Biomedical subjects

W Eduard

Publications and source records attributed to W Eduard.

At least 19 recordsLinked to original sources

PubMed2006

Airborne fibres in the norwegian silicon carbide industry.

Morphology of silicon carbide (SiC) fibres from the Norwegian SiC industry has been studied by scanning electron microscopy (SEM). The fibres are an unwanted side-product in SiC production. They represent a probable cause of the observed increased occurrence of lung diseases among SiC workers. The main aim of this work is to give a detailed description of the morphological variation of the fibres. Furthermore, it is important to study the occurrence of various morphological types with respect to job types and process parameters. SiC fibres accounted for >90% of all fibres observed. Eight categories of SiC fibres are described based on their morphology. The most frequent fibre category had a smooth surface and accounted for more than half of the observed SiC fibres. The diameter distributions of the eight fibre types were significantly different except for two of the categories. More than 99% of the SiC fibres observed were <3 microm in diameter, satisfying one WHO criterion for health relevant fibres. The aspect ratio and diameter of health-relevant fibres generally followed a lognormal distribution for different fibre categories, whereas fibre length did not. The proportions of SiC fibres (all categories) did not differ significantly between the plants. The proportions differed between plants for two SiC fibre categories including the most dominant type. For two SiC fibre categories and the SiC cleavage fragments differences were observed between job groups. Two other fibre categories were correlated with type of SiC produced (i.e. black or green SiC) and sawdust added to the raw material mix.

Air Pollutants, Occupational↗

PubMed2006

Agricultural seed dust as a potential cause of organic dust toxic syndrome.

AIMS: Episodes of serious work related health problems resembling organic dust toxic syndrome (ODTS) in workers of a grass seed quality inspection laboratory prompted the authors to study personal endotoxin exposure levels in this facility and in the agricultural seed processing industry. In addition, microbial and inflammatory characteristics of agricultural seeds were studied. METHODS: The authors assessed inhalable dust and endotoxin levels in 101 samples from 57 workers in grass, cereal, and vegetable seed plants who were handling mainly grass seeds as bulk product, and horticulture seeds in smaller quantities. Additionally, real-time dust exposure was measured using a DataRAM monitor in 12 grass seed workers to obtain more information on exposure patterns during specific tasks. Endotoxin concentrations in seed extracts were determined by LAL assay and seed samples were analysed by scanning electron microscopy. Release of inflammatory cytokines was measured in supernatants of whole blood samples stimulated with lipopolysaccharide (LPS) or agricultural seed extracts in a human whole blood assay (WBA). RESULTS: Endotoxin concentrations in personal samples were high (geometric mean 1800 EU/m3), particularly in the grass seed quality inspection lab where endotoxin levels up to 274 000 EU/m3 were measured. The recommended health based endotoxin exposure limit of 50 EU/m3 was amply exceeded in almost all personal samples. Job tasks dumping and mixing were associated with highest dust and endotoxin exposures, which was confirmed by real-time measurements. Microbial infestation was found in almost all seed samples. WBA results showed that most seed extracts were capable of inducing a pronounced dose dependent cytokine release. CONCLUSIONS: Workers handling grass, cereal, or vegetable seeds are at risk of exposure to high levels of endotoxin containing seed dust. Occupational exposure to inhalable agricultural seed dust can induce inflammatory responses, and is a potential cause of ODTS.

Agricultural Workers' Diseases↗

PubMed2005

The effects of intervention with local electrostatic air cleaners on airborne dust and the health of office employees.

