Japan-China cooperative study has been carried out since 1991.
The data obtained until 1995 was published in Journal of Radiation Research 41. Suppl. (2000).

	Farm village in Yangjiang.
Brick production using the clay obtained near-by field. The brick has high radioactivity. Thus inside the buildings made of these bricks, radon concentration and γ-ray dose are very high. Indoor γ-ray doses in control and high background areas are shown in the next figure. Details of the villages indicated by red mark can been seen in the attached table.
Comparison of total radiation dose in Madi and Hengpizai village

Frequency distribution of the individual dose rates
in HBRA and CA (measured by TLD).