Eco Toxicological Assessment of Pesticides on Marine Fish.

Abstract

The Pakistan marine ecosystem is constantly threatened by variety of anthropogenic substances, such as, heavy metals, pesticides, oil, radioactive substances, petroleum hydrocarbons, etc., from industries, agricultural sources, and sewage disposal. Indiscriminate use of agrochemicals to control pests in agriculture to increase the yield of crop causes chemical pollution. In the present study, organophosphate pesticides (chlorpyrifos and malathion), synthetic pyrethroid pesticides (cypermethrin, lambdacyhalothrin) and herbicide (buctril) are used to assess the toxic effect on fish. In the present study the fish Oreochromis mossambicus is used as it is highly resistant, easy to handle, have a broad salinity and temperature tolerance. First chapter is the general introduction deals with the pesticides and the effects of pesticides on living organisms. The Second chapter demonstrates the genotoxic effect of pesticides on fish erythrocytes. The aim of this study is to verify the efficiency of the micronucleus assay in laboratory, using erythrocytes of the tilapia specie (Oreochromis mossambicus) as genotoxicity biomarker. Different doses of organophosphate pesticides (chlorpyrifos and malathion), synthetic pyrethroid pesticide (cypermethrin, lambda-cyhalothrin) and herbicide were injected intraperetonially and specimen were sacrificed after 24 and 48 hours. Peripheral blood samples smears were stained with Giemsa, MN frequencies were counted and statistically analyzed. Our results revealed significant dose dependent increase in the frequencies of micronuclei in pesticide treated fish as compare to control. The highest MN frequencies were recorded after 48 hour cypermethrin exposure and the lowest MN frequencies were recorded after 48 hour buctril exposure. The genotoxicity of pesticides vi on fish at 48 hour exposure in the present study is found to be in the order of cypermethrin, chlorpyrifos, malathion, lambda-cyhalothrin and buctril, in peripheral blood erythrocytes. Result of the present study suggests use of the micronucleus test in fish erythrocyte as a sensitive indicator for evaluation and assessment of the carcinogenic and mutagenic compounds in marine environment. The Third chapter deals with the effect of organophosphate pesticides (chlorpyrifos and malathion), synthetic pyrethroid pesticides (cypermethrin, lambda-cyhalothrin) and herbicide (buctril) on total protein content of the fish (Oreochromis mossambicus). For this regard fish is treated for 24 and 48 hours with different concentrations of pesticides. Total protein content in fish tissues were determined by Biuret method. The present study shows that total protein content was inhibited in Oreochromis mossambicus after exposure to organophosphate pesticides (chlorpyrifos, malathion), synthetic pyrethroids (lambda-cyhalothrin, malathion) and herbicide (buctril). The levels of total protein content showed decrease for pesticide treated fish in the order of cypermethrin, malathion, chlorpyrifos, lambda-cyhalothrin and buctril respectively at 48 hrs. The present study reports metabolic dysfunction in response to pesticide toxicity in the fish. Pesticide acts as stress inducing agents which affect the functional state of tissues of the exposed organisms. The fourth chapter describes the effect of pesticides on the histology of fish Oreochromis mossambicus. The fish is treated with the different concentration of organophosphate and synthetic pyrethroid pesticides such as 0.01 ppm and 0.08 ppm for 48 hours. The gills and liver tissue of fish were examined to observe the histopathology. The treated tissues were compared with the tissue of control group. In the present study, vii exposure of the organophosphate and pyrethroid pesticide to fish resulted in structural alterations of the gill lamellae including complete architectural loss, necrosis, shortening of secondary lamellae, fusion of secondary lamellae, thickening of primary lamellae, epithelial desquamation, hyperplasia and lamellar telangiectesis. Many histopathlogical changes have been observed in the liver of fish such as necrosis, pyknotic nuclei, cloudy swelling of hepatocytes and vacuolated fat cells. Histological comparison of gill and liver tissues after exposure to pesticides indicated that most damage occurred in the gill as compare to the liver. The severity of these damages to gill and liver of the fish is proportional to the concentration of the pesticides. In the fifth chapter the acute toxicity of organophosphates (malathion, chlorpyrifos) and synthetic pyrethroid (cypermethrin, lambda-cyhalothrin) pesticides on the marine fish (Oreochromis mossambicus) was investigated. Acute toxicity of the pesticides on marine organism was estimated by determination of the 24 hour LC50. The toxicity tests were performed separately for each pesticide. Data generated from the acute toxicity tests were evaluated using the probit analysis statistical method. The LC50 values obtained at 24 hour show that the fish were sensitive to all the four pesticides tested. The rate of mortality (%) was directly proportional to the concentration of pesticides. In the present study we noted that lambda-cyhalothrin is the most toxic pesticide having LC50 0.014 ppm followed by malathion 0.028 ppm, cypermethrin 0.031ppm and chlorpyrifos 0.063 ppm. The result of the foregoing study suggests that organophosphates and synthetic pyrethroids pesticides are highly toxic to fish juveniles, may attribute to decline of fisheries and marine resources which are valuable natural assets of the country. viii The sixth chapter deals with the effect of pesticides on the fish tissue enzymes for e.g., cholinesterase (AChE), alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), acid phosphatase (ACP) and alkaline phosphatase (ALP). The enzymes are important for the metabolic functions of living organisms. They act as a biological catalyst, any disturbance in the enzymes activity can cause harm to the body which may produce many severe diseases or any other disorders. The outcome of this study is to notice the effects of organophosphate and synthetic pyrethroid pesticide on the AChE (Acetyl cholinesterase), ALT (Alanine Aminotransferase), AST (Aspartate Aminotransferase), LDH (Lactate Dehydrogenase), ACP (Acid Phosphatase), ALP (Alkaline Phosphatase). Fish (Oreochromis mossambicus) exposed to a concentration equal to LC50 values of all pesticides over a period of 24hrs and were kept in ice during the preparation until analyses. Known weight of fish (test and control) was homogenized. Content was centrifuged and supernatant was immediately analyzed for enzymes using analysis kits. AChE activity levels decreased in cypermethrin, chlorpyrifos, and malathion treated fish tissues. Significant (p< 0.05) decrease was observed in chlorpyrifos, and malathion treated fish tissues but in cypermethrin decrease was not significant. In lambdacyhalothrin significant (p< 0.05) increase activity was observed in pesticide treated fish tissues. AST activity was decreased (p< 0.05) significantly by organophosphate pesticides and synthetic pyrethroids pesticides treated groups. The ALT activity level increased significantly (p< 0.05) in chlorpyrifos pesticides treated fish tissues however the ALT activity level was significantly (p< 0.05) decreased in tissues exposed to the malathion, cypermethrin and lambda-cyhalothrin. Malathion, ix chlorpyrifos, cypermethrin and lambda-cyhalothrin significantly (p< 0.05) decreased the LDH activity levels in fish tissues. Significant (p< 0.05) decrease levels of ACP activity in fish tissue were noticed in all pesticides treated fish. ALP activity was reduced in tissues of both organophosphate pesticides and synthetic pyrethroids treated fish. In lambda cyhalothrin pronounced decrease was observed but it was not significant. In malathion treated fish tissue significant (p< 0.05) decrease was noticed. Environment is considered as the one of the essential values of the world wide community since its protection and preservation is necessary for survival of humanity. The results of the biochemical profile in fish tissues indicate a marked neurotoxic effect of pesticides and shows that this change could be used as biomarkers for marine pollution. Pesticide pollution is a potential danger for fisheries and a threat to public health caused by consumption of contaminated fish. Therefore there is an urgent need to protect the environment through the management of pollution.