2024-21229. 1,3-Butadiene; Draft Risk Evaluation Under the Toxic Substances Control Act (TSCA); Science Advisory Committee on Chemicals (SACC) Peer Review; Request for Nominations of ad hoc Peer Reviewers

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Environmental Protection Agency

1. [EPA-HQ-OPPT-2024-0425; FRL-12241-01-OCSPP]

AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Notice.

SUMMARY:

The Environmental Protection Agency (EPA or the Agency) is seeking nominations of scientific and technical experts that EPA can consider for service as ad hoc peer reviewers assisting the Science Advisory Committee on Chemicals (SACC) with the peer review of the draft risk evaluation for 1,3-butadiene conducted under the Toxic Substances Control Act (TSCA). To facilitate nominations, this document provides information about the SACC, the intended topic for the planned peer review, the expertise sought for this peer review, instructions for submitting nominations to EPA, and the Agency's plan for selecting the ad hoc peer reviewers for this peer review. EPA is planning to convene a virtual public meeting of the SACC in early 2025 to review the draft risk evaluation.

DATES:

Submit your nominations on or before October 18, 2024.

ADDRESSES:

Submit your nomination via email to [e-mail] following the instructions in Unit III. Do not electronically submit any information you consider to be Confidential Business Information (CBI) or other information whose public disclosure is restricted by statute. If your nomination may contain any such information, please contact the Designated Federal Official to obtain special instructions before submitting that information.

FOR FURTHER INFORMATION CONTACT:

The Designated Federal Official is Alie Muneer, Mission Support Division (7602M), Office of Program Support, Office of Chemical Safety and Pollution Prevention, Environmental Protection Agency; telephone number: [phone] or call the main office at [phone]; email address: [e-mail].

SUPPLEMENTARY INFORMATION:

I. General Information

A. What action is the Agency taking?

The Agency is seeking public nominations of scientific and technical experts that EPA can consider for service as ad hoc peer reviewers for the SACC peer review of the draft risk evaluation for 1,3-butadiene. EPA will be soliciting comments from the experts on the approach and methodologies utilized in the draft risk evaluation. This document provides instructions for submitting such nominations for EPA to consider for the SACC peer review. EPA will publish a separate document in the Federal Register in the fall of 2024 to announce the availability of the draft risk evaluation and solicit public comments. The public comments received during the public comment period for the draft risk evaluation material will be provided to the SACC and ad hoc peer reviewers.

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

The SACC operates in accordance with TSCA section 26(o), 15 U.S.C. 2625(o) and the Federal Advisory Committee Act (FACA), 5 U.S.C. 10, to provide independent advice and expert consultation with respect to the scientific and technical aspects of issues relating to the implementation of 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. This action may, however, be of interest to those involved in the manufacture, processing, distribution, and disposal of chemical substances and mixtures, and/or those interested in the assessment of risks involving chemical substances and mixtures regulated under TSCA. Since other entities may also be interested, the Agency has not attempted to describe all the specific ( print page 76468) entities that may be affected by this action.

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 comprised 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, environmental engineering and sustainability). The SACC currently consists of 20 members. When needed, the committee will be assisted by ad hoc peer 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 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 assure 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 three stages of the TSCA risk evaluation process for existing chemicals ( i.e., prioritization, risk evaluation, and risk management), go to https://www.epa.gov/​assessing-and-managing-chemicals-under-tsca.

C. Why is EPA evaluating the risks from 1,3-butadiene?

In December 2019, EPA designated 1,3-butadiene (CASRN 106-99-0) as a high-priority substance for risk evaluation following the prioritization process as required by Section 6(b) of TSCA and implementing regulations (40 CFR part 702) (Docket ID: EPA-HQ-OPPT-2019-0131).

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. 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 previously classified 1,3-butadiene as a human carcinogen and epidemiology studies have demonstrated an association between 1,3-butadiene exposure and increased incidence of leukemia in workers.

EPA will be submitting the draft risk evaluation of 1,3-butadiene and associated supporting documents for external peer review. The draft risk evaluation will include 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 or susceptible subpopulations, environmental risk characterization, and human health hazard and risk characterization for workers and the general population.

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

EPA is focusing its charge to the SACC on methods and analyses that are novel and have not been reviewed in other venues. Methods and analyses used in this risk evaluation that are not novel, have been reviewed during development of the tools, used in previously reviewed agency work products, or used in previous TSCA assessments ( e.g., systematic review, BMDS, etc.) are not included in the charge questions. Feedback from this review will be considered in the development of the final risk evaluation for 1,3-butadiene under TSCA. Specifically, EPA will be seeking comment on the issues below:

