Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, K01-OH-008029, 2008 Nov; :1-100
Exposure to airborne biological agents, especially to pathogenic or allergenic microorganisms, is known to cause a wide range of respiratory and other health disorders in occupational and general populations. Exposure to airborne microorganisms is commonly assessed by using air samplers designed for monitoring viable microbial agents. Recently, a number of new or modified portable samplers for viable microbial aerosols have become available, but their performance and accuracy was largely unknown. Accuracy of the data obtained using any bioaerosol sampler is of critical importance, because improper measurements may disguise actual differences in worker exposures and generally misguide the investigation. Thus, the main goal of this research was to analyze the physical and biological performances of newly available or modernized portable bioaerosol samplers, such as the MAS- 100 (EMD Chemicals, Inc., Gibbstown, NJ), Microflow (Aquaria srl, Lacchiarella, Italy), BioCulture (A.P. Buck Inc., Orlando, FL), SMA MicroPortable (Veltek Associates, Inc, Phoenixville, PA), SAS Super 180 (Bioscience International, Inc., Rockville, MD), Millipore Air Tester (Millipore Corp., Billerica, MA) and RCS High Flow (Biotest Diagnostics Corp., Denville, NJ). Their performance was analyzed theoretically and compared in laboratory and field experiments against a traditional reference bioaerosol sampler (Andersen-equivalent impactor) and an inhalation-based sampler (Button Aerosol Sampler with gelatin filter) for viable bioaerosols. In addition, portable samplers' physical collection efficiency was compared against the conventions for total inhalable particles and particle deposition in the lung. The theoretical and experimental analysis of the portable samplers' physical collection efficiency indicated that cut-off sizes, or d5o, of the sampler is > 1um, which would result in a substantial under-sampling of single bacterial cells with diameter 0.5-1.0 um. It was found that the collection efficiency curves of all the samplers did not follow the inhalation exposure convention for bacterial particles, but some samplers did follow the convention for larger fungal particles. Some of the samplers' collection efficiency curves followed conventions for particle deposition in the lung. Laboratory investigation showed that the samplers' overall performance when sampling bacteria and fungi depended on sampler model and microorganism type collected, with their overall performance largely determined by the physical collection efficiency. Overall, the portable impactors underperformed compared to the traditional Andersen-equivalent impactor. Field experiments indoors and outdoors showed that relative performance of all the portable samplers was statistically different (lower) compared to the Andersen-equivalent impactor, except the RCS High Flow and the MAS-100 impactors. The recovery of microorganisms sampled on a gelatin filter was on average 50% of that recovered by the Andersen-equivalent impactor. Field investigation also revealed that the sampling time should be limited to a few minutes; otherwise the collected microorganisms may be inactivated due to desiccation. The use of portable impactors is advantageous due to their high sampling flow rate, light weight and portability. However, this study showed that some of them underperform compared to a traditional Andersen-equivalent impactor and that the occupational professionals should be aware of the limitations of the portable samplers. The results from this study will help occupational professionals to select an efficient tool for environmental investigation projects; the results of the study and its recommendation will also be useful when designing new bioaerosol samplers that allow improved assessment of microbial exposure.
Fungi; Bacteria; Microbiology; Microorganisms; Air-samplers; Air-sampling; Air-quality-monitoring; Air-quality-measurement; Air-sampling-equipment; Air-sampling-techniques; Airborne-particles; Air-monitoring; Air-contamination; Analytical-processes; Analytical-models; Sampling-equipment; Sampling-methods; Sampling; Samplers