Microbial growth in building material samples and occupants' health in severely moisture-damaged homes

There is no commonly approved approach to detect and quantify the health-relevant microbial exposure in moisture-damaged buildings. In 39 single-family homes with severe moisture damage, we studied whether concentrations of viable microbes in building material samples are associated with health among 71 adults and 68 children, and assessed with symptoms questionnaires, exhaled NO, and peak expiratory flow (PEF) variability. Symptoms were grouped into three scores: upper respiratory symptoms, lower respiratory symptoms, and general symptoms. The homes were divided into three groups based on viable counts of fungi, actinomycetes, and total bacteria cultivated from building material samples. Highest group of actinomycete counts was associated with more general symptoms, worse perceived health, and higher daily PEF variability (aOR 12.51; 1.10-141.90 as compared to the lowest group) among adults, and with an increase in lower respiratory symptoms in children, but the confidence intervals were wide. We observed significant associations of fungal counts and total microbial score with worse perceived health in adults. No associations with exhaled NO were observed.

Patients hospitalized abroad as importers of multiresistant bacteria-a cross-sectional study

OBJECTIVES

The pandemic spread of multidrug-resistant (MDR) bacteria poses a threat to healthcare worldwide, with highest prevalence in indigent regions of the (sub)tropics. As hospitalization constitutes a major risk factor for colonization, infection control management in low-prevalence countries urgently needs background data on patients hospitalized abroad.

METHODS

We collected data on 1122 patients who, after hospitalization abroad, were treated at the Helsinki University Hospital between 2010 and 2013. They were screened for methicillin-resistant Staphylococcus aureus (MRSA), extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-PE), vancomycin-resistant enterococci, carbapenemase-producing Enterobacteriaceae (CPE), multiresistant Pseudomonas aeruginosa and multiresistant Acinetobacter baumannii. Risk factors for colonization were explored by multivariate analysis.

RESULTS

MDR colonization rates were higher for those hospitalized in the (sub)tropics (55%; 208/377) compared with temperate zones (17%; 125/745). For ESBL-PE the percentages were 50% (190/377) versus 12% (92/745), CPE 3.2% (12/377) versus 0.4% (3/745) and MRSA 6.6% (25/377) versus 2.4% (18/745). Colonization rates proved highest in those returning from South Asia (77.6%; 38/49), followed by those having visited Latin America (60%; 9/16), Africa (60%; 15/25) and East and Southeast Asia (52.5%; 94/179). Destination, interhospital transfer, short time interval to hospitalization, young age, surgical intervention, residence abroad, visiting friends and relatives, and antimicrobial use proved independent risk factors for colonization.

CONCLUSIONS

Post-hospitalization colonization rates proved higher in the (sub)tropics than elsewhere; 11% (38/333) of carriers developed an MDR infection. We identified several independent risk factors for contracting MDR bacteria. The data provide a basis for infection control guidelines in low-prevalence countries.

The bedding of laboratory animals as a source of airborne contaminants

In work environments with laboratory animals, the bedding of animals binds the excreta as well as other compounds originating from the animals and their environment. These may be generated into the ambient air when the personnel handle bedding in different procedures. This study compares the dustiness of different types of six clean and four soiled beddings from rat or mouse cages. The dust generation of clean bedding varied from <1 to 25 mg/m3. When used in the cages of rats or mice for 4 days, the dust concentration of the beddings decreased, increased or stayed the same, depending on the type of bedding and animal species. A decrease in dustiness was, however, more common. The levels in the soiled beddings varied from <1 to 8.6 mg/m3. In the case of the aspen chip bedding, the contents of bedding used in mouse, rat or rabbit cages were analysed for mesophilic bacteria and fungi, mycobacteria and endotoxins. All of these contaminants were variably found in the bedding samples, the maximal concentrations for bacteria were >6 500 000 colony-forming units (cfu)/g, for fungi 212 000 cfu/g, and for endotoxins 6500 ng/g (81 000 EU/g). The results showed that the bedding of laboratory animals may contain biologically effective compounds, and that these may be distributed into the ambient air depending on the characteristics of the bedding material. The dustiness of different bedding types is an important factor affecting the amount and quality of the occupational exposure of the personnel to airborne contaminants.

Determinants, reproducibility, and seasonal variation of bacterial cell wall components and viable counts in house dust

The objectives of this study were (i) to assess the determinants that affect concentrations of the bacterial cell wall components 3-hydroxy fatty acids (3-OH FAs) and muramic acid and of total viable bacteria and actinomycetes in house dust; and (ii) to examine the seasonal variation and reproducibility of these bacterial cell wall components in house dust. A number of lifestyle and environmental factors, mostly not consistent for different bacterial measures but commonly including the type of dwelling and farming (number of livestock), explained up to 37% of the variation of the bacterial concentrations in 212 homes in Eastern Finland. The reproducibility of 3-OH FAs and muramic acid measurements in house dust were studied in five urban homes and were found to be generally high (ICC 74-84%). Temporal variation observed in repeated sampling of the same home throughout a year was more pronounced for 3-OH FAs determinations (ICC 22%) than for muramic acid (ICC 55-66%). We conclude that determinants vary largely for different types of bacterial measurements in house dust; the measured parameters represent different aspects of the bacterial content indoors. More than one sample is needed to describe bacterial concentrations in house dust in the home environment due to large temporal variation.

Indoor fungi: companions and contaminants

This review discusses the role of fungi and fungal products in indoor environments, especially as agents of human exposure. Fungi are present everywhere, and knowledge for indoor environments is extensive on their occurrence and ecology, concentrations, and determinants. Problems of dampness and mold have dominated the discussion on indoor fungi. However, the role of fungi in human health is still not well understood. In this review, we take a look back to integrate what cultivation-based research has taught us alongside more recent work with cultivation-independent techniques. We attempt to summarize what is known today and to point out where more data is needed for risk assessment associated with indoor fungal exposures. New data have demonstrated qualitative and quantitative richness of fungal material inside and outside buildings. Research on mycotoxins shows that just as microbes are everywhere in our indoor environments, so too are their metabolic products. Assessment of fungal exposures is notoriously challenging due to the numerous factors that contribute to the variation of fungal concentrations in indoor environments. We also may have to acknowledge and incorporate into our understanding the complexity of interactions between multiple biological agents in assessing their effects on human health and well-being.

Determinants, reproducibility, and seasonal variation of ergosterol levels in house dust

This study aimed to clarify the determinants that affect the concentrations of ergosterol and viable fungi in house dust and to examine the seasonal variation and reproducibility of ergosterol concentrations indoors. In studying the determinants, dust samples from living room floors and vacuum cleaner dust bags were collected from 107 farming and 105 non-farming homes. Ergosterol levels were determined with gas chromatography-mass spectrometry,and the dust bag dust was cultivated for enumeration of fungal genera. Lifestyle and environmental factors, for example using of the fireplace, and visible mold observations in homes, explained 20–26% of the variation of fungal concentrations. For the reproducibility study, samples were collected from five urban homes in four different seasons. The reproducibility of ergosterol determinations within a sample was excellent (ICC = 89.8) for floor dust and moderate (ICC = 63.8) for dust bag dust, but poor when sampling the same home throughout a year (ICC = 31.3 and 12.6, respectively) due to large temporal variation in ergosterol concentrations. In conclusion, environmental characteristics only partially predicted the variation of fungal concentrations. Based on these studies, we recommend repeated sampling of dust over time if one seeks to adequately describe overall fungal levels and exposure in a home.

