Dithiocarbamate case is also irrelevant in this context. The commenter
is confusing EPA's acknowledgment of the uncertainty in quantitatively
estimating the long-term efficiency of Subtitle C containment systems
as being equivalent to assertions that ``accidents happen,'' referenced
by the Dithiocarbamate case. As noted in response to other comments in
this proceeding, EPA's evaluation attempted to account for the likely
degradation of a Subtitle C containment system over the long-term.
Therefore, EPA continues to believe that it is logical and appropriate
to assume that the containment efficiency of landfills will degrade
sufficiently so that, for this highly toxic waste, disposal of the
untreated material in a Subtitle C landfill may present a substantial
present and potential hazard.
As noted in the commenter's own statements, unlike in the
Dithiocarbamate case, in which the court did not see how U-listings
would avert accidents, a listing of the 2,4,6-TBP waste solids would,
in fact, prevent the placement of untreated wastes in the landfill.
Further, the treatment standards for this newly listed waste (see the
land disposal restrictions section of today's rule) require levels of
2,4,6-TBP for nonwastewaters to be no greater than 7.4 mg/kg. This
level equates to a reduction of up to a 50,000-fold reduction in the
level of 2,4,6-TBP in the waste. Such a reduction in 2,4,6-TBP levels
will likely result in significant risk reduction--a clear benefit of
the listing. Furthermore, the Sec. 261.11(a)(3) criteria, as noted by
the commenter, does not require the Agency to consider risk reduction.
Section 261.11 is promulgated under the authority of section 3001 of
RCRA, which requires EPA to identify criteria for listing. Once listed,
the wastes would become subject to the management requirements of
Subtitle C. The regulations for management requirements are promulgated
under other sections of RCRA, like sections 3002 (generator standards),
3003 (transportation standards), 3004
[[Page 24613]]
(standards for treatment, storage and disposal facilities), and 3005
(permits for treatment, storage or disposal). These are the sections
under which EPA would consider risk reduction measures that would be
protective of human health or the environment.
While one commenter supported EPA's decision to list the 2,4,6-TBP
solids and filter cartridges, the commenter stated that EPA assumes in
its reevaluation that the wastes at issue will always be landfilled in
a Subtitle C facility, even though the regulated community is under no
legal or technical mandate to do so in the absence of a hazardous waste
listing. The commenter claimed that EPA's proposed listing rationale
based on Subtitle C landfilling substantially understates the risks,
and argues that EPA should not assume past disposal practices represent
the only plausible mismanagement practice for at least four reasons:
(1) There is no technical or other bar to additional companies
producing 2,4,6-TBP and generating the wastes at issue, either at
existing organobromine chemical production facilities or at new
locations. Therefore identification of plausible mismanagement
scenarios should involve more than an analysis of one company's
historic disposal practices; (2) the wastes at issue (floor sweepings
and filter cartridges) are frequently observed in the organobromine
chemical industry, and in many cases are landfilled onsite in
nonhazardous units. Thus, EPA should consider how similar wastes from
other organobromine production processes are managed when identifying
plausible mismanagement scenarios; (3) the company currently generating
these wastes has used three different landfills since 1994, suggesting
that cost is the overriding factor in the company's disposal decision.
It is not unreasonable for EPA to assume the cost differential between
Subtitle C and D landfills may cause the company to use a nonhazardous
waste landfill; and (4) the production facility's 1995 TRI report
reveals that half of the TRI chemicals sent offsite for disposal were
sent to a nonhazardous landfill. Thus, even at this one facility
Subtitle C landfilling is not uniformly practiced.
As a general response to these comments, the Agency notes that
these arguments have no practical effect and would not change EPA's
decision to list the waste. In the original proposal to list the 2,4,6-
TBP production solids, EPA estimated the risks from disposal in an
unlined landfill would warrant listing the waste (see proposed rule, 59
FR 24530, May 11, 1994). As noted in the September 3, 1997 notice
letter, the risks from such disposal would be mitigated in a Subtitle C
landfill, but would still be at levels of concern. Therefore, EPA does
not need to rely on projecting new management practices in this listing
decision. EPA intends to address the more general issue of how to weigh
potential changes in management practice in the future.
Two commenters argued that EPA did not fully consider the impact of
the existing RCRA Subtitle C regulations in its analysis of potential
risks from disposal in such a regulated landfill. One argued that the
proposed mismanagement scenario presumes that all landfill operators
are in violation of RCRA regulations, and noted that the regulations
require that liner/leachate collection systems prevent migration out of
landfills during the active life (including the closure period) of the
landfill. The commenter argues that the resources spent on landfill
design and construction have resulted in more than a 20-fold decrease
in risk posed by the waste disposed. The commenter stated that if EPA
is concerned with releases from landfills, the proper place to address
this is through the regulations governing land disposal units, and not
the listing process.
The other commenter stated that comprehensive landfill regulations
prevent the release of hazardous constituents from the waste into the
environment by: Double liners and leachate collection systems,
groundwater monitoring, and corrective action requirements in case of a
release. The commenter also noted that the performance of Subtitle C
landfills is guaranteed by operating, closure, and post-closure
permits, but stated that none of these safeguards were addressed in
EPA's reevaluation.
EPA agrees that the regulations governing Subtitle C landfills are
stringent and are designed to prevent releases from the unit, to detect
if such leaks occur, and to take corrective action if necessary.
However, EPA is not assuming that all landfill operators will be in
violation of RCRA. EPA is simply recognizing that such standards are
not protective in perpetuity nor for every possible waste. EPA is not
saying that voluntary Subtitle C landfilling is always ``improper'',
just that there are wastes that should not go into them if they are not
treated. EPA agrees that properly installed liner systems and final
covers substantially reduce the potential for releases during the
operating life and post-closure period (see 52 FR 20270, May 29, 1987).
