Monitoring Viable Fungal and Bacterial Bioaerosol Concentrations to Identify Acceptable Levels for Common Indoor Environments

Abstract

Bioaerosol concentrations between 200 - 450 CFU/m3 have remained largely uncharacterized with respect to potential indoor air quality concerns. This research provides for further description of indoor bioaerosol concentrations and concludes that 3 0 0 CFU/m3 of non-toxigenic or non-pathogenic organisms should be typical for normal, non-immunocompromised environments. With the exception of Cladosporium, no organism should individually contribute more than 150 CFUfm3. Furthermore, it is concluded that > 300 CFU's/m3 and/or not meeting the above criteria should incite some additional level of investigation with respect to; the bias of prominent outdoor bioaerosol(s), adequate filtration, indoor humidity and microhumidity environments, and/or potential indigenous contamination source(s). The author cautions that the >300 CFU/m3 threshold is not intended to represent any threshold having medical or health significance and/or necessarily representative of an unacceptable indoor environment. The >300 CFU/m3 is intended to be a "reactionary threshold" to incite further investigation as to the cause(s) of what is perceived to be an above average viable concentration for indoor bioaerosols. The author further concludes that outdoor sampling should only be utilized in the relative comparisons to individual indoor components and that indoor/outdoor ratios involving total CFU/m3 concentrations should not be utilized as a specific mechanism to evaluate acceptable indoor bioaerosol concentrations.