PRACTICAL IMPLICATIONS

This study shows that levels of ergosterol and viable fungi in house dust are related to visible mold observations. Only 20% of the variation in fungal levels can be explained with questionnaires, and therefore, environmental samples need to be taken in addition. Reproducibility of ergosterol determination was excellent for floor dust, and thus, ergosterol measurements from floor dust samples could be suitable for assessing the fungal load in building investigations. The temporal variation needs to be taken into account when describing the ergosterol concentration of urban homes.

Indoor environmental quality in school buildings, and the health and wellbeing of students

Poor indoor environmental quality (IEQ) in classrooms may be a risk for health symptoms and cause absence from school. We conducted a comprehensive study in order to assess the connection between IEQ in Finnish elementary school buildings and the health and academic performance of sixth grade students. The specific aim of the present paper was to study the school- or grade-level prevalence of symptoms in relation to IEQ. The school- or grade-level (i.e. group level) prevalence of self-reported symptoms and perceived IEQ was studied using data collected by a health questionnaire comprising 37 questions. The health questionnaire was sent to all 6th grade students in a stratified random sample of 355 elementary schools in Finland. Indoor environmental conditions were assessed with measurements of ventilation rate and thermal conditions of classrooms in a subsample of 56 schools. Altogether 297 elementary schools participated in the health questionnaire study and a total of 4248 questionnaires were returned (estimated response rate 62.6%). The most common weekly symptoms in the spring semester were fatigue (7.7%), stuffy nose (7.3%), and headache (5.5%). However, both mean prevalence values for different symptoms among all 6th grade students and group-level prevalence values for specific symptoms varied considerably. On the group level, the prevalence values most frequently found above 95% CI (calculated for N=15) were wheezing, cough with wheezing, and fever over 37°C. The most frequently reported IEQ factors causing daily inconvenience in classrooms were noise (11.0%) and stuffy air/poor indoor air quality (IAQ) (7.0%), which were also found most frequently above 95% CI on the group level (calculated for N=15), together with self-reported high indoor temperature and dust or dirtiness. Self-reported daily stuffiness/poor IAQ was significantly correlated with measured mean temperatures and ventilation rates in classrooms. High prevalence of students' self-reported stuffiness/poor IAQ may indicate high indoor temperature or low ventilation rate in classrooms. Also high group level prevalence of other IEQ factors and certain symptoms may be indicative of IEQ problems that should be further studied. The results of this study can be used as a reference for assessing the questionnaire-based prevalence of self-reported symptoms among 6th graders, and their association with IEQ in classrooms. For such assessment, the number of students responding to the questionnaire must be carefully considered, also bearing in mind that prevalence values are symptom specific.

Occurrence of moisture problems in schools in three countries from different climatic regions of Europe based on questionnaires and building inspections - the HITEA study

The aim of this study was to assess occurrence of dampness and mold in school buildings in three European countries (the Netherlands, Spain, and Finland), representing different climatic regions. An assessment was performed utilizing both questionnaires and on-site building investigations, and the agreement between these two methods was evaluated for validation purposes. On the basis of questionnaire data from a representative sample of schools, different types of moisture problems were reported in 24-47% of all school buildings at the time of the study. Most commonly reported was dampness in the Netherlands, moisture/water damage in Spain, and mold odor in Finland. Subsequently, 20-24 schools per country were selected for on-site inspections by trained staff. The overall agreement between the questionnaire and inspection data was good (kappa-value 0.62), however, with large differences (0.39-0.91) between countries. Extrapolating from the inspection data, the minimum estimates for prevalence of moisture problems in school buildings are 20% in the Netherlands, 41% in Spain, and 24% in Finland. In conclusion, moisture problems (such as moisture damage, dampness, and mold) are relatively common in schools. The occurrence and severity may vary across geographical areas, which can be partly explained by building characteristics.

PRACTICAL IMPLICATIONS

On the basis of this study, the prevalence of verified moisture problems in school buildings was highest in Spain, but lower and similar in Finland and the Netherlands. Questionnaire-based surveys can be used to assess moisture problems in school buildings, but because of large variation in agreement with inspection data, the questionnaire needs to be validated by on-site inspections in a subsample of the surveyed buildings.

Microbial secondary metabolites in school buildings inspected for moisture damage in Finland, The Netherlands and Spain

Secondary metabolites produced by fungi and bacteria are among the potential agents that contribute to adverse health effects observed in occupants of buildings affected by moisture damage, dampness and associated microbial growth. However, few attempts have been made to assess the occurrence of these compounds in relation to moisture damage and dampness in buildings. This study conducted in the context of the HITEA project (Health Effects of Indoor Pollutants: Integrating microbial, toxicological and epidemiological approaches) aimed at providing systematic information on the prevalence of microbial secondary metabolites in a large number of school buildings in three European countries, considering both buildings with and without moisture damage and/or dampness observations. In order to address the multitude and diversity of secondary metabolites a large number of more than 180 analytes was targeted in settled dust and surface swab samples using liquid chromatography/mass spectrometry (LC/MS) based methodology. While 42%, 58% and 44% of all samples collected in Spanish, Dutch and Finnish schools, respectively, were positive for at least one of the metabolites analyzed, frequency of detection for the individual microbial secondary metabolites - with the exceptions of emodin, certain enniatins and physcion - was low, typically in the range of and below 10% of positive samples. In total, 30 different fungal and bacterial secondary metabolites were found in the samples. Some differences in the metabolite profiles were observed between countries and between index and reference school buildings. A major finding in this study was that settled dust derived from moisture damaged, damp schools contained larger numbers of microbial secondary metabolites at higher levels compared to respective dust samples from schools not affected by moisture damage and dampness. This observation was true for schools in each of the three countries, but became statistically significant only when combining schools from all countries and thus increasing the sample number in the statistical analyses.

High indoor microbial levels are associated with reduced Th1 cytokine secretion capacity in infancy

BACKGROUND

Exposure to microbes and their components may affect the maturation of the immune system. We examined the association of house dust microbial content with cytokine-producing capacity at birth and at the age of 1 year.

METHODS

Production of TNF-α, IFN-γ, IL-5, IL-8 and IL-10 at birth (n = 228) and at the age of 1 year (n = 200) following 24- and 48-hour whole-blood stimulation with staphylococcal enterotoxin B (SEB), lipopolysaccharide and the combination of phorbol ester and ionomycin was measured. Concentrations of ergosterol (marker for fungal biomass), muramic acid (marker for Gram-positive bacteria) and 3-hydroxy fatty acids with a carbon chain length from 10 to 14 (marker for Gram-negative bacteria) in living room floor dust were analyzed using gas chromatography-tandem mass spectrometry. Five single microbial species or groups were determined using a quantitative polymerase chain reaction method.

RESULTS

A high total level of the studied Gram-positive bacteria in general or Mycobacterium spp. in house dust was associated with decreased SEB-stimulated IFN-γ production, especially at the age of 1 year. The total level of indoor fungi analyzed (Penicillium spp., Aspergillus spp. and Paecilomyces variotii group, Trichoderma viride/atroviride/koningii,Wallemia sebi) was also inversely associated with IFN-γ production at the age of 1 year, but this association did not remain significant after adjustment for potential confounders. A few associations were found between microbial exposures and other measured cytokines.

CONCLUSIONS

High indoor microbial exposures may affect immune development in early life by reducing T helper type 1 cytokine secretion capacity. The observed hyporesponsiveness may reflect the adaptation of the immune system to environmental antigens. In future, more attention should be paid especially to the immunomodulatory role of exposures to Gram-positive bacteria.

