Peter A. Nielsen

Production of mycotoxins on artificially and naturally infested building materials

In this study, the ability to produce mycotoxins during growth on artificially infested building materials was investigated for Penicillium chrysogenum, Pen. polonicum, Pen. brevicompactum, Chaetomium spp., Aspergillus ustus, Asp. niger, Ulocladium spp., Alternaria spp., and Paecilomyces spp., all isolated from water-damaged building materials. Spores from the different isolates of the above mentioned species were inoculated on gypsum board with and without wallpaper and on chipboard with and without wallpaper. Fungal material was scraped off the materials, extracted, and analyzed using high performance liquid chromatography-diode array detection and thin layer chromatography. All six isolates of C. globosum produced the toxic chaetoglobosins A and C, at levels of up to 50 and 7 μg/cm2 respectively. The quantities of secondary metabolites produced by Penicillia were generally low, and no toxin production was detected from any of the five isolates of Pen. chrysogenum. Both isolates of Pen. polonicum produced 3-methoxy-viridicatin, verrucosidin, and verrucofortine. Two of five isolates of Pen. brevicompactum produced mycophenolic acid. From five out of six isolates of Alternaria spp., alternariol and alternariol monomethyl ether were detected. From Ulocladium spp., Paecilomyces spp., and Asp. ustus no known mycotoxins were detected, although the latter two are known mycotoxin producers. Asp. niger produced several naphtho-γ-pyrones and tetra-cyclic compounds. All investigated species, especially Asp. ustus and Asp. niger produced many unknown secondary metabolites on the building materials. Analyses of wallpaper and glass-fibre wallpaper naturally infested with Asp. versicolor revealed sterigmatocystin and 5-methoxysterigmatocystin. Analyses of naturally infested wallpaper showed that C. globosum produced the chaetoglobosins A and C, and Pen. chrysogenum produced the antibiotic meleagrin.

Production of mycotoxins on artificially inoculated building materials

Isolates of Stachybotrys chartarum, Aspergillus versicolor and Trichoderma spp. from water damaged Danish buildings were grown on old and new gypsum boards, wood pieces, chipboard, gypsum board with wallpaper and acoustic ceiling tiles. Production of sterigmatocystin and 5-methoxysterigmatocystin by each of 5 isolates of A. versicolor growing on pine wood, wallpaper, gypsum board and chipboard, were detected using HPLC with diode array detection and TLC with AlCl3 staining. After derivatization to the heptafluorobutyrlated ester and using gas chromatography ion trap mass spectrometry, negative ion chemical ionisation, for detection, trichothecenes of the verrucarol type were found in 4 of 5 isolates of S. chartarum growing on old and new gypsum boards. None of 8 Trichoderma isolates produced the trichothecenes T-2 toxin, HT-2 toxin, diacetoxyscirpenol, fusarenon-X, deoxynivalenol, nivalenol or trichothecenes of the verrucarol or trichodermol type on any of the above mentioned materials.

Moulds in floor dust - a particular problem in mechanically ventilated rooms? A study of adolescent schoolboys under the Danish moulds in buildings program.

OBJECTIVE To test the hypothesis that the association between levels of mould in floor dust and prevalence of potentially building-related symptoms may depend on the type of ventilation. METHODS This stratified cross-sectional study is part of the Danish moulds in buildings program (DAMIB), including 503 adolescent schoolboys aged 13-17 years at 15 schools. Besides assessing symptom prevalences in questionnaires, we measured numerous potential risk factors in the school buildings. RESULTS Stratifying on type of ventilation (natural, exhaust only, or full mechanical ventilation system), the negative effect of high levels of mould in floor dust was more pronounced in rooms with mechanical ventilation system. With a variable combining high level of moulds in floor dust with type of ventilation in the classroom, a significantly increased risk was found for all symptoms in the mechanically ventilated classrooms with high mould concentrations. In multiple logistic regression models, significant odds ratios (OR) ranged from 3.9 [95% confidence interval (95% CI) 1.5-10.1] (nasal congestion) to 17.0 (95% CI 2.1-138) (dizziness). CONCLUSIONS The combined effect of moulds in dust and ventilation form might be a result of the higher air flow keeping the dust in the breathing zone for a longer time, thereby increasing the exposure for the occupants of the classrooms. It is important in future indoor air research also to focus on the combination effects of risk factors, including the type of ventilation.