DESIRE FOR LEVELS. Background study for the policy document "Setting Environmental Quality Standards for Water and Soil"

Abstract

The report provides scientific support for setting environmental quality objectives for water, sediment and soil. Quality criteria are not set in this report. Only options for decisions are given. The report is restricted to the derivation of the 'maximally acceptable risk' levels (MAR) for 45 chemicals (metals, PAH, pesticides, chlorophenols). MAR- values for water are primarily derived from chronic toxicity data, following an extrapolation procedure recommended by the Dutch Health Council. If insufficient toxicity data are available to use this procedure, a modified EPA-method that produces indicative values only, has been used. For sediment no toxicity data are available. MAR-values for sediment are therefore derived indirectly from MAR-values for water, using the Equilibrium Partitioning method. MAR-values for soil are derived with ecotoxicological extrapolation methods similar to those used for water. For soil too little toxicity data are available to properly derive MAR-values directly. In addition, MAR for soil are derived from MAR for water with the Equilibrium Partitioning method. Lacking reliable soil-pore water partition coefficients, this does not appear to be a suitable alternative. For metals 'negligible risk' levels in water and sediment are lower than the natural background concentrations. This is not the case for PAH. The 'negligible risk' levels for metals in soil are well below the 'Reference Values for Soil Quality'.<br>