(inhaling) NARRATOR: We take a breath every three seconds.

That's 28,000 breaths every day.

(inhaling) NARRATOR: But in major cities around the world, it's getting harder to breathe.

BARBARA MAHER: 30, 47, 53... MAHER: Anybody can breathe in that plume.

You can smell the metallic tang.

NARRATOR: Even where air looks clean, there's an invisible threat.

MATTHEW BEAUDRY: I had to go to the hospital 18 times?

NARRATOR: Air pollution is a global crisis.

Scientists are on the case.

CHRISTOPHER CARLSTEN: Picture yourself being brought to Beijing for two hours.

NARRATOR: They're discovering that air pollution affects us in ways we never imagined.

Your brain actually shrinks in response to urban air pollution.

GREG EVANS: We should know what we're breathing.

Just 'cause we can't see it doesn't mean it's not there.

NARRATOR: There's something in the air.

Air pollution affects 90% of the world's population.

China and India are the two countries suffering the most from smog.

Billions of people live in cities that are permanently unhealthy.

Air pollution is part of their everyday life.

JEFFREY GETTLEMAN: So, I just moved to New Delhi in August.

We find India very interesting-- there are reasons that draw lots of people from around the world to this place we're sitting right now.

I was surprised how bad the air quality is in India.

I had heard stories, I had done research, I had talked to pediatricians, because I live here with my family, two young boys.

And we knew that India has an air pollution problem.

But it's been much worse and affected our lives more than I had anticipated.

And the worst part is, you can smell it and you can taste it, and it, it leaves this chemical taste on your tongue and it stings your eyes.

And I didn't expect that.

I thought it was more of a long-term health problem, but it's actually something you feel, like, the moment that this bad air blows in.

So, we stay inside a lot.

We wear masks when we go outside on heavily polluted days.

We have an air filter in our car.

We have air filters in every room of this apartment.

And we just spend so much time inside.

NARRATOR: 3,000 people die from air pollution every day in India.

In one middle school in New Delhi, half the students tested had permanent lung damage.

Doctors on the front lines see it firsthand.

(talking in background) ARVIND KUMAR: The things here are only getting from bad to worse.

I've been doing this chest surgery since 1987.

When I started, mostly, you would see pink lungs, and when you handled smokers, you would see grayish, blackish lungs.

But over the last 30 years, the scene has changed dramatically, to the extent that today, it's a rarity for me to see pink lungs.

And very sadly, we are seeing younger and younger patients with lung cancer.

Last one year, the average air quality in Delhi has been equal to about 20 to 25 cigarettes a day.

NARRATOR: Breathing air that is like starting a pack-a-day smoking habit from the day you are born is leading to some alarming consequences.

KUMAR: And I was speaking to one of my colleagues from a cancer hospital in Mumbai day before yesterday, and he told me the youngest he has seen is an 18-year-old boy.

A non-smoker 18-year-old boy with lung cancer.

Truly, there is no non-smoker in India.

So that's something which everyone in the city, from smallest baby to the oldest person, from the poorest person to the president, prime minister-- everybody is inhaling.

You know, air is a big equalizer.

(car horns honking) GETTLEMAN: I did some work on this as a journalist, and I met with people close to the prime minister, and they just gave me the impression that they did not consider air pollution to be a top priority.

There's very little outrage here about how bad the air quality is.

People just say "Oh, it's the fog, "it's," you know, "the way things are, it's the price we have to pay for a growing economy."

This is a wonderful country full of warm people.

We've had an amazing arrival and experience here.

I'm here for just a few years.

But I have more concern for the people who live here for their entire lives and are breathing polluted air day in and day out, and what type of effect that's going to have.

KUMAR: So, I guess that in coming years, we are going to see lung cancer in people in our country in 20s and 30s and in increasing numbers in non-smokers.

It's an explosion waiting to happen.

I know it's coming.

NARRATOR: We have created a growing health crisis.

Over 90% of the world's population lives in places where air pollution is above what the World Health Organization has identified as a safe air guideline.

So it's a hazard, it's a risk that really, almost everybody faces.

In some parts of the world, in China and India, the profile of, of air pollution has really gone up quite a lot.

(car horns honking) NARRATOR: In China, awareness of the hazards of air pollution is high.

Jan Boquillard is one of many who are working on solutions.

BOQUILLARD: I started a start-up about two years and a half ago called AirVisual, and now we're actually part of a bigger group called IQAir.

So our focus is really to bring air-quality data to the world.

