Some commercially available face masks may not provide adequate protection from harmful air pollutants due to poor facial fit, a study published this month has claimed.
Led by Dr Miranda Loh, a senior scientist at the Institute of Occupational Medicine, the study looked at the effectiveness of face masks purchased from consumer outlets in Beijing. Testing was carried out in a lab in Edinburgh.
The study, findings of which were published in the British Medical Journal last week, saw nine masks’ filtration efficiency against fine particulates tested by drawing airborne diesel exhaust through a section of the material.
Researchers measured the PM2.5 and black carbon (BC) concentrations upstream and downstream of the filtering medium.
Additionally, four masks were selected for testing on volunteers who were exposed to diesel exhaust fumes inside an experimental chamber while performing sedentary tasks and active tasks.
Black carbon concentrations were continuously monitored inside and outside the masks.
According to the researchers, the mean percentage of penetration for each mask material ranged from 0.26% to 29%, depending on the flow rate and mask material, the researchers claimed.
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, the study suggested.
The study concluded: “In spite of the generally good filtration efficiency of the tested mask materials, two of the masks performed poorly when worn because of inadequate fit to the face.
“These included a reusable mask with disposable filters and a single-fold disposable mask. The reusable mask cloth was loose, and the filters did not cover the whole surface area of the mask.
“These masks used elasticated ear loops to hold them onto the face rather than head straps. Even for the better-performing masks, some volunteers’ results indicated that the fit was not sufficient to ensure maximal performance of the mask.â€?
Researchers have concluded that rigorous and standardised testing, including volunteer trials, should be conducted to ensure the efficacy of all face masks available for consumer use against air pollution.
Consumers and regulators should be better informed about the exposure impacts of different mask types and how to ensure that masks fits appropriately, the researchers added.
“Many commercially available face masks may not provide adequate protection, primarily due to poor facial fit,â€? the report suggested. “Our results indicate that further attention should be given to mask design and providing evidence-based guidance to consumers.â€?