UNLABELLED: The aim of this intervention study was to identify any health improvements in the upper and lower airways of office workers after the installation of local electrostatic air cleaners. Eighty persons with airways symptoms were recruited and randomly assigned to an intervention or control group. Half of the air cleaners had a non-functioning electrostatic unit. Both participants and field researchers were blinded to the group status. Subjective symptoms were recorded using a questionnaire, and indexes calculated for general, irritation and skin symptoms. Objective respiratory health indicators were recorded, with acoustic rhinometry and peak expiratory flow (PEF) meters. In the intervention group there was a decrease in mean dust concentration from 65 to 35 microg/m(3), and a reduction from 57 to 47 microg/m(3) in the control group (P < 0.05 for difference in decline). The reduction was observed for all particles sizes. The irritation and general symptom indices decreased in both groups, but there was no improvement in the intervention group, compared with the control group. Median PEF increased 3 ml/s in the intervention group, and decreased 4 ml/s in the control group. The adjusted odds ratio for an increase above the 70th percentile was 5.7 (95% CI 1.0-32). PRACTICAL IMPLICATIONS: Electrostatic air cleaners can reduce the dust concentration effectively in the office environment. Small, medium and large sized particles can be reduced by approximately 50%, relatively most effectively for the respirable particles. However, the air cleaners tested in this study produced an annoying fan noise. Cleaning efficiency and noise data should be given consideration before installation. This experimental field study suggests that office workers with airways symptoms may benefit from installation of local electrostatic air cleaners.

Adult↗

PubMed2005

Short term changes in lung function, leukocytosis in blood, and lachrymal fluid among bacterial single cell protein workers after an episode with high exposure to endotoxins.

AIMS: To study possible effects of endotoxin exposure among bacterial single cell protein workers on pulmonary function, blood parameters, and lachrymal fluid before and after a work shift. METHODS: The study included 23 men and five women who were examined at the start and at the end of a work shift. Most workers performed a task with unusually high exposure levels. Twelve of the workers were re-examined the day after. The workers were divided into three exposure groups: production workers with the highest assumed exposure levels (n = 18), engineers (n = 5), and clerks (n = 2). The median endotoxin level during a work shift was 34000 EU/m3 in the high exposure group (range 3300-89000 EU/m3 ), 11000 EU/m3 (range 350-27000 EU/m3) among the engineers, and 180 EU/m3 (range 60-300 EU/m3) for the clerks. The workers answered a questionnaire about work related symptoms. Assessment of lung function included dynamic lung volumes and flows. The blood analysis included cell count of leukocytes and mediators of inflammation, fibrinogen, interleukin-6 (IL-6), D-dimer, and C-reactive protein (CRP). Cells in lachrymal fluid were counted with a microscope. RESULTS: The forced vital capacity (FVC) changed significantly (p<0.05) from 5.34 l (SD 0.9) to 5.25 l (SD 0.9) and forced expired volume in one second (FEV1) from 4.15 l (SD 0.7) to 4.07 l (SD 0.7) during the work shift. The leukocytes increased significantly (p<0.05) from 6.9 10(9)/l (SD 1.2) to 7.7 10(9)/l (SD 1.5) and IL-6 from 1.5 ng/l (SD 0.6) to 3.31 ng/l (SD 2.7). Except for fibrinogen, which had a borderline increase and PEF that decreased, the parameters were normalised the day after. Four of the workers had an increase of neutrofile granulocytes in the lachrymal fluid during the shift. There was a significant association between the endotoxin concentration and decrease of FEV1 despite the use of powered respirators. CONCLUSIONS: During a work shift with unusual high levels of endotoxins at a plant manufacturing bacterial single cell protein the results show that FVC and FEV1 were reduced. Mediators of inflammation increased along with leucocytosis in blood and lachrymal fluid among the workers.

Adult↗

PubMed2004

Cumulative exposure to dust and gases as determinants of lung function decline in tunnel construction workers.

AIMS: To study the relation between lung function decrease and cumulative exposure to dust and gases in tunnel construction workers. METHODS: A total of 651 male construction workers (drill and blast workers, tunnel concrete workers, shotcreting operators, and tunnel boring machine workers) were followed up by spirometric measurements in 1989-2002 for an average of six years. Outdoor concrete workers, foremen, and engineers served as a low exposed referent population. RESULTS: The between worker component of variability was considerably reduced within the job groups compared to the whole population, suggesting that the workers within job groups had similar exposure levels. The annual decrease in FEV1 in low-exposed non-smoking workers was 21 ml and 24 ml in low-exposed ever smokers. The annual decrease in FEV1 in tunnel construction workers was 20-31 ml higher than the low exposed workers depending on job group for both non-smokers and ever smokers. After adjustment for age and observation time, cumulative exposure to nitrogen dioxide showed the strongest association with a decrease in FEV1 in both non-smokers, and ever smokers. CONCLUSION: Cumulative exposure to nitrogen dioxide appeared to be a major risk factor for lung function decreases in these tunnel construction workers, although other agents may have contributed to the observed effect. Contact with blasting fumes should be avoided, diesel exhaust emissions should be reduced, and respiratory devices should be used to protect workers against dust and nitrogen dioxide exposure.

