Included in Issue: Spring 2021

The Efficacy of Face Mask Materials

from Kerry E. Kelly

Face masks are a key strategy to reducing the spread of the SARS-CoV-2 virus. Two recent studies consider their effectiveness.

Aerosol Filtration Efficiency of Common Household Materials

This recent AS&T article by Drewnick et al. examined the filtration efficiency of common household materials for use as masks.  Their measurements showed that leaks are critical. A small fractional leak area, just 1–2%, can dramatically reduce filtration efficiency. This is especially true for particles smaller than 5 µm diameter, where filtration efficiency decreases by 50% or more in response to these small leaks. They also found large differences in filtration efficiency associated with materials and with different particle sizes, ranging from 10 to nearly 100% removal.  However, they demonstrated that layers of materials can yield good filtration efficiencies over a range of particle size.

Quantitative Protection Factors for Common Masks and Face Coverings

A recent article by Leith et al. examined how well face coverings protect the wearer from inhaled infectious aerosol. They evaluated seven types of common face coverings and found that the protective ability of reusable masks made from cotton fabric was limited by the size of the native cotton fibers. However, face coverings made from finer fibers, particularly electret fibers with relatively small diameters, showed excellent performance with moderate flow resistance.

In the media:

Measuring the Presence of Viable Viruses

Identifying viable SARS-CoV-2 virus in aerosols has been a challenge because virus particles collected by various air samplers become inactivated during the air sampling process.  A recent study by Lednicky et al. employed water vapor condensation to collect and isolate viable SARS- CoV-2 virus from hospital settings. They were able to identify viable SARS-CoV-2 from air samples collected 2 to 4.8 m away from the COVID-19 positive patients. This data helps to support epidemiologic research that aerosols may serve as a source of transmission of the virus. Read the whole piece now.

The New Biden Administration and Air-Quality Policy

Under a January 20, 2021 executive order, the Biden administration initiated a review of nearly 20 air-quality regulations based on concerns over the lack of supporting data.  These include national ambient air quality standards for fine particulate matter and ozone as well as GHG emission standards. The new EPA leadership is also expected to review several Trump-administration rules, including the controversial “Secret Science” and “Cost Benefit Analysis” rules, that it alleges hamper the agency’s ability to use the best available science to make policy. The new administration will also be scrutinizing rules that have not yet taken effect.  It directed agencies to consider postponing effective dates for 60 days for rules that have not yet taken effect and to consider opening a 30-day comment period to for some rules.