People who live in areas with high levels of radon are at risk of lung cancer. Modern houses are built with radon barriers, at least where I live in Ireland, and older ones used to be draughty, which allowed radon gas to escape, but now with increased airtightness, radon levels can build up. In Ireland you can get levels of radon in your house tested and remedial work done if needed.
Struggling to support my 91 yr old mother
Are we growing accustomed to the heatwave?

