T9 PM Pyrethroid Insecticides in Urban and Agricultural Environments
Tuesday, 15 November 2005: 1:50 PM - 5:30 PM in 339-340

(COA-1117-844827) Toxicology of synthetic pyrethroids to fish.

Coats, J¹, ¹ Iowa State Univ, Pesticide Toxioclogy Lab, Dept Entomology, Ames, Iowa, USA

ABSTRACT- Natural pyrethrins have considerable toxicity to fish, as well as aquatic arthropods. However their highly labile character results in very rapid dissipation in most natural waters. Modern synthetic, so-called photostable pyrethroids are also much more stable in aquatic or marine systems than the original natural pyrethrins; they are also more toxic to fish (and aquatic arthropods) than the natural pyrethrins. The synthetic pyrethroids, however, exhibit low levels of acute toxicity to birds and mammals. Our research focused on explaining the high toxicity to fish, compared to the low toxicity to birds and mammals, and it resulted in determining several contributing factors. Toxicokinetic factors were examined: uptake efficiency, distribution in the body, biotransformation, and elimination. Potential secondary mechanisms of action were investigated, especially the possible impact of hardness and salinity on osmoregulation. Uptake rate for a highly lipophilic halogenated synthetic pyrethroid was actually lower than for most other pesticides. Biotransformation deficiencies in several species of fish, especially in ester hydrolysis, accounted for some of the discrepancy between fish and higher vertebrates. Elimination also seemed to progress more slowly in fish. Stresses on osmoregulation are able to contribute as a secondary mechanism of action. Selective toxicity of diastereomers and determination of concentrations in brains at time of death (and exposure concentrations or doses causing death) revealed that other toxicodynamic differences also exist between fish and the higher vertebrates. Concentrations in bird and rat brains at death were significantly higher than concentrations in fish brains at death. In summary, multiple toxicokinetic and toxicodynamic factors contribute to the acute susceptibility of fish to synthetic pyrethroid insecticides.

Key words: synthetic pyrethroid, insecticide, fish, toxicology