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Chemicals Listed Effective May 20, 2005 as Known to the State of California to Cause Cancer: Cobalt sulfate, Diazoaminobenzene

The Office of Environmental Health Hazard Assessment (OEHHA) of the California Environmental Protection Agency is adding cobalt sulfate (CAS No. 10124-43-3) and diazoaminobenzene (CAS No. 136-35-6) to the list of chemicals known to the state to cause cancer for purposes of the Safe Drinking Water and Toxic Enforcement Act of 1986 (Health and Safety Code section 25249.5, Proposition 65). The listing of cobalt sulfate and diazoaminobenzene is effective May 20, 2005.

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 sections 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.

The basis for the listing of cobalt sulfate and diazoaminobenzene on the Proposition 65 list was described in OEHHA’s Request for Comments on Proposed Listing of Cobalt sulfate and Diazoaminobenzene As Known to Cause Cancer published in the March 18, 2005, issue of the California Regulatory Notice Register (Register 2005, No. 11-Z). Specifically, in 2005, 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 carcinogenity 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.” No public comment regarding the listing of these chemicals was received during the 30-day public comment period which closed on April 18, 2005.

OEHHA analyses of dose-response data to establish the no significant risk levels (NSRLs) for these chemicals under Proposition 65 have not been conducted. The priority status of the development of such analyses will be announced in a future OEHHA Proposition 65 Status Report for Safe Harbor Levels.

Cancer

Chemical CAS No. Toxicological Endpoint 1Listing Mechanism
Cobalt sulfate 10124-43-3 Cancer LC
Diazoaminobenzene 136-35-6 Cancer LC

1Listing mechanism:

LC – “Labor Code” mechanism (Labor Code sections 6382(b)(1) and (d))

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