RESUMO
A preliminary study of indoor radon was carried out at 176 sites in different buildings in Bangkok (n = 83), Nonthaburi (n = 79), Pathumthani (n = 7), Samutsakorn (n = 3), Samutprakarn (n = 2), and Nakornpathom (n = 2). Elevated radon concentrations were encountered in 19.28 per cent of the buildings in Bangkok and in 29.11 per cent of the buildings in Nonthaburi. Levels were not beyond the threshold in the four other provinces. The prevalence of buildings with elevated radon concentrations between Bangkok and Nonthaburi showed no statistically significant difference (P > 0.05). The arithmetic means and the standard deviations of the elevated concentrations were 226.31 +/- 81.95 Bq.m-3 for Bangkok and 417.96 +/- 455.27 Bq.m-3 for Nonthaburi. With regard to the age of the buildings, those less than five years old had a higher rate of elevated radon concentration when compared with buildings five or more years old (P = 0.60 = no statistical difference). There was evidence suggesting that poor ventilation might be a factor in the elevated concentrations of indoor radon.