An investigation of environmental radiation and dosimetry was carried out in the background radiation area of Guangdong Province of China. The surface soil of the background and control areas were analysed by both radiochemical procedure and gamma ray spectrometry. The results revealed that the concentrations of uranium and radium are about 5 times higher than those in the control area, and the thorium has a higher value in the background area, about 6-7 times more than that in the control area. The higher content of natural radionuclides in this area raised the environmental radiation level. Environmental cumulative exposures and resultant inhabitant exposure rates were measured in the background area with Photoluminescent dosimeters and TLD CaSO₄(Dy), and an average figure of 300 mR/yr for the inhabitants was estimated (110 mR/yr for those in the control area). To determine the internal doses resulting from the deposition of natural radionuclides in the body tissue, we compared the data obtained by different methods and procedures adopted in this investigation. The results obtained by measurements of ²²²Rn and ²²⁰Rn in the exhaled breath of healthy inhabitants, by radiochemical analyses of the adults'' teeth, from dietary investigation and of radiochemical analyses of foodstuff and drinking water suggested that the activity concentrations of 226Ra and 228Ra in human bones in the background area are about 3-5 times higher than that in the control area. After comparing these data, annual absorbed doses of red bone marrow and bone surface from ²²⁶Ra and ²²⁸Ra were estimated.

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