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Calculating homely radon's daughters.

Calculating homely radon's daughters

"Radon in houses is now believed to be causing more deaths than all other types of radiation exposure--natural and manmade --combined,' says University of Pittsburgh health physicist Bernard Cohen in a new report. The decay product of naturally occurring radium, radon is released by rocks, soil and groundwater. Most of the radon found in homes enters from the soil, through basement floors. In order to plan radoncontrol strategies for homeowners in areas where background levels of the radioactive ags are high, one has to know what factors most affect exposure to radon, and its decay products, at home. And that is the subject of a study by Cohen and another by Miron Israeli of lsrael, who was a visting scientist with the Environmental Protection Agency (EPA). Both studies are reported in the most recent (December) HEALTH PHYSICS.

"Radon is an inert gas; you breathe it in and breathe it out--it doesn't stick,' explains Allan Richardson of the EPA's Office of Radiation in Washington, D.C. But as electrically charged ions, radon's decay products--or "daughters'--will adhere to surfaces, including minute airborne particles. If those particles are breathed into and adhere to the lung, the attached daughters will get a permanent home from which to irradiate the lung. He says that's why, from a health perspective, the daughters are the real cause for concern.

In an 18-month EPA study in radon-rich Butte, Mont., Israeli collected data from 70 to 80 heavily monitored homes. Data from a subset of 20 homes monitored continuously for 12 months showed that even where indoor radon levels varied little, radon-daughter levels could double, depending on whether the inhabitants smoked. The reason, Richardson says, is that once the daughters adhere to smoke particles, their speed slows down by a factor of 10. A major mechanism for removing radon daughters from the breathable air is their adherence to walls and furniture; the more slowly they move, the longer they take to reach a wall.

Israeli also observed a sharp decrease in airborne daughters during winter months. He speculates that they may be more likely to adhere to surfaces in winter, perhaps because of static-electricity buildup.

Cohen's year-long survey of 169 Pittsburgh-area homes showed that in general, radon levels were lower in drafty houses and in homes sheltered from high winds. While basement levels were predictably highest, forced-air heating systems moved more of that radon-rich basement air upstairs than did radiator heating systems. Richardson points out that though forced-air systems may increase radon upstairs, they may also reduce airborne daughters by accelerating their natural movement toward surfaces to which they can adhere.
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Title Annotation:radon's decay products as health hazard
Publication:Science News
Date:Jan 18, 1986
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