This, in Donald Milton’s opinion, is the perfect situation to spread the coronavirus.
Not only could people transmit the virus directly from one to the other in the tiny droplets we all spray to one degree or another when we speak, laugh, or sing; But those little drops also rise into the air where, Milton says, they can float for at least a while.
It is not a secret, but the agencies appear to be afraid to talk about the nature of the virus in the air, Milton said.
“The broadcast word on the air appears to be loaded,” Milton, one of the letter’s two main authors, told CNN.
“Most public health organizations, including the World Health Organization, do not recognize airborne transmission except for aerosol-generating procedures performed in healthcare settings. Handwashing and social distancing are appropriate, but in our view insufficient to provide protection against respiratory diseases carrying viruses, microdrops released into the air by infected persons, “they added.
“They don’t want to talk about broadcasting over the air because that will make people scared.”
“I suppose we hope the WHO comes along and is more willing to recognize the important functions of aerosols, whether they want to call it air transmission or not,” Milton said.
Milton studies the transmission of viruses in the air. The other lead author, Lidia Morawska, is a professor of environmental engineering and an expert in aerosol science at Queensland University of Technology in Brisbane, Australia. Milton said they and a group of other similar experts have been discussing possible airborne coronavirus transmission since February.
Milton said the group wants to demystify the word so that health agencies are less afraid to use it.
“They don’t want to talk about broadcasting over the air because that will make people scared,” he said. There is also an element of concern that if people think the virus is in the air, they will stop doing other things they must do to prevent transmission, such as washing their hands, staying apart, and cleaning surfaces.
“The best vaccine against fear is people’s knowledge and empowerment to take care of themselves,” said Milton. “I want them to understand how important it is to wash your hands. Why it is important to wear a mask is because it blocks aerosols at their source, when it is easy to block them.” It is harder to block aerosols once they are floating in the air, he said.
The virus is carried in drops that come out of people’s mouths and noses, and the sizes of those drops vary. Large droplets fall on surfaces quickly and can be picked up with the fingers and brought to the eyes, nose or mouth. Smaller drops can stay in the air longer and can be inhaled deeper into the lungs.
“There is significant potential for exposure by virus inhalation in microscopic respiratory droplets (microdrops) at short to medium distances (up to several meters, or room scale), and we are advocating the use of preventive measures to mitigate this route of air transmission. “Milton and his colleagues wrote.
“Studies by signatories and other scientists have shown beyond reasonable doubt that viruses are released during exhalation, conversation, and cough in droplets small enough to remain airborne and present a risk of exposure to distances of more than 1 to 2 meters (yards) from an infected individual, “they added.
“For example, at typical indoor air speeds, a 5 nanometer drop will travel tens of meters, much more than the scale of a typical room, while settling from a height of 1.5 meters (about five feet) to the floor”.
What is not clearly understood is how important droplet size is for coronavirus transmission, Milton said.
But studies show it’s a factor, added Milton. “A lot of people crowded inside, where it’s poorly ventilated, that’s what drives the pandemic,” he said. A noisy bar, where people must raise their voices to be heard, is a perfect storm of close contact, poor air circulation, and people who generate lots of virus-carrying particles by talking, laughing, and yelling.
He said the WHO is concerned about giving advice that people, especially health workers in low-resource settings, cannot follow. The best way to protect workers from fine aerosols is to wear an N95 or higher respirator, which is rare in many places.
Tips to avoid transmission of the coronavirus
But Milton said there are other ways, too, including improved ventilation, as well as distancing and wearing masks. And that is information that the average person, as well as health professionals, can use and act on.
“I am very concerned about the general public and schools and ventilation in school buildings and in dormitories on university campuses and in bars and churches and where people sing and where people congregate,” he said.
The group gives practical advice in their letter.
• Provide sufficient and effective ventilation (supply clean air outdoors, minimize air recirculation) particularly in public buildings, work settings, schools, hospitals, and nursing homes.
• Supplement general ventilation with airborne infection controls, such as local exhaust, high-efficiency air filtration, and germicidal UV lights. (These would be placed on top of the ceiling to avoid damage to people’s eyes and skin)
• Avoid overcrowding, particularly on public transportation and public buildings.
“Such measures are practical and can often be easily implemented; many are inexpensive,” they wrote.
“For example, simple steps like opening doors and windows can dramatically increase air flow rates in many buildings.”
In a car, Milton advises, open the windows and make sure that the air conditioning or heat is not recirculated, but includes outside air.
In buildings, carbon dioxide monitors can help managers know if the air is being renovated properly, Milton said. Outside, in an urban area, he said, carbon dioxide levels are about 350 parts per million in the air. The exhaled breath carries around 38,000 parts per million of carbon dioxide. Indoors, he said, if the air has 1,000 parts per million carbon dioxide or less, “that’s pretty good,” said Milton.
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