BU’s Mask Policy is Inadequate

This is a guest post by Professor Nathan Phillips, Department of Earth and Environment, Boston University.

In light of national and Massachusetts trends in COVID cases, the wisdom of re-opening BU in three weeks is becoming increasingly questionable. But if BU is going to re-open this fall, among all the safety measures it is taking, it needs to address a big safety gap in its present approach: its mask policy.

To cut to the chase, BU should make a bulk purchase of properly-vetted KN95 masks for the university community, as a key part of a prudent strategy to reduce risk of airborne transmission. Institutionally-vetted KN95 masks are preferable to N95 masks for BU because of a shortage of N95 masks that is due to the need to prioritize the requirements of front-line healthcare workers and first responders.

Our current policy is inadequate because it takes a collective action problem, and views it simply as an individual matter. Choices regarding masks matter for indoor airborne transmission, and leaving this type of decision to tens of thousands of individuals will lead to highly uneven individual choices that will have bad effects on the whole community. Currently, for example, the use of bandanas would be allowed. Bandanas are effective at preventing ballistic transmission, but poor at blocking viral aerosols. Even those who might choose a KN95 mask could easily buy a faulty one by mistake, as this recent report makes clear. BU needs a community-level solution to a community-level problem. Masks must be considered not just PPE, but Community Protective Equipment, and part and parcel of the university’s ventilation strategy.

I appreciate that BU has begun to address concerns about building ventilation in light of mounting evidence of the potential for airborne COVID transmission. While this is laudable, these steps, which include increasing air exchange rates and installing HVAC filters, are missing both the very first and the last lines of ventilation defense: masks. Properly fitted and filtered masks inhibit aerosol transmission both at the source, and at the end point of potential infection. If we are investing time and expense in retrofitting rooms with improved HVAC filters, we should also be considering the quality of facial filters.

A recent Harvard-Illinois IT study of COVID transmission on the Diamond Princess Cruise Ship found that, despite good ventilation on this ship, airborne transmission was a likely major route of transmission. A NY Times review of this study states:

But good ventilation is not enough; the Diamond Princess was well ventilated and the air did not recirculate, the researchers noted. So wearing good-quality masks — standard surgical masks, or cloth masks with multiple layers rather than just one — will most likely be needed as well, even in well-ventilated spaces where people are keeping their distance.”

To be sure, the science is not settled and the cited study, a preprint, is one study, but the physical mechanisms posited as being involved make for a highly plausible causal account, and with the health and welfare of tens of thousands of people at BU on the line, as well as the lives of hundreds of thousands of people across greater Boston at risk, use of the precautionary principle is strongly warranted. If a bulk order can procure vetted KN95 at $2/mask, this is well worth an $80,000 university investment in community safety (supposing we need masks for 40,000 people). While there are risks with extended use of respirators like N95, they have been recommended for re-use under conditions of scarcity.  Compliance and enforcement is an important related issue, but due diligence would mean providing at least one properly-vetted KN95 mask to every member of the university community.  

The mask I wear affects you; the mask you wear affects me; the masks we all wear potentially affect everyone in the BU community. We need a community-level solution to this problem.