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Aerosols and the need for masks

Updated on Jul 24
Tags: health and safety, all updates

For our American neighbours, few COVID-related issues have taken on more cultural and political salience than the decision whether to wear a mask. Despite clear evidence that masks can help protect others from infection, many choose to remain unmasked in public spaces.

To help us understand the University’s current position on masks (which follows below), I’ve asked Dr Andrew Cameron, chair of the University Recovery Planning Group and COVID-19 researcher, to explain aerosols and the risks they pose in enclosed spaces such as classrooms, hallways, elevators, and washrooms. Dr Cameron writes:

SARS-CoV-2, the virus that causes COVID-19, transmits between people primarily via direct contact with saliva and via respiratory droplets. Respiratory droplets are expelled during talking, shouting, singing, coughing, and sneezing.

Fortunately, these large (>5 µm) droplets fall in air, which is why 2 meters of physical distancing is recommended to reduce the risk of infection.

Unlike the larger ones, smaller droplet nuclei (<5 µm), also called aerosols, can remain suspended in air and travel over extended distances — in some instances, tens of meters. Highly infectious pathogens like measles and tuberculosis can transmit via aerosols as well as via respiratory droplets. Currently there is no direct evidence of airborne transmission of SARS-CoV-2, but this is an area of intense study because sensitive techniques can detect the virus suspended in air for extended periods of time after experimental aerosolization. Some scientists suggest that super-spreader events in offices, restaurants, and close-proximity events like choir practices are best explained by aerosol transmission, but presently the majority of evidence points to the main mode of spread being large droplets and contact.

Surgical and cloth masks are effective at reducing droplet and aerosol transmission, especially when worn by infected individuals. Recently in the United States, masks
helped prevent two symptomatic hair stylists from infecting over 140 clients and coworkers. Modelling shows that masks can stop the pandemic, even when they are only 50% effective at capturing exhaled virus and are even less efficient at blocking inhaled virus.

The World Health Organization provides a comprehensive overview of the potential for SARS-CoV-2 to transmit through different modes, including contact, droplet, airborne, fomite, fecal-oral, bloodborne, mother-to-child, and animal-to-human transmission.

Recently, other jurisdictions have made the wearing of masks mandatory in certain situations. The City of Calgary, for example, has passed a bylaw that effective 1 August will require people to wear masks in all indoor public spaces and while using public transit.

Additionally, the University’s Health, Safety and Wellness team has compiled information about masks. Please take time to read it.

  • Though the University of Regina is not yet mandating the wearing of masks, we now strongly recommend that all members of the University community wear a mask in public/shared spaces on our campuses (entrances, hallways, elevators, stairwells, etc.).

  • We also continue to ask people not to come to our campuses unless it is necessary to do so. To mitigate the risk of COVID-19 spreading on our campuses and throughout the community, it is important that the on-campus population be kept as low as possible.

The virus is not going away. Please be aware of what is happening in provinces and states around us. Protect yourself and others. Please also understand that this situation is changing rapidly, and may require more stringent precautions in the weeks to come.

Thomas Chase
Interim President and Vice-Chancellor