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W Dott

Publications and source records attributed to W Dott.

At least 19 recordsLinked to original sources
PubMed2005

[Comparison of methods for quantification of MVOC in indoor environments].

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

Air Pollutants, Occupational↗
PubMed2005

Indoor environment and respiratory symptoms in children living in the Dutch-German borderland.

OBJECTIVE: To investigate the relation between indoor environmental risk factors and respiratory symptoms in 7-8-year-old children living in the Dutch-German borderland. METHODS: A nested case-control study was conducted among children participating in a large longitudinal study on respiratory health. Parents of all 781 children with respiratory complaints and an equal number of randomly selected controls were asked to complete a questionnaire, including questions on indoor environment. RESULTS: The parents of 1191 children (76.2%) participated. Past exposure to environmental (OR = 2.73, 95% CI 1.14-6.67) as well as in utero exposure (OR = 2.28, 95% CI 1.15-4.53) to tobacco smoke, use of an unvented geyser for water heating (OR = 3.01, 95% CI 1.21-7.56), long-term exposure to dampness (OR = 2.98, 95% CI 1.10-8.28) or pets (OR = 2.18, 95% CI 1.39-3.42) increased the risk of asthmatic symptoms in 7-8-year-old children. A middle or low socio-economic status also increased the risk of asthmatic symptoms. An inverse association with asthmatic symptoms was seen for wall-to-wall carpeting (OR = 0.57, 95% CI 0.33-0.95) and insulation measures (OR = 0.46, 95% CI 0.25-0.83). Except for the presence of an unvented geyser, these environmental risk factors also presented a risk for coughing symptoms in children. CONCLUSION: This study showed an increased risk of respiratory symptoms in children exposed to several indoor environmental risk factors.

Air Pollution, Indoor↗
PubMed2005

Differences in asthma diagnosis and medication use in children living in Germany and the Netherlands.

AIM: To compare diagnosis and treatment between German and Dutch children with asthmatic symptoms at the age of 5-6 and 7-8 years, and the use of anti-asthma medication at 7-8 years of age. METHODS: Parents of 4462 children participated in two surveys, in 1995 and 1997. All 465 children identified with current asthmatic symptoms at the age of 5-6 (May 1995) or at 7-8 years of age (May 1997) were sent a third more detailed questionnaire (October 1997). RESULTS: Asthma diagnosis was more prevalent in Dutch children with current asthmatic complaints (50-60%), whereas over 90% of the German children with current asthmatic complaints had been diagnosed with bronchitis. Inhaled beta(2)-agonists were more frequently used by Dutch children compared to German children (67.3% vs. 45.6% p < 0.01) as were inhaled steroids (38.9% vs. 7.0% p < 0.01). Instead, German children more often used sodium cromoglycate or nedocromil as anti-inflammatory medication as compared with Dutch children (42.1% vs. 11.5% p < 0.01). CONCLUSIONS: Differences in diagnosis rates for asthma and bronchitis between German and Dutch children most likely result from differential labelling of complaints, and probably lead to differences in treatment practice, indicating possible undertreatment of German children with inhaled steroids.

Journal Article↗
PubMed2004

Infant immunization and the occurrence of atopic disease in Dutch and German children: a nested case-control study.

Our goal was to assess the role of early childhood vaccination in the occurrence of respiratory symptoms and allergic sensitization in 7-8-year-old Dutch and German children. A nested case-control study was conducted among children participating in a large longitudinal study on respiratory health, to study the relationship between vaccination (bacille Calmette-Guérin (BCG), pertussis, measles/mumps, rubella, and Haemophilus influenza type b (Hib)) and respiratory symptoms and allergic sensitization. Parents of 510 7-8-year-old children with respiratory complaints and an equal number of randomly selected children without respiratory complaints were asked to complete a questionnaire. Blood samples were collected for specific serum IgE analysis. Vaccination status was assessed through the records of the participating Municipal Health Services. No association between vaccination against pertussis, measles, rubella, or Hib and respiratory symptoms or allergic sensitization was found. For sensitization against house dust mite, BCG vaccination resulted in an increased risk (OR, 2.28; 95% CI, 1.05-4.96). Birth order was inversely associated with allergic sensitization, but was not related to respiratory symptoms. We found an association between BCG vaccination and the subsequent risk for sensitization against house dust mite. No evidence was found for an association between vaccination and respiratory symptoms. Earlier reports of an association of birth order with atopic disease were supported by the results of the present study.

BCG Vaccine↗
PubMed2004

Acute toxicity investigations of ester-based lubricants by using biotests with algae and bacteria.

