Protecting the ozone layer is delivering vast health benefits
Montreal Protocol will spare Americans from 443 million skin cancer cases


Date:
October 6, 2021
Source:
National Center for Atmospheric Research/University Corporation
for Atmospheric Research
Summary:
An international agreement to protect the ozone layer is expected
to prevent 443 million cases of skin cancer and 63 million cataract
cases for people born in the United States through the end of this
century, according to new research. The research team developed a
computer modeling approach that revealed the effect of the Montreal
Protocol and subsequent amendments on stratospheric ozone, the
associated reductions in ultraviolet radiation, and the resulting
health benefits.



FULL STORY ==========================================================================
An international agreement to protect the ozone layer is expected to
prevent 443 million cases of skin cancer and 63 million cataract cases
for people born in the United States through the end of this century,
according to new research.


==========================================================================
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.

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 were 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.

========================================================================== Story Source: Materials provided by National_Center_for_Atmospheric_Research/University Corporation_for_Atmospheric_Research. Original written by David
Hosansky. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Sasha Madronich, Julia M. Lee-Taylor, Mark Wagner, Jessica Kyle,
Zeyu Hu,
Robert Landolfi. Estimation of Skin and Ocular Damage Avoided in
the United States through Implementation of the Montreal Protocol
on Substances that Deplete the Ozone Layer. ACS Earth and Space
Chemistry, 2021; 5 (8): 1876 DOI: 10.1021/acsearthspacechem.1c00183 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/10/211006134930.htm

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