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Radiochemistry Unit - Interpreting Your Test Results Table of Contents | Ordering | Collection Kits | Price Schedule | Analysis | Test Interpretation | Radon Information | Health Information | Decay Chains | Research | DNR Quarterly Reports | Useful Links This information is geared for the private well/home owner. The Safe Drinking Water Act (SDWA) regulations that govern radioactivity in drinking water do not apply to the individual well/home owner. Public water suppliers should contact the Wisconsin Department of Natural Resources for information regarding SDWA regulations contact.
WHAT DO YOUR RADON AIR TEST RESULTS MEAN? If your radon level is below 4 pCi/L, you do not need to take action. You may want to test again sometime in the future if your living patterns change or if a lower level becomes occupied, then test in that level. If your radon level is 4 pCi/L or greater, use the following charts to determine what your test results mean. Depending upon the type of test you took, you should either test again or fix your home. CHART 1: Radon Tests Conducted Outside a Real Estate Transaction
*A long-term test is defined as a test lasting more than 90 days. CHART 2: Radon Tests Conducted During a Real Estate Transaction (Buying or Selling a Home)
*Use two passive (simultaneous) short-term tests and average the results. **A long-term test is defined as a test lasting more than 90 days. WHAT SHOULD I DO NEXT? If the radon level is 4.0 pCi/L or greater, you can call the Wisconsin Division of Public Health's Radon Information Center (RIC) nearest you by dialing toll-free 1-888-569-7236. Individuals at the RIC can give you more information, including a list of EPA approved radon contractors who can fix, or help you develop a plan for fixing, the radon problem. You may also call the Radon Fix-It Line at 1-800-644-6999 between 11 AM and 7 PM Monday through Friday, for information and assistance. This is a toll-free number operated by the Consumer Federation of America, a nonprofit consumer organization. HOW SOON TO FIX YOUR HOUSE If results in significantly occupied levels of your house are confirmed to be higher than 4 pCi/L, you should take action to fix your house as soon as possible. In the range of 4 to 20 pCi/L you can take a year to get the work done. For confirmed results above 20 pCi/L, mitigation action should be more prompt. No level of Radon is considered absolutely safe. The average Radon level in the lowest lived-in floors in homes in Wisconsin is about 1.8 pCi/L. In most cases you can reduce the average Radon level in living spaces of your home to below 2 pCi/L. The outdoor air average of about 0.5 pCi/L is the lowest achievable level. FIXING A RADON PROBLEM While in some cases you can treat the problem yourself, you should always consider the use of trained Radon reduction personnel who have passed a test and been listed by a Radon Proficiency Program. Such radon mitigation contractors working in Wisconsin are on a Radon Mitigation Contractor Proficiency list for the state. To get a copy of this list, call one of the Wisconsin Radon Information Centers, toll free 888-569-7236 (888 LOW-RADON). Soil Depressurization is usually highly effective. It involves continually withdrawing air from beneath the basement floor (or from beneath a sheet of 6-mil plastic placed over a crawl space dirt floor and adhered to the walls). This reduces the air pressure there, and then air in the basement (or crawl space) flows to the depressurized zone through small cracks that could not be sealed, instead of soil gases containing Radon flowing into the basement through those cracks. An eleven-minute videotape Radon Reduction: Sub-Slab Depressurization, made in 1997 by the University of Wisconsin-Extension, shows a system installed. It has been sent to all public libraries in Wisconsin. Most homes with elevated Radon levels can be fixed with soil depressurization for around $1,200 (between $800 and $2,000). Sealing: Radon is in the gases in the soil under basements at 300 to 1,000 pCi/L or more. However, experience has shown that sealing cracks and openings in basements will not often reduce indoor Radon levels by much. Sealing results in reduction of radon by more than half in only about a quarter of the houses in which it is tried, while soil depressurization works in almost all cases. Gaps and openings to soil through basement floors and walls should be sealed gas tight. The caulk type with the best adhesion to concrete is polyurethane, not silicone. Sealing might reduce radon levels if the areas of openings to soil add up to several square inches. It can be very inexpensive, so it is worth a try if there are major cracks and openings. For more information on reducing Radon, consult the Radon Information Centers and proficiency-listed radon mitigation contractors. If you have internet access, you can look on the U.S. EPA radon web page. Radon in Water drafted Feb. 20, 2004 , C. Weiffenbach, Wisconsin Division of Public Health There is currently no U.S. EPA standard for radon in drinking water although regulation is called for in the 1996 amendments to the Safe Drinking Water Act. A few years ago, a 4000 pCi/L standard for radon in community supplies was proposed by EPA for states that undertake a suitable program for control of radon in air (like Wisconsin), but that regulation was not finalized. For