Recently monitored my basement for radon levels, discovering it was approaching 200 Bq/m3. That’s at the edge of recommended corrective action, according to Health Canada.
Canada has significant uranium deposits across the country, and radon is frequently cited as something to be aware of. And we’re big fans of basements, exacerbating the issue.
As a bit of background, radon is a noble gas that is a decay product of uranium (through a long and complex decay chain with many other elements in between). Once the decay chain makes it to radon, it can permeate through rocks and soil where it finds its way into our homes, usually via the basement.
Amazingly radon only has a half-life of 3.8 days, then decaying to polonium-218 and then lead-214, then to a more stable lead-210 (still radioactive, but with a half-life in the decades). The transition from radon to lead-210 happens in just a couple of hours, but in between there are radioactive solid particles that attach to dust and the like and can be breathed in. Those particles throw off DNA-damaging alpha-radiation when they decay, so they’re best avoided where possible.
Alpha particles only travel a few cm, and can be blocked by something as simple as paper. They can’t even make it through skin. But if you breathe in those transition elements and it then decays internally, the alpha particles can cause DNA mutations in the lungs that could lead to cancer. For the same reason you don’t want to eat sources of alpha particles.
Anyway, being just under the remediation limit wasn’t comforting, so I researched things I could do quickly. One easy recommendation was to seal off the sump pump, if one is in place. And indeed there is the classic Canadian home sump-pump in this basement, with a pit with an installed pump to ensure that groundwater doesn’t rise too much around the base of the home. It is the one area of the foundation where there isn’t a thick cement layer blocking gases from getting in.
Sealing it off was nothing more than some plastic wrap taped to the discharge pipe and then tented securely around the base, preventing the circulation of air around the sump pump from mixing with the general basement air. There are a number of third party plastic covers that achieve the same goal.
Almost immediately the radon level dropped to below 50 Bq/m3. Over time an imperceptibly thin layer of Pb-210 will cover the inside of this enclosure as the radon is forced to complete its decay chain in this plastic prison, throwing off a minute number of alpha particles that fall harmlessly off in a remote corner of the basement.