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Biomedical subjects

W Eduard

Publications and source records attributed to W Eduard.

36 records · Page 2Linked to original sources
PubMed1998

Methods for quantitative assessment of airborne levels of noninfectious microorganisms in highly contaminated work environments.

Exposure to high airborne levels of noninfectious microorganisms is recognized as a cause of respiratory symptoms and disease among workers handling biological materials, such as farmers, sawmill workers, and workers handling municipal waste and fuel chips. Risk assessment is difficult because occupational exposure limits for noninfectious microorganisms have not been established. Many different methods are used for the measurement of airborne microorganisms, which are based on impaction, impingement, or filtration. Samples can be analyzed by methods that are culture-based or nonculture-based and that may estimate different microbial entities: culturable microorganisms by culture-based methods, microbial cells by microscopic methods, and microbial constituents and products by chemical, biochemical and immunochemical methods. Sources of errors and validation studies of these methods are reviewed and methods are evaluated for exposure assessment in epidemiological studies and for future compliance testing. At present it is not clear which microbial bioaerosol components should be assessed. Culture-based methods are probably not satisfactory because nonviable microorganisms and microbial constituents and products also may cause health effects. Culture-based methods are poor surrogates for nonculture-based methods and have poor precision. However, identification of microorganisms is most readily performed by culture-based methods. Filter sampling is preferred for personal exposure measurements because filters can be analyzed by a variety of nonculture-based methods, and filter sampling may be adapted to recently adopted criteria for health-related size fractions.

Aerosols↗
PubMed1998

Determinants of asthma in a farming population.

OBJECTIVES: This study examined the determinants of asthma in a population of farmers, including as a crude indicator of genetic predisposition "history of asthma in next-of-kin" (family history), and exposure factors such as animal production and smoking. METHODS: In a cross-sectional study of 8482 farmers or farmers' spouses in Norway a questionnaire with information on asthma among the subjects and their next-of-kin, production type and farming activities, exposures outside farming, and smoking was applied. Spirometry was performed. RESULTS: The lifetime prevalence of self-reported asthma in the population was 6.3%. Significant risk factors for current asthma were asthma among next-of-kin, asthma as child or adolescent, animal production, and age. In a comparison with subjects with no family history of asthma and no animal production the adjusted odds ratio for current asthma in never smokers was 1.9 [95% confidence interval (95% CI) 0.4-8.9] for subjects with family history only, 2.2 (95% CI 1.1-4.2) for subjects with animal production only, and 6.3 (95% CI 3.1-13.1) for subjects with both factors. A combination of animal production, smoking, and a positive family history gave an odds ratio of 8.1 (95% CI 4.0-16.2) for current asthma. CONCLUSIONS: The study can be interpreted as support for the hypothesis of an interaction between genetic factors and exposure factors in the causation of asthma. Since familial associations may be exposure-related, the necessity of considering indicators of both inheritance and exposure in epidemiologic studies of asthma is emphasized.

Adult↗
PubMed1997

A test chamber for experimental hydrogen fluoride exposure in humans.

An inhalation chamber was built to perform experimental studies with hydrogen fluoride (HF), other gases, and particulate matter. The present study sought to describe a new gas delivery system and the distribution and concentration of HF gas in the chamber. The aluminum chamber has a volume of 19.2 m3 and a variable ventilation rate of about 1 to 10 air changes per hour. The negative pressure difference between the chamber and outside air can be regulated from 0 to 300 Pa. HF was fed at concentrations of up to 4000 mg/m3 directly into the ventilation duct feeding the chamber through openings with diameters as small as 50 microns, oriented opposite to the airflow. Gas flow was varied from about 0.1 dm3/min at a pressure of 4 atm. The dilution factor of HF concentration from cylinder to chamber was on the order of 10(3) to 10(4). The standard deviation (SD) of the HF concentrations at a fixed measurement point during a 1-hour test was typically 0.05 mg/m3 at a time-weighted average (TWA) concentration of 2.66 mg/m3. The SD of the TWA HF concentrations at six locations in the chamber was typically 0.05 mg/m3 and 0.29 mg/m3 at 0.61 and 3.46 mg/m3, respectively. Human exposure could be predicted from calculations based on ventilation data, gas flow, and observed ratio between calculated and measured concentrations. When the target exposure concentration was 1.5 mg/m3, the measured mean exposure concentration was typically 1.54 mg/m3 (range: 1.4-1.7 mg/m3, SD 0.09 mg/m3, n = 8). The chamber is well-suited for inhalation studies in humans. Chamber atmosphere was controlled and has proved to be stable and homogeneous, even in tests with HF, a highly reactive gas in the class of superacids.