• 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 will be seeking comment on the qualitative risk assessment for ecological taxa for 1,3-butadiene.
• 1,3-Butadiene photodegrades with a half-life ranging from 1.6-2.6 hours to form formaldehyde and acrolein when it reacts with hydroxyl radicals in the atmosphere. Because non-cancer health effects of formaldehyde and acrolein are dissimilar to 1,3-butadiene non-cancer health effects, risks will not be combined. EPA will be seeking comment on the preliminary decision not to combine risk from non-cancer health effects of 1,3-butadiene and its transformation products.
• Reduced fetal/neonatal body weight is observed in both mice and rats, though there is no evidence that this effect results from a single dose. No other candidate acute endpoints were identified. As such, EPA has not identified a relevant endpoint for acute, single-day exposure to 1,3-butadiene. EPA will be seeking comment on this preliminary conclusion to forego establishing an acute point of departure.
• 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 is conducting an evaluation of the relevance of ovarian atrophy for assessing human risk. EPA will be proposing to use decreased fetal body weight as the basis for the intermediate and chronic points of departure for 1,3-butadiene. EPA will be seeking comment on these preliminary conclusions to establish intermediate and chronic points of departure based on reduced fetal body weight instead of ovarian atrophy.
• OPPT is revising the inhalation unit risk (IUR) for 1,3-butadiene presented in the IRIS 2002 assessment to incorporate updated epidemiological cohort data. EPA will be seeking comment on the mathematical approach and new epidemiological cohort data used in the revised IUR.
• EPA is conducting a mutagenic mode of action analysis and evaluating whether the use of an age-dependent adjustment factor (ADAF) for leukemia is appropriate. EPA will be seeking ( print page 76469) comment on this analysis and preliminary conclusion.
• The majority of occupational exposure sampling data points, collected from OSHA, NIOSH, and ACC's report, are not quantifiable values but are identified as being below the limit of detection (LOD). For datasets including exposure data that were reported as below the LOD, EPA is estimating exposure concentrations, following EPA's Guidelines for Statistical Analysis of Occupational Exposure Data. EPA will be seeking comment on this approach and the relevance of this dataset for risk characterization.
• General population exposure to 1,3-butadiene is being 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 are being modeled at discrete distances from releasing facilities and surrounding census blocks. EPA will be seeking comment on this analysis and preliminary conclusions.

EPA intends to publish a separate document in the Federal Register to announce the availability of and solicit public comment on the draft risk evaluation for 1,3-butadiene that will be submitted to the SACC for peer review, at which time EPA will provide instructions for submitting written comments and registering to provide oral comments at the peer review meeting with the SACC that is planned for early 2025.

III. Nominations of Ad Hoc Peer Reviewers

A. Why is EPA seeking nominations for ad hoc peer reviewers?

EPA is requesting nominations from the public and stakeholder communities for scientific and technical experts who can serve as prospective candidates for ad hoc peer reviewers supporting the SACC. This is part of a broader process for developing a pool of candidates. Interested persons or organizations can nominate qualified individuals by following the instructions provided in this document. Individuals are also welcome to self-nominate.

Those who are selected from the pool of prospective candidates will be invited to attend the public meeting and to participate in the discussion of key issues and assumptions at the meeting. In addition, they will be asked to review and help finalize the meeting minutes.

B. What expertise is sought for this SACC peer review?

Individuals nominated for this ad hoc peer review should have expertise in one or more of the following areas:

1. Risk assessment.

2. Ecological risk assessment, specifically with expertise in physical chemistry, environmental fate, and synthetic polymers.

3. Human health assessment, specifically with expertise in modes of action, mutagenicity, developmental and reproductive toxicity, dose-response, and cancer epidemiology.

4. Exposure assessment, specifically with expertise in occupational inhalation monitoring and air exposure modeling.

Nominees should be scientists who have sufficient professional qualifications, including training and experience, to be capable of providing expert comments on the scientific issues for this review.

C. How do I make a nomination?

By the deadline indicated under DATES , submit your nomination via email to the email identified in ADDRESSES . Each nomination should include the following: Contact information for the person or entity making the nomination; name, affiliation, and contact information for the nominee; and the disciplinary and specific areas of expertise of the nominee.

D. Will ad hoc peer reviewers be subjected to an ethics review?

SACC members and ad hoc reviewers are subject to the provisions of the Standards of Ethical Conduct for Employees of the Executive Branch at 5 CFR part 2635, conflict of interest statutes in Title 18 of the United States Code and related regulations. In anticipation of this requirement, prospective candidates for service on the SACC as ad hoc peer reviewers will be asked to submit confidential financial information which shall fully disclose, among other financial interests, the candidate's employment, stocks and bonds, and where applicable, sources of research support. EPA will evaluate the candidates' financial disclosure forms to assess whether there are financial conflicts of interest, appearance of a loss of impartiality, or any prior involvement with the development of the documents under consideration (including previous scientific peer review) before the candidate is considered further for service.

E. How will EPA select the ad hoc peer reviewers?

The selection of scientists to serve as ad hoc peer reviewers for the SACC is based on the function of the Committee and the expertise needed to address the Agency's charge to the Committee. No interested scientists shall be ineligible to serve by reason of their membership on any advisory committee to a federal department or agency or their employment by a federal department or agency, except EPA. Other factors considered during the selection process include availability of the prospective candidate to fully participate in the Committee's reviews, ability to be hired as an EPA Special Government Employee (SGE), absence of any conflicts of interest or appearance of loss of impartiality, independence with respect to the matters under review, and lack of bias. Although financial conflicts of interest, the appearance of loss of impartiality, lack of independence, and bias may result in non-selection, the absence of such concerns does not assure that a candidate will be selected to serve on the SACC.

Numerous qualified candidates are often identified for SACC reviews. Therefore, selection decisions involve carefully weighing a number of factors including the candidates' areas of expertise and professional qualifications and achieving an overall balance of different scientific perspectives across peer reviewers. The Agency will consider all nominations of prospective candidates for service as peer reviewers that are received on or before the date listed in the DATES section of this document. However, the final selection of peer reviewers is a discretionary function of the Agency. At this time, EPA anticipates selecting approximately 8-10 ad hoc peer reviewers for this SACC peer review.

EPA plans to make a list of candidates under consideration as prospective peer reviewers for this SACC review available for public comment during the fall of 2024. The list will be available in the docket at https://www.regulations.gov (docket ID number EPA-HQ-OPPT-0425) and through the SACC website at https://www.epa.gov/​tsca-peer-review.

Dated: September 12, 2024.

Michal Freedhoff,

Assistant Administrator, Office of Chemical Safety and Pollution Prevention.