American Industrial Hygiene Conference and Exposition, May 13-16, 2006, Chicago, Illinois. Fairfax, VA: American Industrial Hygiene Association, 2006 May; :55
We examined the effects of storage time, temperature, and humidity on levels of culturable fungi from office building floor dust samples. Four bulk dusts were pooled, homogenized with a 360-degree rotation shaker for two hours, and made into 152 aliquots. For a total of 144 aliquots, four were assigned into 36 combinations of time (two, four, six, and eight weeks; six months; and one year), temperature (room temperature, 4 degrees C refrigerator, and -80 degrees C freezer), and humidity conditions (with and without desiccant). We additionally analyzed eight aliquots two days after sampling to obtain baseline data. The samples were cultured with MEA, DG-18, and cellulose agar at room temperature for seven to 10 days. A total of 44 species were identified with Penicillium aurantiogriseum, Epicoccum nigrum, Cladosporium cladosporioides, yeasts, and Alternaria alternata recovered from at least 70% of the aliquots. Total fungi from all aliquots ranged from 3,500 to 165,400 colony-forming units per gram dust (cfu/g), showing that effects of storage conditions were within two orders of magnitude. We analyzed cfu/g with analysis of variance. Compared with baseline, Penicillium levels generally increased over time up to six months for all temperature conditions, and then dropped at one year. Cladosporium levels generally declined at all temperature and time conditions. Yeasts generally declined up to eight weeks; after that, levels differed by temperature conditions. We found interaction effects between time and temperature that differed by species. At the two-week-long storage, Cladosporium and yeast levels were closest to the baseline values for -80 degrees C storage, while for Penicillium, all three temperature conditions gave similar results. The presence of desiccant kept the levels of Cladosporium and Penicillium species closer to the baseline, but this effect was not found for other species. Our results imply a complicated relationship between storage conditions and levels of culturable fungal species.
American Industrial Hygiene Conference and Exposition, May 13-16, 2006, Chicago, Illinois