Kent Driscoll
Northern News Services

Yellowknife (June 27/05) - The air you breathe in Yellowknife is filled with chemicals, particles and complex oxides.

It sounds threatening, but the city's air quality is "very good," according to Graham Veale, air quality program director for the department of environment and natural resources.

Airborne toxins monitored in Yellowknife: Sulphur dioxide-SO2 Primarily from diesel fuel. NWT standard: 172 parts per billion (ppb) per hour. In 1994 that standard was broken 60 times. In 1997, it was broken 20 times. It hasn't been broken since Giant Mine closed in 1999. Nitrogen oxides-NOx From combustion of fuel, home heating and nearby forest fires. Federal standard: 213 ppb per hour. The average hourly Yellowknife reading was 5 ppb in 2004 and the highest recorded reading for one hour was 35 ppb. Carbon monoxide- CO From combustion sources, mostly motor vehicles. NWT standard: 13 parts per million (ppm). The average level in the NWT is .1 to .2 ppm, but it peaks at between 1.5 and 1.9 ppm during rush hour. Ground level ozone Forms in the atmosphere from a reaction with volatile organic materials and Nitrogen oxide. NWT standard: 65 ppb per eight hours. Canadian standard: 70 ppb per eight hours. The average level for Yellowknife in 2004 was 23 ppb, and the highest eight hour reading was 47 ppb. Fine Particulate 2.5 micrograms or smaller Particles in the air, most commonly caused by forest fires. NWT standard: 30 micrograms per metre cubed (mgpm3) in a 24-hour period. The highest 24-hour reading in 2004 was 125 mgpm3. The highest one-hour reading was 337 mgpm3, during a forest fire in July.

"Apart from the springtime dust events, the air quality in Yellowknife is very good. We do not see our standards exceeded," he said.

Things have improved over time, after the closure of Giant Mine.

Between 1994 and 1999 the average hourly reading for sulphur dioxide was three to six parts per billion (ppb). Now, it is less then one ppb.

In 1994, the mine contributed to beating the legislated level 60 times. By 1997, the standard was broken 20 times.

The standard has not been beaten since Giant Mine closed in 1999.

Air quality warnings are uncommon in Yellowknife. The only warnings issued have been when smoke from forest fires clouded the skies.

Dr. Andre Corriveau, chief health officer for the NWT, doesn't need an advisory to know when there is smoke in the wind.

"Mostly we can tell when the air quality is good," said Dr Corriveau.

"We put the air quality readings together with what we hear from the emergency room."

In larger cities, smog is the greatest issue; in Yellowknife, it's small particulate from fires.

"The smaller it is, the deeper it goes," said Veale.

Larger particles are caught in the nose and mouth, smaller ones get to the lungs. The current system looks for dust smaller then 2.5 microns.

Two weeks ago, before rain washed away most of the small particles, they were getting readings of 26 micrograms per cubic metre. On a clear day, the reading is usually near 10.

Veale sees a rise in carbon monoxide readings every day at 9 a.m. and 5 p.m, brought on by the city's brief rush hour and idling vehicles. The average hourly rating is .1 ppm, but the rush hour peak ranges from 1.5 to 1.9 ppm.

The federal government financed the city's air monitoring equipment.

Each of the four gas monitors is worth as much as $20,000 and has a life of eight to 10 years, although some can last up to 20. The particulate collector cost $25,000.

Funding to maintain the air collectors comes from the territorial government. The budget is between $1,500 to $2,000 a year, mostly for filters.

Outside Yellowknife

There are air quality monitoring systems in Inuvik, Norman Wells and Fort Liard as well, funded by the territorial government.

The stations also monitor for hydrogen sulphide, a product of oil and gas wells. The numbers are low, but expected to go up.

"If we have a lot of development, this will give us the baseline numbers," said Veale.