ABSTRACT
During the months of December 1997 and January 1998, a study of indoor radon was carried out on 786 different buildings in 13 districts of Lampang Province in northern Thailand, using the charcoal canister method. The survey revealed the presence of radon gas inside all buildings investigated, varying in concentration from 4.00 to 176.73 becquerels/cubic metre (32.41+21.14 Bq.m-3); an elevated concentration over 150 Bq.m-3 was encountered in only one house in Muangpan district. Although the other measurements did not reveal indoor radon levels exceeding the safety threshold, the prevalence of high levels within normal range was detected among the building in the adjoining four districts (Amphur Muangpan, Amphur Hangchat, Amphur Jaehom and Amphur Koa-ka). With regard to the type, age and ventilation status of the buildings, and the practice of smoking indoors, the findings of this investigation do not conclusively support the notion of their contributing to, or being mutually associated with, indoor gaseous concentrations of radon.