Size characterization and composition of inhalable bioaerosols at Colorado dairies

![CDATA[Background and Objectives: Dairy farmers exposed to bioaerosols are at an increased risk for acute and chronic lung disease. Previous studies have suggested that such bioaerosols contain particle sizes that extend well into the inhalable size fraction. The aim of this study was to characterize the size and compositon of dairy bioaerosol using a high-volume impactor (ISEL v2) that is capable of sampling and size-fractionating dust up to100 μm in aerodynamic diamter. This work is novel because standard particle sizing equipment has an upper limit of 20 μm; very few instruments exist to size-segreate aerosols in the inhalable range (1-100 mm). Methods: The ISEL v2 collected bioaerosols inside three Colorado dairy parlors during a full work shift in four different seasons. At a flow rate of 1500 liters per minute, the impactor segregated airborne dust into size fractions of particle diameter (dp) >30, 10, and 3 μm, in addition to a final filter for dp<3 μm. We are currently completing analyses of fractionated samples for microbial and chemical content. Briefly, fractionated dust will be imaged and analyzed using a scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectrometry (EDS) detector. Additionally, each size fraction will be extracted and analyzed to determine airborne concentrations of endotoxin (PyroGene® assay), as well as to characterize microbial communities by Illumina Mi-Seq and chemical content by GC/MS/MS. Preliminary Results: Bioaerosols exhibited a bimodal size distribution with one mode under 3 μm and a second mode above 30 μm; the larger size mode persisted across different days and seasons at each dairy. Previous studies have typically reported unimodal distributions in agricultural aerosols. PyroGene® assay and GC/MS/MS analyses indicate that endotoxin content is size and dairyspecific, while differences in muramic acid are negligible. Preliminary results suggest variability within and between dairies that is most likely attributed to seasonal effects and parlor characteristics. We will present final results at the conference in addition to findings from SEM/EDS and Illumina Mi-Seq. Conclusions: This study is the first to characterize such a wide size range of agricultural aerosol. Our results indicate that particle deposition in the upper portion of the respiratory system may have important implications for inflammation and lung disease among workers in dairy environments.]]