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PubMed1988

Dust emissions in cattle feedlots.

Dust emissions were measured at three Texas cattle feedlots on 15 occasions in 1987 to determine concentrations of total suspended particulate matter (TSP) and dust with 10 microns or less aerodynamic particle size (PM-10). Net feedlot dust concentrations (downwind minus upwind) ranged from 15.7 to 1,700.1 micrograms per m3 and averaged 412.4 +/- 271.2 micrograms per m3, which is about 37 per cent less than was determined in feedlot dust research in California approximately 17 years earlier. Upwind concentrations averaged 22 per cent of the downwind concentrations. Feedlot dust concentrations were generally highest in early evening and lowest in early morning. Using the Wedding and Andersen-321A PM-10 samplers, the PM-10 dust concentrations were 19 and 40 per cent, respectively, of mean TSP concentrations in direct comparisons. There was good correlation between PM-10 and TSP concentrations. Although dust concentrations decreased with increasing moisture, the correlation coefficients were relatively low. Odor intensity appeared to increase with decreasing net dust concentrations, perhaps due to moisture influences. Mean particle sizes of feedlot dust were 8.5 to 12.2 microns on a particle volume basis and 2.5 to 3.4 microns on a population basis. Respirable dust (below 2 microns) represented only 2.0 to 4.4 per cent of total dust on a particle volume basis. Under conditions of these experiments, the feedlots often exceeded both state and federal (U.S. Environmental Protection Agency) standards for TSP concentrations and for PM-10 concentrations measured using the Andersen-321A sampler. However, feedlots were below the new U.S. Environmental Protection Agency standards when the Wedding PM-10 sampler was used for measuring dust emissions.

Animals↗

PubMedDate not supplied

Trace element patterns and seasonal variability of dust precipitation in a low polluted city--the example of Karlsruhe/Germany.

Urban areas of different land uses can be distinguished by their specific patterns of atmospheric dust and trace element precipitation. Dusts emitted from industrial areas with fossil fuel processing, for instance, are enriched in V, Ni and Co. Cluster analysis groups sampling sites based on their specific element patterns. The resulting groups correspond to the surrounding land use: Urban sampling sites were identified showing similar patterns of dust and trace element precipitation as a reference site; dusts of other urban sites were influenced by diffuse pollution (caused by non-point and dispersed pollution sources), or by specific industrial emissions. Cluster analysis was also used to characterize the chemical dust composition. Three clusters of typical element associations were distinguished. These clusters represent the dust matrix, diffuse urban pollution and pollution due to fossil fuel processing. Dust precipitation and chemical dust composition show seasonal variations. Dust precipitation and concentrations of trace elements in the precipitated dust are negatively correlated during the annual courses. The highest concentrations of trace elements occur during winter, whereas the highest precipitations of dust were found during summer. This finding stresses that both, precipitation and concentration have to be addressed for the environmental assessment of urban dusts.

Air Pollutants↗

PubMed2000

Methods to lower the dust exposure of bag machine operators and bag stackers.

This article reviews various dust control technologies developed over the years at the Pittsburgh Research Laboratory of the National Institute for Occupational Safety and Health (NIOSH) to provide various options and alternatives to lower bag machine operators' and bag stackers' dust exposures. Dust exposure records for the past 20 years show that bag machine operators and bag stackers normally have the highest respirable dust exposures of workers at mineral processing plants. A substantial amount of research has been performed over the years to minimize the dust exposure to these workers and the intent is to present all this information together in one article. Most of the research describes engineering controls that were adapted to existing facilities to reduce the dust generated during bag filling, bag conveying, and bag stacking. In some cases, a single technique succeeded in lowering respirable dust concentrations for all three processes, thus reducing the dust exposure to both the bag machine operator and the bag stacker. In other cases, a technique was developed to specifically reduce the dust exposure of one process or the other. This research also reviews various controls for secondary dust exposure, including general ventilation requirements to mill buildings, the effects of background dust sources, and personal work practices. This information is presented to help industrial hygienists, plant managers, engineers, and workers lower the dust exposure of bag machine operators and bag stackers.

