Development of Human Health Risk Model and Validation for Indoor Air Exposure to Hydrocarbons. L. A. Rodricks and J. Caron, CH2M Gore and Storrie, Ltd., Ontario, Canada; and M. Adomait, Adomait Environmental Solutions Inc., Ontario, Canada
A utility company in Ontario was interested in evaluating the human health risks at two of their urban located facilities. The primary pathway of concern was the migration of soil vapor indoors. Indoor air concentrations and endpoint risks were calculated using transport equations developed by Johnson and Ettinger. The model results were compared against results based on the Ontario Environmental Agency dilution factor established from several probabilistic analyses. The identification of unacceptable risks using both models prompted the utility company to validate the model with measured data. Fourteen weeks of contaminated air transport related measurements were performed. This program measured real time total organic hydrocarbons, barometric pressure fluctuations, soil gas pressures, air exchange rates and discrete chemical concentrations from indoor air, outdoor air and subsurface soil vapor. Based on the program results, a cost effective risk methodology was developed which assess the need for measurements and modeling. A more complete risk model was developed, which incorporates ubiquitous sources, meteorological contributions, facility design, and soil gas pressures into the Ontario Environmental Agency process when establishing end-point risks.
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