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Exposure of farmers to dust on private farms of various production profiles.

In the light of studies of dustiness in agriculture conducted in Poland and abroad, which deal exclusively with dust risk while performing selected occupations, the results presented in this article are a subsequent attempt to recognize annual exposure to dust at workplaces in agriculture. This recognition concerns the workplace of private farmers--typical of Polish agriculture--on family farms of various profiles of production. The study covered 10 selected farms: four animal breeding farms, four specialised cultivation farms, and two traditional mixed-production farms comprising animal breeding and plant cultivation. The results of the study showed an unequal distribution of the working time load and exposure to dust among the farmers examined during the whole year. The monthly working time limit ranged from 53.6-208.8% of the legal working time. The values of the mean weighted monthly concentrations of total dust ranged within 1.2-33.9 mg x m(-3), and those of respirable dust - 0.3-4.0 mg x m(-3), the highest values being observed in August and September. Mean weighted monthly concentrations describing an average level of farmers' exposure to total dust (7.7-21.9 mg x m(-3)), together with the confidence intervals, remain above the occupational exposure limit (4.0 mg x m(-3)), which is equivalent to hazardous conditions. In the case of respirable dust the results obtained show allowable conditions. Despite this, the dusty working conditions of the farmers in the study should be regarded as hazardous, due to the high level of exposure to total dust observed and potentially high contents of pathogenic components. The highest level of exposure was noted on farms engaged in potato production and marketing, followed by traditional farms carrying out mixed production, while the lowest level of exposure was observed on farms engaged in dairy cattle breeding.

Agricultural Workers' Diseases↗

Evaluation of airborne dust and endotoxin in corn storage and processing facilities in Colorado.

The main objectives of this research were to determine what aerosols were present by taking total dust (TD) samples and thoracic particulate mass samples (TPM) on farms and in grain elevators. Cascade impactors were used to characterize size distributions of dust and endotoxins at each site. Total dust concentrations on farms had a geometric mean 3.4 mg/m3 and 3.3 mg/m3 in elevators. The geometric mean (GM) concentrations for the TPM were 2.4 mg/m3 on farms and 1.0 mg/m3 in elevators. Endotoxin concentrations as geometric means were alarming at 3175 EU/m3 total dust and 983 EU/m3 by TPM on farms. In elevators, the GM concentrations for endotoxins were 2534 EU/m3 total dust, and 526 EU/m3 by TPM. The mass median aerodynamic diameter (MMAD) for endotoxins on farms was 8.0 microm and 6.5 microm in elevators. The paired t-test was applied to the log ratios of endotoxin concentrations (EU/m3) and dust concentrations (mg/m3), for paired samples of the TD and TPM. A higher content of endotoxins was associated with TPM for farms but not elevators. It was concluded that although the TPM fraction (dust) may represent a small part of the total mass, the aerosol size is optimum for deposition in the lung's tubular airways, and might cause airway inflammation due to the endotoxins. The TPM fraction of corn dust represents the best measure of exposure with regard to the potential development of long-term airways inflammation, and the potential of chronic obstructive pulmonary disease among chronically exposed workers. All endotoxin concentrations were well above recommended exposure levels of several researchers familiar with endotoxin health effects.

Aerosols↗

[Acarofauna of house dust in Barcelona and surrounding cities].

The study of the house-dust acarofauna has aroused great interest since Voorhorst and colls. (41), in 1964, showed the continual presence of Dermatophagoides pteronyssinus in this habitat; and considered by these authors to be mainly responsible for the allergenic capacity of housedust. Studies carried out by other authors around the world confirm the universal character of this acarus and its prevailing presence in house-dust biocenosis. Dermatophagoides pteronyssinus is usually accompanied with other species of the same Pyroglyphidae family (see table II and III), and by species belonging to other acarian families and groups (table I). In this work 182 house-dust samples have been analyzed; these samples were collected in Barcelona and its surrounding. All have been found to be positive to acari. Samples of 5 g of house-dust were used for the study. The number of acari present in each sample showed a great variation both in relation to the total of acari present and to the number of isolated Pyroglyphidae (table VII and VIII). Dermatophagoides pteronyssinus appeared to be the prevailing species, found in 175 of the 182 samples examined and representing 39.70% of the total population of the acari collected. Other Pyroglyphidae isolated were D. farinae (95 samples), Euroglyphus maynei (75 samples), D. microceras (19 samples), D. passericola (1 sample) and Malayoglyphus carmelitus (1 sample) (table VI). The frequency and density in which other species of acari appeared in house-dust samples studied are shown in table VII. If we compare our results with those obtained by others (1, 7, 11, 21, 23, 26, 28, 29, 38) we see a great difference according to the frequency of acarian infestation in house-dust. We think that the causes of this variation are the diverse methods and techniques employed in the isolation and enumeration of acari. The low infestation percentages given by some authors could be due to the following: a) a study of insufficient amounts of house-dust samples; b) the lack of a method used for processing the samples; c) the interaction of both factors. The discovery of three single D. passericola specimens found in one sample lets us assume that the pressence of this acarus in house-dust has been sporadic. We think it could originate from birds' feathers or nests. Despite the very high number of Tarsonemus sp. collected (37.17% of the acari total) the representative of this species is actually very low, since almost all of them were found in two different samples taken from the same house.

