Arsenic in Yellowknife mushrooms: 5 things to know

Morel pickers are being warned by the territorial government to stay at least 50 kilometres away from Yellowknife, due to arsenic found in the soil. We look at how mushrooms take up contaminants, what it means for gardening season, and more.

Morel pickers warned to stay 50 kilometres away from city, but what does that mean for gardening season?

The Northwest Territories is expecting a bumper crop of morel mushrooms this season, but the territorial government is warning pickers not to stray too close to Yellowknife. ( Shawn Ryan)

Last year's record-breaking 2014 forest fire season has the Northwest Territories primed for a mushroom picking boom: the territorial government has said that this season's morel mushroom harvest — valuable mushrooms that grow in burned-out areas — could be worth up to $10 million.

To prepare residents interested in taking part in the harvest, the government has held information sessions across the territory over the past week, but one piece of advice has would-be pickers near the capital city of Yellowknife concerned.

"Arsenic and heavy metals can be anticipated to be in mushrooms, which would include morels, around Yellowknife and the surrounding area," reads a statement from Drew Williams, a spokesperson for the territorial government's Department of Industry, Tourism and Investment. "The recommended distance from Yellowknife that we have been using in information sessions is 50 kilometres."

Arsenic woes are common for Yellowknife-area residents, a byproduct of the now-closed Giant Mine: last year, levels found in the city's lakes were four times the recommended limit for drinking water. Here are five things to know about the high arsenic levels found in the city's mushrooms, and whether you should be concerned for your own garden:

1. All mushrooms around Yellowknife can be dangerous

First, the bad news: make no mistake, any mushrooms in the Yellowknife area — not just morels — run a major risk of containing high levels of arsenic. 

Joachim Obst, a naturalist who has been studying mushrooms in the Northwest Territories for over 30 years and has been leading the territorial government's information sessions for morel pickers, says that "scientists have known since the 1960s that you can't eat those mushrooms."
The tower at the now-closed Giant Mine. Joachim Obst says he has been warning locals not to eat mushrooms harvested at popular local picking spots near Giant Mine for the past 18 years. (CBC)

"The science has been known for 50 years that mushrooms near mine sites contain heavy metals and contaminants," says Obst, who wrote a study last year stating that an adult could exceed the daily Canadian health standard for toxic organic arsenic by consuming as little as 1.4 grams of contaminated mushrooms found near the city. 

"People have been harvesting for 30 years, mushrooms growing right outside the entrance to Giant Mine," says Obst. "I was alarmed 18 years ago when I watched people picking those mushrooms, and I've been telling people: 'please don't.'"

2. There aren't expected to be many morels in the affected area

Though Yellowknife has become a popular picking spot for many types of mushrooms, including pine mushrooms and shaggy manes, Williams says that there will likely be little reason for morel pickers to cross the 50 kilometre radius recommended by the government.

There is no reason to believe that there will be any significant morels in the 50k perimeter of YK- Drew Williams, Department of Industry, Tourism and Investment, Government of the Northwest Territories

"The entire morel harvest story is focused on last summer's burn area, which is not in the immediate Yellowknife proximity," he said in an e-mail to CBC. "If they were to grow, they would probably be contaminated (all mushrooms can assumed to be to some extent).

"That said, there is no reason to believe that there will be any significant morels in the 50k perimeter of YK — because there were no fires."

3. Don't panic about your garden

Though there have been issues with contaminated soil in Yellowknife in the past, Jackie Milne, president of the Northwest Territories Territorial Farmers' Association, says that there's an important distinction to be made between how mushrooms and plants ingest nutrients. 

"Plants, out of their tissue structure, molecularly, only a small percentage is minerals drawn from the soil," says Milne. "Mushrooms are unique. They do not perform photosynthesis. So the bulk of what they are made of is by pure salvaging, and drawing everything they need from the soil, from the matter, from the wood and the air."

Despite the lower risks run by plant species, Milne, who lives in Hay River, says that any concerned gardeners should consider getting their soil tested for contaminants if they're worried, adding that's what she'd do.

"Noone really knows, because of the wind and the drift in the past, where the arsenic might have accumulated in the city," she says. "I'm sure there are some spots where it's fine. But maybe there's other questionable areas."

4. It's easy to have your soil tested

Milne says getting your soil tested is as easy as opening a Google search.
Jackie Milne, of the Northwest Territories Territorial Farmers Association, says that there are significant difference between how plants and mushrooms draw nutrients out of the soil. (Facebook/Jackie Milne)

"If you go online, there are lots of places that test soil for agricultural use," she says. "You can get a very comprehensive molecular breakout of what is in your soil.

"You just take a little garden shovel, and you'll dig a little straight skinny hole down. And you might take it from 3 or 4 different places on your property and mix it together, so you get an average. It's definitely worthwhile."

Some testers, according to Milne, offer soil testing for as little as $100. However, she says that she would be in support of a government contribution agreement that would assist gardeners to test their own soil. It would "make it simpler for people, so they won't be intimidated," she says. "And it shouldn't be all that much, really."

5. Mushrooms can be used to clean up mine sites

Although the thought of mushrooms drawing arsenic out of the soil is undoubtedly concerning for Yellowknife residents, researchers have been using the fungi for years to clean up contaminated mine sites and oil spills. Some mushrooms have even been proven to eat away radioactive waste. 

"It's proven that you actually can remediate certain contaminated sites with certain species of mushrooms," says Obst. "Not only toxic heavy metals, but also persistent organic pollutants. The only problem in Yellowknife we've got is with arsenic trioxide, currently there is no known mushroom or fungus which would transform arsenic trioxide into a harmless arsenic species."

However, just because there isn't currently a way to use mushrooms to help clean-up the 200,000-plus tonnes of arsenic currently sitting under the city, Milne says that it's an area that is worth researching.

"It'd be wonderful to see if there are some ways to remediate areas that might be high in arsenic," she says.

"If it was possible that we could find a mushroom that could concentrate arsenic into its tissue, then you could purposely grow them, collect them, and then the mushrooms could be safely disposed of."


Garrett Hinchey

Managing Editor, CBC North

Garrett Hinchey is a Métis journalist based in his hometown of Yellowknife, where has worked since 2014. He has worked at CBC North as a social media presenter, copy editor, multimedia reporter, and senior assignment producer. He has been CBC North's managing editor since June 2021.