And really, the goal of starting that business was actually quite selfish, it was really for making sure my children were going to breathe clean air.

In Beijing, this year has been actually very good, I mean, comparatively to previous years.

Lots of people are actually using electrical bikes, like myself, or e-scooters.

All of the power plants using coal around Beijing are now closed.

Factories who used to pollute have been moved out further away from Beijing.

We really feel the improvement of the air quality because of those efforts from the government.

NARRATOR: Air pollution is a global problem.

Even cities where the air looks clean shouldn't be complacent.

♪ ♪ We have amazing blue skies in Canada, and it's sort of, like, if the sky wasn't blue, it'd be un-Canadian.

We have good air quality, and we just can't see the pollutants that are impacting us.

NARRATOR: What we can't see can hurt us.

Air pollution kills more people across North America than traffic accidents.

Dr. Greg Evans has spent decades researching air pollution.

EVANS: Air pollution is a complex mixture of all sorts of different chemicals.

They can be in the gas phase, they can be in the particle phase.

NARRATOR: The real concern is fine particles in the air.

Most of those tiny, nearly weightless particles are leftover bits of fossil fuel that didn't burn.

EVANS: They're so small that you generally can't see them, but there's a large number of them.

So, we're in a very clean room at the moment, but each time you breathe, you're going to be inhaling about five million particles.

Outside, just on the other side of that window, it would be about 20 million particles every time you breathe.

NARRATOR: What are we breathing when we take in a lungful of air?

Anything that is in the environment.

Gases, pollen, dust, and unburnt by-products of combustion are swirling around us all the time.

EVANS: So, we've spent a lot of time with instruments, such as the one beside me here, which was one of the very first ones in the world that studied individual particles.

(car horn honks) NARRATOR: In the city, a lot of those particles come from cars.

You can't study traffic in a lab-- you have to go where the pollution is.

So Dr. Evans and his team built a mobile laboratory that could roam the city.

EVANS: One of the most surprising is how much variability there really is across the city.

The variation inside a city is much larger than the variation between cities, because people are doing all sorts of different things.

NARRATOR: The city is a patchwork of good and bad air quality.

How can there be that much difference?

Marianne Hatzopolou's job is to find out why.

HATZOPOLOU: I study traffic-related air pollution.

So I look at how emissions are generated from vehicles as they move along the roads, and what kind of urban microenvironments trap air pollutants and where the hot spots are in urban areas.

(laughing): My commute?

It's green.

It involves a lot of walking, which is, you know, one of the best ways.

I would not drive.

Not in Toronto, uh, it...

It doesn't work with what I do, what I believe in.

♪ ♪ NARRATOR: There's a new tool in the kit for detecting hot spots-- portable, hand-held monitors.

HATZOPOLOU: Advances in these portable monitors has led us now to the development of very, very, very small instruments, and this has really revolutionized the, the area of air pollution altogether.

NARRATOR: Now we can measure the air quality in places where even a mobile lab can't go.

HATZOPOLOU: Almost every year, I run a large campaign where I have teams of students, research assistants, equipped with personal exposure monitors walking around the city.

The idea is to collect data on air pollution, but to better understand what are the factors determining high levels of air pollution.

With big advances in air pollution technology, we can measure much finer particles, which we normally refer to as ultra-fine particles, and these are really, really fine particles.

NARRATOR: Laura and Junshi are two of Marianne's foot soldiers.

They sample the air for ultra-fine particles in different locations around the city.

Because they are so small and so fine, from a weight point of view, they, they mean nothing.

The weight doesn't give you an idea of how many there are.

So that's why we actually count them.

NARRATOR: First, they take measurements on the University of Toronto campus.

This leafy, quiet part of the campus gets a good reading.

LAURA: Around here, it's 13,000, 14,000 particles per cubic centimeters-- it's very low.

It's an open area and there's not too much traffic.

NARRATOR: Their next stop is an underpass next to a major freeway.

LAURA: Two times higher than what we had on King's Circle.

NARRATOR: Walking past a construction zone, dust and diesel trucks cause a spike in their readings.

JUNSHI: For this one, it's, like, six times higher than the normal.

LAURA: It was five times as high as what we had next to the campus.

NARRATOR: Laura and Junshi head to a walkway designed for pedestrians.

The results are eye-opening.

LAURA: It's five times higher than what we had on campus, and three or four times higher than what we had next to the Gardiner.

NARRATOR: There's a covered walkway right next to the open sidewalk, where the pollution levels are much lower.

