Global Warming & its Effect on Human Health

• Global warming impacts our health

Objectives for the day:

• Defining global warming
• Exploring the effects of global warming on the economy and human health
• Identifying the causes of global warming
• Discussing possible adaptations to global warming

Average Global Temperatures Since 1850

• Graph showing the difference in global average near-surface temperatures relative to the long-term average since 1850
• Graph indicates a clear warming trend

Potential Impacts of Climate Change on Human Health

• Climate change effects like rising temperature, sea level, and altered precipitation can lead to:
  • Heat-related morbidity and mortality
  • Morbidity, mortality, displacement, from storms and coastal flooding
  • Infectious diseases spread by vectors
  • Respiratory diseases from air pollutants
  • Malnutrition from disrupted food supply
  • Morbidity/mortality/displacement due to civil conflict

Effects of global warming on health:

• Increases in malnutrition
• Increased deaths, disease, and injury from extreme events like heat waves, floods, storms, fires, and droughts also likely
• Increased burden of diarrheal disease Frequency of cardio-respiratory diseases increases due to higher ground-level ozone
• Altered spatial distribution of infectious disease vectors

Greenhouse Effect

• The Earth acts like a greenhouse, where energy from the sun penetrates the atmosphere.
• This warms the air and surface, with certain gases slowing heat from escaping, thus raising temperatures.

Carbon Dioxide

• Human activities have significantly increased atmospheric carbon dioxide concentrations.
• CO2 levels have risen from 280 parts per million (ppm) to 383 ppm
• The highest levels in more than 650,000 years

What causes CO2 levels to increase

• Burning fossil fuels in homes, factories, and automobiles
• Transferring carbon dioxide from lithospheric reservoirs to the atmosphere
• Deforestation reduces the biosphere's ability to absorb carbon due to forests serving as sinks for active carbon

Explanation of Global Warming

• There was a balance between CO2 from humans/animals and CO2 absorbed by trees, and between O2 given off by trees and O2 used by humans/animals
• Now, increased greenhouse gases from human activity enhance this effect, leading to more trapped heat and global warming.

Health benefits of milder winters:

• Reduced deaths from influenza or cardiovascular disease in temperate countries
• Mosquito populations may recede in areas becoming more arid

Immediate and direct risks of global warming:

• Health impacts of heatwaves
• Extreme weather events
• Altered air quality, especially increased concentrations of ground level ozone
• The human body's ability to cope with thermal stress will be exceeded
• Older people, those with underlying cardiovascular or chronic respiratory disease, the poor, uneducated, or isolated are particularly vulnerable

Indirect risks of global warming

• Greater absolute burden of adverse health impact from heat waves will be in the general community
• Workers in various heat exposed workplaces, both outdoors and unventilated indoors, are particularly vulnerable
• Changes and disruptions to ecological and biophysical systems
• Affecting food yields
• Altering the production of aeroallergens (spores and pollens)
• Affecting bacterial growth rates
• Impacting the range and activity of disease vectors(mosquitoes)
• Impacting water flows and quality
• Rising temperatures reduce the solubility of gases (such as oxygen) in water
• Oxygen concentrations at saturation falls 10% with a 3°C increase
• Fish stock density may reduce
• Ocean fishery harvests are affected by the adverse impacts of acidification
• Acidification is caused by increased uptake of carbon dioxide from the atmosphere) on the vitality of the marine food web base
• Crop and livestock yields are more sensitive to climatic changes than previously thought
• Yields are impaired by relatively small changes in growing season temperatures.
• Rising temperatures affect rice production

Human Health and Agriculture

• Agriculture is the main source of income and food for the majority of countries
• Projected number of starving people worldwide is expected to be 40-300 million in addition to the 600 million already projected to be starving in 2060

Infectious Diseases and Temperature

• Changes in climatic conditions affect climate-sensitive infectious diseases via:
  • Influences on pathogen maturation and multiplication.
  • Influences on vector organism density and behaviour (such as the mosquito)
  • The ecology and density of reservoir (intermediate) host species.
  • Aspects of human behaviour amplifying the risks of infection (such as crowding and displacement)
  • Cases of campylobacteriosis, and infection with Salmonella Typhimurium and Salmonella Enteritidis rise with temperature