EPA also agrees that permits for landfills help to ensure the
implementation of stringent requirements for groundwater monitoring and
corrective action. The RCRA regulations require a 30 year post-closure
period, during which the unit is maintained and monitored (see 40 CFR
264.117), but after the post-closure monitoring ends releases may not
be detected or corrected. While extending the post-closure period might
be one way to decrease potential risks from Subtitle C landfills, EPA
notes that treatment under the land disposal restrictions program is
another way (and perhaps a more direct way) of ensuring long-term risks
are minimized. Listing the waste solids from the production of 2,4,6-
TBP ensures that this highly toxic waste will be treated prior to
landfill disposal.
c. Demonstration of a Substantial Hazard. One commenter claimed
that EPA's approach does not demonstrate that the TBP wastes managed in
Subtitle C landfills pose a substantial hazard as required by the
statute and EPA's rules (Sec. 261.11(a)(3)). The commenter argued that
no human health or environmental damage has ever occurred as a result
of improper management of TBP wastes, and the quantity of the TBP waste
(35 tons per year) is ``inconsequential.'' The commenter also stated
that the court in the Dithiocarbamate case indicated that EPA must
balance the toxicity of the chemicals with other factors specified in
EPA's listing criteria. Finally, the commenter noted that EPA's
estimate of risks above 10-5 from TBP wastes in Subtitle C
landfills is ``based on improper extrapolation from Subtitle D risk
modeling.''
EPA disagrees with the commenter's assessment of the hazard posed
by the TBP wastes. First, the regulatory criteria for listing wastes as
hazardous is that the wastes may * * * pose a substantial present or
potential hazard.'' These wastes certainly meet that criteria. While
EPA has not found damage cases that document health or environmental
damage from disposal of this waste, this is only one of the factors EPA
considers in its listing decisions. While EPA has not identified any
cases of actual damages from this waste, EPA has explained how it
considered the other factors under Sec. 262.11(a)(3). The risk
assessment, after consideration of all of these factors shows
individual risk numbers to be above EPA's level of concern.
Furthermore, by listing a waste as hazardous, EPA hopes to prevent such
damage from occurring, and the Agency has often listed wastes in the
absence of definitive damage cases. Contrary to the comment, EPA does
not concede that the volume of waste at issue (34 tons annually) is
necessarily ``inconsequential.'' The volume of waste
[[Page 24614]]
must be examined in conjunction with the concentration and properties
of toxic constituents present. In this case, the relatively small
quantity of waste contains very high concentrations of a highly toxic
constituent, 2,4,6-TBP.
As noted elsewhere in today's rule, EPA continues to believe that
the SAR results demonstrate that 2,4,6-TBP is highly toxic.
Furthermore, EPA has shown how this toxic chemical, in a highly
concentrated waste, may potentially cause a substantial risk even if
managed in a Subtitle C landfill. The waste in question is so toxic and
concentrated that release may occur at levels of concern, even if the
containment system of a Subtitle C landfill were very high (e.g., 95%).
Given this result, EPA believes that listing is warranted.
d. Other Risk Issues. Two commenters argued that the Agency's
toxicity assumptions for 2,4,6-TBP are invalid. One stated that EPA
failed to address comments on the use of Quantitative Structure
Activity Relationships (QSAR) in its risk analysis, and incorporated
its previous comments by reference. The commenter also noted that a
proposal by EPA to gather the data necessary to evaluate 2,4,6-TBP was
rejected by the Interagency Testing Committee (ITC). The commenter
stated that, while the ITC originally proposed to include 2,4,6-TBP on
the priority testing list under Section 4(e) of the Toxic Substances
Control Act (TSCA), following receipt of exposure information from an
industry group and the producer of 2,4,6-TBP, the ITC revised its
position and removed 2,4,6-TBP from the priority list. The commenter
stated that the rationale for removal of 2,4,6-TBP was based on the
ITC's determination that ``environmental and workplace monitoring
indicate that 2,4,6-tribromophenol is not likely to result in
substantial environmental releases or significant exposures to workers,
consumers or the general population.''
EPA has not ignored the comments received on the Agency's use of
Structure Activity Relationships for estimating the toxicity of 2,4,6-
TBP. EPA responds fully to all comments related to this issue in a
separate section of today's preamble. As the commenter noted, the ITC's
40th Report revised the TSCA section 4(e) Priority Testing List by
removing 2,4,6,-TBP, which had previously been recommended for testing
in its 39th report (62 FR 8578, February 25, 1997). The ITC stated that
it removed 2,4,6-TBP after reviewing data that demonstrated that: (1)
It is used as a chemical intermediate to produce flame retardants; (2)
greater than 99% of 2,4,6-TBP used as an end-product is shipped
overseas to be used as an intermediate in the production of brominated
flame retardants; and (3) environmental and workplace monitoring
indicate that 2,4,6-TBP is not likely to result in substantial
environmental releases or significant exposures to workers, consumers,
or the general public. Exposure and release information provided by
industry and the CMA include an industrial hygiene survey from 1979, a
historical prospective mortality study of workers, a pollution
evaluation, and a determination of brominated organic compounds in
environmental matrices (secondary effluents). The available exposure
information pertains to workers and the potential for general
population exposure from manufacturing sites. In deciding to list waste
solids from the production of 2,4,6-TBP, however, EPA considered in
detail the potential exposure and risks due to the disposal of wastes
generated, not product use. EPA notes that none of the exposure studies
used in the ITC decision deal with RCRA issues, for example, the
presence of TBP in waste streams, its subsequent disposal in a
landfill, and the potential hazards associated with leakage from such a
landfill or with any mismanagement scenario.
EPA further examined the rationale for the removal of 2,4,6-TBP
from the Priority Testing List and does not agree that this action in
any way undermines EPA's use of SAR to estimate the chemical's
toxicity. 2,4,6-TBP was not removed from the ITC Priority Testing List
because the ITC had found that TBP was not toxic. Indeed, the chemical
was originally included on the List because the NIEHS needed chronic
toxicity and 2-year carcinogenesis study data. The availability of
these data would obviate the need for the use of a qualitative or
quantitative SAR by EPA, which would prefer to use actual data on the
constituent in question whenever possible. Among the studies cited by
CMA and GLCC as available for EPA review are acute toxicity (oral,
inhalation, and dermal), dermal sensitization, skin and eye irritation,
21-day inhalation toxicity, 28-day subacute dermal toxicity, clearance,
teratogenicity, genotoxicity, and pharmacokinetics. None of these
studies are sufficient to judge the carcinogenic potential of TBP,
which is the primary endpoint of concern for this chemical. Therefore,
EPA does not believe that the ITC decision to remove TBP from the
Priority Testing List addresses EPA's determination that 2,4,6-TBP is
highly toxic as indicated by SAR and that disposal of wastes containing
high levels of this toxic chemical in a landfill (even a Subtitle C
landfill) poses a substantial hazard that requires listing the waste as
hazardous.