Adult↗

PubMed2004

Do farming exposures cause or prevent asthma? Results from a study of adult Norwegian farmers.

BACKGROUND: A protective effect of endotoxin exposure on atopy and asthma in farmers' children has been postulated. Studies of adult farmers have shown conflicting results but often lack exposure data. The prevalence of asthma in farmers with different exposure levels to microbial agents and irritant gases was compared. METHODS: Atopy was defined as a positive response to multiple radioallergosorbent tests (RAST) with a panel of 10 common respiratory allergens, and asthma was ascertained by a questionnaire using a stratified sample (n = 2169) of a farming population from south-eastern Norway. Exposure of farmers to total dust, fungal spores, bacteria, endotoxins, and ammonia was assessed by exposure measurements. RESULTS: The prevalence of asthma was 3.7% for physician diagnosed asthma and 2.7% for current asthma. The prevalence of atopy was 14%, but most asthmatic subjects were non-atopic (80%). Compared with farmers without livestock, (1) asthma was significantly higher in cattle farmers (OR(adj) 1.8, 95% CI 1.1 to 2.8) and pig farmers (OR(adj) 1.6, 95% CI 1.0 to 2.5), (2) non-atopic asthma was significantly higher in pig farmers (OR(adj) 2.0, 95% CI 1.2 to 3.3) and in farmers with two or more types of livestock (OR(adj) 1.9, 95% CI 1.1 to 3.3), and (3) atopic asthma was less common in farmers with two or more types of livestock (OR(adj) 0.32, 95% CI 0.11 to 0.97). Exposure to endotoxins, fungal spores, and ammonia was positively associated with non-atopic asthma and negatively associated with atopic asthma. No associations were found with atopy. CONCLUSIONS: Exposure to endotoxins and fungal spores appears to have a protective effect on atopic asthma but may induce non-atopic asthma in farmers.

Adult↗

PubMed2003

Symptoms prevalence among office employees and associations to building characteristics.

A cross-sectional study was performed in eight companies, comprising 32 buildings without previously recognized indoor air problems. Engineers filled in a technical questionnaire on building characteristics, floor surface materials, ventilation, cleaning procedures, heating and cooling. A total of 3562 employees returned questionnaires on individual factors, workload, perceived physical work environment, allergy and symptoms. Frequent symptoms were feeling of fatigue or heavy-headedness, eye irritation, and dry facial skin. Women reported symptoms more frequently than men. Employees with allergy had a 1.8-2.5 times risk of reporting a high score for general, skin, or mucosal symptoms. The risk of a high symptom score increased with daily visual display unit (VDU) work time. Passive smoking and psychosocial load were also relatively strong predictors of symptoms. Weekly cleaning as compared with a frequency of cleaning two to four times a week increased the risk of symptoms. Adjusted odds ratio for a high general symptoms score from infrequent cleaning was 1.5 (95%CI 1.1-2.0). A high ventilation flow or central ventilation unit filter EU7 vs. EU8 seemed to be associated with an increased risk of general symptoms. Absence of local temperature control increased the risk of mucosal symptoms.

Adult↗

PubMed2003

Upper airway inflammation in waste handlers exposed to bioaerosols.

