Two New Chemicals Added to the Prop 65 List

The plastic, synthetic textile, and wild mushroom industries should beware of two new additions to California’s Prop 65 list that may heighten these businesses’ duty to warn.

California’s Prop 65 list is a list of chemicals known to the state to cause cancer and/or reproductive harm. To be compliant with Prop 65, manufacturers, sellers, distributors, packagers, and deliverers must clearly and obviously label products known to contain chemicals on the Prop 65 list. These warning label must include, in writing, the Prop 65 chemical in the product, it’s inclusion on the Prop 65 list, and the type of harm identified by the state – namely: cancerous, developmental or reproductive.

Failure to label correctly under Prop 65 allows individual consumers to bring civil lawsuits for monetary damages against businesses who do not, or improperly label under Prop 65. On products and places in California known to contain Prop 65 list chemicals, business owners have this heightened liability standard in any product liability litigation. Additionally, violating businesses will be penalized with steep, daily accruing fines for violations of Prop 65’s warning requirements.

The two new chemicals added to California’s Prop 65 list were Bisphenol S (BPS) and N-Methyl-N-Formylhydrazine (NMNF).

Bisphenol S (BPS) is used to make up plastics and synthetic fibers in synthetic textiles. It was first added to California’s Prop 65 list in January of 2025 as a reproductive toxin for males. However, towards the end of last year on December 5, 2025, Bisphenol S (BPS) was cross-listed to also be a developmental toxin.

To check if your plastic or synthetic textile business uses this chemical, Bisphenol S’s Chemical Abstracts Service Registry Number (CAS No.) is 80-09-1.

N-Methyl-N-Formylhydrazine (NMNF) is a chemical compound released when Gyromitra mushrooms, more commonly known as “false morels” come into contact with warm water. The NMNF chemical is released from the wild mushrooms when warmed in water, contaminating the water thereafter. NMNF made the Prop 65 list on December 5, 2025 as cancer-causing toxin.

To check if your product contains mushrooms that release this chemical, N-Methyl-N-Formylhydrazine Chemical Abstracts Service Registry Number (CAS No.) is 758-17-8.

In the new year, Prop 65 will now require businesses who handle these chemicals to place warning labels on their products, workplaces, businesses, or rental housing if the business is aware or believes that it is exposing individuals to these, or other listed chemicals.

To protect against violations of Prop 65, we recommend that clients check the Prop 65 list periodically, if not at least annually, to ensure compliance with ever changing laws and regulations.