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The Medical and Public Health Impacts of Global Warming A F A c T S H e e T F R o M PH y S I c I A n S F o R S o c I A l R e S P o n S I b I l I T y The Medical and Public Health Impacts of Global Warming A Warming World stress, the body’s ability to shed heat through As scientific evidence continues to mount increased blood circulation and perspiration, that the earth’s climate is rapidly changing, it and thus its ability to maintain temperature bal- is clear that global warming is no longer just a ance, is lost.6 In such cases, death can result. prediction. The 2003 European heat waves resulted in a Rising oceans, stronger hurricanes, pro- surge of heat-related deaths. Across the United longed droughts, and more intense heat waves Kingdom, France, Italy, the Netherlands, Portu- are signs of the already discernable impacts that gal, and Spain, the heat waves that occurred dur- global warming is having worldwide. Global ing the summer of 2003 are estimated to have average surface temperatures have increased by caused at least 22,000 excess deaths, with some about one degree Fahrenheit since the begin- arguing that this figure could be revised upward ning of the 20th century,1 and the five hottest by as much as an astounding 50–100 percent.7 years on record have all occurred within the last In the United States, a seven-day (July14– decade.2 With the atmospheric concentration of 20) heat wave in Chicago during the summer carbon dioxide (CO2) now higher than at any of 1995 resulted in 485 heat-related deaths.8 In point in the last 420,000 years, widespread con- total, 739 excess deaths were reported during sensus within the scientific community points this period, representing a 147 percent increase to the burning of fossil fuels as the primary above baseline levels.8 cause of this warming of the planet.3 Unless These figures demonstrate the potentially emissions of heat-trapping greenhouse gases devastating impact that could result from an are reduced, temperatures will increase by an increase in heat wave frequency and intensity. additional 2.5 to 10.4 degrees Fahrenheit during Though heat waves normally affect broad geo- the next 100 years—a rate likely to be without graphic regions and resident populations, certain precedent in the last 10,000 years.1 groups are particularly vulnerable. The very old Beyond the serious and potentially irrevers- and the very young tend to have reduced heat- ible impacts on physical and biological systems,4 regulating mechanisms and are at increased a growing body of research also suggests that risk.6 The poor, the socially isolated, and those global warming will adversely affect public already suffering from chronic illness also are health in a number of important ways. likely to be disproportionately affected by an increase in heat wave frequency and severity.6 Heat-Related Illness Climate models predict that North American Air Pollution-Related Health Impacts heat waves will increase in intensity, frequency, While both air pollutant emissions and and duration as global mean temperatures rise ambient pollutant concentrations have generally over the course of this century.5 Under this fallen since passage of the 1970 Clean Air Act, scenario, the many health problems associ- as recently as 2002 approximately 146 million ated with exposure to extreme and prolonged people in the United States lived in counties that heat—heat cramps, heat syncope (fainting), did not meet air quality standards for at least one heat exhaustion, and heatstroke6—will become regulated pollutant.9 Exposure to air pollution can increasingly common. Heat acclimatization is aggravate chronic respiratory and cardiovascular possible, but in cases of extreme or chronic heat disease, damage lung tissue, lead to premature P h y s i c i a n s f o r S o c i a l Re s p o n s i b i l i t y death, and may even contribute to cancer.10 additional benefit of reducing the adverse health Global warming may exacerbate these problems effects associated with a range of air pollutants. by affecting the concentration, distribution, and There also is growing evidence that rising type of both manmade and natural air pollut- global mean temperatures are impacting both ants.10 Ozone levels, for example, are likely to the timing and abundance of airborne aller- increase because higher temperatures accelerate gens, especially pollen.14 the rate at which ground-level ozone (the main In recent decades, spring flowering, and thus component of smog) is formed.10 While long- the allergenic pollen season, has advanced at term exposure to ozone is linked to the develop- a rate of nearly a day per year.15 In Europe, ment and exacerbation of chronic lung diseases, spring events such as leaf unfolding advanced even