Lung cancer is most commonly associated with smoking, but there’s a lesser-known trigger that has experts concerned — radon.

Radon is a naturally occurring colourless, odourless, tasteless gas. It’s also responsible for 16 per cent of lung cancers, making it the disease’s second leading cause, according to the Canadian Cancer Society.

“Nobody knows about it, which is a problem,” says Sara McMillen, spokeswoman for the society.

Radon is present in uranium and is released when rock and soil break down. Outdoors, says McMillen, it’s not a problem because it simply dissipates. However indoors when homes are poorly ventilated and there may be cracks or points of entry in the foundation then radon can accumulate to high concentrations, which is dangerous.

“Our homes are generally built for winter, which means they’re very well sealed,” says McMillen.

The Canadian Cancer Society is raising awareness about radon in the hopes that people will get their homes tested — an inexpensive and simple process. A homeowner need only buy a testing kit ($20-$30), and set it up in their basement for a six-month period.

“We encourage people to do it during the fall and winter months, when windows tend to be closed,” says McMillen. Afterward, the kit gets sent away to a lab where radon levels are analyzed.

Five per cent of buildings tested in a 2011 Health Canada study demonstrated radon levels four times the amount considered safe.

Fixing homes that do test positive for high amounts of radon, says McMillen, might cost anywhere from $300-$1,500 depending on what’s necessary, she says. Fixes range from implementing a ventilation fan to sealing cracks in the foundation.

The Canadian Cancer Society also wants the provincial government to update building codes to ensure that new buildings are properly ventilated.