One commenter supported the proposed decision to list waste solids
from the production of 2,4,6-tribromophenol, but argued that EPA
underestimated the risks posed by disposal of the waste in a Subtitle C
landfill for at least three reasons. The reasons noted by the commenter
were: (1) The TCLP understates the leaching potential of the waste in a
Subtitle C landfill by at least an order of magnitude, because the
waste may be exposed to solvents and other chemicals that encourage
contaminant leaching, and because the TCLP appears ``uniquely
ineffective'' in leaching contaminants from the waste; (2) EPA's risk
estimates are based on the presence of 2,4,6-TBP only and ignore the
presence of arsenic and other toxic contaminants in the waste and TCLP
leachate; (3) EPA's assumption of 95% containment efficiency for a
Subtitle C landfill is unreasonable given that owner/operator's post-
closure responsibilities typically end after 30 years; containment
efficiency would drop to 60% at 100 years, and beyond 100 years
additional declines can be expected.
As a general response to the argument that EPA underestimated the
risks posed by Subtitle C disposal for the wastes in question, the
Agency notes that these arguments have no practical effect and would
not change EPA's decision to list the waste. However, EPA does not
agree with some of the arguments put forth by the commenter, and is
responding to them for this reason. EPA does not agree that the TCLP
underestimates the leaching potential of the waste in question for
reasons discussed below. Absent any firm data to conclude otherwise,
EPA finds no reason to conclude that the TCLP underestimates the
leaching potential of the 2,4,6-TBP production wastes. As a preliminary
matter, EPA notes that the commenter cites no basis for its quantified
estimate that the leaching is underestimated by one order of magnitude.
Moreover, there is no indication that the TCLP is ``uniquely
ineffective'' in leaching contaminants from this waste, as the
commenter claims. The properties of 2,4,6-TBP indicate that the
relatively low leaching efficiency is not unexpected. This chemical is
not highly soluble in water (70 ppm; see The Merck Index, Ninth
Edition, 1976) and would not be expected to leach from the organic
waste matrix at very high levels.
[[Page 24615]]
The octanol-water partition coefficient (Kow) for this substance is on
the order of 17,000 (or in log form, 4.23); this coefficient is a
measure of the tendency of the chemical to partition into organic
phases compared to water, and this value indicates the chemical is
expected to be at 17,000-fold higher concentration in the organic phase
compared to water. It, therefore, would be expected to remain bound in
the organic phase and would tend to be less mobile. Furthermore, the
lower leaching from the spent filter material is also logical, because
the filter material is activated carbon. Activated carbon is used
expressly to remove organic material from a process stream, and the
2,4,6-TBP is expected to be relatively tightly adsorbed to this matrix.
Therefore, EPA has no reason to believe, despite the commenters
assertions, that the TCLP results are not valid for this waste.
EPA's decision to list this waste focused on 2,4,6-TBP because this
chemical was found at levels that greatly exceeded the other
constituents detected. While other constituents were detected in the
waste, many were also found in blank laboratory QC samples (e.g.,
methylene chloride) indicating that the detection of these volatile
constituents in waste samples may have been due to some sample
contamination, perhaps in the laboratory. Concerning arsenic, the
analytical results are suspect due to known problems with measuring
some metals in these type of waste matrices. (See Method 6020, Test
Methods for Evaluating Solid Waste, Physical/Chemical Methods, third
edition, 1994; OSW/USEPA). One of the waste samples (spent carbon
filter material, number GL-08) showed the presence of other brominated
phenols, notably 2,4-dibromophenol; however, EPA does not have any
health-based levels to rigorously evaluate them.
Analysis of the other sample (floor sweepings and off-specification
product, GL-09) showed the presence of several volatile constituents
that were found in the blank samples. However, this sample also
contained significant levels of 1,2-dibromoethane (also known as
ethylene dibromide, or EDB). As evidenced by the very low drinking
water standard established for this chemical (the maximum contaminant
level, or MCL, is 0.00005 mg/L; see 40 CFR 141.61), this substance is
highly toxic, and the level reported in the TCLP analysis (36 mg/L) is
720,000 times the existing MCL. The Agency believes that the relatively
high levels of this chemical in the waste (and the corresponding TCLP
sample) further confirms that these production solids contain high
levels of highly toxic chemicals and present a substantial hazard, even
if managed in a Subtitle C landfill. There is further discussion of the
presence of EDB in the following Unit IV.E.3.
In its reevaluation, EPA did not conclude that the containment
efficiency for a Subtitle c landfill was necessarily 95%. The Agency's
point was, even if the efficiency was as high as 95%, the potential
release from 2,4,6-TBP production solids in a landfill may present
risks at levels of concern. While estimating the long-term efficiency
of containment is highly uncertain, EPA agrees that it may be less than
95%, thereby making the potential risk higher.
e. Other Comments. The commenter that supports EPA's decision to
list the waste at issue noted that the disposal of wastes with high
concentrations of organic contaminants is what Congress sought to
restrict through the Land Disposal Restrictions program. The commenter
argued that a hazardous waste listing for these wastes is appropriate
to ensure Congressional objectives of the LDR program are achieved. The
commenter claims EPA must consider these expressions of ``proper''
management when applying its criteria for listing hazardous waste.
