Human health effects of polycyclic aromatic hydrocarbons as ambient air pollutants - Report of the Working Group on Polycyclic Aromatic Hydrocarbons of the Joint Task Force on the Health Aspects of Air Pollution

Overview

Polycyclic aromatic hydrocarbons (‎PAHs)‎ are a large group of organic compounds containing two or more fused aromatic (‎benzene)‎ rings. The main anthropogenic sources of emission are the incomplete combustion or pyrolysis of organic material (‎i.e. emissions from vehicles, domestic heating or cooking)‎ and the burning of agricultural waste. Human exposure to PAHs may occur from inhalation, dermal exposure or the ingestion of food contaminated with PAHs. PAHs in air pollution are primarily found bound to particulate matter; when PAHs are present in the gas phase, they have a duration of less than a day. Overall, the present scientific evidence suggests that the PAHs in ambient air are associated with increased cancer incidence in exposed populations. Positive associations have been reported between ambient PAHs and breast cancer, childhood cancers and lung cancer. Epidemiological studies have shown that PAHs are associated with reduced lung function, exacerbation of asthma, and increased rates of obstructive lung diseases and cardiovascular diseases. Limited epidemiological evidence also suggests adverse effects on cognitive or behavioural function in children. For several PAHs that are carcinogenic air pollutants, a lowest possible exposure should be aimed at to minimize the risk of cancer development in view of a no-effect threshold. It was not possible to establish whether current WHO guidelines for benzo[‎a]‎pyrene provide sufficient protection against diseases other than cancer. Therefore, the relevance of non-cancer health end-points of PAH exposure should be further explored.