Air Pollutants↗
PubMed1997

Chronic bronchitis in farmers.

OBJECTIVES: Chronic bronchitis was studied in relation to work time and years of exposure in farming, as well as to production type, dusty occupation outside farming, and the combination of work exposure and smoking, in a population of farmers. METHODS: In 1989 a representative cohort of 10,792 farmers and spouses was selected from a government register and invited to participate in a cross-sectional study in 1991. The total response rate was 80%. There were 33% part-time farmers, and among the men 32% of the full-time and 42% of the part-time farmers had worked in dusty occupations outside farming. Bronchitis symptoms were recorded on a self-administered questionnaire, spirometric data were obtained, and internal reference equations were calculated for forced expiratory volume in 1 s (FEV1.0). RESULTS: The exposure factors of importance for chronic bronchitis were full-time farming versus part-time farming, livestock production types (poultry, dairy, swine, horse and combinations), and occupational dust exposure outside agriculture. The combinations of the work exposure factors were significant and showed a 2- to 3-fold increase in risk for chronic bronchitis. Combinations with smoking showed up to a 6-fold increase in risk. Over the age of 50 years, chronic bronchitis was a risk factor for airway obstruction defined as the standardized residuals for FEV1.0 less than -2 for both nonsmokers (OR 2.8, 95% CI 1.1-6.8) and smokers (OR 8.5, 95% CI 5.1-14.3). CONCLUSIONS: Work exposure factors in farming and other dusty occupations enhance the risk for chronic bronchitis from 2- to 3-fold for farmers. In combination with smoking the risk increases to up to 6-fold.

Adult↗
PubMed1996

Comparative study of an inhalable and a total dust sampler for personal sampling of dust and polycyclic aromatic hydrocarbons in the gas and particulate phase.

For many years the closed-face plastic cassette has been widely used for monitoring 'total' dust in working atmospheres. In the late 1980s a different personal sampler was developed at the Institute of Occupational Medicine in Edinburgh. This so-called IOM sampler was designed to meet the criteria for inhalable dust (EN 481). In this work, a comparison of the closed-face 25 mm Gelman total dust sampler and the IOM inhalable sampler was made for exposure measurements of dust and PAHs among workers in an electrode paste plant. The two samplers were modified in order to permit sampling of both particulate and gas-phase PAHs. Three groups with different tasks were examined. The particle size distribution was determined using personal inhalable dust spectrometers and the GRIMM particle counter. The results showed that higher concentrations of dust and particulate PAHs were measured with the IOM inhalable sampler than the Gelman total dust sampler and the difference between the samplers was significant. This is in agreement with previously reported studies. In some samples collected with the IOM sampler very large particles were observed. There was no significant difference between volatile PAHs measured with the two samplers. For semi-volatile PAHs a significant difference between the samplers was observed, which was ascribed to evaporation loss from the filters during storage.

Air Pollutants, Occupational↗
PubMed1996

Measurement methods and strategies for non-infectious microbial components in bioaerosols at the workplace.

Exposure to micro-organisms can be measured by different methods. Traditionally, viable methods and light microscopy have been used for detection of micro-organisms. Most viable methods measure micro-organisms that are able to grow in culture, and these methods are also common for the identification of micro-organisms. More recently, non-viable methods have been developed for the measurement of bioaerosol components originating from micro-organisms that are based on microscopic techniques, bioassays, immunoassays and chemical methods. These methods are important for the assessment of exposure to bioaerosols in work environments as non-infectious micro-organisms and microbial components may cause allergic and toxic reactions independent of viability. It is not clear to what extent micro-organisms should be identified because exposure-response data are limited and many different micro-organisms and microbial components may cause similar health effects. Viable methods have also been used in indoor environments for the detection of specific organisms as markers of indoor growth of micro-organisms. At present, the validity of measurement methods can only be assessed by comparative laboratory and field studies because standard materials of microbial bioaerosol components are not available. Systematic errors may occur especially when results obtained by different methods are compared. Differences between laboratories that use the same methods may also occur as quality assurance schemes of analytical methods for bioaerosol components do not exist. Measurement methods may also have poor precision, especially the viable methods. It therefore seems difficult to meet the criteria for accuracy of measurement methods of workplace exposure that have recently been adopted by the CEN. Risk assessment is limited by the lack of generally accepted reference values or guidelines for microbial bioaerosol components. The cost of measurements of exposure to microbial bioaerosol components may be high owing to expensive analyses and highly variable exposure levels. The use of qualitative indicators of microbial growth, recording of health effects, specific immunoglobulin G antibody levels to prevalent species in serum of exposed workers and stratified sampling may help to reduce the costs of exposure assessment. An example of a combined strategy for assessment of health risks from handling mouldy timber is shown.