Dust↗

PubMed2002

Determinants of dust exposure in tunnel construction work.

In tunnel construction work, dust is generated from rock drilling, rock bolting, grinding, scaling, and transport operations. Other important dust-generating activities are blasting rock and spraying wet concrete on tunnel walls for strength and finishing work. The aim of this study was to identify determinants of dust exposure in tunnel construction work and to propose control measures. Personal exposures to total dust, respirable dust, and alpha-quartz were measured among 209 construction workers who were divided into 8 job groups performing similar tasks: drill and blast workers, shaft drilling workers, tunnel boring machine workers, shotcreting operators, support workers, concrete workers, outdoor concrete workers, and electricians. Information on determinants was obtained from interviewing the workers, observation by the industrial hygienist responsible for the sampling, and the job site superintendent. Multivariate regression models were used to identify determinants associated with the dust exposures within the job groups. The geometric mean exposure to total dust, respirable dust, and alpha-quartz for all tunnel workers was 3.5 mg/m(3) (GSD = 2.6), 1.2 mg/m(3) (GSD = 2.4), and 0.035 mg/m(3) (GSD = 5.0), respectively. A total of 15 percent of the total dust measurements, 5 percent of the respirable dust, and 21 percent of the alpha-quartz exceeded the Norwegian OELs of 10 mg/m(3), 5 mg/m(3), and 0.1 mg/m(3), respectively. Job groups with highest geometric mean total dust exposure were shotcreting operators (6.8 mg/m(3)), tunnel boring machine workers (6.2 mg/m(3)), and shaft drilling workers (6.1 mg/m(3)). The lowest exposed groups to total dust were outdoor concrete workers (1.0 mg/m(3)), electricians (1.4 mg/m(3)), and support workers (1.9 mg/m(3)). Important determinants of exposure were job group, job site, certain tasks (e.g., drilling and scaling), the presence of a cab, and breakthrough of the tunnel. The use of ventilated, closed cabs appeared to be the single most important control measure for lowering exposures.

Adult↗

PubMed1999

A soiling system for evaluation of house dust, allergens, and lead retention on carpets and other surfaces.

Artificial soiling of carpeted or other floor surfaces has several important applications in human exposure assessment and textile research including evaluation of textile properties, sampling devices, and cleaning regimens. A method was developed and validated to deposit uniform and reproducible known quantities of house dust, allergens, and leaded dust on carpets. The soiling apparatus consisted of a 100 cm x 60 cm inclined steel track and a plastic cylinder, with a series of staggered holes, that contains a known volume of reference house dust. After deposition, the dust is embedded by dragging a steel rod over the carpet surface. Deposition tests were performed with bulk house dust, sodium chloride, and house dust with reference quantities of dust mite allergen and lead. The apparatus deposited equivalent (arithmetic mean) amounts of dust, sodium chloride, and dust mite allergen on the front and back halves of test carpets. The introduction of inert fumed silica to the reference sample aided in dispersal of dust over test surfaces. Little to no variation in mean deposition was found within or between 4 days of testing. Using a grid containing weighing boats under the apparatus, spatial deposition was found to vary across a 92 x 46 cm surface by 13 percent. The apparatus deposited reproducible mean quantities of bulk dust on test surfaces from 7 g/m2 to 28 g/m2 with a coefficient of variation ranging from 4-6 percent. The apparatus could be altered to deliver smaller or larger amounts of dust.

Allergens↗

PubMed1986

Wood dust and formaldehyde exposures in the cabinet-making industry.

