7/22/20 Photo illustration of droplets

"A sneeze or a cough can produce a wide size range of droplets," Park said. "Big droplets (of a) few micrometers can travel less than 6 feet. But some small droplets travel longer. After drying, a single virus may suspend in the air for a long time and travel longer."

Editor’s note: This interview with Jae Hong Park, a professor in the School of Health Sciences, took place earlier this summer regarding the safety of classrooms during the pandemic. Park said he has not changed any of his courses to online since the interview. Park’s research concentration focuses on aerosol science, and the dynamics, synthesis and control of aerosols, according to his biography.

Answers have been lightly edited for length and clarity.

From what you know about how viruses and aerosols work, how quickly can being in an enclosed classroom space with, say, 30 people during the span of 50 minutes, spread the virus?

The coronavirus is thought to spread mainly from person to person including via airborne virus and direct/indirect contact. Droplets that are produced when an infected person coughs or sneezes may be inhaled into the mouth or nose of people who are nearby or possibly be inhaled into their lungs.

Droplet size could be varied and the droplet can be shrunken in dry condition. Larger droplets can be settled on the surface of objects near the infected person while smaller droplets can become aerosols and be suspended in the air for a longer time. They may not be settled in 50 minutes. These small droplets containing the virus are bioaerosols.

Moreover, the ventilation system supplies fresh air in the room. But the air movement can spread small droplets further. In some cases, droplets can be distributed to other rooms through the ducts.

How does the research you’ve done personally relate to these things? Have you researched other similar things before that behave like COVID-19?

My research interest includes bioaerosols. Bioaerosols are aerosol particles of biological origins, bacteria, viruses, fungi, fungal spores, pollen, fragments of biofilm, etc. Since bioaerosols can be suspended in the air for a long period, they are ubiquitous in indoor and outdoor air. Inhaled by a human, they would be deposited in the respiratory tract, and potentially cause irritation, allergies, contagious infectious disease, acute toxic effects, cancer, and even death if the concentrations of bioaerosols are high.

For example, legionellosis, influenza, measles and tuberculosis are often spread by aerosols especially in poorly ventilated environments. Some occupational places such as composting sites, wastewater treatment plants, food industries, livestock farms and health-care centers have a high concentration of bioaerosols.

At agricultural workplaces, high concentrations of bacteria and fungi have caused infections and allergies, even death to farmers. Moreover, people working in health-care facilities are at higher risk of infections. I am currently developing the samplers to collect bioaerosols and the rapid analysis method for collected bioaerosols.

What factors would put students and professors more at risk when it comes to being in that enclosed space?

In a poorly ventilated environment, droplets from the people can be accumulated in the space. Opening the window could be helpful to minimize the risk. Air-cleaning devices are also good to minimize the concentration of droplets. A sneeze or a cough can produce a wide size range of droplets. Big droplets of a few micrometers can travel less than six feet. But some small droplets travel longer. After drying, a single virus may suspend in the air for a long time and travel longer.

Wearing a mask, having filter, can protect people who are infected and not infected. The mask can prevent both the generation and inhalation of infectious droplets. Masks can capture the droplets from the mouth and nose. Some small droplets can penetrate the mask and be inhaled by other people who are not wearing the mask. Masks can make fewer chances to touch the face directly with one’s hands. The cotton or surgical mask can not capture the droplet as much as the N95 mask, but something is better than nothing.

All droplets can be accumulated on the surface of the mask. Masks need to be washed frequently or wasted in the trash bin covered, not in an open bin, after use.

Even with everyone spread out, social distancing and wearing masks, is there still a risk for virus transmission?

That’s the best option. But I can say that risk is not zero.

With what you know about these things, do you feel safe entering a classroom space in the fall? Given that everyone does their part to appease to the Protect Purdue Plan.

No. As I mentioned, the risk is not zero. In the worst scenario, a single virus passing through the mask can be suspended in the air, reach another person’s breathing zone, pass through the mask, be inhaled, and develop the disease.

Do you trust that students will follow the guidelines set in place by the University?

No. We are human, like freedom and want to do what we want.

Do you think the University is doing enough in its plans to keep people safe in the fall?

Yes. I believe that they are doing their best.

What more could we as students do to keep each other safe and minimize risk and mitigate exposure?

We already know the answer. Social distancing and masks are the best options at this point. That’s the baseline. Wash hands. Measure body temperature. Stay home.

Are you going to do anything different, or extra in your own classrooms to help reduce the risk for yourself? Or will you try to limit the face-to-face classes as much as possible by having lectures online or anything?

It depends on the situation. I may use one of my special respirators utilizing a P95 filter or a HEPA filter. They are used in special occupational settings. If necessary, I will change the face-to-face classes to an online course.

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