An insight into endocrine disruption by pyrethroid insecticides in fishes

Abstract

Pyrethroids are a group of widely used insecticides for agricultural and residential purposes. They have selective toxicity that is relatively harmless to mammals and birds. But they are extremely toxic to fish. They are insoluble in water and accumulate in sediments and bioaccumulate in fishes. Being lipophilic in nature they can easily enter through fish gills. Fishes are unable to metabolize pyrethroids. Both the parent compound and its metabolites are harmful to the fish. They adversely affect various physiological pathways in fish. It has now been established that pyrethroids can act as endocrine disruptors. Their chirality plays an important role in this aspect. The different enantiomers of the pyrethroids have diverse roles as endocrine disruptors in fishes. The effect of endocrine disruption by pyrethroids in fishes grossly affects their survival, behavior, growth, and reproduction. Because of this endocrine disruption, many marker genes of hormone expression are either upregulated or downregulated in fishes. Research has been carried out to understand the exact mechanism of these endocrine disruption pathways. Techniques have been developed to ameliorate the effect of pyrethroids in fishes. This review tries to summarize the endocrine disruptive effects of some of the commonly used pyrethroids in fish and indicates the recently developed ways to mitigate the toxic effects of these insecticides.