Screening for risk assessment around closed uranium mining sites

The aim of this study is to present the environmental impact and health risk 20 years after the closing of the uranium mining industry. The areas under observation are 31 former classical underground uranium mining and exploratory sites in Bulgaria. The geometric mean value of the gamma dose rate (0.33 mu Sv h(-1)), measured 1 m above ground in the mining sites, was three times higher than the mean of the gamma dose in the nearby settlements (0.11 mu Sv h(-1)). The geometric mean of specific activities for U-238, Ra-226, Th-232, K-40 and Pb-210 in mining site soil was found to be: 437 Bq kg(-1), 291 Bq kg(-1), 65Bq kg(-1), 835 Bq kg(-1) and 318 Bq kg(-1), respectively. Analysis of variance and correlation were applied. The external dose and offsite external hazard index, as health risk indicators, were estimated based on the results. After twenty years there is still environmental contamination in some locations that may cause a health risk, so remediation and monitoring should continue and be maintained.