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PubMed1989

The study of house dust mites in Taiwan.

By using a radioallergosorbent test (RAST) and intradermal skin testing, our previous studies strongly suggested that house dust mites are the most important allergen in Taiwan, especially in asthmatic children. This study was conducted to determine the distribution of house dust mites in houses of mite-sensitive asthmatic children and normals, the species of mites in various house dust samples, the seasonal prevalence, and the relation between the content of mite allergen and the mite density in dusts. Serial samples were collected every month between February 1986 and January 1987 from 61 houses of mite-allergic patients and nine normals. About 1 m2 surface area each of (A) family couch, (B) TV room floor carpet, (C) mattress, and (D) bed room floor carpet was vacuumed for one minute. The flotation method was used to collect mites in dusts and mites were counted under an inverted phase contrast microscope. Identification of house dust mite species was also performed. The RAST inhibition method was used for assay of mite allergen in dust extracts. The results showed the following six points. (1) Dermatophagoides pteronyssinus (DP) was the dominant species found in house dust in the Taipei area (78.8%). (2) The mean number of mites was greater in August through November and lowest in July. (3) The content of mite allergen did not correlate with the number of mites in dust sample. (4) The average number of mites in patients' houses was not different from that in normals' houses.(ABSTRACT TRUNCATED AT 250 WORDS)

Allergens↗
PubMed1988

[Histochemical studies of rat lungs after the short-term influence of soil dust].

There was examined the biological activity of soil dusts using histochemical methods. Intratracheal administration of dusts used in this study is a common method for testing activity of industrial dusts. The used soil dusts were characterized by high content of free silicon dioxide, 3 times higher than its content in dusts from power stations released in the process of burning coal and approximately to the amount in graphite dust. Both coal dusts and graphite dusts absorbed by the lungs cause silicoanthracosis. The investigations have been shown that soil dusts caused stimulation of the mitochondrial metabolism giving an increase of the activity of succinic dehydrogenase, lactic dehydrogenase, and ATPase induced by Mg++ ions. This was additionally confirmed by an increase of NADP activity which is an enzyme binding a chain or reactions regulating the hydrocarbonic metabolism. There was also observed an increased activity of the hydrolytic enzyme acid phosphatase. High activity occurred in the epithelium of bronchi and bronchioli and focally in pulmonary parenchyma.

Acid Phosphatase↗
PubMed1983

[SUVA (Swiss Accident Insurance Fund) and silicosis. Silicosis in Switzerland. Development of technological dust control].

In Switzerland the technical measures against quartz dust started in 1948 when wet drilling was compulsoryly introduced, initially in underground mining. The miners using the first wet drilling machines had serious problems with water, and only with the introduction of carriage drilling machines in 1963 did the method fully break through. Dust caused by blasting operations and by loading of the resultant material was limited by ventilation and sprinkling of water. In 1966 the first full-face cutting machines were used, and it was necessary to install a dust chamber behind the drill from which dust could be taken to a dust arrester. The problem of dust limitation when using boom cutters at sectional areas of more than 20 sq. meters without a pilot tunnel has not been resolved. Since 1970, dust in quarries and stone-cutter workshops has been successfully combated by the use of exhaust pumps in combination with filters. The use of quartz sand to clean metal pieces (sandblast) was forbidden in 1960. Today, materials of the same value, but quartz-free, are available. In foundries, dust production can be limited by continuous automation and installation of exhaust pumps in moulding units. For more than 30 years now the technical equipment has been available for successful prevention of quartz dust emissions. However, at some plants it is still difficult to persuade the personnel to use the protective equipment.

Dust↗
PubMed1994

Respiratory health status in swine producers relates to endotoxin exposure in the presence of low dust levels.

