HEAT WAVES, THE "OTHER" NATURAL DISASTER: Perspectives on an Often Ignored Epidemic

By Silvia Chiang

Home to one-fourth of the country’s agricultural production and a swelling underclass of migrant farm workers, California’s Central Valley is known for blistering summer temperatures. In July 2006, daytime temperatures consistently shot past 100º F for two weeks, with temperatures reaching 115º F for several consecutive days. The heat lead to the deaths of 50 people in the Central Valley. Most victims were elderly, migrant farm workers, outdoor laborers, and people living alone or in poor housing conditions. To the south, in the Imperial Valley, another heavily agricultural area, many of the dead were migrants living in tents or trailers, sometimes far from any town.

On the other side of the globe, the Indian subcontinent is also accustomed to scorching summers, but in recent years, extreme heat has caused thousands of deaths. Over 1000 people perished in the 2002 heat wave, when temperatures topped 122 degrees. The following year, another heat wave killed over 1600, with some 1200 of those deaths occurring in the southern state of Andhra Pradesh. During the 2005 heat wave, primarily affecting Andhra Pradesh¹, Orissa in India, and neighboring Bangladesh, women, children, and laborers below the poverty line (rickshaw pullers, daily wage laborers, and construction workers) were most vulnerable to death from heatstroke, dehydration, and diarrhea². Although the Indian government had issued heat warnings and strongly advised people to stay indoors during the hottest part of the day, many farmers and outdoor laborers continued to work because they could not afford to lose their desperately needed income.

Other examples of deadly heat waves include Chicago’s 1995 heat wave, which killed 485 people in seven days³ and the 2003 European heat wave, which killed 15,000 people in France and 20,000 people in Italy. In these heat waves, too, poverty and marginalization contributed to higher risk of death. Social mapping showed that most heat-related deaths in Chicago occurred in low-income neighborhoods⁴. An epidemiologic study of four Italian cities showed that during the 2003 heat wave, low socioeconomic groups in at least two of the cities had the greatest percentage of heat-related excess deaths⁵. Worldwide, heat waves are increasing in intensity and frequency; as a result, heat-related casualties will also climb, and the suffering will most likely continue to be disproportionately borne by the poor and the marginalized.

As heat wave mortality has dramatically increased, public health agencies and governments have allocated more resources to combating this often forgotten epidemic. In August 2006, California state officials announced a $4.5 million study that will investigate the effects of extreme heat and global warming on the health of Californians⁶. This announcement was made just weeks following the state’s deadly heat wave. After the heat wave that struck Europe in the summer of 2003, the World Health Organization Regional Office developed EuroHEAT, a collaboration with other agencies to identify risk factors and effective interventions for heat-related health problems. France and Italy, the two hardest hit countries in 2003, have both developed heat response plans that include heat warnings, public education, activation of social and health networks, and epidemiologic data collection.

The study of heat-wave related morbidity and mortality has been stymied by disparities in the classification of heat-wave related mortality by medical examiners, resulting in wide variations in data generated by different localities, even within the U.S. The Medical Examiner of Cook County, Illinois (Chicago) classifies a death to be heat-related if a body temperature of at least 105°F (hyperthermia) is measured at or shortly after the time of death, if there is evidence of high temperature in the place where the body was found, or if the body is found in a decomposed state and was last seen alive at the peak of the heat wave⁷. Another method of estimating heat-related mortality is to take the total number of deaths during a heat wave, regardless of specific criterion, and subtract the average number of deaths for an equal time period during that particular month. The difference between the two figures is the number of excess deaths assumed to be caused by the heat wave. Applying this method to the 1995 Chicago heat wave, the death toll rises from 485 to 739⁸. New York City, on the other hand, uses a narrower definition for heat-related deaths: only those with measurable body temperatures of over 105°F are classified as having died as the result of heat exposure. A death is not counted if another medical condition was the immediate or primary cause of death, even if that condition was exacerbated by the extreme heat⁹. Furthermore, no universal definition of ‘heat wave’ exists. Rather, local areas may generate their own definitions based on temperature, humidity, nighttime temperature, and heat index thresholds, above which significant heat-related problems (including morbidity, mortality, economic loss, and environmental damage) occur.

Although this lack of standardization hinders epidemiologic measurements, it is likely that strict criterion, such as those employed by New York City, underestimate the lethality of heat waves. Bodies are frequently found days after death, when core body temperature are no longer meaningful, precluding the establishment of hyperthermia. Moreover, while enumeration of deaths due to documented hyperthermia contributes to our understanding of heat wave mortality, the chief medical examiner of New York City himself acknowledged that "not every heat-related death is manifested by heat stroke"¹⁰. Perhaps a more accurate manner in which to assess heat-related mortality would be Chicago’s statistical model rather than New York’s criterion based model.

