If you have ever wondered what is going into your lungs when you inhale in downtown Whitehorse, the filter in Janine Kostelnik's hand holds some of the answers. The grey dust coating the filter paper looks not too different from the gunk you find inside your vacuum filter, but this stuff has a very specific name -- Total Suspended Particulates.

Kostelnik is an analyst with the Environmental Protection and Assessment Branch of the Yukon Department of Renewable Resources. She has just removed the filter from a sampling machine located on the roof of the Andrew Philipsen Law Building in Whitehorse.

Down in the basement of the building, two other sampling machines collect data on carbon monoxide and nitric oxides at ground level. This air monitoring system is part of the National Air Pollution Surveillance Program (NAPS), which is set up to monitor and assess urban air quality around the country.

In general terms, it is not too hard to tell when the air quality is less than desirable in Whitehorse. On cold, calm winter days, when smoke from wood-burning stoves and vehicle exhaust is trapped in a lower layer of stagnant air, the filters show what is floating around in the air.

"When it is really cold and snowy, you can see black goop up to an inch thick on the filter. It is a combination of snow mixed with dirt, and it smells like woodsmoke," she says.

But right now it is another balmy winter day in Whitehorse -- not a temperature inversion in sight -- and the deposit on the filter does not look too threatening.

The term TSP describes a range of particles that are small enough to hang in the air for hours or weeks, and includes dust, soot, smoke and, occasionally, more complicated organic compounds. TSP levels can spike upwards when spring winds whip up lots of dust, or when forest fires produce blankets of smoke.

TSP levels have dropped substantially since monitoring began in 1974. A recent summary of Whitehorse air quality data shows that in general, air in downtown Whitehorse is quite clean. The report summarizes data through 1998, and found that national air quality standards were only exceeded on two occasions in that year.

The report does point out though that air quality can vary from place to place around Whitehorse, so results for downtown Whitehorse do not necessarily represent other locations like Riverdale.

Levels of woodsmoke can be a concern in Riverdale, and the City of Whitehorse used to monitor air quality in the subdivision and impose "No Burn" periods when the levels were high. The City shut down this monitoring station in Riverdale in 1997.

Air quality data is most useful for monitoring when it is available right away. The TSP monitoring equipment kicks in once every six days, and pulls air into the unit for 24 hours. Kostelnik ships filters off to Environment Canada in Ottawa once a month for analysis.

But sometime this year Whitehorse is supposed to receive a new sampling unit that will provide the TSP data as it is received. A sampling machine for ground level ozone should also be in place soon.

The data on carbon monoxide and nitric oxides is available right away. Air samples for these gases are sucked into the sampling units from an intake next to the Law Building's parking lot. Kostelnik can download this data at her computer as soon as it is recorded.

Levels of carbon monoxide have decreased since monitoring began in 1984, and Kostelnik suggests that warmer winters could have something to do with it. Carbon monoxide is produced by incomplete combustion; it spews out of tailpipes and wafts out of the chimneys of homes heated with firewood, so levels of this colourless, odourless gas go up as temperatures go down.

The Whitehorse monitoring station is operated jointly by the federal and territorial governments, and keeping the equipment up and running has had its challenges over the years. Problems with the sampling machines have led to gaps in the data, particularly for nitric oxides. But the available data indicate that levels of these gases are well below what is recorded at other Canadian sampling stations.

Since Whitehorse does not have a lot of smokestack industries, these results are not unexpected. In other urban regions, air-monitoring stations can be located near industrial areas as they produce most of the air quality problems.

Kostelnik says that once it is possible to download information right away on TSP levels, as well as on the other gases, it will also be easier to track air quality in Whitehorse and address any public health concerns.

For more information on the air-monitoring program, contact Janine Kostelnik at 667-5456 or by e-mail at janine.kostelnik@gov.yk.ca.