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Reduce level of tritium deemed safe in drinking water, experts urge

The Globe And Mail: Martin Mittelstaedt - June 10, 2009

An expert panel in Ontario is recommending that the province adopt the toughest standard in the world for the amount of cancer-causing tritium considered safe in drinking water.

Tritium is the main radioactive contaminant found in Ontario water supplies, and, although small amounts are produced through natural processes, most of what is detected comes from leaks at nuclear power plants, Atomic Energy of Canada Ltd.'s Chalk River research facility and several glow-in-the-dark sign companies.

The recommendation, from the Ontario Drinking Water Advisory Council, would cut the amount of tritium allowed in drinking water to an average of 20 becquerel per litre over the course of a year, from the current level of 7,000 bq/L. A becquerel is a scientific term indicating the number of radioactive disintegrations in a substance every second.

Jim Merritt, chair of the council and a former assistant deputy minister of environment, said in an interview that the proposal, if adopted, would be the most rigorous anywhere.

Tritium releases are one of the worries at AECL's now-shut-down NRU reactor that produces medical isotopes. The company has detected a leak of tritium containing heavy water at the reactor and is storing the radioactive material at the site, although it said last month that some of it is evaporating and getting into the reactor's ventilation system.

The review of the dangers of tritium by the panel, which is composed of some of the province's top experts in drinking water safety, is one of the most thorough ever done in Canada, and suggests that the Health Canada guideline of 7,000 bq/L for water may be out of date. Europe has moved to a standard of 100 bq/L, and the U.S. Environmental Protection Agency has set its safe level at 740 bq/L.

California has a non-enforceable objective of 15 bq/L, but for regulatory purposes uses the EPA standard.

The new Ontario recommendation vindicates the work of a previous expert group for the Ontario government, which proposed adopting the same lower limit in 1994. At the time, the recommendation was shelved after heavy pressure from the nuclear industry.

The panel's recommendation was placed yesterday on a government website. Ontario Environment Minister John Gerretsen has received a copy of the report, and will make a decision on changing the standard after a public comment period. No date has been set for his decision.

According to Mr. Merritt, the panel based its proposed limit on a view that it would be acceptable to have only one additional case of cancer among a million people due to tritium exposure. The Health Canada guideline was calculated on a different basis, using a figure that 600 extra cancers in a group this size were acceptable.

If accepted, the new standard could be used as a justification to temporarily shut drinking water treatment plants near nuclear facilities if they have large leaks of tritium, a radioactive form of hydrogen that is produced during the normal operation of Canadian-designed Candu nuclear power plants.

Ontario has been reviewing the adequacy of its standard because of pressure from the City of Toronto and its board of health, which asked for an assessment leading to a new level in 2006.

Currently, all water treatment plants in the province would be under the proposed annual standard, but one, in Port Elgin, with median readings of 16 bq/ L, is close to it. As well, plants in Ottawa, Southampton and Kincardine have occasional levels of more than 20 bq/L, according to the expert panel's report. Toronto's level is around seven bq/L.

Ontario surface water that isn't near nuclear plants has two bq/L to three bq/L of tritium from natural sources and from the legacy of nuclear weapons testing in the 1950s and 1960s.

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