Chemical contamination and the ecological quality of surface water

Baas, J. and Kooijman, S. A. L. M. 2010.
Chemical contamination and the ecological quality of surface water. Envir. Pollut. 158: 1603 - 1607


To assess the quality of surface waters, the typical procedure that is followed that a land use survey is conducted and based on this the concentration of contaminants in the surface water is monitored. The concentration of all the measured contaminants is subsequently compared with their respective Maximum Permissible Concentrations (MPCs). This approach leads to a number of questions, most importantly (assuming that the right contaminants measured): How bad is it if MPCs are exceeded? And: Is the water quality good if no MPC are exceeded? We tried to answer these questions by comparing MPCs to observed and calculated effects of contaminants in Dutch surface waters. We show that there are shortcomings underlying the concepts of the MPCs. And therefore we can not be sure that the water quality is okay if MPCs are not exceeded. Neither can we be certain that the water quality is not safe (for 95 % of all species) if MPCs are exceeded. The lack of relation between exceeding MPCs and mortality amongst in situ exposed daphnids underlines this. It is possible to have a daphnid population go extinct within 30 hours of exposure when it is exposed to a mixture of metals or pesticides at the concentration level of the maximum permissible concentration. We conclude that the MPCs aim to protect 95% of all species is not met for a number of compounds taken up in our analysis. Especially if organisms are exposed to mixtures of metals or pesticides, as they are in the environment, the objectives of the MPCs are not met. Specifically the MPC for cadmium and the ad hoc MPC of 2 ng/l that is used for some pesticides are not strict enough. Especially for the more potent insecticides, like diazinone.

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This paper is highlighted by Science for Environment Policy; DG Environment New Alert Service