Like many other epidemics, heat waves have illuminated underlying structural violence and the prior and continuing neglect of marginalized populations. Deeply rooted socioeconomic problems have contributed to higher mortality among the poor and other marginalized populations. In the U.S., heat waves have drawn attention to the social isolation of senior citizens, as news stories have circulated about the bodies of elderly heat stroke victims decomposing for days inside their homes until finally being discovered by neighbors. Advanced age, living alone, and rarely leaving home have emerged as factors strongly associated with risk of heat-related death, and these factors appear to be further compounded by poverty. Sociologist Eric Klinenberg, who analyzed the structural violence underlying the mortality patterns of Chicago’s 1995 heat wave, explains that neighborhoods where the highest numbers of elderly people died were those that had been abandoned by businesses and residents, making social networks and support systems particularly difficult to sustain. In addition, these neighborhoods had higher crime rates, creating a fear that prevented older people from leaving their homes or opening their windows¹¹. Understanding Chicago’s landscape of urban poverty and social isolation is essential for developing effective emergency response plans that protect the city’s most vulnerable residents.

These growing data have generated new public health policies. During the 1999 heat wave, Chicago enacted its emergency heat wave response plan. The city issued strong warnings and produced press releases informing citizens of cooling centers with free bus transportation to these locations, and extended opening hours for municipal beaches and pools. The policies particularly focused on senior citizens living alone (a population at risk for poor social support networks) with telephone calls and door-to-door visits by municipal workers. One hundred and three people perished in the 1999 heat wave, demonstrating some improvement from 485 victims in 1995¹². These policies were extended at the cost of several million dollars a day, demonstrating the need for further study in the cost effectiveness of various policies.

Unfortunately, most U.S. cities are still unprepared to prevent the tragic consequences of extreme heat. A 2004 study published in the American Journal of Public Health found that of 18 U.S. cities at risk for lethal heat waves, one-third lacked any written heat wave response plans. In addition, one-third of the municipal response plans that did exist were only cursory. The study concluded that more research on municipal response plans is needed since many of the current plans have not been evaluated or are of questionable efficacy¹³. This lack of preparedness reflects the low priority status of heat waves in comparison to other natural disasters. Despite the fact that every year since 1998 the annual mortality from extreme heat in the U.S. has exceeded the death tolls of floods, tornadoes, and hurricanes combined¹⁴, fewer resources have been allocated to heat-related problems than to other extreme weather events. Moreover, the general public perceives heat waves as uncomfortable and inconvenient rather than life-threatening. Unlike natural disasters that wreak visible, violent havoc, heat waves kill stealthily, often striking victims within the confines of their homes. Thus, heat waves have been called a “silent epidemic” and an “invisible natural disaster.”

The relative importance of specific risk factors for heat-related death varies between different localities – for instance, between Chicago’s poor urban communities and California’s agricultural valleys. Although advanced age and social isolation remain important associations, one analysis found that fewer than half of the 2006 California victims were over the age of 70¹⁵, revealing the need to further examine other risk factors. Indeed, many of the deaths in the Central Valley occurred among migrant farm workers. Their high mortality, relative to the general population, may be due to the nature of their work, but many of them also live isolated from mainstream society and news information, face language barriers, cannot afford air conditioning, and lack protective social networks. These aspects of migrant life may be important research topics, especially since they are frequently shared by other segments of Central California’s population, which is comprised of a high percentage of recent immigrants and indigent people. Even though the risk profile for heat-related mortality differs between rural California and urban Chicago, the burden of suffering in both places falls disproportionately on the marginalized and the poor.

Socioeconomic factors likely contribute to the unequal heat-related mortality in other parts of the world as well. In the last several years, many of the heath-wave related deaths occurring in India were among women and children who succumbed to heat stroke, dehydration, and diarrhea. During heat waves, the water sources dry up, magnifying challenges related to limited potable water. Further epidemiologic research is needed to confirm the risk factors faced by Indian women and children during heat waves to better establish effective interventions.

Environmental factors have also played a significant role in the intensifying heat wave epidemic. The urban heat island effect – the phenomenon of city temperatures being as much as 10 degrees Fahrenheit warmer than surrounding areas – has often been cited as a contributing factor to extreme heat. The heat island effect is due to two primary causes: first, the greater absorption of heat by concrete, asphalt, and other dark surfaces, and second, the paucity of trees and plants, which provide cooling through shade and "evapo-transpiration." Because of these socially constructed phenomena, cities generally suffer more from heat waves than rural areas. As cities continue to sprawl and become more densely populated, this problem is expected to expand.

