[Federal Register Volume 63, Number 248 (Monday, December 28, 1998)]
[Notices]
[Pages 71542-71568]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-34298]



[[Page 71541]]

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Part II





Environmental Protection Agency





_______________________________________________________________________



Endocrine Disruptor Screening Program: Statement of Policy; Notice

Endocrine Disruptor Screening Program: Priority-Setting Workshop; 
Notice

  Federal Register / Vol. 63, No. 248 / Monday, December 28, 1998 / 
Notices  

[[Page 71542]]



ENVIRONMENTAL PROTECTION AGENCY

[OPPTS-42208; FRL-6052-9]


Endocrine Disruptor Screening Program; Proposed Statement of 
Policy

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice.

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

SUMMARY: In this notice, EPA is providing additional details and an 
opportunity for public comment on its Endocrine Disruptor Screening 
Program (EDSP). The Agency first set forth the basic components of the 
EDSP in the August 11, 1998, Federal Register. The EDSP is required by 
the Federal Food, Drug, and Cosmetics Act (FFDCA), as amended by the 
Food Quality Protection Act (FQPA). In developing the EDSP, EPA 
considered recommendations of the Endocrine Disruptor Screening and 
Testing Advisory Committee (EDSTAC), a panel chartered pursuant to the 
Federal Advisory Committee Act. EDSTAC recommended expansion of the 
screening program beyond the statutory minimum to include not only 
pesticides but commercial chemicals regulated under the Toxic 
Substances Control Act (TSCA), certain natural products, non-pesticide 
food additives, and cosmetics. EDSTAC also recommended that EPA screen 
for effects on the androgen and thyroid systems and for effects on fish 
and wildlife. This notice describes the major elements of EPA's EDSP, 
as well as its implementation. EPA is seeking public comment on the 
EDSP in this notice.

 DATES: Written comments on this proposed policy must be received by 
EPA on or before February 26, 1999.
    The joint meeting of the EPA Science Advisory Board (SAB) and 
Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) Scientific 
Advisory Panel (SAP) to review EPA's proposal for the EDSP will be held 
March 30 through April 1, 1999. A document announcing the meeting sites 
and times will be published in the Federal Register.

ADDRESSES: Each comment must bear the docket control number OPPTS-
42208. All comments should be sent in triplicate to: OPPT Document 
Control Officer (7407), Office of Pollution Prevention and Toxics, 
Environmental Protection Agency, 401 M St., SW., Room G-099, East 
Tower, Washington, DC 20460.
    Comments and data may also be submitted electronically to: oppt. 
[email protected]. Follow the instructions under Unit IX. of this notice. No 
Confidential Business Information (CBI) should be submitted through e-
mail.
    All comments which contain information claimed as CBI must be 
clearly marked as such. Three sanitized copies of any comments 
containing information claimed as CBI must also be submitted and will 
be placed in the public record for this rulemaking. Persons submitting 
information on any portion of which they believe is entitled to 
treatment as CBI by EPA must assert a business confidentiality claim in 
accordance with 40 CFR 2.203(b) for each such portion. This claim must 
be made at the time that the information is submitted to EPA. If a 
submitter does not assert a confidentiality claim at the time of 
submission, EPA will consider this as a waiver of any confidentiality 
claim and the information may be made available to the public by EPA 
without further notice to the submitter.

FOR FURTHER INFORMATION CONTACT:  For general information or copies of 
the EDSTAC Final Report: TSCA Hotline, Environmental Assistance 
Division (7408), Office of Pollution Prevention and Toxics, 
Environmental Protection Agency, 401 M St., SW., Washington, DC 20460; 
telephone (202) 554-1404, TDD (202) 554-0551; e-mail address: TSCA-
H[email protected]. For technical information, please contact Anthony 
Maciorowski, Office of Pesticide Programs, telephone: (202) 260-3048, 
e-mail address: [email protected] or Gary Timm, Chemical 
Control Division, Office of Pollution Prevention and Toxics, telephone: 
(202) 260-1859, e-mail address: [email protected].

SUPPLEMENTARY INFORMATION
Table of Contents

I. General Information

A. Does this notice apply to me?
B. How can I get additional information or copies of this notice or 
other support document?

II. Background

A. Concern Regarding Endocrine Disruption
B. The Food Quality Protection Act, Safe Drinking Water Act, and 
Other Environmental Legislation
C. The EDSTAC
D. Key Terms and Definitions

III. Overview of the Screening Program

A. Scope
B. Program Elements

IV. Sorting and Priority Setting

A. The Universe of Chemicals Included in the EDSP
B. Sorting
C. Information Required for Priority Setting
D. Use of a High Throughput Pre-Screen (HTPS) to Assist Priority 
Setting
E. Setting Priorities for Tier 1 Screening
F. Bypassing Tier 1 Screening
G. Mixtures
H. Categories of Chemicals

V. Screening Program

A. Tier 1 Screening
B. Tier 2 Testing
C. Route of Administration

VI. Implementation

A. Overview of Implementation Steps and Timeline
B. HTPS Demonstration
C. HTPS Priority-Setting Project
D. Priority-Setting Data Base (EDPSD) Development
E. Process for Public Nominations for Chemical Screening
F. Standardization and Validation of Assays, Screening Battery, and 
Tests
G. Implementation Mechanisms
H Data Compensation Issues
I. Data Submission and Collection
J. Data Release and CBI
K. Reporting Requirements Under TSCA 8(e) and FIFRA 6(a)(2)
L Exemptions
M. Use of Significant New Use Rules (SNURs) under TSCA
N. Relationship Between the EDSP and Related Actions Under TSCA
O. Analysis of Data in the EDSP

VII. Issues for Comment

VIII. References

IX. Public Record and Electronic Submissions

I. General Information

A. Does this notice apply to me?

     This notice describes the major elements of EPA's EDSP, and also 
requests public comments on technical and policy aspects of the 
program. You may be interested in the program set forth in this notice 
if you produce, manufacture or import pesticide chemicals, chemical 
substances or mixtures subject to TSCA, substances that may have an 
effect cumulative to an effect of a pesticide, or substances found in 
sources of drinking water. The general public may also have an interest 
in the potential health and environmental consequences associated with 
the results of any testing that is conducted in conformity with this 
policy. If you have any questions regarding the applicability of this 
action to a particular entity, consult the technical person listed 
under ``FOR FURTHER INFORMATION CONTACT.''

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

    1. Electronically. You may obtain electronic copies of this notice 
and various support documents from the EPA Home Page at http://
www.epa.gov/. On the EPA Home Page select ``Laws

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and Regulations'' and then look up the entry for this notice under 
``Federal Register--Environmental Documents.'' You can also go directly 
to the ``Federal Register'' listings at http://www.epa.gov/fedrgstr/.
    The complete EDSTAC Final Report is available on the worldwide web 
at: www.epa.gov/opptintr/opptendo/whatsnew.htm. Paper copies of the 
EDSTAC Final Report can be obtained upon request from the TSCA Hotline 
at the address listed under ``FOR FURTHER INFORMATION CONTACT'' section 
of this notice.
    2. In person or by phone. If you have any questions or need 
additional information about this action, please contact the technical 
person identified under ``FOR FURTHER INFORMATION CONTACT.'' A public 
version of this record, including printed, paper versions which does 
not include any information claimed as CBI, is available for inspection 
in the TSCA Nonconfidential Information Center, Rm. NE-B607, 401 M St., 
SW., Washington, DC, 12 noon to 4 p.m., Monday through Friday, 
excluding legal holidays. The telephone number of the TSCA Docket is 
(202) 260-7099.

II. Background

A. Concern Regarding Endocrine Disruptors

    The endocrine system consists of glands and hormones which are 
found in all mammals, birds, fish, and invertebrates. Hormones are 
biochemical substances produced in glands and released into the blood 
stream to act on an organ in another part of the body. Over 50 hormones 
have been identified in humans and other vertebrates. Hormones control 
or regulate many biological processes and are often produced in 
exceptionally low amounts within the body. Examples of such processes 
include blood sugar control (insulin); differentiation, growth, and 
function of reproductive organs (testosterone (T) and estradiol); and 
body growth and energy production (growth hormone and thyroid hormone). 
Much like a lock and key, many hormones act by binding to receptors 
that are produced within cells. The hormone-receptor complex switches 
on or switches off specific biological processes in cells, tissues, and 
organs.
    Scientific evidence has been accumulating that humans, domestic 
animals, and fish and wildlife species have exhibited adverse health 
consequences from exposure to environmental chemicals that interact 
with the endocrine system. To date, such problems have been detected in 
domestic or wildlife species with relatively high exposure to 
organochlorine compounds (e.g., 1,1,1-trichloro-2,2-bis(p-chlorophenyl) 
ethane (DDT) and its metabolite dichorodiphenyldichloroethylene (DDE), 
polychlorinated biphenyls (PCBs), and dioxins) or to some naturally 
occurring plant estrogens. But effects from exposure to low levels of 
endocrine disruptors has been observed as well (e.g., parts per 
trillion levels of tributyl tin have caused masculinization of female 
marine molluscs such as the dog whelk and ivory shell). Adverse effects 
have been reported for humans exposed to relatively high concentrations 
of certain contaminants. However, whether such effects are occurring in 
the human population at-large at concentrations present in the ambient 
environment, drinking water, and food remains unclear. Several 
conflicting reports have been published concerning declines in the 
quality and quantity of sperm production in humans over the last 4 
decades, and there are reported increases in certain cancers (e.g., 
breast, prostate, testicular). Such effects may have an endocrine-
related basis, which has led to speculation about the possibility that 
these endocrine effects may have environmental causes. However, 
considerable scientific uncertainty remains regarding the actual causes 
of such effects. Nevertheless, there is little doubt that small 
disturbances in endocrine function, particularly during certain highly 
sensitive stages of the life cycle (e.g., development, pregnancy, 
lactation) can lead to profound and lasting effects (Kavlock et al., 
1996. EPA, 1997).
    Taken collectively, the body of scientific research on human 
epidemiology, laboratory animals, and fish and wildlife provides a 
plausible scientific hypothesis that environmental contaminants can 
disrupt the endocrine system leading to adverse-health consequences. A 
critical issue is whether ambient environmental levels are sufficiently 
high to exert adverse effects on the general population. Various types 
of scientific studies (epidemiology, mammalian toxicology, and 
ecological toxicology) are necessary to resolve many of the scientific 
questions and uncertainty surrounding the endocrine disruptor issue. 
Many such studies are currently underway by government agencies, 
industry, and academia.

B. The Food Quality Protection Act, Safe Drinking Water Act, and Other 
Environmental Legislation

    In 1996, Congress amended the FFDCA with the FQPA. FFDCA section 
408(p) requires EPA to develop a program ``to determine whether certain 
substances may have an effect in humans that is similar to an effect 
produced by a naturally occurring estrogen, or such other endocrine 
effects as [EPA] may designate'' (FFDCA section 408(p) (21 U.S.C. 
346a(p))).
    When carrying out the program, EPA ``shall provide for the testing 
of all pesticide chemicals'' and ``may provide for the testing of any 
other substance that may have an effect that is cumulative to an effect 
of a pesticide chemical if the Administrator determines that a 
substantial population may be exposed to such a substance'' (21 U.S.C. 
346a(p)(3)).
    In addition, Congress amended the Safe Drinking Water Act (SDWA) 
and gave EPA authority to provide for the testing, under the FQPA 
Screening Program, ``of any other substance that may be found in 
sources of drinking water if the Administrator determines that a 
substantial population may be exposed to such substance'' (SDWA 
Amendments of 1996, section 136 (42 U.S.C. 300j-17)).
    This notice describes the major elements of the program EPA has 
developed to comply with the requirements of FFDCA section 408 (p) as 
amended by FQPA. EPA initially set forth the Program in an August 11, 
1998, Federal Register notice (63 FR 42852) (FRL-6021-3). The screening 
program described in this notice is ambitious. EPA is considering 
87,000 substances as potential candidates for testing. EPA believes 
that the FFDCA and SDWA provide authority to require the testing of 
many of these substances. EPA will use other testing authorities under 
the FIFRA and TSCA to require the testing of those chemical substances 
that the FFDCA and SDWA do not cover. EPA also plans to work with other 
Federal agencies and departments to ensure that substances not covered 
under any of EPA's authorities are tested.
     As described in detail in this unit, the EDSP is divided into 
several stages, including a priority-setting stage, a stage involving 
screening tests (Tier 1 screening), and a stage involving confirmatory 
testing (Tier 2 testing). EPA believes that the results from the entire 
battery of tests required in the Tier 1 screening and Tier 2 testing 
stages (or their equivalents) are necessary to make the statutory 
determination of whether a particular

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substance ``may have an effect in humans that is similar to an effect 
produced by a naturally occurring [hormone]''(21 U.S.C. 346a(p)). In 
other words, a positive result in the Tier 1 screening assays would not 
be adequate to make the determination ``whether a substance may have an 
effect in humans that is similar to an effect produced by a naturally 
occurring [hormone].'' Id. Conversely, a negative result in all Tier 1 
screening tests will be adequate to determine that a particular 
substance is not likely to have an effect on the estrogen, androgen, 
and thyroid hormone systems (EAT) and, therefore, is not a priority for 
testing in Tier 2. The confirmatory tests in the Tier 2 testing stage 
are necessary to determine whether a substance may have an effect 
similar to that of a naturally occurring hormone.

C. The EDSTAC

    Recognizing the expertise available outside the Agency on endocrine 
disruptor issues, as well as the evolving nature of the science 
surrounding endocrine disruption, EPA chartered an advisory committee 
under the Federal Advisory Committee Act to advise it on developing a 
program to comply with FFDCA section 408(p) requirements. The Advisory 
Committee, known as the EDSTAC, was comprised of members representing 
the commercial chemical and pesticides industries, Federal and State 
agencies, worker protection and labor organizations, environmental and 
public health groups, and research scientists. EPA charged the EDSTAC 
with providing advice and recommendations to the Agency regarding a 
strategy for testing chemical substances to determine whether they may 
have an effect in humans similar to an effect produced by naturally 
occurring hormones. Specifically, EPA charged EDSTAC with developing 
the following:
    Methods for chemical selection and priorities for screening.
    1. A set of available, validated screening tests for early 
application.
    2. Ways to identify new and existing screening tests and mechanisms 
for their validation.
    3. Processes and criteria for deciding when additional tests beyond 
screening would be needed and how to validate such tests.
    4. Processes for communicating to the public about the EDSTAC's 
agreements, recommendations, and information developed during priority 
setting, screening, and testing.
    In response to this charge, EDSTAC reached consensus on a set of 
recommendations for the Agency. These recommendations are contained in 
the EDSTAC Final Report (EDSTAC, 1998). Considering EDSTAC's diverse 
membership--including individuals from industry, labor, environmental 
justice groups, public health and environmental groups, academia, and 
Federal and State agencies--EPA found its consensus compelling. More 
importantly, EPA found the advice contained in the EDSTAC Final Report 
scientifically rigorous. As such, EPA relied heavily on EDSTAC's advice 
and recommendations in developing its EDSP. EPA has not further 
developed recommendations in areas where EDSTAC recommended further 
stakeholder involvement. However, in other areas, EPA has added 
additional refinements which are highlighted under ``Issues for 
Comment'' in Unit VII. of this notice.

D. Key Terms and Definitions

    For the purposes of this notice, EPA will use the following 
definitions.
    Chemical or chemical substance as used in this notice includes 
naturally occurring and synthetic chemicals and elements.
    Commercial chemical is defined as chemical substances subject to 
the provisions of TSCA (15 U.S.C. 2602 et seq.).
    Exempted chemicals are pesticide chemicals that have been given an 
exemption under FFDCA section 408(p) or commercial chemicals that the 
Agency determines to exempt from the requirements of screening and are 
therefore not subject to the EDSP.
    Functional equivalency--an assay, test, or endpoint may be defined 
as being ``functionally equivalent'' to another assay, test, or 
endpoint when it provides equivalent information for each endpoint 
being studied. For purposes of the EDSP, assays, tests, and endpoints 
must be standardized and validated prior to use. The standardization 
and validation process will provide data and information that will 
allow EPA to develop guidance on the use of functionally equivalent 
assays, tests, and endpoints prior to the implementation of the 
screening program.
    Hazard assessment is defined to include identification of the 
chemical substances and mixtures that have endocrine-disruption effects 
(which is often referred to as hazard identification) and establishment 
of the relationship between dose and effect (which is often referred to 
as dose-response assessment).
    Mixtures refers to combinations of two or more chemical substances, 
including those found in the environment. This definition is the 
ordinary definition applied by chemists and differs from the legal 
definition under TSCA section 3. The TSCA definition of mixture 
excludes natural products and chemical reaction products that may be a 
combination of two or more chemical substances.
    Pesticide chemical means any substance that is a pesticide within 
the meaning of FIFRA, including all active and inert ingredients of 
such pesticide and all impurities.
    Polymer is defined as a chemical substance consisting of one or 
more types of monomer units and comprising a simple weight majority of 
molecules containing at least three monomer units which are covalently 
bound to at least one other monomer unit or other reactant and which 
consists of less than a simple weight majority of molecules of the same 
molecular weight. Such molecules must be distributed over a range of 
molecular weights wherein differences in the molecular weight are 
primarily attributable to differences in the number of monomer units.
    Priority setting is defined as the collection, evaluation, and 
analysis of relevant information, including the results of HTPS, to 
determine the general order in which chemical substances or mixtures 
will be subjected to screening and testing.
    Screening is defined as the application of short-term assays to 
determine whether a chemical substance or mixture may interact with the 
endocrine system. As these are preliminary assays, a positive result 
during screening does not mean that a chemical substance may have an 
effect in humans, fish, or wildlife that is similar to the effect 
produced by naturally occurring hormones.
    Sorting is the separation of chemicals into groups prior to 
priority setting for the purpose of distinguishing chemicals needing 
Tier 1 screening from those needing Tier 2 testing, hazard assessment, 
and those for which endocrine screening, testing, or hazard assessment 
is not warranted at this time.
    Testing is defined as a customized combination of long-term assays 
and endpoints designed to determine whether a chemical substance or 
mixture may cause effects in humans, fish, or wildlife that are similar 
to effects caused by naturally occurring hormones and to identify, 
characterize, and quantify these effects. Tests are designed to confirm 
and further define the results obtained in Tier 1 screens.
    Weight-of-evidence refers to the process by which trained 
professionals judge the strengths and weaknesses of a collection of 
information to render an

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overall conclusion that may not be evident from consideration of the 
individual data.