AIMS: To examine work associated upper airway inflammation in 31 waste handlers, and to correlate these findings with personally monitored exposure to different bioaerosol components. METHODS: Cell differentials, interleukin 8 (IL-8), myeloperoxidase (MPO), and eosinophilic cationic protein (ECP) were examined in NAL (nasal lavage), and swelling of the nasal mucosa was determined by acoustic rhinometry before work start on Monday and the following Thursday. Bioaerosol exposure was determined by personal full shift exposure measurements on Monday, Tuesday, and Wednesday and analysed for total bacteria, fungal spores, endotoxin, and beta(1-->3)-glucans. RESULTS: The increased percentage of neutrophils from Monday (28%) to Thursday (46%) correlated with increases in ECP (r(S) = 0.71, p < 0.001) and MPO (r(S) = 0.38, p < 0.05), and showed a close to significant correlation with nasal swelling (r(S) = -0.55, p = 0.07). The Thursday levels of neutrophils, MPO, and IL-8 were associated with the exposure to fungal spores (range 0-2.0 x 10(6)/m(3)) and endotoxin (range 4-183 EU/m(3)) measured the day before, and the median exposure to beta(1-->3)-glucans (range 3-217 ng/m(3)), respectively (r(S) = 0.47-0.54, p < 0.01). Swelling of the nasal mucosa was associated with the fungal spore and beta(1-->3)-glucan exposure (r(S) = 0.58-0.59, p < 0.05). CONCLUSION: These results are based on a relatively small population, and conclusions must be drawn with care. The results suggested that a moderate exposure to fungal spores, endotoxins, and beta(1-->3)-glucans during waste handling induced upper airway inflammation dominated by neutrophil infiltration and swelling of the nasal mucosa.

Adolescent↗

PubMed2003

Airway inflammation in waste handlers exposed to bioaerosols assessed by induced sputum.

Work-associated lower airway inflammation in waste collectors was examined by induced sputum and correlated with the bioaerosol exposure. Organic waste collectors (n=25) underwent induced sputum collection and spirometry before work on Monday and the following Thursday. Total cells, cell differentials, interleukin (IL)-8 and eosinophilic cationic protein were determined. Personal full-shift exposure measurements were performed Monday, Tuesday and Wednesday and analysed for total bacteria, fungal spores, endotoxins and beta(1-3)-glucans. The percentage of neutrophils (46-58%) and the IL-8 concentration (1.1-1.4 ng x mL(-1)) increased from Monday to Thursday. Forced expiratory volume in one second (FEV1) was significantly reduced on Thursday, and the decrease in FEV1/forced vital capacity correlated with the increase in the percentage of neutrophils. The median exposure to endotoxin (range 7-180 EU x m(-3)) and beta(1-3)-glucan (range 5-220 ng x m(-3)) was correlated with the increase in IL-8. Bioaerosol exposure during waste collection induced an inflammatory response in the lower airways, characterised by neutrophils and interleukin-8 secretion, that influenced the lung function. The inflammatory response was related to microbial components in the bioaerosol and was more pronounced for endotoxin than beta(1-3)-glucan exposure. No associations were found for mould spores or bacteria.

Aerosols↗

PubMed2001

Organic dust-related respiratory and eye irritation in Norwegian farmers.

BACKGROUND: Information on exposure to organic dust and work-related symptoms in farmers is sparse. METHODS: An exposure study was nested in a survey of 8,482 farmers and spouses. Task-related respiratory and eye symptoms were recorded by questionnaire. Personal exposure to total dust, fungal spores, bacteria, endotoxins, and ammonia during 12 different tasks was measured in a random sample of 127 farms (288 measurements). RESULTS: The prevalence of work-related symptoms occurring "often" was 31% and "seldom" 35%. Specific tasks provoking symptoms were reported by 5-55% of the farmers. Task mean exposures ranged from 0.04 to 2 mg dust/m(3), 0.02 x 10(6) to 2 x 10(6) fungal spores/m(3), 0.2 x 10(6) to 48 x 10(6) bacteria/m(3), 0.5 x 10(3) to 28 x 10(3) endotoxin units/m(3), and 0 to 8 ppm ammonia. Task mean exposure levels were positively correlated with task-specific symptom prevalences for total dust, fungal spores, and endotoxins but not for bacteria and ammonia. CONCLUSION: Work-related symptoms are common in farmers and are associated with exposure to total dust, fungal spores, and endotoxins.

Adult↗

PubMed2001

Ochratoxin A in airborne dust and fungal conidia.

