Document ID: EPA-HQ-OPPT-2015-0305-0001
Agency: epa
Document Type: Notice
Title: Endocrine Disruptor Screening Program: Use of High Throughput Assays and Computational Tools
Posted Date: 2015-06-19T04:00Z

[Federal Register Volume 80, Number 118 (Friday, June 19, 2015)]
[Notices]
[Pages 35350-35355]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2015-15182]

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ENVIRONMENTAL PROTECTION AGENCY

[EPA-HQ-OPPT-2015-0305; FRL-9928-69]

Use of High Throughput Assays and Computational Tools; Endocrine 
Disruptor Screening Program; Notice of Availability and Opportunity for 
Comment

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice.

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SUMMARY: This document describes how EPA is planning to incorporate an 
alternative scientific approach to screen chemicals for their ability 
to interact with the endocrine system. This will improve the Agency's 
ability to fulfill its statutory mandate to screen pesticide chemicals 
and other substances for their ability to cause adverse effects by 
their interaction with the endocrine system. The approach incorporates 
validated high throughput assays and a computational model and, based 
on current research, can serve as an alternative for some of the 
current assays in the Endocrine Disruptor Screening Program (EDSP) Tier 
1 battery. EPA has partial screening results for over 1800 chemicals 
that have been evaluated using high throughput assays and a 
computational model for the estrogen receptor pathway. In the future, 
EPA anticipates that additional alternative methods will be available 
for EDSP chemical screening based on further advancements of high 
throughput assays and computational models for other endocrine 
pathways. Use of these alternative methods will accelerate the pace of 
screening, decrease costs, and reduce animal testing. In addition, this 
approach advances the goal of providing sensitive, specific, 
quantitative, and efficient screening using alternative test methods to 
some assays in the Tier 1 battery to protect human health and the 
environment.

DATES: Comments must be received on or before August 18, 2015.

ADDRESSES: Submit your comments, identified by docket identification 
(ID) number EPA-HQ-OPPT-2015-0305, by one of the following methods:
     Federal eRulemaking Portal: http://www.regulations.gov. 
Follow the online instructions for submitting comments. Do not submit 
electronically any information you consider to be Confidential Business 
Information (CBI) or other information whose disclosure is restricted 
by statute.
     Mail: Document Control Office (7407M), Office of Pollution 
Prevention and Toxics (OPPT), Environmental Protection Agency, 1200 
Pennsylvania Ave. NW., Washington, DC 20460-0001.
     Hand Delivery: To make special arrangements for hand 
delivery or delivery of boxed information, please follow the 
instructions at http://www.epa.gov/dockets/contacts.html.
    Additional instructions on commenting or visiting the docket, along 
with more information about dockets generally, is available at http://www.epa.gov/dockets.

FOR FURTHER INFORMATION CONTACT: For technical information contact: 
Jane Robbins, Office of Science Coordination and Policy (OSCP), Office 
of Chemical Safety and Pollution Prevention, Environmental Protection 
Agency, 1200 Pennsylvania Ave. NW., Washington, DC 20460-0001; 
telephone number: (202) 564-6625; email address: robbins.jane@epa.gov.
    For general information contact: The TSCA-Hotline, ABVI-Goodwill, 
422 South Clinton Ave., Rochester, NY 14620; telephone number: (202) 
554-1404; email address: TSCA-Hotline@epa.gov.

SUPPLEMENTARY INFORMATION:

I. General Information

A. Does this action apply to me?

    This action is directed to the public in general, and may be of 
interest to a wide range of stakeholders including those interested in 
endocrine testing of chemicals (including pesticides), and the EDSP in 
general. Since others also may be interested, the Agency has not 
attempted to describe all the specific entities that may be affected by 
this action.

