Notice of Adoption of Revised Cancer Inhalation Unit Risk Factors for Cobalt Sulfate Heptahydrate and Water-Soluble Cobalt Compounds
The Office of Environmental Health Hazard Assessment (OEHHA) is adopting revised cancer inhalation unit risk (IUR) and slope factors for cobalt and water-soluble cobalt compounds for use in the Air Toxics Hot Spots (Hot Spots) program for use in the Air Toxics Hot Spots Program. This revision corrects the cancer inhalation unit risk factors (IURs) for cobalt sulfate heptahydrate and water-soluble cobalt compounds. OEHHA adopted IURs for these compounds in October 2020.
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 requirement, OEHHA develops unit risk factors for carcinogens, such as cobalt sulfate heptahydrate. The cancer IURs are used to estimate lifetime cancer risks associated with inhalation exposure to a carcinogen. While the IURs for cobalt sulfate heptahydrate and water-soluble cobalt compounds have been corrected, the IURs for cobalt metal and insoluble cobalt compounds have not changed.
The values for Cobalt and Cobalt Compounds are as follows:
Cobalt metal and water-insoluble cobalt compounds
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 1.0 × 10-2 (µg/m3)-1
Inhalation Slope Factor 35 (mg/kg-day)-1
SRP Draft (June 15, 2023)
First Draft (May 5, 2023)
- Notice of Public Comment Period
- Summary of Corrections
- Public Comments – none received
- Public Workshop Slides and Recording
Please direct any inquiries concerning technical matters or availability of the document to:
Dr. Rima Woods, Chief
Air Toxicology and Risk Assessment Section
Office of Environmental Health Hazard Assessment
1001 I Street, 12th Floor
Sacramento, CA 95814
E-mail: rima.woods@oehha.ca.gov
Related Information
Notice of Adoption of Cancer Inhalation Unit Risk Factors for Cobalt and Cobalt Compounds, Oct 2, 2020
Hot Spots Unit Risk and Cancer Potency Values
- Comment Submissions - Notice of Public Comment Period and Workshops on a Draft Revised Cancer Inhalation Unit Risk Factors for Cobalt Sulfate Heptahydrate and Water-Soluble Cobalt Compounds
Link to Public Comments
Downloads
Scientific Review Panel Slides Cobalt
Public Workshop Slides Cobalt
Draft Revised Cancer IUR Factors for Cobalt Sulfate Heptahydrate and Water-Soluble Cobalt Compounds
Summary or the Corrections to the Cancer IUR Factors for Cobalt Sulfate Heptahydrate and Water-Soluble Cobalt Compounds