托福阅读机经虽然没有口语写作机经使用频率高，但托福阅读却是整个托福考试的重要部分。适当地掌握一些托福阅读技巧和背景材料对于我们备考托福阅读也是有所帮助的。
In Hot Weather,Know the Warning Signs of Heat Disorders
BOB DOUGHTY: This week, we tell about health problems linked to extreme heat. We tell what experts suggest to prevent and treat these problems.
FAITH LAPIDUS: Extremely hot weather is common in many parts of the world. Although hot weather just makes most people feel hot, it can cause serious medical problems, even death.
Floods, storms and other natural events kill thousands of people every year. So does extreme heat. Experts say heat may be nature's deadliest killer.
For example, Indian officials blamed extreme heat for killing more than two hundred people in late May. Temperatures reached almost fifty degrees Celsius in several Indian states.
BOB DOUGHTY: Several hot days that follow each other are considered a heat wave. Experts say heat waves often become dangerous when the nighttime temperature does not drop much from the highest daytime temperature. This causes great stress on the human body.
Doctors say people can do many things to protect themselves from the dangers of extreme heat. Stay out of the sun, if possible. Drink lots of cool water. Wear light colored clothing made of natural materials. Make sure the clothing is loose, permitting freedom of movement. Also, learn the danger signs of the medical problems linked to heat.
FAITH LAPIDUS: The most common health problem linked to hot weather is heat stress. Usually, it is also the least severe. The causes of heat stress include wearing heavy clothing, physical work or exercise, hot weather and high humidity. Humidity is the amount of water in the air.
If several of these conditions are present at the same time, a person's body temperature may rise above safe levels. The person loses large amounts of body water and salt in perspiration. Perspiration is one of the body's defenses against heat. It is how the body releases water to cool the skin.
Most people suffer only muscle pain because of heat stress. The pain is a warning that the body is becoming too hot. Doctors say those suffering muscle pain should stop all activity and rest in a cool place. They should also drink cool liquids. Doctors say not to return to physical activity for a few hours because serious conditions could develop.
BOB DOUGHTY: Some people face an increased danger from heat stress. They may have a weak or damaged heart, high blood pressure or other problems of the blood system. Severe heat increases problems for small children, older adults and those who have the disease diabetes.
It is also dangerous for people who weigh too much and have too much body fat, and for people who drink alcohol. Hot weather also increases dangers for people who must take medicine for high blood pressure, poor blood flow, nervousness or depression.
FAITH LAPIDUS: Untreated heat stress can lead to a more serious problem called heat exhaustion. A person suffering from heat exhaustion loses too much water through perspiration. The person becomes dehydrated.
A person suffering heat exhaustion feels weak and extremely tired. He or she may have trouble walking normally. Heat exhaustion may also produce a feeling of sickness, a fast heartbeat, breathing problems and pain in the head, chest or stomach. Doctors say people with such problems should rest quietly in a cool place and drink plenty of water. They also say it may help to wash with cool water.
BOB DOUGHTY: Heat exhaustion can develop quickly. It also can develop slowly, over a period of days. Doctors call this dehydration exhaustion. Each day, the body loses only a little more water than is taken in. The person may not even know this problem is developing. If the problem continues for several days, the effects will be the same as the usual kind of heat exhaustion.
Experts say even a two percent drop in the body's water supply can cause signs of dehydration. These signs include problems with memory and even simple mathematics.
FAITH LAPIDUS: Dehydration limits a person's ability to work and think. Experts say a reduction of only four or five percent in body water leads to a drop of twenty to thirty percent in work ability. The loss of salt through perspiration also reduces the amount of work that muscles can do.
The treatment for dehydration exhaustion is the same as for heat exhaustion. Drink plenty of water and rest in a cool place. Even better, doctors say, drink about two liters of water a day so problems with dehydration will not have a chance to develop. BOB DOUGHTY: Heat exhaustion can lead to heat stroke if it is not treated. Heat stroke is the most serious disorder linked to hot weather. It results when the body is not able to control its temperature. The body's temperature increases and perspiration fails.
以上即为关于托福阅读机经背景科学类：酷热天气易导致健康问题的详细内容，对于同学们积累托福阅读机经的背景知识有一定帮助，也希望同学们在日常复习中自己也有意识地积累一些托福阅读背景素材。 |
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