Chemicals That Are "Possibly" Carcinogenic Cannot Be Added to California Proposition 65 List

The California Court of Appeal recently issued an opinion holding that chemicals, including styrene and vinyl acetate, that are “possibly” carcinogenic could not be included on the Governor’s list of chemicals known to the state of California to cause cancer or reproductive toxicity, a.k.a. Proposition 65.

In Styrene Information and Research Center v. Office of Environmental Health Hazard Assessment (Nov. 15, 2012, C064301) ___Cal.App.4th __, the Court of Appeal held that based on the express language of California statutory provisions relating to The Safe Drinking and Toxic Enforcement Act of 1986, commonly referred to as Proposition 65, only those chemicals “known to the state to cause cancer or reproductive toxicity” could be included on the Governor’s list of chemicals.

The Court found that chemicals labeled “possibly” carcinogenic by International Agency for Research on Cancer (“IARC”) could include chemicals “based on less than sufficient evidence of carcinogenicity in either humans or experimental animals.” Therefore, such chemicals would not qualify to be included in the Governor’s list of chemicals.

Proposition 65 requires the Governor to maintain a list of chemicals known to cause cancer of reproductive toxicity. (Health & Saf. Code, § 25249.8, subd. (a).) Once a chemical is placed on the list, businesses that manufacture, import or use such chemicals are required to stop adding that chemical to any drinking water source and provide a public warning if they knowingly or intentionally expose any individual to that chemical. (California Chamber of Commerce v. Brown (2011) 196 Cal.App.4th 233, 238-239.)

The Proposition 65 list must include substances identified by reference in Labor Code section 6382, subdivisions (b) and (d). (Health & Saf. Code, § 25249.8, subd. (a).) Labor Code section 6382, subdivision (d) identifies by reference “any substance within the scope of the federal Hazard Communication Standard (“HCS”).” The HCS in turn identifies several sources, such as the IARC monographs, “as establishing that a chemical is a carcinogen or potential carcinogen.”

The IARC categorizes chemicals into four groups based on the level of carcinogenicity. The Court of Appeals was faced with the issue of deciding whether chemicals categorized by the IARC as Group 2B chemicals (e.g. styrene and vinyl acetate), which include those that are “possibly” carcinogenic to humans based on less than sufficient evidence of carcinogenicity in experimental animals and supporting evidence from mechanistic and other relevant data, should be included on the Proposition 65 list.

On June 12, 2009, the Office of Environmental Health Hazard Assessment (OEHHA) published a list of new chemicals, including styrene and vinyl acetane, to be added to the Proposition 65 list. Styrene is used primarily to manufacture synthetic rubber and plastic for automobile and boat parts. It is also used to make carpet backing, plumbing, and electrical components. Vinyl acetate is a key ingredient for intermediates used in paints, adhesives, coatings, and acrylic fibers. The food industry uses vinyl acetate, for example, as a coating for plastic wraps and in food starch. Both styrene and vinyl acetane had previously been categorized as possibly carcinogenic within IARC’s Group 2B category.

In July 2009, Styrene Information and Research Center, a non-profit corporation engaged in research and public dissemination of information about styrene, initiated this action seeking a declaration from OEHHA that styrene is not a known carcinogen and a temporary restraining order prohibiting OEHHA from including styrene on the Proposition 65 list. On August 20, 2009, the trial court granted the order concluding that styrene is not a known carcinogen. On August 26, 2009, Celanese Corporation, the world’s leading producer of vinyl acetate, was granted leave to file a complaint in intervention seeking declaratory and injunctive relief prohibiting OEHHA from including vinyl acetate on the Proposition 65 list because it is not a known human or animal carcinogen. On December 17, 2009, the trial court concluded that styrene and vinyl acetate are not known carcinogens and therefore should not be included on the Proposition 65 list. OEHHA appealed.

OEHHA argued on appeal that under the prior case, AFL-CIO v Deukmejian (1989) 212 Cal.App.3d 425 (“Deukmejian”), even “possibly” carcinogenic substances could be incorporated from the HCS. The Court of Appeals disagreed because all the court had found in Deukmejian, was that both human and animal carcinogens must be included in the Proposition 65. The court in Deukmejian did not address whether substances for which there was not sufficient evidence of carcinogenicity in either animals or humans should also be on the list.

In its ruling, the Court of Appeals went beyond Deukmejian and held that the Proposition 65 list should only incorporate substances from the HCS that are “known” carcinogens and reproductive toxins. The Court reasoned that the Proposition 65 reference to Labor Code section 6382 in Health and Safety Code 25249.8, subdivision (a) should be read in conjunction with the prior language requiring the Governor to publish a list of chemicals “known to the state to cause cancer or reproductive toxicity.” Thus, the chemicals included in IARC’s Group 2B based on less than sufficient evidence to carcinogenicity in either animals or experimental animals did not satisfy the main requirement of being “known to the state to cause cancer or reproductive toxicity” to warrant inclusion on the Proposition 65 list.