&EPA
United States
Environmental Protection
Agency
Office of Policy,
Planning and Evaluation
(2171)
EPA236-F-97-005
October 1997
Climate Change and
Public Health
ases in the atmosphere such
'"as carbon dioxide and
methane trap the sun's energy
and warm the earth. This natural
"greenhouse effect" is intensified
by human activities, especially
the combustion of fossil fuels.
Increased energy use in cars,
homes, and factories raises the
concentration of carbon dioxide
in the atmosphere, and this can
"The balance of
evidence suggests that
there is a discernible
human influence on
global climate."
Intergovernmental Panel on Climate
Change of the United Nations and
World Meteorological Organization
cause a variety of impacts on the
global climate. As the climate
changes, natural systems will be
destabilized, which could pose a
number of risks to human health.
Exactly how much risk is entailed
by climate change is difficult to
quantify in terms of projected
numbers of increased deaths or
illnesses. For one thing, human
populations differ in vulnerabil-
ity. Factors such as crowding,
food scarcity, poverty, and local
environmental decline make
populations in some developing
countries especially vulnerable.
Likewise, in industrialized
countries, the demographic trend
toward an aging population raises
the health risks.
POTENTIAL HEALTH IMPACTS FROM
GLOBAL CLIMATE CHANGE
.§
fl>
fft
Heat
Waves
More heat-related deaths
and illnesses
i
Air
Pollution
T3 ^MH
c
(O
CO
CD
c
0
o
"43
Terrestrial
Changes
Aggravation of cardiovascular
and respiratory diseases from
worsening air quality
Risk of infectious diseases because
of new geographic ranges and activity
of disease-carrying animals, insects,
and infective parasites
/*
Altered
Marine
Ecology
Changes in incidence of cholera and
food poisoning from toxic algae
Storms
Deaths and injuries from storms
and floods and intestinal illnesses
from flooding of sewage treatment
plants
Droughts
Rising malnutrition in
some countries
Population
Displacement
Injuries and increased risk
of disease due to migration
and crowding
ROT
Saltwater
Encroachment in
Coastal Aquifers
Greater risk of intestinal illnesses
from inadequate water supplies
-------
City
Chicago
Milwaukee
Philadelphia
St. Louis
St. Louis
St. Louis
Recent Heat
Year
1995
1995
1993
1995
1980
1966
Waves
Approx. No.
of Fatalities
465
85
118
31
113
400
Heat Waves
Some health consequences may occur as a direct result of
higher temperatures. More frequent or severe heat waves
could boost deaths and illnesses among the elderly,
infants, and people with cardiovascular and respiratory
disorders. Studies of selected U.S. cities indicate that the
number of heat-related deaths would increase substantially
by the year 2050 under some climate change scenarios.
The increase in mortality could be partially offset by a
decrease in cold-related deaths during milder winters. The
data are insufficient at present to quantify this tradeoff,
but preliminary results suggest that global warming would
cause a net increase in deaths. Gains and losses would
vary by region.
Adaptive responses such as use of air conditioning may
have important modulating effects on deaths related to
thermal stress. People living in inadequate housing with
no air conditioning in urban areas where heat is retained
by buildings and pavement are particularly vulnerable.
Acute Episodes of Air Pollution
No. of Fatalities
Year or Illnesses
1909
1930
Location
Glasgow, Scotland
Meuse Valley, Belgium
Donora, Pennsylvania 1948
London
New York City
1952
1953
1,063 deaths
63 deaths and
6,000 people sick
20 deaths and
1,190 people sick*
4,000 to
8,000 fatalities
175 to 260 fatalities
'Almost 43 percent of the area's population.
Air Pollution
In the 20th century, there have been several episodes where
sudden build-ups of air pollution have caused widespread
illnesses and deaths. With the introduction of air pollution
control measures, these severe episodes have been avoided.
However, moderate air pollution episodes continue to occur
especially under adverse weather conditions.
Hotter temperatures could enhance the formation of
secondary air pollutants such as ground-level ozone.
Burning fossil fuels such as coal, gas, and oil produces a
Temperature Sensitivity of Two Malaria Parasites
1
I
10 33
Days (Incubation Period)
From Giles HM. Epidemiology of Malaria. In: Giles HM, Warrell DA, eds. Bruce-Chwatt's
essential malariology. London: Edward Arnold Div. of Hodder & Stoughton; 1993.
number of air pollutants in addition to carbon dioxide.
Exposure to air pollutants has been shown to aggravate
respiratory and cardiovascular diseases and cause premature
deaths. The net effect on human health from simultaneous
exposure to stressful weather and air pollution may be
greater than the separate effects added together.
Infectious Diseases
Some health effects of climate change may occur indirectly
through impacts on natural ecosystems. Altering climatic
factors such as temperature, surface water, and humidity
can change the habitat of organisms such as mosquitoes
and rats and the parasites they carry. Changing the
abundance and geographic range of carriers and parasites
could shift the seasonal occurrence of many infectious
diseases and cause them to spread.
For example, simulations based on climate change
scenarios for the latter half of the next century predict an
increase from approximately 45 percent to 60 percent in
the proportion of the world's population living within the
-------
potential zone for malaria transmission. Climate change
may intensify transmission and could result in 50-80
million additional cases annually, against an assumed
global background total of 500 million.
