Risk assessment of organochlorine pesticide residues in water and fish from two Ethiopian highland lakes

Abstract

The widespread use of organochlorine pesticides (OCPs) poses significant ecological and human health concerns, particularly in developing countries. This study evaluated OCP contamination and associated risks in water and fish from two Ethiopian highland lakes. Ecological risk was assessed using the risk quotient (RQ), calculated as measured concentrations divided by predicted no-effect concentrations (PNECs). Health risks were assessed using hazard quotient (HQ), derived from estimated daily intake and reference doses (RfDs), and cancer risk (CR) based on U.S.EPA models. Of the 18 target OCPs, eight were detected in both water and fish. In water, mean concentrations ranged from 1.11 µg/L (lindane) to 15.0 µg/L (Σendosulfan), exceeding WHO guideline limits, except for lindane and endosulfan. Fish from Lake Tana contained 12.6–68.8 µg/kg, and those from Lake Hayqe 10.7–61.2 µg/kg, with Σendosulfan and ΣDDTs dominating. Elevated RQs, particularly for β-endosulfan, 4,4′-DDT, and endrin, indicated potential ecological risks. HQs for adult fish consumers were below the safety threshold (HQ < 1), suggesting low non-carcinogenic risk. However, CR values indicating potential carcinogenic risk (10⁻⁶ –10⁻⁴), with dieldrin posing the greatest concern. These findings highlight the need for integrated pest management (IPM) strategies to reduce pesticide inputs and mitigate OCP contamination in the region. • Eight of 18 OCPs were detected; most water concentrations exceeded WHO limits • Min–max concentrations of total Endosulfan and DDTs in water: 11.3-19.3 µg/L and 3.42-5.01 µg/L • Min–max concentrations of total Endosulfan and DDTs in fish: 25.4-80.1 µg/kg and 51.9-61.2 µg/kg • Elevated RQ indicates ecological risk from β-endosulfan, DDT, and endrin • Most OCPs show low non-cancer risk (HQ<1); dieldrin poses the highest cancer risk • Findings highlight the urgent need for IPM and stricter pesticide regulation in the region