White cloth masks are ubiquitous in many Asian cities where urban commuters must daily battle significant pollution, but new research suggests the masks offer limited protection from harmful particulates.

Scientists at the University of Massachusetts Amherst tested the level of protection provided by several types of the most commonly used washable cloth and surgical masks. The results were less than stellar.

"Wearing cloth masks reduced the exposure to some extent," researchers reported in their paper, newly published in Journal of Exposure Science and Environmental Epidemiology, "[but] the most commonly used cloth mask products perform poorly when compared to alternative options available on the market."

Lead study author Richard Peltier says the masks may offer people a false sense of security, giving them confidence to visit highly polluted places or venture outside when pollution problems are especially bad.

"What became clear to us is that millions of people probably wear these masks and feel safer, but we worry that this is potentially making things worse, if they stand next to a diesel truck and think they are protected by the mask, for example," Peltier said in a news release.

Peltier first became interested in the efficacy of cloth masks after seeing the extent of their use in Katmandu, which has tremendous pollution levels. A bad pollution day in Katmandu can feature levels as high as 800 to 900 micrograms of particulates per cubic meter.

"We found ourselves wondering how effective these masks are," Peltier said. "I was shocked that we couldn't find any research studies investigating them."

While the least expensive cloth masks were able to keep out upwards of 65 percent of larger particles, they failed to effectively guard against particulates smaller than 2.5 micrometers. Smaller particulates are considered more harmful than large particulates.

The study's results show the most inexpensive and most popular masks used in Nepal, China, India and much of Southeast Asia are also the least effective.