ESTIMATING INDOOR AIR EXPOSURE TO VOCS FROM SUBSURFACE RELEASES - FIELD METHODS AND MODEL LIMITATIONS

摘要

Exposure to carcinogenic volatile organic compounds (VOCs) poses a potentially significant risk due to vapors associated with migrating subsurface releases of chlorinated solvents. The evaluation of the cancer risk associated with subsurface releases is generally estimated using fate and transport models adopted by the USEPA, i.e., Johnson-Ettinger model. Field verification of the Johnson-Ettinger model has identified that it underestimates exposure concentrations up to 1000 times especially through the use of default parameters. The model is characterized as a non-deterministic numerical model that requires evaluation of site-specific parameters and performance of sensitivity analyses. Field methods have been developed and tested that result in more reliable exposure evaluation techniques. Data from field studies in varying soil and atmospheric conditions have been evaluated to generate more representative estimates of exposure concentrations.