Respiratory health and endotoxin: associations and modification by CD14/-260 genotype

Exposure to endotoxin has been associated with increased respiratory symptoms and decrements in lung function in occupational settings but little is known about the health effects of domestic exposure in adults. Here, we describe the association of respiratory disease, immunoglobulin (Ig)E sensitisation, bronchial reactivity and lung function with mattress endotoxin levels in adults, and determine whether these associations are modified by polymorphisms in CD14. Endotoxin levels in mattress dust from a population-based sample of 972 adults were measured. Associations were examined using generalised linear mixed models, adjusting for individual and household confounders. Effect modification of these associations by CD14/-260 (rs2569190) was assessed. Mattress endotoxin levels varied from 0.1 to 402.6 EU · mg(-1). Although there was no overall association of lung function with endotoxin exposure, there was evidence that the association of forced expiratory volume in 1 s and forced vital capacity with endotoxin was modified by CD14/-260 genotype (p-value for interaction 0.005 and 0.013, respectively). There was no evidence that symptoms, IgE sensitisation or bronchial reactivity were associated with mattress endotoxin levels. In this large epidemiological study of adults, there was no evidence that mattress endotoxin level was associated with respiratory symptoms or IgE sensitisation but the association of lung function with endotoxin levels may be modified by CD14 genotype.

Concentrations and diversity of microbes from four local bioaerosol emission sources in Finland

Microbial particles can readily be released into the air from different types of man-made sources such as waste operations. Microbiological emissions from different biological sources and their dispersion may be an issue of concern for area planning and for nearby residents. This study was designed to determine the concentrations and diversity of microbiological emissions from four different man-made source environments: waste center with composting windrows, sewage treatment plant, farming environment, and cattle manure spreading. Samples of airborne particles were collected onto polyvinyl chloride filters at three distances along the prevailing downwind direction, from each source environment during a period of approximately 1 week. These samples were analyzed for 13 species or assay groups of fungi, bacterial genus Streptomyces, and Gram-positive and -negative bacteria using quantitative polymerase chain reaction (PCR). Samples for determining the concentrations of viable fungi and bacteria were collected from all environments using a six-stage impactor. The results show that there were variations in the microbial diversity between the source environments. Specifically, composting was a major source for the fungal genera Aspergillus and Penicillium, particularly for Aspergillus fumigatus, and for the bacterial genus Streptomyces. Although the microbial concentrations in the sewage treatment plant area were significantly higher than those at 50 or 200 m distance from the plant area, in the farming environment or cattle manure spreading area, no significant difference was observed between different distances from the source. In summary, elevated concentrations of microbes that differ from background can only be detected within a few hundred meters from the source. This finding, reported earlier for culturable bacteria and fungi, could thus be confirmed using molecular methods that cover both culturable and nonculturable microbial material.

Molecular profiling of fungal communities in moisture damaged buildings before and after remediation--a comparison of culture-dependent and culture-independent methods

Background

Indoor microbial contamination due to excess moisture is an important contributor to human illness in both residential and occupational settings. However, the census of microorganisms in the indoor environment is limited by the use of selective, culture-based detection techniques. By using clone library sequencing of full-length internal transcribed spacer region combined with quantitative polymerase chain reaction (qPCR) for 69 fungal species or assay groups and cultivation, we have been able to generate a more comprehensive description of the total indoor mycoflora. Using this suite of methods, we assessed the impact of moisture damage on the fungal community composition of settled dust and building material samples (n = 8 and 16, correspondingly). Water-damaged buildings (n = 2) were examined pre- and post- remediation, and compared with undamaged reference buildings (n = 2).

Results

Culture-dependent and independent methods were consistent in the dominant fungal taxa in dust, but sequencing revealed a five to ten times higher diversity at the genus level than culture or qPCR. Previously unknown, verified fungal phylotypes were detected in dust, accounting for 12% of all diversity. Fungal diversity, especially within classes Dothideomycetes and Agaricomycetes tended to be higher in the water damaged buildings. Fungal phylotypes detected in building materials were present in dust samples, but their proportion of total fungi was similar for damaged and reference buildings. The quantitative correlation between clone library phylotype frequencies and qPCR counts was moderate (r = 0.59, p < 0.01).

Conclusions

We examined a small number of target buildings and found indications of elevated fungal diversity associated with water damage. Some of the fungi in dust were attributable to building growth, but more information on the material-associated communities is needed in order to understand the dynamics of microbial communities between building structures and dust. The sequencing-based method proved indispensable for describing the true fungal diversity in indoor environments. However, making conclusions concerning the effect of building conditions on building mycobiota using this methodology was complicated by the wide natural diversity in the dust samples, the incomplete knowledge of material-associated fungi fungi and the semiquantitative nature of sequencing based methods.

Co-occurrence of toxic bacterial and fungal secondary metabolites in moisture-damaged indoor environments

Toxic microbial secondary metabolites have been proposed to be related to adverse health effects observed in moisture-damaged buildings. Initial steps in assessing the actual risk include the characterization of the exposure. In our study, we applied a multi-analyte tandem mass spectrometry-based methodology on sample materials of severely moisture-damaged homes, aiming to qualitatively and quantitatively describe the variety of microbial metabolites occurring in building materials and different dust sample types. From 69 indoor samples, all were positive for at least one of the 186 analytes targeted and as many as 33 different microbial metabolites were found. For the first time, the presence of toxic bacterial metabolites and their co-occurrence with mycotoxins were shown for indoor samples. The bacterial compounds monactin, nonactin, staurosporin and valinomycin were exclusively detected in building materials from moist structures, while chloramphenicol was particularly prevalent in house dusts, including settled airborne dust. These bacterial metabolites are highly bioactive compounds produced by Streptomyces spp., a group of microbes that is considered a moisture damage indicator in indoor environments. We show that toxic bacterial metabolites need to be considered as being part of very complex and diverse microbial exposures in 'moldy' buildings.

PRACTICAL IMPLICATIONS

Bacterial toxins co-occur with mycotoxins in moisture-damaged indoor environments. These compounds are measurable also in settled airborne dust, indicating that inhalation exposure takes place. In attempts to characterize exposures to microbial metabolites not only mycotoxins but also bacterial metabolites have to be targeted by the analytical methods applied. We recommend including analysis of samples of outdoor air in the course of future indoor assessments, in an effort to better understand the outdoor contribution to the indoor presence of microbial toxins. There is a need for a sound risk assessment concerning the exposure to indoor microbial toxins at concentrations detectable in moisture-damaged indoor environments.

Determinants of stimulated peripheral blood cytokine production among farming women

Farming environment and environmental exposure to microbial agents have been suggested to promote favorable development of immune system in children and protect against allergic diseases. However, effects of farm exposure on adult immune responses are less clear. Aim of the present study was to examine associations of farm related factors and measured microbial exposure with stimulated production of interferon-gamma (IFN-γ) and interleukin-4 (IL-4) in peripheral blood samples among farming women. Whole peripheral blood samples were obtained from 112 women living on farms and stimulated with phorbol myristate acetate/ionomycin, lipopolysaccharide and staphylococcal enterotoxin B. Following 24h stimulation, protein levels of IFN-γ and IL-4 in the supernatants were measured by ELISA. From house dust, concentrations of 3-hydroxy fatty acids (C10:0-C14:0, marker for Gram-negative bacteria), muramic acid (Gram-positive bacteria) and ergosterol (fungal biomass) were analyzed with GC-MS/MS and viable microbes by culturing. Information on farm related factors and allergic diseases were collected from self-administered questionnaires. We found that household pets or other current or childhood farm-related factors had only few associations with stimulated cytokine production among studied farming women. Similarly, no strong associations were observed between markers of microbial exposure measured in house dust and cytokine levels. Atopic sensitization, allergic rhinitis and recent respiratory infections were, however, associated with reduced IFN-γ production. Our results suggest that the capacity of the studied environmental factors to modulate immune system is relatively weak in adulthood.

