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The human body is composed of about 60 to 80% water, depending on body size. Everyone needs between 1 and 4 liters of water a day, more in extremely hot conditions, just to survive. But while water is essential to human life, water can also end it. Here are 10 ways water is not a friend to your continued existence.
The human body spends most of its time in a "thermoneutral zone," generating temperatures of 36.5°C and 37.5°C (about 98-99°F). When the core temperature falls below this narrow zone, the body can burn between 40 and 60 calories an hour to bring it back to normal. Those 40 to 60 calories, however, are just enough to raise the temperature of a mere 40 to 60 grams of water just 1°C.
When the body is plunged into massive amounts of cold water, it simply cannot generate enough heat, and as the body's temperature passes 33°C (about 90°F) the brain cannot function properly, and at about 21°C (70°F) there is death. Cold water kills, and sometimes kills in minutes.
An avalanche is the massive sliding of water frozen as snow and ice down a mountainous incline. About 1 in 6 people who dies in an avalanche succumbs to crushing injuries caused by the weight of snow, but about 5 in 6 die of suffocation. If you are caught in an avalanche, lift your arms over your head, turning your face away from the snowslide, to create an air pocket in which you may survive until help arrives. Don't try digging your way out unless you know you are at the surface, digging uses limited oxygen supplies.
3. Waterborne pathogens.
Worldwide, nearly 2 million people a year die of waterborne diseases, ranging from cholera, the waterborne diarrhea which has killed millions of people over centuries, to fecal E. coli, viruses, and parasites. Millions of people also die from the cumulative effects of exposure to chemical contaminants of water, especially arsenic, which is a particular problem in South Asia and the Southwestern United States.
4. Holding your urine in (well, sort of).
It is possible to die of uremic poisoning caused by accumulation of toxins that accumulate in the kidneys. This can occur when the kidneys or the urethra, the channel that carries urine outside the body, are blocked by a kidney stone. However, it's not possible to kill yourself by holding in your urine so you don't go to the bathroom. The sphincters on your urethra would fail first, causing you to wet yourself. Violent release of urine is possible when people try to hold it in, some people lasting longer than others.
5. Dangerous driving conditions.
Unsafe drivers and unsafe vehicles cause some fatal auto crashes, but the majority of unsafe driving conditions are linked to accumulations of water, whether frozen, liquid, or fog. It's the unexpected, "minor" effects of water that are the most dangerous. Just a few drops of drizzle after a long drought can loosen oils and grease on pavement that make it slick as ice. Or a shift in elevation along the roadway can bring drivers out of sunny weather into fog with zero visibility, putting them at great risk for collision with other drivers on the road. A poorly drained road can accumulate big pools of shallow water that don't seem dangerous until drivers lose control as their cars hydroplane. Sometimes sudden loss of visibility during a rainstorm, especially in tropical and subtropical locations, is the cause of an accident--every year over 3,000 drivers die during rain-related crashes in the United States.