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PubMed2003

The effects of wood dusts on the redox status and cell death in mouse macrophages (RAW 264.7) and human leukocytes in vitro.

Wood dusts are classified as carcinogenic to humans and also produce other toxic, allergic, and acute effects in woodworkers. However, little is known about causative agents in wood dusts and their mechanisms of action. The effects of different tree species and particle size for biological activity were studied. The differences in the production of reactive oxygen species (ROS) and cell death (necrotic and apoptotic) between mouse macrophage (RAW 264.7) cells and human polymorphonuclear leukocytes (PMNL) for pine, birch, and beech dust exposures were investigated in vitro. The pine and birch dust exposure (1-100 microg/ml) produced concentration-dependent ROS production in both the cells, which was one order of magnitude higher with pine dust. The ROS production was faster in human PNML than murine RAW cells. The higher concentrations (500 and/or 1000 microg/ml) decreased ROS formation. With pine and birch dust exposure, this was probably due to the necrotic cell death. The pine dust concentrations of 500 and 1000 microg/ml were cytotoxic to human PMNL. The beech dust exposure activated the ROS production and decreased the cell viability only at the highest concentrations, being least potent of the three dusts. A sign of the apoptotic cell death in the murine RAW cells was observed at the pine dust concentration of 100 microg/ml. The exposure to the birch and beech dusts with a smaller particle size (<5 microm) produced greater ROS production than exposure to the corresponding dust with a wide range of particle sizes. However, changing the particle size did not affect the cell viability. The results indicate that the type of wood dust (tree species and possibly particle size) has a significant impact on the function and viability of phagocytic cells.

Animals↗
PubMed1992

Influence of mineral dust surface chemistry on eicosanoid production by the alveolar macrophage.

It has been suggested that radicals on the surface of dust particles are key chemical factors in the pathophysiology that results from the occupational inhalation of coal and silica dust. In addition, oxygenated derivatives of arachidonic acid (eicosanoids) have been implicated as important biochemical mediators of mineral dust-induced lung disease through their role in bronchial and vascular smooth muscle reactivity, inflammation, and fibrosis. Therefore, we assessed eicosanoid production by the rat alveolar macrophage (AM) exposed in vitro to mineral dusts with varying surface chemical characteristics in order to determine if radicals associated with the mineral dust could influence the production of proinflammatory mediators in the lung environment. Primary cultures of rat AM were exposed to freshly fractured or "stale" bituminous coal dust, as well as untreated silica or silica calcined to 500 and 1100 degrees C. Prostaglandin E2 (PGE2), thromboxane A2 (TXA2), and leukotriene B4 (LTB4) levels in incubation medium were determined by specific radioimmunoassay. When AM were exposed to freshly fractured coal dust, PGE2 production was markedly increased. In contrast, exposure of AM to "stale" dust significantly reduced PGE2 production. Exposure of AM to freshly fractured coal dust resulted in a significant increase in production by AM, while exposure to stale coal dust did not influence AM TXA2 production. Neither "fresh" nor "stale" coal dust had any effect on LTB4 production. In vitro exposure of AM to untreated silica resulted in a significant increase in TXA2 PGE2, TXA2, and LTB4 production compared with control. However, exposure of AM to silica calcined to 1100 degrees C resulted in eicosanoid levels that were not significantly different from control. These effects were still apparent 8 wk after calcination of the silica particles. Silica was a more potent activator of AM eicosanoid production than was coal, and amorphous fumed silica was a more potent activator of AM eicosanoid production than was crystalline silica. These findings suggest that radicals associated with respirable coal and silica particles may play a key role in the ability of mineral dust to activate AM eicosanoid production and therefore may be important in the pathophysiological consequences of occupational mineral dust inhalation.

Animals↗
PubMed2004

Exposure to and acute effects of medium-density fiber board dust.

