How To Prevent Radon From Invading Buildings
What radon is
Sources of radon
Health problems caused by radon
Decreasing exposure to radon
Steps to reduce exposure
Steps to reduce radon levels
What Radon Is
Radon is a colorless, odorless, tasteless radioactive gas that results naturally from the breakdown (decay) of uranium (a radioactive metal) and radium in soil, rock, or water. As uranium decays, radon gas is released. Typically, uranium is concentrated in areas with a lot of granite, schist, limestone, shale, phosphate, and pitchblende. When radon is released in soil under buildings, it may percolate into the building. Radon is an indoor air hazard because it is a known human carcinogen that can result in lung cancer. Radon is the second leading cause of lung cancer, following smoking, and is the leading cause of lung cancer in nonsmokers.
The discovery of indoor radon concentrations dates to 1984 when Stanley Watras, an engineer at a nuclear power plant in Pennsylvania, set off a radiation detection device on his way into work. Researchers found that his home had a radon level 16 times that allowed for uranium miners. That was because his house sat on top of an old uranium mine. However, radon is not found in every home. In this case, his neighbors did not have a radon problem. That is because radon is found in pockets. But sometimes entire neighborhoods can be affected.
The concentration of radon in the air is measured in units of picocuries per liter (pCi/L). A picocurie is one trillionth of a curie, a measurement of radioactive material. The US Environmental Protection Agency (EPA) recommends that action be taken to reduce radon levels if the concentration reaches 4 pCi/L. Breathing in radon levels of 4 pCi/L raises the risk of lung cancer equivalent to smoking five cigarettes per day. The concentration of 4 pCi/L has been established by the EPA as the radon action level. Nearly one out of every 15 homes (some 6 million) in the United States has radon levels above the EPA action level. In addition, about one in five schools in the United States has at least one classroom (more than 73,000 in all) with radon levels above the EPA action level.
Sources of Radon
Radon is found in all 50 states with Colorado having among the highest radon levels in the country. The most common source of indoor radon is uranium in the soil or rock on which homes and other buildings are built.
Any home or building may have a radon problem. This means new and old ones, well-sealed and drafty ones, and homes or buildings with or without basements. Radon travels through soil and enters the indoor environments of buildings through cracks and other openings in the foundation. This is especially true in homes if there is not enough ventilation and the home is under negative pressure.
Radon gas enters residences and buildings through:
Cracks in concrete walls and floors
Floor drains, and sumps
Utility pipes or wires that penetrate a foundation wall
Well water - Only one percent to two percet of indoor radon in the air comes from drinking water. But locations where radon from water can be released into the air include:
Building materials such as natural stone or rock; however, building materials rarely cause radon problems by themselves.
High levels of radon in the outside air
Once inside, radon can travel throughout the home through unsealed furnace ducts and distributed throughout the house by the ductwork and registers. Harmful levels of radon can accumulate in confined air spaces, such as basements and crawl spaces. Radon levels are usually highest in these areas because they are nearest to the source and are usually poorly ventilated.
Health Problems Caused By Radon
After radon enters a residence or building, it continues to decay into other radioactive elements. These can easily become attached to other solid objects (such as dust or smoke) that can be inhaled into a person's lungs. When these particles continue to break down inside the lungs, they release small bursts of radiation. This radiation can damage lung tissue and lead to lung cancer later in life. According to the EPA, about 7,000 to 30,000 lung cancer deaths from radon occur each year.
An individual's risk of getting lung cancer from radon depends mainly on three factors: the level of radon, duration of exposure, and smoking habits.
The concentration and amount of radon. Some homes or buildings may have high concentrations of radon and others may have none. Based on a national residential radon survey completed in 1991, the average indoor radon level is 1.3 pCi/L. The average outdoor level is about 0.4 pCi/L. Action to eliminate radon should begin if concentrations are 4 pCi/L.
Length of exposure to radon. The longer the exposure, the higher the risk.
Exposure to radon and environemntal tobacco smoke. The EPA estimates that the increased risk of lung cancer for smokers from radon exposure is ten to twenty times higher than for people who have never smoked.
There are no acute or immediate health problems caused by radon. There is only one health effect associated with radon (lung cancer) and that might not show up for many years.
Decreasing Exposure to Radon
Testing to see if radon is present. One of the environmental objectives of the US government was to persuade 40 percent of people to conduct radon testing in their residences by the year 2000 (50 percent where there is a smoker, former smoker or a child.) However, during a 1990 survey by the National Center for Health Statistics, they found that only three percent to five percent of residences had been tested for radon even though 69 percent of those surveyed had heard of radon.1 Even though Wyandotte County, Kansas got 500 radon testers to give away free, they had problem getting rid of them since most people around there did not know what radon was.2
Since there are no physical properties to indicate that radon is present (like an odor) and since health effects may not occur for many years, you will not know if radon is in your residence unless you test it. The EPA recommends testing all residences below the third floor. But even if you don't have radon in your residence or building now, keep in mind that there are factors that can change that. Examples include home renovations, changes in ventilation, earthquakes, and settling of the ground beneath a home or building. Testing should be done at least every two years as well as after significant changes or renovations to the building.
There are many kinds of inexpensive, do-it-yourself radon test kits that can be obtained through the mail, and in hardware stores and other retail outlets. Make sure you buy a test kit that has the phrase "Meets EPA Requirements" on it. The most commonly used devices are charcoal canisters, electret ion detectors, alpha track detectors, and continuous monitors placed by contractors.
