Quantifying the Health Benefits of Face Masks and Respirators to Mitigate Exposure to Severe Air Pollution

Familiarity with the use of face coverings to reduce the risk of respiratory disease has increased during the coronavirus pandemic; however, recommendations for their use outside of the pandemic remains limited. Here, we develop a modeling framework to quantify the potential health benefits of wearing a face covering or respirator to mitigate exposure to particulate air pollution. This framework accounts for the wide range of available face coverings and respirators, fit factors and efficacy, air pollution characteristics, and exposure-response data. Our modeling shows that N95 respirators offer robust protection against different sources of particulate matter, reducing exposure by more than a factor of 14 when worn with a leak rate of 5%. Synthetic-fiber masks offer less protection with a strong dependence on aerosol size distribution (protection factors ranging from 4.4 to 2.2), while natural-fiber and surgical masks offer reductions in the exposure of 1.9 and 1.7, respectively. To assess the ability of face coverings to provide population-level health benefits to wildfire smoke, we perform a case study for the 2012 Washington state fire season. Our models suggest that although natural-fiber masks offer minor reductions in respiratory hospitalizations attributable to smoke (2%-11%) due to limited filtration efficiency, N95 respirators and to a lesser extent surgical and synthetic-fiber masks may lead to notable reductions in smoke-attributable hospitalizations (22%-39%, 9%-24%, and 7%-18%, respectively). The filtration efficiency, bypass rate, and compliance rate (fraction of time and population wearing the device) are the key factors governing exposure reduction potential and health benefits during severe wildfire smoke events. Plain Language Summary The use of face coverings (e.g., cloth masks, surgical masks, and N95 respirators) has increased dramatically during the coronavirus pandemic; however, recommendations for their use outside of the pandemic, for example, during wildfire episodes, remains limited. In this study, we investigate the potential health benefits of wearing a face covering to reduce the amount of inhaled particulate air pollution. Our model accounts for different types of face coverings, how well they fit, the characteristics of air pollution, and the risk of air pollution causing respiratory disease. We find that N95 respirators, a special type of face covering that meets regulatory standards, offer a promising means to reduce the inhalation of particulate air pollution and thereby reduce the risk of negative health effects; however, the public health benefits are strongly dependent on how often the respirator is worn and by how many people. In a case study in Washington state in 2012, we estimate that the use of N95 respirators could reduce respiratory hospitalizations caused by wildfire smoke by 22%-39%. Conversely, cloth masks offer only limited protection against air pollution due to poor filtration efficiency and poor fit.

Automated summary

The study explored the potential health benefits of wearing face coverings to reduce inhaled particulate air pollution. N95 respirators showed promising results in reducing inhalation of particulate matter, while cloth masks offered limited protection. Public health benefits heavily rely on wear frequency and population compliance with face coverings, with N95 respirators potentially reducing respiratory hospitalizations from wildfire smoke by 22%-39%.