Time-weighted average (TWA) personal total and respirable dust exposures were determined gravimetrically for 48 subjects in 4 cabinet-making plants. TWA personal formaldehyde exposures also were obtained, with the use of 3M 3750 passive monitors. Selective area sampling for formaldehyde was undertaken using two methods. The results obtained with the passive monitors were compared to the standard chromotropic acid impinger method. Considerable variation was noted in the dust exposures. Cabinet-makers exposed to softwoods were found to have a mean exposure of approximately one half of the current applicable ACGIH TWA-TLV, while hard-wood exposure was twice the applicable TWA-TLV. The highest dust exposures were recorded for those workers sanding, the mean total dust being 2.91 mg/m3 (S.E. 0.70) and respirable dust 0.63 mg/m3 (S.E. 0.20). Sanding operations also were found to produce a higher proportion of respirable dust (22%) than other woodworking operations (6%-14%). Workers in assembly areas also were found to have higher dust exposures, likely reflecting the fact that conventional dust collection devices for stationary woodworking equipment are not appropriate for hand held tools and hand sanding. The importance of making respirable dust measurements is discussed. The poor correlation between paired total and respirable dust concentrations indicates that both measurements should be made. Some potential limitations to respirable wood dust sampling using 10 mm nylon cyclones are noted, however. Area dust concentrations were found to be significantly lower than personal exposures, emphasizing the importance of personal sampling data. Formaldehyde vapor exposures were very low, with a mean of 0.06 ppm (S.E. 0.01).

Air Pollutants, Occupational↗

PubMed1992

Experimental examination of factors that affect dust generation by using Heubach and MRI testers.

Four factors that affect dust generation were investigated--type of test material, particle size distribution of the test material, moisture content of the test material, and apparatus used to generate dust. Dust generated from silicon carbide and aluminum oxide was measured by using MRI and Heubach dustiness testers modified to allow the measurement of dust particle size distribution with an Andersen impactor. The two materials investigated generated similar dusts. The size distribution of the test material slightly influenced the amount but strongly influenced the size distribution of the dust generated. Increased moisture content decreased the amount of dust generated; moisture content had little influence on dust size distribution. The two testers generated different amounts of dust; however, the dust particle size distributions generated were similar. These results help explain factors that affect dust generation and the relative importance of alternative methods for dust control.

Aluminum Oxide↗

PubMed2006

Estimation of respirable dust exposure among coal miners in South Africa.

The use of retrospective occupational hygiene data for epidemiologic studies is useful in determining exposure-outcome relationships, but the potential for exposure misclassification is high. Although dust sampling in the South African coal industry has been a legal requirement for several decades, these historical data are not readily adequate for estimating past exposures. This study describes the respirable coal mine dust levels in three South African coal mines over time. Each of the participating mining operations had well-documented dust sampling information that was used to describe historical trends in dust exposure. Investigator-collected personal dust samples were taken using standardized techniques from the face, backbye (underground jobs not at the coal face), and surface from 50 miners at each mine, repeated over three sampling cycles. Job histories and exposure information was obtained from a sample of 684 current miners and 188 ex-miners. Linear models were developed to estimate the exposure levels associated with work in each mine, exposure zone, and over time using a combination of operator-collected historical data and investigator-collected samples. The estimated levels were then combined with work history information to calculate cumulative exposure metrics for the miner cohort. The mean historical and investigator-collected respirable dust levels were within international norms and South African standards. Silica content of the dust samples was also below the 5% regulatory action level. Mean respirable dust concentrations at the face, based on investigator-collected samples, were 0.9 mg/m(3), 1.3 mg/m(3), and 1.9 mg/m(3) at Mines 1, 2, and 3, respectively. The operator-collected samples showed considerable variability across exposure zones, mines, and time, with the annual means at the face ranging from 0.4 mg/m(3) to 2.9 mg/m(3). Statistically significant findings were found between operator- and investigator-collected dust samples. Model-based arithmetic mean dust estimates at the face were 1.2 mg/m(3), 2.0 mg/m(3), and 0.9 mg/m(3) for Mines 1, 2, and 3, respectively. Using these levels, the mean cumulative exposure for the cohort was 56.8 mg-years/m(3). Current miners had a mean cumulative exposure of 66.5 mg-years/m(3), compared with ex-miners of 26.8 mg-years/m(3). Improvements in dust management or the use of different sampling equipment could account for the significant differences seen between operator- and investigator-collected data. Regression modeling for estimating mean dust levels over time using combined historical and investigator-collected data seems a reasonable method and useful in constructing models to describe cumulative exposures in a cohort of current and ex-miners.