Farm workers are often exposed to high concentrations of airborne organic dust and fungal conidia, especially when working with plant materials. The purpose of this investigation was to study the possibility of exposure to the mycotoxin ochratoxin A (OTA) through inhalation of organic dust and conidia. Dust and aerosol samples were collected from three local cowsheds. Aerosol samples for determination of total conidia and dust concentrations were collected by stationary sampling on polycarbonate filters. Total dust was analysed by gravimetry, and conidia were counted using scanning electron microscopy. A method was developed for extraction and determination of OTA in small samples of settled dust. OTA was extracted with a mixture of methanol, chloroform, HCl, and water, purified on immunoaffinity column, and analysed by ion-pair HPLC with fluorescence detection. Recovery of OTA from spiked dust samples (0.9-1.0 microg/kg) was 74% (quantitation limit 0.150 microg/kg). OTA was found in 6 out of 14 settled dust samples (0.2-70 microg/kg). The total concentration of airborne conidia ranged from < 1.1 x 10(4) to 3.9 x 15(5) per m3, and the airborne dust concentration ranged from 0.08 to 0.21 mg/m3. Conidia collected from cultures of Penicillium verrucosum and Aspergillus ochraceus contained 0.4-0.7 and 0.02-0.06 pg OTA per conidium, respectively. Testing of conidial extracts from these fungi in a Bacillus subtilis bioassay indicated the presence of toxic compounds in addition to OTA. The results show that airborne dust and fungal conidia can be sources of OTA. Peak exposures to airborne OTA may be significant, e.g., in agricultural environments.

Agriculture↗

PubMed2001

Cumulative exposure to dust causes accelerated decline in lung function in tunnel workers.

OBJECTIVES: To examine whether underground construction workers exposed to tunnelling pollutants over a follow up period of 8 years have an increased risk of decline in lung function and respiratory symptoms compared with reference subjects working outside the tunnel atmosphere, and relate the findings to job groups and cumulative exposure to dust and gases. METHODS: 96 Tunnel workers and a reference group of 249 other heavy construction workers were examined in 1991 and re-examined in 1999. Exposure measurements were carried out to estimate personal cumulative exposure to total dust, respirable dust, alpha-quartz, oil mist, and nitrogen dioxide. The subjects answered a questionnaire on respiratory symptoms and smoking habits, performed spirometry, and had chest radiographs taken. Radiological signs of silicosis were evaluated (International Labour Organisation (ILO) classification). Atopy was determined by a multiple radioallergosorbent test (RAST). RESULTS: The mean exposure to respirable dust and alpha-quartz in tunnel workers varied from 1.2-3.6 mg/m3 (respirable dust) and 0.019-0.044 mg/m3 (alpha-quartz) depending on job task performed. Decrease in forced expiratory volume in 1 second (FEV1) was associated with cumulative exposure to respirable dust (p<0.001) and alpha-quartz (p=0.02). The multiple regression model predicted that in a worker 40 years of age, the annual decrease in FEV1 would be 25 ml in a non-exposed non-smoker, 35 ml in a non-exposed smoker, and 50-63 ml in a non-smoking tunnel worker (depending on job). Compared with the reference group the odds ratio for the occurrence of new respiratory symptoms during the follow up period was increased in the tunnel workers and associated with cumulative exposure to respirable dust. CONCLUSIONS: Cumulative exposures to respirable dust and alpha-quartz are the most important risk factors for airflow limitation in underground heavy construction workers, and cumulative exposure to respirable dust is the most important risk factor for respiratory symptoms. The finding of accelerated decline in lung function in tunnel workers suggests that better control of exposures is needed.

Adult↗

PubMed2001

Short term exposure to airborne microbial agents during farm work: exposure-response relations with eye and respiratory symptoms.

