Occupational exposures to fungal bioaerosols: example in a cheeses' maturing factory

Hundreds types of cheese are produced in France (second world’s consumer with 25.6 kg/year/inhabitant in 2010). Plants involved in this occupational sector are numerous and many workers may be exposed to fungal bioaerosols and may develop adverse health effects (toxinic and allergic). However, there is almost no published data concerning workers’ exposures and characteristics of fungal aerosols emitted from these occupational activities. The aim of the study was to build a metrological approach for the assessment of workers’ exposure levels and to measure descriptive parameters of the fungal bioaerosol (concentrations, species identification and size distribution of airborne particles) emitted in a French natural rind cheeses maturing cellar.
Main working tasks were investigated with static and individual sampling for three consecutive days. The measurement strategy includes considerations on aerosol sampling (choice of the samplers, sampling time, particle size fraction, etc.), transport of the samples and analytical methods (culture, identification, etc.). It has been elaborated in agreement with scientific published data in order to better interpret the results, despite the lack of both occupational exposure limit values and standardized sampling and analytical methods.
Depending on the working area, high concentrations were measured: from 105 to 108 CFU.m-3 for cultivable fungi (closed-face cassette). The exposure assessment was improved by identifying cultivable fungi (allergenic Mucor fuscus and Penicillium sp.) and by measuring particle size distributions. Airborne fungal entities (spores, mycelium strands and fragments, agglomerates, etc.) show aerodynamic diameters between 3 and 40 µm, with a size mode for the impactor stage 6-9.8 µm. Our metrological approach allowed a complete characterization of fungal aerosols generated during the cheeses’ maturing.
Thus, the exposure assessment demonstrates an immunological risk among workers, especially for cheese-brushers, cheese-washers and packaging activities.