The California Office of Environmental Health Hazard Assessment (OEHHA) issued an informational letter on Proposition 65 enforcement related to the listing of vinyl acetate in December 2025, prior to when the vinyl acetate warning requirements took place on January 3, 2026. OEHHA explained in the letter that vinyl acetate is mostly used in the production of polymers and copolymers; however, none of those polymers or copolymers are listed under Prop. 65. 

OEHHA’s letter also provided guidance on the evidence needed to support a failure to warn claim and how to evaluate potential exposures to vinyl acetate under Prop 65. As background, a business has an affirmative defense to an assertion that a Prop. 65 warning is required if it can establish that the exposure from a product would be less than the “safe harbor” level associated with a given chemical. OEHHA has established safe harbor levels—which include No Significant Risk Levels (NSRLs) for cancer-causing chemicals and Maximum Allowable Dose Levels (MADLs) for chemicals causing reproductive toxicity—for many of the chemicals listed under Prop. 65. However, OEHHA has not yet proposed a safe harbor level for vinyl acetate. (For background information on safe harbor levels, see the packaginglaw.com article, Safe Use Determinations under California’s Proposition 65: What You Need to Know.)

“The ideal test for this chemical would reflect the amount of vinyl acetate released from the product during use or at other times when people could be exposed; tests which reflect the vinyl acetate present in the product at such times would also be useful,” OEHHA wrote in the letter and then cautioned against dissolving vinyl acetate-containing polymers in a manner which would not otherwise occur during use of the item when testing for compliance under Prop. 65.