Aerosols↗
PubMed1996

A laboratory method for generation of replicate filter samples of asbestos fibers in air.

An exposure chamber for generation of 10 replicate filter samples of asbestos fibers is described. The coefficient of variation of replicate samples from laboratory generated amosite aerosol was less than 2.6% in samples with densities of 15 to 250 fibers/mm2. Thus, generation of replicate filter samples of asbestos fibers was possible on a small scale with good precision. Air ionization by an ion source did not alter the variability of replicate samples at relative humidities of 40% or higher. The exposure chamber is of moderate weight and can also be used in the field for collection of replicate samples from working environments.

Air↗
PubMed1993

Serum IgG antibodies to mold spores in two Norwegian sawmill populations: relationship to respiratory and other work-related symptoms.

Wood trimmers and planing operators from two separate sawmill populations (N = 303 and 170) were studied by serology assessment and a self-administered questionnaire. IgG antibodies to Rhizopus microsporus ssp. rhizopodiformis, Paecilomyces variotii, and Aspergillus fumigatus were measured by ELISA. The questionnaire included questions about general respiratory symptoms and symptoms after handling moldy timber. Personal exposure of wood trimmers to mold spores and wood dust was measured in one part of the sawmills. R. microsporus was the most prevalent mold assessed by serology. Antibody levels were higher and symptoms suggestive of mucous membrane irritation, chronic nonspecific lung disease, allergic alveolitis, and organic dust toxic syndrome were more frequently reported by wood trimmers than by planing operators. The mean level of IgG antibodies to R. microsporus in sawmill workers working in the same work area was the best predictor of symptoms in both populations. The consistent results indicate that exposure to spores of R. microsporus may cause several respiratory symptoms in wood trimmers.

Adult↗
PubMed1992

Detection and quantitation of antibodies against Rhizopus by enzyme-linked immunosorbent assay.

In sawmills high concentrations of spores from the mould Rhizopus microsporus may occur, causing allergic alveolitis in exposed workers. Both symptomatic and asymptomatic exposed workers may develop antibodies. An enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies to Rhizopus has been developed in order to study the relationship between antibody levels and exposure levels. The precision of the measurements of Rhizopus antibodies by ELISA carried out on the same microtiter plate was estimated to be 11%. It is therefore possible to detect changes in antibody levels of approximately 25% or more. Antibodies were studied longitudinally by ELISA in 60 wood trimmers. The observed changes in antibody levels exceeded the precision of the ELISA method substantially, indicating significant variability in antibody levels in wood trimmers. The ELISA test was compared with the double immunodiffusion test (DID). Sera from 67 wood trimmers were analyzed by both methods. Antibodies were detected by ELISA in 70% and by DID in 28% of the workers in this group, clearly demonstrating that the ELISA test is the most sensitive method for the detection of antibodies to Rhizopus.

Antibodies, Fungal↗
PubMed1992

Relationships between exposure to spores from Rhizopus microsporus and Paecilomyces variotii and serum IgG antibodies in wood trimmers.

