Climate Change and Human Health:

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1900 1950
2000
2050 2100
Climate Change and Human Health Knowledge gaps
and research needs Basel University, January
2004 Carlos Corvalan, World Health Organization
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Climate Change and Human Health Knowledge gaps
and research needs Why should we be
concerned? What do we know about climate change
and health impacts? What are the main knowledge
gaps? How are we responding?
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Global environmental change and health
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Global environmental change and health The scale
of environmental health problems has expanded
from household (e.g. indoor air pollution), to
neighbourhood (e.g., domestic wastes) to city
(e.g. urban air pollution) to region (e.g.
transboundary contamination), to global level.
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Climate Change and Human Health Knowledge gaps
and research needs Why should we be
concerned? What do we know about climate change
and health impacts? What are the main knowledge
gaps? How are we responding?
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Weather, an ancient human exposure On Airs,
Waters and Places. Hippocrates (Circa 400 B.C)
Whoever wishes to investigate medicine
properly, should proceed thus in the first
place to consider the seasons of the year, and
what effects each of them produces for they are
not at all alike, but differ much from themselves
in regard to their changes. Then the winds, the
hot and the cold, especially such as are common
to all countries, and then such as are peculiar
to each locality
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Weather extremes have significant impacts on
health 1998 - Hurricane Mitch most
destructive tropical cyclone in 200 years.
Caused 7,500 deaths in Honduras, Nicaragua,
Guatemala and El Salvador.
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Weather extremes have significant impacts on
health 2000 - Mozambique floods killed 500
people and left 330,000 homeless.
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Heat waves and air pollution Heat waves can
cause heat-related illness and death (e.g. heat
stroke). The elderly and persons with heart or
respiratory disease are particularly
vulnerable. Stagnant weather conditions in
cities can trap both warm air and air
pollutants, leading to smog episodes which can
have significant impacts on health.
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IPCC Third Assessment Report The scientific
evidence for climate change and its impacts is
assessed by the Intergovernmental Panel on
Climate Change (IPCC). According to the most
recent IPCC Third Assessment Report (2001),
Adaptation is a necessary strategy at all
scales to complement climate change mitigation
efforts. Those with the least resources have
the least capacity to adapt and are the most
vulnerable
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Climate change facts The average temperature in
many regions has been increasing in the recent
decades. The global average surface temperature
has increased by 0.6 0.2 - C over the last
century. Globally, 1998 was the warmest year and
the 1990s was the warmest decade on record. Many
areas have experienced increases in rainfall,
particularly mid to high latitude countries.
Some regions, such as parts of Asia and Africa,
the frequency and intensity of droughts have been
observed to increase in recent decades. Episodes
of El Niño have been more frequent, persistent
and intense since mid-1970s compared with the
previous 100 years.
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• Climate Change and Human Health issues
• Of growing public health concern
• Potentially serious health consequences
• Disproportionate impact on poor countries
• Disproportionate impact on the poor and
  vulnerable groups in general
• May contribute to increase health inequalities
  within and between countries
• Expected increased demand from Member States
  for technical and scientific advice

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Climate Change and Human Health Knowledge gaps
and research needs Why should we be
concerned? What do we know about climate change
and health impacts? What are the main knowledge
gaps? How are we responding?
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Global warming - projections Global mean surface
temperature will rise by 1.4 - 5.8 C. Warming
will be greatest over land areas, and at high
latitudes. The projected rate of warming is
greater than anything humans have experienced in
the last 10,000 years. The frequency of weather
extremes is likely to change leading to an
increased risk of floods and drought Fewer cold
spells but more heatwaves are expected. The
frequency and intensity of El Niño may be
affected. Global mean sea level is projected to
rise by 9 88 cm by the year 2100
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Global Climate Change and Potential Impacts on
Human Health

• Most expected impacts will be adverse but some
  will be beneficial. Generally not novel processes
  expected but rather, changes in frequency or
  severity of various familiar health risks, for
  example
• floods, storms, cyclones and fires
• heat waves and air pollution (stagnant weather
  conditions)
• change in the range and seasonality of
  infectious diseases
• change in agricultural productivity
• the health consequences of altered freshwater
  supplies
• the consequences of population displacement

