Risk Evaluation under the Toxic Substances Control Act: 1,3-Butadiene

1,3-Butadiene; Risk Evaluation Under the Toxic Substances Control Act (TSCA); Notice of Availability

SUPPLEMENTARY INFORMATION:

I. Executive Summary

A. 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 (defined under TSCA section 3(9) to include import), processing, distribution, use, and disposal of 1,3-butadiene, related industry trade organizations, non-governmental organizations with an interest in human and environmental health, State and local governments, Tribal Nations, and/or those interested in the assessment of risks involving chemical substances and mixtures regulated under TSCA. As such, the Agency has not attempted to describe all the specific entities that this action might apply to. If you need help determining applicability, consult the technical contact listed under FOR FURTHER INFORMATION CONTACT .

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

The Agency conducted this risk evaluation under TSCA section 6, (15 U.S.C. 2605), which requires that EPA conduct risk evaluations on chemical substances and identifies the minimum components EPA must include in the risk evaluations. Each risk evaluation must be conducted consistent with the best available science, be based on the weight of the scientific evidence, and consider reasonably available information, and not consider costs or non-risk factors. 15 U.S.C. 2625(h), (i), and (k). See also the implementing procedural regulations at 40 CFR part 702 and 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. What action is the Agency taking?

EPA is announcing the availability of the final risk evaluation under TSCA for 1,3-butadiene. The purpose of risk evaluations under TSCA is to determine whether a chemical substance presents an unreasonable risk of injury to health or the environment under the conditions of use, including unreasonable risk to potentially exposed or susceptible subpopulations identified as relevant to the risk evaluation by EPA, and without consideration of costs or non-risk factors. EPA has used the best available science to prepare this final risk evaluation and ensured that this action is consistent with Executive Order 14303 "Restoring Gold Standard Science," (May 23, 2025). Based on the weight of scientific evidence, the Agency determined that 1,3-butadiene poses unreasonable risk to human health driven by specific conditions of use. EPA will now initiate risk management action as required pursuant to TSCA section 6(a) (15 U.S.C 2605(a)), to address the unreasonable risk.

II. Background

A. What is 1,3-butadiene?

1,3-Butadiene is a colorless gas with a total production volume (PV) in the United States between 1 and 5 billion pounds. 1,3-Butadiene is produced from petrochemical processing and is also used to aid in petrochemical manufacturing but is primarily used as a monomer to produce plastic and rubber products. This involves polymerization of 1,3-butadiene with itself or with other monomers, which are then incorporated into various rubber and plastic articles. These synthetic rubbers, resins, and latex are used to manufacture tires, other rubber components and plastic materials. 1,3-Butadiene polymers are also used as viscosity agents in several formulations for adhesives, lubricants, and paints and coatings. These polymerization products which are polymeric forms of 1,3-butadiene are also referred to as 1,3-butadiene by some chemical safety data sheets (SDSs). This risk assessment covers only the monomer form of 1,3-butadiene.

B. Summary of Activities for the Risk Evaluation of 1,3-Butadiene

On December 30, 2019, EPA announced its designation of 1,3-butadiene as a high priority substance for risk evaluation under TSCA (84 FR 71924 (FRL-10003-15)). On April 9, 2020, EPA sought public comment on the draft scope of the 1,3-butadiene risk evaluation (85 FR 19941(FRL-10007-11)) and, after considering public comments, issued the final scope on September 4, 2020 (85 FR 55281 (FRL-10013-90)). On December 3, 2024, EPA released the draft risk evaluation for public comment and external peer review by the Science Advisory Committee on Chemicals (SACC) (89 FR 95779 (FRL-12241-02-OCSPP)).

These documents, other supporting documents, and public comments are in dockets EPA-HQ-OPPT-2018-0451 and EPA-HQ-OPPT-2024-0425. The following documents are being released with this notice:

• A response to comments document titled, "Summary of and Response to External Peer Review and Public Comments on the Risk Evaluation for 1,3-Butadiene";
• A non-technical summary of the final risk evaluation titled, "Non-technical Summary of the TSCA Risk Evaluation for 1,3-Butadiene"; and
• The final risk evaluation titled, "Risk Evaluation for 1,3-Butadiene," along with multiple supporting documents.

III. Unreasonable Risk Determination

EPA has determined that 1,3-butadiene, under the conditions of use (COUs), presents an unreasonable risk of injury to human health. EPA has determined that the unreasonable risk to human health presented by 1,3-butadiene is driven by 11 of the 30 COUs. The 11 COUs that significantly contribute to the unreasonable risk determination for 1,3-butadiene are based on identified non-cancer and cancer risk to workers, including 1 COU that contributes to unreasonable risk of injury to occupational non-users, from inhalation exposure:

• Manufacturing-domestic manufacturing;
• Manufacturing-importing;
• Processing as a reactant-intermediate (adhesive manufacturing; all other basic organic chemical manufacturing; fuel binder for solid rocket fuels; organic fiber manufacturing; petrochemical manufacturing; plastic material and resin manufacturing; propellant manufacturing; synthetic rubber manufacturing; paint and coating manufacturing);
• Processing as a reactant-monomer used in polymerization process (Synthetic rubber manufacturing; plastic material and resin manufacturing);
• Processing-incorporation into formulation, mixture, or reaction product-monomers (plastic product manufacturing; plastic material and resin manufacturing; synthetic rubber manufacturing);
• Processing-incorporation into formulation, mixture, or reaction product-plasticizer (asphalt paving, roofing, and coating materials manufacturing);
• Processing-incorporation into article-monomer (rubber product manufacturing);
• Processing-use-non-incorporative activities-fuel (petroleum refineries);
• Processing-repackaging-(wholesale and retail trade fuel; synthetic rubber manufacturing; petrochemical manufacturing);
• Processing-recycling; and
• Disposal.

IV. Next Step Is Risk Management

Consistent with TSCA section 6(a), EPA will propose a risk management regulatory action, to the extent necessary, so that 1,3-butadiene no longer presents an unreasonable risk. EPA expects to focus its risk management action on the conditions of use that significantly contribute to the unreasonable risk. In proposing a rule and selecting among requirements, consistent with TSCA section 6(c)(2), EPA will consider and factor in, to the extent practicable: (i) the effects of 1,3-butadiene on health and the environment, (ii) the magnitude of exposure to 1,3-butadiene of human beings and the environment, (iii) the benefits of 1,3-butadiene for various uses, and (iv) the reasonably ascertainable economic consequences of the rule. Additional information received may inform the risk management of 1,3-butadiene and, like the prioritization and risk evaluation processes, there will be opportunity for public comment on any proposed risk management actions.

(Authority: 15 U.S.C. 2601 et seq. )