The goals of this study were (1) to investigate workers' exposure to medium-density fiber (MDF) dust (inhalable dust, particle size),formaldehyde, and volatile organic compounds; (2) to study the possible inflammatory nasal reactions caused by exposure to MDF board dust; and (3) to determine the occurrence of irritative symptoms among exposed workers. Nasal lavage fluid was analyzed for cytokines and nitric oxide/nitrite. and inflammatory cells were counted. The time-weighted average of MDF dust was 1.4 mg/m3 in the workers' breathing zones. MDF board dust was composed mainly of particles exceeding 10 microm in diameter. The MDF board dust released formaldehyde in concentration of about 1000 microg/g when extracted with water for 6 hours at 37 degrees C. The cell counts and cytokine levels of the nasal lavage fluid samples did not show statistically significant differences between the workers exposed to MDF board dust and those exposed to other wood dusts. Nevertheless, two MDF-exposed workers had a considerable increase in the proportion of eosinophils and cytokine levels. Several workers exposed to MDF and wood dusts experienced nasal, eye, and skin symptoms at the end of a work shift. Both exposed groups had significantly more nasal symptoms, although the median dust level was only 1.2 mg/m3, considerably less than the occupational exposure limit for wood dust in Finland. Nasal symptoms were more frequent among workers exposed to MDF board dust and did not correlate with smoking. Our results suggest that the occupational exposure limit of 5 mg/m3 is probably too high for MDF board dust.

Adult↗
PubMed1995

House dust mite fauna in Thailand.

House dust mites have been shown to be the most important source of allergen in Thailand. The results of our initial mite survey were in conflict with previous data reported 20 years ago. To evaluate the current condition of mite fauna in Thailand, we conducted a larger scale survey of house dust mites in dusts from three different parts of the country. A total of 630 mattress dust samples was collected from various types of housing from central, northern and northeastern parts of Thailand. House dust mites were identified and enumerated by standard techniques and 388 dust samples were analysed further for group I antigen by a two-site monoclonal antibody enzyme-linked immunosorbent assay. House dust mites were identified in 555/630 (88.1%) of dust samples collected; 27.6% of these 555 samples contained over 100 mites per gram of fine dust. Dermatophagoides pteronyssinus was the most abundant species found with a mean count of 87.2 mites per gram of dust (range 1-1460). Group I antigen was detected in 380/388 (97.9%) samples analysed and 330 of which (86.8%) contained over 2 micrograms/gm of group I antigen. The highest density of mites was found in dusts from northern Thailand whereas dusts with highest amount of antigen were those collected from the northeastern part. Some degree of correlation between mite count and mite allergen was observed (r2 = 0.133, P < 0.001). No significant difference in the mite count and mite allergen was found among various types of housings. House dust mites are the source of allergens ubiquitously found all over Thailand.(ABSTRACT TRUNCATED AT 250 WORDS)

Allergens↗
PubMed2006

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

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

Air Pollution, Indoor↗
PubMed2006

Exposure to microbial components and allergens in population studies: a comparison of two house dust collection methods applied by participants and fieldworkers.

Dust collection by study participants instead of fieldworkers would be a practical and cost-effective alternative in large-scale population studies estimating exposure to indoor allergens and microbial agents. We aimed to compare dust weights and biological agent levels in house dust samples taken by study participants with nylon socks, with those in samples taken by fieldworkers using the sampling nozzle of the Allergology Laboratory Copenhagen (ALK). In homes of 216 children, parents and fieldworkers collected house dust within the same year. Dust samples were analyzed for levels of allergens, endotoxin, (1-->3)-beta-D-glucans and fungal extracellular polysaccharides (EPS). Socks appeared to yield less dust from mattresses at relatively low dust amounts and more dust at high dust amounts than ALK samples. Correlations between the methods ranged from 0.47-0.64 for microbial agents and 0.64-0.87 for mite and pet allergens. Cat allergen levels were two-fold lower and endotoxin levels three-fold higher in socks than in ALK samples. Levels of allergens and microbial agents in sock samples taken by study participants are moderately to highly correlated to levels in ALK samples taken by fieldworkers. Absolute levels may differ, probably because of differences in the method rather than in the person who performed the sampling. Practical Implications Dust collection by participants is a reliable and practical option for allergen and microbial agent exposure assessment. Absolute levels of biological agents are not (always) comparable between studies using different dust collection methods, even when expressed per gram dust, because of potential differences in particle-size constitution of the collected dust.

