The Particular Nature of T.O. Smog

By JOSEPH HALL
Sunday, July 17, 2005, The Toronto Star 

Perhaps the most disturbing place to view the spectacle of smog on a scorching summer day in Toronto is from the exit ramp off Highway 427 as it swoops down onto the eastbound Gardiner Expressway.

Because the city you expect to appear while making that slow, descending turn isn't there.

You see straight lanes of puffing cars made distorted and wobbly by the refraction of light through the slimy air.

You see the city's striking skyline — even the world's tallest freestanding structure — obscured or obliterated by a bile-coloured brume.

In short, you see the pall of air pollution as it sucks the colour and breath out of the baking downtown core.

Jeffrey Brook, on the other hand, sees the most exciting thing in all of atmospheric chemistry.

The senior Environment Canada scientist is one of the world's most respected smog experts. And he readily admits that one massive component of the smog that so diminishes summertime Toronto is an ongoing mystery to the people who study Earth's atmosphere.

"It's really where the excitement is in atmospheric chemistry right now," says Brook, who has studied smog for more than 15 years.

Brook is talking about the microscopic particles that make up half of the smog equation, and which still leave scientists stymied.

Smog's brownish yellow hue is caused in part by polluting gases — the other half of the smog equation — absorbing the light of the sun.

But its trademark discolouration is mostly the shadow of floating particles — billions of them, often 10,000 particles per cubic centimetre of air on bad smog days.

And scientists literally have no idea what the vast majority of these nasty specks are.

Where do they come from? How do they form? How do they combine, mutate and disappear over their lifetimes?

And most importantly, what are the health implications of this mysterious particulate matter on the people who are forced to breath it in?

These are the questions that are now at the forefront of smog research.

And in a city that has already surpassed its annual record for bad air days, with plenty of stifling summer left to come, they're questions that have taken on an urgent import.

For decades, the term "chemical soup" has been used to describe urban smog. In the past half-century, researchers have built an extensive knowledge of the component gases — the nitrogen oxides and ozone and sulphur dioxides that go into it.

But scientists have only recently begun to seriously delve into the particulate piece of the pollution puzzle.

"In terms of a chemical soup, we understand the (broth) quite well," says York University atmospheric scientist Geoff Harris, referring to the gaseous elements of smog.

"But we know very little about the lumpy bits."

Harris, the first holder of York's Guy Warwick Chair in Atmospheric Chemistry, estimates research into smog's particulates may be lagging 30 or more years behind the studies of its gaseous side.

Several factors have contributed to this discrepancy, he says, including early clean air regulations of the 1960s, centred mainly on smog-bound Los Angeles that concentrated almost entirely on gaseous ozone and ignored the particle matter.

As well, Harris says, technologies to study atmospheric gases were well established by the mid 1950s, when smog emerged as a serious public health concern.

Plucking microscopic particles from the air and dissecting them into their component molecules, meanwhile, is still proving a difficult chore.

"We still don't have the technologies to understand the particulates," Harris says.

"We're getting better and better at it but it's still a problem to understand just what's there, let alone where it comes from."

Thirdly, Harris says that, until the past decade or so, researchers were ambivalent, from both a health and academic perspective, about the importance of the particles.

"The particles were sort of there and obvious and visible," he says. "But people didn't know enough about them to worry about whether there was much chemistry to them or whether it was just basically smoke."

They know better now.

The particle research that has been completed to date has shown the murky specs to be enormously complex in their chemistry, their formation processes and their sources.

There is also accumulating evidence that they represent a serious public health danger and may be playing a large role in the 5,800 annual deaths that the Ontario Medical Association lays at smog's doorstep in this province.

"In the last few years, the research (on particulate matter) is turning into an avalanche, and it is an exciting time to be around," says Dr. Ted Boadway, executive director of health policy at the OMA.

"We're understanding things that five or six years ago we thought we'd never understand or only dreamed we would at best."

Up on the sweltering roof of the Ontario Environment Ministry building on Resources Rd. in Toronto, an array of vacuum-operated sensors pull in puffs of the city's air 24 hours a day.

