The difference between exposure rate and chemical composition is one of the most common issues that comes up when discussing Proposition 65. While many people get that Prop 65 requires warnings for significant chemical exposures, there is a common misconception that Prop 65 prohibits products from even containing certain amounts of chemicals – lead, cadmium, and phthalates seem to be the prime culprit.
Unlike CPSIA, for example, there are no static composition limits for any chemical. Prop 65 only prohibits failing to provide a warning when exposure to the chemical is significant. Whether an exposure is significant depends on the product, the chemical, and a number of other factors, like human behavior.
Understanding the distinction between exposure and composition can go a long way to making informed choices for defense or compliance.
What is exposure?
Simply put, exposure is a measure of how much of the chemical in a product comes into contact with the consumer during use. Chemicals may get into a user through ingestion or inhalation – from eating it or from breathing it in. Chemicals may also come into contact with the consumer’s skin.
Further complicating matters, the question of significance of an exposure depends on the rate of exposure – that is, the amount of the exposure over a given time period. Generally speaking, this rate focuses on daily exposure (e.g., micrograms of chemical/day). OEHHA has established safe harbor exposure rates for a number of Listed Chemicals under which no warning is required, but a party may also undertake its own risk assessment to develop a no significant risk level if OEHHA has not or it does not use the safe harbor level.
Since people and products are different, Prop 65 seeks to determine the exposure rate for an “average consumer” when using the product in a reasonably anticipated way. Determining this rate usually requires a combination of scientific analysis of the product and chemical, as well as evaluation of human behavior. To win at trial, it typically requires expert testimony from a toxicologist.
For example, a plaintiff could allege a cabinet contains lead in components that consumers touch, requiring a warning. In defense, the cabinet manufacturer may argue that the lead is only in internal nails that the consumer will not touch during the reasonably anticipated use of the product. The manufacturer could also argue an insignificant exposure rate by establishing that the average user does not touch the nails in the cabinet door when using a cabinet, does not inhale, ingest, or absorb the lead through skin even after touching the cabinet, or does not touch the cabinet door frequently enough to ingest a significant amount of lead. To make these arguments, a manufacturer must have evidence (like a human behavior study that observes people opening and closing cabinet doors and putting their hands in their mouths). The plaintiff can challenge these positions with her own scientific studies.
What is composition?
In contrast to this complicated question of exposure, composition is simply a measure of how much of a chemical is in a product. This is determined through testing. The support plaintiffs cite for bringing Prop 65 cases almost always comes from composition analyses. Such analyses most often involve “wet chemistry tests” and “XRF testing.”
A wet chemistry test dissolves the product in a liquid solution to determine what percentage of the solution is the Listed Chemical, typically expressed in parts per million, or ppm (i.e., if you divided the product into one million parts, how many of those parts would be the chemical).
XRF tests use a handheld scanner that emits an X-Ray that disturbs the positions of the atoms in the object being tested. The scanner then measures the amount of energy given off as those atoms reposition themselves, using these energy measurements to determine the amount of Listed Chemical in the product. XRF testing is useful for screening, but is generally not considered reliable for precision composition testing.
Why does it matter?
Because determining exposure rates is so complicated, composition limits have become a proxy for exposure, especially in settlements. They’re basically a shortcut for plaintiffs to avoid exposure analyses for every product in a Prop 65 notice, and for manufacturers, suppliers, and retailers to gauge whether a warning is required without analyzing the product and how people use (or misuse) it. Over time, these composition limits get embedded in consumer products compliance culture, and sometimes no one even knows their origins.
The key when you get your next Prop 65 notice, or are evaluating a new product for the California market, is to remember that Prop 65 does not contain any composition limits – only warnings for significant exposures.