Interim report on phase 1 and 2 of the supplementary investigation of Ra-226 in harbour sludge polders
Tussenrapportage over fase 1 en 2 van het vervolgonderzoek naar Ra-226 in havenspeciepoldergronden
Stoop P , Pennders RMJ , Lembrechts JFMM
RIVM Report 610058001
An increasing concern for the risks from radon(Rn-222)in particular) has caused the Ministry of VROM to ask for an investigation of the relation between radon concentrations in the indoor air of dwellings and the radium content of the soil on which these have been built. This investigation should include not only natural soil types but also some artificial ones. The soils that were formed after polders were filled with harbour sludge are an example of a non-natural soil type with a radium content that is in some instances significantly higher than that of most natural soils. This report brings the results of the first two phases of a project to investigate the radium contents of these so-called harbour sludge polders. Analysis of the radium contents and a number of soil characteristics of 30 harbour sludge polders shows: (1) the average radium content of most of these sites is higher than expected based on a natural situation, (2) the highest average radium content is approximately four times the average value for Dutch soils, (3) the radium surplus is related to the cadmium pollution level, (4) the average radium contents in the polders on which dwellings have been built are probably too small to allow differences in radon concentrations to show up in an investigation in which a limited number of dwellings are compared with similar dwellings built on soils without a radium surplus. This report ends with conclusions and recommendations for phases 3 and 4 of this project.