Health Canada has proposed stronger standards for radon levels in indoor air to reduce the risk of health hazards such as lung cancer.

Radon is a colourless, odourless, radioactive gas that can accumulate in confined spaces such as basements and crawl spaces in homes.

In 2006, an estimated 1,900 lung cancer deaths in Canada were due to radon exposure, the department said.

Under proposed new rules posted on Health Canada's website, homeowners would need to take remedial measures when average annual radon concentration exceeds 200 becquerel per cubic metre, a quarter of the current limit. (A becquerel is a measure of radioactive decay.)

Higher radon concentrations would require faster action, which should reduce radon levels to a "value as low as practicable," the department said, noting the updated guidelines are based on new scientific information.

The guidelines would apply to residential homes, as well as public buildings such as schools, hospitals, long-term residences and correctional facilities. Uranium and other mines that are covered by other regulations are excluded.

It costs about $1,200 for a contractor to reduce radon levels in the average home, although it can range from $800 to $2,500, depending on how the home was built and the extent of the problem, according to the Health Canada's responses to frequently asked questions on the topic.

Health Canada is still reviewing targets for construction of new dwellings. Until August 9, it is accepting public comments on lowering the level to 100 becquerel per cubic metre for areas of new homes where people are likely to spend more than four hours.