Search

Mold concentrations of house dust samples from dwellings reportedly free from mold infestations were analysed to obtain background values. Samples from carpet floors were taken from 80 dwellings in three parts of Germany in winter and summer. Samples were analysed with the cultivation method (using suspension). This resulted in the detection of 35 mold species or genera. Concentrations of the genera Alternaria, Cladosporium, Fusarium and yeast increased in summer. In contrast concentrations of Aspergillus and Penicillium in the summer samples were nearly equal to those in the winter samples. The majority of the various molds were only found in a number of samples too small for a reliable comparison of the winter and summer findings to be made. The results were compared with findings of other authors. The authors propose the concentrations of the 95th percentile of each species (when representing over 10,000 KBE/g of dust) as background values, while a threefold higher value is regarded as an indication of mold presence. An exception should be made for the concentrations of molds which increase sharply in the outdoor air in summer. Because of the difficulty in estimating the outdoor influence, no evaluation proposals can be given for these species for the summer season.

Examination of dust samples is widely used to detect sources of mold growth in indoor environments. The advantage of this investigation is that house dust can be regarded as a passive sampler collecting mold spores over a long time period. No generally accepted method exists, however, for sampling and analysis of house dust for the detection of molds. Therefore, results obtained by different laboratories are not comparable. Measurements with standardized validated methods are a prerequisite to assess concentrations of molds in indoor environments. The method presented is based on sampling with a modified filter holder (in accordance with VDI 4300 page 8). Mini-sieves of different sizes are used for sample preparation. The fraction <63 microm is used for cultivation of molds after suspension. Problems of dust sampling and preparation are discussed. Criteria for the detection of sources of mold growth based on dust samples are presented elsewere.

In co-ordination with the Umweltbundesamt Berlin, the Landesgesundheitsamt Baden-Wurttemberg (LGA) initiated external quality assurance in the diagnosis of indoor fungi in autumn 2001. Four of six fungal strains commonly found indoors have to be fully identified (on the genus and species level). There are two distributions per year; the six distributions hitherto carried out resulted in correct identification by 46-89% of laboratories (40-71 participants, total 148). It is clear from the results that repeat participants were more successful. In addition to the pure cultures sent out we offered actual samples (two air samples, one wood material, one sample of house dust, hitherto); 43- 69% of participating laboratories also took part in this facultative investigation of actual samples and 29-62% were successful. Results that differed considerably revealed problems while treating and evaluating actual samples. Therefore, activities in this field should be enhanced. In conclusion, external quality assurance in the diagnosis of indoor fungi is a useful management aid in the maintenance and improvement of laboratory performance.

The assessment of mold concentrations in air samples requires generally accepted evaluation criteria. It is not possible to derive guideline values based on risk assessment. Background concentrations are therefore used as the basis for the assessment of measured concentrations. The assessment criteria established by the Federal Environmental Agency in Berlin and by the State Health Agency of Baden-Wurttemberg are founded on the experience of some laboratories. The general application of these criteria is only meaningful if validated and generally applied methods of analysis are used. Until now, laboratories have been using many different methods for sampling and detection of culturable molds and total spore counts in air. In this study, different steps for sampling by impaction or filtration are validated. The results presented will contribute to standardization of sampling and detection of molds in air.

The mold concentration of indoor air and outdoor air in three parts of Germany was investigated in both winter and summer. In total, air samples from 80 dwellings, reportedly free from mold infestations, were analysed with both the cultivation method and the total spore count method. With the cultivation method, 40 mold species and genera were differentiated, while with the total spore count method, 11 spore types were distinguished. The concentration of the genera Alternaria, Cladosporium, Fusarium and yeast increased in summertime. In contrast, the concentrations of Aspergillus and Penicillium measured in summer were nearly equal to those measured in winter. The majority of the various molds were only found in a small number of samples, too small for a reliable comparison of the winter and summer findings. The 95th percentile of the indoor mold concentrations is suggested as the upper limit of the background concentration. The results are discussed comparing the assessment proposals of various authors, and a new assessment proposal is described.