This paper is the result of health geological survey engineering.

Objective Through a comprehensive radiological survey in a natural high-background radiation area in western Guangdong, we estimated the annual effective dose to residents from terrestrial gamma radiation and ²²²Rn radiation, and evaluated the radiological safety of the region.

Methods Activity concentrations of natural radionuclides (²³⁸U, ²³²Th, ⁴⁰K) in surface soil, terrestrial gamma radiation dose rates, and ²²²Rn concentrations in both soil gas and indoor air were systematically measured. The annual effective dose equivalent to the public arising from natural radiation was then calculated, and the radiological safety of the high-background environment was assessed.

Results The activity concentrations of natural radionuclides in surface soil averaged (51.9±24.6) Bq/kg, (77.0±19.1) Bq/kg and (365.7±192.2) Bq/kg for ²³⁸U, ²³²Th and ⁴⁰K, respectively. The mean ambient gamma radiation dose rate was (79.8±28.7) nGy/h. Soil-gas ²²²Rn averaged (23901±11672) Bq/m³, while indoor ²²²Rn averaged (87.4±72.5) Bq/m³. With the exception of ⁴⁰K, all other radiation indicators exceeded the national averages, indicating the characteristics of high natural radiation background in the study area. The radiation indicators show distribution patterns consistent with geological conditions, yet exhibit distinct local-scale variations. The estimated annual effective dose from terrestrial gamma radiation in the study area was averaged 0.71 mSv, which was higher than the national average (0.54 mSv). However, it remained within the global terrestrial gamma background fluctuation range (0.3~1.0 mSv/a), and the associated external exposure risk to the population is therefore negligible. All indoor ²²²Rn concentrations in the study area fell within the national control requirements for indoor radon and its progeny. No significant health risks were associated with indoor radon exposure in the study area.

Conclusions The radiation environment in the study area exhibits significant high-background characteristics, yet the resulting exposure does not exceed the control requirements stipulated by the national standards. Nevertheless, it is recommended to monitoring the cumulative health effects of chronic exposure to high-background level of natural radiation is recommended.