The IVAIRE project--a randomized controlled study of the impact of ventilation on indoor air quality and the respiratory symptoms of asthmatic children in single family homes.

UNLABELLED: A randomized controlled trial was carried out to measure the impact of an intervention on ventilation, indoor air contaminants, and asthma symptoms of children. Eighty-three asthmatic children living in low-ventilated homes were followed over 2 years. Several environmental parameters were measured during the summer, fall, and winter. The children were randomized after Year 1 (43 Intervention; 40 Control). The intervention included the installation of either a Heat Recovery Ventilator (HRV) or Energy Recovery Ventilator (ERV). During the fall and winter seasons, there was a significant increase in the mean ventilation rate in the homes of the intervention group. A statistically significant reduction in mean formaldehyde, airborne mold spores, toluene, styrene, limonene, and α-pinene concentrations was observed in the intervention group. There was no significant group difference in change in the number of days with symptoms per 14 days. However, there was a significant decrease in the proportion of children who experienced any wheezing (≥1 episode) and those with ≥4 episodes in the 12-month period in the intervention group. This study indicates that improved ventilation reduces air contaminants and may prevent wheezing. Due to lack of power, a bigger study is needed. PRACTICAL IMPLICATIONS: Positive findings from this study include the fact that, upon recruitment, most of the single family homes with asthmatic children were already equipped with a mechanical ventilation system and had relatively good indoor air quality. However, the 8-h indoor guideline for formaldehyde (50 µg/m3) was frequently exceeded and the ventilation rates were low in most of the homes, even those with a ventilation system. Both ERVs and HRVs were equally effective at increasing air exchange rates above 0.30 ACH and at preventing formaldehyde concentrations from exceeding the 50 µg/m3 guideline during the fall and winter seasons. Furthermore, the ERVs were effective at preventing excessively low relative humidities in the homes. Based on observed difference of risk, intervention to increase ventilation in five sample homes and children would prevent 1 home to exceed the indoor air long-term formaldehyde guideline and prevent 1 asthmatic child experiencing at least one episode of wheezing over a year.

Maintaining health by balancing microbial exposure and prevention of infection: the hygiene hypothesis versus the hypothesis of early immune challenge.

The human immune system is inseparably bonded to an individual's personal micro-biome from birth to death. Since the beginning of life, commensal relationships have ensured the survival of micro- and macro-organisms within complex relationships. However, technological advances and altered lifestyle imposed new rules for this interaction during recent decades. It has been observed that reduced exposure to micro-organisms and parasites results in decreased morbidity and mortality, but is also associated with a rising prevalence of atopic disorders and autoimmune diseases, mostly in industrialized countries. This inverse relationship is described by the 'hygiene hypothesis', put forward in 1989, yet this term only imperfectly describes these observations, as excessive hygiene or hygienic measures may not directly be the central cause. The lack of appropriate immune stimulation during early childhood with the consequence of disturbed alignment in the sequence of encountering self- or non-self-antigens might account in the rise of atopy and autoimmune disease. For this reason we propose the term 'early immune challenge hypothesis'. This concept highlights the importance of immune priming in early life in the context of genetic, social, geographic, cultural, and economic background. Moreover, it emphasizes the central role of 'training' of regulatory T-cells through sufficient microbial exposure, leading to a robust, healthy balance between inflammation and anti-inflammation or immune tolerance. Insufficient exposure might result in abnormal immune regulatory development. Finally, it incorporates the idea of encountering 'old friends' - organisms that shaped our immune system during human phylogeny. This article gives a comprehensive overview of the relationship between microbial exposure, and the incidence of asthma and hay fever is outlined. Although the outcomes of these studies originally were interpreted in the framework of the hygiene hypothesis, they may suit the concept of the hypothesis of early immune challenge even better. Moreover, recent studies have revealed that TH or TReg imbalances in disease may be partially corrected by the administration of helminthic or bacterial extracts.

Microbial volatile organic compounds in the air of moldy and mold-free indoor environments.

