Aerosolization of mycotoxins after growth of toxinogenic fungi on wallpaper

Many fungi can develop on building material in indoor environments if moisture 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 the mycotoxin production by Penicillium brevicompactum, Aspergillus 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 substrate. The propensity to aerosolization differed according to the fungal species. Thus, particles were aerosolized from wallpaper contaminated with P. brevicompactum when air velocity of just 0.3 m/s was applied, where S. chartarum required air velocity of 5.9 m/s. A versicolor was intermediate since aerosolization occurred under air velocity of 2 m/s.Quantification of the toxic content revealed that toxic load was mostly associated with particles of size equal or higher of 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 penetrate deeply in the respiratory tract upon inhalation. These elements are important for risk assessment related to mouldy environments. The possible colonisation of building material by toxinogenic fungi in case 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 mouldy material. This transfer to air requires air velocities that can be encountered in « real life conditions » in buildings. The most part 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 into human respiratory tract. All these data are important for risk assessment related to fungal contamination of indoor environments.