EPA agrees that in establishing the Land Disposal Restrictions
program, Congress found land disposal to be incapable of ensuring long-
term containment of hazardous waste. However, EPA does not agree that
the high content of organic contaminants is, by itself, sufficient to
require listing. The listing decision is based on the highly toxic
nature of the constituent in question (2,4,6,-TBP), in conjunction with
potential risks associated with its release, even if placed in a
Subtitle C landfill. Therefore, EPA agrees that listing, and the
associated treatment required under the land disposal restrictions
program, are appropriate because of the chemicals high toxicity and
potential mobility in groundwater. EPA does not agree that listing is
appropriate merely to comply with Congressional intent for treatment of
hazardous waste, because a waste must first be determined to be
hazardous before the LDR program applies.
One commenter argued that EPA's reevaluation could be read as an
indictment of the Agency's comprehensive Subtitle C program for
managing hazardous wastes in landfills, and indicated that if Subtitle
C disposal is not protective and constitutes mismanagement, then EPA's
landfill standards are inadequate. The commenter does not believe this
is the case and claims the criticism of the long-term integrity of
landfills is an effort to avoid the implications of the Dithiocarbamate
decision. The commenter stated that, even is some uncertain degree of
risk is posed in the long term by such disposal, this uncertainty is
not a sufficient basis for listing these wastes.
As noted elsewhere in response to other related comments, EPA
believes the extensive regulatory controls provide management that
reduces the potential for releases to the environments. EPA's decision
to list the solids from the production of 2,4,6-TBP is in not an
indictment of the Agency's Subtitle C program, but is based on the
specific characteristics of this waste (i.e., toxicity, mobility) and
the potential risks that would occur if these wastes were disposed
without prior treatment, and the long-term containment systems in a
Subtitle C landfill degrade over time, as expected.
3. Comments on the January 14, 1998 Notice Letter
As noted in the above section, a reexamination of the analytical
data of the samples from the 2,4,6-TBP production waste showed that
1,2-dibromoethane (EDB) was found in both the total and TCLP analyses
of the sample of floor sweepings and off-specification product. The EPA
sent a letter of notice to the interested parties (i.e.,the sole
generator of this waste and the commenter that originated the comment
about additional constituents being present in the waste). The letter
explains the new piece of information and notes that the presence of
this highly toxic chemical appears to further support the Agency's
contention that the waste warrants listing. EPA received comments from
the generator, and the Agency's responses are summarized below. The
comments and responses are described in more detail in the docket. (See
``Supplementary Response To Public Comment,'' April 1998).
The commenter challenged the validity of the analytical results
showing the presence of EDB in the waste, because of technical flaws in
the analytical procedure. The commenter collected more samples of the
floor sweepings and product, and submitted chemical analyses that did
not show the presence of EDB. The commenter went on to note that EDB is
not used as a raw material, nor is it produced as a by-product in the
2,4,6-TBP process. The commenter argued that even if the EDB was found
in the floor sweepings, the presence of EDB could not justify the scope
of the Agency's proposed listing. The commenter stated that, since EDB
is
[[Page 24616]]
not present in the 2,4,6-TBP process, its presence would have to be the
result of a mixture of 2,4,6-TBP and EDB.
EPA disagrees with the contention that the Agency's analysis was
flawed. EPA reexamined the raw analytical data for this sample and the
data clearly indicate that EDB was detected and quantified as reported.
EPA has provided a full response in the docket to these and other
comments related to the analysis of the wastes under study (see the
Supplementary Comment Summary & Response Document in the docket). EPA
agrees that EDB does not appear to be used in the 2,4,6-TBP process,
and that it is unlikely to form as a by-product. However, EDB is used
as a raw material elsewhere in the facility, and the raw analytical
data clearly support the finding of EDB in the waste. Therefore its
presence may be due to the cross contamination of waste streams, as the
commenter suggested. The lack of EDB in the recent samples obtained by
the commenter suggest that EDB may not be present in all samples of
waste. Given the limited data, EPA agrees that EDB is not the primary
basis of listing this waste, but that the presence of the 2,4,6-TBP
itself is the major concern.
The commenter stated the Agency did not provide public notice of
its intent to list 2,4,6-TBP production wastes based on the presence of
EDB, and that this is in violation of the Administrative Procedures
Act. Furthermore, the commenter contends that the EPA's ``new
rationale'' to list TBP as hazardous would fail to take into account
the marked shift in emphasis between the proposed and final rules.
As EPA noted in its response to similar comments on the first
notice letter (see subsection 2.a above), due to the limited time EPA
has for completing this action, the Agency decided that a letter of
actual notice to the aforementioned interested parties was appropriate.
The generator of the 2,4,6-tribromophenol production waste is the only
party EPA believes would be affected by the recharacterization of the
rationale for listing and that would have a direct interest in the
final listing decision. The Agency is not aware of any other generators
of this waste, or any other persons who would have a direct interest in
this decision, thus the actual notice given in this case is sufficient.
Finally, the commenter stated that it had not received any response
to its previous comments challenging the use of QSAR as a basis for
alleging that 2,4,6-TBP itself is toxic. The commenter also stated that
EPA does not have any data indicating that 2,4,6-TBP is toxic, and is
instead relying on predictive models that were never intended to be
used for this purpose. The commenter submitted further comments on this
issue.
EPA was not seeking further comments on the use of QSAR in this
listing determination. The Agency's responds to all comments concerning
QSAR submitted on the proposed rule in Units IV.A, IV.B, and IV.C of
today's final rule. These responses are also given in the Public
Comment Summary and Response Document found in the docket as an
appendix to the background document.
F. Listing Determination for Wastes From the Production of
Tetrabromobisphenol-A
1. Solids
In the proposed rule, EPA deferred a hazardous waste listing
decision on waste solids from the production of tetrabromobisphenol-A
(TBBPA), based on a lack of information on waste characterization and
toxicity. In the absence of data on the amount of brominated phenols in
TBBPA product, the leachability of brominated phenols from the product
matrix and toxicological data on TBBPA solids, the EPA was unable to
analyze the potential risks associated with TBBPA migrating to ground
water if managed in unlined landfills. The Agency, accordingly,
requested this information in the proposal and also noted that if
sufficient information to support a listing determination was received
during the public comment period, the Agency may choose to promulgate a
determination rather than defer action in the final rule.