Odour annoyance and physical symptoms among residents living near waste treatment centres

Waste treatment processes produce odours and biological emissions to the environment, but their health effects are controversial. The aim of our study was to assess odour-associated self-reported physical symptoms among residents living near waste treatment centres. The study was conducted in the surroundings of five large-scale Finnish waste treatment centres with composting plants. In 2006, 1142 randomly selected residents living within 1.5, 3.0 and 5.0 km of these centres were interviewed by telephone. A questionnaire with 102 items asked about respondent's personal characteristics, odour exposure and symptoms during the preceding 12 months. Physical symptoms were analysed by distance to the waste treatment centre and by the respondent's perception and annoyance of waste treatment odour. The residents who were classified as "annoyed of the odour" reported following physical symptoms more than the others did: unusual shortness of breath (OR 1.5, 95% CI 1.0-2.2), eye irritation (1.5, 1.1-2.1), hoarseness/dry throat (1.5, 1.1-2.0), toothache (1.4, 1.0-2.1), unusual tiredness (1.5, 1.1-2.0), fever/shivering (1.7, 1.1-2.5), joint pain (1.5, 1.1-2.1) and muscular pain (1.5, 1.1-2.0). Moreover, the ORs for almost all other physical symptoms were elevated among the annoyed respondents. Reported odour annoyance near the waste treatment centres showed an association with many physical symptoms among residents living in the neighbouring areas.

Evaluating housing quality, health and safety using an Internet-based data collection and response system: a cross-sectional study

BACKGROUND

Typically housing and health surveys are not integrated together and therefore are not representative of population health or national housing stocks. In addition, the existing channels for distributing information about housing and health issues to the general public are limited. The aim of this study was to develop a data collection and response system that would allow us to assess the Finnish housing stock from the points of view of quality, health and safety, and also to provide a tool to distribute information about important housing health and safety issues.

METHODS

The data collection and response system was tested with a sample of 3000 adults (one per household), who were randomly selected from the Finnish Population Register Centre. Spatial information about the exact location of the residences (i.e. coordinates) was included in the database inquiry. People could participate either by completing and returning a paper questionnaire or by completing the same questionnaire via the Internet. The respondents did not receive any compensation for their time in completing the questionnaire.

RESULTS

This article describes the data collection and response system and presents the main results of the population-based testing of the system. A total of 1312 people (response rate 44%) answered the questionnaire, though only 80 answered via the Internet. A third of the respondents had indicated they wanted feedback. Albeit a majority (>90%) of the respondents reported being satisfied or quite satisfied with their residence, there were a number of prevalent housing issues identified that can be related to health and safety.

CONCLUSIONS

The collected database can be used to evaluate the quality of the housing stock in terms of occupant health and safety, and to model its association with occupant health and well-being. However, it must be noted that all the health outcomes gathered in this study are self-reported. A follow-up study is needed to evaluate whether the occupants acted on the feedback they received. Relying solely on an Internet-based questionnaire for collecting data would not appear to provide an adequate response rate for random population-based surveys at this point in time.

The effect of ozonization on furniture dust: microbial content and immunotoxicity in vitro

Moisture and mold problems in buildings contaminate also the furniture and other movable property. If cleaning of the contaminated furniture is neglected, it may continue to cause problems to the occupants even after the moisture-damage repairs. The aim of this study was to determine the effectiveness of high-efficiency ozone treatment in cleaning of the furniture from moisture-damaged buildings. In addition, the effectiveness of two cleaning methods was compared. Samples were vacuumed from the padded areas before and after the treatment. The microbial flora and concentrations in the dust sample were determined by quantitative cultivation and QPCR-methods. The immunotoxic potential of the dust samples was analyzed by measuring effects on cell viability and production of inflammatory mediators in vitro. Concentrations of viable microbes decreased significantly in most of the samples after cleaning. Cleaning with combined steam wash and ozonisation was more effective method than ozonising alone, but the difference was not statistically significant. Detection of fungal species with PCR showed a slight but nonsignificant decrease in concentrations after the cleaning. The immunotoxic potential of the collected dust decreased significantly in most of the samples. However, in a small subgroup of samples, increased concentrations of microbes and immunotoxicological activity were detected. This study shows that a transportable cleaning unit with high-efficiency ozonising is in most cases effective in decreasing the concentrations of viable microbes and immunotoxicological activity of the furniture dust. However, the method does not destroy or remove all fungal material present in the dust, as detected with QPCR analysis, and in some cases the cleaning procedure may increase the microbial concentrations and immunotoxicity of the dust.

Immunotoxicological properties of airborne particles at landfill, urban and rural sites and their relation to microbial concentrations

We investigated the immunotoxicological activity of airborne particles in three different environments during 11 months. Specifically, we analyzed the relation of the immunotoxicological activity to microbial concentrations. During the study period, samples from a landfill, an urban and a rural site were collected on filters once a month. The immunotoxicological characteristics of collected particle samples were studied by exposing mouse macrophages (RAW264.7), and measuring the viability and production of inflammatory mediators i.e. nitric oxide (NO), tumor necrosis factor (TNF)-alpha and interleukin (IL)-6 after 24 hours. In addition, the results were compared to corresponding microbial concentrations measured with quantitative polymerase chain reaction (qPCR) in the same sites. The particles collected from the landfill caused significantly more toxicity and inflammatory responses than the particles from other sites. The immunotoxicological activity of the samples changed according to the season, being the lowest in all study sites in the winter. In the rural and urban sites the responses peaked during the spring, whereas at the landfill the highest responses were detected towards the fall. All immunotoxic responses correlated strongly with airborne microbial concentrations at the landfill, whereas on the other sites the correlations were weaker. These results indicate that the overall immunotoxicological activity of the particles is increased in waste handling area with a heavy microbial load. The activity of the samples collected from different sites changes according to the season being at their lowest at wintertime. At the waste center, the immunotoxicological responses are related with concentrations of microbes, whereas at rural area and city center other factors seem to govern the toxicity of the sample.

Odor annoyance near waste treatment centers: a population-based study in Finland

Decomposition of biodegradable waste in municipal waste centers may produce odor emissions and subsequently cause discomfort to nearby residents. The public health importance of the resulting nuisance has not been sufficiently characterized. The aim of this study was to study the perception and annoyance of waste odor among residents in relation to distance from the large-scale source. In 2006, 1142 randomly selected residents living within 5 km from the boundaries of five waste treatment centers were interviewed by telephone. These centers were landfilling municipal waste and composting source-separated biowaste and/or sludge. The questionnaire consisted of 102 items containing questions on perceived environmental nuisance. Odds ratios (ORs) and confidence intervals (CIs) were calculated adjusting for sex and age. The proportion of respondents perceiving odor varied by center and distance (< 1.5 km: 66-100%; 1.5 to < 3 km: 13-84%; 3 to < 5 km: 2-64%). The pooled OR for odor annoyance was 6.1 (95% CI 3.7-10) in the intermediate and 19 (95% CI 12-32) in the innermost zone compared with residents in the outermost zone. Intensity of odor characterized as very strong or fairly strong affected odor annoyance more than weekly or more frequently perceived odor. The high level of odor perception and annoyance in residents living near waste treatment centers draws attention to the need to prevent odor nuisance constricting emission peaks and frequent emissions. Because odors may affect fairly distant (even 1.5 to < 3 km) residential areas, planning of the locations of waste treatment operations is essential.

