Health Assessment of Polycyclic Aromatic Hydrocarbon Mixtures: Current Practices and Future Directions

The U.S. EPA's Integrated Risk Information System (IRIS) program has initiated a health assessment for polycyclic aromatic hydrocarbon (PAH) mixtures. The IRIS program develops EPA consensus scientific positions on potential human health effects from chronic exposure to chemicals. Currently, the IRIS database contains health assessments for the toxic effects of exposure to coke oven emissions, creosote, diesel emissions, and 15 individual PAH compounds. As a whole, these assessments do not consider issues related to the environmental occurrence of PAH compounds as complex mixtures. Risk assessment of PAH mixtures has been hindered by a lack of information on the composition and toxicity of specific mixtures, the components that contribute most to toxicity, and the interactions and differences in mode of action between components. The state-of-the-science has advanced considerably in the past decade and will play a key role in the development of the health assessment. Consideration of these issues led to an EPA-sponsored Workshop on Approaches to PAH Health Assessment in October 2001. The current practices of the EPA regarding the health assessment of PAH compounds and future directions of the agency are discussed in this article.