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Being able to adjust to your climate means being able to survive. An Indiana State University study of leaf-cutter ants found that those coming from cities functioned in 108- degree heat for 20 percent longer than their country cousins. The effect in city-dwelling humans can be just as profound.
"That morning power walk or run on a warm April day in the low 80s feels terribly hot, but in July or August won't because you'll have acclimated," says Dr. Thomas Matte, of the NYC Department of Health and Mental Hygiene. When you're used to the heat, electrolytes make up less of your sweat. Instead of sweating so much around your torso, you'll sweat more efficiently from your arms and legs. And your trigger point for sweating will rise.
"But if you stay in your chair in an air-conditioned room and never have to turn on your hormones and heat-loss mechanism, you're not going to be a fit organism," Blumberg says.
YOUR BRAIN ON ICE
We also hamper ourselves with lousy diets. Instead of consuming junk food and fatty ice cream (and then rushing to gulp down sports drinks and electrolyte supplements), we should drink plenty of water or juice, and eat dark leafy greens, nuts, seeds, whole grains, vegetables, blackstrap molasses, and bananas to get the calcium, magnesium, and potassium adults need.
And don't fetishize ancestral lore. Drinking hot tea on a hot day won't cool you down, but rather will burden your body with extra heat to disperseit's a matter of basic physics. Chinese skullcap is believed in Asia to stimulate flushing, but Western scientists aren't yet convinced. Capsicum, the operative component in cayenne pepper and other hot spices, stimulates neural channels designed to receive signals of thermal stress. Some argue that the chemical can be beneficial by tricking the body into producing a protective sweat without exertion. But, asks Hunter College nutrition professor Arlene Spark, "Why would you need to trick the body into sweating during a heat wave?"
Michael Caterina, a professor of biology at Johns Hopkins University School of Medicine and a leading capsicum researcher, says, "One thing that's pretty clear in lab animals is that when newborn rats are injected with capsicum, they lose some of their temperature-sensing neurons, and for the rest of their lives they're missing this subpopulation of neurons. If you put them into an excessively warm environment, they can't protect themselves against overheating." In adult humans, capsicum temporarily dulls or deadens those receptors in a localized fashion, such as on the tongue.
Apart from toughing it out and allowing our bodies to care for themselves, we can take cues from critters. The most basic advice regarding summer clothingthat it should be light-colored, thin, and loosenicely mimics a camel's fur, which provides sun protection and prevents sweat from simply rolling off before it can absorb body heat and transfer it to the air.
Nature is full of tricks for beating the heat. Blumberg is particularly admiring of the gazelle's carotid rete, an intricate web of thin blood vessels (read: increased surface area) below the brain stem. This web allows a gazelle fleeing a lion to protectively chill its brain to more than seven degrees Fahrenheit below its body temperature, even as its muscles are pumping frantically.
"That advantage is important because the brain gets damaged at a lower temperature than the rest of your body. It's a bit like the neck cooler you see in the Sharper Image catalogue. It's cooling the blood that goes to your brain. There's a conceptual validity to the product, but I don't know of any scientific studies on it," he says. "But we do know that it feels damn good."
Not that the brain always gets pride of place. As Blumberg writes, "A ram continues panting as long as its scrotum is overheated, even if its body temperature decreases more than two degrees Celsius (four degrees Fahrenheit). It appears that the ram is more committed to maintaining the temperature of its testes than to maintaining its deep body temperature."
SO MUCH FOR SHADE Buildings and cities, like bodies, are in large part plumbing. In ancient Egypt, wealthy pallace dwellers installed cooling systems that circulated water from aqueducts through the walls. Today's cutting-edge "green" buildings in Tribeca, Harlem, and Chelsea, among other neighborhoods, save electricity by employing geothermal cooling, looping water through coils deep underground to chill the air in the chambers above. Seven World Trade Center, a model sustainable building, uses rainwater for cooling and for watering plants.
New York City is, by world standards, ridiculously rich in fresh water. Our civil engineers spend much of their time racing to find ways to get rid of it. Household "gray water" from showers and sinks and storm water could slake the thirst of the 1 million new trees Mayor Bloomberg is calling for. Many sidewalks could be lined with "nearly continuous greenswales," says Rohit Aggarwala, director of the Office of Long-term Planning and Sustainability. Bloomberg also wants a tax credit for so-called "green roofs," which would be covered with grass and other plants.
Just don't expect even a newly verdant metropolis to spell the end of our heat island.