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Protecting our Health from
Climate Change:
a Training Course for Public
Health Professionals
Chapter 4: Overview of the
Health Impacts of Climate
Change
Overview: This Module
 Reviews the major health impacts of climate
change, including increases in the frequency
and intensity of extreme weather events
(heatwaves, floods, windstorms, droughts);
alterations in the transmission dynamics of
food-, water-, and vectorborne diseases;
and changes in the concentrations of air
pollutants (including aeroallergens)
Health Impacts of Climate Change
McMichael et al. 2003a
Direction and Magnitude of Change of Selected
Health Impacts of Climate Change
(IPCC, 2007a)
Negative Impact Positive Impact
Very High Confidence
Malaria: Contraction and expansion,
changes in transmission season
High Confidence
Increase in malnutrition
Increase in the number of people suffering
from deaths, disease and injuries
from extreme weather events
Increase in the frequency of cardio-respiratory
diseases from changes in air quality
Change in the range of infectious disease vectors
Reduction of cold-related deaths
Medium Confidence
Increase in the burden of diarrheal diseases
Pathways for Weather to Affect
Health: Example = Diarrheal Disease
Distal Causes
Proximal Causes
Infection Hazards
Temperature
Humidity
Precipitation
Survival/ replication
of pathogens in the
environment
Consumption of
contaminated water
Contamination of
water sources
Consumption of
contaminated food
Contamination of food
sources
Contact with
infected persons
Living conditions
(water supply and
sanitation)
Food sources and
hygiene practices
Rate of person
to person contact
Health Outcome
Incidence of
mortality and
morbidity
attributable
to diarrhea
Vulnerability
(e.g., age and
nutrition)
Multiple Factors Affect ClimateSensitive Health Outcomes
 Biophysical factors
– Baseline climate
– Elevation
– Natural resources (e.g., water bodies, soil
moisture)
 Biological sensitivity
– Concomitant diseases
– Acquired immunity
– Genetic factors
 Socioeconomic status
Intergovernmental Panel on
Climate Change 4th Assessment
 Health impacts due to climate change are occurring
– Impacts unevenly distributed
 Impacts will increase with increasing climate
change
– All regions will be affected
 Mitigation and adaptation needed now
– Inertia in the climate system means change will continue
for decades after successful control of greenhouse
emissions
– Extent of health impacts over next few decades will
depend on the design and implementation of effective
adaptation measures
IPCC AR4 Health Impacts of
Climate Change
 Emerging evidence of climate change impacts:
– Altered distribution of some vectors
– Altered seasonal distribution of some pollen species
– Increased risk of heatwave deaths
Annual Consequences of Diarrheal
Diseases, Malaria, and Malnutrition in
Children in Developing Countries
 Diarrheal diseases cause nearly 2 million
deaths, most attributable to contaminated
water and inadequate sanitation and
hygiene
 Malaria causes about 300500 million
infections, leading to approximately
13 million deaths
 Malnutrition is an underlying cause of
approximately 50% of the 10.5 million
deaths in children under the age of 5
Infant Mortality 1–4 Years
Worldmapper 2008f
World Population 1960
Worldmapper 2008e
World Population 2050
Worldmapper 2008b
Total CO2 Emissions
UNEP 2009
Health Burden of Climate Change
Impacts
Deaths from malaria and dengue fever, diarrhoea, malnutrition,
flooding, and (in OECD countries) heatwaves
Greenhouse Gases and Air
Pollutants
 Most sources of greenhouse gas emissions also
emit “conventional” air pollutants (PM, SO2,
NOx, VOC), which have negative impacts on
human health.
 Many — but not all — GHG mitigation measures
reduce also these air pollutants.
 Positive (side-)impacts on
– Human health through reduced air pollution,
– Air pollution emission control costs.
 Some measures have important trade-offs.
