Notice of Adoption of Reference Exposure Levels for 1-Bromopropane

Apr 28, 2023

The Office of Environmental Health Hazard Assessment (OEHHA) is adopting new Reference Exposure Levels (RELs) for 1-Bromopropane (1-BP) for use in the Air Toxics Hot Spots Program. RELs are airborne concentrations of a chemical that are not anticipated to result in adverse noncancer health effects for specified exposure durations in the general population, including sensitive subpopulations. The adopted RELs cover different types of exposure to 1-BP in air: infrequent 1-hour exposures, repeated 8-hour exposures, and continuous long-term exposure.

OEHHA is required to develop guidelines for conducting health risk assessments under the Air Toxics Hot Spots Program (Health and Safety Code Section 44360(b)(2)). In response to this statutory requirement, OEHHA develops RELs for many air pollutants, including 1-BP. The 1-BP RELs were developed using the most recent “Air Toxics Hot Spots Program Technical Support Document for the Derivation of Noncancer Reference Exposure Levels” (OEHHA, 2008). 1-BP will also be added to the list of Toxic Air Contaminants that may disproportionately impact children, pursuant to Health and Safety Code Section 39669.5(b)(1).

A draft document for the 1-BP RELs was released on January 7, 2022 to solicit public comment and was discussed at a virtual public workshop (January 26, 2022) during the subsequent 45-day public review period. The document was revised to reflect public comments, and peer reviewed by the State’s Scientific Review Panel (SRP) on Toxic Air Contaminants in May 2022 before being finalized.

The 1-BP REL values are as follows:

Acute REL (for infrequent 1–hour exposures): 3,300 micrograms per cubic meter (μg/m³) (700 parts per billion (ppb))
Chronic REL (for long–term exposures): 1.7 µg/m³ (0.3 ppb)
8–Hour REL (for repeated 8–hour exposures): 3.4 µg/m³ (0.7 ppb)

Adoption Memo

SRP Draft (May 12, 2022)