B. What is the agency authority for taking this action?

    The EDSP is established under section 408(p) of the Federal Food, 
Drug and

[[Page 35351]]

Cosmetic Act (FFDCA), 21 U.S.C. 346a(p). Section 408(p)(1) 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 
effects as [EPA] may designate.'' [21 U.S.C. 346a(p)(1)]. Section 
408(p)(2) requires that the screening program be implemented ``after 
obtaining public comment and review . . . by the scientific advisory 
panel established under section 25(d) of the Federal Insecticide, 
Fungicide, and Rodenticide Act. . .'' [21 U.S.C. 346a(p)(2)].
    This document describes the new scientific methods that are 
available as alternatives to some of the current EDSP Tier 1 screening 
assays and solicits public comment on EPA's plan to use these 
alternative approaches to screen chemicals for their ability to 
interact with the endocrine system. The approach described in this 
document is not binding on either EPA or any outside parties, and EPA 
may depart from the approach presented in this document where 
circumstances warrant and without prior notice.

C. What action is the agency taking?

    This document describes and solicits comments on how EPA is 
planning to incorporate scientific advancements and tools into the 
EDSP. The adoption of scientific advancements into the EDSP has been 
underway and part of the public dialogue about EDSP for several years. 
As EPA has consistently indicated, the Agency intends to continue to 
incorporate in the EDSP new methods involving high throughput assays 
and computational toxicology. Also, EPA has identified a universe of 
approximately 10,000 chemicals as potential candidates for screening 
and testing under the EDSP (Ref. 1). This approach is expected to 
accelerate the pace of screening, add efficiencies, decrease costs, and 
reduce animal testing.
    EPA is planning to incorporate the partial screening results from 
validated high throughput assays and computational models as an 
alternative to data from some of the current assays in the EDSP Tier 1 
screening battery. Currently, EPA has partial screening results for 
over 1800 chemicals that have been evaluated using the high throughput 
assays and computational model for the estrogen receptor pathway.
    The use of high-throughput assays and computational models for EDSP 
screening is an initial step in EPA's integration of 21st-century 
integrated assessment and testing approaches broadly, beyond EDSP, 
across a wide range of chemicals related to regulatory and non-
regulatory decisions made in programs under the Agency's purview (Ref. 
2). Much of the knowledge gained in using these approaches for EDSP 
screening will be useful in applying high throughput assays and 
computational models to thousands of chemicals across many 
toxicological endpoints and exposure scenarios.

D. What should I consider as I prepare my Comments for EPA?

    1. Submitting CBI. Do not submit this information to EPA through 
regulations.gov or email. Clearly mark the part or all of the 
information that you claim to be CBI. For CBI information in a disk or 
CD-ROM that you mail to EPA, mark the outside of the disk or CD-ROM as 
CBI and then identify electronically within the disk or CD-ROM the 
specific information that is claimed as CBI. In addition to one 
complete version of the comment that includes information claimed as 
CBI, a copy of the comment that does not contain the information 
claimed as CBI must be submitted for inclusion in the public docket. 
Information so marked will not be disclosed except in accordance with 
procedures set forth in 40 CFR part 2.
    2. Tips for preparing your comments. When preparing and submitting 
your comments, see the commenting tips at http://www.epa.gov/dockets/comments.html.

