Mercury rising?
Studies take a look at mineral content in Northern lakes

Derek Neary
Northern News Services

Deh Cho (Feb 14/00) - The North may contain a significant portion of the world's declining wilderness, but toxic minerals exist in several NWT lakes.

The Northern Contaminants Program is funding a number of studies to investigate the presence of mercury in some territorial lakes, according to Glen Stephens, a contaminants specialist with the Department of Indian Affairs and Northern Development (DIAND).

"Mercury in the environment is one of the key issues in the North that's being addressed," Stephens said. "It's actually a big global issue as well."

There remains a question of what percentage of the mercury is naturally-occurring and what has been introduced by outside sources.

Erica Myles, contaminants consultant with the GNWT's Health Protection Unit, said due to development in the south, some of the mercury could exist due to "long-range transport" through air and water currents.

"That's something (researchers) are just starting to look at," she said.

In 1997, health advisories were issued for Lac a Jacques as well as Cli, Little Doctor, Turton and Manuel Lakes in the Mackenzie River region. Although the fish from these lakes were not considered to pose a health hazard, consumption limits have been recommended for certain species of fish.

It has been advised that predatory fish from these lakes be eaten in quantities ranging from 200 grams to 430 grams weekly (a can of tuna usually contains 175-225 grams).

Myles said it's important to remember that there's no need to panic. The advisories, which she acknowledged would still be considered valid, are based on consumption levels over a lifetime and are directed at those who eat fish from those lakes weekly.

"In general, the levels of contaminants in the Northwest Territories aren't high enough that we think they're going to cause significant health problems," she said.

"We put out these health advisories to protect people, to be on the safe side. But, it's very difficult to measure health effects specific to contaminants because people might be smoking and drinking. There's so many other factors affecting your health."

The side-effects of long-term, low-level mercury ingestion are not well known, according to Myles. Most studies have been conducted on animals over the short term, she explained. She said she's not aware of anyone in the NWT ever having been diagnosed with any sort of mercury poisoning as a direct result of eating too much fish.

Mercury can pass through the umbilical cord, potentially resulting in nerve damage to a fetus. Therefore, the advisories warn that pregnant women be particularly cautious about limiting their fish intake.

Predatory fish, particularly older and larger ones, tend to contain higher concentrations of mercury Stephens noted.

"Mercury tends to bio-accumulate over age and up the species," he said. "If there is a concern you should eat younger, smaller fish on the lower end of the food chain -- that's better than the great big lunkers."

There's no way to be sure if the mercury level in NWT lakes has fluctuated much over the years because of a lack of data, according to Stephens.

"You can have one lake which has high mercury levels and right next to it you'll have a lake with very low mercury levels," he said. "They just don't quite know the differences yet on why that happens and what's happening over time."

The Department of Fisheries and Oceans does conduct fish stock assessments in consultation with communities, Stephens noted. They have started to send some samples to the lab for analysis.

"So it's piggy-backing on an existing program. That's how a lot of the mercury data is started to get generated now," he said.

In addition, a researcher out of Saskatoon, Sask., is currently conducting studies on Cli Lake and Little Doctor Lake, he noted. Myles added that several proposals by researchers have been submitted to the GNWT to study fish in NWT lakes. A review process is under way and those that receive authorization to proceed for next year will be notified in April, she said.

Currently, the best known data for lakes in the NWT are for lakes that lie through the Mackenzie Valley because that's where most of the people live, said Stephens. Lakes where commercial fishing takes place are also the basis for study, he added.

The optimum frequency of sampling hasn't been well established, according to Stephens. Some of the best data on an NWT lake is for Lac Ste. Therese, which has three or four sampling periods over five-year spans.

"I don't think you'd get vastly different (results) from year to year," he said, adding that it's essential that the same class and size of fish are sampled for consistency and accuracy.

A long-term monitoring program is also being undertaken at Giauque Lake near the Discovery mine in the Yk area to determine how quickly fish can flesh out mineral content over a clean-up period.