Ecological and Health Impacts of Organophosphorus Pesticides: A Focus on Ethion in Aquatic Ecosystems

Pesticides play a crucial role in modern agriculture by protecting crops and enhancing yields, yet their indiscriminate use poses significant threats to non-target organisms and ecosystems. In India, annual pesticide consumption ranges from 52,000 to 62,000 tonnes, driven by yield pressures, pest resistance, and limited awareness of sustainable alternatives. Organophosphate pesticides are widely accepted for their rapid biodegradability and reduced environmental persistence. Aquatic ecosystems are particularly vulnerable, as pesticides enter water bodies through runoff, spray drift, and leaching, directly harming fish and invertebrates and disrupting food webs. Human health impacts include cancers, blood disorders, pulmonary dysfunction, and immune deficiencies linked to contaminated water and food sources. Ethion, a thiophosphate-class organophosphorus compound used on crops like tea, cotton, and maize, becomes toxic by converting to ethion monoxon, which inhibits acetylcholinesterase at nerve synapses. This results in uncontrolled nerve stimulation, muscular dysfunction, oxidative stress, and death in susceptible organisms. The toxic effects of Ethion 50EC pesticide on the freshwater fish Labeo rohita by measuring changes in aspartate aminotransferase (AAT) and alanine aminotransferase (ALAT) enzyme activities across gill, liver, kidney, brain, and muscle tissues.Which indicate Ethion-induced hepatotoxicity, mitochondrial disruption, and metabolic shifts toward gluconeogenesis for energy production amid oxidative stress, positioning AAT and ALAT as sensitive biomarkers for pesticide pollution in aquatic ecosystems. These findings highlight the urgent need for responsible pesticide management through integrated pest management (IPM), precise dosing, farmer education, and environmental monitoring to protect aquatic biodiversity while ensuring food security.