Objectives Many 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.
Methods Nine 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.
Results The 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.
Conclusions Many 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.
- exposure assessment
- air pollution
- diesel fumes
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Contributors JWC conceived the current study and, with ML, supervised the work and wrote the manuscript. Study concept and design were based on prior proposals conceived by CJH and JWC. AA carried out the experiments. HC and ML helped develop the current study design and contributed to the data interpretation. ML also cosupervised the work. SS and AS assisted with the experimentation. WM carried out the data analysis. CL assisted with the study in Beijing, translated materials into English and contributed to the data interpretation. All authors contributed to drafting the manuscript and have read and approved the final text.
Funding This project was funded by NERC/MRC grant NE/N007182/1 from the Newton Fund. The filtration and volunteer chambers were developed for this study and for Horwell’s Health Interventions in Volcanic Eruption crises (HIVE) project, funded under the Research for Health in Humanitarian Crises (R2HC) Programme by DfID and the Wellcome Trust.
Competing interests The Institute of Occupational Medicine undertakes a wide range of commercial testing related to occupational and environmental health, some of which has been for respirator manufacturers.
Patient consent Obtained.
Ethics approval Ethical approval for the volunteer tests was obtained from Heriot Watt University, School of Life Sciences Ethics Committee (Reference 2015-165). All participants provided informed consent. They were able to withdraw from the study at any time, without having to give a reason.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement There are no unpublished data from this article that this applies to.