LAURA: Outside it was almost 100,000 particles, so it's a lot lower here inside.

NARRATOR: Some people take the cleaner route, but most see the sidewalk as easier.

Next to a tall building, Laura and Junshi find the worst spot of all.

The air looks fine.

It isn't.

Just now, it's, like, 20 or 30 times higher.

HATZOPOLOU: What happens is, it's called the urban canyon effect.

So depending on the side of the road you're walking on, you could be breathing very different levels of air pollutants.

So you could be in a street that is really narrow.

It could have half the amount of traffic than the highway, but twice the amount of air pollution, just because you are in an urban environment that is more prone to trapping air pollution and leaving it very close to the street.

When we see these sort of concentrations in a city like Toronto, you're thinking "Wow, there are huge hot spots," and some people can be exposed to concentrations as if they're actually living their life in China.

♪ ♪ NARRATOR: The effects of polluted air are long-term.

But for some, bad air can have an immediate effect.

For nine-year-old Matthew Beaudry, the great outdoors can have a hidden danger.

MATTHEW: I love the outdoors, and I love being active and running around.

The problem is, if I run around too long, my asthma starts to act up.

TRACEY BEAUDRY: It all began when he was very, very young, a few months old, and he developed a cold and then couldn't breathe.

NARRATOR: Matthew was born in Mississauga, a large and bustling suburb of Toronto.

MIKE BEAUDRY: Every smog day, we had to keep him inside.

Every time they did construction on the main roads and tarred the roads or paved them, we had to keep him inside.

Cars run, buses run.

They're out on the roads all the time.

TRACEY: Not a whole lot of freedom to be able to go out and enjoy the outdoors, which is exactly what Matthew wants.

He was absent his first year of school, 67 days of school that year.

NARRATOR: Matthew's asthma isn't uncommon.

Come on, Mom.

Remember, don't let it wheeze.

NARRATOR: Asthma is one of the leading causes of hospital admission for kids.

One year, I had to go to the hospital 18 times?

NARRATOR: Matthew couldn't breathe.

For his sake, Mike and Tracey had to make the heartbreaking choice to leave their home and move to a smaller city with cleaner air.

TRACEY: We kind of uprooted and left my childhood, neighbors that I've known my entire life.

TRACEY: But I'm a mom.

He loves the outdoors.

He is very active.

We have been given an amazing opportunity up here to allow him to be a child.

MATTHEW: I'm a very athletic kid.

I like pretty much every sport.

TRACEY: It was the best decision for, I think, us and for our family and for him.

NARRATOR: People like Matthew are the canaries in the coal mine.

What harms them harms us all.

We inhale millions of particles of air pollution with every breath.

What you breathe affects your whole body.

When we're understanding how air pollution, uh, affects our health, it, it seems as though the entire body is, is potentially at risk.

So what happens is, we inhale, especially these very, very small particles, ultra-fine particles.

That leads to an inflammatory response in our lungs.

And everybody can appreciate that your lungs would be affected from air pollution, but that inflammation seems to spill over into the rest of your body, and affects all kinds of other organ systems.

KUMAR: Smoke affects every age and every organ in the body.

So lung is the first port of entry.

Maximum damage is taken by lungs.

Your lungs do not develop to optimum capacity, because all this toxin which is deposited in the lung, it causes fibrosis.

Normally, the lungs are balloons-like, you know?

They have to have an elasticity.

But if you have things deposited in the wall, it reduces the elasticity, so it reduces the size of your lungs, so you do not develop your lungs to your optimal capacity.

And you have now increasing recognition of ultra-fine particles, which actually pass through the pores in the lungs and then they circulate in the blood.

And these particles not only have silica, but they also have a lot of chemicals absorbed on their surface.

So they're carriers of chemicals, and that chemical is then released in the blood and it reaches every organ.

So there is no age which is exempt, there is no sex which is exempt, there is no organ in the body.

So it's going to create havoc, as far as our future is concerned.

NARRATOR: How long does it take before polluted air affects our bodies?

Not very long.

Okay, so everything is going smoothly here?

NARRATOR: To find out how, the University of British Columbia has gone to great lengths to make some of the worst air in the world.

So, so our lab really specializes in controlled human exposures.

They are exposed to, in this case, diesel exhaust at a precise level that we control.

So, the controlled exposure typically is two hours.

This is where the exhaust of the engine is going... NARRATOR: This kind of research is tricky, because volunteers are being exposed to something potentially dangerous.

The study has been carefully designed to limit the risk to their health.