III. Overview of the Screening Program

A. Scope

    Based on the body of available scientific information, EDSTAC 
recommended that EPA's EDSP address both human and ecological (fish and 
wildlife) effects; examine effects to EAT-related processes; and 
include chemical substances and representative mixtures. EPA fully 
agrees with the EDSTAC that this is the appropriate scope for the 
initial EDSP.
    For the reasons stated in this unit, EPA is proposing that the EDSP 
include the following:
    1. Human and ecological (fish and wildlife) effects. Adverse 
effects on wildlife and fish can serve as an early warning of potential 
health risks for humans. There is strong evidence for endocrine 
disruption observed in natural wildlife and fish populations. Moreover, 
wildlife and fish are inherently valuable components of ecosystems, and 
they act as sentinels for the relative health of the environment that 
they share with humans.
    2. Effects on EAT-related processes. Initially, the EDSP will focus 
on EAT effects. These three hormone systems are presently among the 
most studied of the approximately 50 known vertebrate hormones. In 
vitro and in vivo test systems to examine EAT effects exist, and are 
currently the most amenable for regulatory testing. Further, inclusion 
of EAT effects will cover aspects of reproduction, development, and 
growth.
    EPA recognizes that there is a great deal of ongoing research 
related to other hormones and test systems. As more scientific 
information becomes available, EPA will consider expanding the scope of 
the EDSP to other hormones. For now, however, the EAT effects and test 
systems represent a scientifically reasonable focus for the Agency's 
EDSP.
    3. Evaluate endocrine disrupting properties of chemical substances 
and common mixtures. The universe of chemicals and mixtures to be 
prioritized for endocrine-disruptor screening and testing numbers more 
than 87,000 and includes commercial chemicals, active pesticide 
ingredients, ingredients in cosmetics, nutritional supplements, and 
food additives. Commercial chemicals are being included because 
chemicals like PCBs and other non-pesticidal chemicals have been 
implicated as endocrine disruptors. Nutritional supplements are known 
to contain certain naturally occuring phytoestrogens. In addition, EPA 
plans to screen representative examples of six different types of 
mixtures (i.e., combinations of two or more chemicals). The inclusion 
of the representative mixtures was viewed to be a pragmatic, achievable 
first look at a highly complex problem. Testing mixtures will determine 
whether mixtures cause different endocrine effects from those of the 
individual component chemicals. While pharmaceuticals will not be 
tested per se since they are already tested and highly regulated for 
human or animal use, they may be tested as pollutants if found to be 
present in the environment.

B. Program Elements

    EPA will use a tiered approach for determining whether a substance 
may have an effect in humans that is similar to an effect produced by 
naturally occurring EAT. The core elements of the tiered approach 
include: Sorting, priority setting, Tier 1 screening, and Tier 2 
testing. The purpose of Tier 1 is to identify substances that have the 
potential to interact with the endocrine system. The purpose of Tier 2 
is to determine whether the substance causes adverse effects, identify 
the adverse effects caused by the substance, and establish a 
quantitative relationship between the dose and the adverse effect. At 
this stage of the science, only after completion of Tier 2 tests will 
EPA be able to determine whether a particular substance may have an 
effect in humans that is similar to an effect produced by a naturally 
occurring EAT, that is, that the substance is an endocrine disruptor. 
Therefore, both Tier 1 and Tier 2 are essential elements of the 
screening program mandated by the FQPA. Moreover, this tiered approach 
is the most effective strategy for using available resources to detect 
endocrine-disrupting chemicals and quantify their effects. The core 
elements of the program are introduced in this overview section and 
presented in greater detail in subsequent sections.
    Some of the major implementation steps and estimated completion 
dates are:

 
------------------------------------------------------------------------
           Implementation steps              Estimated completion dates
------------------------------------------------------------------------
EDSTAC Final Report and Recommendations     Completed
Development of EPA's EDSP                   Completed
Public comment on EPA's EDSP                February 22, 1999
SAB/SAP Peer Review Processes               April 1, 1999
HTPS Demonstration                          February 1999
HTPS                                        June 2000
EDPSD                                       June 2000
Priority Setting for Tier 1 Phase 1         November 2000
Tier 1 Standardization and Validation       2001
 September
Tier 1, Phase 1 TSCA Test Rule Notice of    December 2001
 Proposed Rulemaking (NPRM) and FQPA
 Orders
Tier 1, Phase 1 TSCA Final Test Rule        June 2003
------------------------------------------------------------------------

IV. Sorting and Priority Setting

A. The Universe of Chemicals Included in the EDSP

    As stated earlier, EPA is concerned about the endocrine disrupting 
potential of more than 87,000 chemical substances, including pesticide 
chemicals, commercial chemicals, ingredients in cosmetics, food 
additives, nutritional supplements, and certain mixtures. Testing of 
all of these chemicals cannot be supported at the same time because, 
even if EPA and industry had the resources to do so, there are not 
enough laboratories or other facilities capable of conducting the 
testing. Consequently, EPA has included a priority-setting phase as 
part of its EDSP. During the priority-setting phase, EPA will use 
existing information, and in some cases, preliminary test results, to 
prioritize chemicals for testing. While EPA believes that the FFDCA and 
SDWA provide authority to require the testing of many of these 
substances, EPA also will use other testing authorities under FIFRA and 
TSCA to require the testing of those chemical substances that the FFDCA 
and SDWA do not cover. EPA also plans to work with other Federal 
agencies and departments to ensure that these substances also are 
tested. EPA will use appropriate authority to obtain testing of the 
chemical.

B. Sorting

    Chemicals under consideration for EAT screening will undergo 
sorting based on existing, scientifically relevant information. The 
sort would identify chemicals for HTPS as well as place chemicals into 
categories 1-4.
    1. Category 1--Hold--Chemicals with sufficient, scientifically 
relevant information to determine that they are not likely to interact 
with the EAT. If

[[Page 71546]]

EPA is able to determine, based on scientifically relevant information, 
that a specific chemical is not likely to interact with the EAT, it 
will place that chemical in a hold category. Chemicals in this hold 
category will have the lowest priority for further analysis and may not 
undergo further analysis unless new and compelling information suggests 
that the chemical may interact with the endocrine system. Although EPA 
will place chemicals in the hold category during the initial sorting 
phase of the screening program, it may add chemicals to this category 
if, during a later phase of the EDSP (Tier 1 screening, or Tier 2 
testing), the Agency determines that a particular chemical is not 
likely to interact with the endocrine system.
    Currently, EPA believes it is appropriate to assign two groups of 
chemicals to the hold category:
    i. Polymers.
    ii. Exempted chemicals.
    These substances would not be subject to HTPS or to priority 
setting for screening at this time (See Fig. 1).
[GRAPHIC] [TIFF OMITTED] TN28DE98.002


[[Page 71547]]


    i. Polymers. EPA anticipates placing most polymers with a number 
average molecular weight (NAMW) greater than 1,000 daltons in the hold 
category. These polymers are not likely to cross biological membranes 
and therefore are not likely to be biologically available to cause 
endocrine-mediated effects. EPA will not place polymers that are 
pesticide chemicals, and therefore must be tested under the FFDCA, in 
this category. In addition, EPA will not place monomer and oligomer 
components of polymers in this hold category. Instead, it will 
prioritize them for Tier 1 screening or Tier 2 testing.
    ii. Exempted chemicals. Exempted chemicals are pesticides given an 
exemption under FFDCA 408(p) and other chemicals that the Agency 
determines to exempt from the requirements of screening. These 
substances would not be included in the HTPS and would be placed in the 
hold category (see Unit. VI.L. of this notice).
    2. Category 2--Priority Setting/Tier 1 Screening--Chemicals for 
which there is insufficient, scientifically relevant information to 
determine whether or not they are likely to interact with the EAT. If 
EPA is not able to determine, based on scientifically relevant 
information, whether or not a chemical is likely to interact with the 
EAT, it will place that chemical into a category of chemicals needing 
Tier 1 screening. Category 2 chemicals are those for which there is 
insufficient scientifically relevant information to be placed on hold 
(Category 1), or assigned to Tier 2 testing (Category 3) or hazard 
assessment (Category 4). Category 2 chemicals will be subjected to 
formal priority setting, and Tier 1 screening, and as appropriate (i.e. 
positive results in Tier 1 screening), Tier 2 testing.
    3. Category 3--Tier 2 Testing--Chemicals with sufficient, 
scientifically relevant information comparable to that provided by the 
Tier 1 screening. Recognizing the need for flexibility, EPA has 
included the possibility of bypassing Tier 1 screening. For example, if 
sufficient, scientifically relevant information already exists 
regarding a specific chemical, EPA may move that chemical directly into 
Tier 2 testing. In addition, EPA may allow a chemical to bypass Tier 1 
if the chemical's producer or registrant chooses to conduct Tier 2 
testing without performing Tier 1 screening.
    4. Category 4--Hazard Assessment--Chemicals with sufficient, 
scientifically relevant information to bypass Tier 1 screening and Tier 
2 testing. For certain chemicals, there already may be sufficient, 
scientifically relevant information regarding their interaction with 
EAT--information comparable to that derived from Tier 1 screening and 
Tier 2 testing--to move them directly into hazard assessment. These 
chemicals, thus, will bypass both Tier 1 screening and Tier 2 testing. 
EPA anticipates that this will be a relatively small number of 
chemicals.

C. Information Required for Sorting and Priority Setting

    Relevant scientific information is essential to sort and prioritize 
chemicals for endocrine-disruptor testing. EPA plans to use three main 
categories of information to set priorities: Exposure-related 
information, effects-related information, and statutory criteria. EPA 
is in the process of developing a relational data base to manage the 
information that it will use to set priorities. A relational data base 
is one that can link with other data bases thus allowing EPA to access 
and manipulate data from other existing data bases.
    1. Exposure-related information and criteria. EPA proposes to use 
several types of existing exposure-related information and criteria for 
initial sorting and priority setting. These include at least four 
exposure information categories and one fate and transport information 
category. The four exposure-related information categories are: 
Biological sampling data for humans and other biota; environmental 
monitoring data, and information on occupational , consumer product, 
and food-related exposures; data on environmental releases; and data on 
production volume and use. Note that the data categories are listed 
from most robust (actual presence in biological tissue confirming that 
exposure has occurred) to least robust (amounts produced which may or 
may not result in exposure).
    This unit describes the nature of the information included in each 
exposure-related information category, the strengths and limitations of 
the type of information in each category, and a set of guiding 
principles that EPA will generally apply to complete the task of 
setting priorities for endocrine-disruptor screening and testing.
    i. Biological sampling data. Biological sampling refers to the 
monitoring of tissues from live or dead organisms for chemicals to 
document actual human or animal exposure. Biological sampling 
information falls into two subcategories: Human biomonitoring and 
monitoring of other biota. Human biomonitoring includes human tissues 
and media (e.g., blood, breast milk, adipose tissue, and urine). 
Monitoring of other biota encompasses a wide range of species 
(invertebrates, vertebrates such as fish and other wildlife) and sample 
matrices (e.g., carcass, liver, kidney, egg, feathers, etc.) for 
exposure to environmental contaminants. EPA will be guided by the 
following principles when using biological sampling data for sorting 
and priority setting.
    a. Greater weight is generally given to data sets that provide 
relevant information on large populations, disproportionately exposed 
subpopulations, or particularly susceptible subpopulations.
    b. Greater weight is generally given to non-detect data when it is 
associated with low analytical detection limits for organisms that are 
likely to be exposed.
    ii. Environmental, occupational, consumer product, and food-related 
data. Environmental, occupational, consumer product, and food-related 
data include: Monitoring data for chemical contaminants found in a 
variety of environmental media to which humans and animals are exposed, 
such as water (surface, ground, and drinking), air, soil, sediment, and 
food; and use information for chemicals, when it is available. EPA will 
be guided by the following principles when using environmental, 
occupational, consumer product, and food-related data for initial 
sorting and priority.
    a. Greater weight is generally given to validly measured data than 
to estimates.
    b. Greater weight is generally given to data that demonstrate that 
a chemical is more likely to be internalized by an organism from its 
environment.
    c. Greater weight is generally given to data sets that provide 
relevant information on large populations, disproportionately exposed 
subpopulations, or particularly susceptible subpopulations.
    d. Greater weight is generally given to non-detect data when it is 
associated with low analytical detection limits for organisms that are 
likely to be exposed.
    In the absence of monitoring data, estimates from the National 
Occupational Environment Survey, Permissible Exposure Limits (PELs) and 
similar estimates will be used to infer potential exposure levels. 
These estimates are much less robust than monitoring data but will be 
used unless actual monitoring data are submitted.
    iii. Environmental releases. Environmental release information 
includes data on chemicals released to the environment to which humans 
and environmental species may be exposed, such as permitted industrial 
discharges to air or water and accidental release or spill data. EPA 
may use data from its Toxic Release Inventory (TRI) and the Agency for 
Toxic Substances Disease Registry's (ATSDR's) Hazardous

[[Page 71548]]

Substance Emergency Surveillance System. EPA will be guided by the 
following principles when using environmental release data for sorting 
and priority setting.
    a. Greater weight is generally given to validly measured data than 
to estimates.
    b. Greater weight is generally given to data demonstrating that an 
environmental release will more likely lead to organism exposure. 
(e.g., EPA will give greater weight to TRI releases to air and water 
than TRI releases to permitted landfills, etc.).
    c. Greater weight is generally given during priority setting to 
data sets that provide relevant information on large populations, 
disproportionately exposed subpopulations, or particularly susceptible 
subpopulations.
    iv. Production volume data. Production volume data are generally 
available for existing chemicals, but not for polymers, inorganics, or 
chemicals under 10,000 pounds of annual production. (These latter 
substances have been exempted from EPA's quadrennial TSCA Inventory 
Update Rule (40 CFR part 710, subpart B)). For new chemicals, the only 
production volume information available is estimates and it is not 
relevant for environmental contaminants. EPA will be guided by the 
following principles when using production volume data for sorting and 
priority setting.
    a. Production volume provides only a very rough indication of 
potential human and environmental exposure.
    b. Production data generally should be combined with other data 
(e.g., use and physical properties data) in an effort to minimize some 
of the inherent weaknesses of using production data as a surrogate for 
exposure.
    c. Production information generally should not be used to compare 
existing industrial chemicals, pesticides and new chemicals because 
production volume ranges are too divergent. For example, production 
volumes for high-volume industrial chemicals are several orders of 
magnitude higher than those for either new chemicals or pesticides.
    v. Fate and transport data and models. The fate and transport 
information category includes chemical and/or physical properties that 
may be used to predict or estimate the medium or media where a chemical 
is likely to be found and whether or not a chemical is likely to remain 
in the environment over time.
    Environmental fate and transport information is available from 
various reference sources, including data bases, textbooks, and 
monographs. Numerous sources of data and models are listed in Appendix 
G of the EDSTAC Final Report (EDSTAC, 1998). The sheer volume of 
environmental fate and transport data makes it necessary to identify 
those data useful for sorting and prioritization purposes. EPA will 
focus attention on three subcategories of environmental fate and 
transport information including: Persistence, mobility, and 
bioaccumulation.
    EPA will consider the following characteristics of fate and 
transport data: Hydrolysis half-life persistence; biodegradation 
persistence; photooxidation persistence; volatility (Henry's Law) 
mobility; adsorption coefficient (Koc ) mobility; and 
octanol: water partition coefficient (Kow/LogP) mobility and 
bioaccumulation. EPA may use a multimedia fate and partitioning model 
to combine this information in a meaningful manner. EPA will be guided 
by the following principles when using fate and transport data and 
models for initial sorting and priority.
    a. Air, water, and soil environmental compartments generally should 
be considered when using fate and transport data to help set priorities 
for screening.
    b. Greater weight generally should be given to fate and transport 
characteristics based on laboratory or field tests than on estimates.
    2. Effects-related information and criteria. EPA generally plans to 
rely on HTPS data, toxicological laboratory studies, epidemiological 
studies, and predictive structure activity models to assist the Agency 
in setting priorities for screening.
    i. Toxicological and epidemiological studies. Toxicological 
laboratory studies include information related to the laboratory study 
of toxic effects of commercial chemicals, pesticides, contaminants, or 
mixtures on living organisms or cell systems including humans, 
wildlife, or laboratory animals. Epidemiological and field studies 
range from hypothesis-generating descriptive studies, such as case 
reports and ecological field analyses, to prospective cohort studies 
and rigorously controlled hypothesis-testing clinical trials.
    Empirical toxicological and epidemiological data are reported in 
numerous peer-reviewed scientific journals. Published studies are 
conducted and described in varying degrees of methodological rigor and 
data are reported in widely varying detail. To rely on this 
information, EPA would be required to review it and determine its 
applicability and adherence to generally acceptable investigatory 
practices. The search and review of this primary literature would be 
too resource intensive to be part of the prioritization process. 
Instead EPA will rely on data bases containing studies addressing the 
endpoints of interest. In response to EPA's proposed Priority List, 
public commenters can submit studies that EPA will review. If the 
submitted studies indicate that the priority should be changed or they 
meet the requirements of portions of Tier 1, EPA will change the 
priority or screening requirements for that chemical, as appropriate.
    EPA will be guided by the following principles when evaluating 
toxicological and epidemiological data:
    a. Negative epidemiological studies generally will not override 
positive toxicological studies. Positive epidemiological studies 
generally will override negative toxicological studies for priority-
setting purposes.
    b. EPA generally will give greater weight to in vivo studies with 
relevant endpoints than to in vitro studies.
    ii. Predictive structure-activity models. Predictive biological 
activity or effects models attempt to identify the correlation between 
chemical structure and biological activity, including those that can be 
identified through in vitro and in vivo screens. Models can be useful 
when biological data are unavailable. While EPA believes this approach 
will be of limited success early in the screening program, it believes 
that the refinement of models as more screening results become 
available may increase their utility as a predictive tool for priority 
setting and may actually replace some of the more mechanistic Tier 1 
assays.
    3. Statutory criteria. The FFDCA, as amended, requires that EPA 
provide for the testing of all ``pesticide chemicals.'' Under the 
FFDCA, ``pesticide chemical'' includes ``any substance that is a 
pesticide within the meaning of FIFRA, including all active and inert 
ingredients'' (21 U.S.C. 321(q)(1)). It also includes impurities. The 
statute does not restrict testing to pesticides used on foods. As part 
of priority setting, EPA will ensure that all substances that must be 
tested pursuant to the FFDCA--i.e., pesticide chemicals--are tested in 
a timely manner.

D. Use of a HTPS to Assist Priority Setting

    For the majority of chemicals, EPA does not believe that any 
endocrine-disruptor effects data exists. This lack of data makes it 
difficult to set priorities for screening and testing. To help solve 
this problem, EPA plans to conduct two of the Tier 1 screening tests 
(see Units V.A. and VI.B. and C. of this notice) on approximately 
15,000 chemicals in a high-speed, automated fashion. Since these assays 
are being run before the

[[Page 71549]]

Tier 1 screening is conducted, EPA refers to this testing as HTPS. HTPS 
test results will provide information on the interaction of chemicals 
with the estrogen and androgen receptor. The automated, low-cost nature 
of HTPS allows EPA to test a large number of chemicals in a short 
period of time. HTPS will provide EPA with preliminary information 
relating to one of several possible mechanisms by which a chemical may 
affect the endocrine system. Thus, EPA will use HTPS to assist in 
setting priorities for further screening; the Agency will not use HTPS 
alone to decide whether a chemical should or should not move to the 
next phase in the EDSP.