UNLABELLED: A single-blinded study was performed to analyze whether indoor environments with and without mold infestation differ significantly in microbial volatile organic compounds (MVOC) concentrations. Air sampling for MVOC was performed in 40 dwellings with evident mold damage and in 44 dwellings, where mold damage was excluded after a thorough investigation. The characteristics of the dwellings, climatic parameters, airborne particles and air exchange rates (AER) were recorded. The parameters mold status, characteristics of the interiors and measured climatic parameters were included in the multiple regression model. The results show no significant association between most of the analyzed MVOC and the mold status. Only the compounds 2-methyl-1-butanol and 1-octen-3-ol indicated a statistically significant, but weak association with the mold status. However, the concentrations of the so-called MVOC were mainly influenced by other indoor factors. 2-Methylfuran and 3-methylfuran, often used as main indicators for mold damage, had a highly significant correlation with the smoking status. These compounds were also significantly correlated with the humidity and the AER. The compounds 3-methyl-1-butanol, 2-hexanone, 3-heptanone and dimethyl disulfide were weakly correlated with the recorded parameters, the humidity being the strongest influencing factor. Only 2-methyl-1-butanol and 1-octen-3-ol showed a statistically significant association with the mold status; however, only a small portion (10% in this case) of the total variability could be explained by the predictor mold status; they do not qualify as indicator compounds, because such minor correlations lead to a too excessive part of incorrect classifications, meaning that the diagnostic sensitivity and specificity of these compounds are too low. PRACTICAL IMPLICATIONS: The assumption that mold infestations might be detected by microbial VOC emissions must be considered with great reservation. The major part of the total variability of the measured MVOC concentrations originates from not known influencing factors and/or from factors not directly associated with the mold status of the dwellings (confounders). More specific and sensitive markers for the assessment of the mold status should be found, if the screening for mold infestations should be performed by volatile organic compounds.

Emission patterns and emission rates of MVOC and the possibility for predicting hidden mold damage?

UNLABELLED: Laboratory trials were performed in order to search for the variety of the production of microbial volatile organic compounds (MVOC), which could be used as indicators for hidden mold damage. Concerning MVOC production the experiments showed a dependency on the mold genus/species, the different strains used and the building materials used as substrate. It could be proved that the production of certain MVOC is not consistent at all times. On the whole low emission rates in terms of microg/h/m2 of the MVOC were found. Extrapolating the emissions rates from the laboratory trails to an indoor air situation results in concentrations below the analytical detection limit in most cases. According to these results only heavy or very large fungal contaminations might be detected by this method in indoor air. The studies were performed at the Institute of Hygiene and Environmental Medicine, Charite, Germany. PRACTICAL IMPLICATIONS: Microorganisms like bacteria and molds produce a huge variety of substances, and a part of them are released into the environment. Some compounds like, e.g. alcohols or ketones are volatile, therefore found in the air and called MVOC. Those compounds were considered helpful to track especially hidden mold damage. The study presented here showed, that the emission pattern varies from genus to genus and sometimes even from fungal strain to fungal strain. The results concerning the emission rates from different infested building materials proved, that the concentrations produced are much too low to be detected in indoor air, especially considering the dilution because of ventilation. Therefore, we conclude that MVOC should not be used as predictors for mold damage in indoor environments.

[Comparison of mycological and chemical analytical laboratory methods for detecting mold damage in indoor environments]. / Vergleich mykologischer und chemisch-analytischer Labormethoden zum Nachweis von Schimmelpilzbefällen in Innenräumen.

To evaluate frequently used methods that discriminate between moldy and nonmoldy indoor environments, 45 homes with visible mold growth and 47 definitively non-infested homes, both confirmed by inspection, were investigated by microbiological and chemical analytical methods. The study was laboratory blinded in relation to the confirmed mold status of the rooms. Statistical evaluation of the results of the applied mycological methods with the Receiver Operating Characteristic (ROC) curve analysis showed that these methods (impaction, open Petri dish method, and determination of mold spores in house dust samples) performed very well in discriminating between rooms with visible mold growth and nonmoldy rooms when the sum score of the mold genera Aspergillus and Penicillium was used as an indicator. The calculated areas under the ROC curves (AUC) of the three mycological methods were: 0.992 (95% CI 0.942-0.997) for mold spores in house dust samples, 0.996 (95% CI 0.940-0.998) for the open Petri dish method, and 0.999 (95% CI 0.957-1.000) for the determination of airborne spores with the Andersen impactor, respectively. A perfect discrimination would lead to an AUC of 1. These results were obtained with DG 18-agar as well as with malt extract agar. In contrast to the results of the mycological methods, the chemical analytical method under the same study conditions showed a distinctly lower performance in discriminating rooms according to their mold status when a sum score (concentration of eight typical MVOC) was used as an indicator. The area under the ROC curve (AUC) had a value of 0.620 (95% CI 0.509-0.723). A completely useless test would have an AUC of 0.5. As the lower limit of the 95% confidence interval of the area under the ROC curve is close to 0.5, the results obtained with the MVOC method do not differ from the classification results which can be obtained simply by chance. Possible methodological biases which could have lead to this interpretation are discussed.

Investigations on the survival time of outdoor microorganisms on air filters.

