Toxicity-metabolism relationship of the photoisomers of cyclodiene insecticides in freshwater animals.

The residual cyclodiene insecticides aldrin (A), dieldrin (D), heptachlor (H) and isodrin (I) can be converted by sunlight and ultraviolet light to their corresponding respective photoisomers photoaldrin (PA), photodieldrin (PD), photoheptachlor (PH) and photoisodrin (PI) (1,2,3,4). PA, PD and PH appear to be more toxic than their parent compounds to adults of the housefly, Musca domestica L. and larvae of the mosquito, Aedes aegypti L. (3,5,6). The increased toxicity of PA, PD and PH observed with faster speed of their toxic action is related with their metabolism to more toxic lipophilic ketones (5,7). On the other hand, the toxicity of PI is greatly reduced due to its rapid detoxification by these insects (3,5).