Commentary on Use of Commercial Pyrethroids

What is it about?

The major problem with this article is the inability to determine the chemical agent, or agents, responsible for the teratological and/or behavioural effects in the offspring. In this study, the pregnant and lactating rats were exposed to a commercial formulation of cyfluthrin that contains 95% unknown ‘inert’ ingredients. According to a manufacturer’s label for this product, it may contain as much as 9% (%w/w) aromatic hydrocarbons and 9% ‘stabilizers’. Aromatic hydrocarbons such as toluene and xylene are well-known neurotoxicants, and there is evidence for developmental neurotoxicity associated with exposure to these solvents. The authors conclude in the article that ‘ . . . the tested doses of cyfluthrin are not embryotoxic but elicit significant toxicity on the behaviour of neonates.’ The problem with this conclusion is that the exposure was not solely to cyfluthrin, and the vehicle control (tap water only) was insufficient because it did not contain the inert ingredients. Therefore, it is impossible to determine whether any effects are due to the cyfluthrin, the other inert ingredients or their combination. Because of this serious confound the authors’ conclusions that the effects can be attributed solely to cyfluthrin exposure cannot be supported.

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