The occupant as a source of house dust bacteria

BACKGROUND

Markers for microbial groups are commonly measured in house dust samples to assess indoor exposure to microbes in studies on asthma and allergy. However, little is known about the sources of different microbes. A better understanding of the nature and origin of microbes present in the immediate environment of human beings is crucial if one wants to elucidate protective as well as adverse effects on human health.

OBJECTIVE

To determine the extent to which the bacterial composition of mattress and floor dust reflects the presence of the human body in relation to other environmental sources.

METHODS

House dust and skin surface swab samples of occupants in 4 homes were collected and analyzed for their bacterial content, using a culture-independent methodology. Bacterial sequences analyzed from the different house dusts and skin surface swabs represented random samples of bacteria present in a given sample. Highly similar sequences were grouped to assess biodiversity and to draw conclusions about the sources of bacteria.

RESULTS

The bacterial flora in the house dust samples was found to be highly diverse and dominated by gram-positive bacteria. To a considerable extent, the presence of different bacterial groups was attributed to human sources. In the individuals' mattress dust samples, 69% to 88% of the bacterial sequences analyzed were associated with human origins. The respective percentages for the individual floor dusts ranged from 45% to 55%.

CONCLUSION

Our study indicates that human-derived bacteria account for a large part of the mainly gram-positive bacterial content in house dust.

Confirmed moisture damage at home, respiratory symptoms and atopy in early life: a birth-cohort study

OBJECTIVES

Most previous studies on the association between moisture or mold problems in the home and respiratory symptoms in children were cross-sectional and based on self-reported exposure. The aim of this study was to evaluate the impact of objectively observed moisture damage and visible mold in the homes on early-life respiratory morbidity and atopic sensitization in a birth cohort.

METHODS

Building inspection was performed by building engineers in the homes of 396 children, and the children were followed up with questionnaires from birth to the age of 18 months. Specific immunoglobulin E levels were measured at the age of 1 year.

RESULTS

Doctor-diagnosed wheezing was associated with the severity of moisture damage in the kitchen and with visible mold in the main living area and especially in the bedroom of the child. The risk for parent-reported wheezing apart from cold increased with the severity of moisture damage in the kitchen. Moisture damage in the bathrooms or other interior spaces had no significant association with wheezing. No significant associations were observed for other end points, such as cough, or respiratory infections. There was a suggestion for an increased risk for sensitization to cat dander linked with moisture and mold exposure.

CONCLUSIONS

This birth-cohort study supports previous observations that moisture mold problems in the kitchen and in the main living area increase the risk for wheezing in early childhood. The results underline the importance of assessing separately the health effects of moisture and mold problems in different areas of the home.

Microbial content of house dust samples determined with qPCR

This study was designed to produce information about microbial concentrations using qPCR and their variation in different seasons and home environments with analyses of two types of house dust samples. Also the correlations between the two types of samples and the reproducibility of the parallel subsamples were studied. Two types of vacuumed house dust samples, rug dust and vacuum cleaner bag dust, were collected in 5 normal urban homes in four different seasons (N=20+20). From all dust samples, five parallel subsamples were subjected to qPCR analyses of 17 microbial species or assay groups of microbes. The highest fungal concentrations were found for the Penicillium/Aspergillus/Paecilomyces variotii group, and for the species Aspergillus penicillioides, Aureobasidium pullulans, Cladosporium cladosporioides and Cladosporium herbarum. These species/groups were present in almost all samples. The two types of dust samples gave similar results for most microbial species or groups analyzed, but in general, concentrations were slightly higher in rug dust than in dust from vacuum cleaner bag. Microbial concentrations varied significantly between different seasons and hence the similarity of samples within home was mainly low. The concentrations varied significantly also between different home environments. The reproducibility of the parallel subsamples was good or moderate for most of the analyzed species or assay groups. However, further studies are needed to fully understand the factors causing variation in these methods. Nevertheless, in order to show actual differences in fungal concentrations between urban homes with no known microbial sources, all dust samples to be compared should be taken during the same season.

Survival of amoebae on building materials

Moisture damage and concurrent microbial growth in buildings are associated with adverse health effects among the occupants. However, the causal agents for the symptoms are unclear although microbes are assumed to play a major role. Fungi and bacteria are not the only microbes inhabiting moist building materials; it was recently revealed that amoebae are also present. As amoebae have the potential to harbor many pathogens and to modulate the characteristics of growing microbes, a better appreciation of the growth and survival of amoebae in moisture damage conditions will add to the understanding of their effects on health outcomes. In this study, we investigated the ability of amoebae to survive on six building materials. Furthermore, both aged and unused materials were tested. Amoebae survived on gypsum board and mineral wool for the whole 2 months experiment even without additional sustenance. When sustenance (heat-killed bacteria) was available, aged pine wood and birch wood also allowed their survival. In contrast, amoebae were quickly killed on fresh pine wood and they did not survive on concrete or linoleum. In conclusion, our data show that amoebae can persist on several common building materials once these materials become wet.

PRACTICAL IMPLICATIONS

Amoebae are able to survive on many building materials should the materials become wet. Amoebae have the potential to increase growth, cytotoxicity, and pathogenicity of other microbes present in moisture damages, and they may carry potentially pathogenic bacteria as endosymbionts and thus introduce them into the indoor air. Therefore, amoebae may have a prominent role in the microbial exposures occurring in moisture-damaged buildings. The presence of amoebae could be usefully included in reporting the microbial damage of material samples.

Evaluation of quantitative PCR and culture methods for detection of house dust fungi and streptomycetes in relation to moisture damage of the house

AIMS

Microbial concentrations in vacuumed house dust samples (n = 71) were analysed by culture and quantitative polymerase chain reaction (qPCR) methods and their association with extent of moisture damage in the house was studied.

METHODS AND RESULTS

Microbial concentrations measured by qPCR correlated with concentrations obtained by culture method, but were orders of magnitude higher. qPCR also had better sensitivity. Concentrations of several microbes in house dust, determined with qPCR, were associated with the extent of moisture damage in the house. This association was strongest for Penicillium brevicompactum, one of the fungi detected in highest concentrations by qPCR. Furthermore, house dust concentrations of Wallemia sebi, Trichoderma viride, Cladosporium sphaerospermum, Eurotium amstelodami and the combined assay group for Penicillium spp., Aspergillus spp. and Paecilomyces variotii were significantly associated with the extent of the moisture damage.

CONCLUSION

These species or assay groups could probably be used as indicators of moisture damage in the house.

SIGNIFICANCE AND IMPACT OF THE STUDY

This finding indicates the benefits of the qPCR method, which is sensitive enough to reveal the differences in microbial concentrations of house dust between moisture-damaged and undamaged houses.

