The National Soil Monitoring Network NABO, in cooperation with the «Wageningen Evaluating Programmes for Analytical Laboratories WEPAL», has conducted proficiency testing for inorganic pollutants since 1989 and for organic pollutants since 1998. Last in 2015, 23 laboratories participated in the proficiency testing programme for inorganic and 11 in the programme for organic pollutants. 14 of the former and 9 of the latter laboratories agreed to disclose their identity and be included in the public laboratory list. This list gives an overview and allows comparison of results between laboratories. Furthermore, it reveals how regularly each laboratory participates, in case the data alone are insufficient for an evaluation of the quality of analysis. Laboratories that participate in proficiency testing programmes and thus can prove comparability of data quality can generally be recommended.
The legal definition of the guide, trigger and clean-up values in the Ordinance on the Pollution of Soil (VBBo) calls for a good comparability of the analyses between laboratories. This can be realised through periodic proficiency testing. The WEPAL offers a proficiency testing programme for interested laboratories. As a consequence, the analyses of the VBBo parameters reach a high standard. The results of the proficiency testing are published annually by the NABO in a public laboratory list. Registration for the proficiency testing programme and inclusion in the list is possible at any time.