Study finds arsenic levels high in Yellowknife-area lakes near Giant Mine

A study released Wednesday by researchers at the University of Ottawa, found arsenic concentrations higher than the Canadian drinking water guideline for arsenic in several lakes within 15 kilometres of Giant Mine.

University of Ottawa study finds high arsenic levels in several lakes within 15 km of Giant Mine

The Giant Mine in Yellowknife is shown Tuesday Aug. 21, 2001. The mine permanently closed in 2004, 56 years after it opened. (CP PHOTO/Chuck Stoody)

Another study has found high levels of arsenic in the lakes around Yellowknife's Giant Mine.

The study, released Wednesday by researchers at the University of Ottawa, found arsenic concentrations higher than the Canadian drinking water guidelines in several lakes within 15 kilometres of the mine.

The guideline is 10 micrograms per litre.

"Many of the lakes we sampled in the region were exceeding that value, particularly ones that are closest to the mine," said Jules Blais, a professor of biology and environmental toxicology at the university and a co-author of the study.

"So we would advise that if there's reason to think that the arsenic exceeds 10 micrograms per litre, [people] should be cautious when drinking the water, particularly if they're relying on water on a day to day basis.

"If people drink water that exceeds the guideline slightly, just occasionally from time to time, that's not the same as relying on that water every day."

Blais said if people are unsure about the arsenic level in a particular lake, they can contact the N.W.T. Department of Environment and Natural Resources, which has also done its own studies, partly based on the University of Ottawa study.

This map, produced by the N.W.T. Department of Environment and Natural Resources, shows the level of arsenic in lakes around Yellowknife and Giant mine measured in micrograms per litre, or ug/L. Canada's drinking water guideline for arsenic is 10 ug/L. (GNWT)

During the 50 years the Giant gold mine operated, about 20,000 tonnes of arsenic dust went up the roaster stack and settled on the ground and lakes around Yellowknife.

The Department of Environment and Natural Resources has released a map showing the different levels of arsenic in lakes around Yellowknife and the mine.

Blais cited that as a good resource, adding, "[People] should take note of how close they are to the mine and whether they might be at risk."

Blais' study did not look at Yellowknife River, the source of the city's drinking water. But he said, "the river has a very large drainage, which is mostly far removed from any industrial impact.

"There's no reason to doubt the tap water."

The City of Yellowknife does not treat its tap water for arsenic (though there's room for the equipment to do so at its new water plant) but does regularly monitor the level of arsenic in the water.

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