Effectiveness of face masks used to protect Beijing residents against particulate air pollution

Abstract

ObjectivesMany residents in Beijing use disposable face masks in an attempt to protect their health from high particulate matter (PM) concentrations. Retail masks may be certified to local or international standards, but their real-life performance may not confer the exposure reduction potential that is marketed. This study aimed to evaluate the effectiveness of a range of face masks that are commercially available in China.MethodsNine masks claiming protection against fine PM (PM2.5) were purchased from consumer outlets in Beijing. The masks’ filtration efficiency was tested by drawing airborne diesel exhaust through a section of the material and measuring the PM2.5 and black carbon (BC) concentrations upstream and downstream of the filtering medium. Four masks were selected for testing on volunteers. Volunteers were exposed to diesel exhaust inside an experimental chamber while performing sedentary tasks and active tasks. BC concentrations were continuously monitored inside and outside the mask.ResultsThe mean per cent penetration for each mask material ranged from 0.26% to 29%, depending on the flow rate and mask material. In the volunteer tests, the average total inward leakage (TIL) of BC ranged from 3% to 68% in the sedentary tests and from 7% to 66% in the active tests. Only one mask type tested showed an average TIL of less than 10%, under both test conditions.ConclusionsMany commercially available face masks may not provide adequate protection, primarily due to poor facial fit. Our results indicate that further attention should be given to mask design and providing evidence-based guidance to consumers.

Bushfire smoke: urgent need for a national health protection strategy

“…Much of the media attention during periods of bushfire smoke relates to the use of facemasks. These are increasingly used by the general public in highly polluted Asian cities, particularly in China . Use of facemasks during brief air pollution episodes (outside occupational settings and extreme air pollution emergencies related to volcanic eruptions) is not routinely recommended by health authorities.…”

“…Surgical masks may have reasonable filtration efficiency; however, their design generally confers poor facial fit and high inward leakage of PM 2.5. Professional P2 or N95 facemasks, which can provide very efficient filtration of PM 2.5 if well fitted, are only designed for adults and can make breathing more difficult and increase thermal discomfort . More research is needed on the longer term health benefits and potential drawbacks of different types of facemasks for adults and children.…”

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“…The better fit to the face is an important reason why FFP respirators provide a better level of protection than surgical masks. Our research with fine dust suggests that wearing a surgical mask might on average reduce aerosol concentrations by ~70% but FFP respirators should on average reduce concentrations inhaled by >95% [12,13]. However, this relies on the mask fitting and being worn correctly.…”

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“…While powered air purifying respirators may be a solution for protecting healthcare workers (Brosseau, 2020), these are unlikely to be practical in many lower risk work settings. Wearing surgical masks is likely to reduce inhalation of very small droplets by 20 to 30% whereas a disposable respirator certified to an appropriate standard can, on average, reduce the concentration by 95% (Cherrie et al, 2018;Steinle et al, 2018). There is the potential that wearing masks may discourage people from touching their face or, conversely, could increase such activity due to frequent moving of the mask, unconscious 'fidgeting' or from irritation of the area around the nose and mouth: there is a need for research to examine the frequency of hand to peri-oral contact during mask wearing in different environmental situations.…”