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医学硕博会2018-06-19 10:56:48

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VOA慢速英语:口罩能防空气污染吗?

Do Face Masks Protect AgainstAir Pollution?

From VOA Learning English, this is the Health &Lifestyle report.

In many areas of the world, taking a deep breath of air can be unhealthy and dangerous.

The WHO estimates(估计) that air pollution is responsible(负责的) for about 6.5million premature -- or early -- deaths every year. It estimates that nearly 600,000 of those who die are children under the age of five.

Most of these deaths, WHO officials say, happen in developing countries.

With all this pollution in the air, many people try to protect themselves and reduce their exposure.So, some people use face masks. You may have seen pictures of people wearing such masks in big cities like Beijing and Tokyo.

But do they work?

 

One expert tells VOA Learning English that some work much better than others.

“We see lots of air pollution that just passes right through these cloth materials. And for us, it’s an important public health issue because people worldwide are choosing to use these kinds of masks to reduce their exposure(暴露).”

Richard Peltier is a professor at the University of Massachusetts,Amherst, in the Department of Public Health and Health Sciences.

He studies the effects of exposure to air pollution.

Recently, he was the lead author of a study on how well inexpensive face masks work.

Peltier led a team that tested several types of inexpensive(便宜的) face masks they bought on the streets of Kathmandu, Nepal(尼泊尔). These masks are commonly used in other polluted parts of the world.

 

 

First, what is an N95 mask?

The N95 is generally considered to be the gold standard, or the best. The U.S. government rates the N95 face mask for people who mightwork around pollutants(污染物). So, air quality experts like Peltier know exactly what it can do and what it cannot do.

Peltier calls the N95 mask a more advanced version of the inexpensive(便宜的) cloth masks thathe studied. The researchers used the N95 mask in their study for comparison(比较).

However, Peltier says, N95 masks are either not available or too expensive in many places where pollution is severe(严峻的). Also, he adds, it is made of paper. So, it can't be washed andreused like cloth face masks.

“But what we find in many parts of the world are the unavailability(无效用) of N95 masks. You can’t buy these. Or if they are available, they are too expensive. So, people chose to substitute the N95 masks for inexpensive pieces of cloth.”

The face masks that Peltier and his team studied can be bought oncity streets in places like China, Nepal(尼泊尔) and India. He explains that these face masks have some effect -- but not enough.

“So, the masks that we studied do have some effect. It’s not acomplete effect and it’s nowhere near comparable(可比较的) to an N95 mask.”

The researchers found that the most popular type of mask -- an inexpensive cloth rectangle that you can wash -- provided little protection against the smallest particles(颗粒). These particles of pollution are less than 2.5 micrometers(千分尺) and can penetrate(渗透) deep into the lungs.

He adds that there are other face masks on the market that meetthe expectation of an N95 mask. But most of these masks are too expensive. So,they are not an option for people in the developing world.

“But there are other technologies out there -- commercial(商业广告) products – that dosort of meet the expectation of an N95 mask. They do work very, very well.However, one of the issues that we find, is that a lot of these masks are tooexpensive. They’re not financially(金融的attainable by many people in the developingworld.”

Peltier says if you have a job that pays you $25 a week, youcannot afford a $25-$35 face mask.

Which inexpensive face maskworks best?

So, among the cheaper cloth face masks -- is there a difference inquality?

Peltier says yes. He explains that cloth masks with exhalation valves performed better in testing.

However, it is not the exhalation(蒸发) valve() itse lf that makes the mask more effective(有效的). Face masks withthese valves are usually thicker. The thicker material is what makes the maskbetter at keeping out pollutants(污染物).

“The cloth masks that had exhalation valves were a little thickerin material. There was more material to the masks itself. And we think that’sactually what causes the pollution to be captured(俘获) by the mask andreducing the exposure(暴露). It's not the exhalation valve itself. That valve is merely fora user's comfort. We think that the feature(特色) of the mask that makes it most useful is how thick the material is. How much material is between the air pollutionand you.”

Also, surgical(外科的) masks made out ofpaper performed surprisingly well. In an interview with the New York Times,Peltier explained that these paper masks didn’t fit as snugly to the face. But rather they stuckagainst the wearer’s wet mouth.

A good fit is most important

Peltier and other air pollution and health experts agree on oneimportant thing: No matter how much you pay for a mask, they only work if theyfit snugly(舒适地) on your face.

But, if they are made out of cloth, too tight is not good either.During his study, Peltier found that if a person pulled their cloth mask tootightly, it lost the ability to filter anything.

False sense of security

You might think that wearing any type of face mask is better thanwearing nothing at all.

“Wearing a face mask – an inexpensive(便宜的), non-working face mask made out of cloth – does give a falsesense of security because it makes you feel like you’re being protected when infact you’re not. You feel like you’re doing something good for your body toprotect yourself from air pollution. But in reality it’s not doing anything atall or it’s doing very little.”

Peltier adds that this false sense of security might prevent youfrom taking other measures to protect yourself, such as avoiding highlypolluted areas or avoiding outside exercise during times of very highpollution.

Health officials around the world warn that air pollution is onlygetting worse. And not just in poorer countries.

“Air pollution is a global problem and it is growing in magnitude across the planet. And individuals(个人) can make informed(消息灵通的) decisions about reducing their exposure to air pollution, whether it’s through wearing appropriate(适当的) masks or avoidingan exposure that will, in fact, have health benefits(利益) to that individual.”

And that’s the Health & Lifestyle report.

I’m Anna Matteo.

 


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