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Health impacts Water To a large extent, public
health depends on safe drinking water, sufficient
food, secure shelter, and good social conditions.
All these factors can be affected by climate
change. Fresh water supplies may be affected,
reducing the availability of clean water for
drinking and washing. Supplies can be
contaminated and sewage systems may be damaged,
increasing the risk of spread of infectious
diseases.
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Global Water Supply and Sanitation Assessment
Report 2000 WHO UNICEF WSSCC 1.1 billion without
appropriate access to water 2.4 billion
without appropriate sanitation services 2.2
million people, mostly children in developing
countries, die every year from diseases
associated with lack of safe drinking-water,
inadequate sanitation and poor hygiene
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Health impacts Food Food production may be
undermined in vulnerable regions, not only
directly but also indirectly through pests and
plant or animal diseases. Local declines in
food production could lead to hunger and
malnutrition with long-term health consequences,
especially for children. Food and water
shortages may lead to conflicts or population
displacement in vulnerable regions, with serious
implications for public health.
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Health impacts Heatwaves
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Health impacts Heatwaves

• Individual factors
• Age
• Pre-existing disease chronic respiratory or
  cardiovascular diseases, mental illness
• Use of certain drugs, e.g. Phenothiazines,
  antidepressents, diuretics
• Lack of fitness.
• Social factors
• Living alone
• Type of care provided
• Access to transport.
• Environmental factors
• building type, which floor, cooling facilities
• Climate factors
• Air masses
• High minimum temperature

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Health impacts Vectors Changes in climate may
alter the distribution of important vector
species (e.g. mosquitoes) and may increase the
spread of disease to new areas which lack a
strong public health infrastructure. Highland
populations (such as in East Africa or Papua New
Guinea) that fall outside areas of stable endemic
malaria transmission may be particularly
vulnerable to increases in malaria due to climate
warming. The seasonal transmission and
distribution of many other diseases transmitted
by mosquitoes (dengue, yellow fever) and by
ticks (Lyme disease, tick-borne encephalitis)
may also be affected by climate change.
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Climate Change and Human Health Knowledge gaps
and research needs Why should we be
concerned? What do we know about climate change
and health impacts? What are the main knowledge
gaps? How are we responding?
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Pathways by which climate change affects health
Non-health impacts Water resources Agriculture Co
astal areas Species Natural resources Forests
Adaptation measures
Health effects Temperature-related illness and
death Extreme weather- related health
effects Air pollution-related health
effects Water and food-borne diseases Vector-bor
ne and rodent- borne diseases Effects of food
and water shortages Effects of
population displacement
Adaptive capacity
Modulating influences
Mitigative capacity
Driving forces Population dynamics Unsustainabl
e economic development
Mitigation measures

• Human exposures
• Regional weather
• changes
• Heat waves
• Extreme weather
• Temperature
• Precipitation

