Variabilities in aerosolizing activities and airborne fungal concentrations in a bakery

Concentrations of airborne culturable fungi were measured in the kitchen of a bakery in Boston, Mass., to evaluate variabilities associated with common worker activities, outdoor aerosol distributions, and season. Activities were categorized as early morning preparation, cornmeal sifting and tossing, flour dumping and mixing, sweeping, and low activity. Sets of measurements were taken over 1 day in spring and 1 day in summer. Fungal concentrations were measured using a one-stage culture plate impactor, and bulk samples were taken from suspected fungal reservoirs within the bakery and subsequently cultured. Compared with the low activity category, elevated levels of total culturable fungi were found during all other activities, with the amount of increase closely related to individual worker activity as well as outdoor concentrations and initial bakery conditions. In the spring, Penicillium was the dominant genus showing activity-related elevations in concentrations, while Cladosporium was the dominant genus during the summer. Clearly, due to variabilities in worker activities and ambient fungal concentrations, a standardized sampling protocol involving a large sample size over multiple days is needed to estimate accurately exposure to either total airborne fungi or specific fungal taxa.