Air Pollutants↗
PubMed1996

Wool and grain dusts stimulate TNF secretion by alveolar macrophages in vitro.

OBJECTIVE: The aim of the study was to investigate the ability of two organic dusts, wool and grain, and their soluble leachates to stimulate secretion of tumour necrosis factor (TNF) by rat alveolar macrophages with special reference to the role of lipopolysaccharide (LPS). METHODS: Rat alveolar macrophages were isolated by bronchoalveolar lavage (BAL) and treated in vitro with whole dust, dust leachates, and a standard LPS preparation. TNF production was measured in supernatants with the L929 cell line bioassay. RESULTS: Both wool and grain dust samples were capable of stimulating TNF release from rat alveolar macrophages in a dose-dependent manner. The standard LPS preparation caused a dose-dependent secretion of TNF. Leachates prepared from the dusts contained LPS and also caused TNF release but leachable LPS could not account for the TNF release and it was clear that non-LPS leachable activity was present in the grain dust and that wool dust particles themselves were capable of causing release of TNF. The role of LPS in wool dust leachates was further investigated by treating peritoneal macrophages from two strains of mice, LPS responders (C3H) and LPS non-responders (C3H/HEJ), with LPS. The non-responder mouse macrophages produced very low concentrations of TNF in response to the wool dust leachates compared with the responders. CONCLUSIONS: LPS and other unidentified leachable substances present on the surface of grain dust, and to a lesser extent on wool dust, are a trigger for TNF release by lung macrophages. Wool dust particles themselves stimulate TNF. TNF release from macrophages could contribute to enhancement of inflammatory responses and symptoms of bronchitis and breathlessness in workers exposed to organic dusts such as wool and grain.

Animals↗
PubMed1998

Induction of IL-8 production in human alveolar macrophages and human bronchial epithelial cells in vitro by swine dust.

BACKGROUND: Exposure to swine dust causes an intense airway inflammation with increased levels of interleukin 8 (IL-8) and predominantly neutrophils in the nasal and bronchoalveolar lavage fluids of healthy human subjects. It is not clear which components in the swine house environment are responsible for the airway reaction. The aim of the present study was to evaluate and compare the effect in vitro of swine dust components on human alveolar macrophages and bronchial epithelial cells. METHODS: Normal human bronchial epithelial cells (NHBE), human pulmonary epithelial carcinoma cell line (A549), and human alveolar macrophages were stimulated with swine dust, lipopolysaccharides (LPS; present in Gram negative bacteria), grain dust (swine feed components), and glucans (a structural component of fungi) in a dose response manner (1-100 micrograms/ml). RESULTS: Swine dust at a concentration of 100 micrograms/ml increased IL-8 production 20 fold in NHBE cells, 28 fold in A549 cells, and 15 fold in macrophages. LPS (100 micrograms/ml) stimulated all three cell types significantly, in macrophages to the same extent as swine dust, but in NHBE and A549 cells swine dust was 5-8 times as potent. Grain dust (100 micrograms/ml) had no effect in A549 cells and macrophages but not NHBE cells. Both glucans and grain dust were weaker stimuli than swine dust and LPS. The LPS content of swine dust solution was 2.16 (0.2) ng/100 micrograms and of grain dust was 0.53 (0.04) ng/100 micrograms. CONCLUSIONS: Swine dust is a strong stimulus for IL-8 production in both bronchial epithelial cells and human alveolar macrophages, whereas LPS has different potency in these cells.

Animals↗
PubMed1986

Microscopical comparison of cotton, corn, and soybean dusts.

Specialized analytical methods are required for identification of components of agricultural dusts such as those generated in harvesting, transportation, storage, and processing of cotton, corn, and soybeans. The larger particles and trash components of the dusts can often be identified visually or with the aid of an optical microscope (OM). The respirable portion of the dust, that which causes lung dysfunction, retains few structural features for identification. Electron microscopy and X-ray microanalysis, together with special optical microscopical techniques, can be used to characterize these microdusts. Combination studies with scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analysis of cotton dusts have shown the presence of mineralogical particles probably of a soil origin and materials that can be associated with plant parts. Even in screened and filtered cotton dusts, fibrillar fragments are usually present due to their ability to penetrate openings the size of their diameters. The corn and soybean dusts studied were different from the cotton dust in that the large fibrillar component of the cotton dust was absent in the screened grain dusts. However, these dusts consisted of structurally unrecognizable particles that appeared similar to those found in cotton dust. In addition they contained many spheroid particles identified as starch. Dusts from all three sources were found to agglomerate into larger particles, some of which were still less than 10 micron. This agglomeration could confuse the instrumental measurement of dust particle size.

