Research Questions for Aerosol Scientists Addressing COVID-19 and the Workplace

August 13, 2020 by William G. Lindsley, PhD; Francoise M. Blachere, MSc; Nancy C. Burton, PhD, MPH, CIH; Brian Christensen, MPH; Cherie F. Estill, PhD; Edward M. Fisher, MS; Stephen B. Martin, PhD, PE; Kenneth R. Mead, PhD, PE; John D. Noti, PhD; Melissa Seaton, MS, CIH

The Coronavirus Disease 2019 (COVID-19) pandemic has raised many questions about the transmission of the virus that causes COVID-19, SARS-CoV-2, including the possibility of aerosol transmission. In the workplace, workers may encounter asymptomatic, pre-symptomatic, and symptomatic individuals who are infected with SARS-CoV-2 and may expel airborne particles containing the virus. Aerosol scientists bring a unique understanding of airborne particle behavior to infectious disease transmission studies. A recent commentary in Aerosol Science & Technology, “COVID-19 and the Workplace: Research Questions for the Aerosol Science Community,” presents some of the questions surrounding droplets and aerosols containing SARS-CoV-2 and provides suggestions for future research topics. Selected excerpts of the commentary are presented below. Please see the commentary for the full discussion.

How much SARS-CoV-2 aerosol is generated by coughing, sneezing, talking, singing, and breathing, and what are the implications for transmission?

A few studies have examined aerosols containing SARS-CoV-2. However, many questions have been raised about the possible transmission of SARS-CoV-2 by aerosol particles:

How much airborne virus is expelled by people?

What is the particle size distribution?

How do speaking, coughing, and breathing affect the emission rate?

Is the airborne virus infectious?

Research to address these questions will help to better understand the roles of droplet and aerosol transmission of SARS-CoV-2 and inform public health recommendations.

Are potentially infectious aerosols produced by toilets containing human waste with SARS-CoV-2?

Numerous research studies have shown that the flushing of toilets can generate aerosols that could lead to the transmission of pathogens. However, in the case of SARS-CoV-2, the potential for transmission through this route is unclear. More work is needed to better understand the possible production of SARS-CoV-2 aerosols by toilet flushing, the size distribution of the aerosol, the infectivity of the virus in the aerosol, and the risk that exposure to these aerosols may pose to healthcare workers and others.

Which engineering control methods are most effective to prevent SARS-CoV-2 exposure through droplet, fomite and short-range aerosol routes?

Studies of the effectiveness of engineering controls, such as intubation boxes and local exhaust source controls are limited, and minimal guidance is available on design dimensions, deployment requirements, and on the expected performance and limitations of these systems. Additionally, little is known about the efficacy of ultraviolet germicidal irradiation (UVGI) against SARS-CoV-2, including the dose of UVGI required to inactivate the virus and the effects of temperature, humidity and the presence of other organic material on virus susceptibility to UVGI. Transparent barriers between workers and customers are being widely deployed to reduce the risk of transmission of SARS-CoV-2, but research is needed on the degree of protection provided by these barriers, and especially on the effects of particle size on exposure reduction.

Do ventilation systems contribute to the dissemination and subsequent exposure to aerosols containing SARS-CoV-2?

SARS-CoV-2 RNA has been found in air samples within patient rooms and on HVAC supply and exhaust grills in restaurants, patient rooms, and patient restrooms (Ding et al. 2020; Liu et al. 2020; Ong et al. 2020). It is not clear if low concentrations of viable virus could accumulate in certain locations in an HVAC system. The lack of information on this topic has had both economic and public health planning consequences on the national and international return-to-work and school implementation strategy. Answering this question will require reliable sampling methods for both air and surface sampling, including measurements of culturable virus.

How contaminated are N95 filtering facepiece respirators (FFRs) that are exposed to SARS-CoV-2 bioaerosols?

With limited FFR availability, healthcare facilities have employed extended use, limited reuse, and decontamination to optimize supplies (CDC 2020b). Research on the level of bioaerosol contamination of used FFRs will provide empirical data to prioritize supply optimization strategies, determine the appropriate level of respiratory protection, and establish decontamination efficiency requirements for a standard method.

