On September 21, 2026, California's Office of Environmental Health Hazard Assessment (OEHHA) released a pre-regulatory package proposing two amendments to Proposition 65 rules for vinyl acetate: a no significant risk level (NSRL) of 11 micrograms per day (11 µg/day) in Title 27, California Code of Regulations, section 25705(b), and a new section 25901 governing how private enforcers must measure vinyl acetate exposure to support a Certificate of Merit. Vinyl acetate, a monomer used to make polyvinyl acetate (PVA), ethylene-vinyl acetate (EVA), polyvinyl alcohol and related polymers, has been listed as a Proposition 65 carcinogen since January 3, 2025, but until now carried no safe harbor level.
OEHHA will discuss the draft at an online workshop on September 30, 2026, from 10:00 to 11:30 am PST, and accepts written comments through October 21, 2026. The agency stresses the text is a pre-regulatory draft for discussion only and could change substantially before any formal rulemaking.
What safe harbor does the 11 µg/day NSRL create, and is it mandatory?
The NSRL gives businesses a voluntary safe harbor: a daily exposure at or below 11 µg/day of vinyl acetate is deemed to pose no significant risk, so no Proposition 65 warning is required. It is not a cap and not a duty. A business may instead rely on its own risk assessment under section 25701(a). Above 11 µg/day the safe harbor falls away, and the business must either provide a warning or be ready to prove the exposure poses no significant risk, defined in section 25703 as one excess cancer case per 100,000 people over a lifetime.
According to the draft regulatory text and explanatory document, OEHHA derived the value from the most sensitive rodent study deemed of sufficient quality: a female F344 rat drinking-water study (EPL 1982; Lijinsky and Reuber 1983) that showed uterine adenocarcinomas, endometrial stromal polyps, hepatocellular adenoma, thyroid C-cell adenoma and pituitary adenoma. Multisite dose-response modeling in US EPA Benchmark Dose Software yielded a human cancer slope factor of 0.065 per mg/kg-day. Applying the Proposition 65 one-in-100,000 risk benchmark (10 to the power of minus 5) and a 70 kg adult body weight produces 11 µg/day. OEHHA relied on its 2024 carcinogenicity evidence document and IARC Monograph Volume 63 (1995).
What does new section 25901 mean for polymer converters?
This is the provision with the sharpest commercial edge. Under Health and Safety Code section 25249.7(d), a private party suing over a missing warning must attach a Certificate of Merit, certifying that an expert reviewed the facts and believes the case is meritorious, and must serve the supporting factual information on the Attorney General. Proposed section 25901 says those facts must show exposure to the listed vinyl acetate monomer, CAS no. 108-05-4. Critically, if a product test is used to set a monomer concentration, that concentration must not include vinyl acetate monomer released by breaking down vinyl acetate-containing polymers in a manner that would not otherwise occur during a consumer product exposure, as defined in section 25600.1.
The rationale matters. Only the vinyl acetate monomer is listed under Proposition 65, not PVA, EVA, polyvinyl alcohol, polyvinyl acetals or the other polymers and copolymers, and the monomer is uncommon in finished consumer goods apart from residual unreacted monomer. A test that aggressively cleaves polymer bonds could manufacture an exposure reading that does not exist in real use. For converters making adhesives, paints, paper coatings, textiles, plastics, inks, lacquers or cosmetics sold into California, the rule narrows the room for bounty-hunter suits built on misleading headspace or forced-degradation testing.
Who needs to act, and by when?
Vinyl acetate monomer producers, PVA, EVA and polyvinyl alcohol converters, and brands selling adhesives, paints, coatings, packaging, inks or cosmetics into California should treat the October 21, 2026 comment deadline as the decision gate. The September 30 workshop is the first chance to shape both the NSRL derivation and the testing-method language before OEHHA commits to a formal rulemaking, where additional comment rounds will follow. Proposition 65 plaintiff labs have a stake too, because section 25901 tightens what a Certificate of Merit must contain.
| Obligation | Today | Under the proposal |
|---|---|---|
| Safe harbor level | None for vinyl acetate; do your own risk assessment or warn | NSRL of 11 µg/day in 27 CCR 25705(b); voluntary |
| Certificate of Merit testing | No monomer-specific analytical rule | Must show CAS 108-05-4 monomer; exclude polymer-breakdown monomer |
| Listing status | Listed for cancer since January 3, 2025 | Unchanged |
| Next milestone | Notice posted September 21, 2026 | Workshop September 30; comments due October 21, 2026 |
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For your immediate checklist: confirm whether your products' vinyl acetate monomer exposure sits above or below 11 µg/day, so you know whether the safe harbor helps you; audit your residual-monomer test methods to make sure they do not artificially break down PVA, EVA or other vinyl acetate polymers; submit comments by October 21, 2026 and register for the September 30 workshop; and brief product stewardship and counsel now, because the testing-method language will shape litigation risk long before a final rule lands. Continuous, per-jurisdiction monitoring surfaces a pre-regulatory draft like this the day OEHHA posts it, which is exactly when influence is cheapest.
