Persistence of Coumarins Rodenticidas Brodifacoum and Coumatetralyl in Brazilian Urban Environment

Abstract

The chemical control of Rattus norvegicus in S?o Paulo city has been done using coumarins rodenticides as paraffin block and powder contact. The brodifacoum-paraffin block is placed in culverts and similar sites being subject to the action of the weather that can change the concentration of active ingredient. Whereas coumatetralyl-powder contact is applied on the entrance of the burrows, being subject to the action of the weather, that can help in the active ingredient degradation and its transference to other environments. There is not information on the environmental persistence of these active ingredients in their formulations after placing on the environment. So this research evaluated the persistence of brodifacoum-paraffin block and coumatetralyl-powder contact after two months under environmental conditions. One hundred blocks were put in culverts and weekly, during two months, three blocks were retreated and submitted to extraction and the extract analyzed by high performance liquid chromatography for quantification of active ingredient. The coumatetralyl-powder contact was applied in experimental systems simulating the field conditions. Soil and water samples were collected weekly, for two months, submitted to the extraction and the extracts analyzed by high performance liquid chromatography for quantification of active ingredient. The results pointed the stability of brodi-facoum-paraffin block under real application environmental conditions because 100% of active ingredient was recovered after exposition of the blocks. However, there was decreased about 80% in the concentration of coumatetralyl-powder contact on top soil during two months of environmental exposition, however there was not found it in water sample.