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Many fungi can develop on building material in indoor environments if the moisture level is high enough. Among species that are frequently observed, some are known to be potent mycotoxin producers. This presence of toxinogenic fungi in indoor environments raises the question of the possible exposure of occupants to these toxic compounds by inhalation after aerosolization. This study investigated mycotoxin production by Penicillium brevicompactumAspergillus versicolor, and Stachybotrys chartarum during their growth on wallpaper and the possible subsequent aerosolization of produced mycotoxins from contaminated substrates. We demonstrated that mycophenolic acid, sterigmatocystin, and macrocyclic trichothecenes (sum of 4 major compounds) could be produced at levels of 1.8, 112.1, and 27.8 mg/m2, respectively, on wallpaper. Moreover, part of the produced toxins could be aerosolized from the substrate. The propensity for aerosolization differed according to the fungal species. Thus, particles were aerosolized from wallpaper contaminated with P. brevicompactum when an air velocity of just 0.3 m/s was applied, whereas S. chartarum required an air velocity of 5.9 m/s. A. versicolor was intermediate, since aerosolization occurred under an air velocity of 2 m/s. Quantification of the toxic content revealed that toxic load was mostly associated with particles of size ≥3 μm, which may correspond to spores. However, some macrocyclic trichothecenes (especially satratoxin H and verrucarin J) can also be found on smaller particles that can deeply penetrate the respiratory tract upon inhalation. These elements are important for risk assessment related to moldy environments.

IMPORTANCE The possible colonization of building material by toxinogenic fungi in cases of moistening raises the question of the subsequent exposure of occupants to aerosolized mycotoxins. In this study, we demonstrated that three different toxinogenic species produce mycotoxins during their development on wallpaper. These toxins can subsequently be aerosolized, at least partly, from moldy material. This transfer to air requires air velocities that can be encountered under real-life conditions in buildings. Most of the aerosolized toxic load is found in particles whose size corresponds to spores or mycelium fragments. However, some toxins were also found on particles smaller than spores that are easily respirable and can deeply penetrate the human respiratory tract. All of these data are important for risk assessment related to fungal contamination of indoor environments.

Aerosolization of Mycotoxins after Growth of Toxinogenic Fungi on Wallpaper
Brankica Aleksic, Marjorie Draghi, Sebastien Ritoux, Sylviane Bailly, Marlene Lacroix, Isabella P. Oswald, Jean-Denis Bailly, and Enric Robine
Appl. Eviron. Microbiol. August 2017 83:e01001-17; Accepted manuscript posted online 23 June 2017 ,
doi: 10.1128/AEM.01001-17

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