Radon is a product of the radioactive decay of the element radium. It is an invisible, odorless, tasteless substance. It comes to us as part of a chain of radioactive transformations, that started with uranium about four billion years ago. With a half- life of only 3.8 days, Radon isn't around very long before it transforms into another element, Polonium, and so on, finally reaching a stable form of Lead. Because it is an inert gas, Radon is particularly mobile, able to move directly through the soil or indirectly through well water. And it is continually being replenished from minerals in the earth.
How Radon Affects Humans
Radon travels in and out of the body with the air that we breathe. The risk to humans is when its particles of decay, particularly high energy alpha particles, come in contact with respiratory tissue. When these particles travel through matter, they knock electrons off molecules, causing them to be broken or changed. Should this happen to a DNA molecule in a cell, the function of the cell could be altered, particularly when the cell reproduces itself. Most of the time the body's defenses will repair or replace the affected cells. But sometimes this kind of damage will contribute to cancer.
What are the Health Risks
More than 6 out of every 100 deaths in the USA are caused by lung cancer. About 80-85% of those deaths are attributable to smoking. Radon is the second leading cause of respiratory cancer. Asbestos is third. The EPA has estimated that living in a house with a radon level of 10 pCi/L in the air is equivalent to smoking one pack of cigarettes a day. The estimate on the number of lung cancer deaths that can be attributed to Radon is 14,000 per year (USA).
How It Gets Into Homes
The Radon we are most concerned with comes out of the soil as a gas. It is able to diffuse through openings in the structure or though porous materials. Sometimes an upward flow of air in homes called the "stack effect", creates pressure differentials that cause soil gases to be sucked into the home. Radon can also come into the home with the well water, where it is then released into the air though the shower, dishwasher, and laundry machine.
What About My House
The only way to find out about your home is to have it tested. Low level radioactivity is measured in picocurries per liter (pCi/L). The average radon concentration of outside air is roughly 0.4 pCi/L. The average radon level found indoors is estimated to be 1.3 pCi/L. The EPA has determined that homes with test results of 4.0 pCi/L or higher present an unacceptable health risk, and should be fixed.
About 1 in 15 homes in the USA has levels above 4.0 pCi/L. In Northern Virginia, particularly the area west of Interstate 95, the incidence is higher (Some zip codes tested as high as 1 in 3). For more information, see EPA Map of Radon Zones .
The Surgeon General and the EPA recommend that you test your home.
Fixing a Home with High Radon
The standard treatment for treating high risk homes is called sub-slab depressurization, where a fan/pipe system is installed to remove soil gases that collect underneath the home. Radon mitigation contractors seal floor cracks as part of the treatment. The cost to install a Radon reduction system usually falls between $1000-1800 for an average size dwelling, and should be viewed as an investment in safer indoor air quality.
For more information on this topic, visit www.epa.gov/radon.