Radioactive Basement

The bedrock under our neighbourhood contains small amounts of uranium. It’s an unstable chemical element that is subject to radioactive decay. The amounts are small and it wouldn’t be a problem but for the fact that one of the decay products is a gas at room temperature – a radioactive gas, radon. It seeps up through cracks in the rock and disperses into the atmosphere, unless it happens upon an enclosed space, such as a building, where it will accumulate. When radon decays it produces solid particles of radioactive polonium, bismuth and lead. These tend to cling to particles of dust and smoke in the air, and when you breathe these in, the heavy metals lodge in your lungs. There they decay, send out alpha radiation, and increase your risk of lung cancer. (The more smoke you breathe, the higher the radiation dose.)

The Swedish authorities recommend a highest level of radioactivity in indoors air of 200 Becquerels per cubic metre. My wife saw to it that during the winter we had two little particle collectors hanging from the ceiling for four months, with bits of sticky tape inside grabbing a sample of the ambient dust. When they were analysed, it turned out that the radioactivity in our winter air was 270 Bq/m3. This needs to be fixed.

The first thing to rule out was an unfortunate building material, blåbetong, “blue concrete”, which is a type of aerated autoclaved concrete. It was made from limestone and a carbon-rich slate and used up until about 1980, when it was realised that the slate contained enough uranium that the concrete blocks exude considerable amounts of radon. There’s no blue concrete in our house.

Then we called in a radon consultant. He came over with a fast measuring instrument that can give you a radon reading in ten minutes and proceeded to take four measurements.

Outdoors: 20 Bq/m3
Bedroom: 140 Bq/m3
Living room: 210 Bq/m3
Crawl space: 1570 Bq/m3

In the summers we open doors and windows a lot more, which explains why much of our house is currently below the recommended max radioactivity level. But our crawl space is not a healthy place to be, at eight times the max value. The radon collects down there and seeps up into the house. Luckily the problem is easily fixed: we just need to put a small fan in one of the crawl space’s air vents to suck the radon out of the enclosed space and into the atmosphere, and fresh air in. The municipality pays.

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Comments

  1. #1 Philip White
    May 29, 2010

    All granite exudes radon. I wouldn’t live on granite, near it, or have granite tiles in the bathroom. It’s the gizzards of the Earth, squeezed out like an old zit. There’s lots near here, on the Fleurieu Peninsula, South Australia. It’s been here since we were part of Antarctica, about 50-60 million years ago. It’s nice to look at but, especially when it’s got plenty of tourmaline in it.

  2. #2 Bob Carlson
    May 29, 2010

    Interesting. I gather that your Baltic Shield is a lot like North America’s Canadian Shield. If your home has forced air heating, I wonder if it would help to add an electrostatic air filter to the furnace.

  3. #3 NJ
    May 29, 2010

    or have granite tiles in the bathroom.

    And keep away from those toxic bananas! All that K40!

    Radiation-phobia is not unlike chemophobia. Not a sign of a well mind.

  4. #4 Art
    May 29, 2010

    Florida has a lot of radon. Another factor that has to be checked and managed in some areas. Mostly a matter of geology. Granite tiles are not much of a source. I doubt you could get a reading from them. No need to freak out.

  5. #5 stripey_cat
    May 29, 2010

    It’s a problem in parts of Cornwall, too: I remember a public awareness campaign when I was a teenager to get cellars tested. Luckily, good ventilation is an easy and cheap solution.

  6. #6 Sandgroper
    May 29, 2010

    Yes, ventilation is the key. A small exhaust fan can make a very big difference to the concentrations.

  7. #7 Jonathan Lubin
    May 30, 2010

    Radon is a problem in New England too. Again, all that granite. When we sold our house in Providence, we needed to get an attestation of a good Rn rating. Radon is mostly a problem if you’ve smoked, I think.

  8. #8 Martin R
    May 30, 2010

    A radon-filled basement in Providence, R.I., strikes me as a very Lovecraftian thing.

  9. #9 Sandgroper
    May 30, 2010

    Jonathon, a synergistic effect has been found between smoking and radon – it is not really known why, but it looks like it could be because the radioactive solid particles which are the decay products of radon attach themselves to the smoke particles which the smokers breathe in. So in areas with buildings which have high radon concentrations, smokers have been found to be more likely to develop lung cancer than either non-smokers in those areas, or smokers in areas which do not have high radon concentrations.

    Offhand, I can’t quote you the paper, but this finding has been published in the USA in the environmental risk literature.

  10. #10 phunctor
    May 30, 2010

    Just a pedantic quibble – radon is not a fission product. It’s a decay product.

  11. #11 Martin R
    May 30, 2010

    Oh, right, fission is when you hit the atom with something, and decay is when you just sit around and wait for it to fall apart. I’ll fix it, thanks.

  12. #12 Dr M
    June 2, 2010

    “fission is when you hit the atom with something, and decay is when you just sit around and wait for it to fall apart”

    Not quite (but close). Radioactive decay is when a nucleus (spontaneously) decays, turning into another nucleus. There are two types of radioactive decay: alpha decay and beta decay. In alpha decay, the nucleus decays by emitting an alpha particle (consisting of two protons and two neutrons, i.e. a Helium-4 nucleus), leaving behind a nucleus of the element with atomic number two less than the original nucleus. In beta decay, a neutron in the nucleus is turned into a proton and an electron is emitted, or a proton emits a positron and turns into a neutron. The result is a nucleus with the same number of nucleons, but with atomic number raised or lowered by one.

    Fission is when a nucleus splits into two fragments. This process can be stimulated, such as in a nuclear plant, where uranium nuclei are made to fission by the help of neutrons, but it does also occur spontaneously in some very heavy nuclei (for example some uranium isotopes: this is what starts the chain reaction of stimulated fission in nuclear power plants, or, for that matter, nuclear bombs).

    So … isn’t alpha decay just fission where one fragment is a helium nucleus? Strictly speaking, yes, but that’s not how we use the terminology. When we say fission, we mean fragments of approximately equal size.

  13. #13 Doug K
    June 2, 2010

    the municipality pays ?
    yer lucky.. we had to pay $1000 to mitigate the radon in our house when we sold. We’d tested the living area to be 1.8 pCi/L, under the recommended level of 4, but the inspector put a tester in the crawl space and found 8 pCi/L..

    I wonder why the Swedish measure is Becquerels per cubic metre, and the American one is pico Curies per Litre ?

  14. #14 Martin R
    June 3, 2010

    Thanks Doc M!

    Doug, when you have universal health insurance it makes good business sense for the collective to pay for those fans. You get an awful lot of them for the price of a single lung cancer case.

  15. #15 Brian Gaulke
    June 8, 2010

    Dr. M, there is an exception to the use of the term fission to refer to a process resulting in fragments of approximately equal size. That is the production of tritium in approximately 0.01% of fissions. See, for example:
    http://www.c-n-t-a.com/srs50_files/127albenesius.pdf
    or the Wikipedia article on tritium.

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