II. Background

A. What is the Endocrine Disruptor Screening Program (EDSP)?

    The Food Quality Protection Act (FQPA) of 1996 amended FFDCA to 
require 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 effects as [EPA] may designate'' (21 U.S.C. 
346a(p)(1)). Also in 1996, the Agency chartered the Endocrine Disruptor 
Screening and Testing Advisory Committee (EDSTAC), under the provisions 
of the Federal Advisory Committee Act (FACA) (5 U.S.C. App. 2, section 
9(c)), to provide advice on developing an endocrine disruptor screening 
program (Ref. 3). 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. EDSTAC recommended that 
EPA's program address both potential human and wildlife effects; 
examine effects on estrogen, androgen, and thyroid hormone-related 
processes; and include non-pesticide chemicals, contaminants, and 
mixtures in addition to pesticide chemicals (Ref. 2).
    In 1998, based on the EDSTAC recommendations, EPA established the 
EDSP using a two-tiered approach (Ref. 4). The purpose of Tier 1 
(referred to as ``screening'') is to identify substances that have 
potential biological activity (``bioactivity'') in the estrogen, 
androgen, or thyroid hormone pathways using a battery of assays. The 
purpose of Tier 2 (referred to as ``testing'') is to identify and 
establish a dose-response relationship for any adverse effects that 
might result from the endocrine bioactivity identified through the Tier 
1 assays. The ultimate purpose of the EDSP is to provide information to 
the Agency that will allow the Agency to evaluate any possible 
endocrine effects associated with the use of a chemical and take 
appropriate steps to mitigate any related risks to ensure protection of 
public health.
    In 2009, the Agency issued test orders requiring Tier 1 screening 
for 67 chemicals (``List 1'') (Ref. 5). Between the time needed to 
review the substantial volume of ``other scientifically relevant 
information'' submitted by test order recipients to satisfy selected 
screening assays, the time and resources of industry spent generating 
data, the time spent by the Agency reviewing the information, and the 
delays resulting from the limited laboratory capacity for conducting 
many of the Tier 1 assays and corresponding time extension requests, 
the review of the initial List 1 chemicals has taken over four years 
and has imposed significant burdens on test order recipients and the 
agency. The Agency is still finalizing the data evaluation records and 
determinations concerning which of the List 1 chemicals need further 
Tier 2 testing. More information on the EDSP history and the status of 
current activities is available at http://www.epa.gov/endo.

B. What is meant by ``high throughput assays and computational model''?

    High throughput assays are automated methods that allow for a large 
number of chemicals to be rapidly evaluated for a specific type of 
bioactivity at the molecular or cellular level. This approach, which 
can help identify compounds that may modulate specific

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biological pathways, was initially developed by pharmaceutical 
companies for drug discovery. The results of these methods provide an 
initial understanding of a biochemical interaction or possible role of 
a chemical in a given biological process. In vitro high throughput 
assays are usually conducted using a microtiter plate: a plate 
containing a grid with a large number of small divots called ``wells.'' 
The wells contain chemical and/or biological substrate (e.g., living 
cells or proteins). Depending on the nature of the experiment, changes 
can be detected (e.g., color, fluorescence, etc.) when the chemical is 
added to indicate whether there is bioactivity. High throughput 
microtiter plates typically come in multiples of 96 wells (96, 384, or 
1536), so that through the use of robotics, data processing and control 
software, liquid handling devices, and sensitive detection methods, an 
extremely large number of chemicals can be evaluated very efficiently.
    High throughput assays can be run for a range of test chemical 
concentrations and produce concentration-response information 
representing the relationship between chemical concentration and 
bioactivity. The concentration-response data from multiple assays can 
be mathematically integrated in a computational model of a biological 
pathway, providing values representative of a chemical's bioactivity in 
that pathway (e.g., estrogen receptor pathway). To reduce non-specific 
results, the computational model can use results from multiple assays 
and technologies to predict whether a chemical is truly bioactive in 
the pathway being evaluated. The most prominent cause of non-specific 
results (activity in an assay that is likely not due to bioactivity of 
the chemical in the pathways) is cytotoxicity in cell-based assays. In 
other cases, chemicals influence the assays through a manner dependent 
on the physics and chemistry of the technology platform (i.e., ``assay 
interference'').

