Bioaccumulation and risk assessment of organochlorine pesticides in fish from a global biodiversity hotspot: iSimangaliso Wetland Park, South Africa

Highlights: • Bioaccumulation of OCPs in fish from a key estuarine region was investigated. • Elevated residue concentrations were detected in all tissue samples analysed. • The study highlights ecotoxicological risks to higher trophic level organisms. • Potential health risks associated with the consumption of fish from this region. Organochlorine pesticides (OCPs) have been used extensively in the eastern regions of South Africa for agricultural and malaria control purposes, yet few data exist on the local environmental and social impacts of these compounds. Such issues have become of increasing concern in the iSimangaliso World Heritage Site, where the continued use of OCPs may pose risks to several sensitive and protected species. This study was designed to examine the bioaccumulation of OCPs in two common fish species, Oreochromis mossambicus (Mozambique tilapia) and Clarias gariepinus (African sharptooth catfish) from iSimangaliso Wetland Park. These species are targeted by local subsistence fishermen and sustain substantial bird and crocodile populations. Our findings indicate widespread contamination of the aquatic environment, with ΣOCP fish tissue concentrations in the range of 6907–8740 ng g⁻¹ lw and 2953–5874 ng g⁻¹ lw for C. gariepinus and O. mossambicus, respectively. HCHs (471–1570 ng g⁻¹ lw), DDTs (645–2399 ng g⁻¹ lw), drin-related residues (589–1960 ng g⁻¹ lw), chlor-related residues (455–2162 ng g⁻¹ lw) and endosulfans (457–1495 ng g⁻¹ lw) were detected in all tissue samples. Concentrations detected in the majority of samples exceeded European Commission maximum residue limits and a health risk assessment indicated potential dietary risk associated with exposure to heptachlor, heptachlor epoxide and dieldrin. This study represents the first investigation into OCP bioaccumulation in fish species from iSimangaliso Wetland Park. Our findings highlight the need for more detailed investigations into the bioaccumulation and ecotoxicological effects of these contaminants in the food web and the associated risks to local ecosystems and human health.