the latest update on possible regulation, please see www.epa.gov/iaq/radon/rnwater.html. In a few wells in the north of the state, waterborne radon occurs at sufficiently high concentrations that one might want to reduce it, even though there is no standard. In a survey of more than 500 private wells located in a grid covering Wisconsin , none south of a line from La Crosse to Green Bay had radon over 4,000 pCi/L, and above that line only 11 were over 4,000 pCi/L. However rare, in the north of the state there are many wells with radon at tens of thousands of pCi/L and a few with hundreds of thousands of pCi/L. The majority (90%) of the risk from radon in water is from inhaling the radon released to air from the water by household uses such as laundering and showering. A 279-page report by an expert committee, titled "Risk Assessment of Radon in Drinking Water" ( www.nap.edu ) was published in 1999 by the National Academy of Sciences. For every 10,000 pCi/L in a household water supply, a time average of about 1 pCi/L is added to the indoor air. Since indoor air often has much higher radon than that coming from the ground directly, and wells are seldom that high, well water is a minor concern compared to radon in indoor air. The risk to an individual from lifetime ingestion of water with 10,000 pCi/L is about seven in ten thousand chance of cancer to the digestive tract, (primarily stomach cancer). The much higher inhalation risk from radon in water depends on the house ventilation rate, volume, and number of residents. Devices for removing radon from well water for a single house are rather large, complex, and expensive, costing $3,000 to $5,000 for installation and 10 years of operation. The low risks avoided with one may not be worth the cost to a homeowner unless the water has many times 10,000 pCi/L. Mitigation of the radon coming directly from the ground into indoor air is a much better value and produces a much greater risk reduction to the residents unless the radon in water is many times 10,000 pCi/L. For information about measuring and controlling radon in indoor air, please see www.lowradon.org , Radon Information for Wisconsin. Last Revised: February 06, 2004 RADON IN AIR If the indoor air exceeds 4 pCi/L, action should be taken to lower the radon as much as possible. This may include treatment of well water. For more information, contact the Radiation Protection Unit (1-888-569-7236), or you local Department of Natural Resources office. It is recommended that you contact one of these agencies before taking any corrective action for radon in water. This screening test measures the total alpha and beta radioactivity in the sample. The test does not give any information about which radioactive isotopes are in the sample. For instance, a water sample may contain radium 226, radium 228 and uranium. All of these isotopes or the progeny of these isotopes give off alpha and beta particles. This test adds up all of the alphas or betas regardless of the isotope that produced them. Generally, if a water sample has an elevated gross alpha value and does not have uranium in it, the gross alpha value is about three to six times higher than the radium 226 value. If a sample has an elevated gross alpha value and no radium 226 in it, the gross alpha value is approximately equal to the total uranium value. There are unique water supplies for which these general rules of thumb don't hold. These supplies may have other isotopes in them such as polonium 210, radium 224, or thorium. None of these isotopes are currently regulated in water, but this may change in the future. If your test result was less than the MDL (see definitions below), then you do not need take any action to treat your water if you are a private well owner. If your results were above the MDL and you would like help interpreting the results, please call the lab at 608-224-6227. These are two naturally occurring isotopes that are sometimes present in well water. Radium analyses are usually only performed if the gross alpha/beta screening test is elevated. It is not possible to have radium 226 in the water without having an elevated gross alpha value. The current standard for municipal wells is that the sum of the radium 226 and 228 activity must be less than 5pCi/L (units are picocurries per liter) to be in compliance with the Safe Drinking Water Act (SDWA). See MCL below in the definitions for additional information. If you are a private well owner and have an elevated radium level, please call the lab at 608-224-6227 for help interpreting the results. Elevated uranium levels are sometimes found in private wells, primarily in the north central part of the State. The uranium result is the sum of the activities for all of the isotopes of uranium found in the water sample and is therefore, reported as total uranium. The various isotopes of uranium are present on the Earth in specific ratios. However, these ratios may be altered in well waters due to a number of chemical and physical conditions that are present in the well. This condition is known as disequilibrium. The total uranium method as well as another technique called alpha spectroscopy accurately determine the uranium activity even if disequilibrium is present. More information on this topic The following is a list of terms found on reports issued by the Radiochemistry Unit.
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