`[Federal Register Volume 89, Number 232 (Tuesday, December 3, 2024)]
[Notices]
[Pages 95779-95782]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-28286]


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ENVIRONMENTAL PROTECTION AGENCY

[EPA-HQ-OPPT-2024-0425; FRL-12241-02-OCSPP]


1,3-Butadiene; Draft Risk Evaluation Under the Toxic Substances 
Control Act (TSCA); Science Advisory Committee on Chemicals (SACC) Peer 
Review; Notice of SACC Meeting, Availability of Draft Documents and 
Request for Comment

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice.

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SUMMARY: The Environmental Protection Agency (EPA or Agency) is 
announcing the availability of and soliciting public comment on the 
draft risk evaluation for 1,3-butadiene. The draft risk evaluation was 
prepared under the Toxic Substances Control Act (TSCA) and will be 
submitted to the Science Advisory Committee on Chemicals (SACC) for 
peer review. EPA is also announcing that there will be two virtual 
public meetings of the SACC: On February 4, 2025, a preparatory meeting 
for the SACC to consider the scope and clarity of the draft charge 
questions for the peer review; and on February 25 through 28, 2025, the 
peer review meeting for the SACC to consider the draft documents and 
public comments.

DATES: 
    Preparatory Public Meeting:
    Meeting date: February 4, 2025, 1:00 p.m. to approximately 4:00 
p.m. (ET).
    Registration: To request time to present oral comments during the 
preparatory meeting, you must register by noon (12:00 p.m. ET) on 
January 31, 2025. For those not making oral comments, registration will 
remain open through the end of this meeting on February 4, 2025.
    Comments: Submit written comments on the scope and clarity of the 
charge questions, by noon (12:00 p.m. ET) on January 28, 2025. (Submit 
a written version of your oral comments by noon (12:00 p.m. ET) on 
January 31, 2025.)
    SACC Peer Review Public Meeting:
    Meeting dates: February 25 through 28, 2025, 10:00 a.m. to 
approximately 5:00 p.m. (ET).
    Registration: To request time to present oral comments during the 
peer review meeting, you must register by noon, February 18, 2025. For 
those not making oral comments, registration will remain open through 
the end of this meeting on February 28, 2025.
    Comments: Submit written comments on the draft documents, and 
written version of your oral comments, on or before February 3, 2025.
    Special Accommodations: To allow sufficient time for EPA to process 
your request for special accommodations before the meeting, please 
submit the request at least ten business days in advance of the 
relevant meeting.

ADDRESSES: 
    Comments: Submit written comments, identified by docket 
identification (ID) number EPA-HQ-OPPT-2024-0425, through https://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. Additional information on 
commenting or visiting the docket, along with more information about 
dockets generally, is available at https://www.epa.gov/.
    Meeting Registration: Online registration will be available 
beginning in January 2025. Please refer to the SACC website at https://www.epa.gov/tsca-peer-review. After registering, you will receive the 
webcast and streaming service meeting links and audio teleconference 
information.
    Special accommodation requests: To request an accommodation for a 
disability, please contact the Designated Federal Official (DFO) listed 
under FOR FURTHER INFORMATION CONTACT.

FOR FURTHER INFORMATION CONTACT: 
    Designated Federal Official (DFO): Alie Muneer, Mission Support 
Division (7602M), Office of Program Support, Office of Chemical Safety 
and Pollution Prevention, Environmental Protection Agency; telephone 
number: (202) 564-

[[Page 95780]]

6369 or call the main office number: (202) 564-8450; email address: 
[email protected].
    Technical information: Brooke Porter, Existing Chemicals Risk 
Management Division, Office of Pollution Prevention and Toxics, Office 
of Chemical Safety and Pollution Prevention, Environmental Protection 
Agency; telephone number: (202) 564-6388; email address: 
[email protected].

SUPPLEMENTARY INFORMATION:

I. Executive Summary

A. What action is the Agency taking?

    EPA is announcing the availability of and soliciting public comment 
on the draft risk evaluation for 1,3-butadiene. The draft risk 
evaluation was prepared under the Toxic Substances Control Act (TSCA) 
and will be submitted to the Science Advisory Committee on Chemicals 
(SACC) for peer review. EPA is also announcing that there will be two 
virtual public meetings of the SACC: On February 4, 2025, a preparatory 
meeting for the SACC to consider the scope and clarity of the draft 
charge questions for the peer review; and on February 25 through 28, 
2025, the peer review meeting for the SACC to consider the draft risk 
evaluation and public comments.
    This document provides instructions for accessing the materials, 
submitting written comments, and registering to provide oral comments 
and attend the public meetings.

