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  • Seth Coe-Sullivan

It's the Aerosols, Stupid

Updated: May 14

Air quality and health (AQH) experts have believed for a long time that coronavirus germs in aerosols, which are exhaled with your breath and can float in the air for hours, are a primary means of Covid-19 infection. But public health authorities have only recently (finally) acknowledged that aerosols have been a major cause of the “super-spreader” events that helped elevate isolated outbreaks into epidemics and finally into a global pandemic.

Source: Aolto University via YouTube


Initially, public health experts discounted the impact of aerosols, believing Covid-19 was spreading through physical contact with viruses in fomites on surfaces and in droplets that only travel several feet through the air. The World Health Organization (WHO) and U.S. Centers for Disease Control (CDC) fell back on a long-term consensus that viruses such as the flu and common cold were spread via heavy droplets in sneezes or coughs that quickly fall to the ground or other surfaces. Therefore, at the outset of the pandemic, they recommended social distancing, hand-washing, and deep surface cleaning to prevent infection, but they said face masks weren’t helpful or necessary. We all started to disinfect the groceries before we loaded them into the fridge.


Now, however, a growing body of research is demonstrating that aerosols can infect people further than six feet away, especially in poorly ventilated indoor spaces. The highly respected health and medicine journal, The Lancet, recently published a summary of many findings in a commentary entitled “Ten Scientific Reasons in Support of Airborne Transmission of SARS-CoV-2.


WHO and CDC Acknowledge Aerosols Help Transmit Covid Infections


On April 30, 2021, more than a year into the pandemic, the WHO updated its guidance to acknowledge that airborne transmission over longer distances was a primary means of Covid-19 transmission. And on May 7 the CDC followed suit with a major update, “SARS-CoV-2 is Transmitted by Exposure to Infectious Respiratory Fluids,” that for the first time acknowledges the fact that aerosols are a principal mode of infection over distances of more than six feet:


“The principal mode by which people are infected with SARS-CoV-2 (the virus that causes COVID-19) is through exposure to respiratory fluids carrying infectious virus. Exposure occurs in three principal ways: (1) inhalation of very fine respiratory droplets and aerosol particles, (2) deposition of respiratory droplets and particles on exposed mucous membranes in the mouth, nose, or eye by direct splashes and sprays, and (3) touching mucous membranes with hands that have been soiled either directly by virus-containing respiratory fluids or indirectly by touching surfaces with virus on them.”


The CDC added that “the smallest very fine droplets, and aerosol particles formed when these fine droplets rapidly dry, are small enough that they can remain suspended in the air for minutes to hours.” Why is this new finding important? Because it will encourage more people, employers, and institutions to focus on the core problem of airborne infection.


Now We Know What Interventions to Focus On


What interventions make the most sense? There are two, one of them familiar, and the other less so.


The first is easy: wear a face mask, especially indoors. There’s a growing body of research demonstrating that wearing face masks at indoor gatherings in poorly ventilated spaces where aerosols linger the longest can dramatically reduce infection rates. When everyone wears a mask, the odds of a “super-spreader” event diminish rapidly.


The second intervention is widespread disinfection with UVC light. It’s less well-known and currently used less than it could or should be. But it’s a tried-and-proven disinfectant, especially for airborne viruses. Invisible UVC light has been used in hospitals for a hundred years, starting with disinfection of the air in tuberculosis wards.


Until recently, however, most UVC light sources emitted disinfecting light at 254 nanometers, which can harm human skin and eyes with symptoms akin to sunburn and snow blindness. As with sunlight, long-term exposure can also lead to cancer. Therefore, UVC disinfection was limited to cleaning surfaces at night or other times when spaces were unoccupied, or to ceiling-mounted systems that disinfected some of the air circulating in the upper room without exposing people in the room below.


But over the past several years, researchers at Columbia University, Kobe University, and elsewhere have demonstrated that a shorter wavelength of UVC light—“far-UVC” light at 230 nanometers or less—can be used more safely around humans. It deactivates pathogens equally well, but its shorter wavelength means it does not penetrate skin or eyes deeply enough to cause long-term damage.


Practical, Cost-Effective, Human-Safe Far-UVC Light


As further studies confirm that far-UVC disinfection is human-safe, the possibilities for effective disinfection of the air in public and private spaces become nearly limitless. Constant disinfection of the air with human-safe far-UVC light should make it possible to significantly reduce the viral load anywhere people congregate. Always-on far-UVC light could make offices, airports and airplanes, trains and train stations, convention centers, buses, personal autos and ride-shares, theaters, and literally any other location where people gather far less likely to spread the contagion.


That’s why at NS Nanotech we have developed the first solid-state far-UVC solution, the ShortWaveLight™ Emitter. Our semiconductor-based far-UVC lamp is smaller than other current far-UVC excimer gas lamps and ultimately will follow a cost-reduction curve similar to other chip-based businesses.


With acknowledgement by public health authorities that airborne aerosols are a principal means of viral infection, our new light source comes at a good time. In addition to our own personal ShortWaveLight™ Purifier for consumers, which uses far-UVC light to sanitize your personal airspace, we’re already talking to many manufacturers who want to design the far-UVC ShortWaveLight™ Emitter into long-term infrastructure solutions that can deliver ubiquitous, human-safe UVC disinfection in public and private spaces worldwide.


For a deeper dive into how far-UVC disinfection infrastructure solutions can be integrated into our built environment, read my previous blog post, Rebuild for the Pandemic Era with Disinfecting UV Light.



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