Assessment of Organochlorine Pesticide Residues in Soil and Their Human Health Risk

Abstract

Pesticide residues in soil pose significant environmental and public health concerns due to their persistence and potential toxicity to both crops and humans. This particularly affects vulnerable groups such as children. This study assessed the levels of pesticide residues and evaluated the associated human health risks in agricultural soils from the Ibaji area of Kogi State, Nigeria. A total of twelve composite soil samples were collected in triplicate from four different framing locations (S1-S4). The samples were extracted for residues using the QuEChERS method and further purified with Florisil and silica in a packed chromatography column. Organochlorine pesticide (OCP) residues were then analyzed using gas chromatography coupled with an electron capture detector (GC-ECD). The concentrations of OCPs varied across the sites: ND - 32.43 ± 0.54 µg/kg (S1), 0.74 ± 0.02 - 31.61±0.58 µg/kg (S2), 1.5 ± 0.04 - 48.94 ± 1.27 µg/kg (S3), and ND - 8.69 ± 0.08 µg/kg (S4). Health risk assessment showed total carcinogenic risk values ranging from 8.86 × 10-6 - 3.2 × 10-3 and 3.20 × 10-5 - 6.94 × 10-3, 8.84 × 10-6 - 4.04 × 10-4 and 3.88 × 10-5 - 8.34 × 10-4, 1.54 × 10-5 - 6.49 × 10-5 and 5.57 × 10-5 - 1.3 × 10-3, and 6.54 × 10-6 - 1.15 × 10-4 and 8.50 × 10-6 - 2.38 × 10-4 across all the study locations, exceeding the USEPA acceptable limit of 1×10-6. The values suggest a potential high cancer risk from chronic exposure, particularly for children and adults in close contact with the soil. Additionally, the observed residue concentrations exceeded USEPA-recommended safe levels for agricultural soils, indicating significant environmental contamination likely due to excessive pesticide application. These findings underscore the urgent need for regular ecological monitoring, stricter regulation of pesticide use, and public health interventions to mitigate the environmental and human health impacts of pesticide residues in the Ibaji Local Government Area of Kogi State, Nigeria.