California Court of Appeal Affirms that Methylmercury in Tuna is “Naturally Occurring”

By Riëtte van Laack –

In 2004, the State of California sued three tuna companies, Tri-Union Seafoods, LLC, Del Monte Corporation, and Bumble Bee Seafoods, LLC, for violation of California’s Proposition 65 because they failed to provide the required clear and reasonable warning that their canned tuna products contain methylmercury, a chemical listed by the State of California as a reproductive toxin and carcinogen.

Defendants argued that no warning was required under Proposition 65 because: (1) in this situation, federal law preempts Proposition 65; (2) the level of methylmercury is below the threshold at which a warning statement is required; and (3) almost all the methylmercury in canned tuna is “naturally occurring” and therefore no warning statement is required.  The trial court agreed and found for the defendants.

The Court of Appeal only reached to the lower court’s conclusion that methylmercury is “naturally occurring” in tuna.  Under Proposition 65, a substance is naturally occurring if it a “natural constituent of a food” or “is present in the food solely as a result of absorption or accumulation of the chemical . . . present in the environment in which the food is raised, or grown, or obtained . . . .”  Such substances are exempt from requirements under Proposition 65.  The defendant bears the burden of proof to show with a preponderance of the evidence that the chemical is naturally occurring.

After a detailed analysis, the Court of Appeal affirmed the lower court’s finding that based on currently available evidence methylmercury is naturally occurring.  The Court pointed out, however, that its decision does not mean that tuna companies are immune to future Proposition 65 claims.  The Court stressed that its decision is based on the present state of research and that “‘scientific conclusions are subject to perpetual revisions.’”  Moreover, the Court noted that California might amend its Proposition 65 regulations such that methylmercury is no longer exempt from the warning requirements.

The Court also emphasized that it did not consider whether the trial court’s other grounds for the judgment in favor of the defendants were valid.  Consequently, the Court’s decision is conclusive only as to the single determination that methylmercury in tuna is naturally occurring for purposes of Proposition 65.