Acari↗

[Dust removal effect of urban tree species in Harbin].

Dust removal by plants was proposed as an important basis of designing urban green space system for future urbanization. Dust removal measurement and leaf surface electron-microscopic scanning were taken for 28 tree species in Harbin city. The results showed that there were obviously different effects of dust removal among different tree species. Picea koraiensis and Juniperus rigida were the ideal conifers for dust removal, and their dust removal abilities were 5.7 g.m-2 and 4.4 g.m-2 after 4 weeks, respectively. Populus alba x berolinensis, Lonicera maackii, and Prunus maackii were the ideal deciduous tree species, and their dust removal abilities were respectively 1.9 g.m-2, 2.0 g.m-2, and 2.45 g.m-2 after 2 weeks. Observation under electronic microscope showed that tree species, having deep channels or dense hair on leaf surface had greater effects of dust removal, while tree species, which had strumose projections on leaf surface, had weaker effects. Different modes of dust removal by plants were also discussed.

Carbon Dioxide↗

[Influence of tobacco dust on the respiratory system and selected immunological parameters].

UNLABELLED: Tobacco dust contains various immunologically active as well as toxic substances. However the relationship between allergic reactivity or lung function with chronic exposure to tobacco dust remains unclear. Accordingly the aim of the present study was to investigate the relationship between occupational chronic exposition to tobacco dust, respiratory function and some allergic reaction parameters. METHODS: 40 tobacco factory workers (47.5% women and 52.5% men) aged 25-59 years (mean 36.5) chronically (5-31 years, mean 12.6) exposed to tobacco dust were included into the study. Control group consisted of 30 subjects (46.7% women, 53.3% men) aged 25-60 years (mean 36.6) not exposed to tobacco leaves' dust. Detailed epidemiological data was collected. Additionally total IgE, specific (tobacco) IgE, eosinophil blood counts, skin tests (mixed grass and weed pollens, house dust, feather, tobacco extracts), basophil degranulation and neutrophil destruction tests with tobacco extracts as well as spirometry were studied in these groups. We found that FEV1/VC was significantly lower in tobacco industry workers chronically exposed to tobacco dust than in the control group (91.5 +/- 11.6% vs. 101.7 +/- 10.7% n; p = 0.0004). These subjects were also characterized by higher occurrence of mild bronchial obturation (FEV1/VC < 88% and FEV1 > 70%) which was present in 30% tobacco factory workers and in 6.7% of control group (p = 0.035). Levels of total IgE and tobacco-specific IgE, eosinophil counts, skin test reactivity, basophil degranulation and neutrophil destruction tests were not different between groups. CONCLUSIONS: Occupational chronic exposition to the dust of tobacco leaves is associated with significant increase in the occurrence of mild obturative ventilatory disturbances. Simultaneously no increased frequency of allergization to tobacco or other allergens was observed in tobacco industry workers.

Adult↗

[Biological testing of the fibrogenic effect of dust from the "Sosnowiec" mine on the lung tissue].

