Download The Effect of Climate Change on Human Health

The Effect of Climate Change on
Human Health
Spring 2012, Lecture 13
1
Overview of Effects
• Climate change is expected to have a major influence
on certain types of disease
• Changes in both temperature and humidity will play
an important role
• Some of the effects are already being seen
• Some increased health risk will be due to extreme
weather events, like the 2010 heat wave in Russia, but
many problems will involve continual climate
modification
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Increased Risk and Benefit
• Some climate changes may produce health
benefits, but most will increase risk
• The following slides outline a few examples
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Increased Heat
• Risk - More deaths and increased disease risk
due to very hot days
• Benefit – Fewer winter deaths and disease
events
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Heat-wave Effects
• According to the IPCC Fourth Assessment
(2007), by 2100:
o Chicago is projected to experience 25% more
frequent heat waves
o Los Angeles is expected to experience a four to
eight-fold increase in heat-wave days
• Those with heart problems, asthma, the
elderly, the very young and the homeless can
be especially vulnerable to extreme heat
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Increased
Heat Stress
•
•
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Schematic representation of how an increase in average annual temperature
would affect annual total of temperature-related deaths, by shifting distribution
of daily temperatures to the right
Additional heat-related deaths in summer would outweigh the extra winter deaths
averted (as may happen in some northern European countries)
Average daily temperature range in temperate countries would be about 5–30ºC.
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Food Poisoning
• Risk increases due to higher temperatures
• Salmonellosis is especially likely to be a
problem
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Aero-allergen Production
• Risk – Increased allergic disorders, including
hay fever and asthma due to longer pollen
seasons
• Benefit – Reduced exposure to aero-allergrens
in some places due to lower productions or
shorter seasons of pollen circulation
o Higher temperatures and changed humidity may
make the growing seasons shorten for some plants
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Effects of Extreme Temperatures
• A European study of hospital admission data for a
dozen major cities found that for every 1ºC rise in
temperature, hospital admissions for respiratory and
asthma-related illness increase up to 4.5% among the
elderly
• The Russian heat wave of 2010 doubled the death rate
in Moscow to 700 people per day during the heat
wave
• During the summer 1995 heat wave in Chicago, it is
estimated there were 700 excess deaths due to heat
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Water-borne Infection
• Risk - Cholera risk will increase in coastal or
estuarine regions, due to a warming of water
temperatures
• Benefit – risk will diminish in areas where
heavy rainfalls decrease
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Vector-borne Infections
• Risk – Both mosquito and tick borne infections
are likely to increase
• Benefit – In areas of diminished rainfall,
mosquitoes, ticks, and snails may become less
prevalent, and regions of very high
temperatures may also decrease these vectors
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Vector-borne Disease and Climate
Associations
• Vector-borne diseases have been shown to be
associated with changing climate conditions,
especially El Nino-Southern Oscillation
(ENSO ) events
o Malaria – South Africa, Columbia, Venezuela
o Dengue fever – Asia-Pacific
o Ross river virus – Australia
o West Nile – Numerous places, including the U.S.
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Vector-borne Disease
• In epidemiology, a vector is an insect or any living
carrier that transmits an infectious agent
• A vector serves two functions:
o It is required for part of the parasite's developmental cycle
o It also transmits the parasite directly to subsequent hosts
• Most commonly known vectors consist of arthropods,
domestic animals, or mammals that assist in
transmitting parasitic organisms to humans or other
mammals
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Common Vectors
• Mosquitoes serve as
vectors for Malaria,
Dengue fever, Yellow
fever, and Chikungunya
• Ticks can serve as vectors for
Lyme disease, Rickettsia, and
Babesiosis
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Climate Effects on Disease Vectors
• High temperatures affect both vector and
pathogen
• Rainfall effects are more complex
o Heavy rainfall and flooding may trigger outbreaks
of diarrhea in areas where crowding and poverty
are present
o Very high rainfall can reduce mosquito populations
by flushing larvae from their habitat in pooled
water
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Increased Malaria Risk
• The IPCC has noted that the global population
at risk from vector-borne malaria will increase
by between 220 million and 400 million in the
next century
• While most of the increase is predicted to
occur in Africa, some increased risk is
projected in Britain, Australia, India and
Portugal
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The Effect of Increased Heat
• Hotter, more humid weather shortens mosquito
breeding cycles
• The incubation of dengue virus is speeded up
by increased temperatures
• Milder winters also allow the survival of many
disease related organisms
o Mosquitos, tics and mice
o Lyme disease, Rocky Mountain spotted fever,
equine encephalitis, anaplasmosis, and bebesiosis
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Pesticides and Health
• In the decades of the 1950’s and 60’s, DDT was
widely used to curtail mosquito breeding grounds
• In her 1962 book Silent Spring, the late Rachel
Carson pointed out the tremendous environmental
havoc being wrought by DDT and related compounds
• Current opinion is that curtailing DDT may have
contributed to the current problem, but today’s
problems go well beyond the use of pesticide
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Public Health Opinion
• John Balbus, senior adviser for Public Health at the
National Institute for Environmental Health Sciences
siad in an article in the December, 2010 Discover
magazine:
o “Climate change will cause a worsening of the common
health problems we already see. There will be incremental
changes in the next 5 or 10 years, but that might not
compare to what we’re going to see in a matter of decades.