Finally, connections of climate change to the recent streak of heat waves have been highlighted by both the media and the general public. Many people in the U.S. have attributed the 2006 heat wave to global warming. Yet the link between climate change and heat waves is more nuanced than a simple cause-effect relationship. Because of weather’s natural variability, no specific weather event can be directly attributed to global warming. Conversely, it is possible to predict climate, the pattern of weather that is based on statistics and averages. Even though global warming cannot be directly linked to specific heat waves, it can be shown to have increased their frequency, intensity, and probability of occurrence. In a study published in Nature, a team of British scientists estimated with >90% confidence interval that increasing greenhouse emissions more than doubled the likelihood of occurrence of the 2003 European heat wave¹⁶. The main point of their analysis is that anthropogenic warming has shifted the statistical distribution of summer temperatures upward. Therefore, it becomes more likely that extreme temperatures will be reached. Another study published in Science predicted that greenhouse gases will cause more frequent, more intense, and longer lasting heat waves in Europe and North America in the coming century¹⁷. Unfortunately, these predictions for more frequent and more intense extreme weather extend to other natural disasters, including hurricanes and droughts. Some American lawmakers are enacting policies to limit this progression in global warming. Only weeks after California state officials announced their new initiative to research the links between heat waves, global warming, and public health, state lawmakers passed historic legislation to mandate a 25% cut in carbon emissions by 2020. Several northeastern states have also taken steps to reduce their carbon emissions.

Climate change, increased urbanization, poverty, old age, social isolation, and a paucity of public awareness all fuel the growing heat wave epidemic. This global epidemic will continue unless greater steps are taken to address this pressing global health problem. It is critical that American cities develop and expand strategies to protect the public from heat waves, and cities with plans already in place should ensure that all segments of the population are adequately protected. Additionally, further study is necessary to understand the interaction of social and environmental conditions that contribute to this "silent epidemic", particularly for marginalized groups. It is most vulnerable among us who bear the brunt of the casualties and remind us all that contrary to the popular expression, death is not the great equalizer – not even in a natural disaster.

Footnotes:

1. Larsen, Janet. "Record heat wave in Europe takes over 35,000 lives: far greater losses lie ahead." Eco-Economy Update. Earth Policy Institute. October 9, 2003

2. Many feared dead in South Asian heat wave. BBC. June 6, 2005.

3. Donoghue ER, Nelson M, Rudis G, Watson JT, Huhn G, Luber G. Heat-related deaths – Chicago, Illinois, 1996-2001 – and United States – 1979-1999. Morbidity and Mortality Weekly Report (2003);52:610-13.

4. Klinenberg E. Denaturalizing disaster: a social autopsy of the 1995 Chicago heat wave. Theory and Society (1999);28(2):239-95.

5. Michelozzi P, de’Donato F, Bisanti L, et al. The impact of the summer 2003 heat waves on mortality in four Italian cities. Euro Surveillance (2005);10(7):161-5.

6. Covarrubias A. California heat wave deaths prompt health study. Los Angeles Times. August 3, 2006.

7. National Oceanographic and Atmospheric Administration (U.S. Department of Commerce). Natural Disaster Survey Report: July 1995 Heat Wave. December 1995.

8. Perez-Pena R. New York’s tally of heat deaths draws scrutiny. New York Times. August 18, 2006.

9. Ibid.

10. Ibid.

11. Klinenberg, 1999.

12. Donoghue, et al., 2003.

13. Bernard and McGeehin, 2004.

14. Bernard SM and McGeehin MA. Municipal heat wave response plans. American Journal of Public Health (2004);94:1520-1522.

15. Steinhauer, 2006.

16. Stott PA, Stone DA, and Allen MR. Human contribution to the European heatwave of 2003. Nature (2004);432:610-614.

16. Meehl GA and Tebaldi C. More intense, more frequent, and longer lasting heat waves in the 21st century. Science (1994);305:994-997

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Climate change is a problem that all communities face regardless of their location globally. Thinking globally but acting locally can make a difference regarding climate change.

To take action in your community, you can:

- Find out if your city/community has signed on to the Mayors' Climate Protection Agreement. Signatories pledge to encourage Congress to adopt the Kyoto Protocol and to take steps to reduce carbon emissions in their own cities/communities. For more information, see here.

- If your city/community is at risk for a heat wave, find out if there is a heat wave response plan in place, and if so, find out if that response plan takes into account the needs of all segments of the population.

To take action nationally:

Join the Physicians for Social Responsibility Prescriptions Campaign to educate your colleagues and petition members of Congress about the public health effects of climate change. For more information or educational materials, please e-mail Silvia Chiang, AMSA’s Global Environment Coordinator, at ssc15@case.edu.

Finally, for more information about climate change, environment, and their impacts on human health, visit the website of Harvard Medical School's Center for Health and the Global Environment. The Center's Associate Director, Dr. Paul R. Epstein, will be speaking at the upcoming AMSA National Convention in March 2007. Come join other activists and learn more about environmental issues in Washington, DC!