Inverse Groundwater-Plume Modeling Applied to Dose Reconstruction

By Peter M. Mesard, P.E., C.E.G.

In toxic tort claims, questions often arise regarding exposure of individuals (receptors) to chemicals of potential concern (COPCs). In these cases, the concentration of the COPCs in an environmental medium that a receptor has been in contact with (termed the “dose”) is a key component in assessing the amount of the chemical that may have entered the body via dermal absorption, ingestion, or inhalation. However, if the exposure occurred in the past, and records of direct measurements of COPC concentrations are not available, it is necessary to estimate historical concentrations, which requires a dose reconstruction approach.

This Environmental Forensics Note presents the application of inverse groundwater-plume modeling to estimate past concentrations of volatile COPCs in groundwater and soil vapor, which could have historically exposed a receptor to those COPCs via two pathways—drinking water and soil vapor intrusion. A hypothetical setting of a rural neighborhood downgradient from a release is used to illustrate this dose reconstruction approach.

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