As part of a project to evaluate health hazards for workers in swine confinement buildings, the air in 21 different buildings was sampled with 37 mm cassette filters with and without cyclone preselectors and with cascade impactors. Filter results yielded a mean total aerosol of 6.3 mg/m3, a mean respirable aerosol of 0.5 mg/m3; the geometric mean diameter was 2.9 microns. Cascade impactor measurements revealed a mean total aerosol of 7.6 mg/m3, a respirable aerosol of 2.5 mg/m3 and a mass median diameter of 9.6 microns. The two major constituents in these aerosols were grain particles and dried fecal matter. The grain particles were larger than fecal particles and proportionately more abundant in finishing buildings where 50 kg X 100 kg animals are housed. Therefore the respirable fraction was less in finishing buildings than in farrowing and nursery buildings. Culturing of settled dusts yielded six different mold species, with the highest counts for Verticillium sp. (5 X 10(2) cfu/mg dry dust) grown at 37 degrees C. Thermophilic Actinomycetes and both gram negative and gram positive bacteria were isolated. Azocasein proteinase activity was found in most dust samples analyzed. This dust had a protein content of about 23% and a mean adsorbed ammonia content of 0.4%.

We report results from one study in the United States and another in Sweden that were designed to evaluate health hazards for workers in swine confinement buildings. The air in 21 buildings in Iowa was sampled with 37 mm cassette filters with and without cyclone preselectors and with cascade impactors [Donham and Gustafsson, 1982; Donham et al, 19841. Aerosolized dust was examined by light microscopy to determine the constituents and particle size [Lippman, 19831. Settled dust was analyzed for adsorbed ammonia [Conway, 19501, protein content [Conway, 19501, proteinase enzyme activity [Starkey, 19771, microbial content [Trehaft and Markus Jones, 19821, and endotoxin [Thedell et al, 19801. Results of gravimetric sampling on 37 mm filters revealed a mean total mass of 6.3 mg/m3 and a mean respirable mass of 0.5 mg/m3. Cascade impactor measurements revealed a mean total mass of 7 mg/m3, a respirable mass of 2.5 mg/m3 and a mass median diameter of 9.6 pm.Light microscopic analysis revealed that the main constituents of this dust included animal feed components (starch granules, grain meal, trichomes, and corn silk) and swine fecal material (bacteria, gut epithelium, and undigested feed). Other identified components of the dust included swine dander, mold pollen, insect parts, and mineral ash. The relative proportion of feed to fecal content of the dust increased in buildings where larger animals were housed. The microscopically measured median diameter of the particles was about 2.2 pm. Culturing of settled dust revealed a total viable count of 20 organismdmg dry dust. Gram-positive bacteria predominated the microbial flora, but Gram-negative bacteria and mold were also present. Six different mold species were isolated: the highest counts were Verticillium sp (5 X lo2 cfu/mg dry dust) grown at 37°C. Thermophilic Actinomycetes and Gram-negative and Gram-positive bacteria were also isolated. Azocasein proteinase activity was

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A multiplicity-dependent interference was observed in respiratory syncytial virus preparations (Randall strain) grown in HEp-2 cells, and the factor mediating this interference was characterized. Cloned virus did not demonstrate this multiplicity-dependent interference, but its replication was shown to be inhibited by the interfering factor by assays of reduction of infectious yield assay, the interferon factor was found to be particulate, to be inactivated by UV irradiation, and not to interfere with the replication of a heterologous virus, vesicular stomatitis virus. These characteristics are compatible with the physical properties and biological behavior of defective interfering particles. Defective interfering particles were generated by four undiluted passages of cloned virus but were not apparent after eight passages at a multiplicity of infection of 0.1.