E. Setting Priorities for Tier 1 Screening

    EPA plans to use existing, available information, HTPS data, and 
the EDPSD to establish Tier 1 screening priorities. EPA anticipates, 
however, that the quantity and quality of exposure and effects 
information will be uneven for the majority of chemicals. Thus, to 
ensure the integrity of the priority-setting process and avoid an 
``apples'' to ``oranges'' comparison, EPA plans to adopt a 
``compartment-based approach'' to priority setting. The term 
``compartment'' refers to the particular information category or 
criterion or combinations of information or criteria that defines a set 
of chemicals, just as a group of parameters defines a set of numbers in 
mathematics. All members of the set must possess the properties 
required for membership in the compartment and thus will have these 
elements in common as the basis for comparison. Operationally, EPA will 
establish a limited number of compartments and sort chemicals into 
those compartments based on the criteria defining each compartment. EPA 
will then prioritize chemicals within each of the compartments 
according to criteria related to those for membership in the 
compartment. Finally, EPA will recombine the highest priority chemicals 
in each compartment to form the group of chemicals going into phase 1 
of the screening program.
    EPA has not identified all of the specific compartments. Examples 
of compartments, however, may include HPVCs, chemicals in consumer 
products, chemicals found in biological tissue, pesticide-active 
ingredients, formulation ingredients in pesticides, and chemicals found 
in sources of drinking water. A chemical could fall into more than one 
compartment. To help develop the list of priority-setting compartments, 
EPA plans to convene a priority-setting workshop for multi-
stakeholders. The document announcing the priority-setting workshop is 
published elsewhere in this issue of the Federal Register.
    Pesticides present a special difficulty in priority setting because 
data on both inert formulation ingredients and active ingredients need 
to be available at the time of a pesticide's evaluation. This will 
present some logistical difficulties in prioritizing the screening of 
pesticide formulations since pesticides with the same active ingredient 
may contain significantly different formulation inert ingredients.
    Although EPA has not identified all priority-setting compartments, 
it has decided on some compartments. EPA plans to have a ``mixtures'' 
compartment, a ``naturally occurring non-steroidal estrogen'' 
compartment; and a ``nominations'' compartment. Each of these 
compartments is described in detail in this unit.
    1. Nominations. The priority-setting process generally will give 
high priority to chemicals with widespread exposure at the national 
level. However, there are chemicals that result in disproportionately 
high exposure to identifiable groups, communities, or ecosystems. For 
these, EPA plans to establish process by which affected citizens can 
nominate chemicals with regional or local exposure to receive priority 
for Tier 1 screening (see Unit VI.E. of this notice).
    2. Mixtures. Mixtures, defined as a combination of two or more 
chemicals, will need special attention during the initial stages of 
sorting and prioritization because they present unique challenges for 
testing and hazard assessment. Consequently, EDSTAC recommended that 
EPA determine the technical feasibility and, where feasible, screen and 
test representative samples of mixtures from six distinct types of 
mixtures, including: Contaminants in human breast milk; phytoestrogens 
in soy-based infant formula; mixtures of chemicals commonly found at 
hazardous waste sites; pesticide/fertilizers mixtures; disinfection 
byproducts; and gasoline.
    EPA will investigate the technical feasibility for screening and 
testing mixtures as recommended by EDSTAC. This will include an 
evaluation of whether it is possible to identify a reasonable number of 
representative samples of mixtures from each of the recommended six 
types of mixtures, as well as the ability to send the representative 
samples of mixtures through HTPS, Tier 1 screening, and Tier 2 testing 
depending on their physical properties, and validation and 
standardization of the results.
    3. Naturally occurring non-steroidal estrogens (NONEs). Another 
special class of chemicals of interest to EPA are naturally occurring 
NONEs. These are natural products derived from plants (phytoestrogens) 
and fungi (mycotoxins). These chemicals occur widely in foods and have 
the potential to act in an additive, synergistic, or antagonist fashion 
with other hormonally active chemicals. EPA will work with the Food and 
Drug Administration (FDA) and the National Toxicology Program to obtain 
testing of the seven specific NONEs that were identified by EDSTAC.

F. Bypassing Tier 1 Screening

    Recognizing the need for flexibility in applying the screening and 
testing requirements, EPA plans to permit chemicals to bypass Tier 1 
screening under certain circumstances. If sufficient, scientifically 
relevant information exists regarding a specific chemical, EPA may move 
that chemical directly into Tier 2 testing. In addition, EPA may allow 
a chemical to bypass Tier 1 screening if the chemical's producer or 
registrant chooses to conduct Tier 2 testing without performing Tier 1 
screening. Each of these two scenarios has different implications for 
the information requirements associated with completing Tier 2 testing.
    1. Chemicals that have previously been subjected to 2-generation 
reproductive toxicity tests. This scenario includes chemicals that have 
previously been subjected to mammalian and wildlife developmental 
toxicology and/or reproductive testing, but where the tests did not 
include endocrine sensitive endpoints included in the most recent 
Office of Prevention, Pesticides, and Toxic Substances (OPPTS) or 
Organization for Economic Cooperation and Development (OECD) test 
guidelines (See Tables 2, 3, and 4 in Unit V.B. of this notice). Food-
use pesticides fall into this category, as do a small number of certain 
other pesticides and industrial chemicals. Chemicals and non-food-use 
pesticides that meet this criterion also will likely be candidates for 
alternative approaches to Tier 2 testing.
    Chemicals that have data from tests that meet the requirements of 
the new mammalian guidelines, but not the new wildlife tests, would be 
subjected to the wildlife testing requirements unless scientifically 
sound reasons are provided to limit testing.
    2. Chemicals for which there is limited prior toxicology testing. 
The second bypass scenario includes chemicals whose manufacturer or

[[Page 71550]]

registrant has decided to voluntarily complete Tier 2 testing without 
having completed the full Tier 1 screening battery or any prior 2-
generation reproductive toxicity testing. Chemicals that bypass Tier 1 
screening under this scenario must be evaluated using the entire Tier 2 
battery (i.e., the mammalian and non-mammalian multi-generation tests 
with all the recommended test species and endpoints) unless 
scientifically sound reasons are provided to limit testing.
    EPA will generally follow the guidance set forth in this unit when 
setting Tier 2 testing priorities for chemicals that bypass Tier 1 
screening:
    i. If a chemical is deemed to be high priority for Tier 1 screening 
and the manufacturer or registrant of the chemical decides to 
voluntarily bypass Tier 1, it should also be high priority for Tier 2 
testing. Voluntary action on the part of registrants/manufacturers 
should expedite testing.
    ii. To the extent practicable, pesticides should be tested on the 
schedule EPA has established for tolerance reassessments, pesticide re-
registration and registration renewal under the FFDCA and FIFRA, unless 
HTPS or other data indicate that the pesticide should be tested in a 
shorter timeframe. EPA does not intend to delay tolerance 
reassessments, re-registration or registration renewal actions to await 
implementation the EDSP.

G. Mixtures

    For purposes of the EDSP, EPA defines ``mixture'' as a combination 
of two or more chemicals. EPA will consider most commercial chemicals 
(class 1 and class 2 substances under TSCA) to be chemicals even though 
they may contain other substances in them as impurities or exist as 
complex reaction products. In some cases a commercial product is in 
reality a complex mixture of unidentified composition in which no 
single substance predominates. These complex products have Chemical 
Abstract Service (CAS) numbers and will be regarded as chemicals from a 
legal and policy perspective but may need to be treated as mixtures 
from a scientific perspective in the EDSP. This determination will be 
made case by case.
    EPA recognizes that the science of evaluating mixtures remains 
complex and unclear, but believes that it should begin to confront the 
issues raised by them. EPA will sponsor some screening of mixtures 
after the demonstration of the HTPS and validation of the Tier 1 
screening battery on single chemicals.
    Initially, EPA plans to include a few mixtures in the HTPS. EDSTAC 
has recommended that one or more representative samples from each of 
the following high priority mixtures would be tested:
    1. Contaminants in human breast milk.
    2. Phytoestrogens in infant soy formula.
    3. Mixtures of chemicals found at hazardous waste sites.
    4. Pesticide and fertilizer mixtures.
    5. Disinfection byproducts.
    6. Gasoline.
    EPA also plans to evaluate some mixtures in the Tier 1 screen. If 
results of Tier 1 are positive for a mixture, the Agency will face a 
choice of testing the mixture in Tier 2 or determining what substances, 
or combination of substances, are responsible for the activity. The 
Agency likely will choose this latter course of action and test the 
individual active chemical or active fraction in Tier 2.

H. Categories of Chemicals

    In its first TSCA proposed test rule (45 FR 48524, July 18, 1980), 
EPA outlined three approaches for testing chemicals belonging to a 
chemical category:
    1. Test members of a category as individual chemicals.
    2. Select test substances to represent the structural and chemical 
variation of the category as a whole.
    3. Subdivide the category into subgroups and choose a 
representative from each as a surrogate for the entire subgroup.
    For the HTPS, EPA plans to screen all members of a category that 
are produced in quantities over 10,000 pounds. The Agency will make a 
case-by-case decision regarding whether all of these chemicals will be 
required to go through Tier 1. However, it is likely that the HPVCs 
would be screened in Tier 1 regardless of the strategy used. As 
Quantitative Structure Activity Relationship (QSAR) modeling becomes 
more reliable, the two sampling approaches (approaches 2 and 3 as 
described in this unit) may become more viable alternatives.

V. Screening Program

    EPA recognizes that a huge number of chemicals could be evaluated 
under the EDSP. EPA is adopting EDSTAC's recommendation of a two-tiered 
system to make the evaluation process more efficient. In Tier 1, a 
screening battery of assays will identify those chemical substances and 
mixtures capable of interacting with EAT. Tier 1 covers only screening 
tests and these alone are not sufficient to determine whether a 
chemical substance may have an effect in humans that is similar to an 
effect produced by naturally occurring hormones. The purpose of Tier 2 
tests is to determine whether a chemical substance or mixture may cause 
endocrine-mediated effects for EAT, determine the consequences to the 
organism of the activities observed in Tier 1, and establish the 
relationship between the doses of the endocrine-active substance 
administered in the test and the effects observed.

A. Tier 1 Screening

    Chemical substances or mixtures can alter endocrine function by 
affecting the availability of a hormone to the target tissue, and/or 
affecting the cellular response to the hormone. Mechanisms regulating 
hormone availability to a responsive cell are complex and include 
hormone synthesis, serum binding, metabolism, cellular uptake (e.g., 
thyroid), and neuroendocrine control of the overall function of an 
endocrine axis. Mechanisms regulating cellular response to hormones are 
likewise complex and are tissue specific. Because the role of receptors 
is often crucial to cellular responsiveness, specific nuclear receptor 
binding assays are included. In addition, tissue responses that are 
particularly sensitive and specific to a hormone are included as 
endpoints for Tier 1 screens. In order for the Tier 1 screening battery 
to discriminate between substances likely to affect the endocrine 
system and those not likely to affect it, the screening battery should 
meet the following criteria:
    1. Detect all known modes of action for the endocrine endpoints of 
concern. All chemicals known to affect the action of EAT should be 
detected.
    2. Maximize sensitivity to minimize false negatives while 
permitting a level of as yet undetermined, but acceptable, false 
positives. The screening battery should not miss potential EAT active 
materials.
    3. Include a sufficient range of taxonomic groups among the test 
organisms. There are known differences in endogenous ligands, 
receptors, and response elements among taxa that may affect endocrine 
activity of chemical substances or mixtures. The screening battery 
should include assays from representative vertebrate classes to reduce 
the likelihood that important pathways for metabolic activation or 
detoxification of parent chemical substances or mixtures are not 
overlooked.
    4. Incorporate sufficient diversity among the endpoints and assays 
to reach conclusions based on ``weight-of-evidence'' considerations. 
Decisions based on the screening battery results

[[Page 71551]]

will require weighing the data from several assays.
    EPA's Tier 1 screening battery meets these criteria. The proposed 
Tier 1 screening battery and alternative assays for possible inclusion 
are:

Proposed Tier 1 Screening Battery

In Vitro

    1. Estrogen Receptor (ER) Binding/Transcriptional Activation Assay.
    2. Androgen Receptor (AR) Binding/Transcriptional Activation 
Assay. 1
---------------------------------------------------------------------------

    1The ER and AR transcription activitation assays are in the 
HTPS. Those chemicals which go through the HTPS program, if it is 
technically feasible and validated, would not be required to 
separately undergo the first two in vitro assays at the bench.
---------------------------------------------------------------------------

    3. Steroidogenesis Assay with Minced Testis.

 In Vivo

    1. Rodent 3-Day Uterotrophic Assay (Subcutaneous (sc)).
    2. Rodent 20-Day Pubertal Female Assay with Thyroid.
    3. Rodent 5-7-Day Hershberger Assay.
    4. Frog Metamorphosis Assay.
    5. Fish Gonadal Recrudescence Assay.

 Alternative Assays for Possible Inclusion in Tier 1

 In Vitro

    1. Placental Aromatase Assay.

In Vivo

    1. Modified Rodent 3-Day Uterotrophic Assay (Intraperitoneal).
    2. Rodent 14-Day Intact Adult Male Assay With Thyroid.
    3. Rodent 20-Day Thyroid/Pubertal Male Assay.
    EPA plans to include the alternative assays in the standardization 
and validation program. Combinations of the alternative assays, if 
validated and found to be functionally equivalent, could potentially 
replace three of the component assays in the recommended Tier 1 
screening battery (in vitro steroidogenesis assay with testis, 20-day 
pubertal female assay, and 5-7-day Hershberger assay), thereby possibly 
reducing the overall time, cost, and complexity while maintaining 
equivalent performance of the overall Tier 1 screening battery.
    1. In vitro assays. EPA has identified two categories of in vitro 
assays that may be used in Tier 1 screening to assess the binding of 
test substances to receptors, i.e., cell-free assays for receptor 
binding and transfected cells designed to detect transcriptional 
activation. The specific assays chosen, whether done ``at the bench'' 
or as a HTPS should have the following characteristics:
    a. Evaluate binding to estrogen and androgen nuclear receptors.
    b. Evaluate binding to the receptor in the presence and absence of 
metabolic capability (e.g., one or more of the P450 isozymes, e.g., 
cyp1A1, cyp3A4).
    c. Distinguish between agonists and antagonists in functional 
assays.
    d. Yield dose responses for relative potency of chemical substances 
or mixtures exhibiting endocrine activity.
    In vitro evaluations can provide both false positive and false 
negative results.  In vitro false positives (i.e., active in vitro but 
not in vivo) arise when a chemical is not absorbed or distributed to 
the target tissue, is rapidly metabolically inactivated and/or 
excreted, and/or when some other form of toxicity predominates in vivo. 
False negatives are considered to be of greater concern if in vitro 
tests were used to the exclusion of in vivo methods. In vitro 
evaluations can result in false negatives due to their inability, or 
diminished capacity, to metabolically activate toxicants. As a result, 
EPA's proposed screening battery includes in vivo methods in 
conjunction with in vitro techniques. Nevertheless, some in vitro 
assays may offer distinct advantages over in vivo assays when 
investigating the activity of specific metabolites.
    The estrogen and androgen receptor binding assays provide an 
indication of the potential of a substance to disrupt ER or AR function 
in vivo. In the receptor binding assays the test chemical competes for 
binding at the receptor with the natural ligand or other strongly 
binding substance. EPA strongly prefers stably transfected 
transcriptional-activation assays over receptor binding assays. In 
addition to binding, there is a consequence to the binding with the 
transcriptional-activation assay, i.e., transcription (synthesis of 
messenger Ribonucleic Acid (mRNA)) of a reporter gene and translation 
of the mRNA to an identifiable detectable protein such as firefly 
luciferase or beta-galactosidase. This assay can distinguish between 
agonists and antagonists and can be run with and without metabolic 
activation.
    The third in vitro assay in the screening battery is the 
steroidogenesis assay. This assay utilizes minced testes and detects 
the ability of substances to interfere with the endocrine system by 
inhibiting the activity of P450 enzymes in the steroid pathway. 
Inhibition of mammalian-steroid synthesis can potentially result in a 
broad spectrum of adverse effects in vivo, including abnormal serum 
hormone levels, pregnancy loss, delayed parturition, demasculinization 
of male offspring, lack of normal male and female mating behavior, 
altered estrous or menstrual cyclicity, and altered reproductive organ 
sizes and weights. Interference with other enzymes involved in the 
synthesis of specific hormones will be detected in the in vivo assays.
    2. In vivo assays. The value of each individual assay cannot be 
considered in isolation from the other assays in the screening battery, 
as they have been combined in a manner such that limitations of one 
assay are complemented by strengths of another. In vivo assays 
complement in vitro assays in several important ways. In vivo methods 
in Tier 1 can help reduce false negatives related to absorption, 
distribution, metabolism, and excretion of a chemical substance in the 
absence of knowledge of its pharmacokinetics. In vivo assays typically 
cover a broader range of mechanisms of action than in vitro assays. It 
would be impractical to try to include an in vitro assay for every 
mechanism of action and in some cases it would be impossible as the 
mechanism would be expressed only in whole animal systems. It is clear 
that a combination of in vivo and in vitro assays is necessary in order 
to detect EAT alterations that act via the ER, AR, thyroid receptor 
(TR), inhibition of steroid hormone synthesis, and/or alterations of 
the hypothalamic-pituitary-gonadal (HPG) and hypothalamic-pituitary-
thyroid (HPT) axes. The screening battery, once validated, should 
detect all chemicals with the potential to disrupt the EAT systems, 
including xeno(anti)estrogens (that act via the ER or inhibition of 
aromatase by oral or parenteral administration), xeno(anti)androgens 
(via AR or hormone synthesis), altered HPG axis, and antithyroid action 
(via synthesis, metabolism and transport, and the TR). However, results 
of even the most specific in vivo assays can be affected by endocrine 
mechanisms other than those directly related to ER, AR, and TR action. 
The lack of specificity of in vivo assays is a limitation if the goal 
is to only identify ER, AR, and TR alterations. In contrast, this lack 
of specificity could be considered an advantage if a broader, more 
apical screening strategy is desired.
    i. Uterotrophic assay. An increase in uterine weight is generally 
considered to be one of the best indicators of estrogenicity when 
measured in the ovariectomized (ovx) or immature female rat or mouse 
after 1-3 days of treatment. EPA is planning to require as part of the 
program a 3-day uterotrophic assay using the ovx adult female rat (the 
duration can be extended if so desired) with 10 animals per group. EPA 
will require sc treatment because most of the

