Acute toxicity test for terrestrial hazard assessment with exposure of Folsomia candida to pesticides in an aqueous medium

Adult Folsomia candida, soil insects, were exposed to various concentrations of carbofuran, dimethoate, oxamyl, or parathion in aqueous solutions for fourteen days. At four days, the effective concentrations at which 50% of the population was unable to coordinate movement in response to stimulation by a hair (EC super(50)) were 0.009, 0.222, 16.2, and 23.6 mg/l, for parathion, carbofuran, dimethoate, and oxamyl, respectively. Prolonged exposure to parathion did not decrease the EC super(50). The concentration of parathion in the solution gradually decreased, presumably because the insects bioaccumulated the compound, a finding that was confirmed in by exposing the insects to an aqueous solution of radiolabeled compound that almost saturated the aqueous solution. The lipophilicity of the pesticides determined their toxicity in the insects. A proposal is presented for testing toxicity in soil organisms as a method for evaluating terrestrial hazards from chemicals.