This is a guest post from Dr. Rob Tarzwell. Dr. Tarzwell is a nuclear medicine specialist (in training) at UBC in Vancouver, and is on the Faculty of Medicine at the University of British Columbia. He is a CFI advisor.
Vancouver’s Georgia Straight, no stranger to willfully stupid incredulity on science matters, has once again achieved a single-punch self-knockout in its latest piece of gassy hysteria, “Japanʼs Fukushima catastrophe brings big radiation spikes to B.C.”
The piece’s author, as deeply misinformed as he is apparently concerned, informs his readership that:
Health Canada detected massive amounts of radioactive material from Fukushima in Canadian air in March and April at monitoring stations across the country.
Lions and tigers and bears, oh my!
Just how massive? Dear reader, I’m glad you asked. Straight journalist Alex Roslin informs us of the actual number, after being sure to wallow in histrionic froth with absolutely no sane context: 3.6 milliBecquerels per cubic metre of air. What does that mean?
One Becquerel is the disintegration of one radioactive nucleus per second. 3.6 *milli* Becquerels represents 0.0036 disintegrations per second, in a cubic metre of air. What does that mean?
Essentially, it means you need to inhale 278 cubic metres of air to internalize enough I-131 to achieve 1 Bq of internal activity (1/0.0036=278), or, 278,000 litres. Also, this means every litre of air contains about 3.6 atoms of I-131.
By comparison, in every litre of air, there are 2.69×10^22 molecules of gas. In long form, that is 26,900,000,000,000,000,000,000. Remember that iodine in gaseous form combines into I-I, so those 3.6 atoms are 1.8 molecules, and the percentage of I-131 is, therefore, 1.8/26,900,000,000,000,000,000,000. Do I really need to do the math for you?
Furthermore, the average human adult only breathes 8 litres of air per minute. It would take about 24 days of breathing at rest to consume enough I-131 (1 million atoms) to guarantee 1 Bq. But I-131 has a half-life of 8 days. So by the time you have inhaled 278,000 litres of I-131, it has decayed three times, and the total radioactivity is then only 0.125 Bq, or 1.25 disintegrations every *ten* seconds.
At a concentration of only 3.6 mBq (1 Bq in 278,000 litres), you literally *cannot* breathe enough air to ingest 1 Bq of I-131.
Even so, should you be worried? Your own body contains potassium-40, a radioactive form of potassium, and you experience approximately 266,000 disintegrations per minute.
So, The Straight is raising alarm bells over 0.0036 nuclear disintegrations per second, completely ignoring the constant internal radioactivity of 4,433 potassium-40 atoms disintegrating each second of your life. Oh! I totally forgot to mention radiation from cosmic rays, and radon gas, and medical x-rays, and bananas, and instant coffee, and dried fruit, and. . .
Step away from the iodine tablets, folks. You’ll be ok.
Photo from Flickr user gsbrown99 under a CC licence.
EDIT: Post updated August 11 to reflect calculation error identified below.