Personal air samplers for measuring occupational exposures to biological hazards

Microbiological air samplers, designed to be worn as personal samplers, were evaluated for studying occupational exposures to aerosols of infectious and allergenic materials. Gelatin filter media, an impinger sampler, and spiral and cascade impactors were tested for collection efficiency for small (less than or equal to 2 microns) latex spheres and for recovery of bacterial aerosols. Only 20% of an aerosol of 0.8 micron latex particles passed through the impinger uncollected, while recovery of bacteria equalled or exceeded collection in an all-glass impinger. Gelatin filters matched the collection efficiency of membrane filters, but were unsatisfactory for the isolation of bacteria sensitive to dehydration. The spiral sampler and the cascade impactor provide information on the size distribution of collected particles, although, at present, collection efficiencies for very small particles are too low for rigorously quantitative studies. Methods of collection, and sampling strategies for biological aerosols are similar to those used for measuring exposures of workers to chemical and mineral aerosols; however, preparation of samples and identification of isolates may have to be referred to experts in the fields of bacteriology, virology, and mycology.