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>>BRYAN: I'm going to tell you a tale of air quality in three very different
cities. Beijing, China; Los Angeles, California; and
Atlanta, Georgia. And since I work for NASA, I'll be telling this from the perspective of
space. This is a satellite image
of northeastern China. And you can see this thick, thick
smog enveloping the entire area, and
including the city of Beijing, China.
And from the ground, the pollution, the smog is stifling. It's not uncommon
to see people wearing these face masks to help protect
them from the pollution. So,
what is smog? Smog is a combination of the word "smoke" and
"fog", and it's really just a catch-all for any
noxious soup of pollutants. In the case of Beijing, the primary
component is particulates coming out of the tailpipes of cars, and out of
smoke stacks. So it occurs whenever you burn fuel,
such as gasoline and coal. And the problem with these particulates is
that when we inhale them, they can go deep into our
lungs and they're toxic, and they can embed themselves into the lining of our lungs.
And the smallest of these particles can actually
enter our bloodstream. Okay, here is
an image of the Forbidden City, one of Beijing's top tourist attractions.
And this is on a clear day.
And this is on a horribly polluted day. So I'd rather be a tourist on the
clear day here. Now on the polluted day, the levels of
pollutants can be ten times greater than what's considered
hazardous, and 40 times greater than what's considered to be healthy.
Okay, now the Chinese government has
developed their own air quality index, similar to the one we have in the US.
And they developed, or they created these cartoon characters
to convey the daily air quality index to the Chinese people, and
they call these the Shanghai girls.
The Shanghai girls become increasingly distressed as the AQI goes up,
as the pollution worsens.
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[no sound] [laughter] Okay,
you wouldn't be surprised to hear that this is not an official Shanghai girl,
this is called the "Beijing girl", and she's created by a concerned Chinese
citizen. And this citizen was concerned because
these levels are above the highest level of the air quality index.
And in these situations,
this air quality is considered to be beyond index.
So, why is China so polluted?
Well, in the last several decades, they've undergone an industrial revolution
and this has been fueled by China's cheap and abundant
coal. And along with this industrialization,
there's been an increase in urbanization as well as
the standard of living. So the Chinese people are manufacturing more goods
and they're consuming more goods. But more importantly, they are exporting
many of these goods and is considered to be the world's manufacturing hub.
When you burn coal, sulfur dioxide is
released, and it's a precursor to acid rain, it's a
primary ingredient. And it also is a contributor to these particulates that
plague Chinese cities. Here's a representation of satellite data,
of sulfur dioxide, and you can see it's pretty high over much of China.
And it's highest here in this region and that region where there's
a high density of power plants.
For perspective, here is the United States, and you
can see that the pollutant levels are much, much lower.
The Ohio River Valley has the highest concentration of power plants in the
US. And it's much lower in the US because
it's required by law for these power plants to operate scrubber
technology. And these scrubbers literally scrub or remove
the SO2, the sulfur dioxide from the effluent of the power plant
before it's released to the atmosphere. The problem here is
the scrubber technology is incredibly expensive to operate. So places like
China and India simply can't afford to.
But it wasn't so long ago that pollutant levels in the US
were very high, and some of the most polluted cities in the world were in the US.
And Los Angeles was a poster child for this.
And you can see in this image, which is not a satellite image, it's actually
a photograph from NASA's Skylab space station in 1973,
you can see this thick smog in the Los Angeles basin.
The first smog event,
major smog event, occured in 1943 during World War II.
And the residents of LA initially thought they were under attack by a foreign power.
And this is because the smog was stinging their eyes,
burning their throats, and there was an odd bleach-like odor.
It smelled like chemicals.
And interestingly, they noticed during these smog events
that the rubber tires on their cars were cracking.
So, the residents of LA, they
protested to the city government. They said they wanted cleaner air.
And this is a protest by the Highland Park Optimists club.
So city officials responded by
initially banning the burning of trash, which was a common practice
at the time. And they also shuttered a few factories
that they thought were particularly polluting. But unfortunately the smog
persisted. Scientists finally figured out
that the primary ingredient in this smog
was ozone. And as
time went on, these ozone episodes just got worse. Here's an example
of 1955 and 1956,
all the days listed here had ozone levels above 500 ppb, that's
an incredible level. And on this one horrible day, September 13th,
it was as high as 900 ppb. And that's 15 times acceptable levels.
Just for reference, from personal experience,
I actually experienced 350 ppb
quite by accident in a lab one time. I was working with a chemical
instrument that generated ozone internally to the instrument, and
unknown to me, a hose cracked and was allowing this ozone to build up in the lab.
