Request for Comments on Proposed Listing of Cobalt Sulfate and Diazoaminobenzene as Known to Cause Cancer

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The California Environmental Protection Agency's Office of Environmental Health Hazard Assessment (OEHHA) is the lead agency for the implementation of the Safe Drinking Water and Toxic Enforcement Act of 1986 (Health and Safety Code section 25249.5 et seq ., Proposition 65). OEHHA is proposing to include cobalt sulfate (CAS No. 10124-43-3) and diazoaminobenzene (CAS No. 136-35-6) on the list of chemicals known to the state to cause cancer, for the purposes of Proposition 65.

Health and Safety Code section 25249.8(a) requires that certain substances identified by the International Agency for Research on Cancer (IARC) or the National Toxicology Program (NTP), as described in Labor Code section 6382(b)(1) and (d), be included on the Proposition 65 list. Labor Code section 6382(b)(1) references substances identified as human or animal carcinogens by IARC, and Labor Code section 6382(d) references substances identified as carcinogens or potential carcinogens by IARC or NTP. Cobalt sulfate and diazoaminobenzene were identified by the NTP as reasonably anticipated to be human carcinogens.

In 2005, the NTP issued the Eleventh Report on Carcinogens. In this report, the NTP concluded that “Cobalt sulfate is reasonably anticipated to be a human carcinogen based on sufficient evidence of carcinogenicity in experimental animals.” In the same report, the NTP concluded that diazoaminobenzene (DAAB) is “reasonably anticipated to be a human carcinogen based on evidence from studies in animals and with human tissue demonstrating that DAAB is metabolized to benzene, a known human carcinogen, and on evidence that DAAB causes genetic damage.”

Pursuant to state law, NTP's designation of cobalt sulfate and diazoaminobenzene as potential human carcinogens means that “cobalt sulfate” and “diazoaminobenzene” must be included on the Proposition 65 list (Labor Code section 6382(d)). Therefore, OEHHA proposes to add “cobalt sulfate” and “diazoaminobenzene” to the Proposition 65 list of chemicals known to cause cancer. Anyone wishing to provide comments as to whether these chemicals meet the requirements for listing as causing cancer specified in Health and Safety Code section 25249.8(a), by reference to Labor Code section 6382(d), should send written comments in triplicate, along with any supporting documentations, by mail or by fax to:

Office of Environmental Health Hazard Assessment
Street Address: 1001 I Street
Sacramento, California 95814

Mailing Address: P.O. Box 4010
Sacramento, California 95812-4010

Fax No.: (916) 323-8803
Telephone: (916) 445-6900

Comments may also be delivered in person or by courier to the above address. It is requested, but not required, that written comments and supporting documentation by transmitted via email addressed to: In order to be considered, comments must be postmarked (if sent by mail) or received at OEHHA (if hand-delivered, sent by FAX, or transmitted electronically) by 5:00 p.m. on Monday, April 18, 2005.