Parameters causing variation between soil screening values and the effect of harmonization

Background, aim, and scope This paper discusses the variation between generic soil screening values (SSV) from 17 countries for 11 volatile organic contaminants (VOC). The variation between SSV was one to four orders-of-magnitude (OOM) depending on the SSV and landuse type. What would be the variation if parameter values are harmonized between member states? Main Features The effect of harmonization was visualized by firstly reviewing the technical derivation procedure for SSV for 7 SSV from five countries and collecting all parameter values that are involved in the deviation. The parameters were subdivided in scientific (e.g. algorithm plus its parameter values), political (e.g. toxicological reference) or geographical (e.g. building and soil properties) elements. Secondly, new SSV were calculated with progressively harmonized sets of scientific and/or political parameter values, while the geographical parameters varied. Thirdly, the variation between SSV was compared before and after harmonization. Results Results show that harmonizing algorithms plus other scientific and political parameters are suited for harmonization. The variation decreases to I OOM, after scientific and political parameters were harmonized. Geographical parameters seem to have less impact on the differences between SSV. Discussion So, should we harmonize the procedures for deriving SSV between EU member states? The need for discussing harmonization is also raised by the upcoming EU Soil Framework Directive. Conclusions Clearly common generic SSV across all of Europe are not appropriate, since countries are allowed to include member state specific geographical and cultural elements and also political decision making. By harmonizing scientific and/or political parameters differences between SSV can be made more transparent between member states and it will encourage convergence in procedures among member states to ensure neutral conditions of competition and a coherent soil protection regime throughout Europe. Recommendations and perspectives To promote uniformity it is recommended to construct a toolbox for the calculation of human health risk exposure, carried by a European consensus, that includes different model algorithms for which fixed and flexible input parameters are made available. Fixed algorithm parameters are standardized and applied uniformly by all member states, e.g. physicochemical parameters, while flexible input parameters permits member states to include region or country specific parameter values and policy decisions.