A study published on February 12, 2025, in Environmental Science & Technology, suggests that California’s right-to-know law, Proposition 65, extends beyond consumers and impacts industry decisions about using known toxics in manufacturing.
Established in 1986, Proposition 65 requires companies in California to disclose and label products that contain chemicals known to be mutagenic, carcinogenic, or demonstrate reproductive toxicity. The Proposition 65 list, which is managed by the State of California’s Office of Environmental Health Hazard Assessment (OHHA), currently includes approximately 900 substances. While research has been conducted on the effects of Proposition 65 on consumer behavior, little has been known about its influence on companies.
For this research, Jennifer Ohayon and colleagues at the Silent Springs Institute, Massachusetts, USA conducted 32 interviews with large retailers and manufacturers. The sectors represented included cleaning, personal care, health and health care, electronics, pesticides, apparel, home improvement, chemicals and raw materials, automotive, flooring, fragrances, and education.
In 78% of cases, interviewees said they reformulated products due to Proposition 65. Rather than limiting chemicals to the safe harbor levels outlined in the legislation, 41% of interviewees chose to eliminate the listed chemicals from their products. One reason cited for this practice was a lack of clarity in Proposition 65 regarding how safe harbor levels translate to chemical concentrations in products, raising the potential for enforcement through civil lawsuits (FPF reported). The researchers propose that, as a result, Proposition 65 is having public health impacts beyond its original intent.
The Proposition 65 list is regularly updated based on the latest health evidence (FPF reported). For example, the OHHA added a reproductive toxicity endpoint for bisphenol S (BPS) effective January 3, 2025. BPS was previously included on the list as a reproductive toxicant in females, and the new endpoint recognizes its toxicity in males as well. Companies have one year to add warnings when exposing Californians to BPS. Interviewees in Ohayon’s study revealed that, despite this grace period, they often try to anticipate these updates and modify formulations accordingly.
Interviewees also described how they apply Proposition 65 to improve transparency in the supply chain. Of those interviewed, 81% use Proposition 65 as an authoritative list of hazardous chemicals to avoid when purchasing from suppliers, and 69% use Proposition 65 to request ingredient information from their suppliers. Several interviewees mentioned that they had dropped suppliers that were unresponsive to changing formulations to remove Proposition 65-listed chemicals. Feedback from interviewees highlighted that these practices within larger companies have the potential to shift formulations for entire industries based on demand from suppliers.
References
Ohayon, J.L., et al. (2025). “How a Right-to-Know Law Shifts Industry away from Chemicals of Concern: The Case of California’s Proposition 65.” Environmental Science & Technology. DOI: https://doi.org/10.1021/acs.est.4c07495
California Office of Administrative Law (January 3, 2025). “California Regulatory Notice Register.”
Read more
Amudalat Ajasa (February 12, 2025) “California’s chemical warning labels are everywhere. A study finds they’re working.” The Washington Post
