Author: Peter B. Harnett, MS, MPH, CIH. Peter founded COEH in 1992. He has conducted numerous exposure assessments and frequently works with attorneys on exposure assessment issues in toxic torts cases. Peter received some assistance on this article from Drs. David Schwartz and Giovanni Ciavarra with ISS, www.innovativescience.net
Nobody on site collected and recorded occupational or environmental data measuring air, soil, surface or ground water levels of possible chemical contaminants. Now you’re left with a big question mark: What level of exposure did the plaintiff actually experience?
Enter the scientist who begins the search for information that can shed some light on the exposure levels. The scientist will likely use the following approaches, depending on case-specific circumstances:
- Employ models to estimate past chemical exposure based on the amount of a chemical used in an operation or the size of a spill or release
- Research the scientific literature to uncover exposure data for a similar set of circumstances involving the specific agent or a suitable surrogate. For example, if the plaintiff is alleging injury from an airborne occupational exposure to a specific volatile organic compound (VOC) with no available data, the scientist could find airborne concentrations for a VOC with a similar vapor pressure. Based on the surrogate’s emissions rate and the spill volume in a room (for which the dimensions and ventilation rate are known), the scientist could then calculate an estimate of the airborne exposure to the specific VOC. The scientist would take into account the surrogate’s properties as well as the work area where the alleged exposure occurred.
- Enlist the help of an expert. The right expert will be highly proficient in conducting an exposure assessment to evaluate existing data and developing an action plan to deal with a lack of historical data. The type of expert required will depend on the nature of the exposure.
Following are a few examples:
- Airborne chemical exposure: industrial hygienist, air dispersion modeler.
- Dispersion of soil particulates in air or volatilization of chemicals from soil to air: soil scientist, air dispersion modeler.
- Surface water contamination resulting in ingestion, dermal contact, or inhalation: environmental scientist specializing in multimedia partitioning of chemicals from water to air and potentially air to water, or ecotoxicologists to assess data from fish or plants that may have been adversely affected.
- Ground water contamination in which a chemical moves from soil, sediment, surface water to ground water and plume (portion of ground water containing the chemical) movement must be determined: hydrogeologist, geologist, industry-specific expert (e.g.; gas-drilling experts in the case of hydraulic fracturing contamination allegations).
To illustrate how an expert can provide key insight, let’s look at the third example, ground water contamination, more closely. A chemical agent does not distribute equally to all ground water in a given area. If the chemical was introduced to the ground water at point X and the plaintiff lives in the direction indicated by plume movement, we could expect past, present and future exposure to the chemical in the ground water if the plaintiff uses the ground water. Hydrogeologists can determine the likely levels of exposure based on the amount of the chemical introduced into the ground water, the rate of plume movement, the amount of ground water, and other factors. Geologists and drillers can play an important role in the process of defining the extent of the chemical contamination of the ground water by installing monitoring wells to determine the chemical concentration over time. These monitoring wells can provide current chemical concentrations and determine ongoing concentrations for future use.
If the scientific research and expert analysis indicate very low or no exposure to the chemical in question, the information will strengthen the defense’s case. But if the information supports the likelihood of a significant exposure, the defense may consider alternate strategies.