Overview and purpose

In April 2020, Yao Addor (PhD student in the Environmental and Industrial Hygiene program) and his advisor Dr. Tiina Reponen of the University of Cincinnati, responded promptly to a call for proposals launched by Droplet Measurement Technologies (DMT), LLC. (Longmont, Colorado) for support of research focusing on the current pollution levels around the world and how mandatory restrictions due to COVID-19 impact them. Our research proposal was selected by the Droplet Science department, granting us two of their cutting-edge instruments, the PAX (Photoacoustic Extinctiometer) and the WIBS-5/NEO (Wideband Integrated Bioaerosol Sensor - version 5 / New Electronics Option) on loan, free of charge. We also used other devices such as Button Aerosol Samplers (SKC Inc., Eighty Four, PA), Allergenco-D Spore Traps (Eurofins EMLab P&K, Marlton, NJ), and Two-stage Viable Andersen Cascade Impactors (Thermo Scientific, Franklin, MA) available in our lab.

The purpose of this project was to assess the indoor and outdoor bioaerosol- and black carbon-related contaminant levels during and after the COVID-19 related shutdown in Cincinnati, Ohio. We conducted continuous bioaerosol and black carbon measurements in a residential apartment in Cincinnati, Ohio, from July to September 2020. The date of August 31, 2020 was chosen as the cut-off for during and after shutdown since schools reopened at the beginning of September in the school district where the measurements were taken.

Material description

Figure 1: Instruments and devices used for air monitoring and sampling.

The WIBS-5/NEO is used worldwide for real-time, single-particle measurement of atmospheric bacteria, molds, pollen, and their fluorescent properties. It detects and classifies particles as biological or non-biological origin to identify bioaerosols that can be detrimental to human health. It measures fluorescence to detect the presence of biological particles as well as detailed data on the size, relative measure of shape, and fluorescent intensity at different wavelengths. The biological particle can then be classified into pollen, bacteria, and fungi categories (Source: https://www.dropletmeasurement.com/).

The PAX is a sensitive, high-resolution, fast-response instrument for measuring aerosol optical properties relevant to climate change. It measures light absorption and scattering and derives effective black carbon mass concentration (Source: https://www.dropletmeasurement.com/).

Air sampling and monitoring

In this project, we measured indoor and outdoor:

• Bioaerosol concentrations, including levels of airborne bacteria, fungi, pollen, and other unspecified airborne biological agents using the WIBS-5/NEO, Button aerosol samplers, Allergenco-D spore traps, and Two-stage Andersen cascade impactors.
• Effective black carbon concentration as a surrogate for traffic-related air pollution.

Figure 2: Setup of the instruments and devices indoors and outdoors

Preliminary data

Figure 3: Indoor and outdoor daily averages of total and fluorescent particles as measured with WIBS-5/NEO 

Figure 3 shows the graphs of daily average concentrations for the total and fluorescent particles, indoors and outdoors, as measured with the WIBS-5/NEO. The fluorescent particle levels followed a similar pattern as the total particle levels.

Preliminary statistical data analysis indicates that the total and fluorescent particle levels were significantly higher indoors compared to outdoors. The mean particle levels appeared to be higher after the shutdown compared to during the shutdown.

Summary

We monitored indoor and outdoor air during and after the shutdown period due to the COVID-19 in a residential apartment using traditional and direct-reading aerosol instruments. The results presented above are preliminary and exploratory. Further analyses will be performed for the biological particles of different fluorescent types.