Different test periods: Test periods can be weeklong, 90-day, and yearlong. Because many factors can influence radon levels in indoor air, a yearlong measurement is the preferred length since it gives more accurate results. But if you can only test for a short amount of time, do the testing during the winter months because all the windows and doors are closed, but do not do it during unusually severe storms or periods of unusually high winds. Alpha track detectors and electret ion detectors are the most common long-term testing devices.
The test canister should be put in the lowest level of the home that you use. Put it in the basement if you use your basement. It should not be put in rooms that are high in moisture or that are drafty, such as kitchens, bathrooms, laundry rooms, or hallways. High humidity and drafty conditions can affect the results. Also, do not bother the devices while they are sampling. Experts recommend using two test kits as a way of determining if your test is accurate. If you find one canister has significantly higher levels than the other, you know that the test is inaccurate and inconclusive and has to be redone.
If you prefer, or if you are buying or selling a home, you can hire a trained contractor to do the testing for you. The contractor must have been evaluated by the EPA's voluntary National Radon Proficiency Program (RPP). A contractor who has met the EPA's requirements will have an EPA-generated RPP identification card. Ask to see this card before deciding on a contractor.
Steps to Reduce Exposure to Radon
Test your home for radon. Fix your home if your radon level is 4 pCi/L or higher. Radon levels less than 4 pCi/L still pose a risk, and in many cases may be reduced.
Increase ventilation. Opening a window can help dramatically. The radon level is lower when the inside air is allowed to escape and fresh air can enter the home or building.
When to hire a special contractor. There is usually no need to hire a special contractor to install radon-resistant features since many items can be easily and inexpensively installed with common building practices and materials. Also, many builders already incorporate some of these items when they build homes to control moisture or increase energy efficiency. If you do hire a contractor to fix your radon problem, make sure they have a card indicating that they have passed the EPA's Radon Contractor Proficiency test.
Steps to Reduce Radon Levels3
Here are some steps usually taken to reduce radon levels in homes and buildings:
A gas permeable layer (A) is placed beneath the slab or flooring system to allow the soil gas to move freely underneath the house. In many cases, the material used is a four-inch layer of clean gravel.
Plastic sheeting (B) is placed on top of the gas permeable layer and under the slab to help prevent the soil gas from entering the home. In crawlspaces, the sheeting is placed over the crawlspace floor. Polyethylene sheets serve as a good barrier to radon emission.
Cracks and other openings in basement floor are sealed (C). Settling cracks occur in foundation walls and in concrete floors. These cracks can be filled with cement grout if they are large enough; small cracks can be filled with high quality caulking compounds suitable for concrete. Painting basement floors and wall surfaces also helps. Epoxy paints are the most effective in reducing radon emission. Typically, two or more coats of paint, or paint used with a sealant compound, are needed to seal the pores adequately. Covering walls with gypsum, plaster or wallpaper does not reduce radon emission. However, sole reliance on sealing cracks in basement walls and floors is usually not an effective radon remedy, especially in a finished basement where many cracks will probably be overlooked.
A three- or four-inch gas-tight or PVC pipe (D) (commonly used for plumbing) runs from the gas permeable layer through the house to the roof to safely vent radon and other soil gases above the house. This method of radon removal is effective because it addresses the pollutant at its source - the soil beneath the basement floor. Radon is removed from the soil and sent outside, before it has a chance to enter the house. In this system, a plastic pipe is installed through a concrete floor to the gravel beneath the slab. The pipe extends to the attic of the house and through the roof.
An electrical junction box (E) is installed in case an electric venting fan is needed later. A special fan (called an in-line fan) draws radon gas out of the soil from beneath the house and pulls it upward through the pipe. The pipe then exhausts the radon gas to the outside, where it is diluted with outdoor air.
Conduct follow-up radon testing to make sure that the measures worked to reduce radon levels. There was one case that a chance inspection showed that the system that had been installed to reduce radon levels didn't work. Radon was being sucked into the heating system and deposited in every room in the house with high levels in some cases.4
Radon in water from lakes, rivers, and reservoirs is not a problem since most of the radon is released before it enters the distribution system. Also, public water systems that serve 25 or more year-round residents must send an annual water quality report, which is supposed to mention if levels of radon have been tested.
However, radon can be a problem if you get your water from a well. If you have tested the air in your home and found a radon problem, and you have a well, contact a lab that is certified to measure radiation in water to have your water tested. Radon problems in water can be readily fixed. Radon-contaminated well water is usually treated by aerating or filtering the water through granulate-activated charcoal (GAC). Aeration (bubbling air through water) is done to strip radon from it. An exhaust fan then vents the radon outside. Though GAC filters may cost less, the radioactivity that collects on the filter is a hazard and has to be disposed of in a special manner.
If you want more information on radon, contact your state radon office, or call 800-SOS-RADON.
Eheman CR, Garbe P. Knowledge about indoor radon in the United States: 1990 National Health Interview Survey. Archives of Environmental Health. 1996;51(3):245-7.
Couret C. Radon: The phantom menace. American City and County. 2000 Jan:35-42.
Environmental Protection Agency. Radon Resistant New Construction. Date accessed October 2000: www.epa.gov/iaq/construc.html.
Chatman AD. Ways to test for deadly radon and how you can get rid of it. The Plain Dealer. February 5, 2000.