Vector Organisms

• Changes in the distribution and life cycle of vector organisms will also occur, as with those of their transmitted pathogens
• Changes in malaria, schistosomiasis and leishmaniasis are expected, as well as in dengue fever and infections by other arboviruses
• Geographical distribution and timing of these changes are difficult to predict.
  • A short term increase in temperature and rainfall associated with the 1997-98 El Niño caused Plasmodium falciparum malaria epidemics in Kenya, but reduced malaria transmission in Tanzania
  • Malarial zones have apparently extended to higher altitudes in western Kenyan highlands
• The schistosomiasis water snail survival zone has extended northwards in eastern China

Infectious Diseases

• Cholera is a parasitic disease which can cause death from dehydration.
• Excessive diarrhea is a symptom
• Dengue fever is transmitted by mosquitoes
  • Symptoms include fevers, joint and muscle pain, and headaches

Malaria and temperature

• Malaria can currently affect 45% of the world's population
• If global warming continues at the current rate, this could increase to 60%
• Dengue's principal vector mosquito is female Aedes aegypti
• Infected mosquitoes remain infective for life
• Indonesia: reported dengue cases doubled in 2007 vs. 2005,

Effects of Temperature Rise on Dengue Transmission

• Shortened viral incubation period in mosquito
• Shortened breeding cycle of mosquito
• Increased frequency of mosquito feeding
• More efficient transmission of dengue virus from mosquito to human

Global Rise in Dengue Cases

• There has been a thousand-fold increase in the global rise in dengue cases reported annually

Schistosomiasis

• Schistosomiasis is a tropical disease caused by infestation with schistosomes.
• It is widespread in rural areas of Africa, Asia, and Latin America
• It is contracted through use of contaminated water
• Schistosomiasis is characterized by infection and gradual destruction of the tissues of the kidneys, liver, and other organs
• Also called bilharziasis, snail fever.
• A northward extension of Schistosomiasis is occurring as a result of rising average January temperatures since 1960
• The northward extension of 'freeze line', which is limited to survival of water snails, puts 21 million extra people at possible risk

Climate-related Impacts

• Climate change results in higher rates of evapotranspiration, glacier melting, increased evaporation and increased variability in perception
• More pressure on groundwater, more frequent periods of soil affects crops, increased demand for irrigation water and longer time affecting water usage for industries
• Increased water contamination, changes in rainfall and temperature may extend and intensify exposure to allergenic pollen and spores from plants such as ragweed

Deferred and Diffuse Risks

• Include those associated with rural to urban displacement, drought affecting rural areas
• In Australia, following a severe weather event, 1 in 5 experienced stress affecting the work force
• Children are vulnerable to pre/post disaster anxiety

Risks associated with conflicts, environmental refugee flows

• Disease, starvation, drought are powerful drivers
• The chance of civil war breaking out doubled due to warmer spells

Responding to Climate Change and Health

• The health sector should play a central role in:
• Communicating the health risks of global heating
• Collaborating with other partners
• Promoting, leading, and evaluating range of adaptive strategies
• Protecting the health and safety of the most vulnerable sectors of populations
• Increasing financial contributions by high-income countries to low-income countries,

Achieving Sustainability

• Individual citizen/consumer actions alone can only address ~5% of the problem
• Achieving sustainability needs large-scale(global) environmental and government policy changes
• A cultural transformation is needed
• Global environmental changes arise from systemic market failures

Adaptive Strategies

• Adaptive strategies include:
• Appropriate workforce training and mid-career development
• Public education and awareness
• Early-alert systems
• Community-based neighborhood support/watch schemes
• Climate-proofed housing design; 'cooler' urban layout
• Disaster preparedness (including health-system 'surge' capacity)
• Enhanced infectious disease control programs (vaccines, vector control, case detection, and treatment)