Lesson 83: Destruction of the Ozone Layer
In this lesson, we will learn about the Earth's ozone layer, how
chlorofluorocarbons (CFCs) can damage the ozone layer, and what is being done
to reduce the use of CFCs.
The ozone layer in the stratosphere protects the Earth from
harmful ultraviolet radiation. The ozone acts as a protective shield, stopping
99% of all UV radiation. Without this protection, UV light would pass through
the air unstopped. Ultraviolet rays can severely damage tissues of all living
things. If the ozone layer were completely depleted and UV rays passed through
unimpeded, life as we know it would cease to exist.
Human activity has caused destruction of the ozone layer primarily through the
use of chemicals called CFCs.
Chlorofluorocarbons (CFCs) are chemical compounds that are used widely in
industrial production, refrigeration, computer cleaning, and as pressurizing
agents for aerosol cans.
CFCs damage the ozone layer through the release of chlorine atoms. The chlorine
acts as a catalyst, promoting a chemical reaction without being used up in the
reaction. Damage to the ozone layer increases the amount of UV light that
passes through, resulting in skin cancer.
The Ozone hole refers to
a serious thinning of the stratospheric ozone layer over the South Pole. This
is an area the size of the United States where ozone layers were 50% less than
normal. If this had happened anywhere else on the planet with human
civilization present, this break in the ozone layer would have been catastrophic.
The Montreal Protocol in
1987 initiated by the United Nations addressed ozone depletion where member
nations agreed to scale back CFC production to 50% by 2000.
After years of resistance, DuPont, a major chemical company in
the United States and one of the biggest producers of CFCs, pledged to
phase out its use by 2020.
CFC use is down after the Montreal Protocol but there are
other ozone-depleting substances such as methyl bromide and nitrous oxide.