Endless Summer No Picnic for Seniors

Older people might be the first to experience the health consequences of global environmental change. These perturbations could put many more at risk of sickness and death from extreme weather, air pollution, and the spread of infectious disease.

Last summer, record-high temperatures in Europe killed thousands of elderly people. An exact count might never be known, but in Rome, the excessive heat claimed the lives of about 1100 more than usually die in summer, all over age 65. And with global warming on the rise, many observers predict more of this kind of severe weather and its casualties.

Health experts have become increasingly concerned about the possible consequences of global climate change. In addition to the danger of sweltering summers, the extreme fluctuations in weather could amplify lung-searing pollution and promote epidemics of infectious diseases carried by insects and rodents. Those over 65 are most susceptible, says Joyce Rosenthal, director of the New York Climate and Health Project at Columbia University. When it comes to global warming, they're the "canaries in a coal mine," adds Ross Gelbspan, author of two books on climate change. As we swing into another summer, researchers say we must learn how to identify and respond better to the changes that have already occurred and try to prevent more extensive warming.

Although debate about the magnitude of global warming continues, most researchers agree that the climate is changing and that human activities are a significant culprit. Auto emissions and other forms of air pollution have boosted the atmospheric concentrations of so-called greenhouse gases that are trapping heat close to Earth's surface. Quantities of one greenhouse gas, carbon dioxide, have soared by one-third since the industrial revolution, mostly in the past 50 years, and are expected to double or triple in 100 years.

Researchers are less certain about the extent to which global warming is affecting public health. In any given day or week or season, scientists cannot distinguish between natural weather fluctuations and longer term climate changes. What's more, the disease outbreaks that might be linked to climate change are also influenced by confounding factors, such as increases in travel, emerging drug resistance, and population growth, says Jonathan Patz, outgoing director of the Program on Health Effects of Global Environmental Change at the Johns Hopkins Bloomberg School of Public Health in Baltimore, Maryland.

Despite these variables, some researchers are convinced that global warming will be hazardous to our health. "Can we say with certainty that there will be health consequences associated with a change in the climate? Yes," says Benjamin Preston, senior research fellow at the Pew Center on Global Climate Change in Arlington, Virginia.

According to the United Nations-sponsored Intergovernmental Panel on Climate Change, large cities can expect to lose thousands of citizens--mostly seniors and the urban poor--to the rising heat each summer. In particular, lack of air conditioning proves deadly when people succumb to cardiovascular and respiratory diseases in their stifling apartments. Nighttime lows are rising twice as fast as daytime highs are, robbing people of relief from the heat stress.

The broiling sun also heats up the chemical stew of air pollution in cities, often causing higher ozone levels, which can contribute to excess deaths. In the New York metropolitan region, for example, about 840 deaths per summer are heat related, whereas ground-level ozone pollution causes another 1300. Summer mortality could more than double in about 50 years, mostly due to heat, according to a new regional model that weaves together health effects of global and regional climate, air quality, and land use.

Milder winters could cut down on the number of cold-related deaths--and more old people die in winter than in summer. On balance, however, hotter summers will kill more people than warmer winters will save.

Changes in temperature, humidity, and rainfall can also boost the geographic range of some infectious agents, particularly those carried by mosquitoes, ticks, and rodents. The World Health Organization estimated that recent climate shifts caused about 150,000 extra deaths worldwide in the year 2000, partly due to an increased incidence of malaria in Africa. The warmth and rain made previously inhospitable places more welcoming to malaria-carrying mosquitoes.

Environmental upsets, including those wrought by climate, can also drive the emergence of new infectious diseases, says Mary Pearl, president of Wildlife Trust in Palisades, New York. West Nile virus first appeared in the United States in New York City after a drought and the hottest summer on record. And infections spiked in Colorado last year after record hot temperatures. Even so, for any particular disease, researchers cannot definitively blame long-term climate change. "You can't say that global warming is responsible for West Nile," Patz said. "You can simply point out that extreme climate conditions may be a factor."

One way to skirt some of these climate-related calamities would be to put the brakes on global warming. Patz and his colleagues recommend adopting approaches to decrease greenhouse gas emissions, such as embracing energy-efficient renewable technologies. In the meantime, others insist that we find ways to adapt to the warming planet and extreme weather. For example, Rosenthal says, by analyzing the cause of death in previous heat waves, researchers have identified ways to save seniors from fatal exposure to the heat--instituting programs to check in on vulnerable older people, or creating cool, tree-filled oases in hot urban spaces. Air conditioning also works wonders during a heat wave, but many people cringe from its high use of electricity, which ultimately pumps even more greenhouse gases into the atmosphere.

For the next several decades, most people living in developed countries with air conditioning, vaccines, and decent health care systems might do fine. But greenhouse gases linger in the atmosphere for hundreds or even thousands of years, accumulating with every turn of the ignition key--so future generations might not be so lucky.

Carol Cruzan Morton is a science writer in the Boston area who prefers subzero winds of winter to urban heat.