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1 Introduction It is estimated that there are about 6 millions underground coal miners countrywide[1,2]. Available data indicate that not only high radioactivity[3] has been found in coal mines in some areas, but also the exposure from radon and its proge
1 Introduction It is estimated that there are about 6 millions underground coal miners countrywide [1,2]. Available data indicate that not only high radioactivity [3] has been found in coal mines in some areas, but also the exposure from radon and its proge