Photograph by Sanjeev Gupta, EPA/Corbis
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Dhanraj, 17, gets medical treatment in Bhopal Madhya Pradesh after suffering from sunstroke and severe dehydration.

Photograph by Sanjeev Gupta, EPA/Corbis

India’s Heat Wave: How Extreme Heat Ravages the Body

Furnace-like conditions can overwhelm the body's natural cooling system, resulting in injury and death.

More than 1,800 people have died in one of the worst heat waves in India’s recent history. Temperatures nearing 122°F (50°C) melted roads in New Delhi and scorched crops in the fields. It proved especially deadly in the southern states of Andhra Pradesh and Telangana, where at least 1,700 died in the past week.

May is consistently India’s hottest month, but, even so, temperatures shot far above normal. In the coastal region of Andhra Pradesh, daytime temperatures rose more than 40°F (7°C) higher than average, according to India’s meteorological department director B.P. Yadav.

Aftab Ahmad, an internal medicine expert at Apollo Health City, a hospital complex in Hyderabad, said there could be many reasons for the heavy death toll. “The prime among them is what is called climatic acclimatization,” he told The Times of India Wednesday  “This year the temperature changed suddenly. This disturbs the defense mechanisms of the body.”

India’s extreme weather serves as a stark reminder of how vulnerable the human body is to severe heat. Unable to adapt to sweltering conditions, people become susceptible to sunstroke and severe dehydration.

Claude Piantadosi, director of the Duke Center for Hyperbaric Medicine and Environmental Physiology in Durham, North Carolina, says human beings aren't built to spend long periods of time in temperatures that exceed the body’s own temperature of about 98.6 degrees.

Cooling Mechanisms

Normally, the body stays cool by shedding unused energy in the form of heat dissipating by conduction—or the transfer of heat energy to the skin's surface, and then by convection—the transfer of heat energy to the air. The hotter it gets, the more difficult it becomes to shed that heat. At temperatures topping 100 degrees, the system reverses and heat flows from the environment into the body, says Piantadosi.

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Scorching heat melted tar and asphalt in New Delhi Wednesday, distorting zebra road crossings.

At that point, humans depend on a second cooling mechanism: perspiration. Sweat heats up and is transformed into water vapor, which removes heat from the body and reduces the internal core temperature. But high humidity defeats the system, because sweat won't evaporate when the air is already saturated with moisture. "The combination of heat and high humidity is really quite deadly," Piantadosi says. "It defeats our heat dissipation mechanism."

Worst-Case Scenario

The sweating mechanism, however, only works if people drink enough water to make up for the loss of body fluids. Without sufficient water, dehydration sets in. Blood flow to the skin decreases, along with the ability to sweat. Body heat builds up. A body temperature of 104°F indicates danger; 105°F is the definition of heat stroke; and a temperature of 107°F could result in irreversible organ damage or even death.

A normal, healthy person who is not used to the heat can, in heat wave conditions, sweat as much as 1.5 quarts in an hour. Someone acclimated to hot weather develops the ability to sweat (and thus cool off) at a more intense rate, losing up to two quarts of sweat in an hour. "So he'd have to drink two quarts of water an hour just to stay even," says Piantidosi.

The combination of high heat and lack of water is a sure recipe for multiple organ damage. Internal temperature soars, heart rate goes up, blood flow slows down, and organs begin to shut down. The kidneys shut down, and the heart has to work harder to pump a lower volume of blood through the body. Other organs begin to shut down, then fail.

A Quick Defeat

Under extreme heat conditions, it can all happen very quickly—in an hour, or even less. The brain, too, is affected by reduced blood flow. That's why people in the throes of heat illness begin to make poor, often life-threatening, decisions.

To compound matters, “in a place like India where there’s lots of poor people, access to clean water in plentiful amounts can be a problem,” Piantadosi says.

The first rains of the monsoon season are expected to hit southwest India by the end of May. But it could be weeks before the northeast feels the cooling effects. Until then, there is little the government can do.

Local officials have been opening water camps. They also advise people to stay indoors between the hours of 11 a.m. and 4 p.m. But seeking refuge is not a realistic option in a poor country. Most of the victims live on the streets, exposed 24/7 to searing heat.

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