Page 825 - The Toxicology of Fishes

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Toxicology of Synthetic Pyrethroid

Insecticides in Fish: A Case Study

Joel R. Coats

CONTENTS
Introduction............................................................................................................................................805
Toxicity...................................................................................................................................................807
Toxic Mode of Action..................................................................................................................807
Factors Influencing Toxicity.........................................................................................................808
Formulation.........................................................................................................................809
Water Parameters ................................................................................................................809
Temperature ........................................................................................................................809
Suspended Solids and Sediment ..................................................................................................810
Toxicokinetics ........................................................................................................................................810
Uptake...........................................................................................................................................810
Distribution...................................................................................................................................810
Detoxification ...............................................................................................................................810
Elimination ...................................................................................................................................812
Toxicodynamics .....................................................................................................................................812
Stereoselective Toxicity................................................................................................................812
Secondary Mechanisms of Action ...............................................................................................813
Fish Nervous System Sensitivity .................................................................................................814
Conclusions............................................................................................................................................814
Acknowledgments..................................................................................................................................815
References..............................................................................................................................................815

Introduction

The development of photostable synthetic pyrethroids as broad-spectrum commercial insecticides around
1980 represented a new threat to fishes. Naturally occurring pyrethrins, from a Eurasian species of
chrysanthemum, had been used for decades for control of insects in homes, restaurants, barns, and
gardens and on pets, livestock, and stored grain. They were selective, safe, and nonpersistent (their half-
lives in sunlight are measured in minutes or hours). They posed very few nontarget effects or residue
problems. Although they are acutely toxic to fish, very few accidental poisonings occurred because they
are not registered for aquatic uses, and they seldom have enough persistence to reach water from a
normal application.
After decades of developmental efforts, several chemical companies were successful in synthesizing,
patenting, and formulating several important photostable pyrethroid insecticides for commercialization.
Through stepwise chemical substitution of three or four labile groups in the basic pyrethrin molecule,
the agrichemical company chemists invented numerous more stable and more potent synthetic analogs

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