Outdoor microorganism survival on air filters was examined in 16-day field investigations. Using a mobile filter testing device, samples of fiberglass pocket filters (filter class F7) were ventilated with outdoor air, and their microorganism contents were determined at 1, 2, 4, 8 and 16-day intervals. The results showed a mean survival time of microorganisms deposited on the air filters of 1 to 3 days.

[Sick building syndrome and HVAC system: MVOC from air filters]. / Sick-Building-Syndrom und RLT-Anlagen: MVOC aus Luftfiltern.

Growth and emissions of volatile metabolites of microorganisms on air filters are suspected to contribute to health complaints in ventilated rooms. To prove the microbiological production of volatile organic compounds (MVOC), concentrations of aldehydes and ketones were determined in two large HVAC systems. The in situ derivated aldehydes and ketones (as 2,4-dinitrophenyl-hydrazones) were analysed by HPLC and UV detection. The detection limit of each compound was 1 ppb (margin of error < 10%). Field measurements were carried out before and after the prefilters and the main filters, respectively, to investigate whether aldehydes and ketones increase in concentration after filters of HVAC systems. First results show that the compounds formaldehyde, acetaldehyde and acetone could be detected before and after the filters. The concentrations of these VOC after the filters were significantly increased--as a mean over twenty measurements--, especially as far as filters made of glass fibre are concerned. However the found concentrations were low and mostly comparable to outdoor findings. In simultaneous laboratory experiments pieces of used filter material of one HVAC system and unused filter pieces (for blank values) were examined in small incubation chambers to investigate the possible production of MVOC. For the incubation a temperature of 20 degrees C and a relative humidity of 95% was chosen. In these experiments an almost identical spectrum of compounds (formaldehyde and acetone) was found as in the field measurements. The concentrations of these compounds were higher in the chambers with the used filter pieces. The concentration of acetone ranged up to almost 12 mg/m3.--As our field experiments correspond with our laboratory experiments, we assume that the microbial production of volatile organic compounds in HVAC systems under operating conditions is possible.

[Nitrated polycyclic aromatic hydrocarbons (nitro-PAH) in the suspended substances of the atmosphere. 2. Comparison of the mutagenicity of nitro-PAH and dust extracts of the air in the Ames, SOS repair induction and SCE test]. / Nitrierte polyzyklische aromatische Kohlenwasserstoffe (Nitro-PAH) im Schwebestaub der Aussenluft. 2. Mitteilung: Vergleich der Mutagenität von Nitro-PAH und Luftstaubextrakten im Ames-, SOS-Reparatur-Induktions- und SCE-Test.

Extracts of airborne suspended particulate matter were assayed in the Ames-test with strain TA 98, in the SOS chromotest (test on induction of the SOS repair) with strains E. coli PQ37 and S. typhimurium TA 1535 and in the sister chromatid exchange test. Samples from Berlin-Wedding were extracted by dichloromethane and tested up to the limits of solubility. All three test systems showed biologic activity. In the Ames- and the SOS chromotest these extracts revealed higher activity with S9-mix. 4 nitro-PAH, which are known to be present in ambient urban air, were assayed in these test systems, checking them additionally with strains TA 1538, TA 100 and TA 1535 in the Ames-test. In this test these compounds appeared to be direct acting frameshift mutagens and their activity is diminished by addition of S9-mix. On the contrary these compounds were either active at all or more active in the SOS chromotest in the presence of S9-mix. In the SCE-test only with exogenous activation a raise of the SCE frequency could be detected.

[Nitrated polycyclic aromatic hydrocarbons (nitro-PAH) in suspended particles in the atmosphere. 1. Fractionation and analytic detection]. / Nitrierte polyzyklische aromatische Kohlenwasserstoffe (Nitro-PAH) im Schwebstaub der Aussenluft. 1. Mitteilung: Fraktionierung und analytischer Nachweis.

A procedure to determine nitrated polycyclic aromatic hydrocarbons from suspended particulate matter was developed. Depending on the organic amount needed, different prefractionation steps are described, starting from thin layer chromatography and solid phase extraction by a cartouche system for small amounts, reaching over column chromatography to preparative HPLC for extracts corresponding up to 1000m3. Prior to analysis Nitro-PAH were reduced to the corresponding amines by a modified method given by Jäger. After reduction these amines could be trapped selectively by ion change chromatography and eluted as a pure fraction with a mixture of methanol/isopropylamine 1/1. This mixture can be easily evaporated and the sample is redissolved in acetonitrile/water 80/20, buffered at pH 7.2 by 0.1 M Tris-buffer. 20 microliter of that solution is injected in a HPLC system with a reversed phase column (250 x 4 mm, 5 micron) and fluorescence detection. According to the strong fluorescence properties of amino-PAH detection limits of 5-50 pg could be achieved. Thus, depending on the preconcentration factor (up to 100 m3 per 200 microliter) these compounds could be detected in the range from 0.5-5 pg/m3.

