loading animation

— Research


How aerosols have contributed to the silent spread of COVID-19 around the globe

Over the course of the COVID-19 pandemic, it became clear that the predominant way people were becoming infected was through air transmission — and this was not being acknowledged. As an atmospheric chemist who has spent my entire career studying aerosols, I know first-hand how far aerosols can float through the air. I became deeply concerned and thus have spent much of the past year focusing on communicating the latest scientific evidence about the major role of aerosol transmission in silently spreading SARS-CoV-2 around the globe.

During a “normal” year, my research at UC San Diego focuses on understanding how aerosols — microscopic airborne particles — affect our atmosphere, climate and human health. I am particularly interested in bioaerosols and pathogens that get ejected from the ocean in coastal regions. Sorting out the impacts of aerosols in field studies is challenging, so my colleagues and I have transferred the full complexity of the ocean and atmosphere into the lab at Scripps Institution of Oceanography using a large wave channel. This unique approach to isolating the ocean/atmosphere system allows us to study how physical, chemical and biological processes in the ocean affect the composition of marine aerosols and their ability to seed marine clouds over 71 percent of the Earth, which strongly impacts our climate.

Throughout the pandemic, I have been deeply concerned that public health agencies, including the World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC), were too narrowly focusing their guidance on protecting against large respiratory droplets. This resulted in an emphasis on advising people to clean surfaces, something now labeled as “hygiene theater.”

Changing this “droplet dogma” has required an intense international grassroots effort imploring the medical community to update their longstanding picture of the transmission modes of respiratory viruses, and at the very least to apply the precautionary principle to better protect health care workers and those at high-risk.
Decades of scientific research have shown that large droplets fall within six feet. Aerosols float. In fact, they can travel thousands of miles around the globe. The only way to explain the thousands of documented superspreader events is by including aerosol transmission. The vast majority of outbreaks have occurred indoors — in places like churches, cruise ships, gyms, nursing facilities and bars.

These outbreaks all have one thing in common: all of those who were infected shared the same indoor air. Similar to the way cigarette smoke builds up and spreads across a room, it only takes one person infected with COVID-19 to expose everyone in poorly ventilated indoor spaces.

Over the past year, I have co-authored several high-profile publications on aerosol transmission along with other aerosol and medical experts, including UC San Diego’s Robert “Chip” Schooley, MD. In The Lancet, for example, we outlined 10 lines of evidence supporting the airborne transmission of SARS-CoV-2 as the predominant pathway. I have done more than 1,000 media interviews on this topic. In addition, I’ve spent significant time advising government officials at local and federal levels on how to safely re-open, encouraging them to focus on cleaning the air. I have also worked closely with a group of UC San Diego experts to help the San Diego Unified School District safely reopen schools.

“And I’ve had conversations with numerous high-ranking officials, including Anthony Fauci, MD, director of the National Institute of Allergy and Infectious Diseases, to alert them to the importance of acknowledging the role of aerosol transmission.”

And I’ve had conversations with numerous high-ranking officials, including Anthony Fauci, MD, director of the National Institute of Allergy and Infectious Diseases, to alert them to the importance of acknowledging the role of aerosol transmission.

Our work to fully understand the role of aerosol transmission is just getting started. It is highly likely that SARS-CoV-2 is not the only respiratory virus that is spread through aerosols. A retrospective analysis of the transmission pathways for other respiratory viruses is already underway.

I am encouraged that we are starting to see our communication efforts pay off. WHO and CDC have updated their guidance. I am proud of the impact this international group of determined scientists has had in turning our understanding of COVID transmission around.

Once the role of aerosol transmission is clearly acknowledged globally, then we know what steps to take to help end this pandemic. Efforts need to focus on enhancing ventilation and filtration to improve air quality indoors where most infections occur. The long-term benefits of having cleaner indoor air in homes, schools and businesses are enormous. They extend well beyond this pandemic and can improve public health for generations to come.