B. What is the Agency's authority for taking this action?

    EPA established the SACC in 2016 in accordance with TSCA, 15 U.S.C. 
2625(o), to provide independent advice and expert consultation with 
respect to the scientific and technical aspects of issues relating to 
the implementation of TSCA. The SACC operates in accordance with the 
Federal Advisory Committee Act (FACA), 5 U.S.C. 10, and supports 
activities under TSCA, 15 U.S.C. 2601 et seq., the Pollution Prevention 
Act (PPA), 42 U.S.C. 13101 et seq., and other applicable statutes.

C. Does this action apply to me?

    This action is directed to the public in general and may be of 
particular interest to those involved in the manufacture, processing, 
distribution, and disposal of the subject chemical substances, and/or 
those interested in the assessment of risks involving chemical 
substances and mixtures regulated under TSCA (including members of at-
risk communities, non-governmental organizations (NGOs), federal, 
state, and local officials). Since other entities may also be 
interested, the Agency has not attempted to describe all the specific 
entities that may be interested.

D. What should I consider as I submit my comments to EPA?

    1. Submitting CBI. Do not submit CBI or other sensitive information 
to EPA through https://www.regulations.gov or email. To include 
information in your comment that you consider to be CBI or otherwise 
protected, please contact the DFO listed under FOR FURTHER INFORMATION 
CONTACT to obtain special instructions before submitting that 
information.
    2. Tips for preparing comments. When preparing and submitting your 
comments, see https://www.epa.gov/dockets/commenting-epa-dockets. See 
also the instructions in Unit III.C.

E. How can I stay informed about SACC activities?

    You may subscribe to the following listserv for alerts regarding 
this and other SACC-related activities: https://public.govdelivery.com/accounts/USAEPAOPPT/subscriber/new?topic_id=USAEPAOPPT_101.

II. Background

A. What is the purpose of the SACC?

    The SACC provides independent advice and recommendations to the EPA 
on the scientific and technical aspects of risk assessments, 
methodologies, and pollution prevention measures and approaches for 
chemicals regulated under TSCA. The SACC is composed of experts in 
toxicology; environmental risk assessment; exposure assessment; and 
related sciences (e.g., synthetic biology, pharmacology, biotechnology, 
nanotechnology, biochemistry, biostatistics, physiologically based 
pharmacokinetic (PBPK) modeling, computational toxicology, 
epidemiology, environmental fate, and environmental engineering and 
sustainability). When needed, the SACC committee will be assisted by ad 
hoc reviewers with specific expertise in the topics under 
consideration.

B. Why is EPA conducting these risk evaluations?

    TSCA requires EPA to conduct risk evaluations on prioritized 
chemical substances and allows chemical manufacturers to request an 
EPA-conducted risk evaluation of a chemical substance (or category of 
chemical substances) using the procedures established in 40 CFR 702.37. 
TSCA also identifies the minimum components EPA must include in all 
chemical substance risk evaluations. The purpose of conducting risk 
evaluations is to determine whether a chemical substance presents an 
unreasonable risk to human health or the environment under the 
Conditions of Use (COUs). These evaluations include assessing 
unreasonable risks to relevant potentially exposed or susceptible 
subpopulations. As part of this process EPA: (1) Integrates hazard and 
exposure assessments using the best available science that is 
reasonably available to ensure decisions are based on the weight of the 
scientific evidence, and (2) Conducts peer review for risk evaluation 
approaches that have not been previously peer-reviewed.
    For more information about the TSCA risk evaluation process for 
existing chemicals, go to https://www.epa.gov/assessing-and-managing-chemicals-under-tsca.