We conducted an assessment of respiratory health status including questionnaire and spirographic measurements in 54 male swine producers age 36.3 +/- 11.1 years (mean +/- SD) who worked an average of 10.7 +/- 6.3 years in the industry and spent 4.7 +/- 2.1 hours per day in the swine barns, and we also measured atmospheric contaminants including carbon dioxide, ammonia, total dust, respirable dust, and airborne endotoxin. Mean atmospheric dust contaminant levels were as follows: carbon dioxide, 2632 +/- 807 ppm; ammonia, 11.3 +/- 4.2 ppm; total dust, 2.93 +/- 0.92 mg/m3; respirable dust, 0.13 +/- 0.05 mg/m3; and endotoxin, 11,332 +/- 13,492 endotoxin units/m3. Of these, endotoxin related to forced vital capacity (P < .05) and endotoxin x hours per day was related to forced vital capacity (P < .05) and to forced expiratory volume in 1 second (P = .06). Respiratory symptoms and lung function studies did not relate to categories of low, medium, and high exposure to respirable dust. However, categories of endotoxin (available on 46 workers) related to respiratory symptoms (cough, P = .02; chronic bronchitis, P = .06; and to forced vital capacity, P < .01). These data suggest that respiratory health status relates to endotoxin levels but not to dust level exposures in the presence of low dust levels and indicates that control measures should include endotoxin as well as dust control.

Adult↗
PubMed1996

Recommendations for reducing the effect of grain dust on the lungs. Canadian Thoracic Society Standards Committee.

OBJECTIVE: To assess the appropriateness of the current Canadian standards for exposure to grain dust in the workplace. OPTIONS: The current permissible exposure limit of 10 mg of total grain dust per cubic metre of air (expressed as mg/m3) as an 8-hour time-weighted average exposure, or a lower permissible exposure limit. OUTCOMES: Acute symptoms of grain-dust exposure, such as cough, phlegm production, wheezing and dyspnea, similar chronic symptoms, and spirometric deficits revealing obstructive or restrictive disease. EVIDENCE: Articles published from 1924 to December 1993 were identified from Index Medicus and the bibliographies of pertinent articles. Subsequent articles published from 1994 (when the recommendations were approved by the Canadian Thoracic Society Standards Committee) to June 1996 were retrieved through a search of MEDLINE, and modification of the recommendations was not found to be necessary. Studies of interest were those that linked measurements of total grain dust levels to the development of acute and chronic respiratory symptoms and changes in lung function in exposed workers. Papers on the effects of grain dust on workers in feed mills were not included because other nutrients such as animal products may have been added to the grain. Unpublished reports (e.g., to Labour Canada) were included as sources of information. VALUES: A high value was placed on minimizing the biological harm that grain dust has on the lungs of grain workers. BENEFITS, HARMS AND COSTS: A permissible exposure limit of 5 mg/m3 would control the short-term effects of exposure to grain dust on workers. Evidence is insufficient to determine what level is needed to prevent long-term effects. The economic implications of implementing a lower permissible exposure limit have not been evaluated. RECOMMENDATIONS: The current Canadian standards for grain-dust exposure should be reviewed by Labour Canada and the grain industry. A permissible exposure level of 5 mg/m3 is recommended to control short-term effects. Further measurements that link the levels of exposure to respiratory health effects in workers across Canada should be collected to establish an exposure-response relation and possible regional differences in the effects of grain dust. VALIDATION: There has been no external review of these recommendations. However, the American Conference of Governmental Industrial Hygienists has recommended an 8-hour average exposure limit of 4 mg/m3 for wheat, oats and barley.

Air Pollutants, Occupational↗
PubMed1997

[PCDD/F-content in house dust].

