Risk assessment of pesticides for soils of the Central Amazon, Brazil: comparing outcomes with temperate and tropical data.

The risk of 11 pesticides to the soil environment was assessed in a 3-tiered approach at 4 sites located in Central Amazon, near Manaus, the capital of the Amazonas State in Brazil. Toxicity-exposure ratios (TERs), as routinely used for the registration of pesticides in the European Union, were calculated. First, the predicted environmental concentration (PEC) values in soil on the basis of real application rates and soil properties but temperate DT50 (degradation time of 50%) values were compared with temperate effect values (earthworm LC50s; median lethal concentrations), both gained from literature. Second, the risk assessment was refined by the use of DT50 values from tropical soils (measured for 7 compounds and estimated for 4) but still with temperate effect values because only a few results from tests performed under tropical conditions are available. Third, the outcome of this exercise was evaluated in a plausibility check with the use of the few results of effect tests, which were performed under tropical conditions. However, the lack of such data allowed this check only for 6 of 11 pesticides. The results are discussed in light of pesticide use in the Amazon in general, as well as compared with the registration status of these pesticides in other countries. Finally, suggestions are given for which kinds of studies are needed to improve the environmental risk assessment of pesticides in tropical regions.