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Aerial levels of bacterial-colony-forming particles (BCFP) in lung-depositable size ranges were determined using an eight-stage Andersen viable sampler with tryptose agar. Aerial levels of BCFP~< 4.7/am and ~<3.3/am in aerodynamic diameter were significantly and positively correlated with total-aerial-BCFP level in swinehouse air. On average, 31% of aerial BCFP were ~<4.7 /am and 15% were ~<3.3 /am in four University enclosed swine houses (n = 192); 30% and 22%, respectively, in a University modified-open-front house (n = 44) and 28% and 11%, respectively, in 12 houses at five commercial operations (n = 24). Aerial-dust level was determined using a Staplex highvolume sampler. Aerial-BCFP and-dust levels were significantly and positively correlated. There tended to be fewer aerial BCFP per unit of aerial dust in the modified-open-front house than in the enclosed houses at the University.Ten swine houses at commercial operations and four at the University were studied a total of 16 times to determine concentrations and sizes of aerial bacterial particles which formed colonies on tryptose (general medium), Chapman-Stone (special medium for staphylococci), KF Streptococcus (fecal streptococci) and Mac-Conkey (coliforms) agars, respectively. Ratio of bacterial-colony-forming-particle (BCFP) count on Chapman-Stone agar to that on tryptose averaged .36, that on KF Streptococcus to that on tryptose averaged .13 and that on Mac-Conkey to that on tryptose averaged less than .01. Twenty-one percent of the staphylococcal BCFP and streptococcal BCFP, respectively, and 9% of the coliform BCFP, were lung-depositable (~<4.7 /am in diameter). Nitrogen content of aerial dust in a swine-finishing house, in which a 13% crude-protein (CP) diet was fed, averaged 4.6%, or (4.6 x 6.25) = 28.7% CP (n = 17). Settled dust in a farrowing house, in which a 12% CP diet was used, averaged 23.3% CP (n = 6), whereas that in a room in which diets having 12 to 16% CP were prepared averaged 13.0% CP (n = 4). It was concluded that much of the dust in swine-house air was feed dust. (

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Female F344 rats were fed diets containing 0.02%, 0.2%, or 2.0% white mineral oil for 90 days. There were no gross or microscopic differences in target organs at the 0.02% level. In the higher-dose groups, relative liver and mesenteric lymph node (MLN) weights were increased, and MLN inflammation was observed. At the 2% level, there was very limited evidence of microgranuloma formation in the liver but at a lower incidence and at lesser severity than has been reported in studies of C₂₂-C₂₅ oils. Analysis of liver extracts from treated rats revealed that C₁₅-C₂₀ constituents were underrepresented by comparison to their corresponding concentrations in the test oil. These results provide evidence that although hydrocarbons with carbon numbers < C₂₀ are absorbed, they are not preferentially retained and do not contribute to inflammatory processes in liver.

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