Researchers Demand That WHO Look at Airborne Transmission of COVID-19

The evidence has been piling up for months.

virus transmition
The coronavirus spreads a lot more than six feet.

Lidia Morawska et al

It must be hard, running the World Health Organization (WHO) in the middle of a fast-moving pandemic. It's supposed to provide the best advice, the consensus of the smartest people from all countries of the world, but it's under attack from all directions.

Seriously, this is the pot calling the kettle black. And he is not alone; recently a group of 239 researchers published a letter, "It is Time to Address Airborne Transmission of COVID-19," with a zinger of a first paragraph:

We appeal to the medical community and to the relevant national and international bodies to recognize the potential for airborne spread of COVID-19. There is significant potential for inhalation exposure to viruses in microscopic respiratory droplets (microdroplets) at short to medium distances (up to several meters, or room scale), and we are advocating for the use of preventive measures to mitigate this route of airborne transmission. 

The WHO acknowledges that there may be an issue; Dr. Benedetta Allegranzi, the WHO's head of the committee studying infection, says the possibility of airborne transmission, especially in “crowded, closed, poorly ventilated settings, cannot be ruled out.”

None of this will be news to regular readers of Treehugger; we are obsessed with indoor air quality on this site, and have been talking about this issue for months, often quoting Dr. Miller. We wrote in March that "the virus can remain viable floating in the air for some number of hours." In April, we covered the story of the restaurant in Guangzhou, where the air conditioning unit spread the virus around the room.

particle settling vs size
small particles float for over a day. ASHRAE 

In fact, back in April, the air conditioning and ventilation experts in Europe and the USA were all recommending changes in air handling. We quoted REVHA, the Federation of European Heating, Ventilation and Air Conditioning Associations:

Small particles (<5 microns), generated by coughing and sneezing, may stay airborne for hours according to the REHVA guidance, and can travel long distances. A Coronavirus particle is only 0.8 to 0.16 microns diameter so there could be many virus particles in a 5-micron droplet floating around in the air.

Oh, and in May we worried about what happens in summer when all the air conditioning is blasting on full and everyone is inside trying to stay cool.

The WHO's recommendations were based on the best science at the time, which was based on research in hospitals. It was also advice that could be followed relatively easily: wash your hands, stay six feet apart. Acceptance that the coronavirus is airborne has profound implications and could mean big changes in how we deal with the virus. The researchers note:

Hand washing and social distancing are appropriate, but in our view, insufficient to provide protection from virus-carrying respiratory microdroplets released into the air by infected people. This problem is especially acute in indoor or enclosed environments, particularly those that are crowded and have inadequate ventilation.

The researchers make similar recommendations to those made by the HVAC engineers noted earlier:

  • Provide sufficient and effective ventilation (supply clean outdoor air, minimize recirculating air) particularly in public buildings, workplace environments, schools, hospitals, and aged care homes.
  • Supplement general ventilation with airborne infection controls such as local exhaust, high-efficiency air filtration, and germicidal ultraviolet lights.
  • Avoid overcrowding, particularly in public transport and public buildings. 

The researchers say that "such measures are practical and often can be easily implemented; many are not costly." This is a gross oversimplification. Almost every air conditioning system in the USA is based on recirculating air. Engineers can't simply dial up more fresh air, especially in the heat of summer; as I wrote earlier:

Engineer and Professor Ted Kesik told Treehugger that 'we shall be greatly challenged retrofitting our existing buildings to eliminate dilution ventilation systems.' This is especially a challenge in the heat of a southern summer, where the difference between inside and outside air can be 40°F in Arizona or Texas. In the Southeast, there is also a lot of humidity with the heat. That's why the air is recirculated; the amount of energy needed to condition a mall's worth of outside air would be ridiculously high.

If you want to have high-efficiency air filtration, you need both way bigger boxes for the filters and way bigger motors for the fans. New construction will have to be built to much higher energy efficiency standards (with much smaller windows) or the heating and cooling costs will be astronomical. Existing building retrofits will take years. This is not like dialing up a thermostat. As I noted earlier,

All of these modifications are expensive, either in equipment or operating costs. All of these building owners and tenants have been bleeding money in the last few months. All of the companies making this equipment are going through the crisis, too. In short, it is probably safe to say it's not gonna happen, at least in the short term.
Trump rally
Lots of people crowded together without masks in Tulsa.  Win McNamee/Getty Images

Then there is the need to "avoid overcrowding, particularly in public transport and public buildings." This should mean the end of super-spreader events like Trump rallies, and how do people who depend on transit get to work?

It's great that the WHO is finally addressing this problem, but one can see why they have been avoiding it. The implications are huge.