As 16 lanes of cars stream by on Highway 401, some 50 metres to the north, the sensing equipment silently sucks the air down into a cluttered laboratory below, where some of the world's most advanced atmospheric gadgets flash their findings.

"This is one of 38 air-quality index stations we have around the province," says David Yap, senior scientific adviser with the ministry's monitoring and reporting branch.

There are sensors measuring nitrogen oxides, sulphur dioxides, ozone, carbon monoxide and reduced sulphur gases, all in precise, parts-per-million detail.

But just one lonely machine devotes its digitalized attentions to measuring particles.

And it doesn't discriminate. Any particle — dust or soot, liquid or solid, organic or inorganic — will do.

So long as the specs are 2.5 microns in diameter or smaller (a human hair is typically 75 microns wide), they all get counted the same.

"Historically all that's being monitored is the mass of the particles, not what they actually are," says Harris.

Because of limitations in both detection technology and academic interest, Harris says, particles have been measured in just two basic units, each one based solely on size.

"We've measured PM (particulate matter) 2.5 microns and PM 10 microns," he explains.

"That's because the PM 2.5 was small enough to get into the inner lungs and the PM 10s were small enough to be inhaled, but tended to get trapped in the nasal passages."

Thus, while it was known that these particles could invade the body, and therefore should be counted among smog's components, little thought was given to what they actually were.

But far from being a uniform mass of tiny air litter, the particle component of smog presents a cacophony of liquid and solid materials that shift and mutate in preposterously complex ways as they float in and react with the aforementioned chemical soup.

More importantly, as they bump and pinwheel through the smoggy atmosphere, they pick up a host of organic chemicals and poisons, in varieties that may well defy description, and deposit them in our pulmonary passages.

"I think of them as the garbage cans of the atmosphere," says Brook of the particles.

"A huge majority of the materials that we emit into the atmosphere, some portion of it ends up on a particle."

Thus, finding out where the particles come from, how they form and what they may carry has become the main preoccupation of atmospheric chemistry.

And of these questions, the one about where they come from is being addressed with world-leading ingenuity inside the University of Toronto's Wallberg building at St. George and College Sts.

Greg Evans is fingerprinting particles.

Using a laser contraption that he and his science and engineering department team built, the chemical engineer is blasting particles to smithereens and collecting their unique molecular signatures.

"We're trying to analyze particles one at a time," says Evans.

"Rather than look at billions of them on a piece of filter paper and trying to figure out where they came from, we're looking at each one individually, because that particle only came from one place."

Tracing the particle's origins — "back calculating where they came from" — is the main focus of Evans' cutting-edge work.

And much like DNA fingerprinting in forensic investigations, pollution fingerprinting may well trace particles back to their place of origin through a comparison of telltale chemical signatures.

In the case of particulate matter, Evans is creating a large signature base using the chemical profile each particle makes when it's vaporized by his laser and sent whizzing, at bullet speed, through a mass spectrometer array.

"When the particle is vaporized, the fragments that come off go down the mass spectrometer and give a fingerprint of the chemical composition of that particle," Evans explains.

Over time, Evans will collect hundreds of particulate signatures — "markers" — in his lab, which uses particles sucked in from a rooftop collection array facing nearby College St. W.

And by looking at the prevailing winds and air current patterns in place on the day the particle in question was captured, Evans can often assign it a place of origin.

Indeed, several years ago, his lab traced particles all the way back to Africa.

"That was one of the more unusual ones," Evans says.

"We see a lot of particles that have a composition of sand, but there was a spike on one particular day — an usually large amount on that particular day."

Using meteorological information, Evans was able to "back trace" the sand to leafy Central America, a "puzzling" source for a heavy load of such desert fare.

"It wasn't until a few weeks later that one of the people in our research group was looking at some satellite data showing there had been a dust storm over the Sahara," he says.

"And some have that sand had crossed the Atlantic and arrived over Central America and was redirected here."

Evans hopes to take a moveable version of his fingerprinting machine on the road, to generate signatures of various particles at their very source.

