Environmentally Relevant Mixtures in Cumulative Assessments: An Acute Study of Toxicokinetics and Effects on Motor Activity in Rats Exposed to a Mixture of Pyrethroids

Due to extensive use, human exposure to multiple pyrethroid insecticides occurs frequently. Studies of pyrethroid neurotoxicity suggest a common mode of toxicity and that pyrethroids should be considered cumulatively to model risk. The objective of this work was to use a pyrethroid mixture that reflects human expo-sure to common pyrethroids to develop comparative toxicokinetic profiles in rats, and then model the relationship between brain concentration and motor activity. Data from a national survey of child care centers were used to make a mixture reflecting propor-tions of the most prevalent pyrethroids: permethrin, cyperme-thrin, β-cyfluthrin, deltamethrin, and esfenvalerate. The mixture was administered orally at one of two concentrations (11.2 and 27.4 mg/kg) to adult male rats. At intervals from 1 to 24 h, motor activity was assessed and the animals were sacrificed. Pyrethroi