Occupational and human health risks of exposure to potentially toxic elements (PTEs) in top soils from steel fabrication workshops

Introduction

Environmental pollution caused by potentially toxic elements (PTEs) from anthropogenic sources has become a global concern due to its deleterious effect on humans and ecosystem health. Therefore, this study evaluated the concentrations of PTEs, pollution level and human health risk in topsoil from ten (10) steel fabrication workshops in Abeokuta, Ogun State, Nigeria.

Materials and methods

Ten (10) composite soil samples were collected in November 2023, from 10 different steel fabrication workshops in proximity to residence in Abeokuta, Ogun State, Nigeria. One (1) gram of processed sample was digested using aqua regia and PTE concentration estimated using atomic absorption spectrophotometer (AAS). Pollution index assessment was determined using enrichment factor (EF) and geo-accumulation index (I-geo) while descriptive statistics and correlation were subjected to statistical package for social sciences (SPSS).

Results

The result showed that Iron (Fe) (11,500 – 42,100 mg kg⁻¹), Lead (Pb) (10.7 – 583 mg kg⁻¹), Chromium (Cr) (16.3 - 49.7 mg kg⁻¹), Zinc (Zn) (34.6 – 343 mg kg⁻¹), Manganese (Mn) (109 – 840 mg kg⁻¹), Nickel (Ni) (2.23 - 25.3 mg kg⁻¹), Copper (Cu) (16.6 -107 mg kg⁻¹) and Cadmium (Cd) (2.23 - 25.3 mg kg⁻¹) were present. Mean concentration for Pb (179±202 mg kg⁻¹) is higher than the Canada soil guideline value (CSGV) (140 mg kg⁻¹) while other PTEs are within the recommended limit. Pollution indices revealed EF (Cd and Pb) and I-geo (Cd) as the primary pollutants in the soil while the strong significant correlation between Cr, Cu and Mn p < 0.05. Cr, Ni, Pb and that of Cu, Mn, Ni, Pb, Zn p < 0.01 suggest an emanation from both geogenic and anthropogenic sources. Human health risk assessment revealed Fe as the most dosed PTE and ingestion as the major pathways of exposure especially to children being the most susceptible. Hazard index (HI) and total cancer risk (TCR) values for PTEs were <1 and within the acceptable threshold (1 × 10⁻⁶ – 1 × 10⁻⁴) except for Pb (3.93E+01; 1.16E-03) in adults respectively.

Conclusion

The study showed that the topsoil from the steel fabrication workshop is polluted with Pb and Cu toxicity and the adult (residents and workers) population exposed to the soil is potentially at a non-cancer and cancer risk.