Characterization of particulate matter in naturally and fan-ventilated swine barns

摘要

Airborne dust and bioaerosol levels from two growing-finishing swine barns (one naturally ventilated, NV, and one mechanically ventilated, MV,) were measured over a 5-month period during warm and mild weather conditions. Concentrations of inhalable and respirable dust masses were determined gravimetrically. Bioaerosol samples were collected on membrane filters and cultured on R2A agar; the resulting colony-forming units (CFU) were counted and identified. The two barns did not show any significant difference in airborne dust and bioaerosol levels. Mean concentrations of respirable and inhalable dust were 0.08 mg/m~3 (SD=0.05) and 1.10 mg/m~3 (SD=0.61), respectively, in the NV barn and 0.10 mg/m~3 (SD=0.05) and 1.03 mg/m~3 (SD=0.70), respectively, in the MV barn. These mean values were lower than either the established threshold limit values or the corresponding values reported in the literature. Inhalable dust was about 15 percent higher over the pens than over the alley, but no significant difference was found in the respirable dust fraction between the pens and the alley. The geometric mean diameters of particles for the NV and MV barns were 14.5 #mu#m (GSD = 2.4) and 13.3 #mu#m (GSD 2.3), respectively. Total CFU counts ranged from 5.0 X 10~2 to 9.4 X 10~4 per m~3 for the NV barn and from 1.6 X 10~3 to 1.4 X 10~5 per m~3 for the MV barn and consisted mostly of Gram-positive bacteria and molds. The mean concentrations of viable respirable particles were 6.9 X 10~3 per m~3 inside the NV barn and 1.2 X 10~4 per m~3 inside the MV barn. Measured values were within the range of previously reported CFU concentrations for swine finishing barns.