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msJAMA |

Global Climate Change and Health: Challenges for Future Practitioners FREE

Jonathan A. Patz, MD, MPH; Mahmooda Khaliq
JAMA. 2002;287(17):2283-2284. doi:10.1001/jama.287.17.2283-JMS0501-3-1.
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Published online

Global climate change is expected to have broad health impacts.1 If current warming trends continue, heat waves, floods, and droughts and their attendant physical effects are likely to become more frequent and severe. Warmer air temperatures can influence the concentration of regional air pollutants and aeroallergens. Less direct health impacts may result from the disruption of ecosystems and of water and food supplies, which in turn could affect infectious disease incidence and nutritional status. Finally, sea-level rise could lead to major population displacement and economic disruption.

Human activities related primarily to the burning of fossil fuels and changes in land cover such as deforestation are changing the concentration of atmospheric constituents or properties of the earth's surface that help to absorb or scatter radiant energy.2 Since the preindustrial mid-1800s, increases in concentrations of three major greenhouse gases, carbon dioxide, methane, and nitrous oxide, have exceeded past changes that occurred over the last 10 000 years; carbon dioxide alone has increased by 30% since the late 1800s.1 Warmer air, such as that resulting from the greenhouse effect, can hold more moisture and more quickly evaporate surface water, thereby increasing the frequency of severe storms, floods, and droughts.1

According to the United Nations Intergovernmental Panel on Climate Change (IPCC), "An increasing body of observations gives a collective picture of a warming world and other changes in the climate system."3 During the 20th century, global average surface temperature increased about 0.6°C, global average sea level rose 10 cm to 20 cm, and snow and ice cover decreased.2 The latest IPCC report predicts that if current trends continue, sea level rise will rise 45 cm and global temperatures will increase by 3°C by the year 2100.3

Small changes in global mean temperatures can produce relatively large changes in the frequency of extreme temperatures.2 Mortality rates increase at both hot and cold extremes of temperature.4 Increases in temperature have a direct and substantial impact on excess mortality for elderly individuals and individuals with pre-existing illnesses. Much of the mortality attributable to heat waves is a result of cardiovascular, cerebrovascular, and respiratory disease.5 A 1995 heat wave in Chicago that caused 514 heat-related deaths (12 per 100 000 population)6 may be part of a recent trend of longer, more frequent heat waves and record-setting temperatures.7 Long-term global warming trends are further exacerbated by the "heat island" effect, whereby high concentrations of heat-retaining surfaces such as asphalt and tar roofs sustain higher temperatures through the night. Heat waves also have the secondary effect of worsening urban air pollution. Ozone, which forms chemically from precursor pollutants, is the most temperature-dependent air pollutant and may contribute to the development of asthma in children.8

Higher average ambient air temperatures are likely to induce more vigorous cycles of evaporation and precipitation. Indeed, a trend of increasing climate variability and extreme precipitation events has been observed over the past century, and recent models strongly correlate this trend with anthropogenic production of greenhouse gases. 9,10

Human health impacts are most likely to occur where extreme weather and population vulnerability converge. At highest risk are communities that are most exposed (eg, in floodplains and coastal zones) and that have the fewest technical and social resources.11 The health impacts of extreme weather events include physical injury; poorer nutritional status, especially in children; increases in respiratory and diarrheal diseases due to overcrowding of flood survivors and limited access to potable water; increased risk of water-related diseases due to disruption of water supply or sewage systems; and release of dangerous chemicals from storage sites and waste disposal sites into flood waters.11,12

El Niño

An El Niño occurs approximately every 3 to 7 years when warm equatorial water shifts from the western to eastern Pacific Ocean.13 The 1997-1998 El Niño event was one of the two strongest of the past century. It was associated with extremely dry conditions and devastating fires in many areas of the world and with extensive flooding in others.14

Some infectious diseases that are typically seasonal have shown marked interannual variability. Many epidemics of malaria are associated with El Niño–driven climate extremes. 15 The 1997-1998 El Niño resulted in torrential rain in parts of East Africa and a subsequent malaria epidemic in the highlands of southwestern Uganda.16

Floods

Climate change may increase the risk of both river and coastal flooding, whose immediate effects include drowning and physical trauma.17 Longer-term effects include increases in communicable diseases such as those caused by ingestion of contaminated water (eg, cholera and hepatitis A) or contact with contaminated water (eg, leptospirosis). Respiratory infections may result from overcrowding of settlements or from overgrowth of molds in flooded homes.17

Droughts

Droughts have their largest impact on population health by threatening food supplies. In addition, diarrheal diseases, scabies, conjunctivitis, and trachoma are associated with poor hygiene and may result from inadequate sanitation as water resources become depleted.14Drought-induced wildfires can cause direct injury and have the potential to affect air quality. During the 1997-1998 El Niño, biomass smoke from drought-exacerbated fires in Indonesia affected large population centers in southeast Asia. In some areas, smoke concentrations were more than six times higher than the ambient air quality standards outlined by the US Environmental Protection Agency.18

