Ecotoxicological effect of fipronil and its metabolites on Folsomia candida in tropical soils

The aim of this study is to evaluate the toxicity of the fipronil and its metabolites, fipronil sulfone and fipronil desulfinyl on Folsomia candida. Three types of soils were used to perform the ecotoxicological tests, two natural soils (Oxisol and Entisol), and an artificial substrate (Tropical Artificial Soil). The treatments consisted of increasing doses of a veterinary medicinal product with active ingredient based on fipronil, and of its two main metabolites, fipronil sulfone and fipronil desulfinyl. The doses of fipronil were 0.00, 0.02, 0.04, 0.08, 0.15, 0.30, 0.60, and 1.00 mg kg−1 of the active ingredient. For fipronil sulfone and fipronil desulfinyl the doses tested were: 0.00, 0.01, 0.02, 0.04, 0.06, 0.08, 0.15, 0.30, 0.60, 1.00, and 5.00 mg kg−1. The effects of toxicity on F. candida were evaluated by survival and reproduction tests, based on the methods described by ISO 11267. There was a completely randomized design, with six replicates for the fipronil tests and eight for the metabolites. We show that fipronil and its metabolites, even at very low concentrations, are toxic to F. candida. Reduction of reproduction can be observed at concentrations of 0.15 mg kg−1. There was little difference in toxicity (LC50 and EC50) between fipronil and its metabolites. Rather, differences were related more to soil type, where the artificial soil was more sensitive than the two natural soils (Oxisol and Entisol). We conclude that it is important to perform ecotoxicological tests in natural soils, in order to generate more realistic representations of veterinary drug toxicity on the environment.