Around the wall here, and just go down over there, where the subject is exposed for two hours.

CARLSTEN: We're able to say, picture yourself being brought to Beijing for two hours.

After those two hours, you'll, you'll be removed back to your normal environment.

When people think about that, it, I think, does fairly and, and understandably put it in a different light, where it's not quite as intimidating.

So I think that is stable enough that this is a solid, valid exposure.

NARRATOR: The volunteers were exposed to dirty air and to clean air on different days.

Keep going, keep going, keep going... CARLSTEN: What we've done with that study is, we've looked at the blood and the brain to see if there are any changes.

NARRATOR: Even a short exposure to polluted air had a shocking effect: air pollution changed the volunteers' DNA.

CARLSTEN: Our DNA, rather than being this static molecule, it's constantly changing with these chemicals that come on and off of it.

NARRATOR: We now know our genes can be switched on or off.

Those changes are called epigenetics.

CARLSTEN: It was really just the days of air pollution that led to certain epigenetic changes.

Not only that, but we were able to show, when the individuals came back on a later date, that those epigenetic changes had disappeared.

These are transient or temporary changes, which is good news, because it means that if we can limit exposures, that they are more likely to not be permanent.

It also begs the question of, if we don't limit exposures-- if you're living, for example, in a place where high levels of air pollution are more common and permanent-- you could be in more trouble for those epigenetic changes becoming longstanding.

It does seem that the deeper we look, the more we find.

NARRATOR: It's not just us.

Bad air affects everything that breathes.

And that includes our closest companions, dogs.

In the late 1990s, veterinarians in Mexico City found themselves treating dogs with unusual symptoms-- confusion, disorientation.

Some didn't even recognize their owners.

It seemed like these dogs were developing a very human disease-- dementia.

When the researchers in Mexico City looked at brain samples from affected dogs, they found something very strange: lesions.

Damaged tissue in the dogs' brains and noses.

They looked a lot like the lesions found in the brains of humans suffering from dementia.

When researchers looked at human brain samples from Mexico City, they discovered something extraordinary: the same lesions, even in the brains of young people, including children.

Usually, older people get dementia, not children or dogs.

There is a way to confirm dementia: measuring iron in the brain.

The team sent their brain samples to Dr. Barbara Maher, an expert in measuring metal in incredibly small particles.

Our brains naturally make tiny, magnetic bits of iron called magnetite.

As we get older, we accumulate more iron in our brains.

Too much iron, however, is a hallmark of dementia.

MAHER: It's been known for a long time that the amount of iron in Alzheimer's brains is greater than in non-Alzheimer's brains.

NARRATOR: Dr. Maher compared the brains from Mexico City with samples from the city of Manchester, England.

MAHER: We made magnetic measurements of these frontal cortex samples from the Manchester brains and from the Mexico City brains.

NARRATOR: As expected, the older patients from Manchester had higher levels of magnetic particles.

But it was the samples from young people in Mexico City that were most surprising.

MAHER: Even some of the young Mexico City cases have even higher magnetic content.

NARRATOR: With these new clues about a link to dementia, Barbara brought in David Allsop, who heads the dementia research lab at Lancaster University.

ALLSOP: Barbara came to me and showed me these papers, where they'd found people in Mexico City-- which is obviously a highly polluted environment-- and they'd seen early changes associated with Alzheimer's in the brains of very young people.

So, the highest magnetic content that we measured was actually from a Mexico City resident who was only aged 32.

Even a three-year-old child has quite significantly measurable amounts of magnetite in their brain.

Barbara had made the connection that some of the metals in the brain might be coming from external pollution, rather than being made in the brain itself.

NARRATOR: Barbara Maher took a closer look at the particles.

MAHER: We made thin tissue sections to look with a very highly resolved transmission electron microscope at the particles in, in those brain cells.

NARRATOR: There were two different shapes of particles.

MAHER: Those magnetite crystals, they're beautifully crystalline.

They're very regular and geometric.

And then there are these rounded-- they're called spherules or nanospheres.

They're rounded because they're originally molten droplets.

NARRATOR: And they're not supposed to be there.

Dr. Maher had recently been measuring roadside pollution-- in particular, ultra-fine particles from vehicle exhaust.

The rounded particles in the Mexico City brains looked the same.

MAHER: So that's, that's a brain cell from one of our Mexican City cases, and the obvious dark, rounded particle is one of these externally sourced pollution magnetites.

For every one of the biological magnetites, we see of the order of 100 of the externally sourced magnetic particles.

