Evaluating indoor air quality: test standards for bioaerosols

Introduction: No standard method exists for enumerating fungal aerosols, impeding the development of reliable exposure-response data. A field comparison of four bioaerosol samplers, the Reuter Centrifugal Sampler (RCS), the Andersen N6 Single Stage (N6), the Surface Air System Super 90, and the Air-o-Cell sampler (AOC), was conducted in a variety of public buildings for the measurement of fungal aerosols to compare sampling performance efficiencies and to collect baseline data for a pool of buildings Methods: Sampling was conducted at 75 sites in public buildings from June-October 2001 in the greater Vancouver area, British Columbia. Four locations were sampled at each site (1 common area, 2 offices, and 1 outdoor sample). Each location was sampled in parallel, collecting approximately 150 litres of air for each sample. Malt extract agar was used for all growth media. Sequential duplicates were taken at each location. Simple linear regressions were calculated for each method pair to develop betweensampler calibration equations. Results: Data from approximately 592 samples (60 different buildings) were available for analysis from each instrument. Differences were found between samplers for overall yield, detection limits, and reproducibility. The highest spore concentrations were returned by the non-viable method, the AOC. The N6 and RCS were comparable in colony concentrations, but the N6 was more efficient at capturing small particulate such as Penicillium and Aspergillus spores. The SAS-90 returned concentrations that were significantly lower than all other samplers. The surrogate chemicals, ergosterol and (1→3) β D glucan were below the limit of detection of the method for these samples. Conclusions: Concentration data is dependent on the sampling methodology utilized for assessment and should be considered before conducting investigations of bioaerosols in different environments. Exposure guidelines cannot be created until a standard methodology is available. All of the bioaerosol sampling devices tested had unique characteristics which could be seen as beneficial or detrimental depending on the sampling environment and the conclusions drawn from the sample data.