Comparative study on the acute toxicities of alpha, beta, gamma, and delta isomers of hexachlorocyclohexane to freshwater fishes

When the insecticide hexachlorocyclohexane (HCH) is manufactured, five isomers are present, of which the gamma isomer, lindane, is the insecticidal product. That isomer, as well as the alpha , beta , and delta isomers biodegrade slowly and have been found in water, soil and vegetables. The acute toxicity of the isomers to three species of freshwater fish was determined. For all species, lindane was the most toxic isomer. There was no change in the LC super(50) with time. The delta isomer was the least toxic. The toxicity of the alpha and beta isomers was similar. For these three isomers, the LC super(50) decreased with time. Guppies were more resistant to the toxic effects of the isomers than neon fish and zebra fish, which demonstrated similar sensitivity to the isomers.