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Chemicals Delisted Effective December 8, 2006 from the List of Chemicals Known to the State of California to Cause Cancer, isosafrole, 5-nitro-o-anisidine, tris(aziridinyl)-p-benzoquinone

The Office of Environmental Health Hazard Assessment (OEHHA) of the California Environmental Protection Agency is removing isosafrole [CAS No. 120-58-1], 5-nitro-o-anisidine  [CAS No. 99-59-2], and tris(aziridinyl)-p-benzoquinone (triaziquone) [CAS No. 68-76-8] from the list of chemicals known to the State to cause cancer for purposes of the Safe Drinking Water and Toxic Enforcement Act of 1986 (Proposition 65).  The delisting of the three chemicals is effective December 8, 2006. 

Each of these chemicals was originally added to the Proposition 65 list on October 1, 1989 pursuant to Labor Code Sections 6382(b)(1) and (d) which are incorporated by reference as Proposition 65 listing provisions pursuant to Health and Safety Code Section 25249.8(a).  Labor Code Section 6382(b)(1) requires inclusion of substances listed as human or animal carcinogens by the International Agency for Research on Cancer (IARC).  Labor Code Section 6382(d) requires the inclusion of chemicals within the scope of the federal Hazard Communication Standard (29 CFR 1910.1200), which establishes that a chemical is a carcinogen or potential carcinogen for hazard communication purposes if it is identified as such by IARC or the National Toxicology Program (NTP).  Isosafrole and tris(aziridinyl)-p-benzoquinone were listed under Proposition 65 based on Labor Code 6382(d).  Both chemicals were on a hazardous chemicals list because of findings of carcinogenicity by IARC.  5-Nitro-o-anisidine was also listed based on Labor Code 6382(d).  It was identified as causing cancer by the NTP.

  1. 5-Nitro-o-anisidine was removed from the NTP Sixth Annual Report on Carcinogens as a substance “reasonably anticipated to be a human carcinogen” in 1991, when NTP concluded there was insufficient evidence of carcinogenicity.  The more recent Report on Carcinogens, Eleventh Edition identifies substances delisted from the Report, and can be found in Appendix B.  IARC currently classifies 5-nitro-o-anisidine as Group 3:  Not classifiable as to its carcinogenicity to humans.  Isosafrole and tris(aziridinyl)-p-benzoquinone are also currently classified by IARC as Group 3:  Not classified as to their carcinogenicity in humans.  A list of all agents currently classified as Group 3 by IARC can be found at

Since these chemicals were added to the Proposition 65 list by operation of law based on the Labor Code Section incorporation by reference of chemicals identified as known or potential carcinogens within the scope of the federal Hazard Communication Standard (29 CFR 1910.1200), the removal of 5-nitro-o-anisidine from designation as such by the NTP and classification of isosafrole and tris(aziridinyl)-p-benzoquinone  as Group 3 by IARC means that these chemicals should be removed from the Proposition 65 list. 

The reader is directed to the Notice to Interested Parties published in the September 8, 2006 issue of the California Regulatory Notice Register (Register 06, No. 36-Z) for the supporting documentation which OEHHA relied upon in its reconsideration of the listing of isosafrole, 5-nitro-o-anisidine, and tris(aziridinyl)-p-benzoquinone (triaziquone).  The September 8 Notice also provided an opportunity for public comment on the intended delisting of these three chemicals.  No comments were received.

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