Bare JL, Abramson MM, Maskrey JR, Manning CM, Keenan JJ. 2018. Proposition 65 risk assessment model framework for chemically-complex consumer products. Abstract #3525. Poster Presentation at Society of Toxicology (SOT) Annual Meeting, San Antonio, TX, March 2018.
California’s Safe Drinking Water and Toxic Enforcement Act (Prop 65) mandates that a warning label be displayed on a consumer product when a person may be exposed to one or more chemicals listed by the State as carcinogenic or a cause of reproductive toxicity at a level greater than the safe harbor levels (SHLs). Companies are not required to provide a warning label if exposures to the listed chemical(s) are below the SHLs, which may be determined by the State or the company. Many consumer products contain multiple listed chemicals and exposures may occur during many consumer uses. We present a risk assessment model framework that can be used to estimate exposures to consumer products with complex chemical compositions and exposure scenarios. As a case study, two exposure scenarios were modeled: 1) exposure to benzene from filling a five gallon container with a petroleum product containing 100 ppm benzene over the course of ten minutes, 25 times per year, 2) exposure to lead from filling a one gallon container with a petroleum product containing 10 ppm lead over the course of five minutes, 50 times per year. In the case study, near-field inhalation exposure was modeled for evaporation of benzene during product pouring and evaporation from the product on the consumer’s hands after product use. Dermal absorption was modeled for both benzene and lead by assuming 25% of each hand was covered in the petroleum product. Subsequent direct and indirect hand to mouth ingestion exposure for benzene and lead were estimated for a scenario in which the consumer ingested the product covering an area of five fingertips. A mass balance control was implemented to ensure that the cumulative exposure mass did not exceed the mass available in the product. Cumulative daily exposures to benzene and lead were estimated to be 29.8 and 0.485 µg/day, respectively. Daily doses averaged over a lifetime were estimated to be 2.04 and 0.066 µg/day for benzene and lead, respectively. All exposures were below the SHLs and the mass balance was satisfied. Although there are inherent uncertainties associated with this risk assessment model, exposure concentrations are estimated using conservative assumptions based on Prop 65 and USEPA resources and peer-reviewed literature. This model framework is valuable for estimation of risks associated with metals and volatiles in consumer products, and may be adapted to address a wide range of consumer products and chemical mixtures.