Air Pollutants, Occupational↗

PubMed1979

Inhibition experiments with solid phase mite or epithelia in house dust hypersensitivity.

The present study was undertaken to verify that mites are not the only allergens in house dust extracts and that other allergens such as cat epithelia can also be responsible for house dust hypersensitivities detected both by house dust skin tests and house dust RAST studies. In order to determine whether mite or epithelia fixed on a solid phase could remove not only the IgE antibodies reactive with the homologous allergens, but also the IgE antibodies reactive with house dust allergens, the authors have absorbed 10 sera of house dust allergic patients with solid phase mite or epithelia. The absorption procedure removed a large part of the IgE antibodies reactive with specific immunosorbent (Dermatophagoides pteronyssinus or cat epithelia) and in the same way the IgE antibodies reactive with house dust immunosorbent. The percentage of RAST inhibition varied from 65% to 92% for Dermatophagoides pteronyssinus and from 65% to 94% for house dust in patients allergic to house dust and mite; the percentage of RAST inhibition varied from 67% to 92% for cat epithelia and from 73% to 90% for house dust in patients allergic to house dust and cat epithelia. This is in accordance with the hypothesis that house dust is not an allergen per se, but rather a complex mosaic of several allergens including mite, animal epithelia, etc.

Absorption↗

PubMed2005

The dustfall collector--a simple passive tool for long-term collection of airborne dust: a project under the Danish Mould in Buildings program (DAMIB).

UNLABELLED: A newly developed dustfall device that collects airborne dust by sedimentation has been evaluated in Danish schools. Dust collected over 140 days was compared with airborne dust sampled during single school days and settled floor dust sampled at the end of a school day. Measurements of culturable fungi in air samples corresponded well to those from the dustfall collector in mechanically but not naturally ventilated rooms. Levels of beta(1 --> 3)glucan and culturable fungi in dust from the dustfall collector and settled floor dust did not agree well. Up to 10 times more beta(1 --> 3)glucan per milligram dust was found in the dustfall collectors than in settled floor dust. Only in dust from the dustfall collector was the mass concentration of culturable fungi (cfu/mg) significantly correlated with the degree of dampness. The culturability of fungi in the 140-day dustfall samples tended to be lower than in other types of samples. Nonetheless, the results indicated that the dustfall collector can be used to estimate the median concentration of airborne culturable fungi, provided identical sampling periods are used for all samples. The collector is cost effective and simple to use. PRACTICAL IMPLICATIONS: Traditional ways of assessing exposure to microorganisms by sampling airborne dust or dust from floors have several disadvantages. In the present paper, a new sampler, the dustfall collector, which collects airborne dust by sedimentation over a period of months, is introduced. Tests of this collector indicate that it can be used to estimate the mean concentration of airborne culturable fungi but not beta(1 --> 3)glucan over a long period and that the method can differentiate between buildings with different levels of water damage.

Adolescent↗

PubMed1993

Occupational dust exposure and chronic obstructive pulmonary disease. A systematic overview of the evidence.

