Polyaromatic Hydrocarbon Content in Crude Oils Around the World

Polyaromatic hydrocarbons (PAHs) are of environmental concern because a few of them have been found to be mutagenic and/or carcinogenic at some dose levels in laboratory studies. For this reason, 16 PAHs are on the U.S. Environmental Protection Agency's Superfund Amendments and Reauthorization Act (SARA) Priority Pollutant list (U.S. EPA 1987). PAHs consist of two or more fused benzene rings in linear, angular, or clustered arrangements. They are naturally occurring in crude oils and therefore may be of concern at crude oil spill sites and in some types of E&P wastes. There are many sources of PAHs in the environment with incomplete combustion of fossil fuels (including coal and oil) being a major source of low concentrations of PAHs worldwide. Some other environmental sources of PAHs are natural oil seeps, spills of refined products, and wood preservatives such as creosote. Exxon Production Research and Chevron Research and Technology as participants in a joint industry effort through the Petroleum Environmental Research Forum Project 97-08 have analyzed over 48 crude oils, exploration and production (E&P) wastes, and site soils from across the world. In this paper, information regarding PAH content and concentration is compared to the composition of some refined products, creosote, and combustion sources. The potential risk to human health from PAHs in crude oils is also addressed. Preliminary assessments were conducted to determine the concentrations of these crude oils in soil for which human health risk from PAH exposure was acceptable. The concentrations determined from these assessments were compared to total petroleum hydrocarbons (TPH) cleanup criteria targets of 10,000 ppm, as used by several states. For all oils tested, the cleanup standard of 10,000 ppm was protective of human health with a considerable safety factor.