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For several years now, MVOC have been regarded as indicators for microbial growth in indoor environments. Until now, a direct correlation between the occurrence of microfungi and MVOC could not be shown in scientific investigations. One reason may be that different analytical methods were applied, and moreover they were not validated sufficiently. The present investigation aimed to test the comparability of both methods (Tenax adsorption/thermal desorption; charcoal adsorption/elution). It turned out that with both methods comparable results can be achieved if the technical handling of the calibration is standardized to a wide extent. Thus, highest demands have to be made on quality assurance. Therefore, it is necessary to formulate technical regulations for the quantification of MVOC.

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The intention of this study was the determination of the potential to reduce specific microbial bioaerosol (cultivable bacteria and fungi, total cell counts of microbes, airborne endotoxins and microbial volatile organic compounds, MVOC), odour and ammonia emissions from a pig facility by biofilters. Five identical biofilter units in half technical scale were filled with different filter materials (Biochips, coconut-peat, wood-bark, pellets + bark and compost) and connected in parallel to a piggery. The results showed obvious differences between the filter materials. Numbers of airborne cultivable bacteria were decreased by ca. 70 to 95% and the total counts of bacterial cells from ca. 25 to (>) 90%. The total amount of fungal cells was reduced by at least 60%, although the percentage of cultivable moulds in the air after passing the filters was sometimes higher than before. Airborne endotoxins and MVOC were effectively reduced by all filter materials to at least 90%. Regarding odour, the average reduction was between 40 and 83%, whereas only one of the filters proved to be capable of slightly reducing the ammonia emissions. No relationships between odour/ammonia and microbial bioaerosols with regard to the reduction efficiency of the different filter materials or the total load of the emitted air could be established. A tendency could be shown, that biofilters best capable to reduce odour emitted slightly more airborne bacteria, both cultivable and total cell counts.

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SETTING: Study of current asthma in adults in relation to the indoor environment. OBJECTIVES: To assess the effect of building dampness in dwellings on the occurrence of current asthma, and biochemical signs of inflammation. DESIGN: A nested case-control study with 98 prevalent cases of asthma and 357 controls, within a stratified random population sample (20-45 years) from the Uppsala, Sweden, part of the European Community Respiratory Health Survey (ECRHS). Current asthma was defined as a combination of bronchial hyperresponsiveness and at least one asthma symptom (wheeze or attacks of breathlessness). Statistical calculations were made by multiple linear or logistic regression, adjusting for age, sex and smoking. RESULTS: Building dampness was found in 27% of dwellings. Current asthma was more common among subjects living in damp dwellings (odds ratio [OR] 1.8; 95% confidence interval [CI] 1.1-3.0), particularly with dampness in the floor construction (OR = 4.6; 95% CI 2.0-10.5). The average forced expiratory flow in one second (FEV1) was lower and peak expiratory flow (PEF) variability was higher in subjects from dwellings with floor dampness, and blood eosinophil count was increased in damp dwellings. No relation was found between immediate type allergy to house dust mites and current asthma or building dampness. Immediate type allergy to moulds (Cladosporium or Alternaria) was more prevalent in damp dwellings (9.3% vs 3.9%), and was related to current asthma (OR = 3.4; 95% CI 1.4-8.5). CONCLUSIONS: Building dampness is common in dwellings in Sweden, and seems to be related to an increase in current asthma and biochemical signs of inflammation. Immediate type allergy to house dust mites does not seem to be the explanation, but immediate type allergy to moulds could explain some of the findings.

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In the context of microbial emissions from composting facilities the methods for the detection and identification of the groups of substances released, i.e. endotoxins, mycotoxins and Microbial Volatile Compounds (MVOC) are discussed. With the aid of an overview of the different methods employed for the investigation of the single groups of compounds the current state of the art in this field is presented. In conclusion the enormous research needs, especially with regard to the mycotoxins and MVOC, are pointed out.

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The statement presented here gives an overview and assessment of the procedures and concepts currently used for the collection and determination of airborne, culturable microorganisms at sources of emission within composting plants and in their near vicinity. The paper focuses on "classical" methods, which involve cultivation as an intermediate step for the determination of viable, airborne microorganisms. The theoretical and practical requirements on such methods are discussed. Results and experiences from recent investigations are described.

