Montreal Protocol will spare Americans from 443 million skin cancer cases
BY
DAVID HOSANSKY
The
research team, by scientists at the National Center for Atmospheric Research
(NCAR), ICF Consulting, and U.S. Environmental Protection Agency (EPA), focused
on the far-reaching impacts of a landmark 1987 treaty known as the Montreal
Protocol and later amendments that substantially strengthened it. The agreement
phased out the use of chemicals such as chlorofluorocarbons (CFCs) that destroy
ozone in the stratosphere.
Stratospheric
ozone shields the planet from harmful levels of the Sun’s ultraviolet (UV)
radiation, protecting life on Earth.
To
measure the long-term effects of the Montreal Protocol, the scientists
developed a computer modeling approach that enabled them to look to both the
past and the future by simulating the treaty’s impact on Americans born between
1890 and 2100. The modeling revealed the treaty’s effect on stratospheric
ozone, the associated reductions in ultraviolet radiation, and the resulting
health benefits.
In
addition to the number of skin cancer and cataract cases that were avoided, the
study also showed that the treaty, as most recently amended, will prevent
approximately 2.3 million skin cancer deaths in the U.S.
“It’s very encouraging,” said NCAR scientist Julia Lee-Taylor, a co-author of the study. “It shows that, given the will, the nations of the world can come together to solve global environmental problems.”
The
study, funded by the EPA, was published in ACS Earth and Space
Chemistry. NCAR is sponsored by the National Science Foundation.
MOUNTING CONCERNS OVER THE OZONE LAYER
Scientists
in the 1970s began highlighting the threat to the ozone layer when they found
that CFCs, used as refrigerants and in other applications, release chlorine
atoms in the stratosphere that set off chemical reactions that destroy ozone.
Concerns mounted the following decade with the discovery of an Antarctic ozone
hole.
The
loss of stratospheric ozone would be catastrophic, as high levels of UV
radiation have been linked to certain types of skin cancer, cataracts, and
immunological disorders. The ozone layer also protects terrestrial and aquatic
ecosystems, as well as agriculture.
A
NASA false-color view of total ozone over the Arctic pole on Oct. 3, 2021. The
purple and blue colors show areas of least ozone, and yellows and reds show
areas of more ozone. (Image by NASA.)
Policy makers responded to the threat with the 1987 Montreal Protocol on Substances that Deplete the Ozone Layer, in which nations agreed to curtail the use of certain ozone-destroying substances.
Subsequent amendments strengthened the
treaty by expanding the list of ozone-destroying substances (such as halons and
hydrochlorofluorocarbons, or HCFCs) and accelerating the timeline for phasing
out their use. The amendments were based on input from the scientific
community, including a number of NCAR scientists, that was summarized in
quadrennial Ozone Assessment reports.
To quantify the impacts of the treaty, the research team built a model known as the Atmospheric and Health Effects Framework. This model, which draws on various data sources about ozone, public health, and population demographics, consists of five computational steps.
These simulate past and future emissions
of ozone-destroying substances, the impacts of those substances on
stratospheric ozone, the resulting changes in ground-level UV radiation, the
U.S. population’s exposure to UV radiation, and the incidence and mortality of
health effects resulting from the exposure.
The
results showed UV radiation levels returning to 1980 levels by the mid-2040s
under the amended treaty. In contrast, UV levels would have continued to
increase throughout this century if the treaty had not been amended, and they
would have soared far higher without any treaty at all.
Even
with the amendments, the simulations show excess cases of cataracts and various
types of skin cancer beginning to occur with the onset of ozone depletion and
peaking decades later as the population exposed to the highest UV levels ages.
Those born between 1900 and 2040 experience heightened cases of skin cancer and
cataracts, with the worst health outcomes affecting those born between about
1950 and 2000.
However,
the health impacts would have been far more severe without the treaty, with
cases of skin cancer and cataracts rising at an increasingly rapid rate through
the century.
“We
peeled away from disaster,” Lee-Taylor said. “What is eye popping is what would
have happened by the end of this century if not for the Montreal Protocol. By
2080, the amount of UV has tripled. After that, our calculations for the health
impacts start to break down because we’re getting so far into conditions that
have never been seen before.”
The
research team also found that more than half the treaty’s health benefits could
be traced to the later amendments rather than the original 1987 Montreal
Protocol. Overall, the treaty prevented more than 99% of potential health
impacts that would have otherwise occurred from ozone destruction. This showed
the importance of the treaty’s flexibility in adjusting to evolving scientific
knowledge, the authors said.
The
researchers focused on the U.S. because of ready access to health data and
population projections. Lee-Taylor said that the specific health outcomes in
other countries may vary, but the overall trends would be similar.
“The
treaty had broad global benefits,” she said.
ABOUT THE ARTICLE
Title: “Estimation of Skin and Ocular Damage Avoided in the
United States through Implementation of the Montreal Protocol on Substances
that Deplete the Ozone Layer”
Authors: Sasha Madronich, Julia Lee-Taylor, Mark Wagner, Jessica Kyle,
Zeyu Hu, and Robert Landolfi
Journal: ACS Earth and Space Chemistry