A longitudinal study of wood trimmers exposed to mould spores was carried out from 1985 to 1988. Exposure to airborne spores from Rhizopus microsporus ssp. rhizopodiformis and Paecilomyces variotii was measured by scanning electron microscopy of filter samples. Specific IgG antibodies to these moulds were measured by ELISA in serum samples collected at half-year intervals. Antibody levels to R. microsporus and P. variotii were higher in wood trimmers than in other sawmill workers whose jobs had an assumed lower exposure to mould spores. Antibody levels were significantly elevated after periods with high exposure compared to antibody levels in the same wood trimmers after periods with low exposure. Antibodies were also found in newly employed wood trimmers. These wood trimmers were exposed to 1,300 x 10(3) R. microsporus spores/m3 and 130 x 10(3) P. variotii spores/m3 (arithmetic mean exposure). Antibody levels in the newly employed wood trimmers were similar to antibody levels in wood trimmers who had already worked in the trimming department before the start of the study. Antibody levels to R. microsporus and P. variotii in wood trimmers can be regarded as indicators of fairly recent exposure. There were, however, large differences between the individual antibody levels of similarly exposed wood trimmers.

Adult↗
PubMed1990

Evaluation of methods for enumerating microorganisms in filter samples from highly contaminated occupational environments.

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

Air Microbiology↗
PubMed1985

Occurrence of airborne silicon carbide fibers during industrial production of silicon carbide.

Airborne dust from the production of silicon carbide has been analyzed for particle morphology and composition. Fibers of alpha silicon carbide were identified by scanning electron microscopy (SEM) combined with energy dispersive X-ray spectrometry (EDS) and transmission electron microscopy (TEM) with selected area electron diffraction techniques (SAED). Micrographs taken at high magnification revealed several stacking periods along the fiber axis, and one or more of the polytypes 2H, 4H, or 6H could be distinguished. Preliminary investigations applying SEM showed that 80% of the fibers had diameters of less than 0.5 micron and a length greater than 5 micron. Fiber concentrations were examined by the counting of stationary and personal samples in an optical phase contrast microscope. The fiber levels in the three plants investigated were low and less than 1 fiber/cc of air (10(6) fibers/m3). Dust samples from the handling of raw material, including recycled material, contained up to 5 fibers/cc (5 X 10(6) fibers/m3).

Air Pollutants, Occupational↗
PubMedDate not supplied

Dust and gas exposure in tunnel construction work.

Personal exposures to dust and gases were measured among 189 underground construction workers who were divided into seven occupational groups performing similar tasks in similar working conditions: drill and blast crew; shaft-drilling crew; tunnel-boring machine crew; shotcreting operators; support workers; concrete workers; and electricians. Outdoor tunnel workers were included as a low-exposed reference group. The highest geometric mean (GM) exposures to total dust (6-7 mg/m3) and respirable dust (2-3 mg/m3) were found for the shotcreters, shaft drillers, and tunnel-boring machine workers. Shaft drillers and tunnel-boring machine workers also had the highest GM exposures to respirable alpha-quartz (0.3-0.4 mg/m3), which exceeded the Norwegian occupational exposure limit (OEL) of 0.1 mg/m3. Shaft drillers had the highest exposure to oil mists (GM=1.4 mg/m3), which was generated mainly from pneumatic drilling. For other groups, exposure to oil mist from diesel exhaust and spraying of oil onto concrete forms resulted in exposures of 0.1-0.5 mg/m3. Exposure to nitrogen dioxide was similar across all groups (GM=0.4-0.9 ppm), except for shaft drillers and tunnel-boring machine workers, who had lower exposures. High short-term exposures (>10 ppm), however, occurred when workers were passing through the blasting cloud.

Dust↗
PubMedDate not supplied

Hazardous peak concentrations of hydrogen sulfide gas related to the sewage purification process.

The concentration of hydrogen sulfide in the atmosphere of a sewage purification plant in Norway was studied. Continuous measurements over several 3-week periods showed that the concentrations generally were lower than 2 ppm, but peak concentrations over 100 ppm were discovered. Rapid onset and decline characterized these peak concentrations, which occurred at regular intervals. Through evaluation of the time pattern of these peaks compared with plant operations, a specific process was identified as the likely causative factor of the spikes. Through simple remedial actions the hydrogen sulfide concentration associated with this activity was reduced from above 100 ppm to less than 2 ppm. Olfactory fatigue to hydrogen sulfide and strong offensive odors from other compounds in the sewage makes smell ineffective for signaling high concentrations. Peak concentrations may therefore pass unnoticed unless detected with continuous measuring equipment. The risk for exposure may be reduced by enclosing processes and through the use of spot extraction ventilation in areas with compacted anaerobic waste material.

Air Pollutants, Occupational↗