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The detection of airborne microorganisms including selected cell constituents (e.g. allergens or endotoxins) depends on suitable methods and instruments for their collection. Furthermore, microbiological methods are necessary for their quantification and qualification. In the past these methods were largely based on the classical cultivation dependent approach. Modern molecular methods, e.g. direct staining procedures, hybridization assays with nucleic acids including the PCR-technology or immunological assays are promising new tools for a more sophisticated detection of bioaerosols. They allow a better detection rate, a more precise identification of certain members of the aerosol including cell constituents. With respect to speed and lower costs they are an important alternative to established detection methods.

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Based on numerous publications dealing with the effects of microbial emissions on workers in waste processing plants and on few papers concerning the assessment of the environmental health relevance of microbial aerosols on people living in the vicinity of composting facilities, the current state of the art in this field is presented. With regard to occupational exposure the possible health effects like infections, toxicity and allergies are specified. Since to date only few studies have been made of populations exposed to microbial aerosols in ambient air, the environmental health aspects are reviewed in the context of a study of three compost plants in Hesse, where ambient air measurements as well as epidemiological investigations were carried out. Final recommendations are given and the research needs regarding the environmental health significance of microbial aerosols are formulated.

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As a part of a worldwide investigation on the prevalence of respiratory symptoms, we have performed a study on the relationship between the indoor environment and asthma-like symptoms in the population of a central Swedish municipality. The study comprised 88 individuals, aged 20-45 years who underwent a structured interview, spirometry, a methacholine provocation test, skin-prick tests and blood samples for measurements of serum concentrations of eosinophil cationic protein (S-ECP), blood eosinophil count and total immunoglobulin E (S-IgE). In the homes, the room temperature, air humidity, respirable dust, house dust mites (HDM) and airborne micro-organisms were measured. The relative humidity in all the homes was found to be above 33%. HDM were found in 13% of homes. In the homes of the 47 subjects with asthma related symptoms, significantly higher total levels of bacteria and mould (P < 0.05) and a higher proportion of detected HDM (OR = 5.3) was found than in subjects with no asthma related symptoms, after adjustment for age, sex, smoking, indoor temperature and air humidity. HDM were found to be an independent risk factor for asthma related symptoms (OR = 7.9) and nocturnal breathlessness (OR = 6.2) (P < 0.05), while the total level of bacteria was a risk factor for asthma related symptoms and wheezing (P < 0.05). We conclude that although HDM is relatively infrequently found in the homes of central-Sweden, the presence of HDM is related to asthmatic symptoms. A relation between levels of airborne bacteria and asthma related symptoms was also found.

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Scanning electron microscopy (SEM), light microscopy (LM), epifluorescence microscopy (FM), and culture were used to assess catches of microorganisms in parallel air samples on membrane filters from heavily contaminated working environments that differed in the relative abundance of bacteria, actinomycetes, and fungal spores. Except in pig houses, estimates by SEM and LM were similar, but those by FM and culture were smaller. However, in pig houses, the fluorescent stain enabled bacteria on skin scales, not seen by SEM or LM, to be counted. Although counts obtained by culturing were always smaller than those obtained by SEM or LM, they sometimes exceeded those obtained by FM. Counts suggested that 0.1-68% of bacteria + actinomycetes and 3-98% of fungal spores were viable. However, samples for culturing may have contained larger aggregates than parallel samples collected within a sampling apparatus. All spore types recognized by LM included aggregates--those of bacteria + actinomycetes sometimes exceeding 200 units, while Wallemia sebi spore aggregates were never larger than 3 spores. The size distributions of all types approximated to log-normal, although single spores and small aggregates of bacteria + actinomycetes were perhaps underrepresented. When spores were counted directly on the filter surface, as by SEM and LM, allowance was necessary for heavier deposition of particles near the center of filters by distributing counting fields systematically over the whole filter or a sector of it. Deposition was more uniform in graphite-filled polypropylene filter holders used open-faced. Losses within filter holders and during transportation from sampling site to laboratory were small. The precision of counting spore-containing particles by LM and SEM was better than that of counting individual spores. No such difference was found for FM because many large spore-containing particles were dispersed during preparation.

