An analytical method for the measurement of nonviable bioaerosols

Exposures from indoor environments are a major issue for evaluating total l ong-term personal exposures to the fine fraction (<2.5 mum in aerodynamic d iameter) of particulate matter (PM). It is widely accepted in the indoor ai r quality (IAQ) research community that biocontamination is one of the impo rtant indoor air pollutants. Major indoor air biocontaminants include mold, bacteria, dust mites, and other antigens. Once the biocontaminants or thei r metabolites become airborne, IAQ could be significantly deteriorated. The airborne biocontaminants or their metabolites can induce irritational, all ergic, infectious, and chemical responses in exposed individuals. Biocontaminants, such as some mold spores or pollen grains, because of thei r size and mass, settle rapidly within the indoor environment. Over time th ey may become nonviable and fragmented by the process of desiccation. Desic cated nonviable fragments of organisms are common and can be toxic or aller genic, depending upon the specific organism or organism component. Once the se smaller and lighter fragments of biological PM become suspended in air, they have a greater tendency to stay suspended. Although some bioaerosols h ave been identified, few have been quantitatively studied for their prevale nce within the total indoor PM with time, or for their affinity to penetrat e indoors, This paper describes a preliminary research effort to develop a methodology for the measurement of nonviable biologically based PM, analyzing for mold and ragweed antigens and endotoxins. The research objectives include the d evelopment of a set of analytical methods and the comparison of impactor me dia and sample size, and the quantification of the relationship between out door and indoor levels of bioaerosols. Indoor and outdoor air samples were passed through an Andersen nonviable cascade impactor in which particles fr om 0.2 to 9.0 mum were collected and analyzed. The presence of mold, ragwee d, and endotoxin was found in all eight size ranges. The presence of respir able particles of mold and pollen found in the fine particle size range fro m 0.2 to 5.25 mum is evidence of fragmentation of larger source particles t hat are known allergens.