In order to determine biological aggressiveness of settled dusts (mechanical, crumbled) and dusts collected using the gravimetric method, experimental studies were carried out, including: 1) evaluation of the physicochemical parameters (size of dust particles, content of silica, metals and other chemical compounds), 2) evaluation of the haemolytic activity, 3) experimental evaluation of fibrogenic potentials by means of: a) intraperitoneal test--to identity morphological type of reactive changes in the peritoneum and b) intratracheal test--to determine the level of hydroxyproline (collagen) in lungs and the morphological type of reactive changes. Albino rats were used for the experiment. The animals were divided into ten groups which received a single intratracheal injection of 50 mg of mining dust in 0.9% NaCl suspension. Comparative evaluation of biological aggressiveness of mining dusts was conducted basing on the findings of collagen levels in lungs. After the end of the experimental period (3 and 6 months, respectively) histopathological a examination of the lungs and mediastinal lymph nodes was made and the collagen levels in the pulmonary tissue (following Stegemann) were determined. As evidenced by the results of the pathomorphological examination and a statistical analysis: 1) after intratracheal injection the mining dusts induced changes within the respiratory system e.g. inflammatory process and emphysema. The exposure also brought about double increase of collagen level as compared to the control group, 2) histopathological study of the lungs and lymph nodes did not reveal progressive development of fibrogenic changes, 3) cytotoxic test showed differences in the haemolytic activity of settled dust and dusts collected by the gravimetric method.

Air Pollutants, Occupational↗

[Assessment of risk for tin mine dust in Guangxi].

OBJECTIVE: To explore the minimum observed adverse effect level(LOAEL) and intensity of pathogenesis of tin mine dust. METHODS: A cohort study design with retrospective assessment of exposure was used. Selected 4,471 male tin miners who were exposed to tin at least one year during 1960 to 1974 and were compared with 4,797 pottery dust exposed workers in the same way designed. Statistical analysis system SAS, PROC LIFETEST were used to perform the non-parameter calculation by Life Table method. RESULTS: Tin mine cohort subjects were followed up to December 31, 1994. The percentage of miners who developed silicosis was 21.7% (971/4,471). 81% of the patients had been exposed to dust before 1958. The cumulative total dust exposure(CTD) was significantly correlated with silicosis risk. The risk of silicosis was 0.012 when CTD was less than 50 mg/m-3.year-1. The risk of silicosis was increased to 0.971 when CTD was beyond 400 mg.m-3.year-1. However, the risk of silicosis was only 0.369 for dust exposed workers in pottery factories when CTD was beyond 400 mg.m-3.year-1. CONCLUSION: There was significant relationship between cumulative dust exposure and the incidence of silicosis in tin exposed workers. And silicosis induced by tin mine dust is more serious than the pottery dust.

Cohort Studies↗

Allergy to house dust mites and asthma.

House dust mites have been shown to be important sources of indoor allergens associated with asthma and other allergic conditions. Asthma is a chronic respiratory disease that affects millions of people worldwide, and numerous scientific studies have shown that the prevalence of asthma is increasing. The most common dust mite species around the world include Dermatophagoides pteronyssinus (Dp), Dermatophagoides farinae (Df), Euroglyphus maynei (Em) and Blomia tropicalis (Bt). Over the past three decades, many important allergens from these species have been identified and characterized at the molecular level. The biological function of several house dust mite allergens has been elucidated, with many of them showing enzymatic activity. However, Bt allergens remain the least studied, even though this mite is very common in tropical and subtropical regions of the world, including Puerto Rico. Therefore, it is very important to include Bt in diagnostic and therapeutic strategies for house dust mite induced allergy and asthma, particularly in areas where Bt exposure and sensitization is high. Recombinant DNA technology, as well as other molecular biology and immunological techniques, have played a fundamental role in advances towards a better understanding of the biology of house dust mites and their role in allergic diseases. This kind of study also contributes to the understanding of the complex immunologic mechanisms involved in allergic reactions. The development of effective diagnostic and therapeutic approaches depends on the continuity of research of house dust mite allergens. The objectives of this review are to describe the most important aspects of house dust mite allergy and to acquaint the scientific community with the latest findings pertaining to house dust mite allergens, particularly those derived from Bt.

Allergens↗

Airway toxicity of house dust and its fungal composition.