[[Page 71552]]

historical data are collected in this manner and there are relatively 
few data concerning the effects of other routes of administration at 
this time. EPA is also planning to use this assay to detect 
antiestrogens. When run to detect antiestrogens, a control and 
xenobiotic-treated group are co-administered with estradiol. The 
uterotrophic assay is an in vivo check on the ER binding and ER 
reporter gene assays.
    ii. 20-Day pubertal female with thyroid. The 20-day pubertal female 
assay is the most comprehensive assay in the screening battery. It can 
detect thyroid effects, aromatase inhibitors, estrogens, antiestrogens, 
and agents which interfere with one of the hormone feedback loops that 
controls maturation and reproduction, the HPG axis. Next to in utero 
development, the pubertal stage is the most sensitive and vulnerable 
life stage.
    Exposure of weanling female rats to environmental estrogens can 
result in alterations of pubertal development (Ramirez and Sawyer 
1964). Exposure to a weakly estrogenic pesticide after weaning and 
through puberty induces pseudoprecocious puberty (accelerated vaginal 
opening without an effect on the onset of estrous cyclicity) after only 
a few days of exposure (Gray et al. 1989). Pubertal alterations are 
also observed in girls exposed to estrogen-containing creams or drugs, 
which induce pseudoprecocious puberty and alterations of bone 
development (Hannon et al. 1987).
    In the pubertal female assay, oral dosing is initiated in weanling 
rats at 21 days of age (10 per group, selected for uniform body weights 
at weaning to reduce variance). The animals are dosed daily, 7 days a 
week, and examined daily for vaginal opening (one could also check for 
age at first estrus and onset of estrous cyclicity). Dosing continues 
until vaginal opening is attained in all females (typically 2 weeks 
after weaning, unless delayed). The advantage over the uterotrophic 
assay is that one test detects both agonists and antagonists, it 
detects xenoestrogens like methoxychlor that are almost inactive via sc 
injection, it detects aromatase inhibitors, altered HPG function, and 
unusual chemicals like betasitosterol. In addition, at necropsy one 
should weigh the ovary (increased in size with aromatase inhibitors, 
but reduced with betasitosterol), save the thyroid for histopathology, 
take serum for T4, and measure thyroid-stimulating hormone (TSH). In 
addition to estrogens, the age at vaginal opening and uterine growth 
can be affected by alteration of several other endocrine mechanisms, 
including alterations of the HPG axis (Shaban and Terranova 1986; and 
Gonzalez et al. 1983). In rats, this event can also be induced by 
androgens (Salamon 1938; and EGF (Nelson et al. 1991). In the last 20 
years there have been over 200 publications which demonstrate the broad 
utility of this assay to identify altered estrogen synthesis, ER 
action, growth hormone, prolactin, follicle-stimulating hormone (FSH) 
or luteinizing hormone (LH) secretion, or central nervous system (CNS) 
lesions.
    iii. Rodent 5-7 day Hershberger assay. This assay is designed to 
detect androgenic and antiandrogenic effects. In this in vivo assay, 
sex accessory gland weights (ventral prostate and seminal vesicle 
separately) are measured in castrated, T-treated adult male rats after 
4-7 days of treatment by gavage with the test compound. The advantage 
of this assay is that it is fairly simple, short term, and relatively 
specific for direct androgenic/antiandrogenic effects compared to other 
in vivo procedures. To detect both agonists and antagonists the assay 
requires two-dosing regimes:
    a. Castrated male rat + Xenobiotic (to detect agonist)
    b. Castrated male rat + T + Xenobiotic (to detect antagonist)
    Although the androgens, T, and dihydrotestosterone (DHT), play a 
predominant role in the growth and maintenance of the size of these 
accessory gland structures, several other hormones and growth factors 
can influence sex organ weights including the thyroid and growth 
hormones, prolactin, and epidermal growth factor (EGF). Exposure to 
estrogenic pesticides can also reduce sex accessory gland size; 
however, it is unclear to what degree these reductions result from 
direct versus indirect action of the chemical. Other useful endpoints 
that help reveal the mechanism of action include serum hormone levels 
of T, DHT, LH, AR distribution, TRPM2/C3 gene activation, ornithine 
decarboxylase (ODC), and 5-alpha-reductase activity in the prostate.
    The prostate and seminal vesicles should be weighed separately 
because these organs differ with respect to the androgen that controls 
their growth and differentiation. The prostate is dependent upon 
enzymatic reduction of T to DHT, whereas the seminal vesicle is less 
dependent upon this conversion. Hence, effects on 5-alpha-reductase can 
be distinguished from AR-mediated mechanisms by determining whether the 
prostate is preferentially affected. Growth of the levator ani muscle 
is T dependent, having little capacity to convert T to the more potent 
androgen DHT. Weight of this muscle is useful in identifying anabolic 
androgens and antiandrogens, and for this reason has been used 
extensively in the pharmaceutical industry. In order to detect 
androgenic rather than antiandrogen action one would simply delete the 
hormone administration from the protocol.
    iv. Frog metamorphosis assay. This assay is in the screening 
battery to detect thyroid (increase in tail resorption rate) and 
antithyroid (decrease in tail resorption rate) effects. It also 
broadens the taxonomic representation of the screening battery. This 
assay employs intact larval (tadpole) stages of the African clawed frog 
(Xenopus laevis) exposed over a 14-day time period, 50-64 days of age, 
to observe the rate of tail resorption (Fort and Stover 1997). Tail 
resorption can be easily quantified with computer-aided video image 
processing (Fort and Stover 1997). The molecular mechanisms involved in 
tail resorption are well characterized (Brown et al. 1995; Hayes 1997a) 
and this assay is, therefore, considered to be a simple and specific 
assay for thyroid action. Because evidence also suggests that thyroid 
action on tail resorption is regulated by corticoids, estrogens, and 
prolactin (Hayes 1997b), this assay will address distinctive modulating 
pathways and, in tandem with the 20-day mammalian pubertal assay, a 
comprehensive screen for thyroid hormone activity is achieved.
    v. Fish gonadal recrudescence assay. This assay is in the Tier 1 
screening battery because as a group, fish are the most distant from 
mammals within the vertebrates, and it provides an additional safeguard 
that endocrine disruptors will not pass through the screen undetected. 
Intact mature fish maintained under simulated ``winter'' conditions 
(short-day length, cool temperatures) exhibit regressed secondary sex 
characteristics and gonad maturation.
    In this assay, intact fish of both sexes (fathead minnow, 
Pimephales promelas, or other appropriate species) are simultaneously 
subjected to an increasing photoperiod/temperature regime and test 
substance to determine potential effects on maturation from the 
regressed position (recrudescence). The primary endpoints examined in 
the assay include morphological development of secondary sexual 
characteristics, ovary and testis development (weight increases), 
gonadosomatic index (ratio of gonadal weight to body weight), final 
gamete maturation (ovulation, spermiation), and induction of 
vitellogenin. This assay is sensitive to HPG axis effects in

[[Page 71553]]

addition to androgen- and estrogen-related activity.
    Having diverse taxa in Tier 1 may give some information on the 
homology of the endocrine system across species and likelihood of 
consistent response across taxa and among organisms of the same species 
and when one must be concerned about variability.
    3. Alternative assays for possible inclusion. These assays are 
being developed and validated (see Unit VI.F. of this notice) and may 
be acceptable cost effective substitutes for some of the assays in the 
primary Tier 1 screening battery of recommended by EDSTAC.
    i. Placental aromatase assay. Aromatase converts T to estradiol. If 
an assay using a male is substituted for the 20-day pubertal female 
assay it will be necessary to add this assay to the screening battery 
since aromatase is present at very low levels in the testis. It is 
present at higher levels in the ovary, uterus, and placenta. Human 
placental aromatase is commercially available and could be used in 
vitro to assess the effects of toxicants on this enzyme.
    ii. Modified rodent 3-day uterotrophic assay (Intraperitoneal). The 
intraperitoneal (ip) injection method may enhance the sensitivity of 
the uterotrophic assay and is capable of detecting the estrogenic 
potential of methoxychlor, which has been cited as an example of a 
compound not detectable by the sc route. This is an in vivo assay 
(O'Conner et al. 1996) for estrogenic activity in ovx female rats. It 
can detect certain antiestrogens with mixed activity, i.e., some 
agonistic activity (e.g., tamoxifen).
    The rats are injected intraperitoneally with the test agent daily 
for 3 days. The females are necropsied either 6 hours or 24 hours after 
the final treatment, depending on the protocol employed by the 
laboratory. Vaginal cytology is evaluated by vaginal lavage to 
determine whether the epithelium has become cornified, indicative of 
estrus. Presence of fluid in the uterine lumen is noted and recorded, 
and the number of animals that have fluid in the uterus is reported. 
Fluid imbibition (uptake) is indicative of estrogenic potential. The 
uterus is excised and weighed. It is then preserved in an appropriate 
fixative for subsequent histological evaluation, if needed. Subsequent 
histological evaluation will be triggered by an equivocal uterine 
weight or uterine fluid response (i.e., an increase that is not 
statistically significant). This evaluation will consist of a 
characterization of the appearance of the uterine epithelium, a 
measurement of uterine epithelial cell height, and epithelial mitotic 
index or proliferating cell nuclear antigen (PCNA) 
immunohistochemistry. Uterine cell height and cell proliferation are 
sensitive indicators of estrogenic potential.
    iii. 14-Day intact adult male assay. This in vivo assay is intended 
to detect effects on male reproductive organs that are sensitive to 
antiandrogens and agents that inhibit T synthesis or inhibit 5-alpha-
reductase (Cook et al. 1997). The proponents of this assay believe that 
the duration of the assay is sufficient to detect effects on thyroid 
gland activity. The rats are anatomically intact and mature; therefore, 
they have an intact HPG axis, allowing an assessment of the higher 
order neuroendocrine control of male reproductive function and the 
thyroid. This assay coupled with the aromatase assay could potentially 
replace the Hershberger and the pubertal female assays in the 
recommended screening battery. Empirical assessment of this assay has 
shown it to be sensitive to agents that are directly antiandrogenic, 
inhibit 5-alpha-reductase, inhibit T synthesis, or affect thyroid 
function. The sensitivity of this assay, as defined as the ability to 
detect a hazard, may be comparable to other assays that have been 
recommended.
    Young adult male rats (70-90 days of age) are used in this assay. 
They are dosed daily with the test agent for 14 days. The recommended 
route of administration is ip, which may, in some cases, maximize the 
sensitivity of the assay. They are necropsied 24 hours after the final 
dose. Immediately after sacrifice, one cauda epididymis is weighed and 
processed for evaluation of sperm motility and concentration. The 
following organs are weighed: Testes, epididymides, seminal vesicles, 
and prostate. The following are fixed and evaluated histologically: One 
testis and epididymis and the thyroid. The following hormones are 
measured in blood plasma: T4, TSH, LH, T, DHT, and estradiol.
    iv. Rodent 20-day thyroid/pubertal male assay. This assay (in 
conjunction with the aromatase assay) is another candidate to replace 
the pubertal female and Hershberger assays in the screening battery. 
The thyroid/pubertal male assay detects androgens and antiandrogens in 
vivo in a single stage-apical test. ``Puberty'' is measured in male 
rats by determining age at preputial separation (PPS). Preputial 
separation and sex accessory gland weights are sensitive endpoints. 
However, a delay in PPS is not pathognomonic for antiandrogens. 
Pubertal alterations result from chemicals that disrupt hypothalamic-
pituitary function (Huhtaniemi et al. 1986), and, for this reason, 
additional in vivo and in vitro tests are needed to identify the 
mechanism of action responsible for the pubertal alterations. For 
example, alterations of prolactin, growth hormone, gonadotrophin (LH 
and FSH) secretion, or hypothalamic lesions alter the rate of pubertal 
maturation in weanling rats. Sex accessory gland weights in intact-
adult male rats also can be affected directly or indirectly by toxicant 
exposure. The HPG axis in an intact animal is able to compensate for 
the action of antiandrogens by increasing hormone production, which 
counteracts the effect of the antiandrogen on the tract (Raynoud et al. 
1984; Edgren 1994; Hershberger 1953).
    Delays in male puberty result from exposure to both estrogenic and 
antiandrogenic chemicals including methoxychlor (Gray et al. 1989), 
vinclozolin (Anderson et al. 1995b and dichlorodiphenyldichloroethylene 
(p,p' DDE) (Kelce et al. 1995). Exposing weanling male rats to the 
antiandrogenic pesticides p,p' DDE or vinclozolin delays pubertal 
development in weanling male rats as indicated by delayed PPS and 
increased body weight (because they are older and larger) at puberty. 
In contrast to the delays associated with exposure to estrogenic 
substances, antiandrogens do not inhibit food consumption or retard 
growth (Anderson et al. 1995). Antiandrogens cause a delay in PPS and 
affect a number of endocrine and morphological parameters including 
reduced seminal vesicle, ventral prostate, and epididymal weights. It 
is apparent that PPS is more sensitive than are organ weights in this 
assays. In addition, responses of the HPG are variable. In studies of 
vinclozolin, increases in serum LH were a sensitive response to this 
antiandrogen, whereas serum LH is not increased in males exposed to 
p,p' DDE during puberty (Kelce et al. 1997). Furthermore, a systematic 
review of the literature indicates that the sex accessory glands of the 
immature intact-male rat are consistently more affected than in the 
adult intact-male rat.
    Animals are dosed by gavage beginning 1 week before puberty (which 
occurs at about 40 days of age) and PPS is measured. Androgens will 
accelerate and antiandrogens and estrogens will delay PPS. The assay 
takes about 3 weeks and allows for comprehensive assessment of the 
entire endocrine system in one study. The animals (10 per group, 
selected for uniform body weights to reduce variance) are dosed daily, 
7 days a week, and examined daily for PPS. Dosing continues until 53

[[Page 71554]]

 days of age; the males are then necropsied. The body, heart (thyroid), 
adrenal, testis, seminal vesicle plus coagulating glands (with fluid), 
ventral prostate, and levator ani plus bulbocavernosus muscles (as a 
unit) are weighed. The thyroid is retained for histopathology and serum 
is taken for T4, T3, and TSH. Testosterone, LH, prolactin, and DHT 
analyses are optional. These endpoints take several weeks to evaluate 
and are affected not only by estrogens but by environmental 
antiandrogens, drugs that affect the hypothalamic-pituitary axis 
(Hostetter and Piacsek 1977; Ramaley and Phares 1983), and by prenatal 
exposure to 2,3,78-tetrachlorodibenzo-p-dioxin (TCDD) (Gray et al. 
1995a; Bjerke and Peterson 1994) or dioxin-like PCBs (Gray et al. 
1995b). In contrast to these other mechanisms, only peripubertal 
estrogen administration accelerates this process in the female and 
delays it in the male. Preputial separation in the male rodent is easy 
to measure and this is not a terminal measure (Korenbrot et al. 1977). 
Age and weight at puberty, reproductive organ weights, and serum 
hormone levels can also be measured.
    As indicated in this unit, the determination of the age at 
``puberty'' in the male rat uses endpoints that already have gained 
acceptance in the toxicology community. Preputial separation in the 
male is a required endpoint in the new EPA 2-generation reproductive 
toxicity test guideline. In this regard, this assay would be easy to 
implement because these endpoints have been standardized and validated 
and PPS data are currently being collected under Good Laboratory 
Practice (GLP) conditions in most toxicology laboratories. In addition, 
PPS data are reported in many recently published developmental 
reproduction studies (i.e., see studies from R.E. Peterson's, J. 
Ashby's, R. Chapin's, and L.E. Gray's laboratories on dioxins, PCBs, 
antiandrogens, and xenoestrogens).
    4. Selection of doses in screening assays. All in vitro screening 
assays (including the steroidogenesis assay) will involve multiple-dose 
levels, whether performed by HTPS or bench level methods, so a dose-
response curve and assessment of relative potencies can be developed. 
EDSTAC recommended that in vivo screening assays be conducted at a 
single-dose level to save testing resources. In comments on the draft 
EDSTAC Report the SAB/SAP raised concern that relying on a single-dose 
level might give false negative results. EPA believes this question can 
be resolved in the standardization and validation program. EPA will 
require one-, two-, or three-dose levels for in vivo screens depending 
upon the results of the standardization and validation program. 
Information to assist in selecting the doses in the in vivo screens 
includes:
    i. Prior information, such as that available during the priority-
setting phase.
    ii. Results from the HTPS (or its equivalent bench-level assays).
    iii. Results from range-finding studies, utilized for T1S dose 
selection.
    Results from the HTPS (or its equivalent) will provide potency 
information (i.e., EC 50) relative to a positive control such as 17-
beta estradiol (E2), diethylstilbestrol (DES), or T for those chemical 
substances or mixtures which bind to the estrogen or androgen 
receptors. Information on the in vitro effective doses of E2, DES, or 
T, can be used to set the dose level(s), based on the validation 
process, for the in vivo Tier 1 screening assays for these chemical 
substances or mixtures.
    It may be more cost effective to conduct the shortest of the in 
vivo screening assays at several doses without the intermediate step of 
a range finding study since repeating the study at different doses in 
the event that inappropriate doses are used would be relatively 
inexpensive. A range-finding study can be performed at multiple dose 
levels (at least five) with a few animals per dose level and a limited 
number of relevant endpoints. In general, range-finding studies should 
meet the following guidelines:
    i. Use of the same species strain, sex(es), and age in the assay 
for which it is being performed (principal study).
    ii. Use of the same route of administration, vehicle, and duration 
of dosing as in the principal study.
    iii. Use of multiple dose levels; the number of dose levels will 
depend on the availability and extent of prior information.
    iv. Use of multiple animals per dose level which may be fewer than 
the number used per group in the assay.
    v. Use of relevant endpoints, which may be more limited than those 
in the main assay; for example, the range-finding study for the 
uterotrophic assay may employ only body weights and uterine wet weight, 
while the full screening assay may also evaluate uterine gland height, 
serum hormone levels, and/or vaginal cornification, etc.
    vi. Use of comparable animals, e.g., ovarectomized females for the 
uterotrophic range-finding study or castrated males for the Hershberger 
range-finding assay. However, there may be circumstances under which 
exceptions occur, e.g., use of intact males in the range-finding study 
for the Hershberger assay to define doses producing systemic toxicity 
and any effects on the reproductive system as a first pass 
approximation.
    vii. Use of more than one range-finding study if the initial 
version does not identify the dose level(s) to be used in the specific 
Tier 1 screening assay if necessary by extrapolation or interpolation.
    The doses to be selected for the in vivo assays should not result 
in excessive systemic toxicity, but should result in effects useful for 
detection of potential EAT disruption. However, no-dose level higher 
than one gram/kilogram body weight/day (i.e., a ``limit'' dose) should 
be utilized. The rationale for selection of dose levels for each range-
finding study, all of the results for such studies, and the logic 
employed to select the dose level(s) for the principal study should be 
included in the submission of study results for evaluation by the 
Agency as to the appropriateness of the study design, conduct, and 
conclusions.

