Eco-toxicological and epidemiological assessment of human exposure to polycyclic aromatic hydrocarbons in the Niger Delta, Nigeria

Epidemiological examinations of polycyclic aromatic hydrocarbons (PAHs) exposure in biological bodies have shown the potential risk of cancer induction. Environmental media containing PAHs were analyzed in the Niger Delta region. Gas chromatographicmass spectrometric analyses were carried out on samples and 98% of the samples contained carcinogenic PAHs. The concentration of the 7 potential carcinogenic PAHs (Σcarcsoil 7PAHs) in the soils varied from 297–4080.6±546.3 mg/kg (min-max +/- standard deviation) with a median of 419 mg/kg, the concentrations for non-carcinogenic PAHs ranged from 315–1999±300 mg/kg with a median of 497.5 mg/kg. The total concentrations of PAHs (»total H2O17PAHs) in water samples varied from 119.8–450.0±117.9 mg/L with a median of 141.9 mg/L, while the sediment concentrations ranged from 6.0–132.0±28.7 mg/L with a median of 62.73 mg/L. Concentrations of benzo(a) pyrene (BaP), which most likely originated from crude oil spillage in the area was determined as 66.95±73.47 mg/kg in soil samples. To evaluate human exposure to carcinogenic PAHs sources, the toxic equivalence factors (TEFs), mutagenic potency equivalent factors (MEFs) and the incremental lifetime cancer risk (ILCR) methodologies were used to calculate the exposure risk. Carcinogenic equivalents (BaP-TEQ) and mutagenic equivalents (BaP-MEQ) were calculated from the potency relative to BaP (TEF) and BAP (MEF) respectively. BaP-TEQ (mg/kg) for Ωcarcsoil 7PAHs were determined as 98.80±125.81 and varied from 68.20–953.84 mg/kg, while the BaPMEQ (mg/kg) for Σcarcsoil 7PAHs were determined as 124.01±163.37 and varied from 87.24–1237.82 mg/ kg. The BaP-TEQ (mg/kg) for ΩcarcH2O7PAHs were determined as 16.79±14.44 and varied from 5.55–52.69 mg/L, similarly the BaP-MEQ (mg/kg) for ΩcarcH2O 7PAHs were determined as 9.29±8.15 and varied from 1.55–29.80 mg/kg. The cumulative ILCR from the water and soil contaminations were determined as 1.13×10−4 and 6.42×10−4 respectively for children, while values of 1.09×10−4 and 6.19×10−4 were determined respectively for adult. The ecotoxicological assessments in this study indicate contamination of environmental media in the region with high potential of acute toxicity sufficient enough to induce carcinogenic effects and chronically affect the human health of residents with prolonged exposures.