One commenter provided toxicological data on TBBPA that support an
assessment of the potential for environmental risk from release of
TBBPA. (The toxicological data were previously submitted to EPA under
Section 8(d) of the Toxic Substances Control Act (TSCA) and as the
result of a TSCA Section 4 Test Rule.) The test data on the toxicology
of TBBPA indicate that TBBPA product ``does not pose a health hazard to
mammals.'' One reason appears to be that TBBPA is poorly absorbed when
ingested. In 1985, the Interagency Testing Committee reviewed TBBPA and
found no need to conduct further health effects testing. In addition,
the results of ecological testing submitted to the Agency by the
Brominated Flame Retardant Industry Panel do not indicate an
unacceptable level of hazard for aquatic organisms.
Ecological effects data submitted by the commenter (and previously
collected by EPA under TSCA as noted above) indicate that TBBPA is not
particularly toxic to aquatic test species (e.g., fathead minnow,
bluegill, daphia); no long-term aquatic effects are observed with
tetrabromobisphenol-A in water at levels below 0.22 mg/L. Using the
data on fish and assuming that the waste was placed in an unlined
landfill close to a stream into which ground water discharged, the
Agency made a worst-case assumption that leachate from the landfill
would be saturated with tetrabromobisphenol-A at the chemicals
solubility level (4.16 mg/L). This leachate would be diluted before
reaching any nearby stream (in the proposed rule, EPA estimated a
dilution fraction on the order of 100 for leachate exiting a landfill),
and then diluted further after discharge to such a stream. Therefore,
the diluted concentration in the stream after such a scenario would be
well below the above-stated long-term aquatic effect level of 0.22 mg/
L.
In determining potential risk from the TBBPA waste, EPA also
considered the possible risk due to the presence of traces of 2,4,6-TBP
in the TBBPA waste. The commenter provided the Agency with data on
concentrations of 2,4,6-tribromophenol in the TBBPA product. In
considering whether to list spilled product and floor sweepings from
the packaging of TBBPA due to the possible presence of 2,4,6-TBP, EPA
assumed that the 2,4,6-TBP concentration in the spilled product would
be no greater than the 2,4,6-TBP concentration in the TBBPA product
itself. (Note that this appears to be a worst case assumption because
2,4,6-TBP is not handled in the packaging area, thus the spilled
product should not be contaminated with any further 2,4,6-TBP; the
commenter confirmed that waste solids from production of TBBPA are
floor sweepings generated from spills in the packaging area, and not
the production area). The commenter reported that commercial TBBPA has
less than 1% impurities, and the primary impurities are isomers of
tribromobisphenol A, not 2,4,6-TBP. The concentration of 2,4,6-TBP in
the TBBPA product reported by the commenter is more than 100 times less
than the concentration of 2,4,6-TBP EPA found in the off-specification
2,4,6-TBP product.
The TCLP leaching data presented in the proposed rule show a
maximum concentration of 760 mg/l of 2,4,6-TBP in leachate extracts
from the off-specification 2,4,6-TBP product. In the absence of TCLP
leaching data for the TBBPA solids, EPA assumed the TCLP leaching
efficiency of 2,4,6-TBP from the spilled TBBPA product and floor
sweepings would be comparable to the
[[Page 24617]]
leaching efficiency of 2,4,6-TBP measured for the off-specification TBP
product. Thus, the TCLP level for 2,4,6-TBP from the TBBPA solids was
assumed to be more than 100-fold less than the TCLP level found in the
TBP off-specification product. As described in the proposed rule, the
level of estimated individual risk from exposure to 2,4,6-TBP in
groundwater for disposal of the off-specification 2,4,6-TBP product in
an unlined Subtitle D landfill was 7 x 10-4 (with the SAR-
based health number is corrected for molecular weight differences of
2,4,6-TCP and 2,4,6-TBP as noted in today's notice, the risk would be
4.2 x 10-4). Using this analysis, any risk posed by TBBPA
solids under the same disposal scenario would be more than a 100-fold
less, or less than 10--6. Therefore, this waste is not a
candidate for listing as hazardous based on the presence of 2,4,6-TBP.
In addition, EPA has monitoring data that also indicate TBBPA
wastes do not present a significant risk. As stated in the proposed
rule, record sampling of an on-site landfill at one plant where TBBPA
solids formerly were disposed for a number of years showed the absence
of TBBPA and any brominated compounds in the landfill leachate.
Therefore, based on the data submitted by the commenter, the available
data on the limited toxicity of TBBPA noted above, and the monitoring
data, the Agency has decided not to list waste solids from the
production of TBBPA.
2. Wastewaters
As discussed in the proposed rule (59 FR 24537), wastewaters from
the manufacture of tetrabromobisphenol-A already are listed and carry
the hazardous waste code of K131. Methyl bromide and TBBPA are produced
in the same process. One commenter objected to the language used in the
proposed rule to describe the process step that generates wastewaters.
The proposal states ``process wastewater originates from the
distillation step where methyl bromide is recovered.'' The commenter
contended that the wastewater originated from a distillation step where
methanol is recovered. The commenter believed the language in the
proposed rule was inconsistent with the existing listing description
for K131 and was concerned that EPA was attempting to amend the K131
listing as part of this rulemaking.
The Agency concedes that the language used in the proposed rule was
misleading. Indeed, the distillation step is where methanol, or both
methanol and methyl bromide, can be recovered, as described in the
Listing Background Document. The Agency was not referring to a specific
process at any one facility. It was simply attempting to make the point
that TBBPA and methyl bromide are produced in the same process and the
wastewaters arising from that process meet the existing listing
description for K131. As a result, there is no need for further action
on a hazardous waste listing for wastewaters from TBBPA production.
In response to a petition filed by the Ethyl Corporation for
judicial review of the K131 listing, the Agency stayed the K131 listing
as it applies to the ``liquid material exiting the reactor producing
methyl bromide located at Ethyl Corporation's production facility.''
This facility currently recycles the wastewaters, after solids removal,
to the bromine plant for recovery of bromine values. As directed by the
terms of the stay, the Agency is in the process of ``determining
whether the wastewater stream generated at this facility contains a
solid waste and, if so, whether it is eligible for an exemption or
variance.'' EPA clarifies that today's rulemaking does not affect the
Agency's ongoing effort to respond to this petition. EPA is not
attempting to reach a decision on the applicability of the K131 listing
to Ethyl's wastewater stream as part of the listing determination for
wastes from organobromines production.
