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Update on arsenic concentrations in lakes around Yellowknife

The NWT Chief Public Health Officer provided an update on arsenic levels found in some of the lakes located around Yellowknife today.

Niven, Range, and Fiddler Lake have been added to the public health advisory map.

Niven Lake, which was formerly used as a sewage lagoon, is not recommended to swim in, and health officials are advising people not to to harvest berries or other edible plants from the surrounding area.

Niven Lake has arsenic levels of 46.9 parts per billion (ppb), which is below the 52 ppb threshold that has been set for caution.

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Fiddler Lake has arsenic levels of 11.1 ppb, and Range Lake is at 33.4 ppb but is safe to swim in.

According to Health Canada’s guidelines, water is safe for drinking if it has less than 10 parts per billion of dissolved arsenic.

Additional surface soil data has resulted in the expansion of the “area of interest”, which is defined as areas of land adjacent to water bodies with elevated arsenic, in close proximity to a mine site, or where high arsenic soil concentrations have been documented.

Results from the recently released Human Health and Ecological Risk Assessment (HHERA) have been incorporated in this public health advisory.

The HHERA results indicated very low human health risk for arsenic exposure for Yellowknife, Ingraham Trail and Dettah residents and low human health risk for arsenic exposure for N’dilo residents.

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What about fishing?

A human health risk assessment is being done to help understand the effects of this contamination on people who have cabins, and hunt, fish, or hike and camp around Yellowknife.

The GNWT recently asked the public for help collecting fish samples to study the extent of contamination in the environment from former mining operations around Yellowknife.

Based on contaminants studies that have been done to date and the HHERA results, fish from Back Bay and Yellowknife Bay are safe to eat. The advisory currently recommends avoiding eating fish from lakes with arsenic levels above 52 ppb.

Fish caught in Jackfish Lake should not be eaten, because the lake’s arsenic levels fall between 52 and 99.9 ppb (orange dot on the map).

Officials are also advising people not to swim in Kam Lake, or harvest berries or plants nearby, because it has arsenic levels above 100 ppb (dark red dot on public health advisory map).

Residents can continue to paddle on the lake or walk through the area, because walking or hiking through a contaminated area does not constitute a risk in and of itself.

Arsenic is not absorbed in any significant amounts through the skin. Significant exposure can only occur through regular ingestion or inhalation. 

Click here for the map of arsenic concentrations in lakes in and around Yellowknife.

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