ALLSOP: And lo and behold, we found these tiny little particles that look virtually identical to those that you see in airborne pollution.

It's not definitively proven, but it certainly looks very suggestive that they might be coming from environmental pollution.

NARRATOR: But how could air pollution be getting into our brains?

MAHER: Anybody can go down and stand at a busy roadside and... (sniffs deeply) Breathe in that plume of pollution that you're being exposed to.

And, of course, you can actually smell it, you can smell the metallic tang as you're standing there.

And, of course, the reason you can smell that is that some of those particles, they're being sensed by your olfactory nerves.

So when you breathe in, these particles are small enough to actually travel through the nerve cells, and when they do that, they're able to gain direct entry into the brain, because where the olfactory bulb adjoins the frontal cortex, unfortunately, there is no blood-brain barrier at that point.

NARRATOR: Our body protects our brain with the blood-brain barrier.

Even elements in our bloodstream cannot get directly into the brain.

But these particles are so small, they can bypass the blood-brain barrier through the nerves in our noses.

Now the Mexico City dogs made sense.

Where humans have thousands of olfactory nerves, dogs have millions.

ALLSOP: Magnetite is made out of iron, but we found other particles in the brain made out of other fairly exotic metals, like platinum, that you wouldn't normally find in the brain, which adds to the story that they must be coming from an external source.

NARRATOR: David and Barbara released their paper in 2016.

ALLSOP: When the paper came out, it caused a huge amount of publicity.

People were contacting us from all over the globe wanting to know more about what we'd found.

Because it looks as though, for the first time, we've found these particles in the brain that looks as though they must come from a, an external environmental source.

I mean, we can only speculate about the possible relationship with things like Alzheimer's, and possibly other brain diseases, as well.

It's very difficult to prove!

(laughing) But there are some interesting, um, observations.

There's this study in Canada where they found there's a higher risk of developing dementia if you live within 50 meters of a major road.

So that's highly suggestive.

♪ ♪ NARRATOR: That study included six million Ontario residents.

The closer someone lived to a major road, the higher the chance of dementia.

If you live within 50 meters of a major road, your chances of dementia go up by seven percent.

EVANS: What we found is that the levels of air pollution from a roadway takes about 250 to 300 meters before it drops off enough to be equivalent to the roadway not being there.

♪ ♪ NARRATOR: In cities around the world, researchers are finding similar results.

One of these studies was in Los Angeles.

CALEB FINCH: The women in our study whose residence exposed them to above the E.P.A.

standard had nearly a double risk of dementia.

NARRATOR: The more air pollution you breathe, the faster your brain ages.

The brain actually shrinks in response to urban air pollution.

The total environmental exposure might account for, I think the working figure is ten percent of excess Alzheimer cases in the United States.

Even in Canada, where our air is not that polluted, what we're finding is that there really is no safe level.

There's no level of air pollution which we're not able to detect some effect on, on the entire population.

CARLSTEN: With just little increases in particulate matter in the environment, the increase in health risk associated with them goes up dramatically.

It's like tobacco smoke-- there's no such thing as a safe background level of tobacco smoke.

It is all toxic.

(grunts): Wasn't ready.

Now I have to catch... NARRATOR: Studying air pollution isn't child's play, but in this case, it can be.

Let's practice a little bit, and then we can do it.

NARRATOR: Dr. Rima Habre is part of a team conducting a long-term study that's been running at the University of Southern California.

And go!

HABRE: The children's health study is one of the longest-running pediatric cohorts, um, in the U.S., definitely-- I think globally, as well.

It started in 1992.

It's now recruited over 12,000 children from 16 different southern California communities.

Oh, look at this cool one!

Ooh!

HABRE: This study has really provided a lot of scientific evidence to show how air pollution exposure is very tightly related to kids' health in general.

NARRATOR: Los Angeles used to be famous for its smog.

Over the years, the air in the city has improved radically.

HABRE: You know, as these levels went down, there were actual improvements in outcomes in these kids.

(exhales deeply) HABRE: So their lung function improved, you know, asthma symptoms improved just across the board.

NARRATOR: The children's health study also showed that where children lived made a big difference in their health.

Like other studies, it was clear that exposure came down to location, location, location.

HABRE: Kids who live near busy roadways had higher asthma.

Kids who lived in communities with more air pollution suffered more lung damage, or had more lung damage, and once they moved to cleaner communities, they regained some of their lung function.

