The evaluation of pesticide ingredients and formulations in vitro and correlations with in vivo data

By Clothier, R.H. - Morris, J. - Lankford, W.T.

Pesticides are often insoluble directly in aqueous solvents, but can be dissolved/suspended in surfactant-based formulations. Both surfactants and pesticides can induce irritation. Since a single in vitro assay has proved inadequate for evaluating the toxicity of a chemical and its ability to cause an irritant response, a combination of assays was employed to examine the potential toxicities of two pesticide formulations. The surfactant-based vehicles had toxicities that reflected their surfactant concentration. The formulation containing 5% permethrin required a more concentrated vehicle than was needed to dissolve 0.1% cypermethrin. In vitro, the ID50 dose (i.e. the dose which inhibited the increase in total cellular protein by 50%) was 576 microgram/ml for the permethrin formulation and 1080 microgram/ml for the cypermethrin formulation. This corresponded closely to the ID50 values for the vehicles alone (464 microgram/ml and 1230 microgram/ml, respectively). When tested at high concentrations on confluent cells over a 1-minute exposure period to mimic potential exposure of the eye, the more concentrated vehicle, Lanosol 50 ME, was 4-6 times more toxic than Siege II. Technical grade permethrin and cypermethrin had low toxicities in each of the in vitro tests employed. Taken together, these results reflected the in vivo profiles available.