OBJECTIVES: Exposure to high levels of non-infectious microbial agents is recognised as a cause of respiratory disease in working populations, but except for endotoxins, little is known about exposure-response relations. As these effects do not depend on viability, exposure to non-viable microbial agents is important. Various methods not based on microbial cultures were explored to study the complex microbial exposure of farmers and associations with acute symptoms during work. METHODS: Airborne exposure was measured when farmers carried out specific tasks. Fungal spores, bacteria, endotoxins, beta(1-->3)-glucans, fungal antigens specific for Penicillium and Aspergillus species, and mites were measured by methods not based on microbial cultures. Also silica, inorganic and organic dust, ammonia, hydrogen sulphide, and nitrogen dioxide were measured. Respiratory, and nose and eye symptoms experienced during measurements were recorded by a short questionnaire. Both univariate and multivariate statistical analyses were applied to assess the relations between exposure and acute symptoms. RESULTS: 106 Farmers and their spouses participated in this study. Prevalences of work related symptoms were: wheezing 3%; chest tightness 7%; cough 14%; eye symptoms 18%; and nose symptoms 22%. Prevalence ratios for nose and eye symptoms were 4-8 after exposure to 20-500x10(3) fungal spores/m(3) and higher, and a prevalence ratio for cough was 4 after exposure to 500-17,000x10(3) fungal spores/m(3). Nose symptoms were also associated with exposure to silica with prevalence ratios of 4-6 after exposure to 0.015-0.075 mg /m(3) and higher. CONCLUSIONS: Farmers had a high occurrence of symptoms of the nose and eyes as well as cough during work. These symptoms were associated in a dose dependent manner with exposure to fungal spores. Nose symptoms were also associated with exposure to silica.

Aged↗

PubMed2001

Effects of electric field reduction in visual display units on skin symptoms.

OBJECTIVES: This study investigated the facial skin complaints of office workers before and after the static electric fields of a visual display unit were reduced. METHODS: On the basis of a screening survey of 4556 office workers in 11 companies, 120 of 227 subjects reporting facial skin complaints were randomly selected to this double blind intervention study. Antistatic measures were used to reduce the static electric fields of the visual display unit in the intervention group but not in the control group, which worked with a visual display unit resembling that of the intervention group. Electric fields, dust concentration, health complaints, and psychological behavior tests were recorded before and after the intervention. RESULTS: The intervention group reported statistically significantly fewer facial skin complaints than the control group. In the intervention group, among those with an office dust concentration of >58 microg/m3, a median reduction of 1.5 skin index points (scale 0-8) was achieved, whereas there was no change in the control group. In the regression model "group category" was still a significant variable after control for background factors. In addition, further linear regression analyses indicated that several static electric field parameters were predictors of the skin complaint reduction. CONCLUSIONS: This field trial indicates that removing static electric fields from visual display units can probably help reduce the facial skin complaints of workers in offices with high dust concentrations.

Adult↗

PubMed2001

Effects of blasting fumes on exposure and short-term lung function changes in tunnel construction workers.

OBJECTIVES: This study attempts to determine the effects of exposure to blasting fumes and its influence on the lung function of tunnel workers. METHODS: Two groups of tunnel workers, one using ammonium nitrate fuel oil (ANFO) as the explosive and the other using size-sensitized emulsion (SSE), with 24 workers per group, were compared with a reference group (N=34) with low exposure. Spirometry was used to determine lung function. Personal exposure to total and respirable dust, alpha-quartz, volatile organic compounds, oil mist and vapors, formaldehyde, nitrogen dioxide, and carbon monoxide was measured. RESULTS: The ANFO workers were more exposed to all the agents than the reference group and more exposed than the SSE workers to all the agents except total dust and carbon monoxide. The SSE workers were significantly more exposed to total dust and alpha-quartz than the reference group. High peak exposures to nitrogen dioxide (up to 20 ppm) occurred for the ANFO workers in contrast to the SSE workers, whose exposure did not exceed 2 ppm. The lung function of the ANFO workers significantly decreased by 3% for forced vital capacity, 7% for forced expiratory volume in 1 second, and 8% for forced expiratory flow rate from 25% to 75% of the forced vital capacity over the 11-day period. The changes were reversible. There were no significant changes among the SSE workers and the outdoor workers. The ANFO workers had a significant decrease in FEV1.0 when compared with both the SSE and outdoor workers. CONCLUSIONS: Tunnel workers using ANFO explosive show a temporary reduction in lung function, whereas those using SSE do not. The most likely explanation for the observed changes is peak exposures to nitrogen dioxide.

