Starting on Jan. 3, 2026, warning requirements for vinyl acetate can be enforced under California’s Proposition 65, which is commonly referred to as “Prop 65.” The California agency charged with implementing Prop 65, the Office of Environmental Health Hazard Assessment (OEHHA), has listed vinyl acetate as a chemical known to the state of California to cause cancer, and a clear and reasonable warning will be required for certain exposures to vinyl acetate from consumer products, the workplace or the environment. Companies with products containing vinyl acetate would be well-advised to start considering compliance measures.
Vinyl Acetate Is a Widely Used Chemical
Vinyl acetate is a synthetic chemical that readily evaporates into air and easily dissolves in water. Like other esters, it is synthesized from an alcohol and an acid, but vinyl acetate is synthesized from unstable vinyl alcohol. Once synthesized, vinyl acetate is a volatile, flammable liquid that will readily break down in the environment.
Vinyl acetate is common in a variety of products, including paints, coatings, adhesives and sealants. Vinyl acetate is a common industrial monomer, and it is used to make homopolymers and copolymers that have a variety of applications. In its Evidence on the Carcinogenicity of Vinyl Acetate, OEHHA commented that “[v]inyl acetate-based polymers are used in adhesives and glues, paints, paper coatings, textile and leather finishing, plastics and resins, inks and lacquers, heat sealing films, pesticides, and cosmetics,” and that vinyl acetate and vinyl acetate-based polymers have been approved as food additives for food starch and chewing gum base.
Overview of Proposition 65
Prop 65 was enacted as a ballot initiative in November 1986, and is officially known as the Safe Drinking Water and Toxic Enforcement Act of 1986. Chemicals known to the state of California to cause cancer or reproductive toxicity are listed on what is known as the Proposition 65 List. Prop 65 prohibits businesses from knowingly discharging a listed chemical such that it will probably pass into drinking water (i.e., the Discharge Prohibition), and from knowing and intentional exposures to listed chemicals without first giving a clear and reasonable warning (i.e., the Warning Requirement).
Prop 65 is best known for its Warning Requirement, and Prop 65 warnings have become ubiquitous throughout California on products and in certain areas open to the public. This is partly due to Prop 65’s broad reach. For example, although the warning requirement only applies to businesses with ten or more employees, many manufacturers with fewer than ten employees have contracts with distributors or retailers that are subject to Prop 65 and require that the small manufacturer defend and indemnify those distributors and retailers from any claimed violation of Prop 65.
Beginning in January 2026, warnings for vinyl acetate may be required for exposures from consumer products, exposures due to contact with an environmental source such as ambient or indoor air, and exposures to an employee at their place of employment.
Although Prop 65 only requires that warnings be “clear and reasonable,” Prop 65 provides very little guidance on what is meant by “clear and reasonable.” Instead, OEHHA regulations provide that a warning will be “clear and reasonable” if it complies with the “safe harbor” warning methods and content. Although compliance with those “safe harbor” provisions is not required, many businesses choose to use this method to reduce the risk of enforcement. The cost to address alleged violations of Prop 65 is often significant.
Potential Compliance Challenges
Compliance with Prop 65 can be challenging, because the Warning Requirement applies to exposure to listed chemicals. Many laws prohibit a product from containing a specific chemical at a concentration over a certain threshold, and compliance can be based on relatively straightforward concentration testing to determine whether that threshold is surpassed. However, this strategy does not apply to Prop 65, where it is not the concentration level of the chemical at issue, but rather the level of human exposure to the chemical. For chemicals listed as carcinogens, such as vinyl acetate, to determine whether there is a prohibited exposure, businesses must demonstrate “no significant risk,” which is one excess case of cancer in an exposed population of 100,000, assuming lifetime exposure at
the level in question.
Although Prop 65 regulations provide some guidance on calculating “no significant risk” levels, the bases for such calculations are generally open to reasonable interpretation and may be the subject of dispute. Moreover, developing this potential defense generally requires extensive work by a team of experts, including a toxicologist.
Compliance for vinyl acetate may present additional compliance challenges, as exposure may occur through various pathways. Due to its chemical properties and common use, exposure may occur through inhalation, ingestion of food or water, or dermal contact in relation to consumer products, the workplace, or the environment.
In light of these potential compliance challenges, and with the January 2026 enforcement deadline less than six months away, companies would be well advised to begin considering compliance measures as soon as possible.
