Air that we breathe
Sulphur dioxide levels lowest city's seen since the '50s

The closure of the roaster at Giant mine has played a big role in improving air quality in Yellowknife, resulting in lower levels of suphur dioxide emissions -- Merle Robillard/NNSL photo

Dawn Ostrem
Northern News Services

Yellowknife (May 10/00) - Yellowknife's air has reached normal levels for the first time in nearly 40 years, according to a recent study on Yellowknife's air quality conducted by the Department of Resources, Wildlife and Economic Development (RWED).

The report notes sulphur dioxide emissions in Yellowknife have decreased dramatically since last November, when the Giant mine roaster shut down.

Since Miramar Mining purchased the mine last December, the ore from the site has been taken to an autoclave unit at Miramar's Con mine and processed using chemical technology.

"When the roaster shut down, we began to see the true effects that emissions from the roaster had on air quality," said RWED environmental protection services director, Emery Paquin.

"The roaster did not have regulatory controls on it for sulphur dioxide and no capturing technology for sulphur dioxide."

According to air quality monitors set up in downtown Yellowknife, readings of sulphur dioxide have gone from peak concentrations of 600 to 800 micrograms per cubic metre in any one hour to below 25 micrograms per cubic metre.

The high numbers occurred for short periods of time depending on factors such as wind directions, Paquin said, adding, during the summer when concentrations were high stressed trees could be seen.

The yearly sulphur dioxide emission average in 1998 was 14 micrograms. But Paquin said that doesn't necessarily tell the whole story since the hourly standard of 450 micrograms was exceeded on 45 occasions, nine of which were above 900 micrograms.

"At (450 micrograms) vegetation damage begins to occur," Paquin said. "I would describe the effects as periodically impacting individuals with pre-existing respiratory ailments.

Lack of regulations

"There are no regulations in place," he added.

"We have cured that problem and the roaster emissions are now zero."

Paquin said air quality started being monitored in Yellowknife in the early 1990s when RWED started receiving complaints about the Giant roaster.

"There is no reason to believe that levels we observed in 1998 didn't exist since the beginning of roaster operations at the local mine. I truly believe the levels of sulphur dioxide we are seeing now are the lowest this city has seen since the 1950s," he said.

Public apathy to blame

Local environmentalist Chris O'Brien said the reason there were never government regulations pin-pointing a level in which sulphur dioxide emissions were considered hazardous is due to local apathy and economic ties.

"I assume it boils down to the folks in charge not wanting to get tough because jobs would be at risk," he said.

"There wasn't any hue or outcry from the people around town and the general public.

"If there had been regulations put into effect I assume the company would have said bye-bye."

Brian Labadie, senior vice-president of operations for Miramar, said his company would never have purchased the property if they did not have the resources to acquire gold from the ore another way.

Air-borne arsenic

"We made the acquisition because we had more modern technology with the autoclave as opposed to the roaster and because we had excess capacity to feed our autoclave," he said.

"Miramar would never have done a deal if we did not have excess capacity at the Con mine because we would never have run the Giant mill roaster and complex, and I mean never."

The ore processed at the roaster also produced airborne arsenic but unlike sulphur dioxide, 99 per cent of it was captured while operations were running smoothly through a filtering process.

It did, however, spike above what Ontario standards were in 1988 twice in that year due to pollution control equipment malfunctions at Giant mine.

From 1985 to 1997 arsenic has been recorded at varying levels in the air every year, according to an RWED report released in May 1999.

Natural sources

"Arsenic is called a non-threshold carcinogen which means at any level there is an increased likelihood of arsenic-causing cancer," Paquin explained.

"But there are other sources of arsenic than just the mine."

Arsenic is found naturally in the soil and water bodies in this area. The levels of arsenic for 1997 averaged 0.005 micrograms per cubic metre in downtown Yellowknife but Paquin expects that level will also decrease when a report is issued detailing those levels for 1998 and 1999 due to the roaster closure.

He added that the dispersion will not be as significant compared to sulphur dioxide because of the arsenic filtering measures that were already in place.