How reliable are your one-minute Andersen sample data?
Heinsohn, P.
Environmental Microbiology: Bioaerosols and Biosafety
Heinsohn, P."How reliable are your one-minute Andersen sample data?", Environmental Microbiology: Bioaerosols and Biosafety.
| Abstract: |
| Industrial hygienists can choose a sampling time in which a minimum air volume can be collected to meet the published limit of quantitation (LOQ) of a NIOSH-validated sampling and analytical method for nonbiological aerosols. Inherent in that choice is an assumption that the coefficient of variation is constant over the entire range of airborne contaminants. However, industrial hygienists must choose a sampling time for a "viable" sampler such as the Andersen N6 to sample for airborne culturable fungi in the absence of validated methods. The AIHA Field Guide for the Determination of Biological Contaminants in Environmental Samples describes how to calculate the LOQ of such samples based on a coefficient of variation of 0.2 using a desired sampling time and states that the maximum sampling time is five minutes. However, the common industrial hygiene practice is one minute. The purpose of this study was to determine if one-minute sampling times met the LOQ. One- and two-minute samples using the Andersen N6 were taken simultaneously on three different media in the morning and afternoon in single-family residences. Total colony-forming units were analyzed using Poisson regression statistics. There is a significant effect of time demonstrated among the 227 paired data points. A significantly higher proportion of two-minute samples meets the LOQ overall (p = 0.0001). This significance is maintained among morning samples (p = 0.0038) and afternoon samples (p = 0.001). There is also statistical significance for samples collected on dichloran glycol media (p = 0.0031) and malt extract agar (p = 0.008) but not on cellulose Czapek's agar (p = 0.057). Our work suggests that one-minute sampling times result in less reliable data than two-minute samples and are thus discouraged in residential settings.
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