Biomonitoring

Biomonitoring refers to the measurement of the body burden of a chemical in biological media (blood, urine, tissue, breast milk) to assess actual human exposure levels. In the Proposition 65 context, OEHHA uses biomonitoring data when available to estimate actual exposure levels and derive safe harbor thresholds. Under California’s Biomonitoring Program (SB 1379), OEHHA and the California Department of Public Health conduct population-level biomonitoring studies. Biomonitoring data can be relevant evidence in Proposition 65 enforcement litigation when demonstrating that actual exposure to a listed chemical is below the NSRL or MADL.

California Health & Safety Code §25249.10 (exposure assessment); OEHHA toxicological guidance documents; California Biomonitoring Program (Health & Safety Code §125000 et seq.).

For businesses defending Proposition 65 actions, human biomonitoring data showing that average population exposures to the relevant chemical are below the NSRL or MADL can support a defence that exposure is not ‘significant.’ Product-specific biomonitoring studies (e.g., showing that consumer exposure from a specific product is below the safe harbour level) can also support a safe harbour defence. Biomonitoring is particularly relevant for chemicals found in food, personal care products, and consumer goods.