It may be hard to believe, but while much of the eastern U.S. was digging out from a series of snowstorms, Earth as a whole was experiencing its ninth warmest February on record. Australia endured intense heat waves in late January and early February, reaching a record high of 119 degrees F in Hopetoun, Victoria on February 7, which may be the highest temperature ever recorded for a southern latitude. The dry, hot season also brought the deadliest wildfires in Australia’s history.
|Image of Exceptional Australian Heat Wave courtesy of the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite|
It stands to reason that as average surface temperatures on Earth rise, heat waves - dangerous spikes in temperature that last for days or even weeks without breaking - would increase in frequency and intensity. Scientific models of climate change predict this. It’s frightening to think that those of us who dwell in the northern hemisphere can expect more summers like that of 2003, when an August heat wave broke temperature records across the European continent and killed over 50,000 people.
But who dies during a heat wave, why do they die, and what can be done to save lives when the temperature soars?
The lethality of a heat wave is determined by its intensity, its duration, and how high the temperature remains overnight. For perspective, consider the European heat wave of 2003. It was very intense, with daytime highs reaching 95 degress F across a continent where most homes lack air conditioning; national heat records were broken in Switzerland (106.7 degrees F) and Portugal (117.1 degress F), and Britain experienced its first day of temperatures above 100 degress F in nearly 300 years of record keeping.
Most people can tolerate a long series of hot days if their bodies can cool off at night, but casualties start to mount when you have stiflingly hot temperatures without relief at night for three days or more. The heat wave that struck Europe in 2003 lasted for two weeks, and nighttime temperatures did not fall enough to bring relief.
And it’s not just the heat that’s deadly.
Many deaths during heat waves are actually caused by air pollution in the form of increased ground-level ozone (the primary component of smog, most of which comes from motor vehicle emissions and industrial pollutants) and tiny particles that accumulate in the still air. Ozone damages the lungs and is especially harmful for people with lung diseases such as asthma. And tiny particles small enough to evade the lung’s filters can enter the bloodstream, raising the risk of heart attacks. Such indirect casualties help explain why it took over a year to tally all the deaths from the 2003 heat wave. They also explain why heat waves, which generally are responsible for more deaths per year in the U.S. than any other natural disaster, fail to draw the same level of public attention as hurricanes or tornadoes, which claim their victims rapidly and directly.
Moreover, heat does not treat all people equally. It targets the old (>65) and the very young (<1), whose bodies cannot easily adapt to extreme temperatures. Deaths predominate among elderly and impoverished individuals who are isolated and unable to move to a cool location.
What You Can Do
How can you protect yourself and others during a heat wave? A few suggestions:
• Drink plenty of cool liquids, not just when you’re thirsty. Avoid iced drinks, which slow down drinking, and alcohol and caffeinated beverages, which can lead to dehydration. Water is best.
• Stay indoors in an air-conditioned location during the hottest part of the day. If your home isn’t air-conditioned, go to a library or mall or other public space. Even a few hours of air conditioning can be protective. Portable electric fans are not always protective, and in very hot conditions (>99 degrees F) they may even increase heat stress by blowing hot air over the body while increasing evaporation of sweat.
• Take cool baths, showers, or sponge baths. The most effective way to lower the body temperature of a person with exercise-induced hyperthermia is to immerse them in ice-cold water.
• If you are caring for babies or young children, make sure they stay cool indoors and get plenty of liquids. Children are vulnerable because they run around outside and don’t notice when they are overheated. Infants have to rely on adults to keep them cool.
• If you have friends or neighbors who are elderly or otherwise vulnerable to heat stress due to pre-existing health conditions, check on them at least twice a day to make sure they are staying cool. Help them get to a place with air conditioning. If you find someone who may be suffering from heat stroke, call 911 immediately.
When heat waves occur in northern cities like Philadelphia or Chicago they typically cause more deaths than in southern cities like Phoenix. While long-term exposure to high temperatures may help southerners adapt to the heat, a likelier explanation for their increased survival is that southern residents have adopted behaviors appropriate to a warmer climate, including those described above.
Many cities, including Chicago, Philadelphia, Baltimore, and Toronto, have plans for dealing with heat emergencies and web sites with tips for surviving them. (Chicago’s plan was developed after a 1995 heat wave killed more than 700 people.) In Baltimore, residents in need are advised to call 311, where operators can provide directions to cooling centers and arrange for transportation. Baltimore’s Code Red Heat Alert Plan describes a system for providing shelter, outreach, and transportation to residents during a heat advisory or excessive heat warning.
In addition to media announcements and cooling centers, Philadelphia’s Hot Weather Warning System takes advantage of its 5,000 community-elected block captains to identify and visit high-risk individuals within their neighborhoods. A study of Philadelphia’s program determined that it saved over a hundred lives in four years. But you don’t have to be elected to visit a neighbor or call a friend and make sure they are keeping cool when the pavement starts to melt, and you might even save a life.
Elsewhere on the Web:
From the National Library of Medicine, a collection of resources on the prevention, detection, and treatment of heat illness.
Carol Berkower is a mathematician and molecular biologist living in Baltimore.
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