The Office of Environmental Health Hazard Assessment (OEHHA) of the California Environmental Protection Agency is adding carbon black (airborne, unbound particles of respirable size) 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 (Proposition 65). The listing of carbon black is effective February 21, 2003.

The listing of carbon black (airborne, unbound particles of respirable size) (CAS No, 1333-86-4) is based on a formal identification by an authoritative body (i.e., the International Agency for Research on Cancer ["IARC"]) that this chemical causes cancer. Regulations governing the listing of chemicals under the "authoritative bodies" mechanism are published in Title 22, California Code of Regulations, Section 12306. The reader is directed to the Notice of Intent to List carbon black published in the October 29, 1999, issue of the California Regulatory Notice Register (Register 99, No. 44-Z) for the documentation supporting OEHHA's determination that the criteria for administrative listing have been satisfied for this chemical. The following describes the unique aspects of the listing of carbon black.

The listing only pertains to airborne, unbound carbon black particles of respirable size. As noted by IARC, the respirable fraction is "that fraction of an aerosol with an aerodynamic diameter suitable for penetration into the alveoli/gas exchange region of the lung (typically <10 µm)" (pp. 171-172, Volume 65, IARC Monographs on the Evaluation of Carcinogenic Risks to Human, 1996). OEHHA and the California Air Resources Board have also noted that, "In general, particles 10 µm or less in diameter are considered respirable by humans " (California Environmental Protection Agency, Air Resources Board, Staff Report: Public Hearing to Consider Amendments to the Ambient Air Quality Standards for Particulate Matter and Sulfates, prepared by staff of the Air Resources Board and OEHHA, 2002). Thus, for the purposes of Proposition 65, carbon black particles 10 µm or less shall be considered respirable. Exposure to carbon black, per se, does not occur when it remains bound within a product matrix, such as rubber, ink or paint.

A complete, updated Proposition 65 list is published elsewhere in this issue of the California Regulatory Notice Register. The following table outlines the addition of carbon black (airborne, unbound particles of respirable size) to the Proposition 65 chemical list as known to the State to cause cancer:

¹ Listing mechanism:
AB - "authoritative body" mechanism (22 CCR Section 12306)

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For questions regarding Proposition 65, please contact the Cynthia Oshita in the Proposition 65 Implementation Program

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