No Significant Risk Level (NSRL)

A No Significant Risk Level (NSRL) is the safe harbour exposure level established by OEHHA for chemicals listed as carcinogens under Proposition 65. Below the NSRL, a business is not required to provide a Proposition 65 cancer warning. The NSRL is set at the level of exposure that would cause no more than one excess case of cancer in 100,000 individuals exposed over a 70-year lifetime. Key NSRLs include: lead: 15 μg/day; acrylamide: 0.2 μg/day; arsenic: 10 nanograms/day; benzene: 12.7 μg/day; cadmium: 0.05 μg/day (tobacco); styrene: 27 μg/day. NSRLs are published in Title 27 CCR §25703 and OEHHA’s Proposition 65 list.

California Health & Safety Code §25249.10; Title 27 CCR §§25701–25723 (NSRL methodology); §25703 (specific NSRLs); OEHHA Proposition 65 list (Excel).

The NSRL is the critical threshold for carcinogen warnings. If a product exposure assessment demonstrates that the daily intake of a listed carcinogen is below the NSRL, no warning is required. Businesses must either conduct product-specific exposure assessments or reformulate to bring carcinogen exposure below the NSRL. Many NSRLs are extremely low (in micrograms or nanograms per day), making testing sensitivity and exposure pathway accuracy critical factors. OEHHA’s exposure calculation tools can assist in determining whether product use results in exposures above or below the NSRL.