APR 08, 2020
This small-scale 2008 study assessed the level of protection offered by N95, surgical and homemade facemasks in the general population.
Three different experiments on 28 adults and 11 children were undertaken to assess short-term protection, long-term protection and effectiveness of masks in preventing outgoing transmission and inward protection. The authors tested 3 masks: a European equivalent of an N95 mask, a surgical mask with a filtering efficiency of around 95% for particles of sizes between 0.02 µm to 1 µm, and a homemade mask made from teacloth. Outward protection was measured via a mechanical head simulated patient.
In this study, all masks provided some level of protection against transmission, reducing exposure during all types of activities for both children and adults. As expected, mask type and fabric determined the level of protection, with the N95 equivalent mask providing 50 times more protection than homemade masks and 25 times more protection than surgical masks in adults. Children were significantly less protected compared with adults; this difference might be related to an inferior fit of the masks on their smaller faces. The study also found that all 3 types of masks provided a much higher degree of exposure protection against inward transmission of particles rather than preventing outward transmission.
The study is limited by its experimental model, small sample size, and short duration. Of significance, the impact of coughing or sneezing on outward transmission through a mask was not assessed. The study asked participants to simulate real-world activities during the testing, and with greater sampling and repeated testing models to calculate inward and outward transmission, the study results would likely be verified.
According to this study, any type of face mask use is likely to decrease viral exposure and infection risk to both the individual and general population, even when imperfect fit and adherence are accounted for. Homemade masks like those made from teacloths in the study may still confer a significant degree of protection, of course, to a lesser extent than surgical or N95 masks. In a pandemic, such as we are experiencing today with COVID-19, homemade masks may provide protection to the general public; patterns and materials are readily available to make these masks. The authors note that mask-wearing should form only one part of an approach integrating multiple effective interventions. Additional future research of aerosol and droplet inoculation and infectivity may provide better insight into the impact and transmission on population spread.