Contaminant study finds few concerns in Yellowknife area

Last modified: May 15, 2019 at 3:25pm

The first results of the Health Effects Monitoring Program are in – and in most cases, residents’ contaminant levels in Yellowknife, Dettah, and Ndilo are quite similar to people’s levels across Canada.

The data was collected as part of the program’s first phase: determining baseline levels of exposure to arsenic, lead, and cadmium.

As the Giant Mine Remediation Project gets under way, the monitoring program will resample children in 2022 and adults in 2027 to ensure levels of arsenic and other contaminants are not increasing due to mine remediation work.


In total, 2,037 people participated in the study – 506 children and 1,531 adults – which involved toenail, urine, and saliva samples; a lifestyle questionnaire; a food frequency survey; and a review of medical records from the past five years.

While researchers currently only know the levels of contaminants found in the urine and toenail samples, over the next year the remaining data will be analyzed to determine possible sources of arsenic and other contaminants.

The researchers will return to Yellowknife in 2020 to present the new findings.

Their studies are federally funded but the researchers operate independently, led by principal investigator Dr Laurie Chan from the University of Ottawa.

Of the participants, 890 were randomly selected. Others were volunteers from Yellowknife, the Yellowknives Dene First Nation (YKDFN), and the North Slave Métis Alliance.


Chan explained the volunteers had slightly higher levels of exposure to contaminants.

“Usually people who come to the study have some suspected exposure, because they may be working at the mine or drinking water from the lake or doing something that they believe may have high levels,” said Chan at the first of two public presentations on Tuesday evening.

The second community meeting will take place in Dettah at Chief Drygeese Hall on Thursday at 6pm.

The participants in the study were sampled in two waves – the first in the fall of 2017 and the second in the spring of 2018. Researchers thought seasonal changes might affect levels of arsenic exposure as they’d heard from the community there is more dust in the spring..


In their progress report, the research team indicated toenail arsenic concentrations were higher in the second wave, suggesting “there may be seasonal influence in arsenic exposures.”

Contaminant reference levels

The monitoring program used the 95th percentile of inorganic arsenic, lead, and cadmium concentrations as a reference level – meaning anyone exceeding that mark would have levels higher than 95 percent of the Canadian population, as determined by the Canadian Health Measures Survey.

In total, 225 of the the participants in the study had at least one contaminant that exceeded the reference level.

All participants have received their individual, confidential results.

Those whose results are higher than the reference levels have been invited to meet with a nurse practitioner to discuss how they can lower their exposure to contaminants and discuss possible effects on their health.

Arsenic levels

For arsenic, this reference level is 21 μg/L (“μg” stands for “micrograms”). The average Canadian has an inorganic arsenic level of 5.4 μg/L, while in Yellowknife children’s levels averaged 6.6 μg/L and adults’ averaged 5.3 μg/L.

This means, in this instance, researchers found no meaningful difference between the Yellowknife community and the rest of Canada.

In fact, the Yellowknife population had “significantly lower urine total arsenic than the general Canadian population,” stated the report.

However, inorganic arsenic levels in children aged six to 11 were slightly higher than their peers of the same age across Canada; and the toenail results showed higher levels of arsenic in children than in adults.

As arsenic does not build up in the body, this study was collecting baseline data that shows a snapshot in time of people’s current arsenic exposure – the urine samples show contaminant exposure over the past few days, while the toenails show arsenic exposure over the past few months.

A slide showing urine arsenic levels.

A slide showing urine arsenic levels.

A slide showing toenail arsenic levels.

A slide showing toenail arsenic levels.

“The results were similar to other studies that were done in populations living in old mine sites,” noted Chan.

He explained that in other studies, there is no difference between adults and children because the arsenic is usually coming from the drinking water.

But as the City of Yellowknife monitors arsenic in the drinking water all of the time and the levels are very low, the researchers do not believe Yellowknife residents are being exposed to high levels of arsenic in this way.

“So this evidence – we don’t know yet, but it’s pointing to the direction that because children crawl around and play in the dirt, they ingest more soil compared to adults,” Chan said.

“It is important to note that arsenic occurs naturally in the Yellowknife area because of the local geological formations,” the researchers cautioned in their report, noting their study does not currently distinguish between arsenic exposures from nature, Giant or Con mine, or dietary sources.

Lead levels

Looking at lead, the reference level is 1.3 μg/L for children and 1.9 μg/L for adults.

The Yellowknives Dene had elevated levels compared to the Canadian average: in YKDFN children, the average was .52 μg/L compared to the Canadian average of .42 μg/L.

In adults, YKDFN members had lead levels of .66 μg/L while the Canadian average sits at .54 μg/L.

A slide showing lead levels in people.

A slide showing lead levels in people.

“We will have some discussion with YKDFN leaders to see whether we need to do anything to look at potential sources of lead exposure. Lead can come from the soil or from dust or from old paint or water pipes … or lead containing ammunition,” noted Chan.

Cadmium levels

Meanwhile, cadmium levels in Yellowknife residents were much lower than expected.

“It was a little bit of a surprise to me,” said Chan, who thought higher percentages of people who smoke in the North would mean higher cadmium levels.

Cadmium, which remains in the kidneys for years, can be found in cigarette and tobacco smoke.

Adults’ cadmium levels in the study were nearly half of the average Canadian’s, while children’s levels were even lower.

A slide showing cadmium levels in people.

A slide showing cadmium levels in people.

In the random sample, the average Yellowknife child had a cadmium level of .06 μg/L compared to a Canadian average of .26 μg/L and a reference level of .7 μg/L.

In Yellowknife adults, the random sample found a .22 μg/L level of cadmium compared to a .41 μg/L level across Canada. The reference level for adults is 1.3 μg/L.