Arsenic Warning: Fishing, Swimming Off-Limits in Several Yellowknife Lakes

Don’t swim or fish in Frame Lake.

That sage bit of advice is already followed by most Yellowknifers, but any hope of opening up the once-popular Frame Lake beach after some serious lake cleanup was effectively put to bed today with a health advisory from the territory’s public health officer.

Frame Lake, Jackfish Lake and around a dozen other small lakes near the Giant Mine bypass road are not safe for swimming, drinking or fishing due to heightened levels of arsenic, Dr. André Corriveau announced today. Frame Lake, in particular, has arsenic levels more than 10 times the limit suggested by Health Canada’s safe drinking guidelines.

“This information won’t be a surprise to most of us who have been living here for a while, but it’s important to be transparent.” 

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“The science tells us there’s very poor absorption of arsenic through the skin, so the occasional dip wouldn’t be of concern. But when people swim, they occasionally swallow water,” said Corriveau, advising against swimming or fishing in any of the lakes where arsenic levels were greater than 52 parts per billion (ppb).

Corriveau’s public health advisory comes on the heels of a pair of studies, one from the University of Ottawa and one from the NWT Geological Survey, that found arsenic levels exceeded federal drinking water standards in dozens of lakes within 30 kilometres of Giant Mine.

Folks won’t be playing like this in Frame Lake again any time soon. Taken by Ted Grant, 1967. CREDIT: NWT Archives/Northwest Territories. Dept. of Information fonds/G-1979-023: 0146 

The most contaminated lakes tend to be small ones with little runoff — mostly within five kilometres of the old Giant Mine roaster and to the northwest of the mine, where the prevailing winds blew arsenic dust during the mine’s early years of operation. In this group of lakes, which include several along the Prospector’s Trail behind Long Lake, arsenic concentrations are “consistently above 100 ppb …and one lake is higher than 600 ppb.” 

For the areas around these lakes, it also was recommended that people “avoid harvesting berries, mushrooms and other edible plants within this zone. However, walking through this area does not pose a health hazard.”

Luckily, the bodies of water near Yellowknife most commonly used for recreation don’t pose much of a risk to human health, and Corriveau was quick to note that “we can, for the most part, enjoy the recreational opportunities around the city…without undue concerns.”

This includes Long Lake, Vee Lake, Martin Lake and Lower Martin Lake, where arsenic levels do exceed federal drinking standards, but at a level low enough that “occasional exposure does not pose a significant risk for arsenic-related health effects.” Still, the advisory recommended against drinking from them.

Map of arsenic concentrations in lakes surrounding Yellowknife | Courtesy of GNWT

Larger lakes with cabins on them like Prosperous and Walsh were deemed largely safe, having arsenic levels lower than the recommended limit.

“This information won’t be a surprise to most of us who have been living here for a while, but it’s important to be transparent,” especially with newcomers and visitors, Corriveau said.

Over the next several months, the GNWT and City will be working together to put up signs near accessible lakes like Frame Lake and the ones along the Prospector’s Trail. More research into the effects of arsenic on the ecosystem is ongoing, with another study from Queen’s University expected to be published this summer.

Overall, “there are no significant public health risks,” said Corriveau, so long as we’re not doing laps in Frame Lake or filling our plates with fish from Jackfish Lake. But, he added, “we will continue to review the data as it comes in and adjust our advice accordingly.”


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