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Matthias Müller was
appointed as new VW
CEO in September 2015
Protesters at the Volkswagen plant in November 2015WHAT ARE NITROGEN OXIDES
AND HOW DO THEY AFFECT THE
ENVIRONMENT AND HUMAN
HEALTH?Nitrogen oxides, also known as NOx, are
a family of gases produced during high-
temperature combustion in air. Before
humans came along, that meant forest
fires and lightning bolts, but since the
Industrial Revolution spread millions of
combustion engines around the planet,
the amount of NOx in the atmosphere
has increased dramatically. Cars, power
plants and planes all produce them in
large quantities, with the result that air
pollution is responsible for one in eight
deaths around the world.
Unlike carbon dioxide, NOx gases don’t
last too long in the atmosphere - only
a matter of hours. But that’s because
they react with other gases to form
even more noxious substances. They
react with ammonia, moisture and other
compounds to form nitric acid vapour,
which can damage sensitive lung tissue
and cause conditions like emphysema
and bronchitis.
They also react with another by-
product of combustion - volatile organic
compounds - to create ozone. When
ozone is up in the stratosphere, 10km
above the ground, it’s great. It protects us
from ultraviolet radiation, and that layer of
stratospheric ozone is crucial to life being
able to exist on Earth. Near the Earth’s
surface, though, ozone hangs around for
longer than NOx does, meaning that it
can cause health impacts – such as lung
damage – far from the source.
Finally, NOx gases react with a variety of
common organic chemicals to form toxic
products like nitroarenes, nitrosamines
and the nitrate radical - which can cause
biological mutations. That’s why you rarely
see moss and lichens on trees near city
roads - they can’t cope with the gases
emitted by car engines.