Dust↗
PubMed1993

The effects of inhalation of grain dust extract and endotoxin on upper and lower airways.

To characterize the short-term effects of grain dusts on pulmonary function, mucosal inflammation, and systemic responses, four women and three men inhaled nebulized corn and soybean dust extracts, endotoxin diluted with Hanks' balanced salt solution (HBSS), and HBSS. Subjects were volunteers recruited via newspaper advertisement and were required to be healthy, nonasthmatic, nonatopic never-smokers. The mean age was 26.9 years (range, 19 to 36 years). Using a randomized, double-blind, crossover design, each subject was challenged with each of the 4 substances with at least 10 days between challenges. Serial spirometry, peripheral blood leukocyte and differential cell counts, and 24-h postchallenge nasal lavages were performed. Extracts were produced by mixing 3 g of the corn or soybean dust with 30 ml HBSS followed by shaking for 60 min, centrifugation, then filter sterilization. The endotoxin solution was produced by mixing lyophilized Escherichia coli endotoxin (serotype 0111:B4) with HBSS to attain a final concentration of 7 mg/L, which was the same as the concentration of endotoxin in both grain dust solutions. The pH of all solutions and unmixed HBSS was adjusted to 5.8, which was the native pH of the soybean dust extract. Subjects were challenged with 0.08 ml/kg of each substance, resulting in a range of endotoxin doses of 30 to 60 micrograms, similar to that which a worker might inhale over the course of one workshift. The lowest mean percentage baseline FEV1 (+/- SD) after inhalation challenge was 99.2 +/- 2.1 for HBSS, and it was significantly lower for endotoxin (90.1 +/- 8.5, p = 0.03), corn dust extract (93.1 +/- 4.3, p = 0.02), and soybean dust extract (96.2 +/- 3.7, p = 0.03). In addition, a peripheral blood leukocytosis developed after exposure to all three endotoxin-containing solutions (p < 0.05), yet a lower peripheral blood lymphocyte count was found only after inhalation of corn dust extract (p = 0.02). Interestingly, this was associated with a higher nasal lavage lymphocyte count after inhalation of corn dust extract (p = 0.03). Neither the decrease in peripheral blood lymphocytes nor the increase in nasal lymphocytes were found after inhalation of soybean dust extract or endotoxin. Our results indicate that extracts of grain dusts have physiologic effects similar to endotoxin. However, in spite of the same endotoxin levels, the effects of corn dust extract appear to have different biologic activity than either soybean dust extract or endotoxin.

Administration, Inhalation↗
PubMed1976

Dust exposure in Finnish foundries.

Dust measurements were made in 51 iron, 9 steel, and 8 nonferrous foundries, at which 4,316 foundrymen were working. The sampling lasted at least two entire shifts or work days continuously during various operations in each foundry. The dust samples were collected at fixed sites or in the breathing zones of the workers. The mass concentration was determined by weighing and the respirable dust fraction was separated by liquid sedimentation. The free silica content was determined by X-ray diffraction. In the study a total of 3,188 samples were collected in the foundries and 6,505 determinations were made in the laboratory. The results indicated a definite difference in the dust exposure during various operations. The highest dust exposures were found during furnace, cupola, and pouring ladle repair. During cleaning work, sand mixing, and shake-out operations excessive silica dust concentrations were also measured. The lowest dust concentrations were measured during melting and pouring operations. Moderate dust concentrations were measured during coremaking and molding operations. The results obtained during the same operations of iron and steel foundries were similar. The distribution of the workers into various exposure categories, the content of respirable dust and quartz, the correlation between respirable dust and total dust, and the correlation between respirable silica and total dust concentrations are discussed. Observations concerning dust suppression and control methods are briefly considered.