The object of this study was to assess the relationship between occupational dust exposure and chronic obstructive pulmonary disease (COPD). Studies were identified using MEDLINE (January 1966 to July 1991), SCISEARCH, manual review of reference lists, and personal contact with more than 30 international experts. Studies of COPD, lung function, emphysema, chronic bronchitis, or mortality in workers exposed to nonorganic dust were retrieved. Studies were included if dust exposure was measured quantitatively, and a quantitative relationship between dust exposure and one of the outcomes of interest was calculated while controlling at least for smoking and age. Methodological rigor was assessed, and data regarding the study populations, prognostic factors, and outcomes were extracted independently by two reviewers. Thirteen reports derived from four cohorts of workers met our inclusion criteria. Three of the cohorts were of coal miners and one was of gold miners. All of the studies found a statistically significant association between loss of lung function and cumulative respirable dust exposure. It was estimated that 80 (95% CI, 34 to 137) of 1,000 nonsmoking coal miners with a cumulative respirable dust exposure of 122.5 gh/m3 (considered equivalent to 35 years of work with a mean respirable dust level of 2 mg/m3) could be expected to develop a clinically important (> 20%) loss of FEV1 attributable to dust. Among 1,000 smoking miners the comparable estimate was 66 (95% CI, 49 to 84). The risk of a clinically important loss of lung function attributable to dust among nonsmoking gold miners was estimated to be three times as large as for coal miners at less than one fifth of the cumulative respirable dust exposure (21.3 gh/m3), the maximal exposure observed among the cohort of gold miners. We conclude that occupational dust is an important cause of COPD, and the risk appears to be greater for gold miners than for coal miners. One possible explanation of the greater risk among gold miners is the higher silica content in gold mine dust.

Bronchitis↗

PubMedDate not supplied

Enzyme activities and arylsulfatase protein content of dust and the soil source: biochemical fingerprints?

Little is known about the potential of enzyme activities, which are sensitive to soil properties and management, for the characterization of dust properties. Enzyme activities may be among the dust properties key to identifying the soil source of dust. We generated dust (27 and 7 microm) under controlled laboratory conditions from agricultural soils (0-5 cm) with history of continuous cotton (Gossypium hirsutum L.) or cotton rotated with peanut (Arachis hypogaea L.), sorghum [Sorghum bicolor (L.) Moench], rye (Secale cereale L.), or wheat (Triticum aestivum L.) under different water management (irrigated or dryland) and tillage (conservation or conventional) systems. The 27- and 7-microm dust samples showed activities of beta-glucosidase, alkaline phosphatase, and arylsulfatase, which are related to cellulose degradation and phosphorus and sulfur mineralization in soil, respectively. Dust samples generated from a loam and sandy clay loam showed higher enzyme activities compared with dust samples from a fine sandy loam. Enzyme activities of dust samples were significantly correlated to the activities of the soil source with r > 0.74 (P < 0.01). The arylsulfatase proteins contents of the soils (0.04-0.65 mg protein kg(-1) soil) were lower than values reported for soils from other regions, but still dust contained arylsulfatase protein. The three enzyme activities studied, as a group, separated the dust samples due to the crop rotation or tillage practice history of the soil source. The results indicated that the enzyme activities of dust will aid in providing better characterization of dust properties and expanding our understanding of soil and air quality impacts related to wind erosion.

Agriculture↗

PubMed1998

Isotopic ratio analysis in residential lead-based paint and associated surficial dust.

OBJECTIVES: This investigation assessed the contribution of lead in lead-based paint (7 samples) to lead-laden dust (8 samples) in a single suburban vacant residence using isotopic ratio analysis. METHODS: Interior/exterior lead-based paint surface concentration was measured by X-ray fluorescence while dust and scrapings were analyzed chemically for total lead content and by mass spectrometry for the associated isotopic ratios. RESULTS: Four out of 5 comparisons of paint (7 samples) and dust (8 samples) for a given location did not match isotopically. In the one location where the isotopic ratio of the paint and dust samples matched closely, some portions of the paint were not intact. One explanation for the isotopic ratio match is that the dust sample may have actually been contaminated with paint flecks. This explanation appears likely since the isotopic ratio for the lead in the dust and paint sample were not in the modern average range of US environmental lead, strongly indicating a local point source of the lead in this dust sample, namely the paint at this location. Lead dust samples whose isotopic ratio lies in the modern average range for US environmental lead cannot be correlated to the paint which is beneath them, since the isotopic ratio of lead in the dust may actually be a composite of many sources of lead over time, as suggested by an isotopic ratio in the modern average range. CONCLUSIONS: From the samples from this one house, the data dispute the contention that intact lead-based paint chalks and creates lead-contaminated dust on its surface. While leaded household dust may contribute to children's lead exposure, intact paint need not contribute to surficial lead-laden dust. Isotopic ratio measurements can be useful for point-source determination by virtue of sample match and by placement of the ratio on the spectrum of isotopic ratio values for lead. Point-source assessment based on isotopic ratio was either strengthened or weakened by placement outside or within the average range for US environmental lead, respectively.

