Polyethylene glycol used as a dispersant potentiates the toxicity of insecticides in mammalian cells rather than insects.

Insecticides are used in household products with various dispersants such as polyethylene glycol (PEG) and polyoxyethylene lauryl ether (PLE) to improve solubility. Although certain effects are expected, the combination effects of insecticides and dispersants remain elusive. Here, five different classes of insecticides (i.e., dinotefuran, fipronil, hydramethylnon, indoxacarb, and etofenprox) were dispersed in water, PEG, and PLE, and their lung inflammation potential was evaluated by bronchoalveolar lavage fluid analysis 24 h after intratracheal instillation into the lungs of rats. All chemicals dispersed in water caused no inflammation. However, among the five chemicals dispersed in PEG and PLE, only hydramethylnon showed significant neutrophilic inflammation and hydramethylnon in PEG showed 4-fold higher inflammogenic potential than that in PLE. The in vitro cytotoxic potential of hydramethylnon in PEG was 10-17 fold (in A549) or 12-14 fold (in dTHP-1) higher than that of hydramethylnon in PLE, and greater than 370 fold (in A549) or 65-169 fold (in dTHP-1) higher than that in water. PEG toxicity increased due to the micellar formulation of hydramethylnon in PEG, increasing cellular uptake by simple diffusion. Therefore, the observed potentiation effect highlights that the combination effect of formulation of hydrophobic compounds with dispersants should be carefully evaluated.