G. Other Issues
One commenter felt that the model used by the Agency for assessing
migration of 2,4,6-tribromophenol wastewaters from the deep formations
into which they were injected was very conservative and over-estimated
potential risks. The commenter felt that many of the assumptions of the
model describe physical conditions that are known not to exist.
In response, the Agency notes that the model was intended to
represent a conservative scenario in order to identify any potential
risk if leakage were to occur. The Agency reexamined the record and
agrees that the existing data collected for the site suggest that the
release scenario modeled is not likely to exist. The information
available indicates that the only abandoned wells found in the area of
the injection wells that are deep enough to penetrate the injection
zone are in fact known to be plugged and should not serve as potential
conduits for release of waste constituents from the injection zone to
the upper drinking water aquifer. Furthermore, as noted in the proposed
rule, sampling of drinking water wells on the plant site and in the
vicinity of the plant did not find any trace of tribromophenol in the
groundwater, even though disposal has been occurring for nearly twenty
years. In any case, the comment is moot, since EPA has decided not to
list wastewaters from the production of 2,4,6-TBP.
One commenter requested that the Agency provide a detailed
definition of the term ``production'' as used in the proposed listing
description for K140. The commenter suggested that production be
defined to limit the reach of the listing to wastes resulting from the
actual synthesis of 2,4,6-TBP (i.e., the listing should not encompass
wastes from processes that isolate an intermediate or a product other
than 2,4,6-TBP).
The Agency does not believe it is necessary for this final rule to
define ``production'' because the majority of wastes listed in 40 CFR
261.37 include the unambiguous term ``production.'' The fact that
intermediates or co-products may arise from the same process that
produces 2,4,6-TBP is irrelevant to the basis for listing the process
wastes from the production of 2,4,6-TBP. If listings were constructed
so narrowly as to capture wastes from the production of a given product
only when the process produced that product alone, vast amounts of
process waste containing similarly hazardous constituents would remain
unregulated. In this case, by manipulating the process, a producer of
tribromophenol may co-produce di-, tetra-, or penta-brominated phenols
along with tribromophenol from the same process. If the listing were
crafted the way the commenter suggests, the operator of such a process
would escape the intent of this regulation, while still producing
2,4,6-TBP.
One commenter expressed concern that the proposed rule may have the
unintended effect of increasing the land disposal of wastes containing
2,4,6-TBP by preventing their use as feedstocks to bromine recovery
units (BRUs). EPA does not agree with this statement. The listing of
TBP production wastes should not affect the current management of these
materials in BRUs. EPA clarifies that BRUs are halogen acid furnaces,
which meet the definition of industrial furnace in 40 CFR 260.10. As
stated in the proposed rule, the combustion of hazardous waste in
industrial furnaces is regulated under 40 CFR part 266, subpart H. The
commenter noted that EPA issued a correction notice on August 27, 1991
that excluded from regulation certain brominated materials combusted in
halogen acid furnaces (56 FR 42504). The Agency agrees that the
provision added by the correction notice effectively excludes
brominated materials meeting the criteria in 40 CFR 261.2(d)(2)(i)-
(iii) from designation as
[[Page 24618]]
``inherently waste-like'' materials. Accordingly, these materials are
not hazardous wastes; thus, furnaces processing them are not processing
hazardous wastes and are not subject to the BIF regulations. Listed and
characteristic brominated streams that do not meet the criteria of 40
CFR 261.2(d)(2), i.e., that contain >1% of Appendix VIII materials, are
considered inherently waste-like and should not be burned in non-RCRA
facilities. Today's listing of TBP wastes does not alter the criteria
of this exclusion nor subject the commenter's BRUs to any additional
requirements. If the commenter's brominated waste streams meet the
criteria for the exclusion, the BRUs to which these streams are fed are
not subject to regulation under part 266, subpart H.
Finally, the Agency notes that the sole generator of the 2,4,6-
tribromophenol production solids did not attempt to use this material
as feedstock for the BRU, even in the absence of a hazardous waste
listing.
One commenter questioned the accuracy of early sampling and
analysis results obtained at one facility. This commenter submitted a
letter to the Agency in 1993 detailing concerns over the quality and
accuracy of some of the analytical results. The commenter concluded in
the 1993 letter, ``There are a great many non-credible and questionable
analyses in this study. We believe that the analytical work will simply
not stand up to close scrutiny. The analytical results are not of a
quality that lend themselves to making a valid risk assessment or
developing regulations for the organo-bromine industry. The validity
and accuracy simply aren't there.'' EPA prepared a complete response to
the issues enumerated in that letter and has placed it in the public
docket for today's rulemaking. EPA notes that none of the questioned
data were used as a basis for the decision to list wastes from the
production of 2,4,6-tribromophenol.
V. Conclusions
The Agency is listing, as EPA Hazardous Waste No. K140, floor
sweepings, off-specification product, and spent filter media from the
production of 2,4,6-tribromophenol. EPA is also listing discarded
2,4,6-TBP product as EPA Hazardous Waste No. U408. EPA received no
comments objecting to the listing of U408, except to the extent that
issues relating to SAR may be considered relevant to the U408 listing.
(EPA notes, however, that the analysis completed for the listing of
K140 also included an evaluation of the risks posed by off-
specification 2,4,6-tribromophenol product. Such off-specification
product should be very similar to discarded material that might carry
the U408 listing and, as such, the discarded U-waste may present
comparable risks and is even more likely to be disposed of in an
unlined landfill). EPA responded above, and in the separate Response to
Public Comment Document, to all comments on the SAR analysis. These
listing determinations are based on the projected toxicity of 2,4,6-TBP
from structural activity studies, and the assessment of risk from
potential exposure to this chemical. EPA's decision to list these
wastes as hazardous represents a determination by the Agency that the
wastes identified in this action meet the criteria for listing
hazardous wastes presented in 40 CFR 261.11. Specifically, based on
available evidence, the Agency concludes that 2,4,6-tribromophenol is
similar in toxicity to its chlorinated analogue (2,4,6-trichlorophenol)
and, therefore, may pose a risk to human health and the environment if
improperly land-disposed.