Although ester-based lubricants are ecologically acceptable due to their good biodegradability, there are still some environmental ecotoxicological impacts that have to be considered. Information on the acute ecotoxicological behavior of lubricants is obtained in this work using several single species bioassays. In previous studies it was observed that lubricating fluids containing additives for the enhancement of their technical performance were more problematic than base fluids especially with respect to algae growth inhibition. In order to clarify the influence of additives, the anti-wear additive tri-n-butyl phosphate was tested. It was very toxic to algae though not to bacteria. Additionally, a mixture of this additive with a base fluid is characterized. Despite the high toxicity of the single additive, the water extract of the mixture of tri-n-butyl phosphate with hydraulic base fluid caused almost no toxicity. Therefore, tri-n-butyl phosphate cannot explain the effect observed for the toxicity of water extracts of the commercially available lubricants.

Biological Assay↗
PubMed2004

Efficiency of nanofiltration for the elimination of steroids from water.

Steroid hormones such as the synthetic 17-alpha-ethinylestradiol often persist in the sewage treatment process and metabolites of the natural steroids like estrone from estradiol accumulate resulting in relevant amounts in the aquatic environment. Since biological removal of steroids in the sewage treatment plant is not successfully complete, physical processes such as membrane filtration may become more important. We investigated the elimination of natural and synthetic steroids by nanofiltration using a laboratory membrane reactor. Chemical analysis of 17-beta-estradiol, estrone, estriol, 17-alpha-ethinylestradiol, mestranol, diethylstilbestrol, progesterone and beta-sitosterine was performed after solid phase extraction by GC-MS with standard addition. The elimination rate depended on the nanofiltration membrane material. LFC1 membrane consisting of polyamide removed the steroids over 99% whereas PES10 membrane consisting of hydrolysed polyethersulfone was less efficient, obviously caused by different pore sizes and permeability of the membrane structure.

Animals↗
PubMed2003

Effect of sample preparation on the in vitro genotoxicity of a light curable glass ionomer cement.

The glass ionomer cement Vitrebond showed a clear genotoxic effect in the in vitro Mammalian Cell Gene Mutation Test (HPRT Test) with CHO cells as well as in the bacterial umu-test with Salmonella typhimurium TA1535/pSK1002. Both DMSO and Ham's F12 cell culture medium extracts according to ISO 10993-12 (Biological evaluation of medical devices-Part 12: sample preparation and reference materials, Geneva, Switzerland) exhibit a clear genotoxic effect in the umu-test. The effect is independent of the extraction volume in a range from 0.5 to 4 ml Ham's F12 cell culture medium. Subsequent extractions of Vitrebond showed no significant difference in the genotoxic response although weight loss and content of 2-hydroxyethyl-methacrylate dropped significantly. In vivo conditions of Vitrebond were simulated by extractions with artificial and collected human saliva. These extracts showed a clear genotoxic effect in the umu-test, even if only a few seconds of extraction time were applied. In conclusion, sample preparations for genotoxicity testing according to ISO 10993-12 reflect the in vivo conditions of Vitrebond applications. This seems to be mostly due to the hydrophilic nature of the genotoxic ingredients.

Animals↗
PubMed2002

Selective enrichment and characterization of a phosphorus-removing bacterial consortium from activated sludge.

Under alternating aerobic/anaerobic conditions and without additional carbon sources, a bacterial consortium consisting initially of 18 bacterial strains was obtained in a sequence batch reactor. The phosphorus removal capability could only be maintained using sterile filtrate of activated sludge as medium. The addition of calcium and magnesium salts, as well as vitamins and trace elements, to autoclaved sterile filtrate of activated sludge was not sufficient to achieve stable phosphorus removal. A further enrichment by subcultivation on solid, agar, freezing, and shortening of the aerobic and anaerobic phases led to a defined bacterial consortium consisting of four strains. On the basis of physiological and chemotaxonomic characterization, and partial 16S rRNA sequencing, one of the organisms was identified as Delftia acidovorans. A further isolate belonged to the Bacillus cereus group, and the third isolate was identified as Microbacterium sp.. The remaining strain seems to represent a new genus within the Flavobacteriaceae. Under continuous chemostat conditions, this consortium was able to remove up to 9.6 mg P/l phosphate in the aerobic phase and released up to 8.5 mg/l in the anaerobic phase. Up to 25 mg P-polyphosphate/g dry mass was stored under aerobic conditions.

Actinomycetales↗
PubMed2002

Quality assurance and good laboratory practice in the mycological laboratory--compilation of basic techniques for the identification of fungi.