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Conidia of Penicillium brevi-compactum and Aspergillus fumigatus, sporangiospores of Rhizopus rhizopodiformis, spores of Streptomyces griseus, and bacterial cells of Bacillus subtilis were partitioned in two-phase systems consisting of dextran, polyethylene glycol, substituted positively charged sulfonylpolyethylene glycol, and water. At a pH of 2.8 in the system, the microorganisms showed 60 to 90% affinity for the upper, polyethylene glycol-rich phase, except for cells of B. subtilis, which were entirely located in the lower, dextran-rich phase. This partition behavior was used to separate microorganisms in aqueous suspensions of peat, wood fuel chip, and straw samples from organic dust impurities prior to total count by acridine orange staining and epifluorescence microscopy. Only one extraction of the interphase and lower phase was needed to separate approximately 98% of the conidia of Penicillium chrysogenum from a suspension containing peat dust.

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The total number of airborne micro-organisms collected on Nuclepore filters was determined by acridine orange staining and epifluorescence microscopy. The viable fraction of the total numbers varied significantly when actinomycete and fungal spores from different environments were stored on the filter surface for 1 week, although the microflora composition was not altered. A high correlation between viable and total counts was noted in environments where the airborne flora was dominated by fungal spores, while a low correlation was found for airborne bacteria. Peak values of the total counts registered in some work environments varied between 10(7) and 10(11) micro-organisms/m3. Size analysis showed a dominating fraction of respirable micro-organisms (aerodynamical diameter less than 5 micron). The investigation shows that it is of the utmost importance to combine viable counts with total count enumeration in the study of exposure to micro-organisms in work-related situations.

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A questionnaire was sent to 512 farmers, members of a local farmer's health association. Eighty were interviewed, and their serum precipitins and total serum immunoglobulin E (IgE) values were determined. Forty-five underwent extensive pulmonary function tests. On the basis of the clinical evaluation it was estimated that 19% of the farmers had experienced febrile reactions (fever and/or shivering) following exposure to organic dust, 50% of the 19% having been exposed within the last 2.5 years. Common causes were moldy grain, hay, and woodchips. The pulmonary function, gas exchange, and chest radiographs of those who had previously had febrile reactions were normal. Only 13% showed positive precipitin reactions in Ouchterlony double-diffusion tests. With more sensitive tests, positive precipitins were found in 59%, but they were negatively correlated with febrile episodes. Air samples collected during work with hay and grain on 21 farms contained between 10(7) to 2 X 10(9) microorganisms/m3. The highest values were associated with symptoms of alveolitis. Eleven percent of the farmers reported obstructive chest symptoms following exposure to organic dust. This group showed decreased pulmonary function and elevated serum IgE levels and included a high proportion of smokers and exsmokers. No correlation was found between febrile and obstructive reactions.

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Nuclepore filters (polycarbonate) were compared with a slit sampler for the collection of airborne fungi particles. To enable high spore-concentration sampling, the slit sampler method was modified by the use of collection gels consisting of agar or glycerol/gelatin. The exposed gels were homogenized (agar) or melted (glycerol/gelatin), diluted, and spread on cultivation media. No significant difference was found between the Nuclepore filter method and the slit sampler method when glycerol/gelatin gels were used in the interval 10(3)-10(8) colony-forming units (cfu) per cubic meter. The lower trapping efficiency with agar gel was probably caused by water evaporating from the medium. The efficiency of a personal cascade impactor (Sierra) was compared with that of the Nuclepore filter method. The collection media used in the personal cascade impactor was modified for the determination of colony-forming units by moistening the collection filters with glycerol. The exposed filters were extracted with sterile water, and the suspension was diluted and spread on cultivation media. In trapping efficiency, the personal cascade impactor was similar to the Nuclepore filter method. The cut point of the personal cascade impactor showed high conformity with that of an Andersen sampler.

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