House dust is an important source of different toxic metabolites as well as allergens, including those of fungal origin, in the indoor environment. A bio-assay employing 1-day-old chick tracheas was used to characterize airway effects of 2-butanone and dimethylsulphoxide (Me2SO) extracts of 23 dust samples collected from water damaged (13) and control (10) Danish schools. Direct microscopical analysis of samples, followed by cultivation on dichloran 18 % glycerol agar at 25 degrees C for 10 days to establish their mycoflora, was performed. The in vitro ciliostatic potential of the chloroform-extractable endo- and exometabolites of 41 representative fungal isolates was determined. Nine dust extracts in 2-butanone (2 from damp rooms) or 10 (6) in Me(2)SO showed some ciliostatic activity in the 3-days' experiment. Fungal composition of dust from buildings with leakage was almost identical with that from undamaged houses, as well as the fungal colony counts from the damp schools and the control samples. Aspergillus spp. were prevalent in the samples - 31 or 40 % of all fungi, followed by Penicillium spp. and Cladosporium cladosporioides. Alternaria spp., Chaetomium spp., Mucor spp., Mycelia sterilia, Paecilomyces variotii, Rhizopus sp., Ulocladium sp. and yeasts were each isolated in less than 8 % of the fungal content. No Aspergillus flavus isolate (8 in total) was aflatoxigenic,em>in vitro. Alternaria spp., Aspergillus spp., Botrytis cinerea, Penicillium spp., C. cladosporioides, Chaetomium spp. and Ulocladium sp.; in total, 88 % of all fungi tested, produced ciliostatically active metabolites. These toxigenic strains were also present in 4 dust samples from controls and 5 dust samples from water damaged buildings. Extracts of these dust samples were also toxic in bioassay. There were bio-detectable concentrations (10-20 microg of extracts/ml of the organ culture medium) of toxic compounds in house dust. Contribution of fungal metabolites to its toxic effect should be studied further.

Air Microbiology↗

Health hazards of cement dust.

Even in the 21st century, millions of people are working daily in a dusty environment. They are exposed to different types of health hazards such as fume, gases and dust, which are risk factors in developing occupational disease. Cement industry is involved in the development of structure of this advanced and modern world but generates dust during its production. Cement dust causes lung function impairment, chronic obstructive lung disease, restrictive lung disease, pneumoconiosis and carcinoma of the lungs, stomach and colon. Other studies have shown that cement dust may enter into the systemic circulation and thereby reach the essentially all the organs of body and affects the different tissues including heart, liver, spleen, bone, muscles and hairs and ultimately affecting their micro-structure and physiological performance. Most of the studies have been previously attempted to evaluate the effects of cement dust exposure on the basis of spirometry or radiology, or both. However, collective effort describing the general effects of cement dust on different organ and systems in humans or animals, or both has not been published. Therefore, the aim of this review is to gather the potential toxic effects of cement dust and to minimize the health risks in cement mill workers by providing them with information regarding the hazards of cement dust.

Air Pollutants, Occupational↗

[The new German general threshold limit value for dust--pro and contra the adoption in Austria].

Since it has been realised that inhalation of inert dust is one of the important confounding variables for the development of chronic bronchitis, the threshold values for occupational exposure to these dusts needs to be further decreased. The German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area (MAK-Commission) has set a new threshold (MAK-Value) for inert dusts (4 mg/m3 for inhalable dust, 1.5 mg/m3 for respirable dust) in 1997. This value is much lower than the threshold values currently used world-wide. The aim of the present article is to assess the scientific plausibility of the methodology (databases and statistics) used to set these new German MAK-Values, regarding their adoption in Austria. Although we believe that it is substantial to lower the MAK-Value for inert dust in order to prevent the development of chronic bronchitis as a consequence of occupational exposure to inert dusts, the applied methodology used by the German MAK-Commission in 1997 to set the new MAK-Values does not justify the reduction of the threshold limit value. A carefully designed study to establish an appropriate scientific basis for setting a new threshold value for inert dusts in the workplace should be carried out. Meanwhile, at least the currently internationally applied threshold values should be adopted in Austria.

Air Pollutants, Occupational↗

[Biological attestation of the fibrogenic effect of dust from selected coal mines on the lung tissue].

