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.