C. Why is EPA evaluating this chemical substance?

    In 2020, EPA issued final scope documents for the 20 chemical 
substances designated in December 2019 as High-Priority Substances for 
the TSCA risk evaluation process, which included 1,3-butadiene. The 
final scope documents outline the hazards, exposures, conditions of 
use, and the potentially exposed or susceptible subpopulations the 
Agency expected to consider in its risk evaluation for the substances 
(85 FR 55283, September 4, 2020 (FRL-10013-90)).
    1,3-Butadiene (CASRN 106-99-0) is a volatile, colorless gas with a 
total U.S. production volume between 1 and 5 billion pounds. It is 
produced in petrochemical processing and extracted and further 
processed as a building block for several polymers and elastomers that 
do not readily depolymerize. Air is expected to be the major pathway of 
exposure for 1,3-butadiene in the environment. Although 1,3-butadiene 
is moderately soluble in water, monitoring data indicate that it is not 
detected in water. Environmental release data show that more than 98 
percent of 1,3-butadiene facility releases are to air. Once in air, 
1,3-butadiene will not deposit to land or adsorb to organic matter due 
to its chemical properties. Long-range transport in air is not 
expected, in part, because 1,3-butadiene has a short half-life (<8 
hours) and will degrade into formaldehyde and acrolein.
    Reduced fetal body weight and hematological effects are indicated 
as the most sensitive and robust non-cancer human health hazards. EPA 
has classified 1,3-butadiene as a human carcinogen and epidemiology 
studies have demonstrated an association between 1,3-butadiene exposure 
and

[[Page 95781]]

increased incidence of leukemia in workers.

D. What is the topic of the planned SACC peer review?

    EPA is submitting the draft risk evaluation of 1,3-butadiene and 
associated supporting documents to the SACC for peer review, along with 
the public comments received. The draft risk evaluation includes 
analyses of physical chemical properties, the fate and transport in the 
environment, releases to the environment, exposure to workers and the 
general population, including potentially exposed susceptible 
subpopulations, environmental risk characterization, and human health 
hazard and risk characterization for workers and the general 
population.
    EPA is focusing its peer review charge on specific scientific areas 
and analyses. Many of the methods and analyses used in these 
evaluations are not novel and have been reviewed in the development of 
previous TSCA assessments. EPA is requesting feedback on approaches, 
results and calculations associated with the exposure, human health 
hazard, and environmental hazard analyses. EPA is releasing the draft 
risk evaluation for public comment and independent, expert peer review. 
Once EPA receives comment and input from public comment and peer 
review, revisions will be made, and the Agency will finalize the 1,3-
butadiene risk evaluation.
    EPA is requesting a focused panel discussion and feedback on novel 
approaches, unique exposure analyses and other calculations, and 
selection of key hazard endpoints for 1,3-butadiene:
     No exposure to aquatic and terrestrial species is expected 
due to the physical and chemical properties of 1,3-butadiene, which is 
primarily released to air and does not partition, deposit, or persist 
in or on water or soil. Monitoring data indicate that 1,3-butadiene is 
not detected in water. Exposure of terrestrial organisms via ambient 
air will be brief due to the reactive nature of 1,3-butadiene. EPA is 
seeking comment on the preliminary determination that quantitative risk 
assessment for ecological taxa is not needed for 1,3-butadiene.
     Reduced fetal body weight (the basis of the acute 
Reference Concentration (RfC) in the 2002 IRIS Assessment) is observed 
in both mice and rats following gestational exposure but is not 
expected to result from a single dose of 1,3-butadiene. Further, EPA 
did not identfy effects of teratogenicity or any other relevant 
endpoint following single exposures at doses relevant to human exposure 
scenarios. Therefore, EPA did not derive an acute point of departure 
(POD) or quantify risks from acute exposures. EPA is seeking comment on 
the preliminary determination that there is no appropriate POD to 
support acute risk estimates.
     Ovarian atrophy is an adverse effect observed only in mice 
and can be attributed to a specific 1,3-butadiene metabolite 
(diepoxybutane) that is less prevalent in rats and humans. EPA has 
evaluated the relevance of ovarian atrophy for assessing human risk and 
determined that the ovarian atrophy endpoint is not appropriate for 
extrapolating to human risk due to differences in species-specific 
metabolites. EPA is proposing to use decreased fetal body weight as the 
basis for the intermediate and chronic points of departure for 1,3-
butadiene. EPA is seeking comment on these preliminary conclusions to 
establish intermediate and chronic points of departure based on reduced 
fetal body weight.
     OPPT revised the inhalation unit risk (IUR) for 1,3-
butadiene presented in the IRIS 2002 assessment to incorporate updated 
epidemiological cohort data. EPA is seeking comment on the mathematical 
approach and new epidemiological cohort data used in the revised IUR. 
OPPT also derived bladder cancer risk estimates using the same 
epidemiological cohort and is seeking comment on the appropriate IUR 
for evaluating cancer risk.
     EPA has conducted a mutagenic mode of action analysis and 
evaluating whether the use of an age-dependent adjustment factor (ADAF) 
for leukemia is appropriate. EPA has preliminarily concluded that a 
mutagenic mode of action is applicable to 1,3-butadiene and use of an 
age-dependent adjustment factor (ADAF) for leukemia is appropriate. EPA 
is seeking comment on this analysis and preliminary conclusion.
     The majority of occupational exposure sampling data 
points, collected from OSHA, NIOSH, and ACC's report, were not 
quantifiable values but were identified as being below the limit of 
detection (LOD). For datasets including exposure data that were 
reported as below the LOD, EPA estimated exposure concentrations, 
following EPA's Guidelines for Statistical Analysis of Occupational 
Exposure Data. Based on these guidelines, EPA used the LOD value as the 
high-end estimate and half the LOD as central tendency. EPA is seeking 
comment on this approach and the relevance of this dataset for risk 
characterization.
     General population exposure to 1,3-butadiene was modeled 
using the Human Exposure Model (HEM) to estimate ambient air 
concentrations based on releases reported to the Toxic Release 
Inventory (TRI) for years 2016 to 2021. Exposure concentrations were 
modeled at discrete distances from releasing facilities and surrounding 
census blocks. EPA is seeking comment on this analysis and preliminary 
conclusions.