NARRATOR: Collecting data around Los Angeles came up with some surprising results.

Sometimes, air pollution can come from unexpected directions.

A plane just passed us over, and the levels are climbing up still to 50,000 particle number.

As the planes are going in and taking off, they're emitting these ultra-fine particles.

Because of the typical meteorological conditions in Los Angeles, where the wind is usually blowing from the west in a steady fashion, there is this really pronounced plume of ultra-fine particles downwind that covers most of the communities within L.A.-- sort of the Inglewood area.

It's a very densely populated area.

The more you learn, I think, the more it becomes apparent there are a lot more mysteries.

NARRATOR: Ultra-fine particles are the latest mystery.

HABRE: The ultra-fine particles, especially, they're so tiny that they can quickly cross from the alveoli into the blood circulation through the lungs, basically.

And they are very good at transporting, you know, what we think are bad actors-- things like poly aromatic hydrocarbons, or, or metals-- very deep into the lungs, as well.

So this is the area that we know the least about right now, and all the research is really going there and trying to see, you know, what is it about the ultra-fine particles that's so worrisome.

NARRATOR: If air pollution can get into the bloodstream, it can get into the womb.

A new phase of the study is now tracking pollution exposure at the earliest stage possible.

The inlet, as you can see, is very close to her breathing zone.

HABRE: We are actually doing some personal monitoring or measurements of the pregnancy period, so, while the kid is in utero, and then following them up, you know, up to age five.

BRAUER: Women who are exposed to air pollution during pregnancy are more likely to deliver babies of lower birth weight, and some suggestions also of, more likely to deliver prematurely.

Low-birth-weight babies or prematurely born babies are at risk for a whole number of diseases throughout their lifetime.

So I do think it's a very interesting time for how people perceive air pollution and air quality.

There's a massive explosion now of kind of air pollution measurements anywhere you look.

NARRATOR: Volunteers using portable monitors are now collecting data in cities around the world.

♪ ♪ One of those volunteers is Jeannie Higgens in London.

London, England, is a cautionary tale.

Ten years ago, diesel seemed like the answer to out-of-control greenhouse gas emissions.

The result?

An air pollution crisis.

9,000 Londoners die prematurely because of air pollution every year.

800 schools and nurseries, with tens of thousands of children, are being exposed to illegal levels of air pollution.

Nowhere in London is the air within safe levels.

Central London has twice the safe level of particulates in the air.

HIGGENS: I can tell if the air's better or worse when I go out.

When it's, like, quite hazy, you can almost see the pollution in the air.

Yeah, you can feel it.

NARRATOR: Jeannie feels the effects of polluted air more than most people.

A wide-ranging study in London is using volunteers like Jeannie to track where and how air pollution affects us.

JENNIFER QUINT: So, our role in the study has been to recruit patients who have C.O.P.D.

C.O.P.D.

is a blanket term that stands for chronic obstructive pulmonary disease.

And really, it's an umbrella term that covers a whole spectrum of disease.

They're all linked by, by difficulty breathing.

We give them a pollution monitor and ask them to carry that monitor around with them when they go out for a six-month time period as a maximum.

NARRATOR: Researchers at King's College are using data from the study as part of an overall air pollution strategy.

SEAN BEEVERS: It's important to make estimates of people's exposure and to assign that to particular sources.

And then from there, you can actually develop policies.

We've developed an air pollution exposure model that predicts individual exposure as people travel around the city.

And it represents the sort of seven million people in London.

(siren blaring) NARRATOR: Jeannie is just one of those data points, adding to the big picture and a search for solutions.

♪ ♪ HIGGENS: Because I'm so used to being breathless, I forget that I am breathless.

It's not as if... (gasps): "Oh, dear, I can't breathe!"

(coughing) Now, there...

Sorry, I sort of got a whiff of... Traffic fumes.

I think it's about a four-minute walk from my house to the Tube station, which is including crossing the A4.

I live really, really close, yes.

C.O.P.D.

is just a name for a condition of life.

It's not something in a small box.

You've got that.

♪ ♪ You're not doing enough to look after your lungs.

So the, the diagnosis gives you a whole area in life now to look at.

♪ ♪ NARRATOR: The new wave of research around the world is creating awareness in the general public.

More people are concerned about the air they breathe than ever before.

(kids squealing) NARRATOR: Toronto resident Keith Brooks is one of them.

BROOKS: I'm a lifelong environmentalist, and then also, it's an issue that I care about personally, because this is me, where I live, and, and it's my children and my health and our health.