C. What is ToxCast\TM\?

    To improve efficiencies in screening and testing chemicals, EPA 
scientists are harnessing advances in molecular and systems biology, 
chemistry, toxicology, mathematics, and computer technology. In doing 
this, they are helping to revolutionize chemical screening and safety 
testing based on advances in computational toxicology. A major part of 
this effort is the Agency's Toxicity Forecaster, or ToxCast\TM\, which 
uses automated, robotics-assisted high throughput assays to expose 
living cells or proteins to chemicals and measure the results. The high 
throughput assays produce concentration-response information 
representing the relationship between chemical concentration and 
bioactivity. These innovative methods have the potential to quickly and 
efficiently screen large numbers of chemicals and other substances. 
ToxCast\TM\ is part of EPA's contribution to a federal research 
collaboration called ``Toxicity Testing in the 21st Century'', or 
``Tox21,'' pooling resources and expertise from EPA, the National 
Institutes of Health and the U.S. Food and Drug Administration to use 
robotics for screening thousands of chemicals for potential bioactivity 
(Ref. 6).
    As part of EPA's commitment to gather and share its chemical data 
openly and clearly, all ToxCast\TM\ chemical data are publicly 
available through user-friendly web applications called the interactive 
Chemical Safety for Sustainability (iCSS) and EDSP21 dashboards (Refs. 
7 and 8). The EDSP21 and iCSS dashboards provide accessible portals for 
users to search and query the ToxCast\TM\ chemical data. Users can 
review chemicals and data of interest, as well as export the 
information. Making ToxCast\TM\ data available through the dashboards 
creates an environment that encourages external stakeholder 
interactions identifying potential issues, concerns, and suggesting 
improvements.

D. What is meant by the ToxCast\TM\ ER Model for bioactivity?

    The ToxCast\TM\ ER Model for bioactivity (``ER Model'') includes 
data from 18 estrogen receptor (ER) high throughput assays from 
ToxCast\TM\ that detect multiple events in the receptor pathway. The ER 
Model also includes a computational module that integrates the assay 
data to produce a value for ER agonist and antagonist bioactivity for 
each chemical (Ref. 9). An ER agonist binds and activates the receptor, 
and an antagonist binds and blocks activation. These 18 high throughput 
assays measure bioactivity at different sites along the ER pathway 
including receptor binding, receptor dimerization, chromatin binding of 
the mature transcription factor, gene transcription and changes in 
estrogen-receptor growth kinetics. Bioactivity (i.e., response) is 
measured using various detection methods (e.g., fluorescence, etc.) 
across a range of concentrations to examine potential concentration-
response relationships, including no change across concentrations 
indicating no bioactivity. Concentration-response relationships for 
each assay are mathematically integrated in the ``ER Model'' to 
quantify bioactivity from multiple assays. The computational model 
integrates the results of each of the 18 ER assays as an area under the 
curve (AUC) for ER agonist or antagonist bioactivity for each chemical. 
The bioactivity values generally range from 0 to 1 for each chemical, 
with 0 indicating no bioactivity and 1 approximating the positive 
reference chemical (e.g., estradiol for ER agonism).
    In order to validate the ER Model, ToxCast\TM\ data have been 
collected and reviewed on over 1800 chemicals, including ER reference 
agonists and antagonists (Ref. 10). ER agonist and antagonist 
bioactivity scores from the ``ER Model'' compare very well with 
reported bioactivity of reference chemicals across a range of 
structures and potencies. Of the over 1800 chemicals tested, over 1700 
chemicals had very low or no detectable ER bioactivity (Ref. 10). The 
``ER Model'' bioactivity scores were validated by comparing the scores 
to 45 reference chemicals, equivalent to a performance-based approach 
to validation. EPA also compared ``ER Model'' results to a database of 
curated uterotrophic studies published in peer-reviewed literature. ER 
agonist bioactivity scores accurately predicted in vivo ER agonist 
activity for a large set (~150) of chemicals with uterotrophic data 
(Refs. 9 and 11). The validation of the ``ER Model'' as an alternative 
screening method for three current Tier 1 assays (ER binding, ER 
transcriptional activation (ERTA), and uterotrophic) was peer reviewed 
by the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) 
Scientific Advisory Panel (SAP) in December 2014 (Refs. 9 and 11). The 
FIFRA SAP fully endorsed the use of these alternatives for the ER 
binding and ERTA assays; however, there was not consensus among panel 
members on the use of the ``ER Model'' as an alternative for the 
uterotrophic assay (Ref. 11). In response to the concerns raised by the 
FIFRA SAP, EPA has published a paper clarifying the relationship 
between ``ER Model'' bioactivity and uterotrophic results, and 
illustrating that a uterotrophic assay would provide no added value if 
``ER Model'' data are available (Ref. 12). Based on these findings, EPA 
concludes that ``ER Model'' data are sufficient to satisfy the Tier 1 
ER binding, ERTA and uterotrophic assay requirements. The Agency 
intends to build on the performance-based validation approach presented 
at the December 2014 FIFRA SAP expanding this approach to include

