2000 Volume 44 Issue 3 Pages 155-164
Most insecticides are nerve poisons. Organochlorines and pyrethroids affect the nerve membranes and induce electrophysiological effects; organophosphates and carbamates inhibit acetylcholinesterases; nicotine, nereistoxins and chlornicotinyl insecticides affect acetylcholine receptors; avermectins affect GABA receptors; and attractants, repellents, antifeedants and pheromones affect sensory organs. Toxins of Bacillus thuringiensis affect the insect mid gut; organofluorids and arsenates affect energy production; rotenone, dinitrophenols and HCN inhibit respiratory mechanisms; and benzoylphenylureas, buprofezin and JH mimics affect insect growth. These classifications are based on the target and primary action of the compounds. A mode of action study should include definitive information of the sequential processes that lead to death of the animal. These are highly complicated processes and effects of the primary, secondary, tertiary, etc. actions on the intact animal should be considered. Few entomologists studied insect toxicology before the 2nd World War. Successful progress in insect toxicology has been stimulated by the development of insect physiology, insect biochemistry, radio tracer techniques, chromatography, electrophysiology, etc. along with the collaborated development of new synthetic insecticides. Risk assessment of insecticides has been performed not only by evaluation of acute toxicity but also chronic toxicity, carcinogenecity, mutagenecity and propagation by Good Laboratory Practices, environmental assessment, etc. Safeties of insecticides were assured by insecticide registration laws. However, the risk assessment of insecticides seems to be unsatisfactory from the view point of endocrine disruption. Mode of action of endocrine disruption compounds is so complicated that experiments on the mode of action of these compounds must cover many related organs and physiological actions through successive generations. As we cite in this review, a report was withdrawn or others have objections. These show how difficult to draw conclusions on endocrine disruption of compounds. Regarding risk assessment of insecticides, we must carefully discuss data in a realistic and science-based manner.
