EPA Researchers Study Aerosol Transport and Mitigation Measures to Reduce COVID-19 Transmission
Published November 10. 2020
As we learn more about SARS-CoV-2, the virus that causes COVID-19, there is mounting evidence that aerosols - airborne particles that are released through normal human breathing and speech, as well as through coughing and sneezing - are playing a role in transmission of the disease. Larger respiratory particles or droplets are commonly released during coughing or sneezing but only travel short distances before settling out of the air. Risks from exposure to these larger droplets are a primary reason for the public health recommendation for 6 feet of physical distancing. However, we also know that respiratory aerosols include many smaller particles that have the potential to carry viruses within them and can linger in the air, much like smoke. These smaller particles can travel longer distances and can build up in indoor air, especially when ventilation is poor. These factors can increase the potential for viral exposures.
As people gather in indoor spaces, such as schools and businesses, and increase ridership on mass transit, safe and effective mitigation measures and technologies are needed to help reduce the spread of the disease.
EPA researchers are working on a variety of projects to learn more about this issue. To determine how far exhaled aerosols spread in an office environment, EPA researchers are studying indoor air pathways. The focus of this work will be on an "open office" or a cubicle work environment where there is concern about the potential for direct movement of aerosols from an infected (though likely asymptomatic) individual to the breathing zones of individuals at other workstations in the office space. EPA researchers will first seek to determine baseline levels of exposure from aerosol transport and then test the impact of practical office modifications that could potentially reduce viral exposure.
Paul White, an EPA researcher leading this project says, “The potential spread of virus particles in aerosols in indoor air has been a concern to scientists and public health authorities. We want to understand better how these aerosols may move in an ordinary office environment. We are using computational models to predict the quantity of virus containing particles that could be transported in the air and will then investigate how relatively simple changes to the workplace may reduce potential for spread of COVID-19."
While EPA research is ongoing, businesses and employers should continue to follow CDC guidelines and recommendations.
Researchers are also evaluating technologies that are safe to operate in occupied spaces and that may be capable of reducing the amount of SARS-CoV-2 in the air. Researchers will assess the effectiveness of different devices, such as ultraviolet light devices, chemical-based devices and products, and filters and passive air cleaners, to reduce infective virus on surfaces and in the air. The researchers are building on a foundation of research on SARS-CoV-2 surface disinfection started earlier this spring in mass transit settings, which was done collaboratively with New York City Metropolitan Transit Authority (NYC MTA) and the Los Angeles Metropolitan Transit Authority.
“Everyone wants to know how to safely bring people into enclosed spaces, for example restaurants and business spaces, particularly as we are coming into winter,” said EPA researcher Katherine Ratliff, EPA researcher leading these research efforts. “Mass transit agencies across the country are going to great lengths to ensure the safety of their ridership, and using technologies that would potentially reduce the airborne transmission of COVID-19 could be part of a holistic and comprehensive approach to create a safer environment for their customers,” she adds.
EPA researchers are also participating in a study led by researchers at the Department of Homeland Security Science &Technology and NYC MTA that will assess the behavior of aerosols in buses and subway train cars. This field assessment and modeling effort is investigating the impact of ventilation on reducing aerosolized virus in enclosed or semi-enclosed environments.
Results from this research are expected later this winter and will provide a foundation for community leaders around the country to make decisions based on the best available science to keep people in workplaces, restaurants, and other indoor areas as safe as possible.