Acute toxicity of chlorpyrifos, cadusafos and diazinon to three Indian major carps (Catla catla, Labeo rohita and Cirrhinus mrigala) fingerlings

Fingerlings of three Indian major carps, viz. Catla catla (Hamilton-Buchanon), Labeo rohita (Hamilton-Buchanon) and Cirrhinus mrigala (Hamilton-Buchanon), were exposed to different concentrations of chlorpyrifos (lorsban 10 G), cadusafos (rugby 10 G) and diazinon (basudin 10 G) for a period of 96h with a view to determine the median lethal concentrations (LC sub50) values for each of chemicals. Of the tested concentrations, chlorpyrifos at a dose of 6.65 ppm, cadusafos at 2.0 ppm and diazinon at a dose of 8.40 ppm or above induced 100% mortalities within 96h of exposure. The 96h LC sub50 values of chlorpyrefos, cadusafos and diazinon were 1.66, 0.72 and 2.10 ppm for C. catla, 2.35, 0.72 and 2.97 for L. rohita and 2.35, 0.72 and 2.10 ppm for C. mrigala, respectively. Pesticide induced behavioral abnormalities observed in the present study included erratic movements, rapid operculum activities, jumping of fish out of the test media, violent spasm and convulsion.

Effect of Neemta 2100 toxicity on acetylcholinesterase and serum glutamate oxaloacetate transaminase enzymes in serum of fish, Oreochromis mossambicus

Acetylcholinesterase and serum glutamate oxaloacetate transaminase enzymes have been used as marker monitoring the effect of neem seed based pesticide Neemta 2100 on the fish, Oreochromis mossambicus. Fishes exposed to sublethal concentrations of Neemta 2100 for acute periods of 24 and 48 hours were sacrificed to determine enzyme activities in serum affected due to toxicity. Laboratory studies of in vivo exposure of this pesticide showed synergistic inhibitory effect during acute period of toxicity. Acetylcholinesterase was noticed as 6.25 µm substrate hydrolyzed/mg protein/hour and serum glutamate oxaloacetate transaminase was noticed as 36.71 µm substrate hydrolyzed/mg protein/hour in control fish serum. Significant decrease in GOT level in Neemta 2100 treated fishes after short term exposure indicated its severe toxicity to fish.

Acute toxicity of metasystox to wedge clam, Donax cuneatus from west coast

96h acute toxicity tests were performed using commercial grade metasystox on the marine wedge clam, Donax cuneatus during summer 1985. The behaviour and mortality rates were recorded periodically. Most of the dams responded in opening the shell valves and extending the siphons quicker in low test concentrations (0.004-0.0052 p.p.m) but this was slow and late in high concentrations (0.0056-0.008 p.p.m). Mortality began to occur in 0.008 p.p.m. from 12 h, whereas, in 0.0052 p.p.m. from 60 h onwards. The observed LC sub(0) value was 0.004 p.p.m. and LC sub(50) 0.0064 p.p.m. The regression equation established was Y = 79.0891 + 33.4523 X. The rate of oxygen concentration increased at LC sub(0) and LC sub(50) values compared to control indicating the disturbed physiological adjustment. The results are correlated with physico-chemical parameters of seawater and discussed in the light of pesticide toxicity to the dam.

Impact of phosphamidon and its metabolites on histopathology of the liver, gill and intestine of Labeo rohita

Impact of phosphamidon, an organophosphorus pesticide and its metabolites viz. dimethyl phosphoric acid and 2-chloro 2-diethyl carbamoylmethyl vinyl acid on histopathology of a common teleost, Labeo rohita was studied by exposing the fish to sub-lethal concentrations which were taken as 1/3rd of LC50 and were equal to 0.0123 ppm for phosphamidon, 0.0160 ppm for dimethyl phosphoric acid and 0.0167 ppm for 2-chloro 2-diethyl carbamoylmethyl vinyl acid respectively. The results revealed that hepatocytes in the liver were markedly swollen and exhibited hydropic degeneration. Fusion of primary lamellae and moderate congestion of blood vessels were evident in the gill. Intestine showed degeneration of mucosa and cellular infiltration in sub-mucosa. LC50 values and histopathological photomicrographs suggest that phosphamidon is more toxic as compared to dimethyl phosphoric and 2-chloro 2-diethyl carbamoylmethyl vinyl acid.

Endosulfan: a hidden menace

A clean and healthy environment is paramount to human existence. While pesticide use has successfully sustained agricultural and food production in our lifetime as well as safeguarded human health by controlling insect pests, it has also caused many tragedies including population declines in our wildlife, fatalities in workers exposed to pesticides in its manufacture and use, and the increasing incidence of dreaded human illnesses such as cancer. A delicate balance should be achieved to mitigate the adverse impact of pesticide use to the environment and at the same time ensuring short- and long-term agricultural productivity. Endosulfan has been effectively used as a pesticide, but much evidence on its chronic and sub-lethal effects on humans and wildlife have been gathered in recent years. More research still needs to be done to determine its effects from long-term exposure at very low levels. Endosulfan is highly toxic to fish and other aquatic animals and, thus, not recommended for use in aquatic ecosystems. However, in some countries, it has been incorrectly used as a molluscicide in rice paddies, which could have an adverse impact on the rice-fish farming systems and on other surrounding aquatic ecosystems. It is clear that such practices should be stopped and users must strictly observe the recommended application methods. Agricultural productivity should be achieved with less pesticide by using integrated pest management programs which make use of biological, cultural, and physical control agents and lower doses of safer pesticide on a need only basis. The benefits of biotechnology should also be used to develop more effective and safer products and techniques. This is a valid approach and one that will require a unified and concerted effort among suppliers and users of pesticides in order to ensure that resources are used to our best advantage with minimal risk.