[[Page 35353]]

other key events in the estrogen pathway.

III. Using High Throughput Assays and Computational Models for 
Screening

A. How Will ToxCast\TM\ data be used for screening in the EDSP?

    The ability to screen chemicals rapidly for bioactivity in several 
endocrine pathways, and reducing the use of animals in testing, have 
been EDSP goals since 1998, when the program was first adopted (Ref. 
4). As previously noted, when the first Tier 1 orders (for List 1 
chemicals) were issued in 2009, EPA had not confirmed the reliability 
and relevance of the ToxCast\TM\ results so that they could be cited as 
``other scientifically relevant information'' to satisfy the Tier 1 ER 
binding, ERTA, and uterotrophic assays (Ref. 13). However, since that 
time, EPA has reached a critical juncture, determining that the science 
has progressed such that reevaluation of EPA's earlier position is 
warranted. Based on scientific advances, EPA intends to implement the 
use of high throughput assays and computational models to evaluate, and 
to a significant extent, screen chemicals. The in vitro high throughput 
and computational model alternatives provide an accurate quantitative 
measure of specific endocrine pathway bioactivity and mechanisms. The 
current Tier 1 battery includes animal-based assays that do not clearly 
identify or differentiate pathways and mechanisms. Specifically, the 
current Tier 1 ER binding, ERTA and uterotrophic assays do not provide 
both estrogen agonist and antagonist activity and animals are required 
to conduct the ER binding and uterotrophic assays.
    EPA is planning to adopt in vitro high throughput assays and 
computational models for detecting and measuring ER agonist and 
antagonist bioactivity as an alternative for three current Tier 1 
assays: 1) ER binding in vitro assay (Ref. 14); 2) ER transcriptional 
activation in vitro assay (ERTA) (Ref. 15); and 3) in vivo uterotrophic 
assay (Refs. 16 and 17). EPA is also planning to accept existing 
results for chemicals that have been evaluated using the ToxCast\TM\ 
``ER Model'' for bioactivity. The accompanying database contains the ER 
agonist bioactivity and ER antagonist bioactivity for over 1800 
chemicals and identifies those chemicals that are pesticide active 
ingredients, pesticide inert ingredients, and on EDSP Lists 1 or 2 
(Ref. 10). This is a ``living'' database that will continue to 
incorporate bioactivity results for chemicals as they become available. 
This database is available at http://www.epa.gov/endo and in the docket 
identified for this document in a format that can be easily reviewed 
and manipulated electronically (Ref. 10). It is important, however, not 
to equate a determination of a chemical's bioactivity from the ``ER 
Model'' with a determination that a chemical causes endocrine 
disruption. The World Health Organization (WHO)/International Programme 
on Chemical Safety (IPCS) defines endocrine disruption as being caused 
by ``an exogenous substance or mixture that alters function(s) of the 
endocrine system . . . and . . .consequently causes adverse health 
effects in an intact organism or its progeny, or (sub)populations'' 
(Ref. 18). Bioactivity is an indicator that a chemical has the 
potential to alter endocrine function, but (1) whether the chemical 
actually alters endocrine function and (2) whether that altered 
function produces an adverse outcome in an intact animal cannot be 
determined without further testing (i.e., Tier 2 testing).
    The EDSP has been developed over the past 19 years, and has 
demonstrated that the current screening process may take upwards of 5 
years before a Tier 1 decision is available or Tier 2 test orders are 
issued. In light of recent advances in high throughput assays and 
computational models, and advances likely to come in the next two 
years, it is prudent for the Agency to consider new, rapid screening 
methods. The availability of additional alternative high throughput 
assays and computational models in the near term will allow EPA to 
screen more chemicals in less time, involve fewer animals, and cost 
less for everyone. Furthermore, reconsideration of the EDSP List 2 
chemicals may be appropriate since ``ER Model'' data are available for 
many List 2 and other chemicals (Refs. 10 and 19). Ongoing use of high 
throughput assays and computational models will address thousands of 
chemicals in the future.
    These advancements in the EDSP screening program will not affect 
the overall framework--i.e., the Tier 1 screening battery and Tier 2 
testing approach focused on estrogen, androgen and thyroid pathways in 
humans and wildlife remains unaffected. Instead, as discussed above, 
EPA is planning to adopt sensitive, specific, quantitative, and 
efficient screening methods that will rapidly screen many chemicals and 
substantially decrease costs and animal use and may be used as an 
alternative to some EDSP Tier 1 screening assays. Accordingly, EPA 
intends a future recipient of an EDSP test order to be able to satisfy 
the screening requirement for ER, ERTA, and uterotrophic in one of 
three ways: (1) cite existing ToxCast\TM\ ``ER Model'' for bioactivity 
data as ``other scientifically relevant information'' (where 
available); (2) generate new data relying on the 18 ER high throughput 
assays and the ToxCast\TM\ ``ER Model'' for bioactivity; or (3) 
generate their own data using the current Tier 1 ER binding, ERTA, and 
uterotrophic assays.

