LAUSR

Abstract Pesticides constitute one of the major sources of environmental hazards to human and animals as they concentrate in the food chain. Organochlorine, organophosphorus, and carbamate pesticides were investigated using water, sediment, and fish (Clarias gariepinus, Oreochromis niloticus, and Tilapia zillii) muscle samples of the Nile River in Cairo region (Egypt). Pesticide residues were analyzed seasonally using gas chromatography. The results showed that the average total pesticide residue in sediment was higher (63.5 ± 36.2 ppb) than that in water samples (45.1 ± 35.0 ppb). High levels of total pesticide residues in water and sediment samples were detected in autumn (73.57 ± 62.97 and 103.03 ± 16.05 ppb, respectively), which may be attributed to the increase in suspended matter (low flood) and high application of pesticides during that season. Pesticide residue in tissue samples of C. gariepinus amounted to 49.1 ± 17.8 ppb followed by T. zillii (48.3 ± 18.9 ppb) and O. niloticus (45.6 ± 28.7 ppb). The relatively high levels of total pesticide residue on C. gariepinus tissue may be explained by the nature of catfish habits and feeding. The estimated pesticide residual concentrations in fish samples did not exceed the maximum residue limits. Health risk estimation revealed that all tested pesticides in the studied fish species had no potential for systemic toxicity to consumers, but regular monitoring is recommended to control the levels of pesticide residues in the Nile River ecosystem.