June 1, 2023

Bioaerosol Sampling in a Healthcare Facility

By Ed Rutkowski

In any workplace, industrial hygiene sampling needs to proceed according to a well-formulated plan that minimizes disruptions to work tasks. This requirement is difficult to meet in healthcare facilities, and especially so when the agent of interest is a bioaerosol. Last week at AIHce EXP 2023, three experienced professionals described how they overcome challenges of sampling in the healthcare environment and the singular difficulties presented by bioaerosols.

As with all sampling, a plan is key to success. “You just don’t go and pull samples because you can,” said Cynthia Ellwood, an industrial hygiene consultant. A variety of bioaerosols are of potential interest; the fungi aspergillus and mucorales, the tuberculosis bacterium, and the measles and varicella-zoster viruses are all well-established potential airborne hazards in healthcare facilities. The COVID-19 pandemic has also brought wide recognition of the potential for SARS-CoV-2 to spread among hospital patients and staff. Several other microorganisms are occasionally reported in healthcare facilities.

Ellwood’s co-presenter Suzanne Blevins, the director of an industrial hygiene laboratory, encouraged OEHS professionals to work with their labs to identify the right method for the agent of interest. “Your laboratory is your best partner to enhance the protocol” to find specific bioaerosols, Blevins said.

When developing a sampling strategy, Ellwood documents where and when the sampling will be conducted, its duration, the number of samples to be taken, and the sampling method to be used, including its cost, detection limit, and any potential disruption it might cause to patient services. One of the most important tasks during this process, she said, is to identify what qualifies as an acceptable and unacceptable result, and what actions to take in either case. For acceptable results, OEHS professionals need to decide who to share the information with, where it will be stored, and who will have access to the data. Unacceptable results require communication, documentation, and follow-up that OEHS professionals should plan before the sampling is conducted.

The remainder of the session focused on a case study involving patients who have undergone bone-marrow transplants (BMT). Laura Riley, an industrial hygienist with a hospital in Georgia that has a large BMT patient population, explained that she performs sampling quarterly with the goal of sampling every patient room once per year. The sampling is conducted in unoccupied rooms at least six hours after they’ve been cleaned, Riley said. Because bone-marrow patients are a sensitive population, the ventilation is designed to meet stringent requirements, and the rooms are presumed to be so clean that Riley treats a sampling result of a mere 2 colony-forming units per cubic meter of air (CFU/m3) as a trigger for further investigation. In one instance, the positive pressure in the rooms was so strong that it was pulling contaminants out of the wall cavities, she said.

On another occasion, sampling data informed a change in process for conducting routine maintenance on the air-handling unit (AHU) serving the BMT rooms. To minimize disruptions to patients, maintenance staff typically changed the filters on the AHU in the middle of the night, a task that required the AHU to be shut down. Riley’s surveillance revealed that restarting the AHU was associated with huge, brief spikes in particulate in patient rooms at a time when the patients were sleeping—and therefore unmasked. The new procedure, which occurs during the day, involves coordination between the maintenance and nursing staff. As Riley explained, maintenance calls to inform staff that the AHU will soon be turned off, which triggers nurses to put the patients in N95 respirators. Once the patients are protected, nursing staff call maintenance to say that it’s okay to restart the AHU. The patients stay masked for about an hour after restart—the length of time needed for particulate to return to baseline levels, as Riley’s data has shown.

The lesson, Riley said, is that “you really have to control for your environment.”

Ed Rutkowski is editor in chief of The Synergist.

For Further Reading

The Synergist: “From Hardhats to Hair Covers: IEQ Investigations in Healthcare Facilities” (June/July 2015).