And at first my eyes were stinging, my throat was burning, and finally
when I smelled this chemical odor, this bleach-like odor, I knew it was ozone. So I took a quick
reading, and it was only 350 ppb. I can't imagine
what it would feel like to experience 500 ppb regularly, and
900 ppb for hours on end. Okay,
so, the question still remained, where was this ozone coming from?
Scientists figured out it wasn't coming from tailpipes and smoke stacks, so it
wasn't directly being emitted. Instead, it was being
generated within the smog itself.
So here, today we know that there are three primary ingredients necessary
to form these unhealthy levels of ozone in an urban environment.
The first, sunlight, that drives these chemical
reactions, that provides energy. And of course LA is in sunny California.
The second is a family of compounds called nitrogen oxides
and they are generated whenever coal and gasoline are combusted,
so it comes out of tailpipes and smoke stacks. The third
ingredient are volatile organic compounds, and they primarily come out of the tailpipes of
cars and some factories. And if you've ever smelled gasoline
or paint fumes, you've smelled VOCs, they're very common. There are literally thousands of
these in the urban environment.
Here is a representation
of satellite data, nitrogen dioxide, it's one of the nitrogen oxides.
And you can see all these red
splotches on here, they're high levels of nitrogen dioxide.
And the highest, one of the highest levels is here in Los Angeles.
And all of these occur or coincide with America's largest
cities. The most populated areas.
Okay, so scientists have figured out that
ozone was a primary ingredient in this smog, and they had a basic
understanding of how it was being generated within this smog. So initially
government officials controlled the emissions of
volatile organic compounds from cars and from factories, and the ozone levels went down.
Then they later, they tried to control
nitrogen oxide emissions from power plants and cars and the ozone went down even further.
As an example, cars were required to have
catalytic converters installed on them, and a car today
is about 20 times less polluting than a car was in 1960.
But the situation was a little harder in the eastern US,
they had an ozone problem, but it wasn't so easy to reduce the ozone as it was in
California. Here is a satellite image of
the Atlanta metro area, and the thing you notice is that there are a lot of trees.
And that's the case for many cities in the US, or eastern US.
And these trees
put out lots of volatile organic compounds naturally.
Here is a representation of satellite data of one of these
VOCs. On a hot summer day, you see that their concentrations are very high.
Less so on a warm summer day, and
even lower still on a cool summer day. And it's not exactly
understood why trees are doing this. It's thought that maybe somehow
releasing these VOCs protects them from heat stress. But the exact mechanisms
are just not known yet. Okay,
so, in a city, in the eastern cities like Atlanta,
the only way that you can really reduce ozone
is to reduce nitrogen oxides. It's because there are so many
VOCs occurring naturally from these trees
that the amount coming out of the tailpipe of a car or factory is just very
small in comparison. Over the last two decades, there's been
a tremendous decrease in emissions of what the EPA calls
the six common pollutants. They've gone down by almost 60 percent.
And I've talked about five of these, sulfur dioxide,
nitrogen dioxide, ozone, volatile organic compounds, and particulates.
I didn't talk about lead because as far as I'm aware, we can't measure that from space yet.
And even though this may seem pretty
impressive or significant that it went down by 60 percent, it's even more
impressive when you take into account that our economy
has grown, our population has gone up, the number of cars on the road
have gone up, and the amount of energy we're consuming has gone up.
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And we can see this from space, this major decrease
in emissions just in the last decade. Here's a representation of nitrogen dioxide,
one of the nitrogen oxides, in 2005 and 2011.
And the concentrations went down by 30-40 percent just over that time.
Sulfur dioxide, a similar story. Emissions
went down by anywhere from 50 to about 90
percent. So it's been a real success story.
But the job isn't done yet, because about
120 million Americans still live in areas with poor air quality.
So we need to keep reducing our emissions. Now
most smog that we're breathing in any particular city is home-grown,
it's locally produced or regionally emitted. However,
the pollution that we emit today will affect someone downwind tomorrow.
For instance, Europeans grumble that American
pollution is blowing in the wind across the Atlantic and degrading their air quality.
And people in California complain that Asian pollution
is blowing across the Pacific and impacting them.
So, air quality is not just a local or regional problem, it's actually
a global problem now these days. So we need satellites to continue
to monitor our air quality from space. There's a fleet of satellites,
Earth-observing satellites, that are orbiting the planet right now. And they observe
everything from ice sheets to oceans to forests and so on
and including our air quality. And I've presented data from
some of those satellites, primarily the Aura satellite mission. And NASA will
continue to design and build bigger and better satellites and monitor our
Earth and our air quality in the future. Thank you.
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