Invisible, tasteless, and radioactive, radon is a gas. It is created when radium, a byproduct of uranium's decay, disintegrates. In addition to emitting alpha particles, radon also generates a number of solid radioactive compounds known as radon daughters or ""progeny."" There are trace levels of radon gas and radon progeny in the air, water, and soil everywhere. In areas where the soil or rock is rich in uranium, there are particularly high radon levels. Radium in the ground, groundwater, and building materials release radon. It can contaminate interior air, accumulating in poorly ventilated spaces together with the byproducts of its breakdown. Constrained air spaces, such basements and crawl spaces, can build up dangerous levels of radon and its offspring. Inhaled with air, radon descendants settle in the lungs. The lung takes in alpha particles that are released by the radon offspring. The radiation dose that results raises the danger of lung cancer.
What affects does radon have on health?
The International Agency for Research on Cancer (IARC) has categorized radon as a Group 1 human carcinogen. Lung cancer risk is increased by radon progeny inhalation. Data from a study of lung cancer mortality among uranium miners and other workers exposed to extremely high levels of radon progeny served as the initial foundation for the association between the concentration of radon progeny in the air and the risk of lung cancer. Compared to radon exposure alone, smoking and exposure to radon together dramatically increase the risk of lung cancer.
What features do radon and uranium share?
The radioactive decay process that results in radon and its offspring is shown in the following diagram. Figure— radon and its offspring are produced from uranium The half-life of each radioactive isotope describes the pace at which that isotope decays. This is the amount of time needed for a radioactive substance's half of its atoms to break apart. The half-life of radon is 3.8 days. The alpha particle intensity from a given sample of radon will decline by half in 3.8 days without its parent radium, to half the remaining amount (i.e., one-quarter of the original) in another 3.8 days, to an eighth in still another 3.8 days, and so on. This, however, does not occur indoors since fresh radon is continuously released from the decomposing radium contained in the ground and walls as old radon decomposes. The half-lives of radon progeny are extremely brief, ranging from a nanosecond to 27 minutes. As a result, radon progeny are only present in substantial amounts while radon is. In the event that all radon gas is eliminated, the radioactivity of radon offspring will swiftly degrade.
What are the radon level measurement units?
Picocuries per litre (pCi/L) or becquerels per cubic meter (Bq/m3) are the units used to measure the amount of radon in the air. One disintegration happens every second at a rate of one Bq. 37 Bq/m3 is equal to one pCi/L. Working level (WL), a measurement of the potential alpha particle energy per litre of air, is used to express the concentration of radon progeny. 200 pCi/L of radon in a normal indoor environment is equivalent to one WL of radon progeny. However, the relative levels of radon and its offspring can differ from one structure to another. In the most extreme scenario, 1 WL is equivalent to 100 pCi/L of radon. Full equilibrium is a highly improbable state that never occurs. Working level months (WLM) are used to measure occupational exposure to radon progeny, and one working level month is equal to 170 hours of exposure at an average concentration of 1 WL. Both of the aforementioned units can be used to report measurement data. The conversion table shown below may be helpful for comparing data from various sources: 37 Bq/m3 for 1 pCi/L. 0.1 WL = 800 Bq/m3 = 20 pCi/L 0.02 WL = 148 Bq/m3 = 4 pCi/L 1 m3 = 1000 L 0.01 WL = 74 Bq/m3 = 2 pCi/L More information on the units of ionizing radiation can be found in the publication Quantities and Units of Ionizing Radiation.
How can radon get into structures?
