Assessment of occupational exposure to polycyclic aromatic hydrocarbons via involuntary ingestion of soil from contaminated soils in Lagos, Nigeria

Soils from 12 sites in Lagos area, Nigeria impacted by anthropogenic activities were extracted by ultrasonication and analysed for the concentration of 16 priority polycyclic aromatic hydrocarbons (PAHs) by gas chromatograph-mass spectrometer (GC-MS). The concentration of the sum of PAHs ranged from 0.2 to 254 mu g/g at these sites. The sum benzo[a]pyrene-equivalent dose (BaPeq) at the sites ranged from 0.0 (K, forest soil) to 16.7 mu g/g (C, the lubricating oil depot soil). Mean daily intake (MDI) for the composite soils samples when compared that of food revealed that some of the individual PAH in samples from sites A (Dump site), C (Depot and loading point for used for black oil), F (Dump site), G(petroleum depot), H (Roadside) and L (Car park) exceeded the recommended the recommended MDI threshold for food, indicating some risk associated with activities on these sites based on this ingestion estimate exceeded value. 8.2 x 10(-6), 7.1 x 10(-7), 1.2 x 10(-4), 4.9 x 10(-7), 7.3 x 10(-7), 1.4 x 10(-5), 7.9 x 10(-5), 4.6 x 10(-6), 3.4 x 10(-7), 2.4 x 10(-7), 2.2 x 10(-7) and 1.1 x 10(-4) estimated theoretical cancer risk (ER) for an adult with a body weight of 70kg working on sites were composite soil samples A, B, C, D, E, F, G, H, I, J, K and L respectively were sampled. The ER from occupational exposure to surface soil based on oral ingestion were all higher than the target risk of 1 x 10(-6) for normal exposure but were all within the 1 x 10(-4) for extreme exposure for most of the sites except for site C and L. The differences in concentration and risk were related to the different activities (e.g., handling of petroleum products, open burning, bush burning) undertaken at these locations. However, it should be noted here that the resultant risk could be overestimated, since these calculations were based on an exhaustive extraction technique which may be different from uptake by the human guts (bioavailability study).