During the winter of 2015, we conducted a 90-day radon test in the basement of our house. Results came back as a shock.
Our test revealed that our house has 2260 bequerals per cubic metre (Bq/m3) radon. This means that in a cubic metre of household air, 2260 radon nuclei were decaying every second. The Government of Canada says that 200 Bq/m3) is the maximum safe limit for Canadian houses. The World Health Organization has put safe levels at 100 Bq/m3.
I did a second 90-day test and the results were almost the same at 2320Bq/m3. This testing was done during the winter heating season when radon levels would be at the highest.
When I built our house 20 years ago,as a geologist, I knew that here was a radioactive boulder in the yard. It never occurred to me (or anyone else) that that might mean there’d be radon in the soils. Twenty years ago, no one was thinking about radon. Building codes are different today with radon vent piping being mandatory in new house construction.
Radon is a colourless, odorless gas, a radioactive byproduct of radium. It is part of the natural radioactive decay series starting with uranium-238. It is radioactive with a half-life of 3.8 days, decaying by the emission of alpha particles within about an hour to polonium, bismuth, and lead in successive steps.
These atoms float around in the air during their few minutes of existence, often becoming attached to dust particles. These particles, sometimes being electrically charged, can stick to the surfaces of our bronchial tubes. This puts them right where they can do the most harm, for the cells lining our bronchial tubes are among the cells of our body most sensitive to radiation-induced cancer. The large release of energy into a single cell is what can damage DNA and initiate cancerous growth.
Radon is believed to be an important cause of lung cancer. Only cigarette smoking causes more lung cancer deaths per year. The onset of lung cancer takes five to 25 years, or even longer. Being a smoker compounds the problem by providing more dust particles for radioactive atoms to stick to.
Once one receives such news, you really have no choice but to mitigate the situation. No one will buy your house and you won’t want to bequeath it to loved ones, as is. This news came during a period of unemployment, so I had time to deal with the problem. However, I did not think that it would take three years!
My first step was to contact Radon West in Calgary (www.radonwest.com). They are the “go-to” people in western Canada for radon mitigation. They gave me many hours of their time in phone calls and emails and I bought a DIY kit from them ($600) as well as a digital radon tester ($150) that gives a reading within two days. The digital tester confirmed the 90 day test results within five per cent.
I am confident that the digital tester (Safety Siren Pro Series#3) was giving accurate measurements.
By this time the winter heating season was over. We live in a three-storey house with full basement. This makes for an excellent radon trap because of the thermal siphon effect in the winter, especially if an upstairs window is open. The wood stove in the basement also compounds the problem and helps create a negative air pressure in the house relative to the pressures under the basement slab during heating season.
The first step was to seal all basement floor cracks with elastomeric caulking compound. The next step was to install a radon fan under the basement stairs and run a four-inch ABS vent pipe up through an existing laundry chute, through the attic and out the roof. Then four suction points were drilled in the slab into the four area defined by interior footings. These were dug out under the slab and sealed air tight. At this point, the folks from Radon West visited our house and spent half a day (gratis) to analyze the situation. Small holes were drilled in the slab corners and pressures were read using a micro manometer. Sub slab pressures were slightly negative in two corners and slightly positive in two corners. Conclusion was that we had tight soils under the slab.
At the start of the next heating season, the radon readings were consistently about 1300 Bq/m3, or almost half what we had pre suction points. Next, I spent the rest of the winter cutting the gyproc out from the basement walls (finished basement), rolling up the insulation and sealing the cold joint where floor slab meets concrete wall. Once this was done, the sub slab pressures were still slightly positive in places but the overall readings dropped to about 750 Bq/m3.
The next summer, I was contemplating drilling holes under the house from outside to vent soil gasses but Radon West came up with a better idea. To spread the suction around under the slab, I then drilled 20 six-inch holes in the slab about four feet apart and then tunnelled between them and connected the tunnels to the existing suction points. This took about two to three hours per hole digging by hand using a screw driver and crowbar to carve tunnels in the compacted soils. Holes were then sealed by using plywood suspended under the slab and by filling in with concrete.
In addition, we also stopped leaving upstairs windows open during heating season and installed timers on the bathroom fans. Now, in the middle of the last heating season, radon numbers were 32 to 48 Bq/m3 (fluctuating with outside air pressure). For comparison, readings I was getting outside the house were about 20 to 30 Bq.m3.
I feel good now that there is no longer an invisible enemy in our house, but I feel very concerned that we raised three kids in our house with many hours of playing Lego or watching TV in the basement, and that their health could be compromised as a result. I console myself by thinking that there are 2.5 x 10^ 22 molecules in a cubic meter of air (sextillions!) and only 2320 of them per second were radon nuclei going through their half-life. Also, no one in our family smokes.
Still though, radon induced lung damage is based on probability and the higher the concentrations then higher the probability. But, one could be walking in a park and just happen to breathe in a radon atom or its progeny as it gives off a burst of alpha radiation and get DNA damage. There are no guarantees in life. I hope and pray daily that no family member comes down with lung cancer as a result of radon in our house. I also wonder about all the other families out there, who are unwittingly breathing in high radon concentrations every Canadian heating season.
Glen Rodgers can be contacted at email@example.com