8.1 PAH Sources and Exposure
PAHs are ubiquitous environmental contaminants, originating from both natural and anthropogenic sources. Anthropogenic sources dominate, and include incomplete combustion of organic materials, notably carbon fuels such as coal or petroleum. Natural sources include volcanic eruptions and forest fires. PAHs are distributed widely in the environment, generally as complex mixtures, and concentrations are often elevated in urban soils due to the presence of such mixtures. Exposures to these mixtures can occur through inhalation, ingestion, and dermal contact.