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Proposition 65 Notice of Intent to List Isopyrazam and 3,3’,4,4’-Tetrachloroazobenzene
(July 2012)

California’s Office of Environmental Health Hazard Assessment (OEHHA) intends to list the chemicals isopyrazam and 3,3’,4,4’-tetrachloroazobenzene as known to the state to cause cancer under the Safe Drinking Water and Toxic Enforcement Act (Proposition 65).

A chemical is listed under Proposition 65 when two conditions are met:
1. An authoritative body formally identifies the chemical as causing cancer (Section 25306(d)).
2. The evidence considered by the authoritative body meets the sufficiency criteria contained in the regulations (Section 25306(e)).

OEHHA has determined that isopyrazam, used as a Pyrazole fungicide, and 3,3’,4,4’-tetrachloroazobenzene, used as a herbicide, meet the criteria for listing under Proposition 65 based on findings by EPA and the National Toxicology Program (NTP). EPA reports conclude isopyrazam is “likely to be carcinogenic to humans” due to evidence described in the report: Cancer Assessment Document, Evaluation of the Carcinogenic Potential of Isopyrazam, which shows that isopyrazam causes increased incidences of malignant and combined malignant and benign thyroid tumors in male rats and malignant tumors of the uterus in female rats.

With regards to 3,3’,4,4’-tetrachloroazobenzene, NTP published a report: Toxicology and Carcinogenesis Studies of 3,3’,4,4’-Tetrachloroazobenzene (TCAB) in Harlan Sprague-Dawley Rats and B6C3F1 Mice, which concludes that 3,3’,4,4’-tetrachloroazobenzene causes cancer. NTP found that 3,3’,4,4’-tetrachloroazobenzene increases incidences of malignant tumors at multiple sites in male rats, rare malignant tumors of the oral cavity in female rats, malignant tumors at multiple sites in male mice, and malignant tumors at multiple sites in female mice.

Proposition 65 states that no person in the course of doing business releases any chemical known to cause cancer or reproductive toxicity into water or land where the chemical may pass through to a source of drinking water. It also requires a chemical warning label if intentionally exposing any individual to a chemical known to the state to cause cancer or reproductive toxicity.

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