“Climate Change is the Biggest Global Health Threat of the 21st Century”

Contrary to what some U.S. Senators believe—who last week (10 June 2010) tried to overturn the EPA’s scientific finding that climate change poses a threat to human health and welfare—climate change is a significant hazard to human health. In May 2009, a leading medical journal, The Lancet, called climate change “the biggest global health threat of the 21st century.” The article, “Managing the health effects of climate change,” states that, “[e]ffects of climate change on health will affect most populations in the next decades and put the lives and wellbeing of billions of people at increased risk.”

While health impacts fall disproportionally on poor and developing countries due to geography and lack of resources, the United States will not be immune from the effects. In fact, two recent federal reports outline the potential public health hazards to U.S. citizens from a changing climate:

• Global Climate Change Impacts in the U.S. By the U.S. Global Change Research Program (USGCRP), June 2009.
• A Human Health Perspective on Climate Change. By the U.S. government's Interagency Group on Climate Change and Health.  April 2010. Published by Environmental Health Perspectives (EHP) and the National Institute of Environmental Health Sciences.

Below are 9 categories of human health impacts from the 2 reports.

1. Air Quality Decline—Asthma, Respiratory Allergies and Airway Diseases
Human-induced climate change is predicted to increases exposure to air pollution, pollen, dust, and molds. “Higher temperatures are projected to increase the frequency, intensity and duration of conditions conducive to air pollution formation” (USGCRP). Ground-level ozone is a major component of this due to its interaction with temperature. This will be especially problematic in urban areas where condense populations and automobile usage increases the levels of concentrated pollution. Higher temperatures not only intensify air pollution but also pollen production, potentially generating more asthma. Increases in atmospheric carbon dioxide (most abundant U.S. greenhouse gas pollution) concentrations are also projected to raise pollen counts. Amplified mold and dust exposure may result from extreme or more frequent precipitation and drought increases. 

Pollen Counts Rise with Increasing Carbon Dioxide

Pollen production from ragweed grown in chambers at the carbon dioxide concentration of a century ago (about 280 parts per million [ppm]) was about 5 grams per plant; at today’s approximate carbon dioxide level, it was about 10 grams; and at a level projected to occur about 2075 under the higher emissions scenario, it was about 20 grams. ©USGCRP

2. Cardiovascular Disease and Stroke
“Climate change may exacerbate existing cardiovascular disease by increasing heat stress, increasing the body burden of airborne particulates, and changing the distribution of zoonotic vectors that cause infectious diseases linked with cardiovascular disease” (EHP).

3. Foodborne Diseases and Nutrition
“Climate change may be associated with staple food shortages, malnutrition, and food contamination (of seafood from chemical contaminants, biotoxins, and pathogenic microbes, and of crops by pesticides)” (EHP).

4. Heat Related Mortality or Disease
With rising temperatures, "the risk of illness and death related to extreme heat and heat waves are very likely.” (USGCRP). The aging population is especially vulnerable and this demographic is increasing. In the future, rare extreme heat waves will be more common, affecting disproportionally major U.S. cities due to the urban heat island effect. Projections for Chicago suggest heat wave deaths could more than double or even quadruple by 2050, depending on emission levels.

Projected Increase in Heat-Related Deaths in Chicago

©USGCRP

               Number of Days Over 100°F

©USGCRP

5. Mental Health and Stress-Related Disorders
“By causing or contributing to extreme weather events, climate change may result in geographic displacement of populations, damage to property, loss of loved ones, and chronic stress, all of which can negatively affect mental health” (EHP).

6. Disease Risk Increase
Disease risk may increase due to disruption and relocation of large populations from climate change or from expanded pathogen range and shortened incubation period of the disease vector. Some of these diseases may currently only be associated with areas outside the U.S. but changing temperatures may make U.S. regions suitable for survival and transmission.

7. Weather-Related Mortality and Disease
Extreme weather events such as hurricanes, wildfires, floods and droughts are projected to increase in number and intensity. These may cause death or impact people’s health during and/or following the event. 

The pie chart shows the distribution of deaths for 11 hazard categories as a percent of the total 19,958 deaths due to these hazards from 1970 to 2004. Heat/drought ranks highest, followed by severe weather, which includes events with multiple causes such as lightning, wind, and rain. This analysis ended prior to the 2005 hurricane season which resulted in approximately 2,000 deaths. ©USGCRP

8. Waterborne Diseases
“Increases in water temperature, precipitation frequency and severity, evaporation-transpiration rates, and changes in coastal ecosystem health could increase the incidence of water contamination with harmful pathogens and chemicals, resulting in increased human exposure” (EHP).

9. Human Developmental Effects
“Two potential consequences of climate change would affect normal human development: malnutrition—particularly during the prenatal period and early childhood as a result of decreased food supplies, and exposure to toxic contaminants and biotoxins—resulting from extreme weather events, increased pesticide use for food production, and increases in harmful algal blooms in recreational areas” (EHP).

Geographic Vulnerabilities of U.S. Residents to Selected Climate-Related Health Impacts

Maps indicating U.S. counties, or in some cases states, with existing vulnerability to climate-sensitive health outcomes. ©USGCRP

More research is needed for improving the understanding of climate change’s impact on public health and methods for preparation and risk reduction. However, it is clear that climate change will pose a formidable health challenge in the coming years/decades with major efforts needed for reducing climate change pollution. 

More recently, the National Research Council (NRC) has addressed health impacts -- and the need to prepare for them -- in reports published as part of its project on America's Climate Choices.  In Advancing the Science of Climate Change, the NRC warns:

"Responses to recent extreme weather and climate events such as Hurricane Katrina show that even in the United States, current levels of adaptation are insufficient. Substantial inequities exist in access to public heath infrastructure, both in the United States and elsewhere, so health risks will be disproportionately high for the poor, elderly, and otherwise disadvantaged. Additionally, analysis has shown that without further investment, the public health infrastructure most important for addressing the challenges of climate change could be insufficient. Concerted efforts are needed to reduce vulnerability of populations in both this country and the world, particularly the poorest and most marginalized."

Sources Cited:

• U.S. Global Change Research Program (USGCRP). “Global Climate Change Impacts in the United States.” June 2009.
• Environmental Health Perspectives (EHP) & the National Institute of Environmental Health Sciences. “A Human Health Perspective on Climate Change.” April 2010.

Other Sources:

• Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems (2008).  U.S. Global Change Research Program,  Synthesis and Assessment Product 4.6. 

Related WWF Blog Postings:

• Climate Change Will Likely Worsen Allergies, Says New Report (14 April 2010)
• The Spread of Disease & Pests from Climate Change (6 April 2010)
• Clean Air Act Under Attack (8 June 2010)