short-term exposure to relatively low ozone by six days, while autumn events such as leaf concentrations can cause lung inflammation, coloring have been delayed by nearly five days acutely decreased lung function, and respiratory in the last 35 years.16 Experimental studies have impairment.10 A 2004 study using global warm- demonstrated significant increases in pollen ing and air quality models in the 31-county New production resulting from exposure to in- York metropolitan region projected a median creased CO2 concentrations, while examination increase of ozone-related acute mortality across of recent trends have linked elevated pollen the region of 4.5 percent by the 2050s.11 levels to increases in temperature.14 Addition- Although increasing atmospheric CO2 ally, some studies suggest stronger allergenicity concentrations have no known direct adverse of pollen from trees grown at increased tem- health effects, other byproducts of fossil fuel peratures.17 Patz, et al. warn of the potential combustion, including airborne particulate public health consequences of these changes: matter (PM), sulfur oxides (SOx), and nitrogen “climate change may adversely impact the oc- oxides (NOx), are associated with a number of currence and severity of asthma, the most com- well-established health risks.12 Consequently, a mon chronic disease of childhood, and affect continued rise in CO2 emissions would be mir- the timing or duration of seasonal allergies such rored by a rise in the harmful effects of these as hay fever.”14 Combined with the observed combustion byproducts. doubling of pediatric asthma prevalence within In recognizing the link between CO2 emis- the past twenty years,18 children’s physiologi- sions and PM pollution, Cifuentes et al. estimat- cal and behavioral susceptibility to air pollution ed that adoption of existing, readily acquirable increases their risk of being adversely affected greenhouse gas mitigation technologies would by changes in the concentration and distribu- reduce PM concentrations by 10 percent, thus tion of pollutants.19 avoiding 64,000 premature deaths and 65,000 chronic bronchitis cases through 2020 in four cities alone—New York City, USA; Santiago, Infectious Disease Chile; Mexico City, Mexico; and São Paulo, Since 1976 the world has witnessed not only Brazil.13 These studies demonstrate that actions the emergence of 30 diseases previously un- aimed at mitigating the atmospheric accumula- known to medicine, but also the resurgence of tion of greenhouse gases would have the older diseases such as malaria and cholera, and Forebodings from the Gulf coast The devastation produced by Hurricanes Katrina and hurricanes… has increased markedly since the mid- Rita along the Alabama, Mississippi, and Louisiana 1970s,” warning that “future warming may lead to an coasts has given new urgency to the threats posed by upward trend in tropical cyclone destructive potential.” global warming. Although Hurricane Katrina cannot be specifically attributed to global warming, recent trends Already, more than 1,200 deaths have been reported as a point to a shift toward more intense storms. result of Katrina.42 Public health and rescue workers also have documented numerous cases of respiratory and di- As tropical ocean sea surface temperatures (SSTs) arrheal disease among evacuees and rescue workers. The continue to rise—SSTs increased 0.5 degrees Celsius long-term public health effects of the storm, however, during the last 35 years40—warmer ocean temperatures remain uncertain though considerable. Of particular will increase the total energy available to amplify storm concern are the health threats associated with exposure intensity. According to a study published in the journal to molds in flood damaged structures and the risk posed Science, during the past 35 years the number of hurri- by the toxic residues left behind from the flooding of canes reaching categories 4 and 5 has nearly doubled in chemical facilities and oil refineries along the 100 mile both number and proportion.40 Other investigators have stretch between Baton Rouge and New Orleans known concluded that “the potential destructiveness of as “Cancer Alley.” the redistribution of others, including West years.25 While increasing global temperatures Nile virus.15 While not all of these changes in in- will create heavier precipitation events in some fectious disease transmission patterns are related regions, acceleration of land-surface to global warming, Paul Epstein, MD, of Harvard drying will also mean more frequent, more Medical School’s Center for Health and the Glob- severe drought in others.25 al Environment has warned that “a warming and Death and injury are the direct health im- unstable climate is playing an ever-increasing pacts most commonly associated with extreme role