The levels of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) were determined in house dust samples collected from 22 residential houses located in different areas of Germany. Nine houses were located in an urban and industrial area, one house in a rural and 10 houses in a contaminated residential area near to a former metal reclamation plant. Two house dust samples were collected from two old farm houses, in which large amounts of pentachlorophenol (PCP) containing wood preservatives had been used several years ago. All dust samples were collected from the dust bags of vacuum cleaners and passed through a sieve (mesh: 2.0 mm). Particles < 2.0 mm were used for analysis. The average level of PCDD/F in "normal" house dust was 101 ng I-TEq/kg (range: 7.83-332 ng I-TEq/kg). The predominant congeners and chlorohomologues were OctaCDD followed by HeptaCDD, HeptaCDF and OctaCDF. The average level of PCDD/F in house dust samples collected from a contaminated residential area was 265 ng I-TEq/kg (range: 29.9-1050 ng I-TEq/kg). When compared with "normal" residential houses significantly increased levels of lower chlorinated PCDD/F were noted in the house dust samples from this area. The house dust samples collected from a PCP-treated old farm house were found to contain 1.39 and 11.8 micrograms I-TEq/kg. The chlorohomologues patterns were typical for PCP contaminated with PCDD/F. The present study shows that the levels of PCDD/F in house dust may be used as indicators of indoor contamination by PCDD/F and as reference values for further investigations.

Air Pollutants↗
PubMed1998

The allergenic acarofauna of house dust from dwellings, hospitals, libraries and institutes in Upper Silesia (Poland).

A survey of dust samples from dwellings, hospitals and some public utilities (libraries, institutes) in several Upper Silesian towns was undertaken to determine the prevalence, number and species of mites. Total seasonal dynamics of dust mite species of the family Pyroglyphidae in dust from beds, floors/carpets and upholstery furniture in dwellings was analysed. Over a 4-years period, 402 dust samples were studied: 238 samples from dwellings, 122 samples from hospitals, 14 from libraries and 28 from institutes. Mites were present in 51.3%, 50.0%, 21.3% and 17.9% of dust samples from dwellings, libraries, hospitals and institutes, respectively. Generally, they were found in 160 samples (39.8%) out of 402 examined. The majority of mites (96.0%) were found in samples from the dwellings, especially in dust from upholstery furniture, couches, sofas and beds. More than 30 mite species were found of which the most abundant and common were pyroglyphids, especially Dermatophagoides pteronyssinus and D. farinae. The pyroglyphid mites constituted 89.2%, 78.9% and 57.5% of a total count of mites collected from dwellings, libraries and hospitals, respectively, and were not found in institutes. D. pteronyssinus was the dominant, especially in libraries and hospitals, however, in dwellings D. farinae was more abundant per 1 gram of dust as the former species. Another pyroglyphid mite, Euroglyphus maynei, occurred in very small numbers. The highest mite densities per gram of dust were noted in dwellings and libraries. A mean number of mites per 1 gram of dust from dwellings was 73.7 +/- 182.9 (range 1.0 - 1560.0), whereas mean values of indoor relative humidity and temperature were 64.5% RH and 22.7 degrees C, respectively. The low mean indoor relative humidity of ambient air, resulted in the relatively low mite frequency (only about 51.3% of samples were positive for mites) and density detected in the dwellings.

Air Pollutants, Occupational↗
PubMed1995

N-acetyl-beta-D-glucosaminidase activity within BAL from macaques exposed to generic coal dusts.

N-acetyl-beta(beta)-D-glucosaminidase is a lysosomal enzyme secreted by alveolar macrophages in response to phagocytosis of particulate material. Alveolar macrophages participate in the degradation and fibrosis of pulmonary tissue that results in pneumoconiosis. Known quantities of four characterized respirable dusts were bronchoscopically placed into the right caudal lung lobe of macaque monkeys. Bronchoalveolar lavage (BAL) samples were collected from dust-exposed right lung and unexposed left lung of the same individuals at 2-week intervals for 12 weeks after dust instillation. The samples were tested for N-acetyl-beta-D-glucosaminidase activity to determine if the enzyme levels could serve as an indicator of pulmonary injury induced by generic coal dusts when compared to known fibrogenic and nuisance dusts. Installation of generic quartz, anthracite, or TiO2 dusts produced significant elevations of enzyme activity and increased numbers of macrophages in the dust-exposed lobes. Elevations in enzymatic activity and macrophage numbers were greatest in response to generic quartz dust. These results suggest that quantitative levels of N-acetyl-beta-D-glucosaminidase activity may be a useful indicator of acute and chronic lung injury following exposure to fibrogenic and nonfibrogenic dusts.

