Radon Gas – A silent killer

11 June 2015

Radon has become a growing concern for home owners.

To fully understand the issue with Radon, you must know a little about where it comes from. Radon is a naturally occurring radioactive noble gas that is an indirect decay product of uranium, one of the most common radioactive elements.

Uranium is naturally found in a solid state in the ground and decays at a very slow rate with a half-life of approximately 4.5 billion years. This means that in 4.5 billion years, half of the uranium on the planet will have broken down into other products and, eventually, radon. The very slow decay rate means that radon gas will be an issue for generations to come. When the uranium naturally decays into radon, it goes from a solid state to an inert gas. As radon is an inert gas, it is not chemically bound to other materials. This allows radon to easily move through any porous materials such as soil and concrete. Even with a half-life of 3.8 days, radon gas has plenty of time to move through the soil using the path of least resistance. Since it is less resistive to move through an open space than soil, radon gas will readily infiltrate a basement or crawlspace.

The radon will decay further into other substances, termed Radon Decay Products (RDPs), which are also radioactive. During the decay process and the further decay of the RDPs, alpha radiation is released. Alpha radiation presents the greatest health risk associated with radon and can cause a great deal of damage to living tissue if released within close proximity.

The major risk to human health from these alpha particles is to a person’s lungs. During a normal day, everyone breathes in radon, but at low levels. However, people who inhale high levels of radon are at an increased health risk, which can have serious consequences. Radon gas is the second leading cause of lung cancer in North America, surpassed only by smoking. In the United States, 15,000 to 22,000 deaths each year are associated by radon-caused lung cancer. The majority of the health risks of radon come from inhaling the alpha-emitting RDPs. To prevent this, one must know if radon gas is elevated within a residence or work place.

Radon gas is invisible, tasteless, odourless, and it can slowly seep into buildings, meaning testing is required to identify its presence. In fact, every home has some level of radon, just like the air outside. The average level of radon in outdoor air is about 10 becquerels per cubic meter, or Bq/m3. A becquerel is the SI unit of radioactivity; this is the activity of a quantity of radioactive material in which one nucleus decays per second. When radon levels are elevated, the chance of developing lung cancer increases. Studies have shown lung cancer rates sharply increase when people are exposed to concentrations of 100 Bq/m3 or higher. If there is a lack of air movement, radon gas has the ability to accumulate within an enclosed space and can reach these elevated levels.

Indoor radon levels are affected by the amount of radon entering the building and the amount of dilution of the radon gas within the indoor air. This allows for a variance in radon levels within a home. Typically, basements have the highest level of radon gas because this is the initial area for the radon to enter a home. Pressure differentials throughout the home can cause the radon gas to infiltrate every floor. This is the dominant transport mechanism for radon flow throughout a dwelling. Since the dominant transport mechanism for radon flow is pressure differentials, homes that are next to each other can have very different radon levels depending on property geology and building construction. This makes a neighbour’s radon test results a poor indicator of your own radon risk. In fact, the radon level will fluctuate with the seasons, weather, and even the time of day. Unluckily for Canadians, the highest radon gas levels are typically seen in the winter months due to snow cover on the ground.

Winter conditions cause an increase in house hold radon because of the snow cover and frost. This stops the ground gases from freely flowing up through the topsoil by providing a water/ice/snow barrier. This increase in resistance is enough to cause the gas to then find the path of least resistance, which is most often the nearest basement.

There are test kits available at your local hardware store that are similar to basic test kits ordered through a licensed laboratory; however, without having a qualified person conducting the testing and interpreting the results, these kits are inaccurate and unreliable. Just as buying shingles and a ladder does not make you a roofer, purchasing a radon test kit does not mean your house is ready for testing. The radon test kit needs to be placed in an appropriate location determined by a professional and the test results need to be analysed properly.

There are three basic sampling methods that can be conducted: grab, short-term, and long-term sampling. Grab sampling is conducted over 30 minutes and is usually used to determine radon entry points once a radon problem has been identified. Short-term sampling, which is what is available from the hardware store, is conducted over a period between two and 90 days. This type of sampling is needed to determine if long-term sampling is required. Short-term sampling is to be conducted under closed conditions and requires care by the homeowner. During their assessment, the radon-measuring technician must inspect the entire home and instruct the homeowner on how the sampling will affect their daily routine. If short-term sampling has determined that there is elevated radon within the residence, then long-term sampling must be conducted to establish an effective radon reduction method. Long-term sampling is the only reportable level accepted by Health Canada to determine the need for mitigation. Long-term sampling takes from three (3) to 12 months and can be conducted under normal living conditions.

Health Canada recommends an action level of 200 Bq/m3. This means that radon measurements found above the action level require remediation techniques within the residence. Health Canada recommends immediate remediation if the levels are greater than 600 Bq/m3. For anything between the two limits, Health Canada recommends remediation efforts within two years. However, the longer you live with elevated levels of radon and RDPs in your house, the greater your chances of developing adverse health effects. The only way to know is to have your house tested.

Pario Engineering & Environmental Sciences is fully capable of conducting radon testing within a residential home. To learn more about your options please contact us at your convenience.

Brad Williams, P.Eng., QP, CMI, CMR, CRT