EVENING. People.

Another Side Effect From The Heat Wave: `Supermarket Syndrome'

July 27, 1995|By St. Louis Post-Dispatch.

It's as close as most of us will ever come to getting cooked.

The air-conditioned office, mall or supermarket has left us a bit chilly. We step outside into the peak of a hot, humid summer day.








We may feel a bit drained, or even dizzy. But the toll on the body is minimal, and there's little health risk for the normal, healthy adult-unless we engage in strenuous activity.







In the heat of summer, the body pumps up its blood supply to handle the heat better. Until this adjustment, mowing the lawn and shopping can be a strange experience early in the summer, according to Thomas Adams, a physiologist at Michigan State University. Even though body temperature remains normal, the warm air triggers a reflexive surge in blood flow to the skin. That, in turn, causes a drop in blood pressure.



After the blood delivers heat to the skin, the heat is carried away into the air by physical processes with names such as convection, conduction and radiation. But when the air temperature exceeds the skin temperature, sweat glands take over.

Between 3 million and 5 million sweat glands cover the human body. Their job: to put moisture on the skin. As the sweat evaporates, it takes energy away from the skin in the form of heat.

These glands can unleash virtual torrents of water. A person exercising on a hot day can generate 12 quarts of water in 24 hours, with bursts of sweating up to 3 quarts an hour.

On a dry day, sweat evaporation readily pulls heat from the body. Unfortunately for residents of moist regions, humidity short-circuits the process and makes hot air feel worse. That's because the air is already laden with moisture, so sweat can't evaporate as easily as in a drier climate.

Twentieth-century American life in the summertime is filled with thermal barriers. That's what scientists call the invisible walls where air-conditioned air and hot outside air meet.

How dramatic a thermal barrier can humans stand? The scientific literature cites the cases of two researchers who subjected themselves to 250-degree air for 15 minutes. One of them went on to take 364 degrees for one minute.