Of the two risks Canada faces from radiation due to the earthquake and tsunami that hit Japan, one is under control — the risk of eating food from Japan contaminated by radiation from the crippled Fukushima nuclear power plant.

This is because Canada hasn't imported any Japanese food since the March 11 disaster. Also, Canada's food imports from Japan have always been rather small, about .03 per cent of our total food imports, which comes to about $42.6 million a year.

The big question today is what damage can radiation from Japan drifting across the Pacific Ocean to British Columbia do to our food, whether grown, hauled from the water or raised on the hoof?

The scientific answer is that it's too soon to know, that it will take most of a week to determine if there are dangers from any radiation unleashed at the Fukushima power plant.

"We clearly see from the data we have there is on the order of seven days between the releases of Fukushima and the radiation reaching us here," said Simon Fraser University scientist Kris Starosta, speaking on Tuesday of this week.

"We can monitor the situation in Japan and know ahead of time of any release, and we'll have our window to react and prepare for that."

Dangers of iodine-131, cesium-137

David Walter-Toews, professor of population medicine at the University of Guelph — he is also president of Veterinarians Without Borders — says the radiation risks from Fukushima appear in the form of iodine-131 and cesium-137.

Iodine-131 has been detected both near the Fukushima plant and in trace amounts on the west coast of North America, including B.C. It can be dangerous, especially for children, because it mimics iodine in the body and at dangerous levels can lead to thyroid cancer.

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Forester Andreas Thiermeyer checks the radioactivity level of wild boar meat with a Geiger counter near Munich, Germany. While Germans may worry about Sushi imported from Japan, some of the country's wild game and mushrooms pose a far greater radiation risk, showing the long-lasting effects of contamination from the Chornobyl nuclear accident. (Matthias Schrader/Associated Press)

The important thing about iodine-131 is that it has a half-life of eight days, which means it loses half its deadly load every eight days, which means in several weeks its threat reduces to a miniscule level.

Walter-Toews says a shipment of sweet potatoes from Japan showed up in Thailand after the accident and was destroyed. They didn't have to be destroyed, he said. They could have been stored in a shed for a few months, by which time the successive half-lives would have rendered any potential radiation danger negligible.

The radiation danger to be concerned about is cesium-137, which has a half-life of 30 years. Walter-Toews says so far there is no indication of even trace levels of cesium-137 this far from Japan.

He says those who monitor radiation dangers in Canada should zero in on plants such as spinach and mushrooms as "canaries in the mineshaft" as they would be the first to show signs of dangerous radiation.

Health risks in Canada?

Scientists say radiation levels in B.C. that can be linked to the Japanese reactor are "miniscule" and, so far, pose no health risk to the public. The miniscule radiation levels were detected by testing rainwater and seaweed in British Columbia.

On Wednesday, Health Canada and the Canadian Nuclear Safety Commission reported that the increase in environmental radiation measured in B.C. as a result of the situation in Japan is "very minute ... so small that it is extremely difficult to measure against normal background radiation."

Doses of radiation in Canada also vary depending on weather conditions and seasonal changes. The Canadian Nuclear Safety Commission said Wednesday that rain can raise the readings from two to four times and in northern stations such as Whitehorse we can expect gradual increases in radiation levels as the snow melts because the snow shields radiation in the ground.

A Health Canada document says Canadians routinely are exposed every day to what is called "background radiation," whether from rocks and soils, cosmic radiation from space, as well as medical or clinical devices such as X-ray machines and CT scanners. Some typical levels of exposure are:

  • A cross-country air flight exposes a person to 0,03 millisieverts (mSv) of radiation.
  • A CT scan can expose a person to between 5 and 30 millisieverts of radiation.
  • A chest X-ray can expose a person to 0.1 millisieverts of radiation.

Lessons of Chornobyl

Radiation can cause immediate health effects when exposure is high, greater than 1,000 millisieverts over a short period of time. This can cause skin redness and hair loss. Chronic exposure to radiation at lower doses over long periods of time can have long-term negative effects such as an increased risk of cancer.

Health Canada, based on information from its monitoring of the radiation from the nuclear incident in Japan, issued a release that says "… the amount of radiation reaching Canada is miniscule and does not pose a health risk to Canadians."

On Wednesday, the Japanese government announced it is considering spraying resin on the grounds of the Fukushima power plant. This would stick to the ground and form a film, trapping radiation and keeping it from reaching the Pacific Ocean or from being released into the air.

The technique used at the nuclear accident in Chornobyl in 1986 was to bury the nuclear reactors in tonnes of sand, then encase it in concrete at a cost of millions of dollars. Some 25 years later, the concrete at Chornobyl must be replaced, which is expected to cost about $1 billion.