What’s in the air you breathe? - Amy Hrdina and Jesse Kroll
Take a deep breath.
In that single intake of air,
your lungs swelled with roughly
25 sextillion molecules,
ranging from compounds produced days ago,
to those formed billions of years
in the past.
In fact, many of the molecules
you’re breathing were likely
exhaled by members
of ancient civilizations
and innumerable humans since.
But what exactly are we all breathing?
Roughly 78% of Earth’s atmosphere
is composed of nitrogen
generated by volcanic activity
deep beneath the planet’s crust.
The next major ingredient is oxygen,
accounting for 21% of Earth’s air.
While oxygen molecules have been around
as long as Earth’s oceans,
oxygen gas didn’t appear until
ocean dwelling microorganisms
evolved to produce it.
Finally, .93% of our air is argon,
a molecule formed from the radioactive
decay of potassium
in Earth’s atmosphere, crust, and core.
Together, all these dry gases
make up 99.93% of each breath you take.
Depending on when and where you are,
the air may also contain some water vapor.
But even more variable
is that remaining .07%,
which contains a world of possibilities.
This small slice of air is composed
of numerous small particles
including pollen, fungal spores,
and liquid droplets,
alongside trace gases
like methane and carbon dioxide.
The specific cocktail of natural
and man-made compounds
changes dramatically from place to place.
But no matter where you are,
.07% of every breath you take
likely contains man-made pollutants—
potentially including toxic compounds
that can cause lung disease, cancer,
and even DNA damage.
There’s a wide variety of known pollutants
but they all fall into two categories.
The first are primary pollutants.
These toxic compounds are directly emitted
from a man-made
or naturally occurring source.
However, they don't always come
from the places you'd expect.
Some large factories mostly generate
water vapor,
with only small quantities of pollutants
mixed in.
Conversely, burning wood or dung can
create polycyclic aromatic hydrocarbons;
dangerous compounds that have been
linked to several types of cancer,
as well as long-term DNA damage.
In all cases, pollutants interact with
regional weather patterns and topography,
which can keep compounds local
or spread them kilometers away.
When these molecules travel
through the air, a transformation occurs.
Natural compounds called oxidants,
formed by oxygen and sunlight,
break down the pollutants.
Sometimes, these reactions make pollutants
more easily washed out by rain.
But in other cases, they result
in even more toxic secondary pollutants.
For example, when factories burn coal,
they release high concentrations
of sulfur oxides.
These molecules oxidize to form sulfates,
which condense with water vapor in the air
to form a blanket of fine particles
that impair visibility
and cause severe lung damage.
This so-called sulfurous smog was
well-known in 20th century London
and continues to plague cities
like Beijing.
Since the advent of cars,
another secondary pollutant
has taken center stage.
Exhaust from fossil fuel-burning vehicles
releases nitrogen oxides and hydrocarbons
which react to form ozone.
And while some ozone
in the upper atmosphere
helps shield us from ultraviolet rays,
on the ground,
this gas can form alongside secondary
particles and create photochemical smog.
This brown fog can be found covering
densely packed cities,
making seeing difficult
and breathing hazardous.
It also contributes to climate change
by trapping heat in the atmosphere.
In recent decades, industrial activity
has contributed to a huge spike
in various trace gas emissions,
fundamentally changing the air
we all breathe.
Many places have already responded
with countermeasures.
Most cars produced since the 1980′s
are equipped with catalytic converters
that reduce the emission
of carbon monoxide and nitrogen oxides.
And today, places like Beijing are
battling smog
by electrifying
their energy infrastructure
and limiting automobile emissions
altogether.
But while moving away from fossil fuels
is essential,
there's no universal remedy
for air pollution.
Different regions need to respond
with unique regulations
that account for their local pollutants.
Because no matter where you live,
we all share the same air.