Acetylglucosaminidase↗
PubMed1995

Physical effects of dust on leaf physiology of cucumber and kidney bean plants.

The physical effects of dust accumulating on leaf surfaces, on leaf physiology, such as photosynthesis, transpiration, stomatal conductance and leaf temperature of cucumber and kidney bean plants were investigated by the use of chemically inert dust. It was found that dust decreased stomatal conductance in the light, and increased it in the dark by plugging the stomata, when the stomata were open during dusting. When dust of smaller particles was applied, the effect was greater. However, the effect was negligible when the stomata were closed during dusting. The dust decreased the photosynthetic rate by shading the leaf surface. The dust of smaller particles had a greater shading effect. Moreover, it was found that the additional absorption of incident radiation by the dust increased the leaf temperature, and consequently changed the photosynthetic rate in accordance with its response curve to leaf temperature. The increase in leaf temperature also increased the transpiration rate.

Journal Article↗
PubMed2004

Family history, dust mite exposure in early childhood, and risk for pediatric atopy and asthma.

BACKGROUND: Dust mite allergen exposure is considered a major determinant of sensitization to these allergens during childhood and a risk factor for pediatric asthma. OBJECTIVE: By using a birth cohort in a setting with a substantial burden of dust mite allergen, we evaluated exposure and risk for outcomes related to allergy and asthma. METHODS: We collected dust from the bedrooms of 428 children born from 1987 to 1989 and measured Der f 1 and Der p 1 (microg/g dust, combined). Follow-up at 6 to 7 years of age included clinical examination, skin prick testing, specific serum IgE measurement, and methacholine challenge. RESULTS: No overall association was evident for any outcome except bronchial hyperresponsiveness (adjusted odds ratio [OR], 0.62; 95% CI, 0.38-1.00; P <.050; and OR, 0.53; CI, 0.27-1.04; P <.065 for dust mite allergen levels > or =2 microg/g and >10 microg/g, respectively). With a parental history of allergy and asthma, there was an association between a positive dust mite skin test (OR, 2.09; CI, 0.93-4.73; P <.076) and dust mite allergen level >10 microg/g. The inverse was true for children without a parental history. Dust mite exposure of >10 microg/g was associated with a decreased risk of current atopic asthma among children with a parental history (OR, 0.39; CI, 0.05-3.13; P <.376), but with increased risk if without a parental history (OR, 1.52; CI, 0.22-10.6; P <.673). CONCLUSION: Parental history is an important independent variable in the relationship between early dust mite exposure and atopic outcomes. Increased exposure during infancy is associated with a higher risk for sensitization in the presence of a positive parental history, but is protective among children of parents without a history of atopic disease.

Antigens, Dermatophagoides↗
PubMed2000

Granulometry and the content of toxic and potentially toxic elements in vacuum-cleaner collected, indoor dusts of the city of Warsaw.

