The Montreal Protocol, enacted in 1987, put controls on use of aerosol CFC's.
“The Montreal Protocol is working,”
says chemist Mario Molina, who shared the Nobel Prize for his work on the
effects of chlorofluorocarbons (CFCs). “CFCs are a global environmental
problem that is being solved by society.”
The international treaty, which opened
for signature in 1987, created controls on the use of CFCs, gases used as
coolants in refrigerators and to propel aerosols like hair spray out of cans.
The problem was that CFCs spread out in the stratosphere, where they led to a
hole in the ozone layer.
When Molina started studying CFCs in
the 1970s and discovered their role in ozone depletion, each U.S. household
averaged 30 to 40 spray cans. Since the late ’90s, CFC production has all but
stopped, making modern spray cans ozone safe.
The ozone layer itself? Though
scientists say it will take until beyond 2050 to return to pre-1980s levels of
CFCs—they take about a hundred years to decompose—the amounts in the atmosphere
are steadily decreasing. (See chart below.)
Chart by NGM Art. Source: David W.
Fahey, NOAA Earth System Research Laboratory
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