The studies aimed at determining the changes in respiratory system of animals after intratracheal administration of settled dusts sampled from seams 116 and 188 in Janina colliery and seams 314 and 317 in Victoria colliery. For comparison, dusts sampled gravimetrically from a/m seams in Janina and Victoria collieries were intratracheally administered to animals. Crystalline silica concentrations determined by Polezajew method in dusts from Janina and Victoria collieries were 2.4% to 8.1% and 1.6% to 2.8%, respectively. Biological aggressiveness of mine dusts was examined using intraperitoneal, pulmonary and hemolytic tests. Hydroxyproline concentration was determined by Stegemann method using the modification of Hurych and Chvapil (2). The results of biochemical analysis were subjected to a statistical analysis by t-Student's test. Specimens from lungs for histopathological examination were stained with hematoxylin and eosin, while collagen fibres were stained by Van Gieson method. A single intratracheal administration of dust collected gravimetrically from 116 seam and settled dust from seam 118 in Janina colciery caused, after six months, a hypro-increase by more than three times comparing with the control group. No correlations were found between higher hypro-levels in lungs and histological changes. It seems probable that higher hypro-levels in lungs can be caused mainly by SiO2 whose concentration in dusts was 8%. Similar concentrations of aluminium and ferrous compounds may suggest that their influence on the biological activity of silica is mutually eliminated. After a six-month intratracheal administration of dusts from Victoria colliery in Wałbrzych, a hypro-decrease was observed compared to a three-month period of administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Air Pollutants, Occupational↗

[Public perceptions of the risk of Asian dust storms in Seoul and its metropolitan area].

OBJECTIVES: In spite of the recent increased concern for Asian dust storms, there are few studies concerning how dangerous the general public recognizes these dust storms to be. This study examined the public's perceptions of the risk of the Asian dust storms and also the source of the information concerning the risk. METHODS: A telephone interview survey using a standardized questionnaire was done for the adults living in Seoul and its metropolitan area from May 15th, 2003 to May 16th, 2003. The contents of the questionnaire were the sociodemographic characteristics, the perceptions of risk to the Asian dust storms, and the coping strategy of the study participants. RESULTS: The study participants get their information on Asian dust storms mainly from TV newscasts and they have a good knowledge of them. They regard it as one of the most dangerous health risks, along with dioxin. They think that it is associated with allergic rhinitis, conjunctivitis and bronchial asthma, etc. Of the 500 study participants, 201(40.2%) persons suffered bodily discomforts during the Asian dust storm period. CONCLUSIONS: Although there are uncertainties about the health risks of Asian dust storms, the public thinks these dust storms are very dangerous to health in many ways. This negative perception will not disappear easily. To fill the gap of the public's perceptions of the risk and the objective evidence of its health effects, more studies about its health effects and the methods to reduce exposure are required.

Adult↗

[Determination of ergosterol amount in house dust of different indoor environment in Shanghai City by HPLC].

OBJECTIVE: A high performance liquid chromatographic (HPLC) method was developed for the determination of the amount of ergosterol in house dust, and was examined the feasibility on determination of ergosterol in house dust. According to the established method, different house dusts derived from different functional indoor air was sampled and determined. We expected to regard ergosterol as an indicator of fungal biomass. METHODS: We picked up dust samples from nine typical functional indoor area to represent different room temperature, ventilation, air conditioning, human activities, pet-feeding, et al, during Dec 2004 to Jan 2005. The house dust was sampled with a dust collector, and filtrated with a filter. Fine house dusts were extracted by ultrasonic blending, filtration, refluxing, saponification and evaporation. High liquid chromatography was carried out and combined with gas chromatography (GC)-mass spectrometry (MS) to analyze the molecular structure. RESULTS: A linearity association was observed in the range of 0.02 to 0.8 g/L ergosterol. The detection concentration was 0.0005 g/L. The intra-and inter-day relative standard deviations (RSD) were in the range of 10.2% - 11.7% and 4.54% - 7.34%, respectively. The absolute recoveries ranged between 77.1% and 80.1%. Survey results showed the amount of ergosterol differed greatly from the different sampling spots. The amount of ergosterol had a positive correlation with room temperature and people denseness, while had a negative correlation with natural ventilation, briefly. The highest amount was 66.08 microg/g (house dust). CONCLUSION: The method is sensitive, accurate and feasible. It can examine different ergosterol content in environmental matrix. Followed by GC-MS, the reliability of the results can be further checked. The sampling data show there are different degrees of fungal contamination in typical indoor air of Shanghai City.

Air Pollutants↗

[Occupational exposure to asbestos-containing dust at the plants manufacturing and using asbestos products during the years 1986-1989].

