The California Office of Administrative Law approved a No Significant Risk Level (NSRL) for styrene of 27 µg per day under the state’s Safe Drinking Water and Toxic Enforcement Act of 1986, also known as Proposition 65. Styrene was listed as a carcinogen under Proposition 65 on April 22, 2016, and the California Office of Environmental Health Hazard Assessment (OEHHA) proposed the NSRL at the same time. Comments on the proposed NSRL were accepted through June 6, 2016.

Proposition 65 requires companies to provide warning statements where their products cause an “exposure” to carcinogens and/or reproductive toxicants. The warning requirements do not apply when an exposure falls within the “safe harbor”—an NSRL for a carcinogen or a maximum allowable dose level (MADL) for a reproductive toxicant. The MSDL is the level at which a chemical would have no observable effect assuming exposure at 1,000 times that level.

The NSRL for styrene becomes effective on July 1, 2017, and will be listed in Title 27, California Code of Regulations, Section 25705. The notice about the NSRL for styrene, along with background information, including a final statement of reasons, can be found on OEHHA’s website.