Their little lungs are being exposed to this on a daily basis, so, yeah, we want to know what we're being exposed to.

NARRATOR: Using one of University of Toronto's air monitors, Keith has agreed to play guinea pig.

BROOKS: Bike usually goes faster than the cars do.

I don't have to pay for gas, and I don't have to worry about parking, right?

We're looking here at the exposure of our cyclist, Keith, to ultra-fine particles.

So, you can see that on Dundas, the levels are fairly low, probably a combination of, you know, wider street, more ventilation.

Still maybe a little bit too early in the morning for vehicles to start accumulating, to get gridlock.

As Keith was getting closer to the downtown area, his exposure became much higher.

By the time he's getting into downtown, it's really rush hour, so it's polluted, because everything is polluted downtown during rush hour.

NARRATOR: Keith's route includes a large park.

We would expect a park to have cleaner air, but that's not always the case.

HATZOPOULOU: Urban parks are great, because we need to have green space in urban areas, but a lot of them happen to be along, bordered by major roads.

And so the concentrations are not very low within these urban parks.

NARRATOR: When even parks are affected, air pollution seems inescapable.

Is there anything we can do to protect ourselves?

♪ ♪ There's no mystery to solving the air pollution problem-- we need to stop burning fossil fuels.

In a carbon-based economy, that's not going to happen overnight.

But there are changes we can make.

BRAUER: It's not like we still have to search for the cure.

We know how to solve this problem, because we've actually come a long way throughout North America and Western Europe.

Ultimately, what we'd like to do is actually get away from a carbon-driven economy.

We're unfortunately going to live with internal-combustion engines for many, many years to come.

KUMAR: You can have the most expensive water bottle in your pocket, but you can not have more expensive air for you carried around you.

You have to breathe the ambient air.

Nowhere in the world has government alone been able to solve this problem.

Without people's participation, this problem cannot be solved.

First, they have to know that there is a problem.

Second, they have to accept that this problem cannot be solved without each one of us taking a little bit of inconvenience to solve it.

We have to move to cleaner, greener sources of energy.

Otherwise, if we continue to spread like this the way we are, the future is doomed.

NARRATOR: One way to protect ourselves is masks.

But do they really work?

BRAUER: Masks and filters are increasingly common.

If you've ever worn a mask for more than an hour, you know it's really uncomfortable.

So even though we do see people increasingly using them, I just don't think it's a practical solution for the general population.

Having said all that, if they are worn correctly, they do filter out the particles that we're most concerned with.

Filters on the other hand, these, these small room air cleaners, they work quite well.

If you place that in your bedroom you could sleep for eight hours actually in a situation where you've reduced the pollution by perhaps 60%.

So our idea is that people should have access to information on air quality.

We should know what we're breathing.

Just because we can't see it doesn't mean it's not there.

And if people had this information, they would be much more interested and engaged, because most simply don't realize what they're being exposed to or how they're contributing to the, the problem.

NARRATOR: Biking with an air monitor gave Keith some valuable information about his daily commute.

So how can he improve on it?

By turning to technology with the Clean Ride Mapper.

HATZOPOULOU: The bike mapper was started as an initiative to really just disseminate research.

We thought, "Okay, we could do something that is useful "for individuals who want to plan their routes, "especially cyclists, or even pedestrians or runners, who are trying to look at low-exposure routes."

What he did a little later, which is really interesting, he decided to take an alternative route, to go again from the same origin to the same destination.

Now, what I did is, I actually computed his average exposure along his morning route.

And I found that on average, across the entire route, he was exposed to about 34,000 particles per cubic centimeters.

And then I computed the average along the alternative route, which is a combination of starting your trip a little bit later and taking some alternative roads.

And on average, his exposure was 11,000.

That's a reduction of over 66% in his exposure.

BROOKS: A 66% reduction, eh?

That's significant, especially if you bike every day, both ways.

NARRATOR: Getting people out of cars is key to reducing pollution.

But with all the traffic still on the road, are cyclists damaging their health?

CARLSTEN: I live in the North Shore, and I ride my bike.

I think that's nice for both mental health and probably my fitness.

The biking question continues to be a hot one in the air pollution community.

And one thing does seem clear, that on balance, the health benefits of cycling outweigh the risks.

So that's a really important message, because there's a lot of science about it.

BRAUER: So, I ride a bike.

Doesn't have a whole lot to do with my air pollution exposure.

I do it mostly for the physical activity.

(chuckling): And for my own sanity.