Air Pollutants↗

PubMed1999

[Examination of dust generated from a workplace where steel wire coil are unwound].

Analyses of constituents, measurement of concentrations, research of size distributions and scanning electron microscopic examinations were carried out to determine the type and amount of dust generated in a working environment where steel wire coils are unwound. In about a 700 m2 work area unit, stationary samplings, including A-sampling (24 points) and B-sampling (1 point), which are defined by the law, were carried out. The dust concentration was measured by a digital dust indicator. A low volume air sampler was used to determine the conversion factor of the values obtained by the digital dust indicator. Because the result of the dust level by A-sampling and B-sampling were 0.64 mg/m3 and 0.82 mg/m3 respectively, they can both be classified as Control Class 1. A proportion of less than 7 microns of the airborne dust made up about 15 to 20% (volume %) of the total dust in the working environments. Metallic dust and white dust were identified in the accumulated dust. By measuring with a X-ray diffractometry, it was determined that the metal dust constituent was Zn and the white dust constituent was Zn4CO3(OH)6.H2O. By a scanning electron microscopic examination, the scope of the particles was proven to be non-fibrous.

Air Pollutants, Occupational↗

PubMed2001

Levels of fungi and mycotoxins in samples of grain and grain dust collected on farms in Eastern Poland.

Ten samples of stored wheat grain and 10 samples of settled grain dust released during machine threshing of wheat grain were collected on 10 farms located in Lublin province (eastern Poland). The samples were examined for the concentration of total microfungi, Fusarium species, fusariotoxins (moniliformin, deoxynivalenol, nivalenol), and ochratoxin. Microfungi able to grow on malt agar were present in 30% of grain samples (median for all examined samples = 0, range 0-227.5 x 10(3) cfu/g) and in all samples of grain dust (median = 977.5 x 10(3) cfu/g, range 115.0-16,700.0 x 10(3) cfu/g). Fusarium species (F. avenaceum) were found only in 10% of grain samples (median = 0, range 0-800.0 x 10(3) cfu/g), but in 90% of grain dust samples (median = 1,150 x 10(3) cfu/g, range 5.5-10,060.0 x 10(3) cfu/g). The species F. avenaceum, F. culmorum, F. graminearum, F. poae and F. sporotrichioides were isolated respectively from 50%, 10%, 20%, 40% and 20% of examined grain dust samples. The presence of the mycotoxins produced by Fusarium (moniliformin, deoxynivalenol, and nivalenol) was found altogether in 70% of wheat grain samples (median = 0.1275 microg/g, range 0-1.480 microg/g) and in 90% of grain dust samples (median = 0.350 microg/g, range 0-1.090 microg/g). Moniliformin (MON), deoxynivalenol (DON), and nivalenol (NIV) were each detected in 40% of grain samples, and respectively in 80%, 40%, and 40% of grain dust samples. Ochratoxin A (OTA) was detected in 60% of grain samples and in 60% of grain dust samples (median in both cases was 0.0005 microg/g). The concentrations of F. poae (p<0.05) and of total Fusarium species (p<0.01) in grain samples, and the concentrations of F. culmorum and F. graminearum (p<0.05) in grain dust samples were significantly correlated with the concentration of deoxynivalenol. The concentrations of F. poae (p<0.05) and of total Fusarium species (p<0.01) in grain dust samples were significantly correlated with the concentration of total fusariotoxins. Moreover, the concentration of total Fusarium species in grain dust samples was significantly correlated with the concentration of nivalenol (p<0.05). In conclusion, the majority of samples of wheat grain and grain threshing dust collected on farms in eastern Poland contained notable quantities of fusaria and/or fusariotoxins. This fact poses a potential risk of mycotoxicoses to agricultural workers exposed to grain dust when handling wheat during threshing, unloading, shuffling, and other farm occupations.

