Risk Assessment of Pesticide Residues in Water Samples From Nwaniba River, Akwa Ibom State, Nigeria

Abstract

Ecological risk assessment of pesticide residues is not only germane but critical in view of their inherent health challenges and for informed decision-making process. This study was conducted to assess the levels of contamination of organochlorine pesticide residues in water from Nwaniba River in Uruan Local Government Area of Akwa Ibom State. The analysis was carried out using Gas Chromatography with electron capture detector (GC-ECD). The obtained results revealed the predominance of Dieldrin in the different samples of water analysed from Ufak Effiong in the Southern District (station I) and Akani Obio in Uruan Central District (station II) of Uruan. Pesticide levels were found to be significantly higher than the World Health Organization /Food and Agricultural Association (WHO/FAO) Maximum Residue Limits (MRL). The concentrations of organochlorine pesticides (OCPs) ranged from Below detection limit (BDL) - 2.37 × 10-1 ng/µL for water samples. Carcinogenic risk values for γ-BHC, delta-BHC, Dieldrin, Endosulfan I and Heptachlor epoxide in the water samples were found to be less than 1.0 × 10−5, thus posing no potentially serious cancer risk to consumers. The values of cancer risk obtained were lower (6.448 × 10- 11 and 7.208 × 10-11) than the established maximum limit. Hazard index (HI) values calculated for pesticide consumption through water by children and adults are all above unity, indicating that high toxic risks are associated with them. The HI values for children exposure are significantly lower compared to those of adults of Ufak Effiong and Akani Obio. This study reveals that the physicochemical parameters of water obtained from both stations were below the maximum permitted levels set by World Health Organization (WHO) and Nigerian Standard for Drinking Water Quality (NSDWQ). It also provides a baseline data and critical information to encourage effective monitory and management of the ecosystem.