Graduate Thesis Or Dissertation

A human health risk assessment of hazardous air pollutants in Portland, Oregon

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  • In 1990, the Clean Air Act (CAA) Amendments authorized the regulation of 188 hazardous air pollutants (HAP). Exposure to HAPs at sufficient concentrations and durations can increase both cancer and serious adverse non-carcinogenic effects. The purpose of this study was to conduct a human health risk assessment using data of 43 HAPs from five monitor sites in Portland, Oregon during July 1999-August 2000. HAP concentrations were compared to carcinogenic and non-carcinogenic (health) benchmark concentrations; and emission sources were determined for HAPs that exceeded health benchmark concentrations. Additionally, cancer risks were determined for subpopulations and compared to cancer risks generated for the general population. Results of this study indicate that 20 HAPs exceeded carcinogenic benchmark concentrations (corresponding to a risk level of 1 x 10⁻⁶) in at least one location. Chromium compounds posed the highest cancer risk (3.5 x 10⁻⁴). Seventeen HAPs exceeded carcinogenic benchmark concentrations at all five sites. Seventy-five percent (%) of the total cumulative cancer risk was contributed by chromium compounds, 1,3-butadiene, formaldehyde and 1,1,2,2-tetrachloroethane. Three HAPs, chromium compounds, acrolein, and formaldehyde, exceeded non-carcinogenic hazard ratios of 1.0. Releases from area sources accounted for the largest percentage of HAPs that exceeded health benchmark concentrations. With respect to subpopulations, asthmatics teenagers (age 11-16) and asthmatic adults (age 18-50), had slightly elevated cancer risks of 1.4 x 10⁻⁶ and 1.2 x 10⁻⁶. respectively, compared to the general population risk level of 1 x 10⁻⁶. Results of this study indicate that several HAPs pose a potential human health concern in Portland and that efforts should be made to reduce their emissions. Additional studies are warranted to further assess potential human health risks and the extent of HAPs in Portland, Oregon.
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