B. Tier 2 Testing

    The purpose of Tier 2 testing is to characterize the likelihood, 
nature, and dose-response relationship of the endocrine disruption of 
EAT in humans, fish, and wildlife. To fulfill this purpose, the tests 
are longer-term studies designed to encompass critical life stages and 
processes, a broad range of doses, and administration of the chemical 
substance by a relevant route of exposure, to identify a more 
comprehensive profile of biological consequences of chemical exposure 
and relate such results to the dose or exposure which caused them. Dose 
selection, specifically the use of environmentally relevent low doses 
for endocrine disruptor testing, has not been conclusively resolved. 
The EPA will continue its collaborations with other Federal agencies, 
industry, and environmental and public health organizations regarding 
low-dose research projects to resolve outstanding scientific questions. 
Effects associated with endocrine disruption may be latent and not 
manifested until later in life or may not appear until the reproductive 
period is reached. Unless a rationale exists to limit the test to 1 
generation, tests for endocrine disruption will usually encompass 2 
generations including effects on fertility and mating, embryonic 
development, sensitive neonatal growth and development, and 
transformation from the juvenile life stage to sexual maturity.
    The outcome of Tier 2 is designed to be conclusive in relation to 
the outcome

[[Page 71555]]

of Tier 1 and any other prior information. Thus, a negative outcome in 
Tier 2 will supersede a positive outcome in Tier 1. Furthermore, each 
full test in Tier 2 has been designed to include those endpoints that 
will allow a definitive conclusion as to whether or not the tested 
chemical substance or mixture is or is not an endocrine disruptor for 
EAT in that species/taxa. Conducting all five tests in the Tier 2 
testing battery would provide a more comprehensive profile of the 
effects a chemical substance or mixture could induce via EAT disruption 
mode(s)/mechanism(s) of action than would be the case if only a subset 
of tests or less comprehensive tests were performed. Considerations for 
determining whether the full battery of comprehensive tests should be 
implemented include an understanding of mechanisms of action, 
environmental fate and transport, persistence, potential for 
bioaccumulation, and potential exposure. EPA plans to require that all 
tests be performed in Tier 2 with all endpoints, unless compelling 
information is presented to show why testing should be limited.
    Despite the design of Tier 2 to be as definitive as possible, there 
will always be situations in which ambiguous results are obtained. In 
some of these cases a weight of evidence approach using Tier 1 and Tier 
2 data together may resolve the ambiguity. In others, it may be 
necessary to conduct additional special studies or to repeat a test to 
resolve the data interpretation issues.
    1. Tier 2 tests. EPA is proposing that the Tier 2 test battery 
include the following tests: 2-Generation Mammalian Reproductive 
Toxicity Study, Avian Reproduction, Fish Reproduction, Amphibian 
Reproduction and Developmental Toxicity, and Invertebrate Reproduction.
    Except for the amphibian reproduction and developmental toxicity 
study, these tests are routinely performed for pesticides with 
widespread outdoor exposures that are expected to affect reproduction. 
Modifications to each may be necessary to enhance the ability to detect 
endocrine-related effects. The amphibian test, though not standardized, 
is important because of the extensive fundamental knowledge base on 
amphibian development and the realization that amphibians may serve as 
key indicators of the health of the environment.
    There is utility in considering the results of the entire battery 
when assessing human risk. For instance, if the results from different 
taxa produce similar results, one can feel more confident that the 
results are generally applicable to humans. If the results are widely 
divergent, either qualitatively or quantitatively, it indicates greater 
biological variability and perhaps additional caution in conducting a 
hazard assessment.
    i. Mammalian reproductive toxicity. The 2-generation reproductive 
toxicity study in rats (40 CFR 799.9380; OPPTS Guideline 870.3800; OECD 
Guideline No. 416, 1983; FIFRA, Subdivision F, Guidelines 83-4) is 
designed to evaluate comprehensively the effects of a chemical on 
gonadal function, estrous cycles, mating behavior, fertilization, 
implantation, pregnancy, parturition, lactation, weaning, and the 
offspring's ability to achieve adulthood and successfully reproduce, 
through 2 generations, one litter per generation. While administration 
is usually oral (dosed feed, dosed water, or gavage), other routes are 
acceptable if justified (e.g., inhalation). In addition, the study also 
provides information about neonatal survival, growth, development, and 
preliminary data on possible teratogenesis.
    In the existing 2-generation reproductive toxicity test, a minimum 
of three-treatment levels and a concurrent control group are required. 
At least 20 males and sufficient females to produce 20 pregnant females 
must be used in each group as prescribed in this current guideline. The 
highest dose must induce toxicity (or meet the limit dose requirement) 
but not exceed 10% mortality. In this study, potential hormonal effects 
can be detected through behavioral changes, ability to become pregnant, 
duration of gestation, signs of difficult or prolonged parturition, 
apparent sex ratio (as ascertained by anogenital distances) of the 
offspring, feminization or masculinization of offspring, number of 
pups, stillbirths, gross pathology and histopathology of the vagina, 
uterus, ovaries, testis, epididymis, seminal vesicles, prostate, and 
any other identified target organs.
    Table 2 provides a summary of the endpoints evaluated within the 
framework of the experimental design of the updated 2-generation 
reproductive toxicity test (and some recommended additional endpoints 
for validation and inclusion to cover EAT concerns). These endpoints 
are comprehensive and cover every phase of reproduction and 
development. Tests that measure only a single dimension or component of 
hormonal activity, (e.g., in vitro or short-term assays) provide 
supplementary and/or mechanistic information cannot provide the breadth 
of information that is critical for risk assessment.
    Additionally, in this study type, hormonally induced effects such 
as abortion, resorption, or premature delivery as well as abnormalities 
and anomalies such as masculinization of the female offspring or 
feminization of male offspring, can be detected. Substances such as the 
phytoestrogen, coumesterol, and the antiandrogen cyproterone acetate, 
which possess the potential to alter normal sexual differentiation, 
were similarly detected in this study test system (i.e., 1982 
Guideline).
    Table 2 contains two types of lists: First, those endpoints 
required in current EPA harmonized 1998 test guidelines; second, 
additional endpoints recommended by EDSTAC for validation and inclusion 
in both the recommended 2-generation test, as well as the alternative 
mammalian tests discussed in Unit V.B.3. of this notice. These 
additional endpoints will detect EAT effects.
    The default assumption is that all of these endpoints would be 
evaluated unless the conditions which are set forth in the guidelines 
for determining the selection of endpoints are met.

    Table 2.--Mammalian Tier 2 Test Endpoints

Current Guideline Endpoints Sensitive to Estrogens/Antiestrogens

sexual differentiation
gonad development (size, morphology, weight)  accessory 
sex organ (ASO) development
ASO weight  fluid; histology
sexual development and maturation: Acquisition of vaginal patency 
(VP), PPS
fertility
fecundity
time to mating
mating and sexual behavior
ovulation
estrous cyclicity
gestation length
abortion
premature delivery
dystocia
spermatogenesis
epididymal sperm numbers and morphology; testicular spermatid head 
counts; daily sperm production (DSP); efficiency of DSP
gross and histopathology of reproductive tissues
anomalies of the genital tract
viability of the conceptus in utero (prenatal demise)
survival and growth of offspring
maternal lactational behaviors (e.g., nursing, pup retrieval, etc.)

Current Guideline Endpoints Sensitive to Androgens/Antiandrogens

altered apparent sex ratio (based on AGD)
malformations of the urogenital system
altered sexual behavior
changes in testis and ASO weights
effects on sperm numbers, morphology, etc.
retained nipples in male offspring

[[Page 71556]]

altered AGD (now triggered from PPS/VP)
reproductive development; PPS/VP (puberty)
male fertility
agenesis of prostate
changes in androgen-dependent tissues in pups and adults (not 
limited to sex accessory glands)

Recommended Additional Estrogen/Androgen Endpoints for Validation 
and Inclusion

ASO function (secretory products)
sexual development and maturation (nipple development and retention)
androgen and estrogen levels
LH and FSH levels
testis descent

Current Guideline Endpoints Sensitive to Thyroid Hormone

Agonists/Antagonists (general)
growth, body weight
food consumption, food efficiency
developmental abnormalities
perinatal mortality
testis size and DSP
VP; PPS

Recommended Additional Thyroid Endpoints for Validation and 
Inclusion

neurobehavioral deficits (see developmental landmarks in this unit)
TSH, T4, thyroid weight and histology (e.g., goiter)
developmental landmarks:
prewean includes pinna detachment, surface righting reflex, eye 
opening, acquisition of auditory startle, negative geotaxis, mid-air 
righting reflex, motor activity on PND 13, 21, etc.
postwean includes motor activity PND 21 and postpuberty ages (sex 
difference); learning and memory PND 60--active avoidance/water maze
brain weight (absolute), whole and cerebellum
brain histology

    ii. Avian reproduction test. While birds are not included as 
subjects in the Tier 1 screening battery, it is important to evaluate 
the effects of exposure of birds to chemical substances or mixtures 
with endocrine activity.
    EPA is planning to modify its Avian Reproduction Test guideline 
(OPPTS Guidelines 850.2300) for use in the endocrine disruptor testing 
program. The modification include: The additional endpoints presented 
in this unit to make the test more sensitive to chemical substances or 
mixtures with endocrine activity. Table 3 provides a summary of the 
endpoints evaluated within the framework of the Avian Reproduction Test 
(and recommended additional endpoints for validation and inclusion to 
cover EAT concerns). Two important extensions of this guideline include 
modification and standardization of the husbandry and dosing of the 
offspring from EPA's Avian Reproduction Test guidelines (OPPTS 
Guidelines 850.2300) to create a 2-generation avian reproduction test 
and evaluation of an additional exposure pathway (i.e., direct topical 
exposure, which is common in the wild, by dipping eggs). The extensions 
to the guideline are outlined in Appendix Q in the EDSTAC Final Report 
(EDSTAC, 1998).
    In the current Avian Reproduction Test guidelines, two species are 
commonly used, mallards and northern bobwhite. Exposure of adults 
begins prior to the onset of maturation and egg laying and continues 
through the egg-laying period; their offspring are exposed, in early 
development, by material deposited into the egg yolk by the females. 
These offspring can be used efficiently to test for the effects of 
chemical substances or mixtures on avian development. There are several 
endpoints currently required (see OPPTS Guidelines 850.2300(c)(2)) that 
are particularly relevant to disruption of endocrine activity, 
including: Eggs laid, cracked eggs, eggshell thickness, viable embryos, 
and chicks surviving to 14 days. EPA is extending the guidelines to 
require: Additional measurements of circulating steroid titers, thyroid 
hormones, major organ (including brain) weights, gland weights, bone 
development, leg and wing bone lengths, and ratios of organ weights to 
bone measurements; skeletal x-rays; histopathology; functional tests; 
and assessment of reproductive capability of offspring (Baxter et al. 
1969; Bellabarba et al. 1988; Dahlgren and Linder 1971; Emlen 1963; 
Cruickhank and Sim 1986; Fleming et al. 1985a; Fleming et al. 1985b; 
Fox 1976; Fox et al. 1978; Freeman and Vince 1974; Hoffman and Eastin 
1981; Hoffman and Albers 1984; Hoffman 1990; Hoffman et al. 1993; 
Hoffman et al. 1996; Jefferies and Parslow 1976; Kubiak et al. 1989; 
Maguire and Williams 1987; Martin 1990; Martin and Solomon 1991; 
McArthur et al. 1983; McNabb 1988; Moccia et al. 1986; Rattner et al. 
1982; Rattner et al. 1987; Summer et al. 1996; Tori and Mayer 1981).

    Table 3.--Avian Reproduction Test Endpoints

Current Guideline Endpoints Sensitive to Estrogens/Antiestrogens, 
Androgens/Antiandrogens, and/or HPG Axis

egg production
eggs cracked
viable embryos (fertility)
eggshell thickness
fertilization success
live 18-day embryos
hatchability
14-day-old survivors

Recommended Additional Endpoints for Validation and Inclusion

sex ratio
major organ (including brain) weights
gland weights
histopathology
plasma steroid concentrations
neurobehavioral test (e.g., nest attentiveness)

Current Guideline Endpoints Sensitive to Thyroid Hormone Agonists/
Antagonists

body weight of adults
food consumption of adults
body weight of 14-day-old survivors
developmental abnormalities

Recommended Additional Endpoints for Validation and Inclusion

plasma T3/T4
thyroid histology
bone development (skeletal x-ray)
ratio of organ weights to bone measurements
neurobehavioral test (cliff test)
cold stress test

    iii. Fish reproduction test. Fish are the most diverse of all 
vertebrates. Reproductive strategies extend from oviparity, to 
ovoviviparity, to true viviparity. The consequences of an endocrine 
disruptor may be quite different across the many families of fishes. As 
a first step though, EPA plans to require use of fathead minnows, or in 
special cases, sheepshead minnows in the Fish Life Cycle Test. The Fish 
Life Cycle Test consists of continuous exposure from fertilization 
through development, maturation, and reproduction, and early 
development of offspring with a test duration of up to 300 days. EPA 
also anticipates use of the fathead minnow in the Tier 1 fish gonadal 
recrudescence assay, and as such, the relevance of any activity 
detected in the screening assay would be evaluated. If exposure to a 
particular chemical substance or mixture is predominantly estuarine or 
marine, EPA may require use of the estuarine sheepshead minnow 
(Cyprinodon variegatus) in the test. However, EPA will permit 
flexibility to species selection with appropriate justification as to 
species choice by the test sponsor.
    The Fish Life Cycle Test (OPPTS 850.1500) follows procedures 
outlined in (Benoit 1981) for the fathead minnow and (Hansen et al. 
1978) for the sheepshead minnow. In general, the test begins with 200 
embryos distributed among eight incubation cups in each treatment 
group. When hatching is completed, the number of larvae are reduced to 
25 individuals, if available, which are released to each of four 
replicate larval growth chambers. Four weeks following their release 
into the larval growth chambers, the number of juvenile fish are 
reduced again and 25 individuals, if available, distributed to each of 
two replicate adult test chambers. When fish reach sexual

[[Page 71557]]

maturity, fish are separated into spawning groups (pairs or one male/
two females) with a minimum of eight breeding females. Remaining adults 
will be maintained in the tank but will be segregated from the spawning 
groups. Adults will be allowed to reproduce, at will, until the 300th 
day of exposure. Alternatively, the test may be continued past 300 days 
until 1 week passes in which no eggs from any group have been laid. The 
embryos and fish are exposed to a geometric series of at least five 
test concentrations, a negative (dilution water) control, and, if 
necessary, a solvent control.
    Assessment of effects on offspring of the parental group (first 
filial or F1 generation) will be made by collecting two groups of 50 
embryos from each experimental group and incubating those embryos. When 
embryos hatch, the number of larvae hatched from each group will be 
impartially reduced to 25, if available, and released into the larval 
growth chambers. After 4 weeks of exposure, lengths, and weights of 
surviving individuals will be recorded.
    Observations are made of the effects of the test substance on 
embryo hatching success, larvae-juvenile-adult survival, growth of 
parental and F1 generation, and reproduction of the adults. Table 4 
provides a summary of the endpoints evaluated within the framework of 
the Fish Life Cycle Test (and recommended additional endpoints for 
validation and inclusion to cover EAT concerns).

    Table 4.--Fish Reproduction Test Endpoints

Current Guideline Endpoints Sensitive to Estrogens/Antiestrogens, 
Androgens/Antiandrogens, and/or HPG Axis

viability of embryos
time to hatch
spawning frequency
egg production
fertilization success

Recommended Additional Endpoints for Validation and Inclusion

sexual differentiation (tubercle formation, gonadal histology)
sex ratio
gonadosomatic index
gamete maturation (production, final oocyte maturation, sperm 
motility test, etc.)
vitellogenin
plasma steroid concentrations
in vitro gonadal steroidogenesis

Current Guideline Endpoints Sensitive to Thyroid Hormone Agonists/
Antagonists

growth, length, and body weight
developmental abnormalities

Recommended Additional Endpoints for Validation and Inclusion

plasma T3/T4
thyroid histopathology
bone development (skeletal x-ray)
ration of organ weights to bone measurements
neurobehavioral test (cliff test)
cold stress test

    iv. Invertebrate reproduction test. Although invertebrates do not 
generate EAT, EPA plans, through use of this test, to examine in more 
depth invertebrate hormones that are functionally equivalent to EAT. 
The species of choice would be mysids or daphnia.
    Although neither the daphnia nor the mysid chronic test was 
designed to examine endocrine-specific endpoints, both species are 
crustaceans and therefore share common physiology. Ecdysone is a 
steroid hormone that regulates growth and molting in arthropods, and 
exhibits some functional and structural similarities to estrogen. The 
central role of ecdysone makes it an attractive candidate for examining 
endocrine effects in invertebrates; however, other possibilities also 
exist. Morphogenetic and reproductive development of arthropods is 
controlled in part by juvenile hormone (JH). Methyl farnesoate is a JH 
like compound that may play a role in reproduction and development 
(Borstet et al. 1987; Laufer et al. 1987a,b).
    Invertebrate hormones are beyond the immediate scope of the EDSTAC 
which has focused on the vertebrate EAT. Nevertheless, invertebrate 
hormones that are functionally equivalent to EAT need to be examined in 
more depth. More importantly, chemicals that affect these vertebrate 
hormones may also affect invertebrate hormones resulting in altered 
reproduction, development, and growth.
    Chemicals with estrogenic properties are reported to have altered 
normal function of ecdysone systems (Mortimer 1993, 1994, 1995a, 1995b; 
Chu et al. 1997). Satyanarayana et al. 1994 showed stimulation of 
vitellogenin in insect prepupae and pupae by methoprene, a JH mimic 
with retinoid properties. Whether vitellogenin production is controlled 
through either an estrogen receptor or an alternative mechanism is not 
crucial for obtaining test results that show alteration occurs.
    Therefore, the mysid shrimp chronic life cycle test (OPPTS 
850.1350) may be adapted to determine whether chemicals that affect 
hormonal activity in vertebrates also affect arthropods. Once adapted 
to include reproductive and developmental endpoints relevant to the 
EDSP, the test could be a useful component in screening and testing.
    The other common invertebrate bioassay, one using the water flea, 
daphnia, is used internationally (OECD Guideline No. 202). It 
incorporates life cycle assessment and reproductive and developmental 
endpoints, albeit applied quite differently in this group of animals. 
Reproduction is usually parthenogenic in the laboratory in these 
animals, limiting the applicability to endpoints identified in this 
report. The particular aspect of this system is that the daphnia is 
sensitive to estrogenic compounds (Baldwin et al. 1995; Baldwin et al. 
1997; Shurin and Dodson 1997), and possesses receptors for T, making 
the system sensitive to another vertebrate hormone. Again, this 
bioassay would have to be adapted for the endpoints and processes of 
interest in the EDSP as a protocol for including invertebrate species 
in the endpoints addressed by the EDSP screening and testing batteries. 
Other invertebrates, such as molluscs, crayfishes, and echinoderms, do 
have EAT, but again relevant standardized tests for evaluating the 
consequences of interfering with these systems are not currently 
available. It is simply not known whether one (mysid) or two (mysid and 
daphnia) Tier 2 tests will provide sufficiently valid information for 
other invertebrate groups not tested. This is a source of uncertainty, 
potentially leading to Type II errors of unknown magnitude. These 
issues will be addressed during the development and validation of this 
assay.
    v. Amphibian development and reproduction. A definitive amphibian 
test, which exposes larvae through metamorphosis and reproduction, is 
important to evaluate the consequences of endocrine disruption in 
poikilothermic oviparous vertebrate distinct from fishes. A rich 
literature on metamorphosis, growth, and reproduction exists for frogs. 
No established method has been identified which is suitably 
comprehensive to serve as a Tier 2 test at this time but a promising 
method is under development by EPA.
    2. Alternative test procedures--i. Alternative Mammalian 
Reproduction Test (AMRT). One alternative to the 2-generation test 
procedure in Unit V.B.1.i. of this notice is the AMRT. The objectives 
of this test are to describe the consequences of in utero and/or 
lactational exposure on reproduction and development from compounds 
that displayed EAT activity in the Tier 1 screens. If validated, this 
test may be used, under certain defined circumstances, instead of the 
recommended 2-generation reproductive toxicity test (TSCA guidelines, 
1997) in Tier 2 tests. In this regard, the test will be conducted with

