Cobalt and Cobalt CompoundsCancer Inhalation Unit Risk FactorsTechnical Support Document
Notice of Adoption of Cancer Inhalation Unit Risk Factors for Cobalt and Cobalt Compounds
Download cancer inhalation unit risk (IUR) for Cobalt and Cobalt Compounds
The Office of Environmental Health Hazard Assessment (OEHHA) is adopting new cancer inhalation unit risk (IUR) and slope factors for Cobalt and Cobalt Compounds for use in the Air Toxics Hot Spots Program. IURs are used to estimate lifetime cancer risks associated with inhalation exposure to a carcinogen.
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 implementing this requirement, OEHHA develops new IURs and revises existing IURs for many air pollutants. The IURs for cobalt and insoluble and soluble cobalt compounds were developed using the most recent guidance, “Air Toxics Hot Spots Program Technical Support Document for Cancer Potency Factors,” finalized by OEHHA in 2009.
The values for Cobalt and Cobalt Compounds are as follows:
Cobalt metal and water-insoluble cobalt compounds (normalized to cobalt content)
Unit Risk Factor 7.7 × 10-3 (µg/m3)-1
Inhalation Slope Factor 27 (mg/kg-day)-1
Water-soluble cobalt compounds (normalized to cobalt content)
Unit Risk Factor 8.6 × 10-4 (µg/m3)-1
Inhalation Slope Factor 3.0 (mg/kg-day)-1
A draft document for the Cobalt and Cobalt Compounds IURs was released on March 8, 2019, to solicit public comment and was discussed at public workshops in Oakland and Diamond Bar, CA during the subsequent 60-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 October 2019 before being finalized.
Please direct any inquiries concerning technical matters or availability of the documents to:
Dr. John Budroe, Chief
Air Toxicology and Risk Assessment Section
Office of Environmental Health Hazard Assessment
1515 Clay Street, 16th Floor
Oakland, CA 94612
E–mail: john.budroe@oehha.ca.gov