May 24, 2022

The Many Challenges of Bioaerosol Sampling

By Ed Rutkowski

NASHVILLE, Tennessee (May 24, 2022)—During the COVID-19 pandemic, OEHS professionals have been called on to conduct sampling designed to determine the presence and concentration of SARS-CoV-2. But, as bioaerosol scientist Quinn Aithinne demonstrated yesterday at AIHce EXP 2022, that seemingly simple charge is fraught with difficulty.

Speaking at the first of three technical sessions on the role of the industrial hygienist in a pandemic, Aithinne, of the Johns Hopkins University Applied Physics Laboratory, described sampling for bioaerosols as “probably one of the most inefficient processes in industrial hygiene.” The first challenge, Aithinne said, is that “anyone who is breathing is a potential source.” As a result, deciding where to collect a sample is highly uncertain, and sample sizes are typically low. Often, the analytical laboratory is unable to detect any virus in the sample. “Zeroes [that is, non-detects] are a huge issue” in bioaerosol sampling, Aithinne said, not least because of costs, which could be as much as $500 per sample.

OEHS professionals also need to consider the ultimate purpose of the sampling project. If a biological assay will be conducted, the virus must be alive, but sometimes the sampling method kills what it collects. A smattering of viral parts will work for analysis by polymerase chain reaction (PCR), which can verify the presence of virus in a sample but can’t say whether it’s infectious. And trying to determine whether the amount of virus exceeds what would be expected from background is impossible because no information on background levels exists. For these reasons, Aithinne said, “all your estimates are low-faith.”

The lack of data on background levels is just one of the important differences between sampling for bioaerosols and sampling for chemicals. With chemicals, background levels can be obtained from publications, Aithinne explained; such data doesn’t exist for bioaerosols because OEHS professionals are only tasked with sampling when an outbreak occurs. Also, chemical sampling data typically conforms to a log-normal distribution; in contrast, bioaerosol data conforms to the much more limiting Poisson distribution.

Even if OEHS professionals overcome these challenges, the lack of an enforceable OSHA standard for infectious diseases means that it’s difficult to know what to do with the information they’ve obtained. At the end of the day, Aithinne said, the only options are to conduct contact tracing and implement enhanced precautions.

As if these complications weren’t enough, the equipment used to conduct bioaerosol sampling is expensive and limited by design flaws, Aithinne said. The only reliable sampler for SARS-CoV-2 Aithinne is aware of costs $30,000 and is so bulky it is impossible to use in many circumstances. “That’s why we need industrial hygienists in research design,” Aithinne said.

Ed Rutkowski is editor in chief of The Synergist.

Related: Aithinne coauthored an article in the August 2021 Synergist on sampling for SARS-CoV-2.

View more Synergist coverage of the conference on the highlights page on AIHA’s website.