Delta-9 THC—the compound in cannabis that gets you high—is being added, under certain circumstances, to the list of nearly 900 chemicals in the state of California’s Prop. 65 warning regime.

Prop. 65 warnings have become near-ubiquitous. Its original intent was to protect consumers from potentially tainted drinking water, but has almost become a caricature, with warning labels on rental cars, playground equipment and faux leather jackets. For a while, in 2018-19, it was added to coffee because of acrylamide content in roasted coffee beans before being removed when it was deemed the acrylamide dose in coffee is too low to be a legit carcinogen.

The Prop 65 regulations apply to naturally occurring chemicals in foods. In January 2020, THC was added to the list of chemicals known to the state of California to cause reproductive harm. In August 2022, the THC regulation was tweaked to mean cannabis (marijuana) smoke and delta-9 THC.

The new Prop. 65 regulation, the California’s Office of Administrative Law, was adopted in August and provides specific safe harbor exposure warning methods of transmission and content for retail products that can expose consumers to delta-9 THC via inhalation, ingestion or dermal application, as well as exposures to cannabis (marijuana) smoke.

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The regulation is effective Oct. 1, 2022, and includes a one-year phase-in period and an unlimited sell-through provision for products manufactured and labeled with compliant warnings before Oct. 1, 2023.

“Importantly, the listing does not provide a safe harbor level, and therefore any amount of delta-9 THC—including hemp-derived delta-9 THC below 0.3 percent—may trigger the warning requirement,” said Rend Al-Mondhiry, an attorney specializing in hemp for the Amin Talati Wasserman law firm, based in Chicago. “In addition, the regulation prohibits the use of the general short-form warning for delta-9 THC exposure. The warning symbol must also accompany the safe harbor warning content.”

The regulations noted that the California law governing hemp, AB 45, “does not establish that delta-9 THC in certain hemp products is naturally occurring for purposes of Proposition 65.”

The businesses relying on Prop. 65 “would have the burden of showing the product is a food or derived from a food and that the THC in that product is naturally occurring and thus would not require a warning,” according to a response to a comment made by the American Herbal Products Association from the California Office of Environmental Health Hazard Assessment.

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“The proposed regulations do not specify when a warning is required, instead they provide safe harbor methods and language for warnings where a business determines one is needed,” wrote OEHHA.

The agency has determined that the term “unquantifiable” is the most appropriate term to use to indicate when a CBD product containing delta-9-THC may not require a warning.

That sounds like CBD isolates can keep on rolling, said Al-Mondhiry, but full-spectrum hemp CBD products, which contain various amounts of delta-9 THC, may be subject to the rule and thus a warning on product packages.