Face masks available to consumers in China for protection against air pollution vary widely in their real-world performance, suggests a recent study.
Although a mask may filter tiny particles as advertised, face size and shape as well as movement can lead to leakage as high as 68 per cent, researchers report in Occupational & Environmental Medicine.
"Even if the filtration efficiency of the mask is high, and the mask fits the person initially, the mask may not continue to give a good fit as the person goes about their daily activities - walking, talking, and more," said senior study author Miranda Loh, an exposure and environmental scientist at the Institute of Occupational Medicine in Edinburgh, Scotland.
"It is important for people to understand that not all masks are effective at reducing exposure to particles in air pollution," Loh said in an email. "And none of these masks reduced the concentration of pollution gases such as nitrogen dioxide."
Although masks sold for workplace use generally must meet rigorous standards, there are few controls on masks marketed to consumers and little information on which mask will offer the best protection, the study team writes.
Their assessment of a sampling of masks in Beijing is part of a larger project funded by the Research Councils UK, examining air pollution in the Chinese capital and its health effects.