Air Pollutants↗
PubMedDate not supplied

[The preparation and characterization of fine dusts carried out in the Clinica del Lavoro di Milano in support of experimental studies].

This paper aims to illustrate the conditions selected at the Clinica del Lavoro of the University of Milan to prepare and analyze a large number of fine dust samples produced over a period of about 50 years, that were initially used for studies within the Clinic performed in its own facilities, and since 1956 were sent to other Italian and overseas laboratories (Luxembourg, UK, Germany, Norway, Sweden, South Korea, USA). The total quantity of material distributed (with maximum size 7-10 microns) was about 2 kg and consisted of the following mineral and artificial compounds: quartz, HF-treated quartz, tridymite, HF-treated tridymite, cristobalite, chromite, anthracite, quartz sand for foundry moulds, sand from the Lybian desert, vitreous silica, pumice, cement, as well small quantities of metallic oxides, organic resins, chrysotile, crocidolite, fibres (vitreous, cotton and polyamidic). About half of the entire quantity of dusts produced consisted of partially HF-treated tridymite. Initially, research on the etiology of silicosis used quartz dust samples, simply sieved or ventilated (consisting of classes finer than 0.04 mm, containing a 15-20% respirable fraction). From 1956 to 1960 the dusts were produced by manual grinding in an agate mortar, below about 10 microns, starting from quartz from Quincinetto (near Ivrea, Province of Turin), containing about 99.5% quartz: particle size and composition were checked using an optical-petrographic technique, with identification of the free and total silica content. Subsequently, the dusts used for biological research were obtained by grinding coarse material with a cast iron pestle and planetary mills, agate and corundum jars. The grinding products were sized by means of centrifugal classification, using the selector developed by N. Zurlo, ensuring control of dust size both optically and by means of wet levigators and hydraulic classifiers (in cooperation with the Institute of Mines of Turin Polytechnic School). After 1990 pestles and rotating drum mills with autogenic grinding load were used for grinding: the size of the treated samples was reduced to 0.05 mm and an extremely fine fraction was extracted, smaller than 7-10 microns, which was used for pneumoconioses research. The characterization of the dust produced was in any case achieved by means of preliminary examination under the optical microscope (polarized light, sometimes supplemented with phase contrast), followed by quantitative analysis using chemical/petrographic, chemical diffraction or, more commonly, petrographic/diffraction techniques. Microscopic examination, if necessary supplemented with photo-micrography, was also used for particle size control, for numerical counting and subsequent reference to weight proportion. For all operational procedures the essential data on instruments and methods are reported. During studies on production, separation of fine dusts and their characterization, partly performed with support from the European Community (EEC/European Coal and Steel Commission), the following topics in particular were addressed: connections between particle size and free silica content in the measurable dust size fraction of the grinding products and in airborne dusts; characteristics of the dusts and risk indices in Italian iron and pyrite mines; possibility of abatement of the ultrafine classes of airborne dusts in pneumatically filled stopes by the addition of salts; comparison of the latest dust selectors used within the European Community; influence of the grinding methods on the results of fibrous and soft mineral measurement using X-ray diffraction analysis.

Academies and Institutes↗
PubMed2003

[Dust absorption effect of urban conifers in northeast China].

