On 22 April 2016, the Office of Environmental Health Hazard Assessment (OEHHA) is adding styrene the list of chemicals known to the state to cause cancer for purposes of the Safe Drinking Water and Toxic Enforcement Act of 1986 (Proposition 65). The listing of styrene takes into force effectively.

Chemical	CAS NO	Toxicological Endpoint	Listing Mechanism *
Styrene	100-42-5	Cancer	AB (NTP)

Styrene is widely employed in food contact materials, building insulation and composite products.
It is noted that products shall be attached with warning label as per Prop 65 if containing styrene. You can download the latest Proposition 65 List as below.
OEHHA has proposed to adopt a No Significant Risk Level (NSRL) of 27 micrograms per day for styrene. The NSRL represents the safe harbour level below which warning is not required under Prop 65.
C&K Testing advises businesses that Prop 65 should be dealt with for products to access California of the United States covering almost all industries. The conformity of Prop 65 shall be subject to ligations pr settlements. Businesses had better choose professional testing body for solutions.

Further information
Prop 65 List (updated to 22 April 2016)