Transcript Climate and Human Health

Outline
• Background
– Human energy balance
– Strategies to temperature changes
• Morbidity
– Heat Waves
– Flooding
– Famine
• Disease
– Malaria
How climate change affects health
IPCC (2007) Working Group 2 Report
Heat Waves
• Associated with short-term increases in
mortality
• Have been increasing in frequency
• Mortality displacement is a factor
– People close to death will die sooner in a heat
wave
– Drop off in deaths after the heat wave
Human Adaptability to Heat
• Humans maintain near constant core
temperature through various adaptive
strategies:
– Physiological (sweating)
– Acclimatization (adjustment to new conditions
over time)
– Alteration of food intake
– Changing when you do things
– Migration
– Clothing
– Use energy for A/C or heating
Human Energy Balance
Metabolic Rate
Longwave Radiation
Evaporation
( M  Q)  R  C  E   S
Incoming shortwave
Convection
Storage
• Storage change = 0 over time to maintain
temperature balance
Clothing Impact
• The “private climate”
• Quantified by estimating the resistance to
thermal transfer:
Body Temp.
I CL
Air Temp.
Incoming short
wave
Body Area
TS  TA M T  Q  q  / AD 


MT
hM T
Metabolic Rate
Dry Heat Flux = 6.6+8.7(wind speed)0.5
Simplified Clothing Index
Acclimatization
• Evidence that some populations have become
less sensitive to temperature extremes
– USA (1964-1988)
– South Carolina (since 1970s)
• Physiological responses include:
– More efficient heat loss through sweat
– Readjustment of temperature preference toward the
extreme values
• Leads to less discomfort, better work
performance, sense of better well being
Flooding and Health Effects
• Large numbers of
fatalities from the
events themselves
– Bangladesh
• Post-event impacts
– Digestive diseases
– Chemical contamination
(e.g. Katrina)
– Mental disorders
(anxiety, depression)
• Higher impacts on poor
– More live in flood prone
areas
Drought
• Diminishes diversity in diet and reduces
overall food consumption
• Malnutrition
– Increases risk of acquiring and dying from
infectious disease
• May cause mass migration (rural to urban)
– Increase in communicable disease
Climate Model Projections
Food Safety
• Studies have shown a linear increase in
food poisoning with increase in
temperature
• Higher temperatures increase contact
between food and pests (flies,
cockroaches, rodents)
• More ocean toxins (Harmful Algal Blooms)
contaminate shellfish
Water Supply
• Water access
already a global
concern
– 2 billion + do not
have access to
clean water
– Leads to disease,
malnutrition, infant
mortality
Water Supply
• Climate extremes (projected to increase)
stress water supply systems
• Lower river flows increases pathogen
proportion
• Extreme rain/runoff events may increase
water borne disease
– Curriero et al. 2001
Vector Borne Diseases
• Transmitted through
bites
– Mosquitoes, ticks, bugs,
some flies
• Tick populations have
shifted north (Sweden,
Canada) and up (Czech
Republic)
• Evidence of earlier
arrival of mosquitoes
Malaria
• 515 million cases each year in tropics and
subtropics
– 1-3 million deaths
• Conflicting results on malaria trends and how
they relate to climate
– Some evidence that high minimum temperatures in
preceding months mean more malaria (Ethiopia)
Future Vulnerability to Climate
Change
• Factors
– Existing burden of disease and disability
– Aging of the population
– Population explosion
• From 6.4 bil to 9 bil by mid-21st century
• Highest in poor countries
– Urbanization
• Heat island effect, more efficient disease transfer
– Socio-economic
• Rich get richer, poor get poorer