Occupational Health and Toxicological Risk of Exposure to Toxic Elements (TEs) in Top Soil from Residentially Situated Automobile Workshops (AWs)

Abstract

Background: Undoubtedly the biggest single cause of pollution, automobile emissions have a variety of negative occupational and human health impacts. Chemicals, paints, primers, and other hazardous products are frequently used in auto workshops' operational procedures. Substances like petrol, diesel, solvents, lubricants, and grease can be unintentionally or purposely release/exposed to the terrestrial environment. Numerous rock oil products consist of organic compounds that are capable of causing significant risk to soil, organisms, and humans due to their high toxicity. Objectives: The study aims to assess the occupational and toxicological risk of exposure to toxic elements (TEs) in topsoil from residentially situated automobile workshops (AWs) in Abeokuta, Ogun State, Nigeria. Methods: 12 composite soil samples were strategically collected and transported to the laboratory. 1 g of the processed sample was digested using aqua regia, namely a mixture of nitric acid and hydrochloric acid, optimally in a molar ratio of 1:3, while toxic elements analyses were done using an atomic absorption spectrometer (AAS). Results: The result showed the presence of arsenic (As = 0.67 – 5.63 mg/kg), cadmium (Cd = 8.92 – 134 mg/kg), cobalt (Co = 6.21 – 71.22 mg/kg), nickel (Ni = 1.89 – 9.18 mg/kg), and lead (Pb = 32.6 – 211 mg/kg) in the soil. The concentrations of Cd and Pb in 66.7% and 58.3% of the sample are higher than the Canada soil guideline value (CSGV) (for Cd 22 and for Pb 140 mg/kg) respectively. Contamination factors (CF) indicate very high soil contamination from Cd and Pb, and the significant association between the TEs (Pb, Cd, Co, Ni and As) p < 0.01, suggests an emergence from an anthropogenic origin. Hazard index (HI) values for the TEs were < 1, except for Pb (27.8) in the children, indicating a significant non-cancer-related effect on exposure, while the total cancer risk (TCR) value was within the threshold limit. Conclusions: The investigated topsoil is polluted with Cd and Pb, and there is a non-cancer-related effect on children with prolonged exposure to Pb. Therefore, AWs should be cited away from residential homes, while remediation of the polluted soil should be considered.

Keywords

• automobile workshops
• health risk
• topsoil
• toxic elements
• environmental hazard