in driving this global emergence, resurgence, weather events. However, the environmental and redistribution of infectious diseases.”20 Fur- hazards left behind by natural disasters such as thermore, in a 2003 report on climate change floods and hurricanes can also have a number and human health, the World Health Organiza- of serious secondary health effects. tion (WHO) concluded that “changes in infec- Water quality would be jeopardized by tious disease transmission patterns are a likely increased heavy rainfalls, especially if preceded major consequence of climate change.”21 by drought, as surface waters became polluted Vector-borne diseases result from infections by runoff carrying human and animal wastes, transmitted to humans primarily by blood feeding pesticides, fertilizers, and other pollutants.29 arthropods such as mosquitoes, ticks, and fleas.22 In the past, outbreaks of water-borne diseases, Most vector-borne diseases exhibit a distinct such as Cryptosporidium and Escherichia coli, seasonal pattern, with weather variables such have been linked to heavy rainfall events.14,30 as temperature and rainfall An analysis of 548 gastro- affecting both the vectors and intestinal outbreaks that the disease-causing pathogens occurred in the United they transmit.23 Mosquitoes, States between 1948 and for example, are very sensi- 1994 showed that 68 per- tive to temperature changes.24 cent of cases were preced- Higher temperature increases ed by very heavy rainfall.31 their rate of reproduction, the Threats to water quality number of blood meals they from increased precipita- take, prolongs their breed- tion would be compound- ing season, and shortens the ed by rising temperatures, maturation period for the which promote the growth pathogens they carry.24 Rising of disease-causing bacteria. global temperatures could In the ocean, the combi- also result in the expansion of vector ranges into nation of rising surface water temperatures and areas with previously unexposed populations.14 increased nutrient loading from rivers carrying The 1999 outbreak of West Nile virus (WNV) in agricultural runoff may contribute to increased New York in which seven people died,20 and the harmful blooms of algal species capable of pro- subsequent expansion of the disease in the ducing biotoxins.29 The consumption of fish and summer of 2002, when 230 animal species were shellfish contaminated by these toxins can result infected and cases of human or animal WNV in neurological damage, respiratory irritation, were reported in 44 states and the District of skin irritations, and gastrointestinal illness.32 Columbia,24 exemplify what may occur more Water quantity also may become an issue as regularly as global warming progresses. a result of global warming. Droughts, decreased winter snow-packs, earlier snowmelt, and a extreme Weather events and shift to less frequent but more intense precipi- Water-Related Health Impacts tation events could all put a strain on freshwa- ter resources.29 As water supplies decline, con- Evidence indicates that extreme weather centrations of human waste, animal waste, and events such as heavy precipitation, floods, other pollutants increase while stagnant waters droughts, and hurricanes have increased in provide breeding ground for disease vectors.33,34 frequency, intensity, and duration over the past Poor, developing nations in southern and west century1,25,26,27 and climate models predict that Africa and in the Middle East are at particular this trend will continue as global warming con- risk to increased water stress and may experi- tinues.4 Even if rain becomes less frequent, many ence a rise in the incidence of water-related areas throughout the United States will experi- diseases as people are forced to rely on increas- ence heavier downpours.28 The annual number ingly contaminated sources of fresh water for of days with precipitation exceeding two to four all of their daily needs—drinking, cooking, inches has already increased in the past 100 bathing, and irrigation.30 Addressing Global Warming: total electricity generation of the entire U.S.39 Solar energy is another renewable energy source A Public Health Imperative capable of making a significant contribution to The evidence base for global warming meeting U.S. energy needs. While the current has grown stronger since the United Nations economics of solar energy are constrained, costs Intergovernmental Panel on Climate Change have steadily fallen in the past 20 years. Ad- (IPCC) released its first scientific assessment of ditionally, as the materials to construct solar global warming. The World Health Organization panels become cheaper and more efficient, as (WHO) estimates more than 150,000 deaths production methods improve, and as installa- and approximately 5 million ‘disability-adjusted