Exposure to radon/radon decay products in waterworks

In accordance with the Basic Standards of Radiation Protection issued by EURATOM and the recommendations of the Federal Commission of Radiation Protection (SSK), radon measurements were carried out at 80 of a total of 240 waterworks in the state of Baden-Wrttemberg from the end of 1994 to mid-1997. The measurements covered more than 1000 working places. The waterworks were selected among others on the basis of the number of employees, the size of the supply area, the geological and hydrological parameters, and the surface coverage. A major part of the measurements consisted in determining the actual times that were spent by the employees at the respective working places. In the 80 waterworks, about 700 persons are employed and they spend an average of about 180 hours at their working places. In cases of an extremely high concentration, talks were conducted with the waterworks management and methods were proposed for the reduction of the exposure, part of which were implemented. This resulted in a series of rather detailed verification measurements. The following results were obtained: For more than 15% of the 1000 operating points measured, the radon decay product concentration exceeded one working level which is considered the upper limit for a working time of 170 hours (=1 month) per year according to the SSK recommendation of 30 June 1994. The highest concentrations varied between 10 and 20 WL (=40-70 kBq DP m-3). When combining the respective operating points and regarding the entire waterworks, a mean concentration value of 1 WL is exceeded by about 10% of the waterworks. This means that the working places of about 80 employees drop out of the ?normal range?. In addition to the statistic results, a detailed measurement (case study) shall be presented and proposals shall be made with regard to the remediation of the contamination paths.