Potentially harmful secondary metabolites produced by indoor Chaetomium species on artificially and naturally contaminated building materials.

The presence of the fungal genus Chaetomium and its secondary metabolites in indoor environments is suspected to have a negative impact on human health and well-being. About 200 metabolites have been currently described from Chaetomium spp., but only the bioactive compound group, chaetoglobosins, have been screened for and thus detected in buildings. In this study, we used a liquid chromatography high-resolution mass spectrometry approach to screen both artificially and naturally infected building materials for all the Chaetomium metabolites described in the literature. Pure agar cultures were also investigated to establish differences between metabolite production in vitro and on building materials as well as in comparison with non-indoor reference strains. On building materials, six different chaetoglobosins were detected in total concentrations of up to 950 mg/m2 from Chaetomium globosum along with three different chaetoviridins/chaetomugilins in concentrations up to 200 mg/m2 . Indoor Chaetomium spp. preferred wood-based materials over gypsum, both in terms of growth rate and metabolite production. Cochliodones were detected for the first time on all building materials infected by both C. globosum and Chaetomium elatum and are thus candidates as Chaetomium biomarkers. No sterigmatocystin was produced by Chaetomium spp. from indoor environment.

Pre-contamination of new gypsum wallboard with potentially harmful fungal species.

Gypsum wallboard is a popular building material, but is also very frequently overgrown by Stachybotrys chartarum after severe and/or undetected water damage. The purpose of this study was to determine whether Stachybotrys and other fungi frequently isolated from wet gypsum wallboard are already present in the panels directly from the factory. Surface-disinfected gypsum disks were wetted with sterile water, sealed, and incubated for 70 days. The results showed that Neosartorya hiratsukae (≡ Aspergillus hiratsukae) was the most dominant fungus on the gypsum wallboard followed by Chaetomium globosum and Stachybotrys chartarum. Our results suggest that these three fungal species are already embedded in the materials, presumably in the paper/carton layer surrounding the gypsum core, before the panels reach the retailers/building site.