Relative risks of transformation products of pesticides for aquatic ecosystems

In this study, the availability of physico-chemical and ecotoxicological in formation on 78 transformation products for 20 regularly used pesticides in the open literature is evaluated. Based on this information, it is attempt ed to predict the relative risk for the aquatic environment of each transfo rmation product in comparison to its parent pesticide. It is concluded that for the 78 transformation products selected, the data set on physico-chemi cal and ecotoxicological behaviour is not very large. Measured log K-ow val ues and other physico-chemical properties are known for only 30-40% of the selected transformation products. The overall reliability of the collected physicochemical values is considered to be moderate to slight, while for th e ecotoxicological data set, reliability is considered to be sufficient. In many cases, there is a need for more information especially on the persist ency and no-observed-effect concentrations of the pesticide's transformatio n products. In general, over 50% of the transformation products of triazine s, carbamates and phenoxypropionic acids pose, in theory, a similar to high er risk than their parent pesticide, while over 50% of the transformation p roducts of synthetic pyrethroids, organophosporous pesticides and dithiocar bamates probably pose less risk. High risk was expected for products with h igh accumulation or persistency in sediment and/or high toxicity together w ith considerable bioaccumulation (potential) or relatively high concentrati ons or persistency in water. A generalization of the joint features that ca used an increased risk for ecosystems could not be made for most pesticide classes. Exceptions are the synthetic pyrethroids, for which transformation products with a similar or even higher log K-ow than the parent pesticide caused an increased potential risk, while for the carbamates the presence o f the carbamate group in the transformation product was the joint character istic of chemicals with predicted increased risk. For three transformation products, monitoring data based on concentrations measured in surface water in The Netherlands were compared with maximum permissible concentrations. This comparison indicated that two of these compounds pose a potential risk of adverse effects in the held situation in Dutch aquatic ecosystems. For all other transformation products, the potential risk in the field situatio n could not be established because of the absence of monitoring data. (C) 1 998 Elsevier Science B.V. All rights reserved.