The identification of microfungi by morphology is generally regarded to be very difficult, as traits used for delimitation of species within a genus often show minute differences that can only be reliably evaluated by experienced mycologists. Different strains of one species can slightly vary in their morphology. This is often used as an argument by investigators with rather limited experience that identification on a morphological basis is not reliable and leads to inconsistent results. This paper compiles essential methods and techniques contributing to improved identification concerning (i) isolation from mixed cultures, (ii) inoculation and incubation, (iii) usage of media, (iv) identification and usage of determination keys, (v) preparation of microscopic slides, (vi) microscopy, and (vii) storage of isolates. The application of chemotaxonomy and sequencing for routine identification of airborne microfungi is shortly evaluated. The techniques compiled here can improve routine determination work considerably and will lead to much more accuracy and consistency of results. An improved quality assurance of applied fungal identification in the field of indoor and occupational hygiene is a prerequisite to find possible correlations between exposure on the one hand and health effects on the other.

Clinical Laboratory Techniques↗
PubMed2001

Microcosms-experiments to assess the potential for natural attenuation of contaminated groundwater.

Groundwater samples from six wells of a former gas plant site were characterised using chemical, microbial and ecotoxicological methods. Degradation studies were performed in batch-culture under aerobic conditions with the groundwater samples containing their autochthonous microflora and original contaminant mixture. The highest O2-consumption (3 mmol 100 ml-1), combined with BTEX (8.3 mg l-1) and naphthalene (171.3 mg l-1) degradation, as well as formation of organic acids was found after N- and P-supplementation with the highest contaminated groundwater sample. The other highly polluted groundwater sample showed no activity obviously because of the toxicity of some compounds. The major part of the PAHs and BTEX was eliminated in the assays with the low contaminated groundwater samples. The results indicate that the microbial degradation capacity and thereby the natural attenuation capacity in each groundwater differ and cannot be assessed simply by chemical, microbial and toxicological data. Additionally activity tests with authentic groundwater samples with and without nutrient supplementation are recommended.

Carbon Dioxide↗
PubMed2001

Denitrification of groundwater with methane as sole hydrogen donor.

It was examined, whether methane can be used as hydrogen donor for an in situ denitrification of groundwater. It is demonstrated, that groundwater can serve as liquid medium and that the denitrification can occur at 10 degrees C. Efforts to enrich methanotrophic bacteria under anoxic conditions have not been successful. No methane oxidation occurred in the absence of oxygen. For this reason, the denitrification with methane must be performed in a two-stage process with aerobic methanotrophic bacteria producing metabolites, that are used as hydrogen donor by non-methanotrophic bacteria in anoxic areas. This kind of indirect denitrification was proved by quantifying nitrogen and nitrous oxide in enrichment cultures that were not stirred or shaken. Large numbers of non-methanotrophic bacteria being able to denitrify with methanol, acetate or proteins as sole hydrogen donor were enriched besides the methanotrophic bacteria under these conditions.

Aerobiosis↗
PubMed2001

[Interreg II--European regional study of chronic respiratory tract diseases in children in the Germany-Netherlands border zone].

AIM OF THE STUDY: In Westelijke Mijnstreek (WM), Midden-Limburg (ML), both The Netherlands, and Kreis Heinsberg (HS), Germany, the relationship between quality of the indoor environment and respiratory symptoms in children was studied, finally resulting in proposals for prevention of respiratory symptoms in the three regions. This paper presents the results of the first part of the study, investigating prevalences of respiratory complaints. METHODS AND RESULTS: A brief questionnaire was used to document prevalences of respiratory complaints, physicians diagnoses and treatment in about 7,000 children 5-6 resp. 7-8 years of age from HS, ML and WM, in 1995 and 1997. Prevalences of respiratory symptoms differed slightly between the regions, but there were differences in physician-diagnosed asthma and bronchitis and treatment of the children. PERSPECTIVES: The brief questionnaire is a useful instrument to get an overview on respiratory symptoms. Since 1995, it is used by several German Municipal Health Services for Public Health Reports.

Air Pollution, Indoor↗
PubMed2001

Sensitive indoor air monitoring of formaldehyde and other carbonyl compounds using the 2,4-dinitrophenylhydrazine method.