Other infectious diseases such as encephalitis and dengue
(a severe influenza-like disease) also are sensitive to
climate. Recent field studies in California suggest that a
3° to 5°C increase in temperature could cause a signifi-
cant northern shift in the United States in two types of
encephalitis. In addition, annual epidemics of dengue
have returned to Central America during the past decade.
In Mexico, dengue has spread to higher elevations that
were previously unaffected, and it could reach the
southern United States.
"It is anticipated that most of the [health]
impacts would be adverse."
Intergovernmental Panel on Climate Change of the
United Nations and World Meteorological Organization
Developed countries should be able to minimize exposure
to these diseases through existing methods such as spraying
insecticides to control insects and other disease-bearing
organisms. However, these pesticides entail health risks
themselves. Further, the quicker "turnover" of parasite life
cycles that occurs in warmer temperatures would increase
the likelihood of their evolving greater resistance to drugs
and control methods.
Water-borne Diseases
Poor sanitation, poor erosion control management, coastal
sewage release, and contamination of drinking water from
agricultural fertilizers and waste may all increase the
likelihood of water-borne diseases. Any changes that affect
the sea—water temperatures at the surface, nutrient levels,
winds, currents, and precipitation patterns—also can
change the marine ecosystem, leading to possible increases
in diseases transmitted from fish and shellfish. Higher
surface temperatures, for example, stimulate the growth of
certain species of algae, in particular, toxic "red tides."
When these algae are consumed by fish and shellfish, they
pose a threat of food poisoning to humans.
Marine phytoplankton and zooplankton can shelter a
dormant form of cholera when pH, temperature, salinity,
and nutrient levels are insufficient to sustain the infectious
Health-Related Impacts of
Mississippi River Flood of 1993
Fatalities 48
Health-Related Impacts
Displaced Missourians
(increased exposure to
risk of disease) 60,000
Injuries and illnesses
in Missouri* 483
Hospital emergency room
patients in Missouri* 234
Hospitalizations in Missouri* 32
Potential Health-Related Impacts
Closures of primary-care 1 4% of population
physician offices in Iowa*
Interruptions in public
health services in Iowa**
Loss of operating public water
system in Des Moines, Iowa
Loss of operating public sewer
systems in Iowa***
More reports of mosquitoes
and rats in Iowa**
affected
24% of population
affected
250,000 people
affected for 1 2
days
35% of population
affected
53% of population
affected
Emergency room flood-related data reported to CDC for
July 16-September 3.
CDC survey for July 15-16.
CDC survey for week of July 18-24.
form. When waters warm or when nutrient levels increase,
cholera can become infectious again.
In addition, saltwater intrusion caused by changes in sea
level is threatening drinking water supplies in many
communities along the East Coast. Florida has already
resorted to building a large number of desalinization plants.
Weather Disasters
Climate change could alter the frequency and severity of
extreme weather events. In some cases (e.g., hurricanes),
current climate models are unable to predict whether these
extreme weather events will increase. There is no clear
evidence for changes in extreme events worldwide in
recent decades, but evidence of changes on a regional level
does exist.
Such events, when they occur, endanger human health by
increasing deaths, injuries, infectious diseases,
-------
stress-related disorders, and the adverse health effects
associated with social disruption and forced migration,
internal or external.
Floods could lead, in addition to deaths, to the spread of
infectious diseases because of crowded living conditions in
shelters, exposure to fecal material because of impaired
sewage treatment, exposure to toxic chemicals from heavier
runoff from agricultural lands and urban stormwater systems,
and hazardous exposure from ingesting contaminated water
and fish.
What Needs to Be Done
Everyone has a part to play in preventing the probable
negative health effects from climate change. Individuals
and businesses can help by taking steps to reduce the
burning of fossil fuels. Gains in energy efficiency of 10 to
30 percent above present levels are feasible at little or no
cost through conservation measures, use of available
technologies, development of new energy technologies,
and better land management practices.
If intense rainfall and floods occur more frequently in a
warmer world, the number of displaced victims and rates of
injuries and infectious diseases could rise.
Federal, state, and local governments can play an
important role by enacting flexible and cost-effective
policies to reduce greenhouse gas emissions. Significant
reductions in net greenhouse gas emissions can be
achieved by employing an array of technologies and policy
measures that accelerate technology development and
transfer. However, it will be important to assess risks to
health from proposed technological adaptations. For
example, intensive use of air conditioning would protect
against heat stress, but it also could boost emissions of
greenhouse gases and conventional air pollutants.
Physicians and public health practitioners can help by
directly reducing the impacts through improved
primary health care for vulnerable populations.
Measures that can be taken include improved public
health monitoring, better disease surveillance and
control programs, more thorough disaster preparedness
vaccination, and public education.
Communities and state governments can help through
better management of ecosystems, wider use of protective
technologies such as sea walls and levees, and improved
water purification. Assessing the risks from these adaptive
strategies is also critical. For example, if new pesticides are
used to control insects, the effects of these pesticides on
human health, insect predators, and increased insect
resistance all need to be considered.
For More Information
Call EPA's Fax-On-Demand service (202-260-2860),
or access EPA's global warming Internet site at
http://www.epa.gov/globalwarming.
Reference
McMichael, A.J., et al. 1996. Human population health
(Chapter 18). In Climate change 1995—Impacts, adaptations,
and mitigation of climate change: Scientific-technical analyses.
Intergovernmental Panel on Climate Change (IPCC),
pp. 563-584.
------- |