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♪

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>>One of the difficulties in
understanding air quality

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is that the pollution that
affects your health the most,

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is not the initial component
put into the atmosphere.

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>>Under certain
atmospheric conditions,

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some of these pollutants
react with each other

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and produce new harmful
agents like Ozone.

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>>There's three key ingredients
to make ozone.

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NOx, hydrocarbons and sunlight.

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>>So think of ozone
as an important

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cleansing agent from
the atmosphere.

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When you have a big stain to
clean you use a lot of cleanser.

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And when you create
a lot of pollution,

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a lot of ozone becomes evident
in the atmosphere.

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That's helping to clean
the atmosphere

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but it's also
impacting our health.

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>>We have primary pollutants.

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Nitrogen oxides and

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reactive hydrocarbons

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are most important

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in the formation of ozone.

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>>Your car emits both

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NOx and hydrocarbons

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with the unburned fuel

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>>But the ozone itself comes
from the chemistry,

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so we call it a
secondary pollutant,

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because it results from the
chemistry that occurs after

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the emission of the
nitrogen oxides

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and the reactive hydrocarbons.

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>>When nitrogen oxides and
hydrocarbons react with sunlight,

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they produce a harmful
secondary pollutant: Ozone.

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But wait!
Isn't ozone good for us?

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Well... it depends!

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>>The role of ozone in the
atmosphere is quite complex

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In the stratosphere ozone
is a great benefit

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because it protects us
from UV radiation.

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In the lower atmosphere,
ozone is also a benefit

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because it's responsible
for initiating

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the chemistry that cleanses
the pollution out.

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But when pollution levels
are very high,

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the chemistry runs the muck

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and you create very
high levels of ozone.

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And those ozone levels
can become so high,

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that they become reactive
with our own body tissues

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and become a problem
in terms of health.

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>>Photochemical smog
is considered to be

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a problem of modern
industrialization.

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It is present in all
modern cities,

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but it is more common in cities
with sunny, warm, dry climates

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and a large number
of motor vehicles.

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It can also affect rural areas

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where agriculture, trees and
forest fires can release

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a considerable amount of
volatile organic compounds

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or VOCs.

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>>What are the sources of VOCs...?

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We have the evaporation
of gasoline

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when you're filling your tank

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Petrochemical plants...

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The refineries that are making
gasoline for us from oil

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and also the plastics companies

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that are making plastics,
polyethylene, polypropylene...

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>>In terms of reactive nitrogen,

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man activity far outpaces
the natural sources

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and so we can say that,

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when nitrogen oxides
are present...

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that's man!.

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When you talk about
reactive hydrocarbons,

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actually vegetation plays
a major global role

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in creating them!

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>>Trees can emit that pine
tree smell that you smell...

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But also, a lot of the
deciduous trees

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are emitting isoprene.

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Isoprene is very reactive

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and very good at making
both particles and ozone.

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>>But, fortunately, they create
very specific molecules.

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And when man creates pollution,

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it creates a different
chemical mix.

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And so we can look at
the constituents

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of the reactive hydrocarbons
to determine

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whether is nature
or whether is man.

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>>But because these compounds
travel with the wind,

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they can affect different
parts of the world.

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Recently, scientists from
other airborne campaigns,

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were able to trace the origin of
unusual high levels of ozone

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in the air above the
western Pacific Ocean.

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They found that they were linked

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to the organic compounds
released by forest fires

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in Southeast Asia and Africa...

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Half a world away!.

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>>The atmosphere is a
shared resource

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and we're seeing more
and more that the entire

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northern hemisphere is suffering
from pollution background levels

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that are due to all of us,
not just one.

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>>Everyone living in a big city
around the world

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is breathing polluted air...

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and it's having an impact.

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>>It's part of the tug of war
between progress

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and the price that we
pay for that progress.

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And so that balance needs to be
maintained into the future

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as we continue to
develop economically,

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develop technologically...

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We have to pay attention to how
that's impacting the air quality

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>>Our world is an
interconnected system

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and the impact of air pollution
goes beyond the air we breath

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>>All of the processes
that are emitting

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and causing air pollution,

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are also putting CO2
into the atmosphere,

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causing climate change...
global warming...

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>>It also affects our soils,
our glaciers, our oceans...

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Our climate!

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>>And this is a problem

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that is going to affect our
children and our grandchildren.

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So it's very selfish
of us to ignore