Adult↗

PubMed2001

Recognition errors in the quantification of micro-organisms by fluorescence microscopy.

OBJECTIVES: An interlaboratory comparison of fluorescence microscopic counting of micro-organisms was carried out to assess counting errors in the measurement of micro-organisms in bioaerosols generated during handling of municipal waste. METHODS: Series of 27 replicate samples were collected in the work environment with a modified field exposure chamber. The preparation methods of three Scandinavian laboratories were compared. Four microscopists from these laboratories performed the counts which were also compared. Duplicate counting of identical microscopic fields allowed the assessment of recognition errors. RESULTS: The field exposure chamber collected replicate samples with a relative standard deviation of 5% when particles < or = 15 microm aerodynamic diameter were collected. Storage time of 40-200 days had no significant influence on the total micro-organism count. Differences between preparation methods were from 2 to 35% for bacteria, and from 15 to 35% for fungal spores when samples were analysed in Oslo; the results for fungal spore counts were significantly different (P < 0.01). These differences were not confirmed when samples were analysed in Umeå, Copenhagen and Oslo using those laboratories methods. These results can be explained by less efficient redispersion of aggregates when the Umeå and Copenhagen methods were recreated in Oslo yielding a greater number of innumerable aggregates. Differences between microscopists were minor for fungal spores (2-12%) but substantial for bacteria (4-53%). A major source of error was the recognition of bacteria which had a relative standard deviation (rsd) of 37% although a lower size limit of 0.75 microm was adopted for counting of bacteria. Fungal spores were recognised with much better precision (rsd 9%). CONCLUSIONS: Recognition errors of bacteria may be substantial and more specific fluorochromes are needed for fluorescence microscopic counting of micro-organisms.

Analysis of Variance↗

PubMed1999

Classification of particles from the farm environment by automated sizing, counting and chemical characterisation with scanning electron microscopy-energy dispersive spectroscopy.

About 60,000 particles in 288 aerosol samples collected during farm work have been characterised with automated particle analysis using scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS). Based on EDS-analysis of materials with known composition (potato flour, alpha-quartz, K-feldspar and beta-wollastonite), criteria were developed for classification of particles as: (1) organic, (2) silicon-rich (silica), and (3) other inorganic particles. The reproducibility of the relative mass proportions in dust samples collected during farm work was 0.078 when approximately 200 particles were characterised per sample. Field samples from the farm environment showed clear differences in composition. Generally, inorganic particles dominated the particle mass. The proportion of the organic particle mass was highest for tending of swine and poultry, 55 and 38% respectively. Silica particles amounted to 10 to 20% of the total mass during handling crops, e.g. grain, straw, hay, potatoes, and onions. It seems likely that the results can be used in etiologic studies, but further validation would be needed for quantitative purposes.

Aerosols↗

PubMed1998

Does the mycotoxin citrinin function as a sun protectant in conidia from Penicillium verrucosum.

Our results demonstrate high concentrations of the UV absorbing mycotoxin citrinin in the outer layer of spores from three citrinin-producing strains of Penicillium verrucosum, which is released in an aqueous environment. An important function of the toxin could be to act as a sun protectant in order to create favorable conditions during the initial germination process. When spores from these strains of P. verrucosum were examined by confocal microscopy, a clearly visible fluorescent layer associated with the cell wall was observed. The strains were grown on agar plates, and the mycelial mat was washed with saline. This suspension contained at least 95% of the spores and particulate material, which was removed by filtration after counting the conidia. An aliquot of this filtrate was extracted and citrinin was purified by high pressure liquid chromatography. The absorbance at 319 nm was used to calculate the amount of UV absorbing material released from the spores. Based on the spore numbers in the suspension of the saline extract, we estimated that this material released was 1.4-4.1 pg per spore or 8-24% of the spore weight. Citrinin (and minor amounts of ochratoxin A and some other unidentificable fluorescent compounds) were observed in the filtrate when subjected to thin layer chromatography.

Journal Article↗