In trying not to be alarmist, scientists have systematically
underestimated the threat.”
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West Nile Virus
• Another vector borne disease is West Nile virus
• It first occurred in Uganda in 1937, with later
outbreaks in Israel in the late 1950’s, and
Romania in 1996
• It has since spread to the U.S., appearing in
New York in 1999
• The vector is Culex pupiens, a common house
mosquito
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Conditions for Spreading West Nile
• West Nile becomes a threat after periods of
hot, dry weather
• In New York in 1999, there was a period of ten
days with temperatures over 100ºF, followed
by heavy rains
• The resulting floods created mosquito breeding
grounds, and populations increased rapidly
• Birds drinking in stagnant pools of water were
infected
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Bronx Zoo
• Birds at the Bronx Zoo became infected, with
deaths of several species
o Crows
o Flamingoes
o Bald Eagles
• More than 30,000 West Niles cases have
occurred in the U.S. since 2002, with over
1000 deaths
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Infectious Diseases
• Many infectious agents, vector organisms, nonhuman reservoir species, and rate of pathogen
replication are sensitive to climatic conditions
• Salmonella and cholera bacteria, for example,
proliferate more rapidly at higher temperatures,
salmonella in animal gut and food, cholera in water
• In regions where low temperature, low rainfall, or
absence of vector habitat restrict transmission of
vector-borne disease, climatic changes could tip the
ecological balance and trigger epidemics
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Dengue Fever in the United States
• Dengue fever was thought to be eradicated in
the U.S., but has been making a comeback
• There are two forms
o Classic dengue fever has been present in northern
Mexico (Matamoros) and is occurring in
Brownsville, Texas
o Dengue Hemorrhagic Fever was seen in
Brownsville, for a resident who contracted the
disease in the U.S., in 2005, and has been
spreading
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Dengue Hemorrhagic Fever
• The appearance of Dengue Hemorrhagic Fever
in the United States was of great concern
o There is no vaccine to protect against it
o There is no medicine to cure it
• The patient in Brownsville recovered, but
those people who have other health problems
would probably not be so lucky
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Flooding
• Floods are classified as low-probability, high
impact events
• For the decade 1992-2001, there were nearly
100,000 flood related deaths, and 1 to billion
people were affected by flooding
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Increased Risk of Floods
• More injuries and deaths due to flooding
• Increased risk of infectious disease due to
flooding, and mental health disease brought on
by flood-related stress
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Short Term Flood Effects
• Some health consequences arise during or soon
after the flooding
• These include injuries, communicable
diseases, or exposure to toxic pollutants
• Excessive rainfall facilitates entry of human
sewage and animal wastes into waterways and
drinking water supplies, increasing the risk of
water-borne diseases
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Longer Term Flood Effects
• Other effects of flooding may appear later
• These include malnutrition, caused by crop
loss, and mental health disorders resulting
from the stress of flood-related problems
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Droughts
• Droughts represent the other extreme of weather
related precipitation problems
• Globally, disaster effects are greatest for droughts
(and associated famines) because of their regional
extent, which are usually much larger than floodrelated regions
• Another pollutant of concern is "particulate matter,"
also known as particle pollution or PM
• Climate change may indirectly affect the
concentration of PM pollution in the air by affecting
natural or “biogenic” sources of PM such as wildfires
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and dust from dry soils
Particulate Matter
• PM is a complex mixture of extremely small particles
and liquid droplets
• When inhaled, these particles can reach the deepest
regions of the lungs
• Exposure to particle pollution is linked to a variety of
significant health problems
• Particle pollution also is the main cause of visibility
impairment (haze) in the nation’s cities and national
parks
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Poverty and Disease
• Susan Fisher-Hoch, an epidemiologist at the
University of Texas School of Public Health said,
o “If dengue moves into a population that hasn’t experienced
it and has no natural immunity, we are going to see more
severe disease”
o “The way we live hermetically sealed in our houses – with
screens on the windows and air-conditioning – protects us
enormously. But what about those who don’t live well – the
people in trailer parks sitting on their porches surrounded
by mosquitoes?”
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Additional Problems
• According to a paper by McMichael et al.
(2006) in The Lancet, IPCC modeling
indicates a future increase of 5-10% in the
number of malnourished people
• Conflicts over food, together with migrant and
refugee flows likely to result from these widerranging effects would create additional
problems
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Anticipated Consequences
• These additional effects include:
o Increase in infectious disease cases
o Malnutrition
o Mental health problems
o Injury and violent death from conflict
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The Effects of Climate Change
• The video shows a report that resulted from a
collaboration between the British medical journal,
The Lancet, and University College London
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