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The atomic rhubarb of Pembroke

April 3rd, 2009

Tritium-laced plants found near town’s glow-in-the-dark sign factory
MARTIN MITTELSTAEDT Environment Reporter, The Globe and Mail
Tuesday, September 28, 1999

Radioactive rhubarb has been found growing in Pembroke, Ont., near a factory that makes glow-in-the-dark signs from nuclear waste.

The rhubarb, apparently thriving downwind of the sign factory owned by SRB Technologies (Canada) Inc., contained about 1,000 times the radioactive tritium found either in rain water in Ottawa or in a rhubarb sample taken from a garden about 45 kilometres away.

“It was unusually large rhubarb, but I don’t think it was mutant or anything like that,” said Ole Hendrickson, a resident of the Ottawa Valley community who helped collect the samples.

The Atomic Energy Control Board, the country’s nuclear-safety agency, said the radioactivity from the rhubarb carries little risk, but Mr. Hendrickson said residents should not have any involuntary exposure to a potentially dangerous radioactive substance. He said regulators “should be targeting for zero level” of exposure to radioactive material.

There are no other known sources of tritium in Pembroke, such as atomic power stations or nuclear-weapon-manufacturing facilities, making fugitive emissions from the sign plant the only likely source. The company makes signs that are illuminated without electricity, such as airport runway markers and exit signs.

The tritium concentrations were about 19 to 75 times the average levels found in plants growing around Ontario’s three nuclear stations. The generating stations are far larger than the sign plant, which is in a small industrial building on the outskirts of Pembroke.

The AECB views the radioactive rhubarb as safe enough to be baked in pies or made into jam.

Sunni Locatelli, a board spokeswoman, said consuming the rhubarb would deliver a weak radioactive dose far lower than that from a chest X-ray or from living in a brick house, two other things that lead to small extra doses of radiation.

The emissions from the rhubarb are “well below the public dose limits,” she said.

The company said it is in compliance with all the conditions of its operating licence. “We meet the guidelines set by the Atomic Energy Control Board,” SRB executive Stephane Levesque said.

Mr. Hendrickson had the rhubarb sent to a laboratory at the University of Waterloo, which detected the high concentration.

The laboratory then refused to analyze a second plant sample — of an aspen leaf from a tree growing next to the sign factory — because of concern over the tritium levels in the rhubarb.

University officials were worried that if a worker accidentally broke a sample containing such a high level of tritium, its laboratory would be contaminated.

The Waterloo lab specializes in checking for minute traces of tritium in groundwater, which typically has radiation amounts about one-thousandth those of the Pembroke rhubarb. Staff were worried that an accident would irradiate instruments and undermine the accuracy of future test results.

A spill in the lab “might cause us a lot of grief,” said manager Robert Drimmie, adding that he did not refuse the second sample because of worries over the potential health risk.

Tritium is a radioactive form of hydrogen used mainly to make thermonuclear bombs. But it can also be used in glow-in-the-dark signs.

Tritium is produced as an unwanted byproduct of Canadian-designed nuclear reactors. SRB makes its signs using tritium from Ontario Power Generation Inc. and from tritium recycled from old glow-in-the-dark signs.

Canada has no standards for tritium contamination in food, Ms. Locatelli said, but regulators try to minimize exposure to all sources of human-caused radioactivity because it is a carcinogen and causes genetic damage.

There is no safe radiation dose, but the new federal regulatory standard for public exposure to human sources of radioactivity accepts as a safe risk nuclear contamination that causes 50 additional people in a population of one million to die of cancer.

The AECB says the sign plant is well within this safety standard.

SRB conducts its own testing for radiation in vegetation around the plant, but Mr. Levesque declined to divulge the results.

The rhubarb Mr. Hendrickson sent for analysis contained 2,000 becquerels per litre of tritium. A becquerel is a unit of radioactivity.

The Ontario drinking-water guideline for tritium is to allow no more than 7,000 Bq per litre. In the mid 1990s, a provincial advisory body recommended a more stringent safety standard of 100 Bq per litre, but the proposal was never adopted by the government

Tritium Awareness Project