Based on the data collected by the Agency during the recent
organobromines industry study and the unique conditions of the industry
regarding limitations to future expansion, EPA believes there is ample
justification for a no-list determination for wastes generated from
production of the other organobromine chemicals identified in the
proposed consent decree (i.e., tetrabromobisphenol A,
bromochloromethane, ethyl bromide, octabromodiphenyl oxide, and
decabromodiphenyl oxide) and for wastewaters from 2,4,6-tribromophenol
production. After considering the collected information and data from
toxicological, chemical, hydrogeological, and engineering viewpoints,
EPA has concluded that the disposal of any wastes from these processes
that are not currently listed in 40 CFR part 261, subpart D does not
pose a substantial present or future risk to human health or the
environment. Therefore, EPA is not listing any additional hazardous
wastes generated from the production of these chemicals. The Agency
received no comments objecting to its decision not to list these
wastes.
VI. Land Disposal Restrictions
A. Treatment Standards for Organobromine Wastes
In the land disposal restrictions Phase III proposed rule (60 FR
11722, March 2, 1995), EPA proposed that the newly identified K140 and
U408 wastes comply with numerical treatment standards for 2,4,6-
tribromophenol to be promulgated in 40 CFR 268.40, and that 2,4,6-
tribromophenol be added as a underlying hazardous constituent subject
to the universal treatment standards of 40 CFR 268.48.
Since treatment data currently are not available for 2,4,6-TBP, the
Agency proposed to set the UTS for 2,4,6-TBP based on analytical
detection limit data transferred from 2,4,6-trichlorophenol. The
structures of 2,4,6-tribromophenol and 2,4,6-trichlorophenol are
sufficiently similar to be considered halogenated congeners of phenol.
Both halogenated phenols contain three symmetrically placed bromine or
chlorine substituents that are difficult to remove by chemical
substitution. The chemical behavior and mechanisms of action for 2,4,6-
tribromophenol are expected to be similar to its chlorinated analogue,
2,4,6-trichlorophenol. Thus, the Agency proposed the treatment
standards for 2,4,6-tribromophenol at 7.4 mg/kg for nonwastewaters and
0.035 mg/L for wastewaters for 2,4,6-tribromophenol.
The Agency solicited comment regarding the achievability of this
standard by demonstrated available technologies and regarding the
analytical detection limit of 2,4,6-TBP in treatment residual matrices.
The Agency also solicited any available data on the concentrations
2,4,6-TBP in treatment residuals from the recovery or destruction of
wastes containing 2,4,6-TBP. The analytical method for 2,4,6-TBP is SW-
846 method 8270 (GC/MS for semivolatiles, capillary column).
In response to the Agency's request for comment, Chemical Waste
Management, Inc. supported the Agency's proposed treatment standards
associated with organobromine wastes; the Environmental Technology
Council, while objecting to setting treatment standards on the sole
basis of analytical detection limits, noted that EPA can use technology
transfer to develop standards from similar chlorinated organics.
Therefore, EPA is promulgating the proposed UTS for 2,4,6-TBP at 7.4
mg/kg for nonwastewaters and 0.035 mg/L for wastewaters.
B. Applicable Technology
The single facility that produces 2,4,6-TBP wastes uses a bromine
recovery unit (BRU) to recover bromine values from organic liquid and
vapor waste streams. In this unit, the organics are burned and the
combustion products are removed by a wet scrubber. The BRU is a halogen
acid furnace which meets the regulatory definition of industrial
furnace in 40 CFR 260.10. The
[[Page 24619]]
combustion of hazardous waste in industrial furnaces is regulated under
40 CFR part 266, subpart H, which regulates air emissions from these
units and requires monitoring and analyses.
Treatment of 2,4,6-TBP wastes in the BRU should be effective in
destroying the phenolic component of 2,4,6-tribromophenol and providing
for recovery of bromine. Based on available information, EPA proposed
that the best demonstrated available technology (BDAT) for 2,4,6-
tribromophenol wastes is treatment by BRU. EPA solicited comment on
this assertion and on the potential applicability of other technologies
which destroy 2,4,6-tribromophenol and provide recovery of bromine.
Great Lakes Chemical Corporation (GLCC) commented that EPA's
assumption that TBP waste generated by GLCC currently is managed in a
bromine recovery unit (BRU) is incorrect. GLCC maintains that treatment
of TBP in the existing BRU would be very difficult, if not impossible
(both technically and legally). Accordingly, GLCC concluded that the
proposed TBP treatment standard is flawed. The Agency disagrees.
Because tribromophenol is not refractory, EPA believes the BRU
technology clearly is applicable to waste treatment of the K140 and
U408 wastes and, therefore, may form the basis of a standard. There are
various combustion technologies capable of meeting the numerical
treatment standards, one of which is BRU. The Agency stated in error in
the proposal that the existing BRU already is subject to the
performance standards of part 266, subpart H. However, in order to
treat the listed organobromine wastes, the subject BRU would be subject
to the part 266, subpart H performance standards. EPA has assessed the
costs associated with incineration of the newly identified
organobromine wastes as part of its regulatory impact analysis. See the
regulatory impact analysis discussion in Section X of this preamble.
Because the Agency has promulgated the universal treatment standards
for the organobromine wastes, treaters are free to use any technology
capable of achieving the numerical standard promulgated today (so long
as the standard is not achieved by means of impermissible dilution).
C. Capacity Analysis Results Summary
1. Introduction
This section summarizes the results of the capacity analysis for
the wastes covered by today's rule. For a detailed discussion of
capacity analysis-related data sources, methodology, and detailed
response to comments for each group of wastes covered in this rule, see
the following document: ``Background Document for Capacity Analysis for
Land Disposal Restrictions: Surfaced-disposed Organobromine Production
Wastes (Final Rule)'' (i.e., the Capacity Background Document).
