A Survey of Four Fluid Milk Processing Plants for Airborne Contamination Using Various Sampling Methods

Air in four commercial fluid milk plants was sampled for microbiological and nonmicrobiological particles over a 4-month period. An Andersen two-stage and Ross-Microban sieve samplers, a Biotest RCS sampler, and a Met-one laser particle counter were used to sample air. Air was sampled two to three times per day in raw milk storage, processing, and filling areas. Viable particle counts per 100 L air obtained with the Andersen sampler were 2.03 ± 0.41 (log10 Mean ± SD), 2.26 ± 0.57, and 2.41 ± 0.70 in raw milk storage, processing, and filling areas, respectively. These levels were significantly (p<0.05) greater than those obtained using the RCS and Ross-Microban samplers. Overall correlations of the Ross-Microban and RCS samplers with the Andersen sampler were r2 = 0.71 and 0.62, respectively. Correlations between Andersen sampler results and number of total particles greater than 0.5 μm were r2 = 0.36 in raw milk storage, 0.15 in the processing area, and 0.18 in the filling area.

Measurement of Airborne Contamination in Two Commercial Ice Cream Plants

Air in two commercial ice cream plants was sampled for microbiological and nonmicrobiological particles over a 4-month period. Sampling methods utilized Andersen two-stage and Ross-Microban sieve samplers, a Biotest RCS sampler, and a Met-one laser particle counter. Air was sampled two to three times per day in pasteurized mix storage, processing, and filling areas. Viable particle counts per 100 L air obtained with the Andersen sampler were 2.26 ± 0.47 (log10 Mean ± S.D.), 2.05 ± 0.68 and 2.31 ± 0.46 in pasteurized mix storage, processing and filling areas, respectively. These levels were similar to those obtained using the RCS sampler, but they were significantly (p<0.05) greater than those obtained using the Ross-Microban sampler. Overall correlations of the RCS and Ross-Microban samplers with the Andersen sampler were r2 = 0.69 and 0.56, respectively. Correlations between Andersen sampler results and the concentration of total particles greater than 0.5 μm were r2 = 0.15 in pasteurized mix storage, 0.11 in the processing area, and 0.13 in the filling area.

Concentration of respirable dust and bioaerosols and identification of certain microbial types in a hog-growing facility

In order to assess the effects of ventilation rate, temperature, relative humidity and source of air on bioaerosol levels and dust with particle size < 10 μm, a total of 120 pigs housed in 12 pens in two separate rooms were used. Pigs averaged 30 kg initially and the trials were discontinued when 20% of the pigs were marketed. A six-stage Andersen sampler and a light scattering particle counter were used to determine bioaerosols and respirable dust (0.1–10 μm), respectively. Total bioaerosols were assessed using Trypticase Soy Agar. Potato Dextrose Agar was used for fungal aeorsols and Baird-Parker Agar used for isolation of Staphylococcus aureus. Moulds amounted to less than 1% of total microorganisms. Gram positive bacteria made up 72% of the bacterial isolates. Respirable dust was not correlated with respirable bioaerosols. Ventilation rate (2, 5 or 8 changes h−1) did not affect bioaerosol level or respirable dust. Total bioaerosols were significantly reduced (P < 0.05) in higher temperatures only. Relative humidity did not influence total bioaerosols but in one series respirable bioaerosols were significantly (R = 0.53) (P < 0.05) correlated with RH. Total bioaerosols were not different in outside air or attic air. Key words: Dust, bioaerosols, pigs, ventilation

Presence of Viable Mould Propagules in the Indoor Air of Houses

The aim of the first port of this study was to select the optimal technique for the enumeration and identification of viable mould propagules in the indoor air of houses. A comparison was made between the results obtained with six commercially available air sampling devices in combination with four culture media. The optimal technique was defined as the technique with the best precision and the highest yield. The coefficients of variation were high (generally > 20%) for all combinations. Statistical analysis showed that the Slit sampler and the N6-Andersen sampler in combination with DG18 and MEA gave the best precision and the highest yield in terms of CFU/m3 and number of species isolated. In the second part of this study the presence of viable mould propagules in the indoor air of 46 houses in relation to the dampness of these houses was investigated, using the N6-Andersen sampler in combination with DG18. To assess the variability in time, the measurements were repeated after five weeks. Overall, between the two periods no difference was found between the average number of CFU/m3 in the investigated homes. However, the variation between homes was much smaller than the variation within homes. The mean number of CFU/m3 was somewhat higher in “damp” houses than in “dry” houses. However, this difference was not significant. Furthermore, there were no demonstrable differences in the presence of specific mould species in “damp” and “dry” houses.