Health officials say sensors in B.C. have now detected “minute” levels of radiation coming here from Japan’s leaking nuclear reactors.
But they continue to assure the public there is no cause for residents here to worry because of the dispersal of radioactive particles across thousands of kilometres of ocean.
“These amounts are negligible and do not pose a health risk to British Columbians,” the B.C. Centre for Disease Control said in an update posted Monday.
“We are expecting very slight increases in radiation until a week after the reactors are stabilized,” it said. “These are not cause for concern, and are smaller than the normal day-to-day fluctuations typically seen in B.C.”
BCCDC officials say the radiation levels arriving from Japan are tiny compared to other natural sources of exposure for B.C. residents, including rocks and soil, ultraviolet radiation from the sun and cosmic radiation from space.
Levels so far detected are at 0.0005 microsieverts per day, according to data from Health Canada’s Radiation Protection Bureau and released by the BCCDC.
By comparison, a dental x-ray is about 10 microsieverts – or 20,000 times as much.
Passengers on a cross-country airline flight can be exposed to 30 microsieverts or 60,000 times as much.
And a CT scan can expose a person to between 5,000 and 30,000 microsieverts – more than 10 million times as much as the increased daily exposure in B.C. from the Japanese radiation plume.
In other words, it would take more than 27,000 years of exposure at the current slightly elevated levels of radiation from Japan in B.C. to equal the exposure from a single CT scan.
“It’s minute, to the point of insignificant,” said a Health Canada official.
Canadians on average are exposed to 5.5 to 8.2 microsieverts per day, or 2,000 to 3,000 per year, from all sources, most of which are natural.
Before the nuclear crisis, baseline radiation readings at stations in Vancouver, Victoria and Sidney were well below the national average, ranging from 0.22 to 0.44 microsieverts per day.
Health Canada is also adding nine more radiation monitoring stations in B.C., in addition to six units already in place along the coast.
Residents are urged not to take or stockpile potassium iodide, which should be taken only when recommended by doctors and can otherwise cause side effects.
The Japanese nuclear disaster at the Fukushima Daiichi nuclear plant has caused partial meltdowns at multiple reactors, releasing large amounts of radiation and triggering a massive evacuation of that region.
The crisis is currently rated as severe as the Three Mile Island disaster in the U.S. but still well short of the 1986 Chernobyl reactor fire that contaminated large areas of eastern Europe.