ILMA Joins Push for Update to CARB’s Chromium 6 Risk Factor
California’s current CrVI inhalation unit risk factor (IUR)—based on a 1985 study of workers in a pre-1940s Ohio chromate plant—drives health risk calculations and regulatory thresholds under the state’s air toxics laws, including the Toxic Air Contaminant Identification and Control Act (TAC Act) and the Hot Spots Act.
Given that new epidemiological and toxicological data has emerged, the petition urges California regulators to reconsider the substance’s IUR based on the best available science as required by the TAC Act. A revised IUR will ensure that public health protections are based on sound science and that regulatory efforts are appropriately tailored based on risk.
The petition cites two important developments for consideration:
- The U.S. EPA’s 2024 IRIS Assessment replaced its 1998 CrVI risk values with new unit risk estimates based on a large, well-characterized cohort from a Baltimore chromate production facility (Gibb et al. 2020), which includes robust exposure data and control for confounding variables such as smoking.
- Recent peer-reviewed studies (Lipworth et al. 2025 and Allen et al. 2025) expand the evidence base with lower-exposure cohorts, including female workers, and confirm that the current California IUR overpredicts risk by more than an order of magnitude.
New Emissions Control in SoCal
ILMA has been monitoring regulatory developments in Southern California relevant to CrVI. Specifically, the South Coast Air Quality Management District is proposing emissions control requirements for metal heat treating operations. While a final proposal has yet to be submitted, it appears that regulators may impose enclosure requirements for furnaces and quench tanks, as well as HEPA filtration systems to address exhaust emissions.
The stringency of this regulation may well depend on current CrVI risk values. It is imperative for California regulators to update the substance’s IUR before new emissions control requirements are put in place.
“Sound science must guide public policy—especially when the stakes for our industry’s operations, compliance investments and public image are so high,” said ILMA CEO Holly Alfano.
The Association will continue to monitor CARB’s response and provide updates. For questions or to get involved, please contact Jorge Roman, ILMA Regulatory Counsel.