Waterborne diseases in marine or coastal zones are especially sensitive to climate. During the 1997-1998 El Niño, the number of daily hospital admissions in Lima, Peru, for childhood diarrhea increased more than two fold over the averaged rate for the preceding four years.19 The increase in ambient temperature in excess of regular seasonal variability was found to be the main environmental variable affecting admissions: for each 1°C increase in mean ambient temperature, the number of admissions increased by 8%. Cholera outbreaks occur seasonally in Bangladesh, with consistent patterns associated with monsoon seasons, sea-surface temperatures, rainfall, and zooplankton populations.20 In the marine environment, warm water and nitrogenous waste favor blooms of dinoflagellates. The resulting "red tides" can cause paralytic, diarrheic, and amnesiac shellfish poisoning.14 Finally, certain vector-borne pathogens, such as those that spend a part of their life cycle in arthropod vectors, are sensitive to ambient temperatures.21

Global mean sea level is predicted to continue to increase primarily by the loss of mass from glaciers and thermal expansion of water. Sea-level rise would especially affect coastal communities and, in some cases, may force population migration.21 Thirteen of the world's 20 major metropolises are situated at sea level. Nicholls and Leatherman showed that a 1-meter rise in sea level would inundate low-lying areas, affecting 18.6 million people in China, 13 million in Bangladesh, 3.5 million in Egypt, and 3.3 million in Indonesia.22 Furthermore, rising seas may salinate coastal freshwater aquifers and disrupt stormwater drainage and sewage disposal.23 Considering the health burden experienced by refugees and populations subjected to overcrowding, lack of shelter, and competition for resources, the response to displaced populations may well become the largest public health challenge posed by global climate change.

Acknowledgment: We thank Jolie Susan for her help with manuscript preparation and editing. Partial funding support for Dr Patz comes from the US EPA Global Change Research Program, cooperative agreement CR 827040.
Patz  JAEngelberg  DLast  J The effects of changing weather on public health. Ann Rev Public Health. 2000;21271- 307
Link to Article
Intergovernmental Panel on Climate Change (IPCC), Climate Change 2001: The Scientific Basis: Contribution of Working Group I to the Third Assessment Report of the IPCC. Houghton  JDing  YGriggs  M  et al. eds. Cambridge, England Cambridge University Press2001;
McMichael  A Human health. IPCC Working Group II,ed.Climate Change 2001: Impacts, Adaptation, and Vulnerability Cambridge, England Cambridge University Press2001;453- 485
Curriero  FCHeiner  KSSamet  JM  et al.  Temperature and mortality in 11 cities of the eastern United States. Am J Epidemiol. 2002;15580- 87
Link to Article
Kilbourne  E Heat waves. Noji  Eed.The Public Health Consequences of Disasters New York, NY Oxford University Press1997;51- 61
Whitman  SGood  GDonoghue  ER  et al.  Mortality in Chicago attributed to the July 1995 heat wave. Am J Public Health. 1997;871515- 1518
Link to Article
Gaffen  DJRoss  RJ Increased summertime heat stress in the US. Nature. 1998;396529- 530
Link to Article
McConnell  RBerhane  KGilliland  F  et al.  Asthma in exercising children exposed to ozone: a cohort study. Lancet. 2002;359386- 391
Link to Article
Karl  TRKnight  RWPlummer  N Trends in high-frequency climate variability in the twentieth century. Nature. 1995;377217- 220
Link to Article
Milly  PCWetherald  RTDunne  KADelworth  TL Increasing risk of great floods in a changing climate. Nature. 2002;415514- 517
Link to Article
Noji  E The nature of disaster: general characteristics and public health effects. Noji  Eed.The Public Health Consequences of Disasters New York, NY Oxford University Press1997;3- 20
McMichael  AJHaines  ASlooff  RKovats  S Climate Change and Human Health: An Assessment Prepared by a Task Group on Behalf of the World Health Organization, the World Meteorological Organization, and the United Nations Environment Programme.  Geneva, Switzerland World Health Organization1996;
Ropelewski  CHalpert  M Global and regional scale precipitation patterns associated with the El Niño/Southern Oscillation. Monthly Weather Rev. 1987;1151606- 1626
Link to Article
Patz  J Public health risk assessment linked to climatic and ecological change. Human and Ecological Risk Assessment. 2001;71317- 1327
Link to Article
Bouma  MPoveda  GRojas  W Predicting high-risk years for malaria in Colombia using parameters of El Niño Southern Oscillation. Trop Med Int Health. 1997;21122- 1127
Link to Article
Kilian  ALangi  PTalisuna  A Rainfall pattern, El Niño, and malaria in Uganda. Trans R Soc Trop Med Hyg. 1999;9322- 23
Link to Article
Malilay  J Floods. Noji  Eed.The Public Health Consequences of Disasters New York, NY Oxford University Press1997;287- 301
Brauer  M Health impacts of biomass air pollution. WHO Workshop on Health Impacts of Haze-Related Air Pollution June1- 41998; Kuala Lumpur Malaysia
Checkley  WEpstein  LDGilman  RH  et al.  Effects of El Niño and ambient temperature on hospital admissions for diarrhoeal diseases in Peruvian children. Lancet. 2000;355442- 450
Pascual  MRodo  XEllner  SPColwell  RBouma  MJ Cholera dynamics and El Niño-Southern Oscillation. Science. 2000;2891766- 1769
Link to Article
Gobler  DJRenter  PEbi  KLYap  WNusci  RPatz  JA Climate variability and change in the United States. Environ Health Perspect. 2001;109 ((suppl 2)) 223- 243
Link to Article
Myers  NKent  J Environmental Exodus: An Emergent Crisis in the Global Arena.  New York, NY Climate Institute1995;
Nicholls  RLeatherman  S Global sea-level rise. Strzepek  KSmith  Jeds.As Climate Changes: International Impacts and Implications New York, NY Cambridge University Press1995;92- 123

