Chemicals Listed Effective May 20, 2016 as Known to the State of California to Cause Cancer: Tetrachlorvinphos, Parathion, and Malathion

Effective May 20, 2016, the Office of Environmental Health Hazard Assessment (OEHHA) is adding tetrachlorvinphos, parathion, and malathion to the list of chemicals known to the State of California to cause cancer for purposes of the Safe Drinking Water and Toxic Enforcement Act of 1986 (Proposition 65[1]).  

Health and Safety Code section 25249.8(a) incorporates California Labor Code section 6382(b)(1) into Proposition 65.  Regulations describing the process for listing chemicals via the Labor Code are set out in Title 27, Cal. Code of Regs., section 25904. The law requires that certain substances identified by the International Agency for Research on Cancer (IARC) be listed as known to cause cancer under Proposition 65.  Labor Code section 6382(b)(1) refers to substances identified as human or animal carcinogens by IARC. An explanation of the carcinogenicity classifications used by IARC, and the Monographs development and peer review by the international working groups of scientific experts convened by IARC, may be found at the following URL: (IARC Preamble).

The basis for the listing of tetrachlorvinphos, parathion, and malathion was described in a public notice published in the September 4, 2015, issue of the California Regulatory Notice Register (Register 2015, No. 36-Z).  The title of the notice was “Notice of Intent to List Chemicals by the Labor Code Mechanism: Tetrachlorvinphos, Parathion, Malathion, and Glyphosate.”  The publication of the notice initiated a public comment period.  We received 230 comments on tetrachlorvinphos, parathion and malathion.  The comments relevant to these three pesticides and OEHHA’s responses are posted with the Notice of Intent to List.

OEHHA intends to propose a safe harbor level (no significant risk level or NSRL) for malathion prior to the effective date of the warning requirement for exposures to that chemical.[2]

A decision concerning the proposed listing of glyphosate will be published at a later date.

A complete, updated Proposition 65 list is published elsewhere in this issue of the California Regulatory Notice Register and is available on the OEHHA website.





Listing Mechanism*













*Listing mechanism:  LC – “Labor Code” mechanism (Health and Safety Code section 25249.8(a) and Title 27 Cal. Code of Regs. section 25904)

Footnotes and References

[1]  Health and Safety Code, section 25249.5,et seq.

[2] Health and Safety Code section 25249.10 , Title 27, Cal. Code of Regs., section 25701 et seq.