[[Page 71558]]

at least three treatment groups plus a control and include endpoints 
sensitive to chemicals that alter development via EAT activities. As 
with the 2-generation mammalian reproductive toxicity study, the 
default assumption is that all of the endpoints would be evaluated in 
the AMRT, unless the conditions set forth in the guidelines for 
determining the selection of endpoints are met.
    The AMRT involves exposure of maternal rats (designated F0 
generation) from gestational day 6 (time of implantation), through 
parturition (birth), and through the lactation period until weaning of 
offspring (designated F1 generation) on post-natal day 21. F1 offspring 
(both sexes) are retained after weaning with no exposures for 10 weeks 
and then mated within groups. F1 males are necropsied after the mating. 
F1 females and their litters (designated the F2 generation) are 
retained until the F2 generation is weaned. F0 females (and a subset of 
F1 weanlings) are necropsied with organ weights and possible 
histopathology. F1 animals are evaluated for reproductive development 
(VP, PPS), estrous cyclicity, and, at necropsy, for organ weights, 
possible histopathology, andrological assessments, and T3/T4 (with TSH 
triggered). F2 weanlings are counted, sexed, weighed, examined 
externally, and discarded.
    The AMRT differs from the ``standard'' 2-generation study design in 
that it:
    a. Does not include exposures prior to mating, during mating, or 
during the early pre-implantation stage of pregnancy in the dams.
    b. Does not include exposures to parental males.
    c. Does not include direct exposure to the postweanling offspring; 
potential exposure is limited to in utero transplacental and/or 
lactational routes.
    The AMRT differs from the 1-generation test (see Unit V.B.2.ii. of 
this notice) in that its study design provides for:
    a. Exposure to the F0 dam only from gestational day 6 through 
weaning of the F1 offspring on post-natal day 21.
    b. No exposure to parental males.
    c. Mating of the F1 animals (who have not been directly exposed) to 
produce F2 offspring.
    d. Following the F2 offspring to weaning (post-natal day 21).
    ii. 1-Generation reproduction toxicity test. A second alternative 
to the standard 2-generation reproductive toxicity test is a 1-
generation reproductive toxicity test, which has been used in rats and 
mice. The 1-generation reproductive toxicity test has been used as a 
range-finding study prior to performance of a guideline 2-generation 
(or more) study for the last 10 years under EPA (TSCA/FIFRA) GLPs; the 
design is similar to that used by Sharpe et al. 1996. This is a 
shortened, scaled-down version of the new draft OPPTS and Final TSCA 
guidelines for reproductive toxicity testing. As with the 2-generation 
mammalian reproductive toxicity study, the default assumption is that 
all of the endpoints would be evaluated in the 1-generation test, 
unless the conditions set forth in the guidelines for determining the 
selection of endpoints are met.
    The 1-generation test is a less comprehensive evaluation of 
functional reproductive development than the AMRT (since it does not 
follow F1 animals through production of F2 offspring), but it has the 
advantage of assessing post-natal development and adult reproductive 
capacity after in utero lactational and post-lactational exposure. In 
the presence of continued exposure, the post-natal component of the 
test is extended to evaluate acquisition of VP, PPS, estrous cyclicity, 
and andrological assessments in the F1 offspring. Inappropriate 
retention of Mullerian duct derivations (e.g., oviducts) in males and 
of Wolffian duct derivatives (e.g., seminal vesicles, epididymides) in 
females can be identified in all three proposed tests (with or without 
satellite F0 females and examination of term fetuses).
    The 1-generation test involves a short prebreed-exposure period for 
male and female rats of the initial parental generation (designated 
F0), and exposure continues through mating, gestation, and lactation of 
F1 litters. F0 males are necropsied after F1 deliveries; F0 females are 
necropsied after F1 weaning. Postweanling F1 animals are directly 
exposed for a 10-week postwean period and are then necropsied. F1 
animals are evaluated for reproductive development (VP, PPS), estrous 
cyclicity and at necropsy for organ weights, possible histopathology, 
andrological assessments, and T3/T4 (TSH triggered). F0 animals will 
undergo the same necropsy assessments.
    The 1-generation test differs from the ``standard'' 2-generation 
study design in that it:
    a. Is shorter (basic design calls for 2 weeks but it can be 
extended) than the standard 2-generation study (10 weeks to encompass 
one full spermatogenic cycle in rats), though it does include a 
prebreed-exposure period.
    b. Does not evaluate effects of in utero and/or lactational 
exposure (and beyond) on generation of F2 offspring though it does 
include direct exposure of F1 offspring after weaning, including 
exposure through puberty and sexual maturation. F1 male and female 
reproductive organs (weight/histology), estrous cyclicity, and 
andrological endpoints are assessed at scheduled necropsy on post-natal 
day 90  2.
    The 1-generation test differs from the AMRT in that its study 
design provides for:
    a. Exposure to both male and female F0 parental animals prior to 
mating, during mating, and during gestation and lactation of F1 
offspring (F0 males are necropsied after F1 deliveries, F0 females are 
necropsied after F1 weaning).
    b. Direct exposure of postweanling F1 offspring after lactation 
until termination.
    c. No mating of F1 animals to produce F2 offspring.

C. Route of Administration

    As part of the test guideline, EPA will provide guidance on a route 
of administration for each screen and test. Tier 1 screening assays may 
employ dosing routes that maximize the likelihood of detecting 
endocrine activity such as ip. Conversely, Tier 2 tests will employ 
routes of administration based upon the most ecologically relevant 
exposure pathway to provide data relevant for risk assessment.
    The route of administration for the uterotrophic assay is sc 
injection while the route for the modified uterotrophic assay and 14-
day intact adult male assay with thyroid is an ip injection. The route 
for all other mammalian in vivo assays is gavage (orogastric 
intubation). The parenteral (non-oral) routes avoid the first-pass 
metabolic effect of the liver and will permit detection of potential 
endocrine disruptors that are active as parent compounds and which 
undergo significant first-pass metabolism. Hepatic xenobiotic 
metabolism does occur eventually after parenteral administration 
(substantially with ip), so the potential effects of metabolites will 
be evaluated as well by these routes. Compounds are occasionally 
metabolized by the gut microflora; this type of metabolism has been 
shown to be important for some plant-derived estrogens. The oral route 
of exposure will allow for this type of metabolism.

 VI. Implementation

    This section of the Federal Register notice discusses the 
implementation steps for the EDSP and many of the issues EPA must deal 
with in its implementation.

[[Page 71559]]

A. Overview of Implementation Steps and Timeline

    There are many elements associated with the development and 
implementation of the EDSP. A timeline that shows the key elements and 
their relationship to each other is provided in Figure 2.
    They include:


 
------------------------------------------------------------------------
           Implementation steps              Estimated completion dates
------------------------------------------------------------------------
EDSTAC Final Report and Recommendations     Completed
Development of EPA's EDSP                   Completed
Public comment on EPA's EDSP                February 26, 1999
SAB/SAP Peer Review Processes               April 1, 1999
HTPS Demonstration                          February 1999
HTPS                                        June 2000
EDPSD                                       June 2000
Priority Setting for Tier 1 Phase 1         November 2000
Tier 1 Standardization and Validation       2001
 September
Tier 1, Phase 1 TSCA Test Rule Notice of    December 2001
 Proposed Rulemaking (NPRM) and FQPA
 Orders
Tier 1, Phase 1 TSCA Final Test Rule        June 2003
------------------------------------------------------------------------


BILLING CODE 6560-50-F

[[Page 71560]]

[GRAPHIC] [TIFF OMITTED] TN28DE98.001


BILLING CODE 6560-50-C

[[Page 71561]]

    As noted, the recommendations of EDSTAC form the basis for EPA's 
endocrine-disruptor screening and testing strategy. Today, EPA is 
soliciting comments on its strategy for screening and testing 
substances for their potential to disrupt the EAT. These comments and 
the Agency's proposal will be reviewed by a joint meeting of the EPA 
SAB and FIFRA SAP in March 1999. Notice of the meeting site and 
specific times will be published in the Federal Register.
    EPA plans to begin running chemicals through the HTPS in August 
1999.
    The Agency will submit a report to Congress and plans to issue a 
notice in the Federal Register in the year 2000 adopting final policies 
for the screening program based on comments of the SAP/SAB and the 
comments received in response to this notice. The year 2000 notice will 
also propose the Priority List of chemicals and mixtures for Tier 1 
screening. The proposed screening Priority List will be based on 
information in the EDPSD including the results of the HTPS. EPA may 
also issue a procedural rule that describes the procedures related to 
implementation of the EDSP.
    EPA plans to publish the results of the standardization and 
validation effort for the screening battery along with guidelines for 
the screening assays that flow from this effort in the Federal Register 
in 2001. The standardization and validation of Tier 2 tests will be 
undertaken approximately in parallel with that of the screening 
battery. However, the test validation program is anticipated to take 
longer than the screening validation program because the Tier 2 tests 
take much longer to run than the Tier 1 screening assays.
    In late 2001, EPA plans to issue testing orders to the first group 
of pesticides and other chemical substances that are subject to the 
authority provided to EPA under the FFDCA and SDWA. In parallel to 
these activities, EPA may propose a TSCA test rule to require screening 
of chemicals that may not be covered by the FFDCA/SDWA. EPA could 
propose the TSCA test rule in 2001 and promulgate it in mid 2003. The 
screening program will operate in phases so as to not overwhelm 
resources. The number of phases and length of time between phases will 
depend on available resources and the number of chemicals proposed for 
screening in each phase. EPA plans to review its initial prioritization 
of chemicals and issue a separate proposed rule for each screening 
phase. This would allow the results from the first phase of screening 
to improve the priority setting for the second phase of screening.
    Tier 2 testing of chemicals that are part of the first phase of 
Tier 1 screening would begin after review of screening data indicated 
that testing was warranted. Standardization and validation of Tier 2 
tests will take from 2 to 5 years. EPA plans to require tests as soon 
as they are available and not wait for the full battery to initiate 
Tier 2 testing. Orders under FFDCA, FIFRA, or SDWA would be issued on 
individual chemicals as their review is completed. TSCA rules would be 
issued for a group of chemicals, probably on an annual basis.

B. HTPS Demonstration

    EPA has initiated a demonstration program to validate use of HTPS 
technology to screen chemical substances for EAT disrupting properties. 
The demonstration program is projected to be completed in February 
1999. If EPA successfully validates HTPS through the demonstration 
program, it could begin running chemical substances through HTPS in 
August of 1999.

C. HTPS Priority-Setting Project

    After completion of the HTPS demonstration and validation project, 
EPA plans to conduct the HTPS on approximately 15,000 chemicals 
(commercial chemicals produced in amounts greater or equal to 10,000 
pounds per year and all pesticides) to supplement existing information. 
EPA will fund the actual screening of these compounds and is soliciting 
industry cooperation in supplying samples of pesticides and 
commercially produced chemicals. One major issue in HTPS is how to deal 
with the need for analytical characterization of so many chemicals. The 
cost of chemical analysis is more than an order of magnitude greater 
than the cost of the HTPS battery.
    Option One is to require full analysis on each chemical prior to 
HTPS. This is the usual requirement for toxicological testing.
    Option Two is to perform chemical analysis after HTPS on those 
substances that test positive.
    Option Three is to rely on the chemical identity and composition 
claims of the chemical supplier.
    EPA favors Option Two as a cost effective alternative to full 
analysis of every chemical. Nevertheless, every sample submitted to EPA 
should be accompanied by some information regarding its analytical 
characterization. It should at a minimum state whether the material is 
a technical grade, analytical grade, etc., to what extent it has been 
characterized, and note the concentration or percentage of the sample 
comprised by the test substance.
    EPA plans to subject chemicals to HTPS that will bypass Tier 1 
screening as well as those that need screening. The rationale for 
conducting HTPS on these chemicals is:
    1. Data generated from the HTPS assays will be valuable for 
receptor-binding mechanisms even though such data by itself cannot be 
used to determine whether or not a chemical may be an endocrine 
disruptor.
    2. As an ancillary benefit, the data can be used to improve and 
validate QSAR models.
    3. For food-use pesticides that will probably undergo 
reregistration and tolerance reassessments prior to the availability of 
validated Tier 2 tests, HTPS data can be used along with other relevant 
testing information to help determine if and when they should undergo 
any additional endocrine-disruptor testing.

D. Priority-Setting Data Base (EDPSD) Development

    As described in Unit IV.C. of this notice, EPA plans to use 
existing exposure, effects and statutory-related data and information 
to sort and prioritize chemicals for endocrine-disruptor screening and 
testing. To maximize its resources, EPA will rely upon data excerpted 
in electronic format instead of primary literature. Recognizing the 
numerous data bases of potential utility to initial sorting priority 
setting (see Appendix H of the EDSTAC Final Report), EPA plans to 
assemble the relevant and useful data sources into a single-relational 
data base. Development of this data base was initiated by the EDSTAC 
but not completed due to time and resource constraints of the EDSTAC 
process. EPA has resumed efforts to complete development of the 
prototype EDPSD initiated by EDSTAC. EPA is publishing elsewhere in 
this issue of the Federal Register a document announcing a priority-
setting workshop for multi-stakeholders and the use of the EDPSD during 
the comment period.
    The purpose of the workshop is to provide stakeholders an 
opportunity for input into the design and implementation of the 
priority-setting system. The focus of the workshop is to discuss the 
basic structure and functioning of the priority-setting system. 
Specifically, the workshop will address the definition of compartments, 
principles and approaches for developing rankings within compartments, 
and for assigning overall

[[Page 71562]]

weighting factors to the various compartments and categories.

E. Process for Public Nominations for Chemical Screening

    Chemical nominations from the public were considered to be an 
important part of the nominations process by EDSTAC because they 
provide a mechanism to identify and screen chemicals which may result 
in high exposures in local communities but which do not receive 
national attention. EPA proposes to establish a nomination process. The 
nominations process could be a formal petition process or an informal 
one such as a letter submitted to the Agency. EPA belives that any 
nomination should be signed and should include the following 
information:
    Statement that it is nominating a chemical for screening in the 
EDSP, identification of the chemical.
    Statement of the reasons for its nomination.
    Although EPA does not believe it can legally protect the identity 
of nominators, employees in the chemical industry are protected by law 
against reprisals from employers for reporting a chemical under TSCA 
(15 U.S.C. 2622) and any threats or reprisal of any kind should be 
reported to the U.S. Secretary of Labor with a copy of the threat or 
reprisal report to the EPA Administrator.

F. Standardization and Validation of Assays, Screening Battery, and 
Tests

    Validation is the scientific process by which the reliability and 
relevance of an assay method are evaluated for the purpose of 
supporting a specific use (ICCVAM, 1997). Relevance refers to the 
ability of the assay to measure the biological effect of interest. 
Measures of relevance can include sensitivity (the ability to detect 
positive effects), specificity (the ability to give negative results 
for chemicals that do not cause the effect of interest), statistically 
derived correlation coefficients, and determination of the mechanism of 
the assay response with the toxic effects of interest. Reliability is 
an objective measure of a method's intra- and inter-laboratory 
reproducibility. The process of validation includes standardization, 
that is, definition of conditions under which the assay is run 
(species, strain, culture medium, dosing regimen, etc.). 
Standardization is critical to ensure reliability, that is, valid, 
consistent results between laboratories.
    FFDCA as amended by the FQPA requires EPA to ``develop a screening 
program, using appropriate validated test systems and other 
scientifically relevant information, to determine whether certain 
substances may have an effect in humans that is similar to an effect 
produced by a naturally occurring estrogen, or such other endocrine 
effect as the Administrator shall designate.''
    EPA convened a meeting of the Domestic Validation Task Force (Task 
Force) comprised of experts and representatives of major stakeholders 
on August 6, 1998, and is scheduled to meet on a bimonthly basis during 
1999. The Task Force is made up of members from Federal agencies, 
industry, and public interest groups. The purpose of the Task Force is 
to implement the validation program for the screens and tests. In March 
1998 and November 1998, the OECD Endocrine Disruptor Testing and 
Assessment Workgroup met to initiate an international validation 
program for endocrine-disruptor screening and testing. The 
international validation program is important in developing an 
internationally harmonized approach to endocrine-disruptor screening 
and testing. An internationally harmonized approach saves money by 
reducing duplicative testing. EPA anticipates that some, but by no 
means all, of the assays it is proposing will be included in the 
international validation program. The majority of the screening assays 
and the screening battery itself will have to be validated in the 
domestic validation program.
    Standard protocols for most of the screening assays and tests are 
now being developed. Most of these should be ready for Task Force 
review and approval in 1999. EPA is inviting laboratories to 
participate in the validation program. Laboratories that are interested 
in the participating in any aspect of the validation program should 
contact Anthony Maciorowski (see the ``FOR FURTHER INFORMATION 
CONTACT'' section of this notice). Participating laboratories will 
receive a standard protocol for each assay they want to conduct and 
appropriate control and test chemicals from the EPA or its agent. EPA 
is planning to begin the laboratory phase in the spring of 1999. Some 
assays which need further development will not begin validation until 
late 1999 or the year 2000.

