It's the evidence; IARC Group 2B ≠ Proposition 65

Styrene and Vinyl Acetate Cannot be Listed Via Labor Code Mechanism

The issue presented to the Court was whether chemicals categorized in Group 2B by an IARC monograph can be included on the Proposition 65 list. "The trial court answered the question in the negative and we agree."

A chemical must be known to the state to cause cancer for it to be listed under Proposition 65 (Safe Drinking Water and Toxic Enforcement Act of 1986; Health & Safety Code § 25249.5 et seq.). Specifically addressing the Labor Code listing mechanism of Proposition 65, a three-judge panel unanimously held that neither styrene or vinyl acetate could be added to the Proposition 65 list because their International Agency on Cancer (IARC) Group 2B classifications did not provide "sufficient" evidence that the chemicals were known to be carcinogens as required by section 25249.8 of the California Health and Safety Code. Styrene Information and Research Center, Inc. v. OEHHA, Cal. App. 3^rd, No. C064301 (Oct. 31, 2012). On November 6, OEHHA filed a motion asking the court to modify its opinion; that motion is still pending but will not change the judgment even if granted.

History of the Litigation

In June 2009, the California Environmental Protection Agency's Office of Environmental Health Hazard Assessment (OEHHA) proposed listing 12 substances, including styrene and vinyl acetate monomer, under the Labor Code mechanism of Proposition 65. While some chemicals were proposed for listing due to their classification by IARC, OEHHA did not propose to list styrene and vinyl acetate based on their IARC Group 2B status. Rather, OEHHA claimed that styrene and vinyl acetate should be listed under the Labor Code provision because they are carcinogens under the Occupational Safety and Health Administration's (OSHA) Hazard Communications Standard (HCS). However, they are only HCS carcinogens due to their IARC 2B status, not from any OSHA regulation or decision.

In July 2009, the Styrene Information and Research Center, Inc. (SIRC) brought an action in California state court challenging OEHHA's proposal to list styrene under the Labor Code provision. SIRC's motion for a preliminary injunction was granted, and OEHHA was ordered not to add styrene to the Proposition 65 list of chemicals until the court reached a decision on the merits of the case brought by SIRC. The court also granted a motion by Celanese, a manufacturer of vinyl acetate, to intervene in the SIRC Proposition 65 litigation.

The issue presented to the trial court was whether chemicals categorized in Group 2B by an IARC monograph can be included on the Proposition 65 list. As stated by the Court of Appeal, "the trial court answered the question in the negative and we agree."

Proposition 65 and the Labor Code Mechanism

Proposition 65 requires the Governor to maintain a list of chemicals known to the state to cause cancer or reproductive toxicity.[1] There are a number of mechanisms by which a chemical can be listed, one of which is by reference to the California Labor Code sections 6382 (b)(1) and (d). The Labor Code section 6382 (d) in turn references the federal HCS, 29 C.F.R. section 1910.1200, which in turn references IARC monographs as one of several sources as establishing that a chemical is a carcinogen or potential carcinogen.[2]

Critical to the decision in this case, IARC categorizes chemicals based on the strength of the human, animal and other evidence of carcinogenic potential. IARC strives to determine whether the toxicological evidence is sufficient, limited or inadequate.

The Decision: The Chemical Must be a Known Carcinogen

The Court of Appeal in this case based its decision on two principles. First, a chemical must be included on the Proposition 65 list if it is identified by reference in the Labor Code section 6382 (d) as one known to cause cancer in either humans or animals. AFL-CIO v. Deukmejian, 212 Cal.App. 3d 425 (1989) (Deukmejian). Second, the Proposition 65 list can and must be regularly updated by the state as set forth by the Labor Code reference, Health and Safety Code section 25249.8(a). California Chamber of Commerce v. Brown, 196 Cal.App. 4th 233 (2011) (Brown).

In the 1989 Deukmejian decision, the Court of Appeal concluded that a chemical must be included on the Proposition 65 list if it is identified by reference in the Labor Code section 6382 (d) as one known to cause cancer in either humans or animals. Revisiting the issue in SIRC v. OEHHA as it applied to the IARC Group 2B chemicals, the Court carefully examined the statutory construction and legislative history of the Health and Safety Code section 25249.8 and its references to the Labor Code and subsequent references to the federal HCS and IARC. With regard to the application of the IARC Groups, the Court affirmed that "substances within IARC Group 1 clearly must be listed, [and] beyond that, the question is not whether a chemical is "probably" carcinogenic to humans, but whether it is in fact a known carcinogen or reproductive toxin."[3] Because IARC does not use the term "known carcinogen", the Court restated that the "for the purpose of interpreting the IARC monographs, "sufficient evidence" of carcinogenicity is the equivalent of "known" carcinogenicity."[4]

