Above: Radon (Wikimedia Commons/Daniel Mayer or GreatPatton)

Radon is a radioactive gas as well as the second leading cause of lung cancer worldwide. As a result, radon exposure is a major public health concern. Although radon can be found virtually everywhere, and there are dangerous levels present in some Canadian homes, the risk is greatest in and around uranium mines.

Did you know?: Uranium miners have the highest rates of radon exposure, especially if they work underground in poorly-ventilated mines.In 2008, Nunatsiavut, the Inuit government in northern Labrador, implemented a moratorium on uranium mining while it studied the risks associated with radioactive mine waste. The value of uranium exploration in Newfoundland and Labrador promptly dropped from $58.1 million in 2008 to 3.2 million in 2010. In December 2011, the moratorium was lifted at the same time as Nunatsiavut passed mining legislation designed to protect both the environment and human health.

Radioactive atoms like radon and uranium are unstable. In a series of steps, called a radioactive decay series, they spontaneously decay by emitting alpha (α), beta (β), and gamma (γ) particles. The loss of these particles transforms the original atom. For example, uranium decays into various other elements, including radon, before ultimately becoming a stable lead atom. The entire process, which can take billions of years, is measured in half-lives. This refers to the time it takes for half of the atoms in a sample to radioactively decay into another element

Did you know? Uranium-238 a half-life of 4.5 billion years and decays to radium-226, which has a half-life of 1602 years. Radium-226 decays to radon-222, which has a half-life of 3.8 days.Exposure to radioactive chemicals can have negative effects on your health. The α and β particles are not normally the problem. They are relatively large and can only travel about a millimetre into the body before they collide with other molecules and come to a stop. However, α and β particles are released along with a great deal of energy.

When a person absorbs this energy, it ionizes atoms within their body, which means that the atoms lose or gain an electron. This ionization is called radiation and it can damage human cells. Exposure to γ rays is much more dangerous than exposure to α or β particles. The energy represented by the γ particle can cause the ionization of DNA and protein molecules, leading to radiation sickness and cancer. Nevertheless, similar effects can be caused by close exposure to high concentrations of α and β particles.

Uranium decays into radon on the fifth step of its radioactive decay series. All other atoms in the uranium radioactive decay series are in the solid phase. Radon, however, is in the gaseous phase. This makes it much more mobile and a much greater threat to human health. So aside from mining-related exposure, radon can also enter houses and other buildings through the soil. Many different kinds of rocks, including granite, contain uranium and can therefore release radon.

Did you know? The Canadian guideline for radon exposure is 200 becquerels per cubic meter (Bq/m3). The global average concentration of radon indoors is 39 Bq/m3, compared to an averaged outdoor air concentration of 10 Bq/m3.In fact, on average, 55% of a person’s annual exposure to radiation is from radon present in both indoor and outdoor air. Since air exchangers, fans, and clothes dryers generally cause air pressure within houses to be lower than in the surrounding soil, houses can act as vacuum for underground gases. As a result, radon can seep through any part of your home that is exposed to the soil.

Radon is found in virtually every house in Canada. However, radon concentrations vary greatly, depending on temperature, the geology in the area, and other factors. Radon concentrations can vary even from house to house on the same street! Health Canada recommends performing a three-month radon test in the lowest lived-in level of your house in order to determine your risk of radon exposure. This test would involve placing a radon detector in your house to measure the α, β and γ particles present in the air.

If the test determines that there are significant levels of radon in your home, there are a variety of ways to lower your exposure. The most common method is called Active Soil Depressurization (ASD). If the lower air pressure in your home is drawing in gas from the soil surrounding your basement, ASD can draw gas from below your home and push it directly out your roof using pipes and a duct fan.

It’s important to remember that you don’t have to be a uranium miner to be exposed to dangerous amounts of radiation. So make sure your family finds out whether there are significant levels of radon gas in your home and how to alleviate your risk.

References

General information

Company to explore for Labrador uranium (CBC News)
Cross-Canada Survey of Radon Concentrations in Homes. Year 1 Interim Report (Health Canada)
Labrador Inuit enact legislation to life moratorium on uranium mining (The Telegram)
Radon Frequently Asked Questions (Health Canada)

Scholarly publications and textbooks

Baird C, Cann M. 2012. Environmental Chemistry. WH Freeman, New York, NY. Robertson A, Allen J. Laney R, Curnow A. 2013. The Cellular and Molecular Carcinogenic Effects of Radon Exposure: A Review. International journal of molecular sciences.14:7.

Heidi Kavanagh

I am a master's student of Environmental Science at Memorial University of Newfoundland.

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