Airborne Coronavirus Transmission

Airborne Coronavirus Transmission

By Michael Riordan

Michael Riordan writes about science, technology and public policy.

The most troublesome aspect of the County’s application to move to Phase 3 of Governor Inslee’s Safe Start program was the proposal to increase restaurant occupancy levels from 50 to 75 percent. Scientific research increasingly points to the inhalation of virus-laden indoor air in confined spaces to be the leading cause of coronavirus transmission and Covid-19 infection. Going to 75 percent restaurant occupancy would only enhance that infection process.

As Professor Michael Osterholm of the University of Minnesota’s Center for Infectious Disease Research and Policy recently put it on NPR’s (appropriately named) program, Fresh Air, “Right now, we have to understand that the single greatest risk factor we have for transmitting this virus is largely via indoor air, where we’re in large crowds, where we are sharing that air with the people right around us.”

Other epidemiologists and public-health experts increasingly agree. According to an article in last Sunday’s New York Times, 239 scientists have written an open letter to the World Health Organization stating that airborne transmission via microscopic aerosol particles emitted during normal speaking is a major factor in coronavirus transmission — rivaling or outweighing that from larger droplets due to coughing or sneezing.

Thus expanding restaurant seating to 75 percent occupancy makes little sense — except to increase the number of diners able to be accommodated and the income thereby earned. It is obviously impossible to wear a mask while eating or drinking. So diners are inevitably exposed to the exhalations of others — including from mainlanders much more likely to be infected — for an hour or more. As restaurants expand from 50 to 75 percent occupancy, noise levels will increase substantially; diners would have to speak ever more loudly to be heard over the growing din. And according to scientific research, aerosol and virus emissions increase in proportion to speech loudness.

Restaurant servers and other employees can protect themselves by wearing high-quality masks that filter out micron-scale aerosol particles (one micron is a thousandth of a millimeter), such as the N95 masks commonly used by hospital workers. Ordinary cloth masks will not suffice. But hapless customers will have neither option unless they don’t eat or drink.

These problems will be exacerbated this summer by the fact that a large fraction of the customers — probably a majority, as concerned islanders avoid local restaurants — will be from the mainland, where the Covid-19 infection rates are much greater. I have tried to patronize some of my favorite Eastsound restaurants during the past two months, but only by takeout orders that I can pick up and then quickly depart, always wearing a mask indoors. It’s an approach I recommend to my fellow islanders.

If our County Councilors truly care about the welfare of our citizens, a third of whom are over 65 and therefore at heightened risk of death from coronavirus infection, they will withdraw their ill-considered request to increase restaurant occupancy to 75 percent — now on hold thanks to Governor Inslee — and instead remain at 50 percent for the rest of the summer.