Contamination pathways Transmission dynamics
Greenhouse gases (GHG) emissions
Climate Change
Natural causes
Health-specific Adaptation measures
Research needs
Evaluation of adaptation
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Infectious diseases Changes in infectious
disease transmission patterns are a likely major
consequence of climate change. The prediction of
future impacts remains a challenge because of
the highly complex causal relationships.
Diarrhoeal diseases
Distal causes
Proximal causes
Infection hazards
Health outcome
Temperature Humidity Precipitation
Survival/ replication of pathogens in
the environment
Consumption of contaminated water
Incidence of mortality and morbidity attributable
to diarrhoea
Contamination of water sources
Consumption of contaminated food
Living conditions (water supply and sanitation)
Contamination of food sources
Contact with infected persons
Food sources and hygiene practices
Vulnerability (e.g. age and nutrition)
Rate of person to person contact
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Main health effects and research areas
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Main health effects and research areas
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Main health effects and research areas
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Main health effects and research areas
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Main health effects and research areas
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Main health effects and research areas
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Main health effects and research areas
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Main health effects and research areas
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Climate Change and Human Health Knowledge gaps
and research needs Why should we be
concerned? What do we know about climate change
and health impacts? What are the main knowledge
gaps? How are we responding?
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Interagency Network on Climate and Health
Programme Focus
Capacity building
Information exchange
Research promotion
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Interagency Network on Climate and Health
Programme Focus
Capacity building
Assisting Member States in a) undertaking
national assessments of climate-induced human
health impacts b) determining and meeting
capacity-building and research needs in order
to identify and address priority areas c)
identifying and implementing adaptation
strategies and preventive and mitigating
measures, designed to effectively reduce adverse
health impacts.
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Interagency Network on Climate and Health
Programme Focus
to serve as the UN-based lead group of
institutions and experts for the guidance of
research programmes on the human health
implications of climate and of global
environmental change, including the impacts of
climate variability, climate change and
stratospheric ozone depletion.
Research promotion
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Three possible research paths

• Heatwaves
• Weather disasters
• Malaria
• Dengue fever
• Diarrhoeal diseases

• Enteric infections (seasonal pattern of summer
  food poisoning
• Vector-borne disease patterns
• Impacts of extreme events (heat waves, floods,
  cyclones)

• Scenario-based modelling for, e.g.
• Cereal grain yields
• Malaria
• Dengue fever

McMichael 2002 WHO/PAHO Conference on Climate
variability and change and their health effects
in the Caribbean
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• Some current activities with a research
  component
• Global Burden of Disease from climate change
• Early health impacts of climate change in Europe
• Guidelines for health impact assessment and
  adaptation
• Book on climate change and health risks and
  responses
• Health impacts in vulnerable groups (e.g. Small
  Island Countries)
• Early warning systems

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How much disease could climate change
cause? Policy makers need to know the approximate
magnitude of health impacts, which are expected
to be the greatest, in which regions, and what
actions are required to minimize such impacts.
Attributable mortality and DALYs for selected
environmental risk factors- 2000
Climate change
Lead exposure
Urban outdoor air pollution
Indoor smoke from solid fuels
Unsafe water, sanitation, and hygiene
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2
0.5
1.5
0
0
0
10
20
30
40
50
60
Million DALYs
Million Deaths
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How much disease could climate change cause?
Burden of disease by region Climate change and
urban air pollution Disability Adjusted Life Year
per million. World Health report 2002.
Climate change Air
pollution
Africa region South-East Asia region Eastern
Mediterranean region Latin America and Caribbean
region Western Pacific region Developed
countries

• Cardio- pulmonary diseases
• Respiratory infections
• Trachea/ bronchus/ lung cancers

• Diarrhoeal diseases
• Malaria
• Unintentional injuries
• Protein-energy malnutrition

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Interagency Network on Climate and Health
Programme Focus
a) provision of information to Member States,
national and international training and research
institutions, and to the public at large, on the
state-of-the-art in the global research effort on
climate and health interactions, their
consequences for population health and for public
health response b) fulfilling clearing house
functions to ensure free access to information
including databases needed for research on
climate variability and climate change on human
health in developing countries.
Information Exchange
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Climate Change and Human Health Risks and
Responses
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• Developing responses in the health sector
• Assessments of vulnerability and adaptation
  options
• Cost-effective (no-regrets) public health
  interventions
• Implementation of preventative actions and
  adaptation strategies
• Communication and public awareness
• "All scientific work is incomplete - whether it
  be observational or
• experimental. All scientific work is liable to
  be upset or modified by
• advancing knowledge. This does not confer upon
  us a freedom to
• ignore the knowledge that we already have, or to
  postpone the action
• that appears to demand at a given time
• Hill, A.B. The environment and disease
• association or causation?
• Proceedings of the Royal
• Society of Medicine
• 58 295-300 (1965).

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Basel University January 2004
Carlos Corvalán Department of
Protection of the Human Environment Sustainable
Development and Healthy Environments