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/m 3 , of which 0 to 4.6% was BTEX and 90 to 95% was hydrocarbons of the C 5-8 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 C 5-8 and C 9-10 aliphatic and C 9-10 aromatic fractions relative to benzene and the TEX aromatic fraction. This work has shown that the C 5-8 and C 9-10 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.

The Toxicology of Chemical Mixtures Risk Assessment for Human and Ecological Receptors

“…HQs are summed for each exposure route HI; measured site concentrations are extrapolated to predicted exposure concentrations for some routes using simple fate and transport models (MA DEP, 2003 Washington (Reed and Sterner, 2004). This procedure has also been used successfully in the United Kingdom (Clay and Harris, 2002) while Canada has its own similar procedure (Sevigny et aL, 2003).…”