Health risks associated with exposure to high concentrations of radon gas have been known for decades, however it wasn’t until December 1984 that it was discovered that people in homes can also be exposed to high concentrations of radon resulting from uranium deposits in the soil on which the houses are built.
Radon gas is present in varying quantities in the atmosphere and soils across the world. It is a colorless, odorless and tasteless gas, produced by the natural radioactive decay of uranium deposits in the earth. According to the United States EPA (Environmental Protection Agency), scientists estimate that between 5,000 and 20,000 lung-cancer deaths a year in the U.S. can be attributed to radon gas exposure.
The concentration of radon in the air is measured in units of picocuries per liter of air (pCi/l). The EPA has set guidelines for radon levels in residential structures, based on currently available information: their “action level” is 4 pCi/l, meaning no action is needed if the radon concentration is below 4 pCi/l. However, the agency acknowledges that even the action level is not risk free, because exposure to an annual radon level of 4 pCi/l is equivalent to the risk of smoking ten cigarettes a day or having 200 chest X-rays a year. Still, the action level was set at 4 pCi/l because in some cases reduction below that level might be very difficult or even impossible to achieve.
Although radon is present in soils across the world, not every house has a problem with high radon gas levels. One house may have a very low radon concentration, while an adjacent one may have a very high level. It all depends on the construction of the house, the uranium-radium content in the soil, as well as geological formation below the house. The only way to determine of a house has a radon problem is to have a professional radon inspection.
The radon concentration in a house varies with time, as it is affected by a several environmental factors such as rain, snow, barometric pressure, direction of wind relative to open windows, and by induced negative pressures caused by periodic use of exhaust fans, attic fans, fireplaces and heating systems. The most adequate way of testing the average annual radon concentration is to perform a long-term test. On the other hand, time is always an issue in real estate transactions, making a long-term test rather unpractical, so a charcoal canister with a test period of three to seven days is generally used.
Radon is a gas, so it can easily seep into the lower level of the house through dirt floors, cracks in concrete floors and walls, sump pits, floor drains, open joints and small cracks or pores in hollow block walls. In many areas, professional home inspection companies offer radon testing services as well. Both home buyers and home sellers must be aware that a home should be tested for radon to avoid serious health hazards. Even if tests determine that a house has a high radon concentration, the condition can be corrected at a reasonable cost.
Prevention and Control – Methods to Reduce Radon Levels
Several methods have proved successful in reducing concentration levels of radon in homes to a point below “action level”. For instance, a very effective mitigation procedure is to use a four-inch plastic pipe with an in-line fan that vents the radon gas from below the floor slab to above the roof. Correcting the problem, however, is not a do-it-yourself project, but should done by a qualified radon-mitigation contractor that has completed the requirements for listing under the U.S. EPA’s Radon Contractor Proficiency Program.