OVERVIEW OF N-PROPYLBROMIDE (NPB)

UNITED STATES

Several solvents which are used in industrial parts cleaning operations, including prior and after heat treatment processes, are currently filed under Risk Evaluation by the Environmental Protection Agency (EPA) under the Toxic Substances Control Act (TSCA).

There are various other regulations which affect industrial cleaning applications, such as The Clean Air Act including NESHAP, The Resource Conservation and Recovery Act or The Clean Water Act. Nevertheless, the scope of this article is limited to TSCA only as this is a regulation which is applied all over the US without further break-down of state individual adoptions. However, SAFECHEM recommends readers also taking into account state specific regulation. There are very strict regulations in certain states like California which are further limiting the use of certain chemistries (e.g. on Ground Water Protection).

Under TSCA, the Risk Evaluation Process is the second step, following Prioritization and before Risk Management. The purpose is to determine whether a chemical substance presents an unreasonable risk to health or the environment, under the conditions of use, including an unreasonable risk to a relevant potentially exposed or susceptible subpopulation. As part of this process, the EPA must evaluate both hazard and exposure, exclude consideration of costs or other non-risk factors, use scientific information and approaches in a manner that is consistent with the requirements in TSCA for the best available science, and ensure decisions are based on the weight-of-scientific-evidence.

Currently, all kind of brominated and chlorinated solvents are under review. This includes the use of N-propylbromide (nPB), Trichloroethylene (TRIC), Perchloroethylene (PERC) and Methylene Chloride/Dichloromethane (DCM) but also trans-Dichloroethylene (t-DCE).

The EPA released a final revised risk evaluation on nPB in December 2022 and found unreasonable risks to workers, occupational non-users, consumers, and bystanders in 23 out of 25 conditions of use.

The EPA will develop ways to address the unreasonable risks identified and will take public comments into account when formulating risk management measures. Proposals by the EPA for nPB were already published in the Federal Register in July 2024. The proposed rule allows for the continued use of nPB in vapor degreasing under a Workplace Chemical Protection Program (WCPP). Cornerstone of the WCPP is the proposed Existing Chemical Exposure Limit (ECEL) of 0.05 ppm as an 8-hour average exposure limit. If companies can adhere to this value and implement a reasonable WCPP including regular exposure measurements, they can continue using nPB.

A public comment phase is open until the end of September 2024, during which the EPA invites all interested parties to submit feedback on the proposed rule. The EPA will then review the comments and consider them in the final rulemaking for nPB under TSCA.

For additional information please visit:

Final Risk Evaluation: Final Risk Evaluation for 1-Bromopropane (1-BP) | US EPA
Risk Management: Risk Management for 1-Bromopropane (1-BP) | US EPA
Proposed Rule: 2024-17204.pdf (govinfo.gov)