The toxic potential of formaldehyde and other aliphatic/aromatic carbonyl compounds requires the determination of even low amounts of these compounds in indoor air. The existing DFG-method for workplace monitoring using adsorption at 2,4-dinitrophenylhydrazine (DNPH)-coated sorbents followed by HPLC-UV/DAD analysis of the extract was modified in order to decrease detection limits. The improvement included an increase in volume and rate of the air sampling, testing applicability of different adsorption materials and a decrease of the extraction volume of the hydrazones. 13 DNPH-derivatives could be separated well on a RP18-column followed by UV/DAD-detection at 365 nm. Recovery rates of 70-100% were determined (apart from acetone with 19%) using dynamically produced artifical carbonyl atmospheres. Detection limits of 0.05-0.4 microgram/m3 were reached by this method which are sufficient for indoor air monitoring.

Air Pollutants, Occupational↗
PubMed2000

Biomonitoring of environmental polycyclic aromatic hydrocarbon exposure by simultaneous measurement of urinary phenanthrene, pyrene and benzo[a]pyrene hydroxides.

A high-performance liquid chromatographic method with fluorescence detection was developed which enables the simultaneous determination of the urinary polycyclic aromatic hydrocarbon metabolites 3-hydroxyphenanthrene, 1-hydroxypyrene and 3-hydroxybenzo[a]pyrene. The method has small solvent consumption because of the use of a microbore RP C18 column and a relatively short run time. Low detection limits of 0.02 nmol/l for 3-hydroxypyrene to 0.19 nmol/l for 3-hydroxybenzo[a]pyrene were attained. In contrast, the detection limits of alpha-naphthol and 9,10-dihydroxy-9,10-dihydrophenanthrene were not adequate for the determination of environmental exposure. The developed method was successfully used for the analysis of urine samples from children.

Air Pollutants↗
PubMed2000

Use of bioassays for assessment of water-extractable ecotoxic potential of soils.

The characterization of contaminated soils is based on heterogeneous strategies considering chemical analyses or bioassays. In the report Bioassays for soils, test methods which are at an advanced state of development and standardization are recommended by the German DECHEMA (German Society for Chemical Apparatus, Chemical Engineering and Biotechnology e.V.). Following this report six soil samples contaminated with different organic and inorganic substances are applied to bioassays using the following organisms: Scenedesmus subspicatus, Daphnia magna, Vibrio fischeri, and Pseudomonas putida. Additionally, they are chemically analyzed. The test results demonstrate that toxic contaminants are present and bioavailable in water elutriates from two soils, indicating the necessity of bioassays and chemical analyses to predict potential risks from contaminated soils. Furthermore it is demonstrated that the described qualitative approach for the assessment of test results is not sufficient to quantify the risk potential of contaminated soils.

Animals↗
PubMed2000

Assessment of the water-extractable genotoxic potential of soil samples from contaminated sites.

A screening method for the evaluation of the water-extractable genotoxic potential of soil is proposed. Due to the low sensitivity of genotoxicity test systems, PAD-1 resin was used as solid phase to concentrate less hydrophilic compounds from aqueous soil extracts. Concentrated and nonconcentrated aqueous soil extracts from 19 soil samples were evaluated using three genotoxicity assays: the umu test according to the German standard method with Salmonella typhimurium TA1535/pSK1002, the NM2009 test with S. typhimurium NM2009, and the SOS Chromotest with Escherichia coli PQ37. All tests were performed according to a uniform protocol using microplates. Results indicate that the nonconcentrated water elutriates should be tested because the genotoxic potential of some soil samples is extremely high. Additionally, water elutriates should be concentrated by solid phase extraction to avoid false-negative results. The results of this study show that the genotoxic risk of sites contaminated with PAHs or mineral oils may be underestimated if only nonconcentrated samples are tested. The solid-phase extraction method with a concentration factor of 30 for these low soluble compounds is suitable for distinguishing between background genotoxicity of noncontaminated sites and anthropogenic contaminations.

Escherichia coli↗
PubMed2000

A stepwise procedure for assessment of the microbial respiratory activity of soil samples contaminated with organic compounds.

Soil respiration measurements are used frequently for the characterization of soil samples. Identical methods are used for the ecotoxicological characterization of contaminated soil samples as well as for quantification of the active microbial biomass in agriculturally used soils. In this study four soil samples contaminated with large amounts of volatile organic compounds, polyaromatic hydrocarbons, or nitroaromatic compounds are characterized after stepwise addition of carbon, nitrogen, and phosphorus. The respiration kinetics are assessed over a period of 5 days. By means of qualitative evaluation of the results, it is demonstrated that this stepwise addition allows one to distinguish between growth-promoting effects of biodegradable organic compounds on the one hand and the toxic influence of these compounds on the other hand. Finally it is stated that a comprehensive ecotoxicological characterization cannot be performed routinely using only one or several parameters of respiration curves. There is need for further research and validation if soil respiration measurements are to be performed quantitatively in the future.

Environmental Monitoring↗