Radon is a radioactive gas produced when uranium in rocks, soil and groundwater breaks down, and may enter the work environment. Radon gas is the leading cause of lung cancer among non-smokers and is responsible for approximately 16% of lung cancer deaths in Canada. The employment sector with the greatest number of workers exposed to radon are elementary and secondary schools. Radon can particularly
build up in poorly ventilated spaces.

Environmental radon concentrations vary depending on a number of factors including building characteristics, occupant lifestyle, and local geology and soil characteristics. Indoor radon is more prevalent in a number of regions, but no areas of the province are ‘radon free’.

Radon is colourless and odourless, so workers and their health and safety representatives should advocate for radon testing, which is the only way to know if radon levels are elevated and if remediation is required. Most schools in Ontario have not been tested for radon.