Indoor radon.

The naturally radioactive but chemically inert gas, radon, is formed from the radioactive decay of radium which is part of the uranium series. Radon gas, which has a half life of 3.8 days, must escape from soil particles through air-filled pores in order to enter the atmosphere following the decay of radium. The concentration of radon in the atmosphere varies, depending on the place, time, height above the ground and meteorological conditions. It is thus an inescapable source of radiation exposure, both at home and at work. The potential hazards posed by exposure to radiation from indoor radon gas and its daughter products are of great concern worldwide. Noting of an excessive lung cancer risk among several groups of underground miners exposed to radon and its daughter products, studies on radon concentrations in the workplace and in dwellings have been conducted in many countries. The results have shown that the distribution of radon concentrations are approximately lognormal from which population weighted; the arithmetic mean of radon concentration of 40 Bq.m-3 has been adopted worldwide for dwellings and workplaces. The principal methods for reducing a high indoor radon concentration are: reducing the radon supply by reversing the pressure difference between the building and the soil; raising the resistance of the foundations to soil gas entry; removing the radon sources such as water or underlying soil; diluting the concentration by increasing the ventilation rate; and reducing the concentration of radon progeny by filtering and increasing the circulation of indoor air. Buildings which have a radon concentration higher than 200 Bq.m-3 should be investigated by the national authorities concerned; meanwhile, householders should be advised to take simple temporary precautions, such as increasing ventilation, until a permanent remedy can be effected.

Indoor radon in Thailand: a study with particular reference to its sources.

Measurements of radon gas were carried out on each floor of the four tall concrete buildings. The results show clearly that levels of radon concentration on the higher floors of the buildings were mostly comparable and occasionally were much higher than the ground-floor in contact with the earth. Hence, the findings indicate that the source of indoor radon is not only the surrounding soil but also other sources in the buildings, i.e. most likely radium-containing building materials.

A preliminary study of indoor radon in Thailand.

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.