Assessment of Workers’ Exposure to Bioaerosols in a French Cheese Factory

Abstract

Hundreds of different cheeses are produced in France, where 23.9kg of cheese were consumed per inhabitant in 2009, when it was ranked the second cheese-consuming nation. To meet this considerable demand, a large number of cheese factories exist where many workers, especially cheese washers, may be exposed to fungal bioaerosols that can lead to adverse toxinic and allergic effects. Airborne bacteria, fragments, or microbial by-products (endotoxins) are also found and contribute to total worker exposure. However, there is almost no published data concerning worker exposure or characteristics of bioaerosols emitted during these activities. Here, we measured the parameters (concentrations, species present, and size distribution) of the culturable fungal bioaerosol emitted in a French natural-rind cheese-maturing cellar. Concentrations of airborne bacteria and endotoxins were also measured. The main tasks were investigated using stationary or personal sampling over three consecutive days. Depending on the work area, high concentrations of culturable mesophilic microorganisms were measured (using closed-face cassettes): from 10(4) to 2×10(8) CFU m(-3) for fungi and from 10(3) to 10(6) CFU m(-3) for bacteria. These concentrations are 10- to 100000-fold higher than those measured at two reference points (indoor and outdoor) that are assumed not to be contaminated by the plant's activities. Endotoxin concentrations were between 10 and 300 EU m(-3) in the plant. Exposure was further assessed by identifying the predominant culturable fungi (allergenic Mucor fuscus and Penicillium sp.) and by measuring particle size distributions (cascade impactor). Airborne fungal entities (spores, mycelium strands and fragments, agglomerates, etc.) were found with aerodynamic diameters from 3 to over 20 µm. A metrological approach was used to fully characterize the culturable fungal aerosols generated during cheese maturing in this plant. The results show that workers are exposed to concentrations of airborne culturable fungi, sometimes very high, throughout the manufacturing process. In addition to fungi, culturable bacteria and endotoxins are also present in the work atmosphere. All these microbial organisms thus contribute in a complex manner to total worker exposure. Despite the lack of both occupational exposure limit values and standardized measuring methods, our results suggest that an immunological risk may occur among workers, especially for cheese brushers, cheese washers, and packagers who are the most exposed workers in the factory.

Occurrence and Identification of Yeasts in Production of White-Brined Cheese

“…Supporting our results, microbial air loads of 1-3 log CFU/m 3 have commonly been reported in dairy plants [18,26,27]. Until now, there is no legislation concerning the limits of airborne contaminants in dairy production, though several scientific recommendations have been published [28][29][30][31].…”

Fungal Fragments and Fungal Aerosol Composition in Sawmills

“…Several other studies from sawmills have shown quite higher concentrations of spores that were associated with airway impairments among workers (median: 1.3 × 10 5 m −3 ( Johard et al, 1992 ); 2 × 10 5 m −3 ( Halpin et al, 1994 ); 5 × 10 5 m −3 ( Dahlqvist and Ulfvarson, 1994 ); 4 × 10 5 m −3 ( Mandryk et al, 1999 ); AM: 1.4 × 10 6 m −3 ( Eduard et al, 1992 ). However, much higher exposure levels have been reported at other workplaces including farming: 26 × 10 5 m −3 ( Eduard et al, 2004 ), grain farming: 40 × 10 5 m −3 ( Halstensen et al, 2007 ), and cheese factory: 54–1500 × 10 5 m −3 ( Simon and Duquenne, 2014 ). The differences in spore exposure in sawmills can be attributed to various parameters including sampling conditions (stationary versus personal, inhalable versus thoracic or respirable), modernization levels of facilities that may help reduce fungal colonization of timber and subsequent exposure, or the spatial and temporal variation in fungal growth and sporulation.…”

Evaluation of Bioaerosol Bacterial Components of a Wastewater Treatment Plant Through an Integrate Approach and In Vivo Assessment

“…Fungal spores and bacteria have a typical aerodynamic diameter (Da) of about 1.5-30 and 1-3 µm, respectively [18], and due to their small size, they become a potential cause of infections in immune-compromised people once inhaled and may cause allergic responses [19]. Most studies on bioaerosol have traditionally been conducted by collecting and analyzing fungal spores and bacterial cells with total-count and culture techniques [20][21][22][23]. However, since the end of nineties, it has been estimated [24][25][26] that only 1.5%-15.3% of airborne microbial cells can be enumerated by the direct counting of the colonies (viable microorganisms) after incubation on Tryptic Soy Agar (TSA) [27].…”