Dose reconstruction is the determination of historical doses, whether by inhalation, ingestion, or entry through the skin. Doses depend on the current concentration levels, in air, water, soil, food, and other media and duration and frequency of exposure. If concentration data are available for the time period and location at which exposure is being claimed, estimating exposure and dose for each chemical is straightforward. However, for exposures that occurred historically, often this information is not available.
Exponent has used a variety of assessment tools to gather data to reconstruct and characterize historical exposures. These include:
- Extrapolations to historical conditions based on current data and conditions
- Factors representing differences between historical and current conditions (e.g., use of differences in ventilation conditions and air exchange rates between the historical and current work facility conditions
- Mathematical modeling of historical exposure conditions (e.g., use of emission and dispersion models to estimate chemical concentrations in air under specific historical conditions)
- Exposure simulations of historical conditions and collection of industrial hygiene data (e.g., tests of chemical releases from historical products under controlled conditions)
Using these methods, Exponent has calculated the historical chemical dose to which persons that worked certain jobs or used specific products were exposed.
Exponent has published dose reconstruction assessments for automobile and truck mechanics, workers using part washing solvents, and persons using roof repair products.