Indoor Radon
PORN SRI POLPONG, M.Sc. Rad. Sci.* SOMCHAI BOVORNKITTI, M.D., D.Sc.Med.**
Affiliation : * Office of Atomic Energy for Peace, Ministry of Science, Technology and Environment, Bangkok 10220, ** Department of Medicine, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand.
Abstract
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 follow-
ing 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 resis-
tance 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 inves-
tigated 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.
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