Should Canadians be concerned about increased radon levels due to energy-efficiency measures that have tightly sealed our homes? A study published this week in the BMJ (formerly the British Medical Journal) cautioned that draft-proofing a house may trap the deadly gas inside, putting residents at increased risk for lung cancer.
Radon is a radioactive gas formed by the breakdown of uranium in soil, rock and groundwater. The odourless gas seeps into homes through cracks in the foundation, forming radioactive particles that can be breathed into the lungs.
In enclosed spaces, radon can accumulate in higher concentrations and become a health risk. According to Health Canada, radon exposure is the leading cause of lung cancer after smoking, accounting for 16 per cent of lung-cancer cases.
Radon dissipates in houses with air circulation from outdoors, but uncontrolled ventilation runs against the goal of utility companies offering incentives to Canadians to draft-proof their homes.
In the new report, researchers from Britain and Australia conducted a modelling study to determine whether the U.K. government's targets for reducing greenhouse-gas emissions in Britain's housing sector would affect radon exposure.
They found that a national rollout of energy-efficient measures would increase radon concentrations by 56 per cent, from a present-day mean of 21 becquerels per cubic metre to 33 becquerels per cubic metre. (A becquerel is the measuring unit of radioactive decay of radon atoms.)
Applied over a population of millions, the higher radon concentration in the study is still "a very small increase," said Dr. Sarah Henderson, a senior scientist in environmental health services at the BC Centre for Disease Control.
Nevertheless, any increase in radon exposure corresponds to an increased health risk, Henderson said. "The best approach to radon is to get it as low as practically possible," she said.
Canada's guideline for acceptable radon levels is 200 becquerels per cubic metre. This falls within the World Health Organization's recommendation that indoor radon exposure be limited to 100 becquerels per cubic metre, but not exceed 300 becquerels per cubic metre if the lower level cannot be achieved in country-specific conditions.
Radon levels may vary depending on soil conditions, how a house was constructed and air circulation within the home. On a given street, "what you'll see is one home with quite a high radon concentration and a neighbouring home with a lower radon concentration," Henderson said.
The only way to detect radon is to use a do-it-yourself test kit from a hardware store, or hire a radon specialist.
Levels can be reduced by sealing the foundation and, if concentrations remain high, installing a suction pipe in the basement floor to draw the gas away from the house. Health Canada estimates the average radon remediation process will cost between $1,500 and $3,000.
However, adding a suction pipe with a fan to vent the foundation may negate energy savings achieved by draft-proofing the home, noted the BMJ study.
Energy-conservation measures may affect air quality in other ways, said Dr. Michael Brauer, a professor in population and public health at the University of British Columbia. Tightly sealing a home may increase allergens such as dust mites, moisture that promotes mould growth and emissions from products such as candles, air fresheners, paints and nail polish. "All of these should be used with ventilation," he wrote in an e-mail.
Ideally, homeowners would test for air pollutants such as radon and carbon monoxide before draft-proofing their houses, Henderson said. "I don't think we want to discourage people from energy retrofitting their homes because of radon," she said.