WHAT’S THE BEST WAY TO FACE UP TO POLLUTION?
Surprisingly, cheap, paper surgical masks fare well against airborne particles
ACROSS Asia, hundreds of millions of motorcyclists, bicyclists and pedestrians wear face masks to protect themselves against air pollution. The masks come in many sizes and colors: Car-exhaust black is the most common, but Hello Kitty pink, Nike swooshes and Burberry tan plaid have been spotted. What has been lacking, until now, is data on whether they actually work.
The consequences are serious. Air pollution is rapidly increasing in Asian cities; it contributes to many deaths from lung disease, and studies have shown that heavy smog quickly erodes lung function.
Environmental health scientists from the University of Massachusetts recently began testing masks they bought in street markets in Kathmandu, Nepal. Using a Styrofoam head, they found that the type of mask that is by far the most popular — inexpensive, washable cloth rectangles held in place by ear loops — provided little protection against the smallest particles, of less than 2.5 micrometers, that penetrate deepest into the lungs.
They were “better than nothing,” said Kabindra M. Shakya, an author of the study, which appeared in The Journal of Exposure Science and Environmental Epidemiology. But “wearers who stand next to a diesel truck and think they’re protected” were clearly at risk, said Richard E. Peltier, the lead author.
Cone-shaped cloth masks that cover the whole lower face and have exhalation vents did much better, removing up to 90 percent of the synthesized dust particles and almost 60 percent of the diesel exhaust that the researchers pumped through them.
The biggest surprise: Cheap paper surgical masks did quite well, almost as well as the U.S.made N-95 masks that the researchers used for comparison.
N-95s are certified by the National Institute for Occupational Safety and Health and block 95 percent of small airborne dust and mold particles. They are hard to find in Asia, however, and they cost $3 to $4 each.
“In Nepal, that’s a day’s salary,” Peltier said.
A pleated paper mask costs only about a nickel, but they are used once and then thrown away. Cloth masks cost 30 to 40 cents but are often washed and reused for a year.
With all masks, a snug fit is crucial. Air must be sucked through the filtering fabric, not around its edges. But when cloth masks were pulled so tight that they stretched, they stopped filtering any particles.
Although the paper masks are not typically snug, Peltier said they appeared to seal against a wearer’s wet lips.
Peltier’s team did its study while working on a larger, more formal study comparing the lung function and heart rates of traffic police in Kathmandu on days when they were protected by N-95 masks to days when they were not.
On bad days, Kathmandu’s smog, a mix of gasoline and diesel exhaust and burning garbage, has particulate levels nearly 10 times those of Los Angeles on a bad day.
The study of street masks was done on a very low budget, Peltier said. “It was about $5 worth of masks, a Styrofoam head, some tubing and a summer student’s time.”
Next, he said, he hopes to win a grant for a larger study with many more masks that incorporates lung-function tests on human subjects.