B. How Does EPA intend to use high throughput assays and computational 
models for the EDSP in the future?

    EPA believes that ongoing adoption of alternative methods and 
technologies will continue to advance EDSP screening of chemicals for 
bioactivity in the estrogen, androgen, and thyroid pathways. EPA is 
continuing research on the ``ER Model'' to determine if ToxCast\TM\ 
assays can provide comparable information as that of the Female Rat 
Pubertal and the Fish Short Term Reproduction assays. In addition, 
research continues on the ToxCast\TM\ ``AR Model'' for bioactivity 
which, if fully validated, may be considered as an alternative (alone 
or with the ``ER Model'') for the following current Tier 1 assays: AR 
binding, Male Rat Pubertal, Hershberger, and Fish Short Term 
Reproduction. Research is also underway to develop steroidogenesis 
ToxCast\TM\ (STR) and thyroid (THY) bioactivity models. Over time, the 
Agency's goal is to develop a set of ``non-animal'' high throughput 
assays and computational bioactivity models as an alternative to all of 
the assays in the current Tier 1 screening battery. The following table 
is intended to illustrate the evolution of screening in the EDSP:

------------------------------------------------------------------------
                                           Alternative high throughput
 Current EDSP Tier 1 battery of assays    assays and computational model
                                             for EDSP Tier 1 battery
------------------------------------------------------------------------
Estrogen Receptor (ER) Binding.........  ER Model (alternative).
Estrogen Receptor Transactivation        ER Model (alternative).
 (ERTA).
Uterotrophic...........................  ER Model (alternative).
Female Rat Pubertal....................  ER, STR , and thyroid (THY)
                                          Models (Future).