Dust pollution is much heavier in winter than in other seasons in the cities of Northeast China, because the urban heating system consumes mainly coal as energy resources. Deciduous trees can hardly absorb dust because of their defoliation, and hence, urban conifer trees become more important in dust absorption in winter. This paper studied the dust absorption ability of 7 conifers under the same and different dust pollution status in Shenyang city, Northeast China. The results showed that the dust absorption ability of conifers was decreased in the order of Abies holophilla > Picea mongolica > P. koraiensis > Taxus cupidata > Pinus bungeana > P. armandi > P. tabulaeformis. Different conifers had different surface structures. Pinus bungeana, P. armandi and P. tabulaeformis had smooth surfaces, their cells and stomata arranged in order, and hence, their dust absorption ability was poor. P. koraiensis, Abies holophilla and Taxus cupidata had coarse surfaces, and their cells and stomata arranged out of order. There were even many tubercular things on the surface of P. koraiensis, and hence, their dust absorption ability was stronger. The dust absorption ability of conifers was related the shape of their leaf sections. The upper leaf surface of Pinus bungeana and P. tabulaeformis was arc, not opted to absorb the dust. The leaf section of P. armandi was prism, and its upper surface was narrow, and hence, its dust absorption ability was also poor. The leaves of Picea mongolica and P. koraiensis had four edges, their upper surfaces were broader and flatter than the former three species, and hence, they had stronger dust absorption ability. The leaf section's shape of Abies holophilla and Taxus cupidata was also broad and flat, which made the dust absorption ability of the two latter's was stronger than other three Pinus species and two Picea species.

Absorption↗
PubMedDate not supplied

Dust-mites: effect on lipid peroxidation.

BACKGROUND: Dust-mites are present in our homes, feed on dead exfoliated skin and other organic material. It is also known that oxidative stress may lead to cellular damage that can be confirmed by markers of cellular disruption. Oxidative stress in various infective processes has been documented. We investigated whether house dust-mites cause oxidative stress in patients. METHODS: Products of lipid peroxidation in erythrocytes and lymphocytes were assessed by measuring malondialdehyde concentration. RESULTS: Our results showed that patients who had a positive skin test for dust-mite antigens and had dust-mites present in their houses (dust-mite positive) had increased erythrocyte malondialdehyde levels (62.39 [18.56] nmol/g-Hb) compared with those who were skin test positive, dust-mite negative (45.45 [10.82]) or skin test negative, dust-mite negative (42.20 [5.68]). They also had significantly higher levels of lymphocyte malondialdehyde (4.22 [0.55] nmol/g-protein) compared with those who were skin test positive, dust-mite negative (3.46 [0.29]) or skin test negative, dust-mite negative (1.25 [0.31]; p <0.05). However, there was no statistically significant difference between the malondialdehyde levels of dust-mite negative/skin test positive and dust-mite negative/skin test negative patients. CONCLUSION: Increased malondialdehyde activity in lymphocytes and erythrocytes in the dust-mite positive/skin test positive group shows the presence of the oxidative stress in patients with dust-mite infestation.

Adolescent↗
PubMed2005

House dust mites, our intimate associates.

House dust mites have lived in human contact from time immemorial. Human dander or dead skin constitutes the major organic component of the house dust ecosystem. Because the mites feed on dander, dust mites and human association will continue to co-exist as part of our environment. Efficient house-keeping practice is the best form of control to reduce infestation. However, special precautions are important when individuals are susceptible or sensitive to dust mites. House dust mites are responsible for causing asthma, rhinitis and contact dermatitis. The respiratory allergies are caused by the inhalation of dead or live mites, their faecal matter or other byproducts. Immune factors are of paramount importance in the development of dust related or mite induced respiratory diseases. House dust mites were found in some 1,000 samples of dust taken from approximately 330 dwellings in Peninsular Malaysia and Singapore. Mattresses, carpets, corners of a bedroom, and floor beneath the bed are favourable dust mite habitats. The incriminating species based on studies here and elsewhere, as well as many other species of dust mites of unknown etiological importance are widely distributed in Malaysian homes. Density of dust mites in Malaysia and Singapore is greater than in temperate countries. Prevention and control measures with reference to subjects sensitive to dust mite allergies, including chemical control described in studies conducted in Europe and America are discussed. However, a cost free and most practical way to remove mites, their faecal matter and other products is to resort to sunning the bedding and carpets to kill the living mites, and then beaten and brushed to remove the dust and other components.

Allergens↗
PubMed2002

House dust mite allergen levels in German day-care centers.