Predominance of Gram-positive bacteria in house dust in the low-allergy risk Russian Karelia

Simple living conditions and farming environment have been associated with reduced risk for allergic diseases such as atopy and asthma but the factors responsible for this effect remain unresolved. We examined the bacterial composition of house dusts obtained from Finnish and Russian Karelia, two adjacent areas with high and low occurrence of atopic diseases respectively. Two dust mixes, both composed of 10 randomly selected dust samples from 349 Finnish and 417 Russian Karelian households were studied for bacterial biomarkers (DNA, Limulus-active endotoxin, 3-OH fatty acids, muramic acid) and for 16S rRNA gene sequences. Overall, the DNA cloning revealed more taxons (94 different genera) of dustborne bacteria than seen in any previous study on residential environments. Majority (67%) of the bacterial DNA clones in house dust from the low-allergy Russian Kareliarepresented Gram-positive bacteria (Firmicutes and Actinobacteria), predominantly Staphylococcaceae and Corynebacteriaceae. Russian Karelian dust showed up to 20-fold higher contents of muramic acid (marker of Gram-positive bacteria) and a sevenfold higher number of clones of animal-associated species, whereas in Finnish Karelian dust Gram-negatives (mainly Proteobacteria) predominated. Clones of plant-associated bacterial species and of chloroplast, indicating plant biomass, were more numerous in Finnish than in Russian Karelian dust. In conclusion, this study revealed major disparities between Finnish and Russian house dusts. The higher bacterial content and the predominance of Gram-positive bacteria in Russian dust may have implications for occurrence of atopy.

Monitoring success of remediation: seven case studies of moisture and mold damaged buildings

Based on seven case studies of buildings that underwent different degrees of moisture and mold damage remediation, we aimed to develop methodology for assessment of the success of the remediation process. Methods used in gauging the success included technical monitoring of performance of building structures and heating, ventilation and air conditioning (HVAC) systems, microbial monitoring of indoor air quality (IAQ), and health effects studies of building occupants. The assessment was based on measurable change in the situations before and after remediation. Based on technical monitoring, remediation was successful in three cases, with partial improvement noted in three cases, whereas no remediation was conducted in one case. Based on microbial monitoring, improvement was detected in one, partial improvement in two and no improvement in two cases, whereas no follow-up was conducted in two cases. Health effect studies (mainly self-reported health status) showed improvement in one case, partial improvement in two cases, and no improvement in two cases, whereas no follow-up was conducted in one case, and in one case, follow-up failed due to low response rate. The results illustrate that it is possible to monitor the effects of remediation using various metrics. However, in some cases, no improvement could be observed in IAQ or occupant health, even if the remediation was considered technically successful, i.e. the remediation was fully completed as recommended. This could be due to many reasons, including: 1) all damage may not have been addressed adequately; 2) IAQ or health may not have been perceived improved regardless of remediation; and/or 3) the methods used may not have been sensitive/specific enough to detect such improvement within the 6-12 months follow-up periods after completion of the remediation. There is a need to further develop tools for monitoring and assessment of the success of moisture damage remediation in buildings.

Indoor air particles and bioaerosols before and after renovation of moisture-damaged buildings: the effect on biological activity and microbial flora

Many building-related health problems coincide with moisture damage and mold growth within a building. Their elimination is assumed to improve indoor air quality. The aim of this study was to follow the success of remediation in two individual buildings by analyzing the microbial flora and immunotoxicological activity of filter samples. We compare results from samples collected from indoor air in the moisture-damaged buildings before and after renovation and results from matched reference buildings and outdoor air. The microbial characteristics of the samples were studied by analyzing ergosterol content and determining the composition of fungal flora with quantitative polymerase chain reaction (QPCR). In addition, the concentrations of particles were monitored with optical particle counter (OPC). The immunotoxicological activity of collected particle samples was tested by exposing mouse macrophages (RAW264.7) for 24 h to particle suspension extracted from the filters, and measuring the viability of the exposed cells (MTT-test) and production of inflammatory mediators (nitric oxide, IL-6 and TNF*) in cell culture medium by enzyme-linked immunoassay (ELISA). The results show that for Location 1 the renovation decreased the immunotoxicological activity of the particles collected from damaged building, whereas no difference was detected in the corresponding samples collected from the reference building. Interestingly, only slight differences were seen in the concentration of fungi. In the Location 2, a decrease was seen in the concentration of fungi after the renovation, whereas no effect on the immunotoxicological responses was detected. In this case, the immunotoxicological responses to the indoor air samples were almost identical to those caused by the samples from outdoor air. This indicates that the effects of remediation on the indoor air quality may not necessarily be readily measurable either with microbial or toxicological parameters. This may be associated with different spectrum of harmful agents in different mold and moisture-damaged buildings.

Diversity and seasonal dynamics of bacterial community in indoor environment

Background

We spend most of our lives in indoor environments and are exposed to microbes present in these environments. Hence, knowledge about this exposure is important for understanding how it impacts on human health. However, the bacterial flora in indoor environments has been only fragmentarily explored and mostly using culture methods. The application of molecular methods previously utilised in other environments has resulted in a substantial increase in our awareness of microbial diversity.

Results

The composition and dynamics of indoor dust bacterial flora were investigated in two buildings over a period of one year. Four samples were taken in each building, corresponding to the four seasons, and 16S rDNA libraries were constructed. A total of 893 clones were analysed and 283 distinct operational taxonomic units (OTUs) detected among them using 97% sequence similarity as the criterion. All libraries were dominated by Gram-positive sequences, with the most abundant phylum being Firmicutes. Four OTUs having high similarity to Corynebacterium-, Propionibacterium-, Streptococcus- and Staphylococcus- sequences were present in all samples. The most abundant of the Gram-negative OTUs were members of the family Sphingomonadaceae, followed by Oxalobacteraceae, Comamonadaceae, Neisseriaceae and Rhizobiaceae.

The relative abundance of alpha- and betaproteobacteria increased slightly towards summer at the expense of firmicutes. The proportion of firmicutes and gammaproteobacteria of the total diversity was highest in winter and that of actinobacteria, alpha- and betaproteobacteria in spring or summer, whereas the diversity of bacteroidetes peaked in fall. A statistical comparison of the libraries revealed that the bacterial flora of the two buildings differed during all seasons except spring, but differences between seasons within one building were not that clear, indicating that differences between the buildings were greater than the differences between seasons.

Conclusion

This work demonstrated that the bacterial flora of indoor dust is complex and dominated by Gram-positive species. The dominant phylotypes most probably originated from users of the building. Seasonal variation was observed as proportional changes of the phyla and at the species level. The microflora of the two buildings investigated differed statistically and differences between the buildings were more pronounced than differences between seasons.

Comparison of mold concentrations quantified by MSQPCR in indoor and outdoor air sampled simultaneously

Mold specific quantitative PCR (MSQPCR) was used to measure the concentrations of the 36 mold species in indoor and outdoor air samples that were taken simultaneously for 48 h in and around 17 homes in Cincinnati, Ohio. The total spore concentrations of 353 per m(3) of indoor air and 827 per m(3) of outdoor air samples were significantly different (p<or=0.05). However, only the concentrations of Aspergillus penicillioides, Cladosporium cladosporioides types 1 and 2 and Cladosporium herbarum were correlated in indoor and outdoor air samples (p-value<or=0.05 and sufficient data for estimate and absolute value rho estimate >or=0.5). These results suggest that interpretation of the meaning of short-term (<48 h) mold measurements in indoor and outdoor air samples must be made with caution.