G. Implementation Mechanisms

    As stated previously, EPA believes that the FFDCA and SDWA provide 
authority to require the testing of many of the approximately 87,000 
chemical substance that it wishes to test. As appropriate, EPA also 
will use other testing authorities, such as those under FIFRA and TSCA. 
Likewise, to the extent that EPA is concerned about the endocrine 
disrupting potential of other chemical substances, it will work with 
other Federal agencies and departments to ensure that these substances 
also are tested. EPA will determine under which authority it will 
require testing of specific chemicals on a case-by-case basis. A brief 
description of EPA's major testing authorities and guidance on their 
application to the EDSP are set forth in this unit.
    1. FFDCA testing authority. Under the FFDCA, as amended by FQPA, 
EPA has authority to order registrants, manufactures, or importers to 
test certain chemical substances, including pesticide chemicals and any 
other substance that may have an effect that is cumulative to an effect 
of a pesticide chemical if EPA determines that a substantial population 
may be exposed to such substances.
    Under the FFDCA, ``pesticide chemical'' includes ``any substance 
that is a pesticide within the meaning of FIFRA, including all active 
and inert ingredients.'' It also includes impurities (see 40 CFR 
177.81). The testing requirement is not restricted to pesticides used 
on foods.
    EPA is still working out how to determine whether a substance ``may 
have an effect that is cumulative to the effect of a pesticide 
chemical.'' However, at a minimum, EPA believes that if the mechanism 
of action of a pesticide chemical and a nonpesticide chemical is the 
same, their effects are additive and therefore may be cumulative. 
Likewise, when the metabolic detoxification or clearance process of a 
pesticide chemical and a nonpesticide chemical are the same, exposure 
to the nonpesticide chemical may slow the clearance of the pesticide, 
and therefore, increase the pesticide chemical's toxicity. This is an 
example of a cumulative effect even when the two chemicals do not 
operate by the same mechanism of toxicity or cause the same toxic 
effect. The same argument would also apply to enzyme poisons or 
noncompetitive inhibitors of pesticide metabolism that slow or 
completely block the metabolic pathway of a pesticide. EPA is 
interested in receiving comment on these and other examples or on 
methods to determine whether a substance may have an effect that is 
cumulative to the effect of a pesticide chemical.
    The phrase ``substantial population'' is used in FFDCA section 
408(p)(3)(B) and in SDWA section 1457 but is not defined in either of 
these statutes. Based upon EPA's experience under TSCA, it is necessary 
for the Agency to define this term. Under TSCA section 4(a)(1)(B) EPA 
defined ``substantial human

[[Page 71563]]

exposure'' in terms of numbers of persons exposed based on a sliding 
scale that reflected that more direct exposures would require smaller 
numbers of persons exposed in order to be substantial than less direct 
exposures would (58 FR 28736, May 14, 1993). EPA is offering no 
definition of ``substantial population'' for SDWA and FIFRA purposes at 
this time but seeks public comment on an appropriate definition.
    2. SDWA testing authority. Congress amended SDWA to give EPA 
authority to provide for the testing, under the FFDCA Screening 
Program, ``of any other substance that may be found in sources of 
drinking water if the Administrator determines that a substantial 
population may be exposed to such substance'' (42 U.S.C. 300j-17).
    Drinking water contaminants may include, but may not be limited to, 
pesticide active and inert ingredients and their degradates, commercial 
chemicals and their degradation products, substances formerly 
manufactured and used as pesticides or commercial chemicals (orphan 
chemicals), or natural substances.
    3. FIFRA testing authority. FIFRA section 3(c)(2)(B) provides EPA 
authority to require pesticide registrants to submit to EPA additional 
data regarding a pesticide if EPA determines that the additional data 
are required to maintain in effect an existing pesticide registration. 
Under this provision, EPA could require submission of endocrine effects 
data for registered pesticides and for chemicals that may have an 
effect that is cumulative to that of a pesticide. FIFRA sections 
3(c)(2)(A), 3(c)(5), 3(c)(7), and 3(d) also give EPA authority to 
require testing.
    4. TSCA testing authority. TSCA section 4 provides EPA with 
authority to require testing of certain chemical substances, not 
including pesticides or food additives among other things, if the 
Agency finds that the chemical substance or mixture:
    i. May present an unreasonable risk of injury to health or the 
environment.
    ii. There are insufficient data and experience from which the 
Agency can determine the effects of such substance or mixture on health 
or the environment.
    iii. Testing with respect to such substance or mixture with respect 
to such effects is necessary to develop such data.
    Alternatively, EPA can require testing if the Agency finds that:
    i. A chemical substance or mixture is or will be produced in 
substantial quantities and:
    a. It enters or may reasonably be anticipated to enter the 
environment in substantial quantities, or
    b. There is or may be significant or substantial human exposure to 
such substance or mixture.
    ii. There are insufficient data and experience which from which the 
Agency can determine the effects of such substance or mixture on health 
or the environment.
    iii. Testing with respect to such substance or mixture with respect 
to such effects is necessary to develop such data.
    EPA achieves TSCA testing through rulemaking and enforceable 
consent agreements (ECAs). For more information on EPA's TSCA testing 
authority see 40 CFR part 790.
    Some chemicals might be subject to more than one testing authority. 
Inert pesticide ingredients will frequently have TSCA uses in addition 
to their use as inert ingredients in pesticide formulations and could 
be screened or tested under TSCA or FFDCA/FIFRA authorities. TSCA 
chemicals found in drinking water sources could also be screened or 
tested under SDWA or TSCA. Compared with order authority under FIFRA, 
FFDCA, or SDWA, a test rule is a slow and labor intensive mechanism. 
Therefore, the Agency believes that when a choice is possible it is in 
the public interest to require screening and testing under its FIFRA, 
FFDCA, or SDWA authorities, rather than under TSCA, when it has that 
option.

H. Data Compensation Issues

    The FFDCA, as amended, requires EPA ``to the extent practicable,'' 
to ``minimize duplicative testing of the same substance for the same 
endocrine effect, [and] develop, as appropriate, procedures for fair 
and equitable sharing of test costs.''
    To meet these requirements, EPA is planning to adopt procedures 
similar, but not identical, to both TSCA's and FIFRA's data 
compensation procedures. If EPA knows that there is more than one 
registrant, manufacturer, and/or importer of a specific chemical, it 
will order each to test the chemical. As part of the order, it will 
include a list of all of the parties who receive equivalent orders and 
require the parties to work together to minimize duplicative testing 
and share testing costs. The parties may notify EPA of other parties 
not listed who also manufacture or import the chemical. Alternatively, 
or in addition, EPA will publish the order in the Federal Register and 
require parties not listed to self identify. If the parties are unable 
to work out testing and data compensation responsibilities, they will 
be required to submit to binding arbitration. If a party fails to 
comply with an arbitrator's decision, it will be subject to the 
penalties described in FFDCA section 408(p)(5)(C).
    If, after completion of the testing, another party seeks to use the 
resulting data in support of a pesticide registration, it will be 
required to comply with FIFRA sections 3(c)(1)(F) or 3(c)(2)(B) which 
require compensation for data. Likewise, TSCA requires parties to 
compensate test sponsors if they manufacture or import a substance 
covered by a test rule within 5 years of the submission of the last 
required study. Chemicals being tested pursuant to a rulemaking under 
TSCA will follow the TSCA procedures for reimbursement under 40 CFR 
part 791.

I. Data Submission and Collection

    EPA is proposing to post an electronic form for the capture of data 
from screening and testing so that these data can be easily uploaded 
into the Endocrine Knowledge Base (EKB) being developed by the FDA's 
National Center for Toxicological Research. The EKB will be the 
repository of all data from the EDSP as well as other sources of 
endocrine effects testing and research. The data base will thus serve 
research and regulatory purposes. As the data base is further 
developed, EPA will provide guidance on how to submit data 
electronically to be compatible with the EKB.

J. Data Release and CBI

    FFDCA section 408(p)(5)(B) requires that EPA, to the extent 
practicable, develop, as necessary, procedures for handling CBI 
submitted as part of the EDSP. EPA anticipates that much of the 
information that registrants and manufacturers submit under the 
auspices of its EDSP will be health and safety information that 
generally does not warrant CBI protection. Nevertheless, EPA is 
interested in receiving comments from potential data submitters 
concerning whether they think any of the information will deserve CBI 
protection. If data submitters believe that certain information will be 
deserving of protection, the Agency is interested in receiving comments 
on the specific types of information that might need protection and on 
procedures that the Agency could develop to verify the validity of CBI 
claims and to ensure protection of valid CBI. EPA also is interested in 
receiving comments on whether current procedures under FIFRA and TSCA 
would be adequate and, if so, how they should be applied.

[[Page 71564]]

 EPA is considering adopting FIFRA CBI procedures for data submitted on 
pesticide active ingredients and TSCA CBI procedures for all other 
substances. If necessary, EPA will develop additional procedures to 
ensure that any valid confidential business information is protected 
from disclosure.

K. Reporting Requirements Under TSCA 8(e) and FIFRA 6(a)(2)

    The following provides EPA's guidance on the reporting obligations 
under the TSCA section 8(e) and FIFRA section 6(a)(2) with respect to 
results from certain priority-setting studies and in vitro screening 
assays that industry or others may conduct voluntarily or as part of 
EPA's EDSP. TSCA section 8(e) requires that ``[a]ny person who 
manufactures, processes, or distributes in commerce a chemical 
substance or mixture and who obtains information which reasonably 
supports the conclusion that such substance or mixture presents a 
substantial risk of injury to health or the environment shall 
immediately inform [EPA] of such information'' (15 U.S.C. 2607(e)). 
Likewise, FIFRA section 6(a)(2) requires registrants that, after 
registration of a pesticide, have additional factual information 
regarding unreasonable adverse effects on the environment of the 
pesticide to submit the information to EPA ( 7 U.S.C. 136d(a)(2)).
    EPA will likely adopt as part of its EDSP both in vitro and in vivo 
assays that assess selected hormonal endpoints. Based on the current 
state of the science, EPA considers the results of endocrine disruptor 
in vitro screening assays to be indicators of potential endocrine 
activity. Whether performed at the bench or in a high throughput mode, 
results from in vitro assays may suggest some mechanisms of endocrine 
activity (e.g., hormone receptor binding, binding plus transcription, 
cell proliferation, steroidogenesis, etc.). Thus, the results of these 
in vitro assays are arguably within the scope of TSCA section 8(e) and 
FIFRA section 6(a)(2). At this time, however, EPA can not conclude that 
the results of these in vitro assays translate into an understanding of 
particular health or environmental hazards and risks in vivo. 
Therefore, based on the current state of the knowledge, EPA will not, 
at this time, require submission of TSCA section 8(e) or FIFRA section 
6(a)(2) reports containing only the results of these in vitro assays. 
Registrants, manufactures, or importers are, nevertheless, encouraged 
to submit the data voluntarily. If these test results are included with 
other information reportable under TSCA section 8(e) or FIFRA section 
6(a)(2), then they must be reported.

L. Exemptions

    There are several circumstances in which exemptions from screening 
or testing requirements are appropriate. The FFDCA section 408(p) 
provides for exemptions from its requirements if EPA determines that a 
substance is anticipated not to produce any effect in humans similar to 
an effect produced by a naturally occurring estrogen. Although EPA has 
not determined when or under what circumstances it will grant 
exemptions from FFDCA 408(p) requirements, examples of the types of 
chemicals that might warrant such exemptions include class 4 pesticide 
formulation inerts--those inert ingredients in pesticide formulations 
judged by EPA to be virtually non-toxic (for example cookie crumbs)--
and strong mineral acids and strong mineral bases, which would likely 
interact with tissue at the portal of entry giving rise to localized 
lesions rather than systemic effects. The strong reactivity of these 
substances would cause interaction with membranes and other biological 
chemicals before the chemical reached the endocrine receptors.
    EPA is considering establishing a petition process as a means of 
establishing exemptions from screening. The details of this process 
could be set forth in the procedural rule EPA is considering issuing 
for the EDSP. EPA is asking for comments on criteria that might form 
the basis for granting exemptions.
    Exemptions under FFDCA 408(p) are not the same as exemptions under 
FFDCA section 408(c). Please note also that the term exemption as used 
under FFDCA section 408(p) is different from, and should not be 
confused with, the use of this term under TSCA section 4(c). An 
exemption under FFDCA section 408(p) means that testing requirements do 
not apply. However, under TSCA section 4(c) an exemption is a mechanism 
for avoiding duplicative testing. Under TSCA section 4(c) an exemption 
can be granted when data are being or have been generated by a 
responsible party and, therefore, other responsible parties can 
reimburse the test sponsor for a portion of the cost. A similar cost 
sharing provision exists for data compensation among registrants under 
FIFRA (see Unit VI.H. of this notice). Unless otherwise indicated, the 
term exemption used in this notice will be used in the sense in which 
it is used under FFDCA section 408(p), that is, a waiver of all testing 
obligations.

M. Use of Significant New Use Rules (SNURs) Under TSCA

    During the EDSTAC deliberations, concern was expressed that under 
certain circumstances less than the full Tier 2 testing would be 
permitted on chemicals based on their limited use and exposure profile. 
For instance, a pesticide registered for contained use only may result 
in human exposure but negligible or no environmental exposure. 
Therefore, performing the 2-generation mammalian reproductive effects 
test may be all that is needed to assess the hazards of this substance. 
Granting permission to limit Tier 2 testing does not present a problem 
for pesticides because pesticide registration limits the uses of the 
pesticide to those contained in the registration application. If a 
pesticide registrant wants to expand the uses and therefore potentially 
the exposure to a pesticide, the registrant must apply to register the 
expanded uses. The same is not true for chemicals under TSCA, since 
TSCA is not a registration statute. Once a commercial chemical is on 
the market it can ordinarily be used freely for any purpose resulting 
in exposures that were not occurring at the time testing requirements 
were promulgated. A potential solution to this dilemma lies in EPA's 
authority under TSCA section 5(a)(2) to issue SNURs.
    A SNUR defines certain uses of a chemical as new uses. Before a 
manufacturer or processor can use a chemical for one of the defined new 
uses, the manufacturer or processor must notify EPA of such intention 
at least 90 days before commencement of the new use. A SNUR thus 
subjects an existing chemical that triggers a new use to the same 
review that a new chemical receives. Submission and review of the new 
use can be tied to the performance of testing and submission of test 
data to EPA if there is a test rule that covers that chemical.
    EPA is considering the development of a SNUR based on a 
manufacturer's showing of limited use and exposure as a condition for 
granting a waiver for limited Tier 2 testing for TSCA chemicals (i.e., 
permission to perform fewer than the five tests in Tier 2 based upon 
exposure considerations). If the manufacturer's claims for limited use 
and exposure are refuted in the significant new use rulemaking process 
by someone who is already using the chemical in such a manner, the SNUR 
will not be valid and the manufacturer will be required to perform the 
full battery of Tier 2 tests required in the test rule issued for that 
chemical under the EDSP.

[[Page 71565]]

N. Relationship Between the EDSP and Related Actions Under TSCA

    Several other testing actions under TSCA may affect chemicals in 
the EDSP. Actions planned or underway include the Hazardous Air 
Pollutants (HAPs) test rule (61 FR 33178, June 26, 1996) (FRL-4869-1) 
as amended, the Children's' Health test rule, the Agency for Toxic 
Substances and Disease Registry (ATSDR) test rule, the High Production 
Volume (HPV) testing initiative and the Screening Information Data Set 
(SIDS) Program on HPV chemicals. None of the EDSP Tier 1 screening 
assays is being considered for by these actions. The SIDS and HPV 
testing programs do not meet either the screening or testing 
requirements of the EDSP. The only likely overlap in testing 
requirements is the 2-generation mammalian test, which is proposed in 
the HAPs rule and being considered in the Children's Health test rule 
and ATSDR test rule. The reproductive effects testing for these 
programs will meet the Tier 2 mammalian reproductive effects testing 
requirement for the EDSP if the 1998 or later guideline for a 2-
generation mammalian reproductive effects study is used. The results 
from some of these testing programs likely will be available before 
final testing decisions are made under the EDSP. It is possible that if 
the results of the 2-generation test (with endocrine-sensitive 
endpoints including thyroid) generated under one of these other testing 
programs is negative that only the fish gonadal recrudescence assay 
would need to be performed to satisfy the testing requirements of the 
EDSP. The correlation of various test results in the validation study 
will provide more information on which to make this judgment. If the 
mammalian 2-generation test were positive, the other Tier 2 tests would 
have to be run depending upon the exposure profile of the chemical in 
question.

O. Analysis of Data in the EDSP

    EPA discussed use of HTPS data for priority setting for Tier 1 
screening and as part of the weight of evidence consideration to 
determine when a chemical should be tested in Tier 2. These data may 
also used in conjunction with other data to help determine if adverse 
effects observed in Tier 2 are due to endocrine disruption or from 
another cause. The Tier 1 data will also serve a dual purpose. They 
will be used to make the determination of which chemicals receive Tier 
2 testing and will also be used to help interpret positive results 
observed in Tier 2 testing.
    More detailed guidance regarding the assessment of hazards due to 
endocrine disruption must await both the results of the standardization 
and validation program and ongoing research. EPA intends to review the 
need for revising its standard evaluation procedures for interpreting 
studies and its human health and ecological risk assessment guidelines 
as relevant data from these programs become available.

