Effects of Polycyclic Aromatic Hydrocarbons contents in Soils of Selected Automobile repair Workshops in Uyo, Akwa Ibom State, Nigeria

Abstract

Background: Automobile Workshops are known for servicing, maintaining, and rectifying any issue that arises in a vehicle. Activities carried out in automobile workshops lead to the release of pollutants, including used and spent motor oils, lubricants, petrol residues, and other hazardous materials, into the environment. Aim: The aim of this study was to investigate the effect of 16 US EPA priority PAHs in soil collected from vicinity of automobile repair workshops in Uyo, Akwa Ibom State to assess and evaluate the human health risk associated with exposure. Methodology: Soil samples were collected at two (2) depths (0-15 cm and 15-30 cm) from SUS; Udi Street, SMV; Mechanic village, SMB; Mbebem Street, SOR; Old Ring road and SOS; New stadium road  automobile repair workshops and IUE; Iba Oku (control sample) using stainless steel hand-held auger. The samples were extracted with soxhlet extractor and analysed using gas chromatography–mass spectrometry (GC-MS) for Sixteen US-EPA priority Polycyclic Aromatic Hydrocarbons (PAHs). Results: The Ʃ16 EPA PAHs detected in the soil samples ranged from 0.72-4.74 mg/kg with SUS recording the highest concentration. According to the European Commission classification system of soil contamination, the soil in this study area was classified to be moderate to heavily contaminated. High molecular weight (HMW) PAHs dominated in most sites suggesting a predominantly pyrogenic origin validated by diagnostic ratios. The total benzo(a)pyrene equivalents (∑BaPeq) for the soil samples ranged from 0.1823-0.5411 mg/kg at automobile repair workshops, which significantly exceeded that at the control (0.004 mg/kg). The calculated values obtained from diagnostic ratios shows that the PAHs in this study were derived from mixed sources but predominantly pyrogenic sources. The total Incremental lifetime cancer risk (ILCR) exceeded the US EPA acceptable threshold of 1 × 10-6 at all five automobile workshop sites (3.96 × 10-6 to 1.17 × 10-5 for adults and 3.28 × 10-8 to 9.74 × 10-6 for children), while in the control site was (8.68 × 10-8 for adults and 7.19 × 10-8 for children). Conclusion: Soil around automobile repair workshop is moderately contaminated and therefore calls urgent need for environmental monitoring.