We investigated the levels of the major house dust mite allergens, Der p 1 and Der f 1, in dust collected from various locations in 41 day-care centers from two German cities (Düsseldorf and Bonn). One hundred and thirty-seven (96%) of 143 samples yielded detectable amounts of house dust mite allergen (range, < 15-85,000 ng/g; interquartile range, 210-1,480 ng group I allergen [sum of Der p 1 and Der f 1]/g dust), and 24 (17%) of the samples (8/34 mattresses; 11/46 cushions/soft toys; 5/43 carpeted floors, 0/20 smooth floors) exceeded the proposed "threshold" level of 2,000 ng/g dust in 18 (44%) of 41 day-care centers. Der p 1 and Der f 1 could be detected in nearly an equal number of samples. The highest concentrations of house dust mite allergens were found in dust from mattresses (geometric mean, 1,103 ng/g dust) and cushions/soft toys (geometric mean, 1,004 ng/g dust). The allergen load per unit area from carpeted floors exceeded that from smooth floors by more than two orders of magnitude. In comparison with dust samples from private homes within the same geographical area, the mite allergen levels in mattress dust (RR, 0.34; CI95, 0.18-0.64) and floor dust (RR, 0.21; CI95, 0.09-0.49) from day-care centers were significantly lower (p < 0.001). We conclude that day-care centers should be included as potential places of additional exposure to house dust mite allergens if avoidance measures are taken.

Allergens↗
PubMed1998

Determinants of personal dust exposure during field crop operations in California agriculture.

The aim of this study was to identify determinants, if any, of personal dust exposure levels during agricultural field crop operations in California. Personal dust concentrations were measured with four-stage cascade impactors and respirable dust cyclones. Altogether, 57 cascade impactor measurements and 63 cyclone measurements were used for analyses. High personal dust concentrations were measured during most operations, in particular during ground preparation operations such as land planing and discing. For the larger dust particles, which is dust collected on all stages of the cascade impactor and dust with a 50% cutoff < 9.8 microns, the most important determinants of personal dust exposure were the presence of an enclosed cabin, relative humidity, type of operation, and tractor speed. The presence of an enclosed cabin on the tractor, higher relative humidity, and lower tractor speed were all associated with a decrease in personal dust levels. For smaller dust particles, which is dust with a 50% cutoff < 3.5-4 microns, the presence of an enclosed cabin, relative humidity, and soil temperature appear to be related to dust levels. The results of this study could be used to reduce the high levels of personal dust exposure currently experienced by those who work in field crop farming in California.

Agriculture↗
PubMed2004

Influence of 8-bromo-cyclicAMP on interleukin -6 and -8 mRNA levels in A549 human lung epithelial cells exposed to organic dust: a time-kinetic study.

Exposure in a swine confinement building of previously unexposed subjects leads to an intense inflammatory reaction with increased number of inflammatory cells and mediators in the upper and lower respiratory tract. In vitro the organic dust induces cytokine release from respiratory epithelial cells. Whether the dust-induced release of IL-6 and IL-8 protein from A549 lung epithelial cells is a result of sustained mRNA expression during the 24 h exposure generally applied is unknown. Furthermore, it is not known if the previously demonstrated effects on basal and dust-induced IL-6 and IL-8 protein production by 8-bromo-cyclicAMP are time-dependent, since only cumulative effects are observed by measurement of cytokine release. In the present study reverse transcription- (RT-) PCR was applied to investigate expression of IL-6 and IL-8 mRNA in A549 cells exposed to organic dust in a time-kinetic manner. The dust increased IL-6 and IL-8 mRNA expression at all times tested (1 h-48 h). The IL-6 mRNA expression peaked at 1-1.5 h and was reduced with time, whereas the dust-induced IL-8 mRNA expression remained elevated. At 1-1.5 h, 8-bromo-cAMP stimulated basal and dust-induced IL-6 mRNA expression and attenuated dust-induced IL-8 mRNA expression by activation of protein kinase A- (PKA), as assessed with the PKA inhibitor H-89. On prolonged exposure (>3 h), the dust-induced IL-6 mRNA was PKA-dependently decreased, whereas at 17 h and longer the IL-8 mRNA expression induced by a dust-suspension with 8-bromo-cAMP was similar to, or enhanced, relative to the dust-induced IL-8 mRNA. Thus, 8-bromo-cAMP exerted opposite action on dust-induced IL-6 and IL-8 mRNA expression with time.

8-Bromo Cyclic Adenosine Monophosphate↗