VII. Issues for Comment

    1. The FFDCA, as amended, requires EPA to screen pesticides for 
estrogenic effects that may affect human health. EPA has decided that 
it is scientifically appropriate to focus on EAT effects, not just 
estrogenic effects. Is this an appropriate scope for the EDSP?
    2. Are there classes of chemicals besides the ones identified in 
Unit VI.L. of this notice that should be exempted (excluded) from the 
EDSP? What criteria and what burden of proof should be applied to 
claims of persons seeking to exempt chemicals from screening? What type 
of process should EPA establish?
    3. As discussed in Unit IV.E. of this notice, EPA is proposing a 
compartment-based (or set-based) approach to priority setting as a way 
of accommodating the real world situation of uneven data. Under the 
compartment-based approach, EPA will group the chemicals into sets 
based on the existence of factual information in a given area. Thus, 
priority ranking can be made fairly among chemicals, i.e., chemicals 
will compete for priority with other chemicals on the basis of 
comparable data and will not be assigned lower priority for lack of 
information. Are these principles and the compartment-based approach to 
priority setting reasonable? Are there alternatives to the compartment-
based approach which EPA should consider?
    4. As recommended by EDSTAC, EPA is proposing that polymers with an 
average number molecular weight greater than 1,000 daltons be excluded 
from priority setting and screening unless they are pesticide chemicals 
or unless their monomers, oligomers, or leachable components are shown 
to have endocrine-disrupting potential in Tier 1 screening. Is this 
approach scientifically sound?
    5. EPA is developing a relational data base to assist in setting 
priorities for screening. The relational data base is intended to 
import existing data and information and allow its synthesis, as well 
as the estimation of certain parameters through modeling. EPA and 
EDSTAC consider the relational data base to have great value in helping 
to identify the specific compartments under the compartment-based 
priority-setting approach. The data base will also be helpful in 
selecting chemicals for the first and subsequent rounds of screening. 
The data fields currently in the data base are defined in Chapter 4 of 
the EDSTAC Final Report. What additional data fields or types of data 
should EPA include as it further develops the relational data base?
    6. EPA is soliciting industry's cooperation in supplying chemicals 
for the HTPS. Is this an appropriate role for industry and is industry 
willing to do so?
    7. EPA plans to screen and, if appropriate, test representative 
mixtures to which large or identifiable segments of the population are 
exposed. The high-priority mixture categories include: Chemicals in 
breast milk, phytoestrogens in soy-based infant formulas, mixtures 
commonly found at Superfund sites, common pesticide/fertilizer mixtures 
found in ground and surface water, disinfection byproducts, and 
gasoline. EPA plans to screen and test one representative mixture from 
each category.
    a. Can standardized representative mixtures be developed? If so, 
how should the chemical combinations, ratios, and doses be selected for 
mixtures?
    b. Is the proposal a reasonable way to address the practicality of 
screening and testing mixtures?
    c. Are the six categories of mixtures the most appropriate to 
address first?
    d. Are there other mixture categories that should be included in 
addition to, or instead of those identified (e.g., Should fish tissue 
contaminants be one of the first mixtures)?
    e. If a mixture is positive in Tier 1, should the whole mixture be 
tested in Tier 2 or should EPA attempt to identify the active 
component(s) and test it (them) in Tier 2?
    8. EPA has identified a screening battery consisting of in vitro 
and in vivo assays to address EAT effects. Will the battery, once 
validated, be capable of detecting such effects in a consistent and 
reliable manner?
    9. EPA is planning to require that the Tier 1 screening in vivo 
assays be conducted at one dose, with appropriate use of range finding 
studies and other information (i.e., HTPS results) to inform dose 
selection. The single-dose approach was adopted to save testing 
resources. The SAB/SAP in a preliminary consultation raised concern 
about relying on only one dose level and suggested that EPA require a 
minimum of two doses and preferably three to ensure that tests did not 
result in false negatives. Does the potential risk of

[[Page 71566]]

false negatives outweigh the cost savings of running the Tier 1 
screening in vivo assays with only one dose?
    10. EDSTAC could not identify existing practical vertebrate 
endocrine disruptor screening assays that incorporated exposure in 
utero or in ovo. Do such screening assays exist?
    11. Is adequate coverage of the thyroid provided in the recommended 
Tier 1 screening battery? Does the Tier 1 screening battery provide 
adequate coverage of non-receptor mediated pathways?
    12. EPA is proposing a Tier 2 testing battery to delineate dose-
response relationships of chemicals that yield positive results in the 
screening battery. Do the tests provide sufficient rigor to identify 
adverse effects and establish dose response for disruption of the EAT?
    13. Will the Tier 2 tests be adequate to detect all known EAT 
endpoints in chemicals that bypass Tier 1 screening?
    14. Tier 2 tests will identify the adverse effects due to endocrine 
disruption as well as reproductive and developmental effects caused by 
non-endocrine mechanisms of toxicity. Thus, it may not be possible to 
determine that a substance is an endocrine disruptor if it bypasses 
tier 1 screening. Is it important to be able to identify substances as 
endocrine disruptors from the standpoint of conducting a hazard 
assessment?
    15. If the results of the 2-generation test (with endocrine-
sensitive endpoints including thyroid) generated under one of these 
other testing programs is negative what additional screening or testing 
should be required to demonstrate that the chemical is not an endocrine 
disruptor?
    16. FFDCA gives EPA authority to test pesticides and substances 
``that are cumulative to the effect of a pesticide.'' EPA is interested 
in receiving comment on how the term ``cumulative to the effect of a 
pesticide'' should be applied in defining additional substances which 
can be tested under FFDCA.
    17. How should EPA define substantial population as used in FFDCA 
section 408(p) and SDWA section 1457?
    8. Is EPA's proposal to adopt FIFRA cost sharing provisions for 
data received under FIFRA and TSCA cost sharing provisions for all 
other substances feasible and practical?
    19. Is EPA's proposal to adopt FIFRA CBI procedures for active 
pesticide ingredients and TSCA CBI procedures for all other substances 
feasible and practical? TSCA makes health and safety data freely 
available. The chemical portion of chemical substances comprising 
formulated products is confidential under both statutes.
    20. Should EPA permit chemicals to receive less than the full Tier 
2 testing battery under certain circumstances? Should EPA issue a SNUR 
for TSCA chemicals that are subject to limited Tier 2 testing?
    21. Should EPA issue a procedural rule codifying many of the 
procedures discussed in Unit VII. of this notice?

 VIII. References

    The Agency's actions are supported by the references listed in this 
unit and cited in this notice. These references are available in the 
public record for this notice under docket control number OPPTS-42208 
in the TSCA Docket, see the ``ADDRESSES''section in this notice.
    1. Anderson, S., S. Pearce, P. Fail, B. McTaggert, R. Tyl, and L.E. 
Gray (1995) ``Validation of the alternative reproductive test protocol 
(ART) to assess toxicity of methoxychlor in rats.'' The Toxicologist, 
15, pp. 164.
    2. Anderson, S., S. Pearce, P. Fail, B. McTaggert, R. Tyl, and L. 
Gray (1995b) ``Testicular and adrenal response in adult Long-Evans 
Hooded rats after antiandrogenic vinclozolin exposure.'' Journal of 
Andrology, 16, pp. 43.
    3. Baxter, W.L., R.L. Linder, and R.B. Dahlgren, (1969) ``Dieldrin 
Effects in Two Generations of Penned Hen Pheasants.'' Journal of 
Wildlife Management, 33(1), pp. 96-102.
    4. Bellabarba, D., S. Belisle, N. Gallo-Payet, and J.G. Lehoux 
(1988) ``Mechanism of Action of Thyroid Hormones During Chick 
Embryogenesis.'' American Zoologist, 28, pp. 389-399.
    5. Bjerke, D., and R. Peterson (1994) ``Reproductive toxicity of 
2,3,7,8 tetrachlorodibenzo-p-dioxin in male rats: Different effects of 
in utero versus lactational exposure.'' Toxicology and Applied 
Pharmacology, 127, pp. 241-249.
    6. Brown, D.D., Z. Wang, A. Kanamori, B. Eliceiri, J.D. Furlow, and 
R. Schwartzman (1995) ``Amphibian metamorphosis: a complex program of 
gene expression changes controlled by the thyroid hormone.'' Recent 
Progress in Hormone Research, 50, pp. 309-315.
    7. Cruickhank, J.J., and J.S. Sim (1986) ``Morphometric and 
Radiographic Characteristics Of Tibia Bone of Broiler Chickens with 
Twisted Leg Disorders,'' Avian Diseases, 30(4), pp. 699-708.
    8. Dahlgren, R.B., and R.L. Linder (1971) ``Effects Of 
Polychlorinated Biphenyls On Pheasant Reproduction, Behavior and 
Survival.'' Journal of Wildlife Management, 35(2), pp. 315-319.
    9. Edgren, R. (1984) ``Issues in animal pharmacology.'' 
Pharmacology of the contraceptive steroids. Ed J. Goldzieher, Raven 
Press, Ltd., New York.
    10. Emlen, Jr., J.T. (1963) ``Determinants of Cliff Edge and Escape 
Responses In Herring Gull Chicks in Nature.'' Behaviour, 22, pp. 1-15.
    11. Fleming, W.J., G.H. Heinz, and C.A. Schuler (1985a) ``Lethal 
and Behavioral Effects of Chlordimeform in Bobwhite.'' Toxicology, 36, 
pp. 37-47.
    12. Fleming, W. J., G.H. Heinz, J.C. Franson, and B.A. Rattner 
(1985b) ``Toxicity of Abate 4E (Temephos) in Mallard Ducklings and the 
Influence of Cold.'' Environmental Toxicology Chemistry, 4, pp.193-199.
    13. Fort, D. J., and E.I. Stover (1997) ``Development of Short-
Term, Whole-Embryo Assays to Evaluate Detrimental Effects on Amphibian 
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Volume), ASTM STP 1317, Dwyer, F.J., T.R. Doane, and M.I. Hinman 
(Eds.), American Society for Testing and Materials, Philadelphia, PA, 
pp. 376-390.
    14. Fox, G.A. (1976) ``Eggshell Quality: It's Ecological and 
Physiological Significance In a DDE-Contaminanted Common Tern Colony.'' 
Wilson Bulletin, 88(3), pp. 459-477.
    15. Fox, G.A., A.P. Gilman, D.B. Peakall, and F.W. Anderka (1978) 
``Behavioural Abnormalities of Nesting Lake Ontario Herring Gulls.'' 
Journal of Wildlife Management, 42, pp. 477-483.
    16. Freeman, B.M., and M.A. Vince (1974) ``Development of the Avian 
Embryo.'' A Behavioral and Physiological Study, John Wiley and Sons, 
New York, NY, pp. 362.
    17. Gonzalez, M.D., F. Lopez, and E. Aguilar (1983) ``Involvement 
of prolactin in the onset of puberty in female rats.'' Journal of 
Endocrinology, 101, pp. 63-68.
    18. Gray, L.E., Jr., J. Ostby, J. Ferrell, G. Rehnberg, R. Linder, 
R. Cooper, J. Goldman, V. Slott, and J. Laskey (1989) ``A dose-response 
analysis of methoxychlor-induced alterations of reproductive 
development and function in the rat.'' Fundamental and Applied 
Toxicology, 12, pp. 92-108.
    19. Gray, L.E., W.R. Kelce, E. Monosson, J.S. Ostby, and L.S. 
Birnbaum (1995a) ``Exposure to TCDD during development permanently 
alters reproductive function in male LE rats and Hamsters: Reduced 
ejaculated and epididymal sperm numbers and sex accessory gland weights 
in offspring with normal androgenic status.''

[[Page 71567]]

 Toxicology and Applied Pharmacology, 131 (1), pp.108-118.
    20. Gray, L.E., J. Ostby, C. Wolf, D. Miller, W. Kelce, C. Gordon, 
and L. Birnbaum (1995b) ``Functional developmental toxicity of low 
doses of 2,3,7,8 tetrachlorodibenzo-p-dioxin and a dioxin-like PCB 
(169) in Long Evans rats and Syrian hamsters: Reproductive, behavioral 
and thermoregulatory alterations.'' Organohalogen Compounds, 25, pp. 
33-38.
    21. Hannon, W., F. Hill, J. Bernert et al. (1978) ``Premature 
thelarche in Puerto Rico: a search for environmental estrogenic 
contamination.'' Archives of Environmental Contamination and 
Toxicology, 16, pp. 255-262.
    22. Hayes, T.B. (1997a) ``Amphian metamorphosis: An integrative 
approach.'' American Zoologist, 37, pp. 121-123.
    23. Hayes, T.B. (1997b) ``Steroids as potential modulators of 
thyroid hormone activity in anuran metamorphosis.'' American Zoologist, 
37, pp. 185-194.
    24. Hershberger, L., E. Shipley, and R. Meyer (1953) ``Myotrophic 
activity of 19-nortestosterone and other steroids determined by 
modified levator ani muscle method.'' Proceedings, Society of 
Experimental Biology and Medicine, 83, pp. 175.
    25. Hoffman, D.J. (1990) ``Embryotoxicity and Teratogenicity of 
Environmental Contaminants to Bird Eggs.'' Revision of Environmental 
Contamination and Toxicology, 115, pp.39-89.
    26. Hoffman, D.J., G. J. Smith, and B.A. Rattner (1993) 
``Biomarkers of Contaminant Exposure in Common Terns and Black-Crowned 
Night Herons in the Great Lakes.'' Environmental Toxicology and 
Chemistry, 12, pp. 1095-1103.
    27. Hoffman, D.J., M.J. Melancon, P.N. Klien, C.P. Rice, J.D. 
Eisemann, R.K. Hines, J.W. Spann, and G.W. Pendleton (1996) 
``Developmental Toxicity of PCB 126 (3,3',4,4',5-Pentachlorobiphenyl) 
in Nestling Amercian Kestrels (Falco sparverius).'' Fundmentals of 
Applied Toxicology, 34, pp. 188-200.
    28. Hostetter, M., and B. Piacsek (1977) ``The effect of prolactin 
deficiency during sexual maturation in the male rat.'' Biology of 
Reproduction, 17, pp. 574-577.
    29. Huhtaniemi, I., A. Amsterdam, and Z. Naor (1986) ``Effect of 
postnatal treatment with a gonadotropin-releasing hormone antagonist on 
sexual maturation of male rats.'' Biology of Reproduction, 35, pp. 501-
507.
    30. Interagency Coordinating Committee on the Validation of 
Alternative Methods (1997) ``Validation and Regulatory Acceptance of 
Toxicological Test Methods.'' National Institutes of Environmental 
Health Sciences, Research Triangle Park, NC 27709
    31. Jefferies, D.L., and J.L.F. Parslow (1976) ``Thyroid Changes in 
PCB-Dosed Guillemots and Their Indication of One of the M echanisms of 
Action For These Materials.'' Environmental Pollution, 10, pp. 293-311.
    32. Kelce, W.R., C. Stone, S. Laws, L.E. Gray, J. Kemppainen, and 
E. Wilson (1995) ``Persistent DDT metabolite p,p' DDE is a potent 
androgen receptor antagonist. Nature, 375(15), pp. 581-585.
    33. Kelce, W.R., C. Lambright, L.E. Gray Jr., and K. Roberts (1997) 
``Vinclozolin and p,p' DDE alter androgen-dependent gene expression: in 
vivo confirmation of an androgen receptor mediated mechanism.'' 
Toxicology and Applied Pharmacology, 142, pp. 192-200.
    34. Korenbrot, C.C., I. Huhtaniemi, and R. Weiner (1977) 
``Preputial separation ass an external sign of pubertal development in 
the male rat.'' Biology of Reproduction, 17, pp. 298-303.
    35. Kubiak, T.J., H.J. Harris, L.M. Smith, T.R. Schwartz, D.L. 
Stalling, J.A. Trick, L. Sileo, D. Docherty, and T.C. Erdman (1989) 
``Microcontaminants and Reproductive Impairment of the Forster's Tern 
on Green Bay, Lake Michigan --1983.'' Archives of Environmental 
Contamination and Toxicology, 18, pp. 706-727.
    36. Maguire, C.C., and B.A. Williams (1987) ``Response of Thermal 
Stressed Bobwhite to Organophosphorous Exposure.'' Environmental 
Pollution, 47, pp. 25-39.
    37. Martin, P.A. (1990) ``Effects of Carbofuran, Chlorpyrifos, and 
Deltamethrin on Hatchability, Deformity, Chick Size, and Incubation 
Time of Japanese Quail (Coturnix japonica) Eggs.'' Environmental 
Toxicology and Chemistry, 9, pp. 529-534.
    38. Martin, P. A., and K.R. Solomon (1991) ``Acute Carbofuran 
Exposure and Cold Stress: Interactive effects in Mallard Ducklings.'' 
Pesticide Biochemistry and Physiology, 40, pp. 117-127.
    39. McArthur, M.L.B., G.A. Fox, D.B. Peakall, and B.J.R. Philogene 
(1983) ``Ecological Significance of Behavioral and Hormonal 
Abnormalities in Bredding Ring Doves Fed an Organochlorine Chemical 
Mixture.'' Archives of Environmental Contamination and Toxicology, 12, 
pp. 343-353.
    40. McLachlan, J.A., R.R. Newbold, H.C. Shah, M.D. Hogan, and R.L. 
Dixon, ``Reduced fertility in female mice exposed transplacentally to 
diethylstilbestrol (DES).'' Fertility and Sterility, 38, 1982, pp. 364-
371.
    41. McNabb, F.M.A. (1988) ``Peripheral Thyroid Hormone Dynamics in 
Precocial and Altricial Avian Development.'' American Zoologist, 28, 
pp. 427-440.
    42. Moccia, R.D., G.A. Fox, and A. Britton (1986) ``A Quantitative 
Assessment of Thyroid Histopathology of Herring Gulls (Larus 
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    43. Nelson, K., T. Takahashi, N. Bossert, D. Walmer, and J. 
McLachlan (1991) ``Epidermal growth factor replaces estrogen in the 
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    44. O'Connor, J.C., et al. (1996) ``An in vivo battery for 
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``Enhancement of Parathion Toxicity to Quail by Heat and Cold 
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Responses and Tolerance to Cold of Female Quail following Parathion 
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    49. Raynaud, J.P. et al. (1984) The Prostate, 5, pp.299-311.
    50. Salamon, V.(1938) ``The effect of testosterone propionate on 
the genital tract of the immature female rat.'' Endocrinology, 23, 
pp.779-783.
    51. Shaban, M., and P. Terranova (1986) ``2-Bromo-I-ergocryptine 
mesylate (CB-154) inhibits prolactin and luteinizing hormone secretion 
in the prepubertal female rat.'' Biology of Reproduction, 34, pp. 788-
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Kubiak, P.D. Jones, D.A. Verbrugge, and R.J. Aulerich (1996) ``Effects 
Induced by Feeding Organochlorine-Contaminated Carp From Saginaw Bay, 
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[[Page 71568]]

Journal of Toxicology and Environmental Health, 49, pp. 409-438.
    53. Tori, G.M., and L.P. Mayer (1981) ``Effects of Polychlorinated 
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Toxicology, 27, pp. 678-682.

 IX. Public Record and Electronic Submissions

     The official record for this notice, as well as the public 
version, has been established for this notice under docket control 
number OPPTS-42208 (including comments and data submitted 
electronically as described in this unit). A public version of this 
record, including printed, paper versions of electronic comments, which 
does not include any information claimed as CBI, is available for 
inspection from 12 noon to 4 p.m., Monday through Friday, excluding 
legal holidays. The official record is located at the address in Unit 
I.B.3. of this notice.
     Electronic comments can be sent directly to EPA at:

    [email protected].

    Electronic comments must be submitted as an ASCII file avoiding the 
use of special characters and any form of encryption. Comment and data 
will alsobe accepted on disks in Wordperfect 5.1/6.1 or ASCII file 
format. All comments and data in electronic form must be identified by 
the docket control number OPPTS-42208. Electronic comments on this 
notice may be filed online at many Federal Depository Libraries.

 List of Subjects

    Environmental protection, Chemicals, Drinking water, Endocrine 
disruptors, Hazardous substances, Health and safety, Pesticides and 
pests.

    Authority: 21 U.S.C. 346a(p); 42 U.S.C. 300j-17; 7 U.S.C. 136a; 
15 U.S.C. 2604.

    Dated: December 21, 1998.
Lynn R. Goldman,
Assistant Administrator for Prevention, Pesticides and Toxic 
Substances.
[FR Doc. 98-34298 Filed 12-23-98; 9:49 am]
BILLING CODE 6560-50-F