tion becomes easier, solar energy is expected life years’ (DALYs) annually as a result of in- to become cost-competitive with conventional creasing incidences of disease and malnutrition electricity production in the near future. Also caused by global warming.35 The public health holding enormous potential for renewable impacts are expected to get worse, with climate energy production is the harnessing of both models projecting a doubling of climate-linked geothermal heat energy and ocean tides and disease burden by the year 2030 without currents for electricity generation. regulatory action.35 Automobiles are the second largest source of With new data indicating that sea ice loss U.S. greenhouse gas emissions.38 Thus, a signifi- in the Arctic and Antarctic is accelerating and cant increase in the fuel economy of cars and climate experts now warning that the Earth may trucks is another essential component of any be fast approaching a climate change tipping strategy to curb global warming. Fortunately, point, it is clear that we can no longer afford hybrid engines, flex-fuel vehicles capable of to delay action. To stabilize the earth’s climate running on ethanol, and biodiesel engines are and avoid the most serious public health and all gaining in popularity and commanding an environmental impacts, we must reduce our increasing share of the automotive market. greenhouse gas emissions by 80 percent below Increased automotive efficiency not only helps to 1990 levels.36 This can be achieved by develop- slow global warming, but also reduces the emis- Physicians ing new, cleaner, and more efficient ways of sion of harmful air pollution, all while saving for social producing energy, transportation, and goods. consumers money at the gas pump. As a result of resPonsibility The fastest and most affordable way to curb increased purchases of minivans, pickup trucks, greenhouse gas emissions is to increase energy and SUVs, the current average fuel economy of 1875 Connecticut Ave., NW efficiency. Replacing older home appliances America’s passenger vehicle fleet is at its low- Suite 1012 Washington, DC 20009 such as refrigerators and washing machines est point since the early 1980s and is far behind with more efficient models; improving heat- that of the European Union, Japan, and China. (202) 667-4260 ing and cooling systems; better insulating both Existing technology is capable of nearly doubling Fax (202) 667-4201 commercial and residential buildings; and re- the average fuel economy of America’s cars, and Web www.psr.org placing old lighting systems with new advanced even more significant improvements are pos- lighting systems that use compact fluorescent sible in the near future as existing technologies For more information, contact or LED bulbs—all these actions can drastically mature and as new technologies such as fuel Will Callaway reduce energy use without having to sacrifice cells enter the market. By providing the appro- Legislative Director functionality or comfort. In fact, Amory Lovins priate incentives to both auto manufacturers and E-mail email@example.com of the Rocky Mountain Institute estimates that consumers, policymakers can ensure that these 75 percent of total electricity consumption in technologies continue to grow in market share the U.S. could be displaced by more widespread and can lessen America’s need for oil while dras- use of the best electricity-saving technologies.37 tically reducing the transportation fuel sector’s Because the electric power industry is the contribution to global warming. single largest source of greenhouse gas emis- Though the task before us is formidable, we sions in the U.S.,38 the generation of electricity already possess the scientific, technical, and using renewable energy technologies holds great industrial know-how to greatly reduce global potential for drastically reducing global warming warming pollution. Scientists warn, however, pollution. Wind energy already is cost-competi- that the window of opportunity is closing quick- tive with new coal and gas-fired power plants, ly and we must begin to curb global warming and the U.S. has tremendous potential for emissions within the next ten years to prevent US Affiliate of International generating wind energy. In twelve states alone the worst impacts from occurring. The time for Physicians for the Prevention (North Dakota, Texas, Kansas, South Dakota, action to stop global warming is NOW! of Nuclear War Montana, Nebraska, Wyoming, Oklahoma, Min- For all references, please visit the Publications and nesota, Iowa, Colorado, and New Mexico), wind Resources page of the PSR website at http://www.psr. turbines could produce as much as 2.6 times the org/site/PageServer?pagename=enviro_resources.
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