Researcher raises Muskrat methylmercury alarm, but Nalcor contractor says levels safe

There's mixed messaging emerging from the debate over methylmercury contamination in Labrador, with a U.S. researcher again raising the alarm about the toxic organic compound, while a contractor monitoring the effects of Muskrat Falls — backed up by the Department of Environment — says there's no need to worry.

Ryan Calder co-authored a 2015 study by researchers at Harvard University saying hundreds of Labrador Inuit will be exposed to dangerous levels of methylmercury once the Muskrat Falls reservoir is fully flooded.

The report was rejected at the time by Nalcor Energy, the government-owned corporation building the controversial hydroelectric generating station and dam on the Lower Churchill River.

Calder has since moved on to research university Virginia Tech, but has continued to follow the findings of an ongoing monitoring program on the river and in Lake Melville.

He said recent data showing an increase in the toxin is cause for concern.

"There's a small number of people that eat enough fish and marine mammals for it to be a concern," Calder said during a phone interview. "Probably in the hundreds of people among the Labrador Inuit that would be pushed beyond the Health Canada and EPA [United States Environmental Protection Agency] reference sources for mercury exposure."

But Jim McCarthy — a senior biologist with Wood Environmental Infrastructure Solutions, which has been contracted by Nalcor to lead a methylmercury monitoring program in central Labrador — disagrees.

It's now been a full year since the Muskrat Falls reservoir was filled to capacity, and McCarthy said methylmercury levels in the Muskrat reservoir has average 0.06 nanograms (one billionth of a gram) of methylmercury per litre of water. 

And as expected, McCarthy said levels increased in the summer, reaching as high as 0.2 nanograms per litre in one sample, with the 2020 summer average at 0.07 nanograms per litre.

The natural levels prior to reservoir flooding was 0.017 nanograms per litre, said McCarthy.

So is McCarty alarmed by those numbers? 

"That's not high at all," he said. "To put it in terms of drinking water quality, there'd be an advisory on if the water quality had 1,000 nanograms per litre of methylmercury."

The main concern for area residents is their wild food supply becoming contaminated with unsafe levels of methylmercuy, and so far there is no evidence of this, said McCarthy, who has been studying the water and fish in the Churchill River for two decades.

Fish samples collected in 2019 did not show any changes in methylmercury levels from previous years.

McCarthy is awaiting laboratory results from fish samples collected in September and October, but is not expecting any significant change again this year.

McCarthy said it can take anywhere from three to five years for higher concentrations of methylmercury to appear in fish, and, he said, "I don't expect it to be much."

When asked if he envisioned a scenario where area residents might be advised against consuming fish or mammals, McCarthy said, "I"m not a human health person, I'm a fish person. But I don't believe so, based on the data that I've seen, I don't think there'll be advisories."

The Environment Department said methylmercury levels are below the Canadian Council of Ministers of the Environment's guidelines.

"To date, monitoring data confirms that the actual methylmercury levels are far below predicted levels by CCME guidelines for aquatic life," a department spokesperson wrote in an email to CBC News.

A statement from Nalcor says, "The Muskrat Falls reservoir is reacting in a similar way to other reservoirs following the first year of flooding."

In fact, Nalcor says average methylmercury concentrations in the reservoir are slightly lower than predicted for the past year, at 0.058 nanograms per litre. The concentrations decrease further downstream, said Nalcor.

"We've noticed that there is an increase, but not a very large increase," said McCarthy.

McCarthy said it's common for concentrations to increase in the first three years after reservoir flooding, and eventually return to natural levels.

He said he could easily find a pond dammed by a beaver anywhere in the province and find higher concentrations of methylmercury.

He stressed that the consumption of fish and mammals should not be avoided.

"I think they're safe to eat, yes," he said.

Ballooning project costs and long delays have dogged the Muskrat Falls hydroelectric project for years, but human health concerns have also been at the forefront, especially for those who eat fish and other mammals in the region.

The threat of methylmercury contaminating the wild food supply resulted in protests four years ago, and a prolonged impasse was resolved after the provincial government agreed to establish an independent expert advisory committee.

An enhanced monitoring program was also launched, with weekly testing at more than a dozen sites upstream of the Muskat Falls reservoir, downstream into Lake Melville, as far as Rigolet.

The issue flared again last year after the provincial government failed to deliver on a promise to clear some vegetation — a process known as wetland capping — from the reservoir prior to full flooding, with then premier Dwight Ball calling it an unintentional oversight.

Nalcor responded by allocating $30 million in compensation for three Indigenous groups in Labrador.

Meanwhile, Ryan Calder says the data emerging from river monitoring is supporting his early concerns about methylmercury.

"The first data that's rolling out is consistent with our predictions, and is exactly what Nalcor refused to believe five years ago," said Calder.

"Immediately the levels are going way beyond the Nalcor projected peak, and are now well within the range of what we had predicted. And they're still rising. The fact that we're in late November now and the levels are still rising quite sharply, when they usually are falling, is a concern. And it suggests they'll probably continue to rise next spring and summer."

When asked why Calder's tone is so different from his own, McCarthy replied, "Well, there's two conflicting models too, I guess."

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