I find it a very unstressful way to get to work.

What makes things worse for cyclists is, they're breathing two to three times the resting rate.

So two to three times more air than you would be when you're sitting in a car.

But putting it all together, the physical-activity benefits from cycling really dramatically outweigh the negative impacts of air quality.

No matter what you do, and no matter how high the level of pollution is, physical activity is still good for you, even if you're getting physical activity in polluted air.

Having said that, people should not have to make that choice.

BROOKS: I ride my bike because it's the fastest way to get around.

It's the easiest way to get around.

I ride my bike because I think it's good for my health, and also, it's good for the environment.

So I'm really glad to hear that there's not a trade-off between my health and what's good for the planet.

NARRATOR: Once you understand air quality, it empowers you to make changes-- even small ones-- that can have a big impact.

I see a lot at daycares, people sometimes, in the winter, especially, would park in a parking lot and leave the car idling, go in, pick up their kids, and come back.

And wintertime, with an idling car, that creates a lot of emissions.

MIKE: It's the little things.

Like running the buses right where the kids are getting on, the exhaust pipe is right at most kids' chest or head level.

MIKE: Why would you do that?

Just turn them off-- it doesn't take much.

But we wouldn't have given that a second thought had Matthew not been, been asthmatic.

TRACEY: I had to force them to shut the buses off to be parked there.

That's a huge trigger, is exhaust fumes.

MIKE: And a lot of communities are starting to institute the idle-free zones.

♪ ♪ NARRATOR: The more information we have, the more we can do to protect ourselves.

♪ ♪ Portable monitors have been a boon to research, but the next step is to network them in smart cities.

♪ ♪ The Smart Cities Initiative is to basically equip people with better information about how the city is working, so they can also make better decisions regarding how they move, et cetera.

I would like to see a monitor on every corner.

I would also like to see a monitor on rental bikes.

And this is not something that is uncommon.

Other European cities are doing that.

Because suddenly now, you can have 100 or 200 monitors walking around.

If you just install them on rental bikes or on pedestrians, you start generating, you know, data throughout the entire city.

You can do this in real time, you can collect it in real time, you can generate real-time air pollution maps, and you develop, again, a more detailed, a finer understanding of air pollution.

♪ ♪ NARRATOR: Smart cities will make it easier to avoid air pollution in the future.

But right now, a little street smarts goes a long way.

♪ ♪ MAHER: Since I've done this work, my behavior has changed.

So if I walked on the downhill side of the traffic-- downhill side of the road, compared to the uphill side-- again, I'd be reducing my dose.

Because obviously, the vehicles are pumping out more particulates as they're accelerating, working hard to get up the hill.

You see the particles, they're invisible, but in your mind's eye, you see, there's particles everywhere in these busy locations.

And ideally, you take yourself away from them, so you're not having that dose, day in, day out, of, of this potentially damaging material.

♪ ♪ I could take the motorway.

I could actually go on the motorway from, you know, close to where I live.

But why would you go on the motorway when you could come on a road this quiet?

If I do have to drive in the city, you'll never find me tucked up behind somebody's exhaust pipe.

Especially at traffic lights, I'll be stopping and leaving as far as practicable a distance between me and the next car.

NARRATOR: Even on roads as busy as the infamous Los Angeles freeways, small habits can have a big effect.

Keeping your air conditioning on recirculate is much better for you.

HABRE: So we've taken the air conditioning off of the recirculate conditions.

We can see the numbers climbing.

They were at 12,000 before, and they're slowly climbing up.

We're about 25,000 right now, to 30,000, actually.

NARRATOR: How about with the window open?

HABRE: We have the windows open.

It's traffic in L.A.-- mild traffic, actually, not very dense traffic, and we're getting the ultra-fine particle exposure from outside into the car.

150,000 particles per cubic centimeter.

CARLSTEN: I don't, I don't think most people are aware that simply opening the window will lead to higher particulate matter in their car, and that that could have adverse health effects.

We have to remember that people and human nature is gonna migrate toward convenience.

If it's easier and more comfortable to roll down the window for whatever reason, people are generally gonna do that until, if and when they're sufficiently educated.

And because people don't see it, there can be a false sense of reassurance.

BROOKS: It's always better to make informed choices than uninformed choices.

So if you're in doubt about what you're being exposed to, it's better to find out.

How important is air?

(chuckling): I suppose if you're an octopus, it's not that important, but for humans and other mammals that breathe air?

It's critical.

♪ ♪ ♪ ♪ Zoot!