226Ra and 228Ra activity levels in potable drinking water supplied to pharmaceutical companies in India

The low level 226Ra and 228Ra activities were measured in Potable water samples received by pharmaceutical companies located in Maharashtra, Goa, Gujarat, Madhya Pradesh and Himachal Pradesh through private Borewell Supply and Municipal water Supply units. Radium in drinking water and food enhances the ingestion dose due to its long radiological and biological half-life. The Radium activity level in the fresh water was supposed to be within the limits prescribed by USEPA Guideline for Drinking Water Quality, 40 CFR 141,a Code of Federal Regulation. Higher concentration of Radium can be easily measured by Gamma spectrometry. The paper gives the low levels of radium isotopes present in the water samples which are not detectable successfully by simple gamma spectrometry. A separation chemistry considering Radium isotopes decay scheme and chemical similarity to Calcium was adapted to measure the activity with sequential chemical separation method followed by determining the alpha and beta activity of individual radium isotopes. In bore well water 226Ra activity level was in the range of 0.21 to 60±3.7 mBq/l and 228Ra level was in the range of 5.48 to 111.9±12.2 mBq/l while in Municipal water supply 226Ra and 228Ra was observed to be in the range of 0.32 to 28.89 mBq/l and 2.19 to 117.43 mBq/l respectively. A combined 226Ra+228Ra activity was observed to be in the range of 2.63 to 171.9±12.75 mBq/l which is very much within the prescribed limits. The investigation indicated that 228Ra activity is comparatively more than 226Ra indicating the water source to be from Thorium rich locations.The expected dose assessed was in the range of 13.18 to 0.04 μSv/y which is well within the limit of 0.1 mSv/y. (author)