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Health Impacts
of Global Warming
Throughout the world, the prevalence of
particular diseases and other threats to human health depend largely on local
climate. Extreme temperatures can directly cause the loss of life. Moreover,
several serious diseases only appear in warm areas. Finally, warm temperatures
can increase air and water pollution, which in turn harm human health.
 The
most direct effect of climate change would be the impacts of hotter
temperatures themselves. Extremely hot temperatures increase the number of
people who die on a given day for many reasons: People with heart problems are
vulnerable because one’s cardiovascular system must work harder to keep the
body cool during hot weather. Heat exhaustion and some respiratory problems
increase.
Higher
air temperatures also increase the concentration of ozone at ground level. The
natural layer of ozone in the upper atmosphere blocks harmful ultraviolet
radiation from reaching the earth’s surface; but in the lower atmosphere,
ozone is a harmful pollutant. Ozone damages lung tissue, and causes particular
problems for people with asthma and other lung diseases. Even modest exposure
to ozone can cause healthy individuals to experience chest pains, nausea, and
pulmonary congestion. In much of the nation, a warming of four degrees (F)
could increase ozone concentrations by about 5 percent.
Statistics
on mortality and hospital admissions show that death rates increase during
extremely hot days, particularly among very old and very young people living
in cities. In July 1995, a heat wave killed more than 700 people in the
Chicago area alone. Studies based on these types of statistics estimate that
in Atlanta, for example, even a warming of about two degrees (F) would
increase heat-related deaths from 78 today to anywhere from 96 to 247 people
per year. If people are able to install air conditioning and otherwise
acclimatize themselves to the hotter temperatures, the lower estimate is more
likely.
Warmer
temperatures may decrease the number of people who die each year from cold
weather. However, in the United States, only 1000 people die from the cold
each year, while twice that many die from the heat. Moreover, of the ten
states with the greatest number of cold-related deaths, Alaska and Illinois
are the only northern states. For the most part, cold-related deaths occur
during occasional cold spells in areas with mild winters where people prepare
less for the cold, or during extreme events like the severe snow storm that
struck Colorado in November of 1997. Global warming is unlikely to reduce
either of these situations. Finally, deaths due to the heat are more sensitive
to temperature changes than deaths due to the cold; the difference between
-20°F and -15°F, for example, has a much smaller impact than an increase
from 95°F to 100°F.
Global
warming may also increase the risk of some infectious diseases, particularly
those diseases that only appear in warm areas.
 Diseases
that are spread by mosquitoes and other insects could become more prevalent if
warmer temperatures enabled those insects to become established farther north;
such "vector-borne" diseases include malaria, dengue fever, yellow
fever, and encephalitis. Some scientists believe that algal blooms could occur
more frequently as temperatures warm--particularly in areas with polluted
waters--in which case diseases such a cholera that tend to accompany algal
blooms could become more frequent.
In
spite of these risks, increased mortality is not an inevitable consequence of
global warming. Malaria, for example, is rare in the United States even in
warmer regions where the mosquito that transmits the disease is found, because
this nation has the ability to rapidly identify and contain outbreaks when
they appear. Heat-related deaths can be prevented by emergency measures to
move vulnerable people to air-conditioned buildings, and by reducing the
emissions of photochemical oxidants which cause ground-level
ozone. Many of the impacts of climate change on health could be avoided
through the maintenance of strong public health programs to monitor,
quarantine, and treat the spread of infectious diseases and respond to other
health emergencies as they occur. Although air-conditioning and public health
programs may impose additional costs on the public and private sectors, they
would often be preferable to the impacts on human health that would otherwise
occur.
U.S. Environmental Protection Agency
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Impacts of Global Warming
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