Agricultural Workers' Diseases↗

PubMed2001

[Evaluation of historical exposure to silica dust for the workers employed in geologic exploration industry].

OBJECTIVE: To evaluate their level of exposure to silica dust in the workers employed in geologic exploration industry using a quantitative method. METHODS: Monitoring data of exposure to silica dust since 1950s were collected for the workers in various jobs from the factories and mines of the bureaux of geological exploration in the nine provinces, with 30,000 pieces of figures in total. Job title and history of employment were determined for 1,627 employees. Levels of exposure to silica dust in various factories and mines were estimated based on the data mentioned-above, including amount of respirable dust, total dust in the lungs, and proportion of free silica dust to the total silica dust. RESULTS: Concentration of total silica dust was 14 mg/m3 in average in the factories and mines, with a range of 29 mg/m3 during the earlier years to 3 mg/m3 in recent years, and that of respirable silica dust was 3 mg/m3, in average, with (28.0 +/- 8.2)% of free silica dust. Different indices of exposure to silica dust were calculated for individuals, based on their history of employment and level of exposure. CONCLUSION: Assessment of exposure to silica dust during the past years, based on the monitoring data, could provide basis for evaluation of dose-response relationship.

Air Pollutants, Occupational↗

PubMed2002

[Appropriate dust control measures for jade carving operations].

OBJECTIVE: To provide the appropriate dust control measures for jade carving operations. METHODS: Dust concentrations in the workplace were measured according to GB/T 5748-85. Ventilation system of dust control were measured according to GB/T 16157-1996. Dust particle size distributions for different sources and particle size fraction collecting efficiencies of the dust collectors were measured with WY-1 in-stack 7 stage cascade impactors. RESULTS: On the basis of adopting wet process in the carving operations, local exhaust ventilation system for dust control was installed, which included: the special designed slot exhaust hoods with hood face velocity of 2.5 m/s and exhaust volume of 600 m3/h. The pipe sizes were determined according to the air volume passing through the pipe and the reasonable air velocities. Impinging scrubber or bag filter dust collector were selected to treat the dust laden air from the local exhaust ventilation system, which gave a total collecting efficiency of 97% for impinging scrubber and 98% for bag filter; The type of fan and its size were selected according to the total air volume of the ventilation system and maximum total pressure needed for the longest pipe line plus the pressure drop of the dust collector. CONCLUSIONS: Practical application showed that, after installation and use of the appropriate dust control measures, the dust concentrations in the workplaces could meet or nearly meet the national hygienic standard and the dust laden air at the local exhaust ventilation system could meet the national emission standard.

Dust↗

PubMed2006

[Pulmonary alveolar macrophage cytotoxicity investigation of irregular shape mineral dusts].

In order to study the damage mechanism of mineral dusts on the pulmonary alveolar macrophages (AM), the changes of their death ratio, malandialdthyde (MDA) content and activities of lactate dehydrogenase (LDH) and superoxide dismutase (SOD) were measured. And the technique of cell culture in vitro was used to investigate the cytotoxicity of six mineral dusts (twelve crystal habits) from twelve mineral deposits. The results showed that wollstonite and clinoptilolite had no AM cytotoxicity while other fibrous and grainy mineral dusts could damage pulmonary AM in various degrees. The cytotoxicity of fibrous mineral dusts was greater than that of the grainy ones, and the cytotoxicity of dusts was positively correlated with the active OH- content in dusts, but not necessarily so with its SiO2 content. The high pH values produced by dust was unfavorable for the cells survival and the dusts with a low bio-resistance were safe for cells. The content of variable valence elements in dusts could influence their cytotoxicity and the surface charge of dusts was not a stable factor on their toxicity. It indicates that the shape of mineral dusts is one of the factors affecting cytotoxicity, and that the cytotoxicity of mineral dusts mainly depends on their properties.

Animals↗