Does transmission of SARS-CoV-2 occur by aerosol inoculation of the ocular surface?

Transmission of airborne SARS-CoV-2 through the eye is highly plausible (Napoli et al. 2020), but the importance and mechanisms of transmission through the eye remain unclear. Additional research looking at whether transmission of SARS-CoV-2 can occur by aerosol exposure to the surface of the eye is greatly needed. Such studies would contribute to eye protection recommendations and use in occupational settings.

Conclusions

Protecting workers and others from COVID-19 presents substantial challenges, in part because we have more to learn about how this disease is spread and how best to prevent it. We hope this blog (and the published commentary) will inspire fresh ideas and new projects to study these and related questions. Data to help address these questions will be critical during the current pandemic; such data may also be applicable to other infectious agents we are already facing and new agents we will inevitably face in the future.

William G. Lindsley, PhD, NIOSH Health Effects Laboratory Division

Francoise M. Blachere, MSc, NIOSH Health Effects Laboratory Division

Nancy C. Burton, PhD, MPH, CIH, NIOSH Division of Field Studies & Engineering

Brian Christensen, MPH, Amentum Services

Cherie F. Estill, PhD, NIOSH Division of Field Studies & Engineering

Edward M. Fisher, MS, NIOSH National Personal Protective Technology Laboratory

Stephen B. Martin, PhD, PE, NIOSH Respiratory Health Division

Kenneth R. Mead, PhD, PE, NIOSH Division of Field Studies & Engineering

John D. Noti, PhD, NIOSH Health Effects Laboratory Division

Melissa Seaton, MS, CIH, NIOSH Division of Science Integration

The Centers for Disease Control and Prevention is addressing questions related to the Coronavirus Disease 2019 through CDC-INFO and on their webpage. Please visit https://www.cdc.gov/coronavirus/2019-ncov/index.html. You can find the most up-to-date information on the outbreak and get the latest answers to frequently asked questions. If you have specific inquiries, please contact CDC-INFO at https://wwwn.cdc.gov/dcs/contactus/form or by calling 800-232-4636.

References

CDC. (2020a). How COVID-19 Spreads. Retrieved May 18, 2020, 2020, from https://www.cdc.gov/coronavirus/2019-ncov/prepare/transmission.html.

CDC. (2020b). Strategies for Optimizing the Supply of N95 Respirators. Retrieved May 11, 2020, 2020, from https://www.cdc.gov/coronavirus/2019-ncov/hcp/respirators-strategy/index.html.

Ding, Z., Qian, H., Xu, B., Huang, Y., Miao, T., Yen, H.-L., Xiao, S., Cui, L., Wu, X., Shao, W., Song, Y., Sha, L., Zhou, L., Xu, Y., Zhu, B. , and Li, Y. (2020). Toilets dominate environmental detection of SARS-CoV-2 virus in a hospital, MedRxiv (preprint) doi: 10.1101/2020.04.03.20052175.

Liu, Y., Ning, Z., Chen, Y., Guo, M., Liu, Y., Gali, N. K., Sun, L., Duan, Y., Cai, J., Westerdahl, D., Liu, X., Xu, K., Ho, K. F., Kan, H., Fu, Q. , and Lan, K. (2020). Aerodynamic analysis of SARS-CoV-2 in two Wuhan hospitals, Nature [published online ahead of print, 2020 Apr 27, doi: 10.1038/s41586-020-2271-3].

Napoli, P. E., Nioi, M., d’Aloja, E. , and Fossarello, M. (2020). The Ocular Surface and the Coronavirus Disease 2019: Does a Dual ‘Ocular Route’ Exist?, J. Clin. Med. 9.

Ong, S. W. X., Tan, Y. K., Chia, P. Y., Lee, T. H., Ng, O. T., Wong, M. S. Y. , and Marimuthu, K. (2020). Air, Surface Environmental, and Personal Protective Equipment Contamination by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) From a Symptomatic Patient, JAMA:10.1001/jama.2020.3227.

WHO. (2020). Q&A on coronaviruses (COVID-19). Retrieved May 18, 2020, 2020, from https://www.who.int/emergencies/diseases/novel-coronavirus-2019/question-and-answers-hub/q-a-detail/q-a-coronaviruses.