Effects of co-culture of amoebae with indoor microbes on their cytotoxic and proinflammatory potential

Free-living amoebae are ubiquitous environmental protozoa found in both natural and man-made environments, including moisture-damaged buildings. Furthermore, the interaction between amoebae and bacteria has been shown to enhance the virulence and pathogenicity of some bacteria. While the inhabitants of moisture damaged buildings are known to be at risk of suffering adverse health effects, the exact causative agents and mechanisms are still obscure. To examine the possible role of amoebae in the health effects associated with moisture damages, the effects of amoebae on the cytotoxicity and proinflammatory potential of nonpathogenic microbes common in moisture-damaged buildings were investigated. First, two bacterial and three fungal strains were cultured both individually and in coculture with Acanthamoeba polyphaga. Then, mouse RAW264.7 macrophages were exposed to the cocultures as well as the individually grown bacteria, fungi, and amoebae. Finally, cell viability and production of proinflammatory mediators, i.e., nitric oxide (NO), tumor necrosis factor alpha (TNF-alpha), and interleukin 6 (IL-6), were measured in macrophages after the exposure. The results revealed that cocultivation with amoebae increased the cytotoxicity of the bacterium Streptomyces californicus and the fungus Penicillium spinulosum. Moreover, the macrophages produced up to 10 times higher concentrations of NO after the exposure to these cocultures than after the exposure to individually grown microbes. Finally, the production of the cytokines was up to two orders of magnitude higher (IL-6) and up to four times higher (TNF-alpha) after exposure to the cocultures when compared to individually grown microbes. We conclude that amoebae are able to potentiate the cytotoxicity and proinflammatory properties of certain microbes associated with moisture damages.

Elements that contribute to healthy building design

BACKGROUND

The elements that contribute to a healthy building are multifactorial and can be discussed from different perspectives.

OBJECTIVES

WE PRESENT THREE VIEWPOINTS OF DESIGNING A HEALTHY BUILDING: the importance of sustainable development, the role of occupants for ensuring indoor air quality, and ongoing developments related to indoor finishes with low chemical emissions and good fungal resistance.

DISCUSSION

Sustainable design rediscovers the social, environmental, and technical values of pedestrian and mixed-use communities, using existing infrastructures including "main streets" and small-town planning principles and recapturing indoor-outdoor relationships. This type of design introduces nonpolluting materials and assemblies with lower energy requirements and higher durability and recyclability. Building occupants play a major role in maintaining healthy indoor environments, especially in residences. Contributors to indoor air quality include cleaning habits and other behaviors; consumer products, furnishings, and appliances purchases, as well as where and how the occupants use them. Certification of consumer products and building materials as low-emitting products is a primary control measure for achieving good indoor air quality. Key products in this respect are office furniture, flooring, paints and coatings, adhesives and sealants, wall coverings, wood products, textiles, insulation, and cleaning products. Finishing materials play a major role in the quality of indoor air as related to moisture retention and mold growth.

CONCLUSIONS

Sustainable design emphasizes the needs of infrastructure, lower energy consumption, durability, and recyclability. To ensure good indoor air quality, the product development for household use should aim to reduce material susceptibility to contaminants such as mold and should adopt consumer-oriented product labeling.

Personal and microenvironmental concentrations of particles and microbial aerosol in relation to health symptoms among teachers

A total of 81 randomly selected elementary school teachers participated in two sampling campaigns conducted 2 weeks apart during the winter. A 24-h sample collection was performed using personal and microenvironmental sampling from homes, and an 8-h sample collection was performed from workplaces of the studied subjects. Filters were analyzed for particle mass, absorption coefficient of the filter, and for both total and viable microorganisms. Comprehensive questionnaire responses were collected from the teachers concerning weekly occurred symptoms during the previous 12-month period, and they filled in symptom diaries immediately after each sampling campaign concerning symptoms during the previous 24-h and 7-day periods. The effect of different recall periods on agreement between questionnaire responses was assessed. Factor analysis was used in order to identify factors explaining the pattern of correlations within the personal, home, and work measurements. Moreover, associations between personal, home, and work measurements of pollutants and symptoms were analyzed using general estimation equations. The recall period of 7 days seemed to provide the most reliable data for the health effect assessment. Information from the factor analysis may allow reduction of variables related to the exposure assessment, and better interpretation of results. Both personal exposure and concentrations of pollutants at home were more frequently associated with health symptoms than concentrations at work. In multipollutant analyses, absorbance coefficient was positively associated with eye symptoms, and total bacteria with both cough and blocked nose.

Effects of moisture damage and renovation on microbial conditions and pupils' health in two schools--a longitudinal analysis of five years

Airborne microbes and pupils' symptoms were monitored in a moisture-damaged (index) school and a reference school for five consecutive years. These surveys were carried out in two separate years before the renovation of the index school, during the renovation, and one and two years after the renovation. Microbial concentrations were higher in the index school than those in the reference school before and during renovation, but afterwards, the levels decreased to the level of the reference school. The effect of remediation was seen as an altered mycobiota in the index school. Year-to-year variation of microbial concentrations, probably due to climatic factors, caused a peak in both schools but their difference remained. Several symptoms were more prevalent in the moisture-damaged school than in the reference school, but the differences disappeared during the renovations. These results emphasize the importance of using a reference building in assessing the microbial conditions of a moisture damaged building. Furthermore, microbial concentrations reflected well the technical condition of the construction, but the reported symptoms of the occupants did not strictly follow the timely fluctuation in microbial conditions.

Skin test reactivity to molds in pre-school children with newly diagnosed asthma

BACKGROUND

The aim of the present study was to evaluate the prevalence of sensitization to molds and to house dust mites (HDM) in pre-school children with newly-diagnosed asthma.

METHODS

From 1996 to 2000, 122 children 1 to 6 years of age with fresh asthma treated in the Kuopio University Hospital, Kuopio, Finland, were recruited in the study; 94% attended. Skin prick tests were performed to common inhalant allergens and to 10 molds. The homes were surveyed for moisture damage.

RESULTS

A majority of the houses had signs of dampness and moisture. One-third of the children reacted to inhalant allergens. There were 11 positive reactions to molds in five children who all reacted to at least one animal dander or seasonal pollen. Aspergillus fumigatus, Botrytis cinerea, and Cladosporium herbarum were the most common mold allergens. There were only two children with positive reactions to HDM, and none of them reacted to molds. No associations were found between the presence or degree of moisture problems at home and mold or HDM allergy.

CONCLUSION

Sensitization to molds seems to play only a minor role in pre-school children with newly-diagnosed asthma in a northern climate where the incidences of mold and HDM allergies are rather low.

A preliminary study on the association between ventilation rates in classrooms and student performance

Poor conditions leading to substandard indoor air quality (IAQ) in classrooms have been frequently cited in the literature over the past two decades. However, there is limited data linking poor IAQ in the classrooms to student performance. Whereas, it is assumed that poor IAQ results in reduced attendance and learning potential, and subsequent poor student performance, validating this hypothesis presents a challenge in today's school environment. This study explores the association between student performance on standardized aptitude tests that are administered to students on a yearly basis, to classroom carbon dioxide (CO2) concentrations, which provide a surrogate of ventilation being provided to each room. Data on classroom CO2 concentrations (over a 4-5 h time span within a typical school day) were recorded in fifth grade classrooms in 54 elementary schools within a school district in the USA. Results from this preliminary study yield a significant (P < 0.10) association between classroom-level ventilation rate and test results in math. They also indicate that non-linear effects may need to be considered for better representation of the association. A larger sample size is required in order to draw more definitive conclusions. Practical Implications Future studies could focus on (1) gathering more evidence on the possible association between classroom ventilation rates and students' academic performance; (2) the linear/non-linear nature of the association; and (3) whether it is possible to detect 'no observed adverse effect level' for adequate ventilation with respect to academic performance in schools. All of this information could be used to improve guidance and take regulatory actions to ensure adequate ventilation in schools. The high prevalence of low ventilation rates, combined with the growing evidence of the positive impact that sufficient ventilation has on human performance, suggests an opportunity for improving design and management of school facilities.

