Concentrations, profiles and exposure risks of polycyclic aromatic hydrocarbons (PAHs) in passive air samples from Lagos, Nigeria

Polycyclic Aromatic Hydrocarbons (PAHs) are potential carcinogenic air components with sources associated with incomplete combustion and related activities. Although such activities are dominant in Nigeria urban space; hitherto, there are limited atmospheric studies on PAHs. The present study investigated air PAHs in Nigeria mega city. Sigma(15)PAHs concentrations generally range from 24 ng/m(3) (in residential area of Ketu) to 110 ng/m(3) (in industrial centre of OSH). The concentration ratio of industrial (Oshodi) location to residential (KTU) location was observed to be similar to 4. General seasonal trend was not observed as seasonal variation was location specific, however OSH highest concentrations were observed in the dry season (October-December) with 3-5 membered ring having a potential influence on three other locations (Agege, Ikeja and Apapa) in the dry period. Impact of a dumpsite explosion on the atmosphere was observed in a proximate location. Relatively high exposure risk was observed at Yaba and Oshodi though still within the low risk boundary. In general, Lagos air PAHs cancer risks evaluated with two risk models indicated: (1.8-9.7) x 10(-5) and (0.23-1.2) x 10(-6) respectively. To the best of our knowledge, this report provides the first full data on air PAHs concentrations in Nigeria and highlights the influence of industrial cores on residential locations.