Endocrine Disruption and Reproductive Dysfunction in Freshwater Fishes Exposed to Agricultural Runoff and Synthetic Estrogens in Rural India: A Mechanistic Critical Review

Abstract

Background: Agricultural pesticides, steroid hormones and other endocrine-active contaminants can enter freshwater networks through different and overlapping pathways. Experimental evidence establishes that estrogens and several pesticide classes can disturb fish endocrine signalling, gametogenesis and reproduction; however, chemically measured exposure and directly attributed reproductive impairment remain unevenly documented in rural Indian river systems. Objective: To synthesize evidence linking contaminant identity and route, hypothalamic–pituitary–gonadal signalling, histological outcomes, fertility, and population-level effects, while evaluating the transferability of international experimental studies to Indian freshwater fishes. Approach: A structured, source-traceable critical synthesis of Indian pesticide monitoring and fish experiments, whole-ecosystem estrogen studies, mechanistic toxicology, and standard testing methods. Results: Indian Yamuna surveys confirm historical organochlorine pesticide residues and an Indian catfish experiment provides endocrine evidence following gamma-HCH exposure; Ganga monitoring documents fish tissue injury but not estrogen-specific reproductive causation. International EE2 studies demonstrate disruption at low ng/L exposures, intersex phenotypes, lowered fertilization and even population collapse during long-term whole-lake exposure. Atrazine evidence is mixed across tests, species and conditions. Interpretation: Induced vitellogenin or gonadal lesions are valuable but non-exclusive signals; attribution requires measured mixtures, life-stage context and organism-level outcomes. Conclusion: Coordinated LC-MS/MS surveillance, validated estrogenicity assays, gonadal histopathology, controlled breeding endpoints and longitudinal ecological monitoring are needed to establish risk in rural Indian waters. Review designation: This article presents a structured mechanistic critical synthesis, not a completed systematic review; its evidence matrix organizes claims by directly measured outcomes rather than by an exhaustive PRISMA search.