California’s Office of Environmental Health Hazard Assessment recently added Δ9-tetrahydrocannabinol (THC) and “cannabis (marijuana) smoke” to the list of chemicals known to the state of California to cause reproductive toxicity, with an effective date of January 3, 2020.

California’s Safe Drinking Water and Toxic Enforcement Act of 1986, more frequently referred to as Prop 65, requires businesses whose products reach California consumers to notify consumers about the presence of certain harmful chemicals in consumer products. Companies have one year after a chemical is listed—in this case until January 3, 2021—to determine if warnings are required for their products and, if so, to post a proper warning (e.g., on the product label, a website, and/or a shelf sign).

As we previously reported here, marijuana smoke has been listed as a Prop 65 carcinogen since 2009. Although Prop 65 warnings already appear on many marijuana products, the new listing likely will require businesses to amend their warnings to address both cancer and reproductive toxicity.

And perhaps even more importantly, the new listing of THC will lead to a much wider range of cannabis products being subject to Prop 65’s requirements—namely edibles, tinctures, topical products, and other cannabis products that do not expose users to “smoke.” OEHHA has not established a safe harbor level for THC (i.e., a level of exposure that would not require a Prop 65 warning), so every business that sells a product with even a trace amount of THC—e.g., hemp-derived CBD products—could be affected.

As we explained in previous alerts (here and here) plaintiff groups have been extremely active on the marijuana front in the last couple of years, filing hundreds of Prop 65 notices of violation against businesses for failure to provide required warnings. We anticipate that this trend will continue—and grow—as additional cannabis-related products and businesses become subject to the law’s requirements on January 3, 2021.

The recent uptick in Prop 65 lawsuits against cannabis businesses highlights the importance of a fulsome Prop 65 compliance plan to reduce the opportunity for alleged violations proactively. A comprehensive compliance plan addressing the relevant laws and regulations, including but not limited to Prop 65, should help minimize the legal risk involved in operating businesses focused on cannabis consumer products.