Using Uncertainty Analysis to Reconstruct Historical Tetrachloroethylene (PCE) Exposure for an Epidemiological Study

Health scientists and epidemiologists rely on groundwater flow and fate and transport models for reconstructing historical exposures to contaminants such as tetrachloroethylene (PCE) when conducting environmental health studies. Of concern to epidemiologists is the reliability of historical estimates of the spatial and temporal distribution of contaminants used in determining exposures. Thus, evaluation of uncertainty and variability of hydraulic and transport parameters should be assessed as part of the overall exposure assessment process. In a health study of historical exposure to PCE-contaminated drinking water at U.S. Marine Corps Base Camp Lejeune, North Carolina, (1) uncertainty analyses were conducted; (2) probability density functions were generated for hydraulic and transport parameters using Monte Carlo and Gaussian sequential simulation; and (3) the related probabilistic analyses were incorporated into the MODFLOW and MT3DMS simulation codes.