Winter 2021

Exposure Scenarios Under Prop 65

By Rosemary Mattuck, M.S.

California’s Proposition 65 is focused on exposure potential rather than the chemical content of a product.

California’s Proposition 65 (“Prop 65”) requires that a clear and reasonable warning be provided to the consumer if use of a product may result in exposure to a chemical known to the State of California to cause cancer or reproductive harm.  The key concept here is that the law deals with “exposure” to chemicals, rather than the chemical content of a product.  Exposure describes the amount of chemical that may be taken into the body through use of the product.  Routes of exposure can include ingestion (from either mouthing the object or hand-to-mouth behavior), dermal absorption, or inhalation of volatile chemicals.  Product testing is therefore focused on relevant product exposures; for example, a wipe test is helpful to evaluate hand-to-mouth exposures, while a leaching test in artificial saliva may be used for a mouthing scenario.  About 320 chemicals on the Prop 65 list have a “Safe Harbor Level,” given in micrograms per day.  If use of the product results in an exposure that is less than the Safe Harbor Level, the product does not require a warning.

Given the diverse array of products on the market, formulating exposure scenarios can be a robust undertaking.”

The California Office of Environmental Health Hazard Assessment (OEHHA) provides some guidance but does not provide prescriptive methods for determining the amount of exposure to chemicals from use of a product.  An exposure assessment should consider how the product will be used and assess exposures for an average or typical user of the product, who uses the product as intended.  For example, one could assess phthalate exposure from handling a plastic pen but would not need to assess exposure from chewing on the pen, as that is not its intended use.  Assessing exposure from food products is relatively straightforward, based on the concentration in the food and the typical serving size, although determining typical servings per day often requires a bit of research.  Non-food products present more of a challenge, as one must formulate a reasonable product-use scenario in order to calculate exposures.  Take for example a brass lamp, for which lead exposure is to be evaluated.  The scenario in this case is touching the lamp, followed by ingestion of lead from hand-to-mouth activity.  A wipe test is used to help evaluate the amount of lead that could adhere to the skin from touching the lamp.  Other inputs needed are the surface area of the hand that touches the lamp and the exposure frequency (i.e., the number of times a day that the lamp is touched).  Obviously these inputs will vary, depending on where the lamp is, who is using it, and how often, and there is no one right answer.

One must propose a scenario that is both plausible and defensible based on the particular product.  Given the diverse array of products on the market, formulating exposure scenarios requires some ingenuity.  For example, to assess heavy metal exposure from artificial turf, key considerations are who plays on the field, how old they are, how often their hands touch the ground, and how long and how often they attend practice.  To evaluate a PVC-based tool, off-gassing tests should be used to assess inhalation exposure to vinyl chloride, in addition to wipe tests to evaluate ingestion exposure, together with an estimate of how often the tool will be used.  In summary, an exposure scenario should use reasonable assumptions for how the consumer will use the product, and testing methods that are appropriate to quantify chemical exposures.

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