In the 2011 Brown decision, the Court of Appeal addressed the methods by which the Proposition 65 list can be updated, and specifically whether OEHHA had the authority to add chemicals to the list by use of the Labor Code mechanism. The California Chamber of Commerce argued that the duty to include chemicals through the Labor Code mechanism was only applicable to the establishment of the initial Proposition 65 list, and that subsequent actions to add chemicals to the list through the Labor Code exceeded OEHHA's authority. The Court reviewed this question of statutory construction de novo and concluded that since the statute is ambiguous, the legislative history (included ballot summaries and arguments) had to be studied to determine the voters' intent and understanding of the ballot measure.[5] It concluded and the Court of Appeals affirmed SIRC v. OEHHA that, "given the remedial purposes of Proposition 65 and the mandate that it be broadly construed, … the Labor Code reference method set forth in subdivision (a) of section 25249.8 continues to specify the minimum content of the Proposition 65 list as it revised and republished."[6] In other words, "the Proposition 65 list is not frozen in time but may be updated as the lists identified by the HCS are updated."

Based on the principles in Deukmejian and Brown, the Court concluded that OEHHA cannot list every chemical referenced by the federal HCS as a "carcinogen" or "potential carcinogen" because such as approach would result in listing chemicals that are not known carcinogens. The Court noted that vinyl acetate's 1995 IARC classification was based on inadequate evidence of carcinogenicity in humans and limited evidence of carcinogenicity in experimental animals, while styrene's 2002 IARC classification was based on limited evidence of carcinogenicity in both humans and experimental animals. In neither case did IARC find sufficient evidence of carcinogenicity. The Court of Appeals thus held:

Because the findings in the IARC monograph on which OEHHA relies to list styrene and vinyl acetate do not satisfy that standard [that there is sufficient evidence of carcinogenicity], they cannot properly be included on the list on that basis alone. And because OEHHA does not propose any other basis for including those substances on the list, they must be excluded.[7]

Also noteworthy is the Court's response to OEHHA's argument that its interpretation of the Labor Code Mechanism was entitled to deference by the Court. The Court, however, found that the agency was entitled to "little or no deference", particularly because the agency had not used the Labor Code mechanism for listing chemicals based on their inclusion in an IARC monograph for the first 15 years the statute was in effect and does not have a long-standing interpretation of the statute and has not adopted a formal regulation interpretation of the statute. The Court stated that while "OEHHA may have an interpretative advantage over the courts in determining whether a particular chemical causes cancer, it does not have such advantage in determining whether the appropriate standard under the statute is one of known cause or possible cause."

There is some ambiguity in the Court's opinion as to whether any chemical that IARC placed in Group 2B may be listed via the Labor Code → OSHA HCS → IARC cross reference system, or whether a chemical in IARC Group 2B can be listed only if IARC determined that there was sufficient evidence of carcinogenicity in animals. This is what prompted OEHHA's motion requesting that the Court modify two sentences in its opinion. Based on OEHHA's apparent interpretation of the decision, SIRC v. OEHHA does not shut the door on listing an IARC 2B chemical under Proposition 65 by the Labor Code mechanism provided that IARC's determination rested on "sufficient evidence" of carcinogenicity in animals.

According to the 2006 Preamble to the IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, which describes the scientific principles and procedures used in development IARC monographs, Group 2B are "those substances "possibly" carcinogenic to human based on a finding that there is "limited evidence of carcinogenicity in humans and less than sufficient evidence of carcinogenicity in experimental animals. It may also be used when there is inadequate evidence of carcinogenicity in humans but there is sufficient evidence of carcinogenicity in experimental animals."[8] In SIRC v. OEHHA, the Court referenced the Deukmejian case for the proposition that the Labor Code section 6382 (d) "incorporated the HCS which includes known animal carcinogens." "IARC Group 2 and supplemental category chemicals as to which there is sufficient evidence that exposure causes cancer or reproductive toxicity in animals are also known carcinogens." This language supports the view that the state of California can list a chemical as Proposition 65 chemical based on an IARC 2B listing of sufficient animal evidence of carcinogenicity, and OEHHA filed its Motion for Modification of the Opinion to strengthen the support for this approach.

It is unclear why OEHHA is so concerned about this Labor Code subdivision (d) interpretation, which references OSHA HCS. Subdivision (b)(1) of Labor Code section 6382 refers to substances listed as human or animal carcinogens by IARC. That appears to be as separate basis on which OEHHA could act. In addition, recent amendment to the OSHA HCS may further diminish the utility of Labor Code subdivision (d) as the basis for future Proposition 65 listings.[9]