4 W( o+ h: W) xRadon is produced naturally when uranium in soil breaks down. However, it's also the second leading cause of lung cancer in Canada and nearly half of Prairie homes have amounts exceeding Health Canada's safety guidelines. , G) B$ H9 ^! `' v4 ~; c1 J4 A4 O, b* U& y+ X% e5 w% J
出处: $ k7 t& ^. f \ @http://www.cbc.ca/news/canada/ca ... r-experts-1.2505835