Indoor Air Quality
What is Radon?
Radon is an odorless, tasteless gas. It occurs from the natural radioactive decay of uranium in the soil. The radioactive decay products of radon are charged ions. They have a static charge that enables easy attachment to dust and smoke particles in the air. Radon is measured in units called picoCuries per liter (pCi/L). A picoCurie is a measure of actual radioactivity. Annual levels above 4 pCi/L are considered excessive, and some remedial action should be taken.
Radon comes from various sources. It can come from rock; granite, shale, phosphate, and pitchblende are four likely rock sources, but others also have some percentage of uranium naturally occurring in them. Radon moves easily through porous, permeable materials. It can come from well water, natural gas, and in rare cases, some building materials such as concrete which can contain and emit radon.
Elevated indoor concentrations of radon can be found in every state. Uranium is present in most of the soil in the world. However, some places are definitely “hot spots.” Risk is more diverse in other locations. There are not immediate symptoms that will alert you to the presence of radon. Testing is the only way to know if you and your family are at risk.
Risks Associated with Radon
Radon gas decays into radioactive particles that can get trapped in your lungs when you breathe. As they break down further, these particles release small bursts of energy which can damage lung tissue and lead to lung cancer. Not everyone exposed to elevated levels of radon will develop lung cancer. And the amount of time between exposure and the onset of the disease may be many years.
Your chances of getting lung cancer from radon depend mostly on:
- how much radon is in your home,
- the amount of time you spend in your home, and
- whether you are a smoker or have ever smoked.
EPA Recommendations for Testing
Testing can be done by the home owner or by a professional. The Environmental Protection Agency (EPA) recommends that you take the following steps in ensuring your safety against radon:
- Step 1 – Conduct a short-term test. If your returned results read 4 pCi/L or higher, take a second, follow-up test.
- Step 2 – The follow-up test should be taken immediately if your short-term test is 10 pCi/L or higher. If not, you may follow up with a second short or long-term test.
- Step 3 – If you followed up with a long-term test, fix your home if your reading result is 4 pCi/L or more. If you followed up with a short-term test, the higher the results, the more certain you can be that you should fix your home. It is recommended that you fix your home if the average between your two tests is 4 pCi/L or more.
For reliable information of radon testing and mitigation in Texas, you can contact Kay E. Soper, the Texas Radon Contact with the Texas Department of State Health Services, at (512) 834-6787 ext. 2428 or (800) 293-0753 ext. 2428. http://www.dshs.state.tx.us/radiation/radon.shtm
Additionally, the Environmental Protection Agency has a radon specialist and indoor air quality specialist in each of their regional offices who can provide answers. The Region 6 office in Dallas serves Texas. The phone number for the Region 6 EPA office is (214) 665-6444.
How Does Radon Enter Your Home?
Four conditions must be present to enable radon to enter your home. Two of these are geological; there must be uranium in the soil as a source material, and there must be permeable soil which allows radon to move through it to your basement or crawlspace.
The other two conditions are determined by the house and its construction. There must be pathways for radon to enter the basement, such as holes, cracks, plumbing penetrations, or sumps (found in every foundation), and there must be an air pressure difference between the basement or crawl space and the surrounding soil. If the air pressure is lower indoors than in the soil, air and gases in the soil will enter. All four conditions must be present to have radon. If you reduce any one, less radon will enter your home. The last two conditions, determined by the house and its construction, are the key ones for mitigation.
If you find that your home has high radon levels, there are ways to reduce the concentrations. Even very high levels can be reduced to acceptable levels. Most radon problems can be fixed by a do-it-yourselfer for less than $500. If you need the assistance of a professional, check with the Texas radon contacts, or contact the National Environmental Health Association for a list of certified individuals offering both radon measurements and mitigation services to the public. Contact NEHA’s National Radon Proficiency office at (800) 269-4174 for assistance.
Mitigation Strategies in Existing Homes
Mitigation strategies are based on the factors necessary to have elevated radon in the home. Each is based on preventing radon from entering the home.
You should try to seal entry points and reduce the pressure-driving forces moving radon into the home. For homes with basements, the most successful mitigation method has been to install an active soil depressurization system. Air is sucked from below the concrete slab in the basement. This lowers the pressure beneath the floor. Since air pressure is higher in the house, soil gas moves to the exhaust pipe rather than into the house. For homes with crawlspaces, ventilate the crawlspace or install sub-membrane depressurization. A membrane must be installed on the floor of a crawlspace which is earth and not concrete.
Seal all cracks and openings, and seal walls with waterproof paint, cement, or epoxy. Put water traps in floor drains to keep air from coming in through floor drains when the traps are dry.
There are several methods you can use to reduce pressure-driven air flow when attempting to control radon. Seal penetrations in the ceiling; weatherstrip the attic hatch; avoid recessed lights; provide an outside air supply to combustion appliances; ventilate with a balanced air-to-air heat exchanger; provide air-supply ports for exhaust-only ventilation; and ventilate the crawlspace. All of these suggestions are directly related to controlling air leakage in the house, because the faster the air leaks out of the house, the more it inducts radon by increasing negative pressure in the bottom of the house.
Prepared by Janie L. Harris, M.Ed., CRS, former Extension Housing and Environment Specialist, Texas A&M AgriLife Extension Service, Texas A&M System. 1999.
Last updated: 22 November, 2013
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