III. Public Meeting of the SACC

A. What is the purpose of the virtual public meeting(s)?

    EPA is planning two virtual public meetings: (1) A preparatory 
public meeting for the SACC to consider and ask questions regarding the 
scope and clarity of the draft charge questions; and (2) a public peer 
review meeting for the SACC to consider and peer review the draft risk 
evaluation. These public meetings are part of the SACC's peer review of 
the Agency's methods and novel analyses for the draft risk evaluation 
of 1,3-butadiene. The agenda for these meetings will be posted in the 
docket and will also be available through the SACC website.
    Recommendations from this SACC review and public comments will be 
considered in the development of the TSCA risk evaluation and may 
inform other EPA efforts related to the assessment and regulation of 
the chemical substance. The Agency will be seeking SACC review of its 
data analyses and methodologies relevant to human health hazard and 
exposure analyses that have not been previously peer-reviewed.

B. How can I participate in the virtual public meeting(s)?

    To participate in these virtual public meetings, you must register 
online to receive the webcast and streaming service meeting links and 
audio teleconference information for each meeting. Online registration 
will be available beginning approximately one month prior to the 
meeting and will remain open through the end of the meeting. To make 
oral comments during one of these meetings, follow the instructions in 
this document.

C. How can I access the documents?

    The draft risk evaluation for 1,3-butadiene and related documents, 
including background documents, related supporting materials, and draft 
charge questions, are available in the docket. As additional background 
materials become available, EPA will include those additional 
background

[[Page 95782]]

materials (e.g., SACC members and consultants participating in this 
meeting and the meeting agenda) in the docket and through links on the 
SACC website at https://www.epa.gov/tsca-peer-review.

D. How can I provide comments?

    To ensure proper receipt of comments, it is imperative that you 
identify docket ID No. EPA-HQ-OPPT-2024-0425 in the subject line on the 
first page of your comments and follow the instructions in this 
document.
    1. Written comments. Submit written comments by the deadlines set 
in the DATES section of this document and as described in the ADDRESSES 
section of this document.
    2. Oral comments. To request time to present oral comments during 
one of the virtual public meetings, you must register online by the 
deadlines set in the DATES section of this document. Oral comments 
during the virtual public meetings are limited to 5 minutes. In 
addition, each speaker should submit a written copy of their oral 
comments and any supporting materials (e.g., presentation slides) to 
the DFO prior to the meetings for distribution to the SACC.

E. What happens after the SACC meeting(s)?

    After the SACC public meeting, the SACC will prepare the meeting 
minutes and final report document summarizing its recommendations to 
the EPA, which will also be available in the docket and through the 
SACC website. EPA will consider the SACC recommendations and public 
comments to complete the risk evaluation and unreasonable risk 
determination under TSCA for this chemical substance. Under TSCA, EPA 
must then initiate risk management actions to address the unreasonable 
risk it identified.
    Authority: 15 U.S.C. 2625(o); 5 U.S.C. 10.

    Dated: November 26, 2024.
Michal Freedhoff,
Assistant Administrator, Office of Chemical Safety and Pollution 
Prevention.
[FR Doc. 2024-28286 Filed 12-2-24; 8:45 am]
BILLING CODE 6560-50-P`