Radon is a radioactive noble gas that comes from the decay of radium in the soil. Radium is also a daughter or progeny nuclide of Uranium (Uranium decay). Radon is a colorless, odorless, invisible gas that can only be detected through the use of proper equipment and protocols. Chronic exposure to elevated radon levels has been linked to an increased incidence of lung cancer in underground miners.
Radon is constantly being generated by the radium in rocks, soil, water and materials derived from rocks and soils, such as certain building materials. Radium is a decay product of uranium which is naturally occurring in the soils and rocks of the earth’s crust. Uranium is present at about 0.5 to 5 parts per million (ppm) in common rocks and soils. The concentration of radon gas in the soil will be related to the amount of uranium present. However, this is not a good indicator of the level of radon in an individual home. The radon concentration in a home is dependant on the type of soil the home is built on. Cracks, openings and various penetrations in the building foundation will provide the pathway for the radon in the soil to enter the home. The ventilation rate and air flow patterns within a house are important factors that will affect how much radon will be pulled into different areas within the house.
Radon can also be dissolved in ground water and can be introduced into the indoor air through the aeration of well water during its use in washing machines, showers, etc. However in New York State, with a few exceptions, this component is usually relatively small compared to the amount of radon entering the home from the soil.
2. What are the health effects of radon?
The U.S. Environmental Protection Agency (EPA) has identified radon as the second leading cause of lung cancer in the United States. Many homes contain radon concentrations that are high enough to give their occupants lifetime exposures that could increase their risk of developing lung cancer. As one inhales, radon decay products in the inhaled air are deposited in the lungs. Radon and its decay products emit alpha and beta particles and gamma photons. The alpha particles are very damaging if emitted from radioactive material within the body. The alpha particles can strike sensitive lung tissue causing damage to the cells in the lungs subsequently increasing the risk of lung cancer. The risk associated with this exposure is thought to increase linearly with increasing radon concentration, so the higher the average radon level is in a house, and the longer the exposure period, the greater the risk to the occupants.
Radon concentration in air is measured in units of picoCuries per Liter (pCi/L) or Becquerels per cubic meter (Bq/m3). The picoCurie (pCi) is a unit of radioactivity which represents one trillionth of a Curie or 2.22 nuclear-transformations/minute. The Becquerel is one nuclear-transformation/second. The New York State Department of Health (NYS DOH) and the EPA use 4 pCi/L as a recommended action level. When testing indicates that the radon level in the lowest primary living area of the home is above this action level, the NYS DOH recommends that the homeowner take appropriate corrective action.
3. How can I find the radon levels in my home?
Radon tests are divided into short-term tests (less than 90 days, typically 2 to 7 days) and long-term tests, which is anything from 3 to 12 months.
The most commonly used device for making short-term radon measurements in homes is the charcoal canister. Usually this device is a small metal container, about the size and shape of a can of tuna fish, that contains activated charcoal. The radon in the air is adsorbed on the charcoal and the decay products can then be measured by a laboratory to determine the concentration of radon in the air. These devices are fairly quick, inexpensive, and easy to use, but their accuracy is only ± 20 percent. The NYS DOH recommends that the average of two charcoal canister measurements be used before making a decision to mitigate.
Another type of short-term test is the continuous electronic radon monitor. These devices generally produce more precise radon measurements, however they are more expensive and should only be used by certified professional radon testing firms. Continuous radon monitors are often used during real estate transactions, because they are more tamper resistant than charcoal canisters.
While short-term tests are useful for screening and for situations where results are needed quickly, a long-term test is a better indicator of the average radon level. Radon levels are known to be affected by the time of day, varying as the temperature changes during the day. They are also affected by the seasons, generally rising in the winter. Using a long-term testing device will provide a true annual average. One of the more common types of long-term detector is the Alpha Track detector or AT. Year-long measurements by AT detectors in living spaces provide adequate measurements for decision making.
Whether you choose to use short-term or long-term testing devices, be sure that the device is analyzed and the results reported to you by a NYS DOH Environmental Lab Approval Program (ELAP) certified lab. ELAP certification ensures that the results obtained from an individual or firm are accurate and reliable. Please contact ELAP, if you have any questions, at (518) 485-5570 or ELAP@health.ny.gov.
4. How can I reduce the radon levels in an existing house?
Radon levels in a house can be reduced. This can be done by several methods, but one of the most widely used methods is the active sub-slab depressurization system. This technique will reroute the radon gas from the soil away from the house, by venting the soil gas from beneath the basement to a point above the roof. This technique is very effective and will typically cost between $1000 and $1500 to install. The Radon Mitigation Standards contain useful mitigation information.
5. Radon reduction techniques for new construction.
If one is building in an area known to have a high probability of elevated radon levels, there are certain steps that can be taken during construction that will reduce the radon levels. If one is building in an area known to have a high probability of elevated radon levels, Radon Resistant New Construction techniques can be taken during construction that will reduce the radon levels.
The Building Radon Out (EPA: Radon Resistant New Construction) contains information on how to incorporate these techniques and materials in residential construction. Essentially this will consist of a layer of semipermeable material such as gravel under the foundation, a 6 mil or thicker layer of plastic between the gravel under the foundation and the concrete, a 3″ or 4″ PVC pipe through the foundation floor, a roughed in electrical box in the attic, and sealing and caulking of all openings in the concrete floor.
6. How often should I test my home?
A radon test should be done when buying a home, after doing major renovations, every two years if there is a mitigation system installed or every five (5) years otherwise.