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Male Rat Pubertal......................  AR, STR, and THY Models
                                          (Future).
Androgen Receptor (AR) Binding.........  AR Model (Future).
Hershberger............................  AR Model (Future).
Aromatase..............................  STR Model (Future).
Steroidogenesis (STR)..................  STR Model (Future).
Fish Short Term Reproduction...........  ER, AR, and STR Models
                                          (Future).
Amphibian Metamorphosis................  THY Model (Future).
------------------------------------------------------------------------

    The table indicates combinations of various alternative assays and 
models that might overlap for evaluating potential endocrine 
bioactivity of chemicals. The in vitro high throughput and 
computational model alternatives provide a focused evaluation of the 
mechanistic aspects of endocrine pathways, thereby providing specific 
and quantitative measures of bioactivity. Several assays in the Tier 1 
battery rely on intact animals and identify bioactivity in the multiple 
biological pathways present. For this reason, the specificity of the in 
vitro high throughput and computational model alternatives may be more 
informative of specific endocrine pathway bioactivity.
    The annual EDSP Comprehensive Management Plan and future FIFRA SAP 
meetings are opportunities for staying informed on EPA's scientific 
progress on the evolution of Tier 1 screening in the EDSP. For 
information, visit EPA's Web site (http://www.epa.gov/endo) or sign-up 
to receive announcements go to (http://www.epa.gov/endo/pubs/assayvalidation/listserv.htm).

IV. Issues for Comment

    In connection with EPA's stated intention to use the scientific 
tools discussed in this Notice as alternatives to some of the current 
EDSP Tier 1 screening assays, EPA is specifically seeking public 
comment on the following:
    1. The use of the ToxCast\TM\ ``ER Model'' for bioactivity as an 
alternative method for the current ER binding and ERTA Tier 1 screening 
assays.
    2. The use of the ToxCast\TM\ ``ER Model'' for bioactivity as an 
alternative method for the current uterotrophic Tier 1 screening assay.
    3. The use of results from the ToxCast\TM\ ``ER Model'' for 
bioactivity on over 1800 chemicals as partial screening for the 
estrogen receptor pathway.

V. References

    The following is a listing of the documents that are specifically 
referenced in this document. The docket includes these documents and 
other information considered by EPA, including documents that are 
referenced within the documents that are included in the docket, even 
if the referenced document is not physically located in the docket. For 
assistance in locating these other documents, please consult the 
technical person listed under FOR FURTHER INFORMATION CONTACT.

1. U.S. EPA. Endocrine Disruptor Screening Program; Universe of 
Chemicals and General Validation Principles. November 2012. 
Available at http://www.epa.gov/endo/pubs/edsp_chemical_universe_and_general_validations_white_paper_11_12.pdf.

