|
Sci Tech
Radon: source of radiation hazard in your homes
|
Indoor radon causes 1,000 to 2,000 cases of lung cancer in the U.K. each year
|
Radon is a radioactive gas formed by the decay of radium which is present in all rocks and soils The progress in controlling radiation exposures from radon has been very slow
On November 12, this year, the UK Health Protection Agency (HPA) and the British Geological Survey jointly published a radon atlas which overviews radon affected areas by one km squares of the national grid. Radon is an invisible, tasteless, odourless, radioactive gas formed by the decay of radium which is present in all rocks and soils. Radon enters homes through cracks and openings and as a contaminant in water and cooking gas.
The levels of radon in homes depend on underlying geology, construction methods of the building and the way we heat and ventilate the building.
Cancer risks
Radon decays into a series of products; some of these produce alpha radiation. High exposures to such radiation are known to increase the risk of lung cancer. Based on an analysis of 13 case-control studies, European researchers reported that exposure to radon gas in the home accounts for about 9 per cent of lung cancer deaths and about 2 per cent of overall cancer deaths in Europe (British Medical Journal, 2005).
Several regulatory agencies highlighted the radiological safety significance of radon.
HPA estimates that indoor radon causes 1,000 to 2,000 cases of lung cancer in the U.K. each year. Risk from radon to smokers is particularly high. In an advisory issued in January 2005, the US Surgeon General said that radon is the second leading cause of lung cancer in the U.S. (smoking is first) and causes more than 20,000 lung cancer deaths annually.
The lower end of the annual dose range to the people who live in homes with radon concentrations at or above an action level of 200 Bq per cubic metre of air is about 10 mSv. The highest doses are well in excess of 100mSv. (Bq is a unit of radioactivity; in a radioactive material containing one Bq of radioactivity one atom disintegrates every sec; mSv is a unit of radiation dose; the skin dose in a chest x-ray examination is about one mSv; the average radiation dose to a worker in a modern nuclear power plant is a few mSv).
More doses
In some areas of United Kingdom, persons in 5 per cent of the homes are exposed to doses above 23.7 mSv/year. One per cent of the houses show dose values above 55.8 mSv/year. The highest estimated dose was 320 mSv/year in Cornwall.
The annual dose limit to radiation workers recommended by the International Commission on Radiological Protection is 50 mSv. Many people in New Jersey and Pennsylvania get more radiation from radon in a week than anybody ever got at Three Mile Island. (Gerald Nicholls in Newsweek, August 18, 1986). Three Mile Island at Pennsylvania is the site at which the most serious nuclear reactor accident in America occurred.
Radon policies
HPA’s radon policies state that existing homes in affected areas should have radon measurements; radon concentrations at or above the Action Level of 200 Bq m{+-}{+3} should be reduced to as low as reasonably practicable.
New homes built within localities delimited by the appropriate Government authorities should be constructed with precautions against radon.
According to the US Environmental Protection Agency (EPA), 1 in 15 U.S. homes have excessive levels of radon.
The agency provides a county-by-county map of the estimated radon levels on its Web site. The nation celebrates a week in the month of October as ‘Radon Action Week’ to highlight the importance of reducing radon levels in dwellings. This year it was October 21-27, 2007. EPA published a ‘Home buyer’s and seller’s guide to radon.’
Remedial action
The agency recommended that buyers and sellers of homes must test them for radon.
Based on the results of a co-ordinated research project sponsored by the Department of Atomic Energy in eight universities and a few research institutions in India, scientists at the Bhabha Atomic Research Centre concluded that dwellings in India do not need any remedial action against radon because they have adequate ventilation (BARC, 2003).
The progress in controlling radiation exposures from radon has been very slow. Staggering amounts of radon at home get scant attention. A trivial amount of caesium-137 at sea at the discharge point of a nuclear installation gets all the attention.
( ksparth@yahoo.co.uk)
K.S. PARTHASARATHY
Former Secretary, AERB
Printer friendly
page
Send this article to Friends by
E-Mail
Sci Tech
|
