Radiation here, but at a minute level
While there is radiation from the nuclear disaster in Japan reaching B.C., it is not enough to cause concern according to experts.
Provincial health officer Dr. Perry Kendall has issued several statements stressing, “British Columbians do not need to worry about any health risks from radiation here at home as a result of the nuclear reactor releases in Japan.”
“We have been monitoring the situation very closely, and I have been in close, regular contact with our partners at the BC Centre for Disease Control, Health Canada and in the United States since the tragic earthquake and tsunami.”
“We expect to continue to see measurable evidence of this power plant-associated radioactivity in the air until about a week after the reactor in Japan has stabilized,” he said adding the radiation levels measured are within the normal range of background radiation, and are below what a person on a long-distance flight may be exposed to.
Simon Fraser University researchers found around 0.0005 milli-Sieverts (mSv) of ionizing radioactive iodine-131 in the Vancouver area, which is less than one billionth the amount shown to cause disease in the thyroid.
At the concentrations detected a person would have to drink 815,143 litres of rain water at one time to suffer harmful effects, they said.
Radiation, or energy transmitted in the form of waves or particles, is present throughout the natural environment. Ionizing radiation is both naturally occurring from cosmic rays, soil and rocks, and human caused from sources like X-rays and CT scans.
The amount of background radiation varies in B.C., higher at high elevation or near natural deposits in the earth, but the average annual dose is two to three milli-Sieverts (mSv).
A person is exposed to about 0.03 mSv during a cross-country airplane flight, 3 mSv during a mammogram or 5 to 30 mSv from a CT scan.
The annual limit for nuclear energy workers is 50 mSv per year and The lowest dose spread over a year, linked to increased cancer risk is 100 mSv.
Acute radiation effects may be noticed around 1,000 mSv (one Sievert), but the effects depend largely on how long the dose takes. Over 24 hours it would likely cause radiation sickness (tiredness, nausea), but wouldn’t if it was spread over weeks.
The radiation levels being measured are within the normal background range, but can be identified as coming from Japan by their unique isotope signatures.
According to “worst case” modeling by the Radiation Protection Branch of Health Canada, a catastrophic reactor failure in Japan would not send enough radiation to B.C. to be harmful.
While the iodine-131 being detected decays in a matter of days, officials are also watching out for cesium-137 which is harder to detect and can remain in the atmosphere for 30 years.
Kendall also still stresses that people should not be taking potassium iodide, which is unnecessary and can cause health problems.
For more information check www.nuclearsafety.gc.ca or the BC Centre for Disease Control at www.bccdc.ca.