真菌の成長による揮発性有機化合物の発生挙動と加湿器からの発生調査

抄録

 Fungi as a microbial contamination of indoor environments may cause a complex spectrum of health effects. Spores of fungi may cause allergies, asthma and sometimes contain mycotoxins. Microorganisms also produce many volatile organic compounds (microbial volatile organic compound (MVOC)). The toxicological aspect of MVOCs may be negligible because of low concentrations in indoor spaces, however MVOCs sometimes attribute an unpleasant smell.

 This study aimed to measure volatile organic compounds emitted from fungi by the small chamber method and investigate emission patterns of MVOCs as fungal growth processes. Furthermore, to investigate the emission compounds from HVAC systems in a building that had odor problems in the room in summer season, the biological contaminants on the humidifier were identified and the small chamber tests for emissions from the humidifier element and biological contaminants were carried out.

 The Cladosporium cladosporioides, Penicillium pinophilum, Aspergillus niger and mixture of these three fungi on the PDA (potato dextrose agar) medium and DG18 (dichloran glycerol) agar without glycerol were installed in the stainless small chamber (20L), and the emitting volatile organic compounds were sampled with DNPH cartridge and Tenax sampler during 2 weeks. The temperature and humidity inside the chamber were kept at 25 °C and 70-90 %, respectively. The samples were analyzed with a high performance/pressure liquid chromatography (HPLC) and a gas chromatograph / mass spectrometer (GC/MS). The sampling of emitting MVOCs and observation of the fungal growth under a microscope were carried out at fixed intervals for 2 weeks.

 Fungal threads of all samples invisibly grew until 2 days, and growth and changing color of spores to black or yellow were occurred after 3 or 4 days. P. pinophilum changed its color to blue after 7 days again. The relationships between the growth of the fungal threads and spores, and MVOC emitting rates were investigated. Fungi could not be visible but grew their thread, however invisible fungi emit MVOCs such as acetaldehyde, acetone, 2-methyl-1-propanol and etc. When the fungi grew with their spores and change their color, other MVOCs such as 3-methyl-1-butanol, 1-octen-3-ol were emitted in 2 weeks. Then as stopping growing, MVOC emissions decreased.

 From the chamber test for the humidifier element and fungi on agar mediums, Fusarium sp. was detected on the elements and MVOC from Fusarium sp. could be identified as dimethyl disulfide. Since dimethyl disulfide was also detected from the humidifier element by the chamber method, the source of the odor in the room could be the humidifier element surface contaminated by Fusarium sp.