Human Exposure to Polycyclic Aromatic Hydrocarbons in Urban and Rural Ambient Air

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous organic compounds in the ambient air. They are composed of two or more fused benzene rings and emitted into the atmosphere after incomplete combustion of organic material and evaporation of PAH containing fossil fuels. Due to their physico-chemical properties and ambient environmental conditions they partitioning between vapor and particle phase in the atmosphere and undergo atmospheric transport. Some PAHs, and their metabolites are carcinogenic, which makes their presence in the ambient air of concern. Humans can be exposed to substantial doses due to the vicinity of important combustion sources, such as vehicle emissions and biomass burning emissions, during daily activities. In urban areas traffic is a dominant source, while in rural area wood burning can be dominant. The composition of PAHs in these emissions depends on many factors, such as the type of fuel as well as combustion efficiencies. Moreover, once emitted into the atmosphere, the atmospheric lifetime of PAHs is influenced by many factors, such as photo-chemical oxidation and meteorological conditions. PAH concentrations are normally higher near potential emission sources and their levels can be determined using different sampling devices. The exposure to atmospheric PAHs and consequent risk assessment on human health is not trivial and many variables should be taken in account. The following chapter gives an update on the occurrence, distribution and fate of PAHs in ambient air and it gives estimates on the actual human health risks related to the exposure of PAHs in ambient air.