Economic Co-Benefits of GHG
Mitigation on Health
Findings of IPCC AR4
 Health benefits
make up between
50% and 400% of
carbon mitigation
costs
 Benefits range from
7 $/t C (USA) to
several 100 $/t C
(China)
Climate Change Is about Children
And Other Vulnerable Groups
Sum of Years of Life Lost and Years
of Life Lived with Disability
Pitcher et al. 2008
Impacts Will Depend on the
Local Context
Philip Wijmans, LWF/ACT Mozambique, March 2000
Possible Impact Scenarios
 Single large-scale disasters
 Repeated smaller disasters
 Continuous temperature increase producing
gradual, linear increase in climate-sensitive
health outcomes
 Any combination of the above
 Adverse health impacts of mitigation and
adaptation measures
Climate
Change Is
Adding More
Energy to the
Atmosphere
http://earthobservatory.nasa.gov
Heatwave:
August 2003
35,000 extra
deaths over a
two-week period
http://earthobservatory.nasa.gov
Emission Pathways, Climate
Change, and Impacts on California
Scenario
B1
A1fi
Angeles)
4X
68X
Length of heatwave
season
Heat-related mortality
57
weeks
913
weeks
Heatwave days (Los
(Los Angeles)
Hayhoe et al. 2004
23X
5–7X
Floods in Europe
1992: 1,346 killed in Tajikistan
1993: 125 died in Yekaterinburg, Russia
1996: 86 died in the Biescas campsite, Spain
1998: 147 died in Sarno, Italy
2002: 120 died in Central Europe
"EM-DAT: The OFDA/CRED International Disaster Database, www.em-dat.net – Université Catholique
de Louvain – Brussels – Belgium." Created on: May-23-2005. Data version: v05.05
Trends in
Disasters
over Time
Projected Changes in Ozone and
Related Deaths, New York Metro Area
1990
2050s
Kinney et al. 2006
2020s
2080s
2050s
Climate Change Will Affect Flora
and Fauna
Temperature and Enteric Disease
Temp Alberta Salmonella
Temp Alberta Campylobacter
Temp Alberta E. coli
1.0
0.6
0.6
0.4
0.5
0.2
0.4
0.0
0.0
0.2
-0.5
meanlag1
20
Temp Nfld-Lab Salmonella
-30
-20
-10
0
10
20
meanlag1
-1.5
10
lo(m eanlag1, span = 0.3)
0
-0.8
-10
lo(m eanlag1, span = 0.3)
-0.2
-20
-0.4
0.0
lo(m eanlag1, span = 0.3)
-30
-30
-20
-10
0
10
20
meanlag1
Temp Nfld-Lab Campylobacter
2
3
RR of Salmonella increased by 1.2% per degree above - 10˚C
2
1
RR of Campylobacter increased by 2.2% (4.5% in Newfoundland) per degree above - 10˚C
1
0
0
RR of E. coli increased by 6.0% per degree above - 10˚C
-1
-1
-2
lo(m eanlag1, sp
-2
lo(m eanlag1, sp
Fleury et al. 2006
Distribution of Lyme Disease,
1991–2000 and 2020
Tick abundance at model equilibrium
Ogden et al., 2005, 2006a, 2006b
for regions unaffected by summer cooling, and pink and red lines for areas affected by
summer cooling. Broken red lines indicate projected geographic range of temperature
conditions suitable for I. scapularisestablishment in the 2020s, 2050s and 2080s using climate
change projections (CGCM2 Scenario ‘A2’). Approximate locations of established I. scapularis
populations are indicated by green triangles. (from Ogden et al., 2005a,c)
Spread of Lyme Disease with
Climate Change
AB
SK
QC
MB
LNF
2080s
2050s
ON
2020s
Modeled geographic limits projected for the
establishment of I. scapularis ticks, in degree-days above
0ºC. Present modeled limits in blue or red (considering
Great Lakes cooling effect). Triangles indicate endemic
tick populations. Red dotted lines indicated projected
change in the modeled geographic limits in three future
time periods according to climate change scenarios
(Ogden et al., 2005).
PEI
NS
NB
Malaria in India
1980 to 2000
2050’s
Bhattacharya et al. 2006
IPCC AR4 Health Impacts of
Climate Change
 Health co-benefits from reduced air
pollution as a result of actions to reduce
greenhouse gas emissions can be substantial
and may offset a substantial fraction of
mitigation costs
 Actions to reduce methane will decrease
global concentrations of surface ozone
IPCC AR4 Health Impacts of
Climate Change (cont.)
 Adaptive capacity needs to be improved
everywhere
– Even high-income countries not prepared for extreme
weather events
 Adverse impacts will be greatest in low-income
countries
– Those at greatest risk include the urban poor, the elderly
and children, traditional societies, subsistence farmers,
and coastal populations
 Economic development is important, but is
insufficient to protect the world’s population
against the health impacts of climate change
– Critical factors include the manner in which growth
occurs, the distribution of benefits, public health
infrastructure, and other factors that determine
population health
Epidemiologic Research Tasks
 Exposure-response relationships between
background climate variation and health
outcomes
 Estimate the current health burden
(e.g., annual deaths) attributable to climate
change
 Develop scenario-based modeling to project
health risks
 Assess health harms and benefits of
proposed mitigation and adaptation policy
options