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Radon is a radioactive soil gas responsible for approximately 22,000 deaths per year in the USA. One of only 28 known human carcinogens, radon is colorless, odorless, and tasteless. It is the second-leading cause of lung cancer, responsible for more deaths annually than homicide, drunk driving, or AIDS. It is important to test for radon, because the effects of exposure may not show up for 5-25 years. There is no immediate indicator of what exposure is doing to your body.
Radon is a decay product of uranium, which is prevalent in granite in western NC. Pressure differences between the ground and buildings result in radon being sucked into the buildings, where it often gets trapped and accumulates. As radon decays, it leaves behind tiny particles of the heavy metals lead, bismuth, and polonium. When the polonium lodges in lung tissue, it emits alpha-particles, which can cause cells to mutate, leading to lung cancer. Obviously, higher radon concentrations, and longer exposure times, lead to greater risk.
Radon exposure is measured in pico-curies per liter (pCi/L). The EPA has established an “action level” of 4.0 pCi/L, which is commonly used in real-estate transactions. The EPA recommends that every home and workplace be tested, those at or above 4.0 pCi/L be mitigated (fixed), and that mitigation be seriously considered for those between 2.0 and 4.0. With normal exposure, a level of 4.0 pCi/L is equivalent to 200 chest X-rays per year and, according to one study, equates to a 22% increase in lung cancer risk.
At this time, lung cancer is the only proven health consequence of radon exposure.
WELL WATER
Radon is also present in well water in WNC, and research is on-going into links to stomach and colon cancer, but at this time there is no documented proof that bathing in or drinking water containing radon is harmful. However, high levels of radon in water can be released into the air through atomization during hot showers or use of dishwashers and washing machines. It is difficult to quantify the exposure effects of such a release, since very high doses can be released in a confined space (i.e. the bathroom) and may diffuse quickly throughout the house. At this time, the EPA has no “action level” for well water, but it is generally accepted that 10,000 pCi/L in well water contributes 1 pCi/L to the levels in the air in a home.
TESTING
There are several types of machines and devices used to test for radon gas and it’s by-products. Each has it’s pros and cons, but all give equally valid results when used properly. The two most common testing methods are passive charcoal devices, used by homeowners and professionals, and electronic monitors, used primarily by radon professionals and home inspectors. Charcoal devices, such as those from Air-Chek labs in Fletcher, are inexpensive, portable, and simple to use. They are quite reliable, affected only by extreme humidity or damage to the packaging. Electronic monitors are expensive, require annual calibration , and must be handled and stored carefully. They are great for diagnostic purposes, since they usually report hourly readings, and the better ones track changes in humidity, temperature and barometric pressure. Additionally, many electronic monitors have a “tilt” function which indicates if the monitor was moved during the test period.
Radon tests are classified as short-term and long-term. Short-term tests are typically 2-7 days in duration and should be as close to 24-hr. increments as possible, since radon levels in buildings typically fluctuate from night to day. Outside windows and doors must remain closed during the test period, except for normal entry and exit, and interior doors should be left open. For a test of less than 4 days, closed-house conditions must be maintained 12 hours prior to beginning the test. EPA protocols call for testing in the lowest area of the house likely to be used on a regular basis; finished or unfinished. If a short-term test shows moderately high radon levels, a long-term test is a good idea. Long-term tests are 91 days to a year in duration and give the most accurate picture of actual conditions in the house. They are usually done with a small passive device known as an alpha-track detector, and do not require closed-house conditions.
MITIGATION
Should testing indicate elevated levels, radon mitigation is required. While there are many lesser-used mitigation techniques, the most common are sub-slab de-pressurization, used for basements and slabs, and sub-membrane de-pressurization, used for crawl spaces. Both seek to reverse the pressure difference between the house and soil, and require a vent pipe and fan to create suction beneath the floor or beneath a vapor barrier. Vent pipes must vent above the roof, and fans cannot be in or under a living area. Typically, the vent will run up through a closet and through the roof, with the fan in the attic, or through a wall and up the outside of the house past the eaves, with the fan on the exterior. Fans run continuously, require no maintenance, and use very little energy. The effectiveness of a sub-slab system is determined mostly by the type of material under the slab; houses with no crushed stone under the floor may require additional work. Crawlspaces are more straightforward as far as results, but have many more variables that affect installation difficulty, such as existence and condition of vapor barrier, square footage, headroom, and obstructions.
FINDING A CONTRACTOR
Since radon is a serious health issue, it is a good idea to hire a certified expert for your testing and mitigation needs. Professional certification is granted by two organizations, AARST-NRPP, and the NRSB, and insures that the certified individual has been trained, passed a National proficiency exam, receives continuing education, and agrees to abide by a code of ethics, EPA Radon Mitigation Standards, and local building codes. A professional contractor should also carry radon-specific liability insurance, offer references and guarantees, and have other professional credentials, such as membership in the Better Business Bureau and American Association of Radon Scientists and Technologists.
As a consumer, please note that while most home inspectors offer radon testing, many are not certified. Additionally, very few companies currently offer liability insurance for radon professionals. Home inspector, contractor, and general liability policies usually do not cover radon-related work.
Henri Boyea, owner
RADON CONTROL PRODUCTS
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