Figures

Tables

References

Patz  JAEngelberg  DLast  J The effects of changing weather on public health. Ann Rev Public Health. 2000;21271- 307
Link to Article
Intergovernmental Panel on Climate Change (IPCC), Climate Change 2001: The Scientific Basis: Contribution of Working Group I to the Third Assessment Report of the IPCC. Houghton  JDing  YGriggs  M  et al. eds. Cambridge, England Cambridge University Press2001;
McMichael  A Human health. IPCC Working Group II,ed.Climate Change 2001: Impacts, Adaptation, and Vulnerability Cambridge, England Cambridge University Press2001;453- 485
Curriero  FCHeiner  KSSamet  JM  et al.  Temperature and mortality in 11 cities of the eastern United States. Am J Epidemiol. 2002;15580- 87
Link to Article
Kilbourne  E Heat waves. Noji  Eed.The Public Health Consequences of Disasters New York, NY Oxford University Press1997;51- 61
Whitman  SGood  GDonoghue  ER  et al.  Mortality in Chicago attributed to the July 1995 heat wave. Am J Public Health. 1997;871515- 1518
Link to Article
Gaffen  DJRoss  RJ Increased summertime heat stress in the US. Nature. 1998;396529- 530
Link to Article
McConnell  RBerhane  KGilliland  F  et al.  Asthma in exercising children exposed to ozone: a cohort study. Lancet. 2002;359386- 391
Link to Article
Karl  TRKnight  RWPlummer  N Trends in high-frequency climate variability in the twentieth century. Nature. 1995;377217- 220
Link to Article
Milly  PCWetherald  RTDunne  KADelworth  TL Increasing risk of great floods in a changing climate. Nature. 2002;415514- 517
Link to Article
Noji  E The nature of disaster: general characteristics and public health effects. Noji  Eed.The Public Health Consequences of Disasters New York, NY Oxford University Press1997;3- 20
McMichael  AJHaines  ASlooff  RKovats  S Climate Change and Human Health: An Assessment Prepared by a Task Group on Behalf of the World Health Organization, the World Meteorological Organization, and the United Nations Environment Programme.  Geneva, Switzerland World Health Organization1996;
Ropelewski  CHalpert  M Global and regional scale precipitation patterns associated with the El Niño/Southern Oscillation. Monthly Weather Rev. 1987;1151606- 1626
Link to Article
Patz  J Public health risk assessment linked to climatic and ecological change. Human and Ecological Risk Assessment. 2001;71317- 1327
Link to Article
Bouma  MPoveda  GRojas  W Predicting high-risk years for malaria in Colombia using parameters of El Niño Southern Oscillation. Trop Med Int Health. 1997;21122- 1127
Link to Article
Kilian  ALangi  PTalisuna  A Rainfall pattern, El Niño, and malaria in Uganda. Trans R Soc Trop Med Hyg. 1999;9322- 23
Link to Article
Malilay  J Floods. Noji  Eed.The Public Health Consequences of Disasters New York, NY Oxford University Press1997;287- 301
Brauer  M Health impacts of biomass air pollution. WHO Workshop on Health Impacts of Haze-Related Air Pollution June1- 41998; Kuala Lumpur Malaysia
Checkley  WEpstein  LDGilman  RH  et al.  Effects of El Niño and ambient temperature on hospital admissions for diarrhoeal diseases in Peruvian children. Lancet. 2000;355442- 450
Pascual  MRodo  XEllner  SPColwell  RBouma  MJ Cholera dynamics and El Niño-Southern Oscillation. Science. 2000;2891766- 1769
Link to Article
Gobler  DJRenter  PEbi  KLYap  WNusci  RPatz  JA Climate variability and change in the United States. Environ Health Perspect. 2001;109 ((suppl 2)) 223- 243
Link to Article
Myers  NKent  J Environmental Exodus: An Emergent Crisis in the Global Arena.  New York, NY Climate Institute1995;
Nicholls  RLeatherman  S Global sea-level rise. Strzepek  KSmith  Jeds.As Climate Changes: International Impacts and Implications New York, NY Cambridge University Press1995;92- 123

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