When EPA establishes land disposal restrictions (LDR)
determinations, LDR treatment standards become effective when
promulgated unless the Agency grants a national capacity variance
delaying the effective date. RCRA section 3004(h)(2), 42 U.S.C.
6924(h)(2) authorizes EPA to grant a national capacity variance for the
waste and to establish a different date (not to exceed two years beyond
the statutory deadline) based on ``* * * the earliest date on which
adequate alternative treatment, recovery, or disposal capacity which
protects human health and the environment will be available'' if there
is inadequate alternative treatment/recovery capacity.
In general, EPA's capacity analysis focuses on the amount of waste
to be restricted from land disposal that is currently managed in land-
based units and will therefore require alternative treatment as a
result of the LDRs. The quantity of wastes that are not managed in
land-based units (e.g., wastewater managed only in RCRA exempt tanks,
with discharge to a Publicly Owned Treatment Works (POTW)) is not
included in the quantities requiring alternative treatment as a result
of the LDRs. Also, wastes that do not require alternative treatment
(e.g., those that are currently treated using an appropriate treatment
technology) are not included in these quantity estimates. Land-disposed
wastes requiring alternative treatment or recovery capacity that is
available on-site or within the same company as the generator are also
omitted from the required commercial capacity estimates.
EPA's decisions on whether to grant a national capacity variance
are based on the availability of alternative treatment or recovery
technologies. Consequently, the methodology focuses on deriving
estimates of the quantities of waste that will require either
commercial treatment or the construction of new on-site treatment or
recovery unit as a result of the LDRs. The resulting estimates of
required commercial capacity are then compared to estimates of
available commercial capacity. If adequate commercial capacity exists,
the waste is restricted from further land disposal before meeting the
LDR treatment standards. If adequate capacity does not exist, RCRA
section 3004(h) authorizes EPA to grant a national capacity variance
for the waste for up to two years or until adequate alternative
treatment or recovery capacity becomes available.
2. Capacity Analysis Results Summary
A brief summary of the capacity analysis performed to support this
rule is presented below. For additional detailed information, please
refer to the ``Background Document for Capacity Analysis for Land
Disposal Restrictions: Surfaced-disposed Organobromine Production
Wastes (Final Rule)''.
For this capacity analysis, EPA examined data on waste
characteristics and management practices that have been gathered for
the organobromine production industry study in the 1992 RCRA Section
3007 survey. The Agency analyzed the capacity-related information from
the survey responses, reviewed the public comments received in response
to the proposed rule, and identified the following annualized
quantities of newly listed hazardous wastes requiring commercial
treatment: Less than 100 tons of organobromine nonwastewater wastes
(K140, U408) are expected to require alternative treatment capacity.
The available data sources indicate that there are no quantities of
K140 and U408 wastewaters that will require alternative commercial
treatment, and therefore this volume is assumed to be zero.
EPA is finalizing the rule to apply UTS to these wastes. The
treatment standards for organobromine production wastes are
concentrations which in turn are based on bromine recovery unit as the
BDAT. Additionally, EPA believes that incineration and thermal
destruction technologies are applicable technologies to meet these
treatment standards. The Agency estimated that the commercially
available sludge and solid combustion capacity is approximately 430,000
MT per year and sufficient to treat these wastes when the listing
determinations for these wastes become effective. Since EPA is
finalizing numerical standards for these wastes, the Agency does not
exclude the use of other technologies capable of meeting the final LDR
treatment standards. Sufficient commercial capacity exists to treat
theses wastes to meet the LDR standards. Therefore, EPA is not granting
a national capacity variance under LDR for these wastes. The LDR
standards for these wastes will become effective when the listings
become effective.
For soil and debris contaminated with the newly listed wastes, EPA
proposed to not grant a national capacity variance. EPA received no
comments regarding
[[Page 24620]]
this issue. EPA believes that the contaminated soil and debris can be
managed on-site or if necessary, off-site commercial treatment capacity
is available. Therefore, EPA is not granting a national capacity
variance to hazardous soil and debris contaminated with the newly
listed wastes covered under this rule. Based on the questionnaire,
there were no data showing the mixed radioactive wastes with the newly
listed wastes. There were also no comments concerning the radioactive
wastes mixed with the newly identified wastes. EPA is not granting a
national capacity variance for mixed radioactive wastes or soil and
debris contaminated with these mixed radioactive wastes.
VII. Waste Minimization Opportunities in the Industry
During the industry study, the Agency identified two potential
opportunities for waste minimization. The first involves the recovery
of tribromophenol in the tetrabromobisphenol-A and tribromophenol
process. Commercial tetrabromobisphenol-A is made by condensation of
phenol and acetone and, hence, the feedstock contains some unreacted
phenol. Record sampling of one wastewater stream, which leaves the
process hot, revealed that it contained tribromophenol. The Agency
appreciates the effort that the commenter has made to recover TBP and
understands the difficulty of recovering pure product. The Agency
received some information from the two manufacturers of TBBPA. One firm
claimed the idea was impractical. The second has installed a process to
recover a low-grade material which is a mixture containing
underbrominated bisphenol-A compounds. It is yet unknown if this
material can be marketed successfully as a low-grade flame retardant
formulation. The facility has informed the Agency that if the material
cannot be marketed it will be sent to Subtitle C facilities for
disposal. This plant also is recycling the wastewater, after solids
removal, to the bromine plant for recovery of bromine from the sodium
bromide present. Removal of the solids is necessary to prevent problems
in the bromine recovery operation.
The second area where savings could be achieved is in product
packaging. Materials spilled in the packaging areas are drummed and
shipped to Subtitle C facilities. Presently, the two major
manufacturers of organobromine chemicals generate over 300 tons per
year of various spilled solid products. Improved housekeeping in the
packaging areas will reduce the volumes of these wastes.
VIII. State Program Implementation
A. Applicability of Rules in States
Under section 3006 of RCRA, EPA may authorize qualified States to
administer and enforce RCRA programs within the State. (See 40 CFR part
271 for the standards and requirements for authorization.) Following
authorization EPA retains enforcement authority under sections 3008,
7003, and 3013 of RCRA, although authorized States have primary
enforcement responsibility.
Prior to the Hazardous and Solid W
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