Given sufficient time and research, Evans hopes to amass enough particle fingerprints to identify culprit sources during bad smog days.

By comparing the chemical signature of a particle captured in downtown Toronto, for example, to a bank of known fingerprints, officials may well be able to pinpoint its precise source — perhaps even down to an individual factory.

The ability to identify sources, to tease this information out of the atmospheric mixing bowl, might allow authorities to target specific industries, or even individual polluters, when the smog gets thick, Evans says.

Unfortunately, the sleuthing won't all be as easy as the African dust storm.

While some particles are simple — they can be specks of dust, bits of smoke or pieces of worn tire rubber — others are enormously complex.

The simple ones, known as primary particles, have obvious, if diverse, sources.

"These are the things that are particles to start with," Evans says.

"So you can get them from a jack hammer on the street, pounding away, or pieces of abrasion from a tire or from the brakes on a streetcar."

The others, known as secondary particles, tend to be smaller than their primary counterparts and are formed from polluting gases like sulphates and nitrates that grow sluggish as they react with other airborne molecules.

Heavier and slower, these growing chemicals collapse out of the gaseous state to form clumps of liquid or crystals that float and mix in the air.

But they live a life of amazing metamorphosis, Evans says.

Secondary particles can grow, shrink or mutate in a million ways, depending on weather conditions, time of day, their original chemistry or the substances they encounter along the way.

In order to trace these particles back to a source industry or location, you have to know what transformations they have likely undergone.

To do this, Evans says, the particles will have to be followed from their sources, using various detection devices, to see what types of transformations they undergo along the way.

"Because what the particle looks like when it gets to Toronto will be different from what it looked like when it started out."

Apart from shifting their shapes and chemistry, particles also act like magnets for other pollutants.

These "garbage cans" can incorporate toxic chemicals right into their structure, or simply pick up things like pesticides and take them along for a ride.

Using a host of measuring devices, Evans says scientists are finding "a slew" of chemicals coating the airborne particles, which present a relatively huge surface amid the breezes for substances to glom on to.

"The complexity of that (coating) layer is immense," says Harris.

"It's impossible to even put a number on the compounds that are likely to be there, but it's in the hundreds."

It is the identities of these hitchhiking substances, as well as the complex particles themselves, that has many in the medical world panting for more information.

Evans says any negative health effects the particles can cause might simply be due to their ability to get into breathing passages, irrespective of what they are or may carry.

He says the mere fact that they can get into and irritate the lungs in large numbers may be behind some of smog's harmful health properties.

"The relationship between the composition of the particles or components that may be on the particles and the observed health effects is very much up in the air," Evans says.

"But the hope is there that we can see which particles or which components of particles are causing greater or lesser health effects."

By identifying the specific chemistry of various particles and their hitchhiking loads, scientists hope to arm medical researchers with a new menu of substances to study and test.

That's certainly the hope of Ted Boadway at the OMA.

"It only makes sense to go after the ones (chemicals) that you can get the most from first," he says.

"So if you can find something that's peculiarly toxic, you're going to want to go after that. You take your most toxic things and go for them."

Boadway stresses that any kind of medically backed regulatory controls of specific particle producers are still years away from being implemented.

"You have to know what's there first," he says. "And they (atmospheric scientists) are providing some of the basic steps for the next part of the research. What they're doing is absolutely fundamental to what will follow."

Once medical researchers get their hands on the new particle menu, they may well be able to influence government and industry regulators in the fight against smog, Harris says.

For example, if scientists can identify specific harmful particles and source them to industries or even specific factories, regulators may be able to selectively target certain sectors on days when the air gets bad.

"At the moment we have no way of knowing whether particles from one place are more of a hazard than particles from another place," Evans says.

"What we hope is that this research will help us figure out where we put the resources so we can regulate and take steps to clean up the air more effectively."

Brook agrees.

"If we know quite a bit about their size and what they're made of, then we have a much better chance of tracing the particles back to where they came from," he says.

"And that allows us to then develop strategies to reduce their concentrations."

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