Toxicological Insights into Haematological and Genetic Damage in Fish Following Pesticide Exposure: A Review

Abstract

Commonly used pesticides such as organophosphates (e.g., chlorpyrifos, malathion), pyrethroids (e.g., cypermethrin, deltamethrin), carbamates (e.g., carbofuran), and organochlorines (e.g., endosulfan) have been frequently detected in freshwater bodies due to agricultural runoff and leaching. These compounds exert toxic effects on fish by inducing oxidative stress, lipid peroxidation, and the generation of reactive oxygen species (ROS), leading to DNA fragmentation, chromosomal aberrations, and micronuclei formation. Haematological disturbances include altered erythrocyte morphology, reduced hemoglobin levels, and fluctuations in leukocyte counts, indicating immune suppression and physiological stress. Ecologically, pesticide contamination disrupts aquatic food webs by reducing the abundance and diversity of zooplankton, benthic invertebrates, and insect larvae, which serve as primary food sources for many fish species. Sub-lethal pesticide effects impair fish reproduction, growth, and behavior, such as feeding efficiency and predator avoidance, leading to population decline and altered community dynamics. Persistent chemicals bioaccumulate in fish tissues and biomagnify through trophic levels, affecting piscivorous birds, mammals, and ultimately humans. The degradation of keystone and indicator species alters nutrient cycling, reduces primary productivity, and compromises essential ecosystem services such as water purification and fishery sustainability.