Asian Journal of Environment & Ecology

Blood provides a rapid reflection of alterations occurring within the organism because it circulates throughout the body and directly interacts with xenobiotics, metabolites, and stress signals. Fish blood serves as a highly sensitive and informative medium for assessing the physiological and pathological impacts of environmental pollutants. This review aimed to synthesise available information on how fish blood responds to organophosphate (OP) exposure, highlighting haematological, biochemical, enzymatic, oxidative, and cytogenetic alterations as reliable indicators of toxicity.  Red blood cell count is one of the most sensitive haematological parameters altered under pesticide stress, and several studies have reported significant declines in fish exposed to organophosphates. Haemoglobin concentration provides direct evidence of oxygen-carrying capacity, and multiple investigations have shown its susceptibility to organophosphate stress. White blood cell count is a critical indicator of immune response and stress in fish, and its alteration under pesticide stress has been extensively studied. Platelets and thrombocytes play crucial roles in blood clotting and wound repair, and their alterations under pesticide stress have received growing attention. Blood biomarkers (AChE, SOD, CAT, GPx, GST, GSH, MDA, MN) gain diagnostic power when integrated with tissue histopathology and molecular endpoints because the trio (biochemical → cellular → molecular) maps the causal chain from exposure to adverse outcome. In conclusion, implemented with standard methods and omics-informed validation, blood biomarker panels offer a cost-effective, non-lethal, and powerful tool for routine environmental monitoring and for prioritising remediation in pesticide-impacted waters.