Importance of Different Volatile Petroleum Hydrocarbon Fractions in Human Health Risk Assessment

Abstract

Soil vapor data for benzene and four aliphatic and aromatic hydrocarbon fractions from five volatile petroleum hydrocarbon (VPH)-contaminated sites in western Canada were used together with the Canadian Council of Ministers of the Environment (CCME) Canada-Wide Standard for petroleum hydrocarbons to investigate the relative importance of benzene and the different fractions in human health risk assessment. VPH concentrations in soil vapor samples ranged from 4.0 to 4200 mg/m3, of which 0 to 4.6% was BTEX and 90 to 95% was hydrocarbons of the C5–8 aliphatic fraction. VPH inhalation exposure by an adult receptor in a hypothetical, commercial building was modelled deterministically assuming 16- and 70 year occupational tenures. The magnitude of hazard quotients varied widely between sites, but their hydrocarbon fraction signatures were consistent, and characterized by higher hazard quotients in the C5–8 and C9–10 aliphatic and C9–10 aromatic fractions relative to benzene and the TEX aromatic fraction. This work has shown that the C5– and C9–10 aliphatic fractions yield greater relative risk than the commonlyregulated TEX compounds, and that benzene becomes the primary chemical of potential concern only when an occupational tenure approaching 70 years is assumed.