Exposure Assessment

An exposure assessment is the quantitative or qualitative evaluation of the actual amount of a listed chemical that an individual is exposed to from a specific product, facility, or activity. Under Proposition 65, a warning is required only when exposure exceeds the applicable safe harbour level (NSRL for carcinogens; MADL for reproductive toxicants). OEHHA provides guidance on calculating exposure levels, including its ‘Proposition 65 Exposure Calculator,’ and technical guidance documents specifying default exposure assumptions (e.g., body weight, inhalation rates, dermal absorption factors, ingestion rates). Businesses may use product-specific exposure data to demonstrate that exposures do not require warnings.

California Health & Safety Code §25249.10 (safe harbour); OEHHA Proposition 65 Exposure Calculator; OEHHA Technical Support Documents; Title 27 CCR §25711–25721.

Exposure assessment is the core technical tool for determining whether a Proposition 65 warning is required. If a product’s exposure to a listed chemical exceeds the NSRL or MADL, a warning is required (or the product must be reformulated). Businesses should conduct documented product-specific exposure assessments using OEHHA’s published methodologies and default assumptions. Where product-specific data show lower exposure than OEHHA defaults, businesses can use these data to demonstrate that no warning is needed. Third-party toxicologists are often engaged to conduct and document these assessments.