Typically, the main source of indoor radon is radium in the soil immediately beneath a building. Ground water and construction materials are less significant sources of radium. An key clue as to where radium and radon may be present is the presence of uranium in soil and rock. Due to the fact that radon is a gas, some of the radon created in the soil can enter a building. The remainder is buried beneath the ground. Radon progeny, which are solids and are present in the air of buildings as fine particles, are created when radon is exposed to air. The amount of radium in the soil and how easily the radon it creates may pass through soil and building walls, where it can then mix with the room air, determine the concentration of radon and radon progeny in the indoor air. Because radon is a gas, variations in atmospheric pressure also have an impact on how much of it accumulates in buildings and how much of it is released from the ground. The basement's walls and floor are made of concrete, which slows the radon's ascent into the building. However, radon can enter a structure through fractures in the floor, wall slab joints, and the drainage system. Radon levels indoors are usually always higher than those outdoors. Once within a structure, radon cannot easily elude detection. Buildings that are sealed in an effort to save energy are getting worse because less outside air is getting in. Due to their proximity to the source and typical lack of ventilation, cellars and basements typically have the greatest radon levels.
What are the radon exposure limits in homes?
There are numerous exposure limit sources to be aware of. Radiation exposure limits are established by the Canadian Nuclear Safety Commission (CNSC). The Nuclear Safety and Control Act defines a nuclear energy worker as ""a person who is required, in the course of the person's business or occupation in connection with a nuclear substance or nuclear facility, to perform duties in such circumstances that there is a reasonable probability that the person may receive a dose of radiation that is greater than the prescribed limit."" This section provides two types of exposure limits: one for occupationally exposed persons. The effective dosage (during the course of a year of dosimetry) for the yearly occupational exposure limit is 50 mSv (milli-Sievert). Effective dose of 1 mSv is the annual exposure cap for the general public. The Radiation Protection Regulations (SOR/2000-203, Section 13(1)) contain these values. In several occupational health and safety jurisdictions, values for workers (generally) or for workers in a particular industry have been adopted (e.g., underground mines, mines and mining plants). These numbers are listed in the Radon summary sheet from Carex Canada. You can also contact your local occupational health and safety jurisdiction to determine what values may apply in your situation. The threshold limit value (TLV®), or occupational exposure limit, established by the American Conference of Governmental Industrial Hygienists (ACGIH®) is 4 working level months (WLM/year) (2017). Although there is currently no regulation that governs an acceptable level of radon in Canadian homes, Health Canada, in partnership with the provinces and territories, has developed a guideline. Acceptable levels of radon in """"dwellings"""" which includes homes or public buildings (schools, hospitals, long term care facilities and correctional facilities) is 200 Becquerels per cubic metre (200 B/m3) based on the Government of Canada Radon Guideline.
What do we know about indoor radon levels?
A 2012 Cross-Canada survey, conducted by Health Canada's National Radon Program, found that no areas of Canada are """"radon free."""" One of the main purposes of the study was to estimate the number of Canadians living in homes with radon gas levels above the guideline of 200 Bq/m3, which identified about 7% of the population living in this situation. The results of the survey are not meant to be used to determine radon risk potential. The only way to know for sure if your home or workplace has levels of radon higher than the guidelines is to conduct testing in each home or workplace of concern.
How are radon levels detected?
Indoor radon level is measured by air sampling and by alpha dosimetry using radon track etch dosimeters. A number of companies manufacture and sell measuring instruments. Since radon levels vary greatly from day to day, Health Canada recommends long-term sampling (at least 3 months) to get a more accurate reading. Testing can be done by professionals or by using testing kits that can be purchased over the internet or from some home improvement stores. Be sure to follow the testing kit's instructions carefully to get accurate values.
What can I do to reduce indoor radon levels?
In many cases, a method called sub-slab depressurization is used. A pipe is installed through the basement sub-flooring that leads to an outside wall or to the roof. A small fan draws the radon from below the house and exhausts the radon before it can enter the home. Other methods include to increase ventilation, or to seal major entry routes into the home. Effectiveness of each method will depend on how high the radon levels are, and the characteristics of each home. Health Canada refers to the Canadian National Radon Proficiency Program (C-NRPP) for a list of certified service providers who can help reduce the level of radon in your home."""