Twenty-seven sites, together with 23 household dust sample sites, representing the home environment, and four public room dust sample sites, representing working environment (mainly offices) have been described in this paper. The latter were examined to obtain an approximate reference to the home environment data. All the samples were collected between May and July 1997 by a vacuum-cleaner method, in the city of Warsaw, Poland. The granulometry of the dusts was determined by their separation into seven fractions in the range 8-500 microm. The concentrations of Cr, Ni, Cu, Zn, Pb, Br and Fe in the samples were investigated in fractions 8-32, 32-63 and 63-125 microm by the EDXRF technique. The results showed higher concentrations of these elements in finer fractions (8-32 microm). The Pb content in the household dusts was found to be unexpectedly low, ranging from 120 microg g(-1) for the 63-125 microm fraction, up to 210 microg g(-1) for the 8-32 microm fraction. Car exhausts could not be determined clearly as the main source of Pb in the indoor household dusts due to the lack of a Pb-Br intercorrelation. In these dusts, only Cr and Zn showed a remarkably high content of 90-100 and 1020-1070 (microg g(-1)), respectively. In the household dusts, strong intercorrelations were present in the three analysed fractions for the metal pairs: Pb-Zn, Pb-Cu, Fe-Cr, and Cu-Cr (weaker). The working environment rooms showed a higher degree of dustiness by 300%, as compared to the dwellings. The dusts collected in the working environment rooms showed slightly higher concentrations of Ni and by 50-100% higher concentrations of: Cu, Zn, Pb, Br than the analysed household dusts.

Air Pollution, Indoor↗
PubMed2002

Concentration of atmospheric particulates during a dust storm period in central Taiwan, Taichung.

In this study we monitored concentrations of particles in central Taiwan using PS-1 (GPS1 PUF Sampler) and Model 310 Universal Air Sampler (UAS) from 02/23/2001 to 03/12/2001 at two sampling sites. During this period, an Asian dust storm moved across central Taiwan from 3/3 to 3/6. The total ambient air particle concentrations during the dust storm period were than compared with previous data from this region. In general, the average total suspended particulate (TSP) concentration order was during dust storm period > after dust storm period > non-dust storm period at both HKITT (traffic) and THUC (rural) sampling sites. The ratio of PM2.5/PM10 was 60% before and after the dust storm period. However, this ratio was decreased to less than 50% during the dust storm. This demonstrates that the coarse particulate concentrations (PM2.5-10) increased during the dust storm period. In contrast the increase of ambient air particles concentrations after the Taiwan Chi-Chi Earthquake were mainly due to fine particles (PM2.5). And, the increased of ambient air particles concentrations after dust storm period were mainly coarse particle (PM2.5-10) concentrations in central Taiwan.

Journal Article↗
PubMed1999

Sensitization to local dust-mite fauna in Singapore.

BACKGROUND: Recent studies showed the presence of a unique dust-mite fauna in the indoor environment of Singapore. Immediate hypersensitivity to these dust mites, along with other known indoor allergens, may play a role in the pathogenesis of allergic respiratory diseases. This study evaluated the sensitization rates of the local atopic population to these allergens. METHODS: The skin prick test was performed on a total of 391 individuals (289 patients with asthma and/or allergic rhinitis and 102 healthy controls) using extracts of six species of local dust mites (Austroglycyphagus malaysiensis, Blomia tropicalis, Dermatophagoides pteronyssinus, D. farinae, Sturnophagoides brasiliensis, and Tyrophagus putrescentiae) and 10 other common indoor allergens. Total serum IgE and specific IgE to these dust mites were also quantified with the fluorescence allergosorbent test (FAST). RESULTS: The sensitization rates among patients with asthma and/or allergic rhinitis to dust mites and other inhalant allergens tested (via skin prick tests) were as follow: B. tropicalis (96.2%), D. pteronyssinus (93.4%), D. farinae (92.3%), A. malaysiensis (78.2%), S. brasiliensis (71.6%), T. putrescentiae (71.3%), canary feathers (69.9%), Periplaneta americana (cockroach) (59.5%), Blattella germanica (cockroach) (56.4%), mosquito (Aedes sp.) (46.4%), dog epithelia (mixed breed) (34.3%), kapok seed (31.8%), cat hair (29.1%), Aspergillus fumigatus (20.8%), Penicillium notatum (18.0%), and Candida (Monilia) albicans (9.3%). All patients were observed to react to at least three of the six dust-mite extracts, with 254/289 (87.9%) reacting to at least five or to all six. Skin prick responses to the dust mites were found to correlate with the corresponding specific IgE levels quantified by FAST (P<0.001). In addition, specific IgE levels to D. pteronyssinus and D. farinae were highly correlated (Spearman's rank coefficient = 0.76, P<0.001), as were those to B. tropicalis and A. malaysiensis (r = 0.60, P<0.001). CONCLUSIONS: Asthma and/or allergic rhinitis patients were highly sensitized to the local dust-mite fauna. Thus, these dust mites should be considered important allergenic sources of this region.

