Assessing the distribution and human health risk of organochlorine pesticide residues in sediments from selected rivers

Sediment samples from major agricultural producing areas in Edo state Nigeria were analysed for α-HCH, γ-HCH, β-HCH and ∑DDT with the aim of elucidating contamination profiles, distribution characteristics, carcinogenic and non-carcinogenic risk of these compounds in these regions. Analysis was done using a gas chromatography (GC) equipped with electron capture detector (ECD), while health risk assessment was carried out using the Incremental Lifetime Cancer Risk (ILCR) and the chronic daily intake (CDI). Results showed varying concentrations of α-HCH, γ-HCH, β-HCH and ∑DDT pesticides in sediment samples with hexachlorocyclohexane (∑HCHs) (4.6 µg/g/dw) being the dominant contaminants as it was widely detected in all samples and stations. Source identification revealed that the current levels of HCHs and DDT in sediments were attributed to both historical use and fresh usage of these pesticides. Risk estimates using ILCR and CDI showed that the risk of cancer and non-cancer effects was highest when exposure route was through ingestion. Furthermore, model projections highlights children as high risk population groups for non-dietary exposure to OCPs. These findings suggests the need for increased monitoring programmes, with a wider scope for both currently used pesticides and legacy/banned pesticides.