Total Indicative Dose Determination in Water from the North Riviera Well Field of SODECI in Abidjan, Cote d’Ivoire

The Uranium-238 (238U), Thorium-232 (232Th) families and Potassium-40 (40K) are of terrestrial origin and contribute generally to an individual’s external exposure through our presence in this environment. They also contribute to the internal exposure through the ingestion of products and beverages such as water that are close to the earth. The aim of this work is to determine the committed effective dose or Total Indicative Dose (TID) due to gamma radioactivity of the borehole water from the Nord Riviera (NR) well field operated by the Côte d’Ivoire Water Distribution Company (SODECI) for the supply of drinking water to part of the population of Abidjan. In addition, the populations, with their habits, could use these borehole waters directly as drinking water. To this end, water samples from the seven (07) functional boreholes were collected and analyzed on a gamma spectrometry chain, equipped with an HPGe detector in the laboratory of the Radiation Protection Institute (RPI) of the GHANA Atomic Energy Commission (GAEC). The results of the specific activities of 238U, 232Th and 40K obtained were transcribed into TID. As the natural radioactivity of the borehole water is high [1], the TIDs calculated from the activity results of the natural radionuclides238U, 232Th, and 40K vary for the seven boreholes from 0.150 to 0.166 mSv/yr with an average of 0.161 ± 0.034 mSv/yr. The TID of the control tower, where the borehole water is mixed and treated for household use, is equal to 0.136 ± 0.03 mSv/yr. The TIDs obtained are therefore all slightly greater than the WHO reference dose value of 0.1 mSv/yr. But all remain below the UNSCEAR reference dose of 0.29 mSv/yr.

Determination of thorium in the hair and urine of workers and the public in a rare earth mining area

Objective:To assess the thorium exposure of the mine workers and the public to a typical rare earth mine and estimate the resultant committed effective dose to them.Methods:A total of 79 volunteers were selected in this survey,including 69 mine workers and 10 local residents living about 4 km away from the mine site.Urinary samples were collected from 79 volunteers,with 65 hair samples from 57 workers and 8 local residents.The thorium concentrations in urinary and hair samples were determined by using inductively coupled plasma mass spectrometry.The committed effective doses were estimated based on the urinary samples collected and the parameters as recommended by ICRP Publication 137.Results:Thorium concentrations in the samples from the workers ranged from 19.0 to 2388.8 ng/g in hair with median of 149.8 ng/g,and in urine 18.3–906.1 ng/L with median of 59.6 ng/L,respectively.The median values of thorium concentrations were 11.8 ng/g in hair and 32.40 ng/L in urine for the public respectively.The thorium concentrations in urinary and hair samples of the workers were not only higher than those of the residents in the local area,but also than those of non-occupationally exposed populations as reported.The median values of committed effective dose were estimated to be 1.51 mSv for the workers and 781μSv for the local residents,respectively.Conclusions:The residents in the local area,and especially the workers,have been subject to long term thorium exposure.More attention should be paid to the radiological hazards of thorium to the workers and local residents.