Radon indoors

Radon is the biggest possible contribution to radiation exposure in houses (50%) that occurs naturally [13] and as a gas, it has no taste, smell or colour. Radon exists 

Radioactive decay of radon forms particles called radon daughters which, after inhalation, can damage lung tissues leading to cancer [20]. 

Radon levels indoors can be measured by a safe and a rather simple method by use of detectors, one in the living room and another in an occupied bedroom. In one experiment (in UK), the detectors used are just a piece of spectacle lens plastic put in a protective shell, about the size and shape of a small door knob (obtainable through mail order in some 

Indoor radon measurements obtained for homes in North Virginia, USA, revealed that existing high or low median indoor radon levels in each house persist through four seasons [25], however, attempts to compare the soil radon and soil permeability was not successful. 

2 Some Measures to Prevent Radon Accumulation Indoors 

The National Academy of Sciences of US estimated that radon from soil causes 15-22,000 deaths from lung cancer each year in the US. 

The EPA set a concentration of 4 pCi/1 of air inside homes as an action level, the average radon level in homes is normally around 1.25 pCi/1. Although there is US Congress Legislation from 1988 establishing the goal not to exceed 0.2-0.7 pCi/1 in homes, this has not been found to be practical because of radon levels in ambient air indoors. 

One can also be exposed to radon by ingestion of underground water that is contaminated with radon. 

Radon is existing everywhere but it is usually in insignificant levels that pose negligible health risk normally. It is a radiocative decay product of uranium (over radium). Uranium is usually found in all soil and rocks in small quantities varying from place to place, and radon also exists everywhere in varying amounts. 

The concentration of radon is higher indoors than outdoors for three reasons. Air movement is less. Radon is exhaled from walls as well as from the floor. Slight negative pressures indoors, caused by heating and by effects of wind, draw in air from the soil below (Nero Nazaroff, 1984). There may be continual circulation, whereby air is drawn down through the soil round the building, then up through the floor. 

A grossly oversimplified calculation shows the first effect. If Xi Xo are the concentrations of radon in a groundfloor room and outside, Q the rate of exhalation from the floor, assumed to be the same as from the ground outside, H the height of the room and Xv the ventilation rate, then neglecting exhalation from the walls 

Typically, Xv is about 3 x 10-4 s-1 (one air change per hour), and H about 2.5 m, giving (xi — XoVQ = 1300sm-1. If Xo is typically 5 Bqm-3, and Q is 20 mBq m-2 s-1, this gives Xi = 31 Bq m-3. This is sufficient to account for radon concentrations found in many houses, apart from the additional effect of pressure differentials. 

The Department of the Environment (1988) has published a guide to the reduction of radon levels in homes. Ground floors can be sealed with plastic sheets, or, as a more drastic measure, a sub-floor suction system, exhausting the upwards flow of radon to atmosphere, can be installed. 

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Problems that rank relatively high in cancer and non-cancer health risks but low in ecological and welfare risks include hazardous air pollutants, indoor radon, indoor air pollution other than radon, pesticide application, exposure to consumer products, and worker exposures to chemicals... 

Sextro, R.G., Understanding the Origin of Radon Indoors--Building a Predictive Capability, Report LBL-20210, Lawrence Berkeley Laboratory, Berkeley CA (1985), submitted to Atmos. Environ. 

Nero, A.V. Nazaroff, W.W. (1984) Characterizing the source of radon indoors. Radiation Protection Dosimetry, 7, 23-9. 

Cancer registries (http //www.cdc.gov/cancer/npcr/) Radon, indoor air quality (http //www.ehso.com/ ehshome/radon.htm)... 

Indoor radon levels were measured in homes located in the Reading Prong area of Pennsylvania. This area has an unusual abundance of homes with high radon concentrations that is presumed to be from geologically produced emanation of radon. Indoor levels of radon in this area ranged from 4 to 20 pCi/L (150 to 740 Bq/m ) in 29% of the homes to >80 pCi/L (3,000 Bq/m ) in 1% of the homes (Fleischer 1986). 

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