Measurement of airborne fungal spore dispersal from three types of flooring materials

Research was conducted in an experimental room to measure the effect of human activity on airborne dispersal of settled fungal spores from carpet and vinyl tile flooring. A series of experiments were conducted in which commercial loop pile carpet, residential cut pile carpet, or vinyl tile installed in the experimental room were contaminated with Penicillium chrysogenum spores. The flooring materials were contaminated to two different levels (106 and 107 colony forming units per square meter [c.f.u./m2] of flooring surface). Airborne culturable and total P. chrysogenum concentrations were measured using Andersen single-stage impactor samplers and Burkard personal slide impactor samplers, respectively. Bioaerosol concentrations were measured at floor level, 1 meter, and the adult breathing zone (1.5 meter) heights before and after human activity consisting of walking in a prescribed pattern for 1 minute in the room. Airborne P. chrysogenum concentrations were greater with the higher surface loading for all three flooring materials. For all flooring materials there was no significant difference between sampler locations, although the data from the 1-meter location were the highest, followed by the floor level and the breathing zone locations, respectively. The data from these experiments indicate that while a very small fraction of culturable P. chrysogenum spores present on flooring materials were aerosolized by walking, relatively high airborne concentrations of spores maybe re-entrained from contaminated materials. The airborne P. chrysogenum concentrations were significantly higher after walking on cut pile carpet than with the other two flooring materials at both contamination levels, with the differences in concentration often ≥ 2 orders of magnitude. No differences were measured in airborne culturable P. chrysogenum between vinyl flooring and loop pile carpet at both contamination levels. Total spore data from the experiments with the 107 C.f.U./m2 contamination level indicated that walking on loop pile carpet produced higher airborne spore concentrations than similarly contaminated vinyl tile although no significant difference was observed at the 106 c.f.u./m2 level.