2. U.S. EPA. Endocrine Disruptor Screening Program for the 21st 
Century: (EDSP21 Work Plan); The Incorporation of In Silico Models 
and In Vitro High Throughput Assays in the Endocrine Disruptor 
Screening Program (EDSP) for Prioritization and Screening; Summary 
Overview. A Part of the EDSP Comprehensive Management Plan. 
September 30, 2011. Available at http://www.epa.gov/endo/pubs/edsp21_work_plan_summary%20_overview_final.pdf.
3. U.S. EPA. Endocrine Disruptor Screening and Testing Advisory 
Committee (EDSTAC); Final Report. August 1998. Available at http://www.epa.gov/endo/pubs/edspoverview/finalrpt.htm.
4. U.S. EPA. Endocrine Disruptor Screening Program; Proposed 
Statement of Policy; Notice. Federal Register (63 FR 71542, December 
28, 1998) (FRL-6052-9).
5. U.S. EPA. Endocrine Disruptor Screening Program; Tier 1 Screening 
Order Issuance Announcement; Notice. Federal Register (74 FR 54422, 
October 21, 2009) (FRL-8434-8).
6. U.S. EPA. Office of Research and Development (ORD); Description 
of Computational Toxicology Research Program. Available at http://epa.gov/ncct.
7. U.S. EPA. Interactive Chemical Safety for Sustainability (iCSS) 
Dashboard, Version 0.5. Available at http://actor.epa.gov/dashboard.
8. U.S. EPA. EDSP21 Dashboard. Available at http://actor.epa.gov/edsp21.
9. U.S. EPA. Integrated Bioactivity and Exposure Ranking: A 
Computational Approach for the Prioritization and Screening of 
Chemicals in the Endocrine Disruptor Screening Program. December 
2014. Docket ID No. EPA-HQ-OPP-2014-0614-0003. Available at http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2014-0614-0003.
10. U.S. EPA. Endocrine Disruptor Screening Program (EDSP); Estrogen 
Receptor Bioactivity Based on ToxCa \TM\ ``ER Model.'' June 1, 2015. 
Available at http://www.epa.gov/endo.
11. U.S. EPA. FIFRA SAP Minutes No. 2015-01. FIFRA SAP Meeting on 
the Integrated Bioactivity and Exposure-Based Prioritization and 
Screening, held December 2-4, 2014. Docket ID No. EPA-HQ-OPP-2014-
0614-0029. March 2, 2015. Available at http://www.epa.gov/scipoly/sap/meetings/2014/december/120214minutes.pdf.
12. Browne, P., Judson, R.S., Casey, W., Kleinstreuer, N., Thomas, 
R.S. Screening Chemicals For Estrogen Receptor Bioactivity Using A 
Computational Model. Manuscript accepted for publication. Environ. 
Sci. Technol. June 12, 2015. Available in the docket and 
electronically at http://pubs.acs.org/journal/esthag.
13. U.S. EPA. Endocrine Disruptor Screening Program; Policies and 
Procedures for Initial Screening; Notice. Federal Register (74 FR 
17560, April 15, 2009) (FRL-8399-9). Note: the status and progress 
of all List 1 Tier 1 orders are available at http://www.epa.gov/endo/pubs/toresources/index.htm.
14. U.S. EPA. Endocrine Disruptor Screening Program Test Guidelines; 
OPPTS 890.1250: Estrogen Receptor Binding Assay Using Rat Uterine 
Cytosol (ER-RUC). October 2009. EPA 740-C-09-005. Available at 
http://www.epa.gov/ocspp/pubs/frs/publications/Test_Guidelines/series890.htm.
15.U.S.EPA. Endocrine Disruptor Screening Program Test Guidelines; 
OPPTS 890.1300: Estrogen Receptor Transcriptional Activation (Human 
Cell Line (HeLa-9903)). October 2009. EPA 740-C-09-006. Available at 
http://www.epa.gov/ocspp/pubs/frs/publications/Test_Guidelines/series890.htm.
16.U.S.EPA. Endocrine Disruptor Screening Program Test Guidelines; 
OPPTS 890.1600: Uterotrophic Assay. October 2009. EPA 740-C-09-0010. 
Available at http://www.epa.gov/ocspp/pubs/frs/publications/Test_Guidelines/series890.htm.
17. Organization of Economic Co-operation and Development (OECD). 
Test Guideline No. 440:Uterotrophic Bioassay in Rodents: A short-
term screening test for oestrogenic properties. OECD Guidelines for 
the Testing of Chemicals, Section 4, OECD Publishing, Paris. DOI: 
http://dx.doi.org/10.1787/

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9789264067417-en.
18. World Health Organization (WHO)/International Programme on 
Chemical Safety (IPCS). Global Assessment of the State-of-the-
Science of Endocrine Disruptors. WHO/IPCS/EDC/02.2. 2002. Available 
at http://www.who.int/ipcs/publications/new_issues/endocrine_disruptors/en.
19. U.S. EPA. Endocrine Disruptor Screening Program; Final Second 
List of Chemicals and Substances for Tier 1 Screening; Notice. 
Federal Register (78 FR 35922, June 14, 2013) (FRL-9375-8). 
Available at http://www.gpo.gov/fdsys/pkg/FR-2013-06-14/pdf/2013-14232.pdf.

    Authority:  21 U.S.C. 346a(p).

    Dated: June 11, 2015.
James J. Jones,
Assistant Administrator, Office of Chemical Safety and Pollution 
Prevention.
[FR Doc. 2015-15182 Filed 6-18-15; 8:45 am]
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