Adolescent↗
PubMed1999

Abundance of house dust mites in relation to climate in contrasting agricultural settlements in Israel.

The correlation between climatic conditions and mite numbers in houses from rural areas was studied in 13 agricultural communities (kibbutzim and moshavim) in nine geo-climatic subregions of Israel. Mites were present in 97% of the dust samples. The average number of mites per gram of dust in the different localities ranged between 84 and 2053. The maximum number of mites (7440/g dust) was found in a carpet from a house in Geva Carmel in the northern coastal region. The most prevalent species of mites were Dermatophagoides pteronyssinus and Dermatophagoides farinae, which were found in 85.6% and 71.3% of the samples, respectively. The house dust mites D. pteronyssinus, D. farinae and Euroglyphus maynei constituted 94.8% of the mites. Most of the mites were isolated from the carpets and sofas (37.0% and 33.7%, respectively), and a smaller number from beds (29.3%). The smallest number of mites (< or = 250/g dust) were found at a minimum relative humidity (RH) of 30% and lower, with a maximum temperature of 32 degrees C and higher, i.e. in the Jordan valley and Negev mountains. A greater number of mites (250-500/g dust) were found at a minimum ambient RH of 35-40% and a maximum temperature of 32 degrees C and higher, i.e. the Hula valley. A large number of mites (500-1000/g dust) were found at a minimum RH of 35-40% with a maximum temperature of 30 degrees C and lower, i.e. in the Judean and Samarian range, as well as in upper Galilee. The largest number of mites (1000-2000/g dust) was found at a minimum RH of 45% and higher, with a maximum temperature ranging between 30 and 32 degrees C. These conditions occur in the coastal strip, the coastal plain and in the Judean and Samarian foothills. A monthly examination of two houses in Zova, a kibbutz in the Judean hills next to Jerusalem, and two houses from Palmachim, a kibbutz in the coastal region, revealed that the highest prevalence of mites was found in the months April-November and May-November, respectively. In Zova, the highest number of mites were found during the months of June and July while the highest concentrations of D. pteronyssinus-antigen (Der p I) were measured during the month of September. A positive correlation between mite numbers and the quantity of Der p I in house dust was found.

Agriculture↗
PubMed2001

Desert dust suppressing precipitation: a possible desertification feedback loop.

The effect of desert dust on cloud properties and precipitation has so far been studied solely by using theoretical models, which predict that rainfall would be enhanced. Here we present observations showing the contrary; the effect of dust on cloud properties is to inhibit precipitation. Using satellite and aircraft observations we show that clouds forming within desert dust contain small droplets and produce little precipitation by drop coalescence. Measurement of the size distribution and the chemical analysis of individual Saharan dust particles collected in such a dust storm suggest a possible mechanism for the diminished rainfall. The detrimental impact of dust on rainfall is smaller than that caused by smoke from biomass burning or anthropogenic air pollution, but the large abundance of desert dust in the atmosphere renders it important. The reduction of precipitation from clouds affected by desert dust can cause drier soil, which in turn raises more dust, thus providing a possible feedback loop to further decrease precipitation. Furthermore, anthropogenic changes of land use exposing the topsoil can initiate such a desertification feedback process.

Journal Article↗
PubMed2000

Simulating the Effects of Intergalactic Gray Dust.