[Polar neutral organic compounds in urban aerosols. 1. Chemical characterization and mutagenic effect in relation to various sources]. / Polare neutrale organische Verbindungen (POCN) im Stadtaerosol. 1. Mitteilung: Chemische Charakerisierung und mutagene Wirksamkeit in Abhängigkeit verschiedener Quelleinflüsse.

Airborne particulate matter was collected by high volume samplers at two sampling stations in Berlin (West) between March 1983 and February 1984 (immissions). The stations were choosen so that two main-sources of urban air pollution could be considered (automobile) traffic and private fuel combustion (domesticfuel). Also in February and March 1983 particles were collected from private coal firing (emissions). The collected particles were fractionated into the following particle sizes (immissions, during October 1983-February 1984): greater than 7.2 microns, 7.2-1.5 microns and less than 1.5 micron (aerodynamic diameter). The etherextractable organic matter of the particles (= EEOM) was determined and the organic matter was then separated into acidic, basic, and neutral fractions. The neutral fraction was further separated into aliphatic compounds (= AlP), polycyclic aromatic hydrocarbons (= PAH), and polar neutral compounds (= POCN) by thin layer chromatography. The mutagenic activity of all organic fractions was determined by using the mammalian microsome bioassay by Ames and was compared with the activity of a whole polar organic extract (including POCN, acidic and basic fraction), a whole neutral extract, and a whole ethersoluble organic extract. Also in February 1984 the nitroreductase specific mutagenicity on immission-stations was determined using nitroreductase deficient strains. Some compounds of the POCN-fraction, and of PAH (in comparison) were identified by gas chromatography. The following results were obtained: The neutral fraction of the organic matter amounted to 70-90% of the EEOM (not depending from particle size, immissions and emissions). The separation of the neutral compounds into AlP, PAH and POCN showed a higher amount of AlP at the collecting station which includes mainly automobile traffic. Some cancer and/or mutagenic suspect compounds were identified by the chromatographic analysis of POCN and PAH. A higher amount of several nitrogroups-containing POCN was found at the collecting station which includes mainly private combustion whereas at the station including mainly automobile traffic 1-nitropyrene was the main compound. The POCN-fraction showed the mostly highest mutagenic activity in the Ames bioassay, mainly for lung penetrating particles (less than 1.5 micron diameter). The whole organic extract (EEOM) showed a lower mutagenic activity than the POCN-fraction. Using nitroreductase deficient strains, at the collecting station which includes mainly private fuel combustion a higher reduction of mutagenicity was shown than at the automobile-traffic including measurement station.

[Mutagenicity of 3 organic fractions of atmospheric dust and gas chromatographic analysis of the basic fraction]. / Mutagene Wirkung von drei organischen Fraktionen von Luft-stäuben und gaschromatographische Untersuchung der basischen Fraktion.

Suspended particulate matter (PM) with a Dae less than 0.4 micron was collected from July 1981 till January 1982. The ether/benzene soluble extract (EEOM) and the acidic, basic and neutral fractions were determined and investigated for their mutagenic activities in the Ames bioassay. In addition particles (Dae) less than 10.2 micron derived in January were investigated. Five compounds of the basic fraction were determined by gaschromatography. The following results were obtained: Suspended particulate matter (Dae less than 0.4 micron) and the ether/benzene extract increase from July to January. The lowest rates occur in July (PM: 16.9 micron/m3) and August (EEOM: 3.0 micrograms/m3), the highest in January (PM: 48.9 micrograms/m3, EEOM: 10.5 micrograms/m3). The ether/benzene soluble portion of the suspended particulate matter increases from the average rate of 16.3% (July-September) to 22.7% (November-January). The neutral fraction amounts to 44.9%, the acidic fraction to 27.3% and the basic fraction to 3.5% of the organic matter (on an average). In experiments with metabolic activation 99% of the total mutagenicity during the period of July till September can be demonstrated by summing up the mutagenicity of the three fractions on the other hand only 59.7% from November till January. The EEOMs derived from winter exhibit without metabolic activation (250 micrograms/plate) distinctively higher numbers of revertants than the single fractions. Dose-response curves of extracts derived from back-up filters (Dae less than 0.4 micron) in January show that the acidic fraction has a slightly higher mutagenic activity than the neutral fraction (mean values of tests with and without S9-mix). The basic fraction shows no mutagenicity without S9-mix, with activation the mutagenic activity is lower than that of the other fractions. Mutagenicity expressed as rev./m3 air shows, that the neutral fraction is most efficient. The number of revertants per plate reveals-in relation to the particle size-different results concerning the three fractions (January).