Question

    It doesn’t kill germs better than cooler water, but turning tap temperatures high, the US burns carbon equal to the emissions of Barbados.

People typically wash their hands seven times a day in the United States, but they do it at a far higher temperature than is necessary to kill germs, a new study says. The energy waste is equivalent to the fuel use of a small country.

It’s cold and flu season, when many people are concerned about avoiding germs. But forget what you think you know about hand washing, say researchers at Vanderbilt University. Chances are good that how you clean up is not helping you stay healthy; it is helping to make the planet sick.

Amanda R. Carrico, a research assistant professor at the Vanderbilt Institute for Energy and Environment in Tennessee, told National Geographic that hand washing is often “a case where people act in ways that they think are in their best interest, but they in fact have inaccurate beliefs or outdated perceptions.”

Carrico said, “It’s certainly true that heat kills bacteria, but if you were going to use hot water to kill them it would have to be way too hot for you to tolerate.”

She explained that boiling water, 212°F (99.98°C), is sometimes used to kill germs — for example, to clean drinking water that might be polluted with germs. But “hot” water for hand washing is generally within 104°F to 131°F (40°C to 55°C). At the high end of that range, heat could kill some germs, but the sustained contact that would be required would scald the skin.

Carrico said that after a review of the scientific literature, her team found “no evidence that using hot water that a person could stand would have any benefit in killing bacteria.” Even water as cold as 40°F (4.4°C) appeared to reduce bacteria as well as hotter water, if hands were scrubbed, rinsed (冲洗) and dried properly.

In fact, she noted that hot water can often have an unfavorable effect on hygiene. “Warmer water can harm the skin and affect the protective layer on the outside, which can cause it to be less resistant to bacteria,” said Carrico.

Using hot water to wash hands is therefore unnecessary, as well as wasteful, Carrico said, particularly when it comes to the environment. According to her research, people use warm or hot water 64 percent of the time when they wash their hands. Using that number, Carrico’s team calculated a significant impact on the planet.

“Although the choice of water temperature during a single hand wash may appear minor, when multiplied by the nearly 800 billion hand washes performed by Americans each year, this practice results in more than 6 million metric tons of CO2 equivalent emissions annually,” she said.

That’s roughly equal to the emissions of two coal-fired power plants, or 1,250,000 passenger vehicles, over the course of a year. It’s higher than the greenhouse gas emissions of small countries like EI Salvador or Armenia, and is about equivalent to the emissions of Barbados. If all US citizens washed their hands in cooler water, it would be like eliminating the energy-related carbon emissions of 299,700 US homes, or the total annual emissions from the US zinc or lead industries.

The researchers found that close to 70 percent of respondents said they believe that using hot water is more effective than warm, room temperature, or cold water, despite a lack of evidence backing that up, said Carrico. Her study noted research that showed a “strong cognitive (认知的) connection” between water temperature and hygiene in both the United States and Western Europe, compared to other countries, like Japan, where hot water is associated more with comfort than with health.

The researchers published their results in the July 2013 issue of International Journal of Consumer Studies. They recommended washing with water that is at a “comfortable” temperature, which they noted may be warmer in cold months and cooler in hot ones.

1.What does the writer mainly focus on when writing this passage?

A.Whether hot water helps kill germs effectively in hand washing.

B.How hot water contributes to the serious worsening of our planet.

C.Why the consumption of hot water is unnecessary and wasteful.

D.What the advantages and disadvantages of using hot water are.

2.The underlined word scald in paragraph six probably means_________.

A.burn B.improve

C.soften D.wrinkle

3.According to the passage, all the following share roughly the same CO2 emissions yearly EXCEPT______.

A.two coal-fired power plants B.US zinc or lead industries

C.1,250,000 passenger vehicles D.EI Salvador or Armenia

4.Which of the following is WRONG according to the passage?

A.Boiling water at 212°F (99.98°C) works effectively in killing germs.

B.Warmer water can damage the protective layer of the outside skin.

C.There is much difference between cold water and hot water in reducing bacteria.

D.Americans have inaccurate beliefs or outdated perceptions in hand washing.

5.Which of the following is the standard of a comfortable water temperature for washing hands?

A.Warmer in winter and cooler in summer.

B.Between 104°F to 131°F (40°C to 55°C).

C.Below 104°F (40°C) or above 131°F (55°C).

D.Warm enough to kill germs and clean up.

Answer

1.A

2.A

3.D

4.C

5.A

【解析】

本文为一篇说明文。文章介绍了用热水洗手杀死细菌的是不必要的，也是浪费的。

1.推理判断题。通读全文及根据第一段It doesn’t kill germs better than cooler water, but turning tap temperatures high, the US burns carbon equal to the emissions of Barbados. (它杀死细菌的能力并不比冷水强，但把水龙头的温度调高，美国消耗的碳相当于巴巴多斯岛的排放量)可知，写这篇文章时，作者主要关注用热水洗手是否有助于有效杀灭细菌。故选A项。

2.词句猜测题。根据前文But “hot” water for hand washing is generally within 104°F to 131°F (40°C to 55°C). At the high end of that range, heat could kill some germs(洗手用的“热”水一般在104到131华氏度（40到55摄氏度）之间，在这个范围的高端，高温可以杀死一些细菌)可知，可以杀死细菌的热水温度处于高温范围，再根据常识可知，如果持续接触高温热水，皮肤可能被烫伤。由此推测scald意为“烫伤”与A项burn“燃烧，烫伤”意思相近。故选A项。

3.细节理解题。根据倒数第三段That’s roughly equal to the emissions of two coal-fired power plants, or 1,250,000 passenger vehicles, over the course of a year. It’s higher than the greenhouse gas emissions of small countries like EI Salvador or Armenia, and is about equivalent to the emissions of Barbados. If all US citizens washed their hands in cooler water, it would be like eliminating the energy-related carbon emissions of 299,700 US homes, or the total annual emissions from the US zinc or lead industries.(这大约相当于两座燃煤发电厂一年的排放量，即1250000辆乘用车的排放量。它比像萨尔瓦多或亚美尼亚这样的小国家的温室气体排放量要高，大约相当于巴巴多斯的排放量。如果所有美国公民都用冷水洗手，那就好比减少了29.97万户美国家庭与能源相关的碳排放，或是美国锌或铅工业的年度总排放量)可知，两座燃煤发电厂，美国锌或铅工业，1250000辆乘用车的二氧化碳排放量大致相同。因此选项中除了萨尔瓦多或亚美尼亚其他的二氧化碳排放量每年大致相同。故选D项。

4.细节理解题。根据倒数第二段The researchers found that close to 70 percent of respondents said they believe that using hot water is more effective than warm, room temperature, or cold water, despite a lack of evidence backing that up, said Carrico.(卡里科说，研究人员发现，近70%的受访者表示，他们认为使用热水比温水、室温水或冷水更有效，尽管缺乏证据支持这一点)可知，没有证据证明冷水和热水在减少细菌方面有很大的区别。冷水和热水在减少细菌方面有很大的区别是错误的。故选C项。

5.细节理解题。根据最后一段They recommended washing with water that is at a “comfortable” temperature, which they noted may be warmer in cold months and cooler in hot ones.(他们建议在“舒适”的温度下用水清洗，在寒冷的月份水温可能更高，而在炎热的月份水温可能更低)可知，冬天用暖和的水，夏天用凉爽的水是洗手时舒适的水温标准。故选A项。