Moisture damage and childhood asthma: a population-based incident case-control study

Most previous studies on the association between moisture damage and asthma have been cross-sectional and relied on self-reported exposure and health. The present authors studied the association by carrying out careful home inspections among new, clinically determined cases of asthma and controls. New cases of asthma aged 12-84 months (n = 121) were recruited prospectively and matched for year of birth, sex and living area with two randomly selected population controls (n = 241). Trained engineers visited all homes. Both cases and controls had lived >or=75% of their lifetime or the past 2 yrs in their current home. Risk of asthma increased with severity of moisture damage and presence of visible mould in the main living quarters but not in other areas of the house. Cases more often had damage in their bedroom. Associations were comparable for atopic and nonatopic asthma and for children aged >30 months or <or=30 months. The present results, using standardised assessment of exposure and asthma, suggest that moisture damage and mould growth in the main living quarters are associated with the development of asthma in early childhood.

Mycobacteria and fungi in moisture-damaged building materials

In contrast to the growth of fungi, the growth of mycobacteria in moisture-damaged building materials has rarely been studied. Environmental mycobacteria were isolated from 23% of samples of moisture-damaged materials (n = 88). The occurrence of mycobacteria increased with increasing concentrations of fungi. Mycobacteria may contribute to indoor exposure and associated adverse health effects.

Characterizing microbial exposure with ergosterol, 3-hydroxy fatty acids, and viable microbes in house dust: determinants and association with childhood asthma

The authors assessed determinants of ergosterol, 3-OH fatty acids (FAs), and viable microbes in vacuum cleaner dust, and investigated the association between these microbial markers and childhood asthma. The authors studied the homes of 36 children who were new cases of childhood asthma and the homes of 36 controls. Home characteristics explained 34% to 44% of the variation in levels of different microbial groups. Determinants of 3-OH FAs were a lower level of cleanliness, having a fireplace, having livestock, and moisture damage; determinants of viable bacteria were the level of home repair needed and the material used in the building frame of the home. Ergosterol was associated with the presence of livestock and the practice of cleaning rugs outside; viable fungi was associated with the material used in the building frame, visible mold, and the practice of cleaning rugs outside. Exposure to mesophilic actinomycetes was nonsignificantly associated with risk of asthma. The authors concluded that the variation of microbial levels in dust could be explained relatively well by home characteristics, and suggested that exposure to mesophilic actinomycetes may increase the risk of new asthma.

Simkania negevensis and newly diagnosed asthma: a case-control study in 1- to 6-year-old children

BACKGROUND

Simkania negevensis is an intracellular bacterium, sharing many characteristics with Chlamydophila and Chlamydia species. S. negevensis infection has been associated with bronchiolitis in infants and with pneumonia and exacerbations of COPD in adults.

OBJECTIVE

The aim of the present study was to evaluate, in a case-control setting, whether S. negevensis serology had any association with the onset of asthma in children.

METHODS

S. negevensis-specific IgM, IgA and IgG antibodies were measured by microimmunofluorescence in 104 children below school-age with newly diagnosed asthma, and in 122 control children.

RESULTS

S. negevensis-specific IgM was detected in two (2%) cases and in nine (8%) of the controls. IgG was detected in 12 (12%) cases and 12 (10%) of the controls. IgA antibodies were absent in all children. The age distribution of the 35 children with S. negevensis-specific antibodies was even, the positivity rate being 11% in the 12- to 23-month-old group and 20-23% in the children aged between 2 and 5 years.

CONCLUSION

Although S. negevensis appears to cause infections in the Finnish preschool-aged population, there was no association with asthma.

Children's homes--determinants of moisture damage and asthma in Finnish residences

Certain housing characteristics increase the risk for moisture damage, which has been associated with increased risk for asthma in children. Modeling moisture damage as a function of these characteristics could therefore provide a simple tool to estimate building-related risk for asthma. This study aimed to find out specific associations between asthma case-control status of children and moisture damage and housing characteristics. The data consisted of information on 121 asthmatic children and predominately two age-, gender- and place of residence-matched control children for every case, and information on moisture damage and housing characteristics in the homes of the children. In a previous study, we found a statistically significant association between moisture damage observations in main living areas and asthma in children. Using logistic regression, five models were formulated to predict moisture damage status of the homes and moisture damage status of living areas. The models were able to classify the damage status correctly in 65.0-87.7% of the homes (kappa values 0.10-0.47) as functions of housing characteristics. None of the models qualified as a significant determinant of the case-control status of the children.

PRACTICAL IMPLICATIONS

It can be hypothesized that building-related risk for asthma could be roughly estimated using models predicting moisture damage status of buildings as a function of easily obtainable housing characteristics. The results of this study indicated that, with a moderate certainty, it is possible to model moisture damage status of buildings using housing characteristics. However, the models developed did not associate with asthma in children. In conclusion, it was not possible to estimate the risk for asthma by studying housing characteristics only, but detailed information on moisture damage (e.g. location of damage) was crucial for such estimation.

Effects of amoebae on the growth of microbes isolated from moisture-damaged buildings

Dampness, moisture, and mold in buildings are associated with adverse health outcomes. In addition to fungi and bacteria, amoebae have been found in moisture-damaged building materials. Amoebae and a growing list of bacteria have been shown to have mutual effects on each other's growth, but the interactions between amoebae and microbes common in moisture-damaged buildings have not been reported. We co-cultivated the amoeba Acanthamoeba polyphaga with bacteria and fungi isolated from moisture-damaged buildings in laboratory conditions for up to 28 days. The microbes selected were the bacteria Streptomyces californicus, Bacillus cereus, and Pseudomonas fluorescens, and the fungi Stachybotrys chartarum, Aspergillus versicolor, and Penicillium spinulosum. Fungi and bacteria generally benefited from the presence of the amoebae, whereas the growth of amoebae was hindered by Streptomyces californicus, Stachybotrys chartarum, and Bacillus cereus. Pseudomonas fluorescens slightly enhanced amoebae viability. Amoebae were indifferent to the presence of Aspergillus versicolor and Penicillium spinulosum. Thus, our results show that amoebae can alter the survival and growth of some microbes in moisture-damaged buildings.Key words: moisture-damaged buildings, free-living amoebae, bacteria, fungi, co-culture.

Dust sampling methods for endotoxin - an essential, but underestimated issue

Exposure to farming environment in early life has been associated with lower risk for allergic diseases possibly caused by increased exposure to endotoxin. The aims of this study were to compare the reproducibility of different sampling methods for endotoxin, and to determine whether environmental characteristics have different effect on endotoxin levels of different sample types. The reproducibility of sampling methods (bed dust, floor dust, vacuum cleaner dust bag dust, settled dust and air samples) was studied with repeated sampling (five visits during 1 year) in five farming and five urban homes. To examine determinants of endotoxin for different types of dust sample, sampling was conducted once in 12 farming and 17 urban homes. Endotoxin was analyzed using Limulus Amebocyte Lysate assay. Bed dust samples had the best reproducibility (intraclass correlation, ICC=66%), but the difference between farming and non-farming homes was not clear with this sample type. The reproducibility of floor (ICC=52%) and settled dust (ICC=51%) was moderate. With these sample types the difference between farming and non-farming homes was clear. Settled dust had some seasonal variation. Based on this study, the best compromise for sampling for endotoxin appears to be floor dust sample followed by bed and settled dust samples. Practical Implications Endotoxins have been widely measured, even though the validity of different sample types to reflect the endotoxin exposure level of an indoor environment is poorly known. This study shows that bed dust samples have the best reproducibility, but they do not reflect the differences in exposure due to environmental factors such as farming. Floor dust samples with moderate reproducibility may be the best choice for sampling of endotoxin in large field studies.