Evaluation of airborne dust and endotoxin in corn storage and processing facilities in Colorado

The main objectives of this research were to determine what aerosols were present by taking total dust (TD) samples and thoracic particulate mass samples (TPM) on farms and in grain elevators. Cascade impactors were used to characterize size distributions of dust and endotoxins at each site. Total dust concentrations on farms had a geometric mean 3.4 mg/m3 and 3.3 mg/m3 in elevators. The geometric mean (GM) concentrations for the TPM were 2.4 mg/m3 on farms and 1.0 mg/m3 in elevators. Endotoxin concentrations as geometric means were alarming at 3175 EU/m3 total dust and 983 EU/m3 by TPM on farms. In elevators, the GM concentrations for endotoxins were 2534 EU/m3 total dust, and 526 EU/m3 by TPM. The mass median aerodynamic diameter (MMAD) for endotoxins on farms was 8.0 microm and 6.5 microm in elevators. The paired t-test was applied to the log ratios of endotoxin concentrations (EU/m3) and dust concentrations (mg/m3), for paired samples of the TD and TPM. A higher content of endotoxins was associated with TPM for farms but not elevators. It was concluded that although the TPM fraction (dust) may represent a small part of the total mass, the aerosol size is optimum for deposition in the lung's tubular airways, and might cause airway inflammation due to the endotoxins. The TPM fraction of corn dust represents the best measure of exposure with regard to the potential development of long-term airways inflammation, and the potential of chronic obstructive pulmonary disease among chronically exposed workers. All endotoxin concentrations were well above recommended exposure levels of several researchers familiar with endotoxin health effects.