title: Probabilistic approach to estimating indoor air concentrations of chlorinated volatile organic compounds from contaminated groundwater: a case study in San Antonio, Texas.
abstract: This paper describes a probabilistic model, based on the Johnson-Ettinger algorithm, developed to characterize the current and historic exposure to tricholorethylene (TCE) and tetrachlorethylene (PCE) in indoor air from plumes of groundwater contamination emanating from the former Kelly Air Force Base in San Antonio, Texas. We estimate indoor air concentration, house by house, in 30 101 homes and compare the estimated concentrations with measured values in a small subset of homes. We also compare two versions of the Johnson-Ettinger model: one used by the Environmental Protection Agency (EPA) and another based on an alternative parametrization. The modeled mean predicted PCE concentration historically exceeded PCE screening levels (0.41 ug/m(3)) in 5.5% of houses, and the 95th percentile of the predicted concentration exceeded screening levels in 85.3% of houses. For TCE, the mean concentration exceeded the screening level (0.25 ug/m(3)) in 49% of homes, and the 95th percentile of the predicted concentration exceeded the screening level in 99% of homes. The EPA model predicts slightly lower indoor concentrations than the alternative parametrization. Comparison with measured samples suggests both models, with the inputs selected, underestimate indoor concentrations and that the 95th percentiles of the predicted concentrations are closer to measured concentrations than predicted mean values.
authors.affiliation: Department of Environmental Sciences & Engineering, Gillings School of Global Public Health, University of North Carolina-Chapel Hill, CB 7431 Chapel Hill, North Carolina 27599, United States. jillj@unc.edu
authors.forename: Jill E
authors.initials: JE
authors.lastname: Johnston
authors.forename: Jacqueline MacDonald
authors.initials: JM
authors.lastname: Gibson
mesh_terms: D016902:Air Pollution, Indoor / Q000032:analysis* / Q000706:statistics & numerical data; D004784:Environmental Monitoring / Q000379:methods; D005618:Fresh Water / Q000737:chemistry; D015233:Models, Statistical; D013750:Tetrachloroethylene / Q000032:analysis*; D013781:Texas; D014241:Trichloroethylene / Q000032:analysis*; D035501:Uncertainty; D055549:Volatile Organic Compounds / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014877:Water Pollution, Chemical / Q000032:analysis / Q000706:statistics & numerical data
chemical_list: D055549:Volatile Organic Compounds; D014874:Water Pollutants, Chemical; D014241:Trichloroethylene; D013750:Tetrachloroethylene