Using a high-resolution cosmological hydrodynamic simulation, we present a method to constrain extinction due to intergalactic gray dust based on the observed magnitudes of distant Type Ia supernovae. We apply several simple prescriptions to relate the intergalactic dust density to the gas density in the simulation, thereby obtaining dust extinctions that may be directly compared with the observed distribution of supernova magnitudes. Our analysis is sensitive to the spatial distribution of gray dust but is not dependent on its intrinsic properties, such as its opacity or grain size. We present an application of our technique to the supernova data of Perlmutter et al., who find that their high-redshift sample is approximately 0.2 mag fainter than the expectation for a nonaccelerating, low-density universe. We find that for gray dust to be responsible, it must be distributed quite smoothly (e.g., tracing intergalactic gas). More realistic dust distributions, such as dust tracing the metal density, are inconsistent with observations at the 1.5-2 sigma level. Upcoming observations and improved modeling of the dust distribution should lead to stronger constraints on intergalactic gray dust extinction.

Journal Article↗
PubMed1999

Theory of dust voids in plasmas.

Dusty plasmas in a gas discharge often feature a stable void, i.e., a dust-free region inside the dust cloud. This occurs under conditions relevant to both plasma processing discharges and plasma crystal experiments. The void results from a balance of the electrostatic and ion drag forces on a dust particle. The ion drag force is driven by a flow of ions outward from an ionization source and toward the surrounding dust cloud, which has a negative space charge. In equilibrium the force balance for dust particles requires that the boundary with the dust cloud be sharp, provided that the particles are cold and monodispersive. Numerical solutions of the one-dimensional nonlinear fluid equations are carried out including dust charging and dust-neutral collisions, but not ion-neutral collisions. The regions of parameter space that allow stable void equilibria are identified. There is a minimum ionization rate that can sustain a void. Spatial profiles of plasma parameters in the void are reported. In the absence of ion-neutral collisions, the ion flow enters the dust cloud's edge at Mach number M=1. Phase diagrams for expanding or contracting voids reveal a stationary point corresponding to a single stable equilibrium void size, provided the ionization rate is constant. Large voids contract and small voids expand until they attain this stationary void size. On the other hand, if the ionization rate is not constant, the void size can oscillate. Results are compared to recent laboratory and microgravity experiments.

Journal Article↗
PubMed2004

[Characteristics of the occurrence of silicosis in the workers exposed to uranium dust].

OBJECTIVE: To understand the laws and characteristics of silicosis incidence of the workers exposed to the uranium dust from 1956 to 2002. METHODS: The length of employment, age of occurrence of silicosis, and its duration and death age were compared between the uranium miners and uranium geological prospecting teams, and also between the miners exposed to uranium dust and those exposed to mixed uranium dust by single factor analysis method. RESULTS: With time going on, the length of employment, age of occurrence of disease and its duration and death age were prolonged respectively in the workers exposed to uranium dust. The length of employment and age of occurrence of disease in uranium geological prospecting teams [(10.15 +/- 5.95) and (40.60 +/- 9.86) years respectively] were shorter than those in uranium miners [(14.23 +/- 8.12) and (41.38 +/- 10.98) years], but the duration (P(50)) and death age were longer [(14.29 years vs 12.52 years), (53.69 +/- 10.04) years vs (51.45 +/- 10.85) years respectively]. The length of employment and age of occurrence of disease in those exposed to uranium dust only [(11.78 +/- 8.06) and (38.04 +/- 9.89) years] were shorter than those exposed to mixed uranium dust [(12.74 +/- 6.29) years, (41.40 +/- 10.67) years], but the duration (P(50)) and death age were longer than the mixed uranium dust ones [(14.59 years vs 13.20 years), (53.93 +/- 10.60) years vs (51.82 +/- 10.20) years]. CONCLUSION: The difference in the occurrence of silicosis in the workers exposed to uranium dust may be attributed to the physical and chemical character of the uranium dust and the different working circumstance.

Age of Onset↗