During 1986-1989, dust levels at workplaces in 19 plants manufacturing or using asbestos products in Poland were measured. Total dust concentrations were determined by the gravimetric method and respirable asbestos fibre concentrations were determined by the phase contrast optical microscope method (PCOM). Air was sampled at the breathing zones of the workers by using Casella personal air samplers. Average respirable asbestos fibre concentrations at the workplaces were from 0.06 fibre/cm3 (control desk operator) to 2.25 fibre/cm3 (spinning machine operator), and the average total dust concentrations were from 0.7 mg/m3 (technicians) to 2.3 mg/m3 (preparatory department workers). Compared with the 1980-1985 period, total dust concentrations were 1.5 times, and respirable asbestos fibre concentrations 2.9 times lower. Considering the obtained data and the analysis of the occupational diseases in workers exposed to asbestos dust during 1983-1988, the national expert group for industrial dusts has suggested that the MAC values for chrysotile dusts be lowered to 1.0 mg/m3 (total dust) and 0.5 fibre/cm3 (respirable fibre).

Air Pollutants, Occupational↗

Studies on the effect of quartz, bentonite and coal dust mixtures on macrophages in vitro.

The effect of quartz, bentonite and coal dusts as well as the effect of the artificial mixture of these dusts on TTC reduction and extra-and intra-cellular lactate dehydrogenase activity in peritoneal rat macrophages was determined in vitro. The cell-membrane-damaging effect of quartz caused a significant extracellular release of lactate dehydrogenase. Bentonite caused no extracellular enzyme release, which leads us to believe that the biological effect of this dust is shown by decrease in intra-cellular lactate dehydrogenase activity. TTC reduction was inhibited equally by quartz and qentonite. In mixtures of quartz (60%)-bentonite (40%) dust the specific effect of quartz was inhibited by bentonite in vitro and also in vivo. We obtained the same results with coal-quartz-bentonite dust mixtures in vitro. Our experiments show that comparison of the biological effects of artificial dust mixtures and airborne dust samples is justified, and prove that performing various examinations simultaneously give fuller particulars on the probable biological effect of mineral dusts.

Animals↗

[Biological testing of fibrogenic effect of dust from the "Gliwice" mine on the lung tissue].

Animal study was carried out to determine biological aggressiveness of mining dust by means of pulmonary tests. Dust samples, 50 mg settled dust, a mixture from 3 different mine layers (sample A) and 50 mg dust collected by the gravimetric method from different mine layers (sample B) were administered in two respective test groups by a single intratracheal injection. Silica content, determined according to Polezhayev, was found to range from 4.6% (sample A) to 12.7% (sample B). In months 3 and 6 of the experiment lung content of hydroxyproline was determined following Stegemann. Biochemical tests for hydroxyproline content revealed highest increase in the lungs of Group 2 animals 6 months after the onset of the experiment (10.312 mg). Very similar result was obtained in Group 1, with injected settled dust mixture: hydroxyproline level amounted to 10.214 mg. Both sample A and sample B induced elevated level of lung hydroxyproline although silica content in dust sample differed considerably. The study revealed that the biological aggressiveness of settled dust was not proportionate to the content of pure silica. It is thought that increased fibrogenic potentials of the settled dust may have resulted from defected crystalline structure of silica due to the grinding of the mineral in a hand-mill.

Air Pollutants, Occupational↗

Bronchial challenge to house dust can induce immediate bronchoconstriction in allergic asthmatic patients.

The goal of the study was to evaluate whether natural exposure to house dust could elicit immediate bronchoconstriction. Two groups of asthmatic patients were studied: 12 asthmatics allergic to house dust mites and seven nonallergic asthmatics. The baseline FEV1 was similar in the two groups. Each subject was challenged through a nasal mask connected to nebulizer filled with house dust. Patients were randomly assigned to inhale dust with high or low Group I allergenic level. All allergic patients had an FEV1 drop larger than 20% of the baseline value. This drop was maximal at the 30th minute after challenge. FEV1 remained unchanged in nonallergic asthmatics. Allergic patients challenged with high Group I allergenic house dust (8.4 micrograms/g) had a mean FEV1 drop larger (P less than .01) than those challenged with the low Group I allergenic house dust (0.66 micrograms/g). Late asthmatic reactions were found in only two patients who were challenged with the high Group I allergenic house dust. These two patients had immediate FEV1 drops greater than 50% of the baseline value. Occurrence of symptoms during the test and the drop in FEV1 were correlated (r = .3; P less than .05). Natural exposure to house dust can induce immediate bronchial in allergic asthmatics in a dose-dependent manner.

Adult↗