Newspaper article International New York Times

Many Masks Are Useless against Smog

Newspaper article International New York Times

Many Masks Are Useless against Smog

Article excerpt

As Asian cities deal with pollution, health professionals seek more research about devices' effectiveness and better education for consumers.

CORRECTION APPENDED

When smog descends on Beijing or other Asian cities, people rush to buy face masks.

But how effective are the masks at filtering out tiny, harmful particles of pollution?

The effectiveness varies tremendously, depending on factors like type, brand and fit. Simple, loosefitting masks do little to combat pollution, according to the United States Food and Drug Administration, whereas more advanced, government-approved respirators that bind tightly to the wearer's face can help but may be uncomfortable. More public education and research are urgently needed about face masks, health professionals say.

"Consumers simply just don't know which of those masks are the best," Richard Saint Cyr, a physician in Beijing who writes a health column for the Chinese-language T Magazine once a month, said in an email. "And some indeed may be worse than helpful if people are falsely reassured and spend more time outside using a mask which doesn't work."

Many masks worn around Asia are simple surgical-type masks. But these are designed to prevent problems like splattering blood, not to block tiny particles, Benjamin Cowling, an associate professor of public health at the University of Hong Kong, said in an email. "It is pretty common knowledge that surgical face masks have almost no filtration efficiency against pollutants," he said.

Surgical masks are made of polypropylene, according to Wallace Leung, director of the Research Institute of Innovative Products and Technologies at the Hong Kong Polytechnic University. His tests found that at a standard airflow velocity, basic masks captured only 20 to 25 percent of tiny particles of 50 to 500 nanometers -- a size common in diesel vehicles' exhaust. Such particles, less than 1 percent of the width of a human hair, are of particular concern because they can get buried deep in the lungs and end up in the bloodstream. The figures do not include any gap between the mask and the face that allows air to come in.

"What it means is, if you wear a face mask, you get 75 to 80 percent into the body," Dr. Leung said.

A better bet, experts say, are respirators that guard against at least 95 percent of small particles. Sometimes known as N95 respirators, they use thick layers of polypropylene, according to Dr. Leung, and are designed to fit tightly to the face. In the United States, such masks get tested by the National Institute for Occupational Safety and Health and must be shown to keep out at least 95 percent of all tiny airborne particles to gain approval. They are often used by industrial workers and are generally disposable.

One widely sought-after brand is 3M. The Minnesota-based company recently announced that it would invest $15 million in a Singapore plant to increase production of its N95 respirators by 70 percent. …

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