Technical evaluation of the Intervention Values for Soil/sediment and Groundwater. Human and ecotoxicological risk assessment and derivation of risk limits for soil, aquatic sediment and groundwater

Serious Risk Concentrations (SRCs, formerly called SCC) are revised for soil and groundwater; in addition SRCs are derived for sediment. A policy phase will start in 2001 to determine how the results will be implemented for setting Intervention Values. Starting points for the derivation of SRCs, partly chosen because of the policy context in which the SRCs are used, are mentioned and discussed. The general procedure for deriving these risk limits is partly modified, especially for groundwater.

The methodology for deriving SRCs for sediment is new, as sediment had not been considered separately earlier. All parts of the human and ecotoxicological risk assessment were evaluated and revised when necessary. For deriving the human risk limit (SRChuman) the model concepts for human exposure pathways (i.e. soil ingestion, crop consumption and inhalation of indoor air), the model input parameters (e.g. physicochemical data), and the human-toxicological Maximal Permissible Risk level (MPR) are revised. For deriving the ecotoxicological risk limits (SRCeco) the HC50s, the concentrations where 50% of the tested species/processes may encounter adverse effects, the procedure and data were revised. The lowest value for each of SRCeco and SRChuman is selected as the integrated SRC. Ecotoxicological risks more frequently determine the integrated SRCs for soil and sediment than human toxicological risks.

For groundwater the integrated SRC is often based on ecotoxicological risks and on the maximum concentration in drinking water (when groundwater would be directly used for human consumption). The proposed risk limits for soil and sediment are higher and lower than the current Intervention Values for Soil/sediment. The proposed risk limits for groundwater are more often higher than lower compared to the current Intervention Values for Groundwater. It can be concluded that in the present report consistently derived human and ecotoxicological risk limits are given, which give a solid foundation for setting Intervention Values in the policy phase.