Longitudinal changes in cardiovascular disease-related proteins in welders.

OBJECTIVE: Occupational exposure to welding fumes is linked to a higher risk of cardiovascular disease; however, the threshold exposure level is unknown. Here, we aimed to identify changes in proteins associated with cardiovascular disease in relation to exposure to welding fumes. METHODS: Data were obtained from two timepoints six years apart for 338 non-smoking men (171 welders, 167 controls); of these, 174 (78 welders, 96 controls) had measurements available at both timepoints. Exposure was measured as personal respirable dust (adjusted for personal protective equipment), welding years, and cumulative exposure. Proximity extension assays were used to measure a panel of 92 proteins involved in cardiovascular processes in serum samples. Linear mixed models were used for longitudinal analysis. The biological functions and diseases related to the identified proteins were explored using the Ingenuity Pathway Analysis software. RESULTS: At both timepoints, the median respirable dust exposure was 0.7 mg/m3 for the welders. Seven proteins were differentially abundant between the welders and controls and increased incrementally with respirable dust: FGF23, CEACAM8, CD40L, PGF, CXCL1, CD84, and HO1. CD84 was significant after adjusting for multiple comparisons. These proteins have been linked to disorders of blood pressure, damage related to clogged blood vessels, and chronic inflammatory disorders. CONCLUSION: Exposure to mild steel welding fumes below current occupational exposure limits for respirable particles and welding fumes in Europe and the US (1-5 mg/m3) was associated with changes in the abundance of proteins related to cardiovascular disease. Further research should evaluate the utility of these proteins as prospective biomarkers of occupational cardiovascular disease.

The potential of Gol-e-Gohar iron ore mine airborne dust to induce toxicity in human lung A549 cells.

Airborne particulates in iron ore mining are a risk factor for adverse human lung effects. In this study, fine particulates deposited on surfaces of about 1.5 m above the ground and 6 meters from a milling unit of the Gol-e-Gohar iron ore mine were collected through wipe sampling. Dust particles less than 5 µm in diameter were separated with an electronic sieve. Aliquots were prepared from the sieved iron ore dust estimated to be equivalent to respiratory exposure in the iron ore mill in the concentrations of 1, 5, 10, 50, 100, and 250 µg/mL, which were intended to represent equivalent inhaled doses from working one month to a working life (25 years) in the mine. The airborne concentration of respirable particles was about five times the threshold limit value given (TLV®) for iron oxide published by the American Conference of Governmental Industrial Hygienists. The in vitro toxicity range was estimated to be equivalent to an accumulated dose associated with working from one month to a working life in the mine. Treatment of the A549 cells resulted in decreased dehydrogenase activity and cell glutathione content and increased reactive oxygen species (ROS) generation, mitochondrial membrane permeability, and cell apoptosis-necrosis rates. The results of this study revealed the possibility of lung damage at cell doses for respirable airborne iron oxide particles estimated to be equivalent to accumulated lifetime exposures among Gol-e-Gohar miners. Further studies are recommended to investigate the effect of actual contaminants in the workplace on the occurrence of health effects on workers.

Respirable dust and crystalline silica exposure among rice mill workers of northeast India.

Crystalline silica is a Group I lung carcinogen primarily known as a causative agent for silicosis. A study was performed to quantify respirable dust, and respirable crystalline silica (RCS) in the rice mills of northeast India. Seventy-two respirable dust samples were collected from the worker's breathing zone from four rice mills at three locations: feeding, sieving, and polishing sections for two paddy varieties: Ranjit and Sali. The National Institute of Occupational Safety and Health (NIOSH), method #7602, was used to determine RCS. The results show that geometric mean TWA dust and RCS emissions in the rice mills varied from 3.97 to 455.00 mg/m3 and 0.02 to 5.38 mg/m3, respectively. RCS exposures were higher during milling of the Sali variety paddy (GM: 0.76 mg/m3) than the Ranjit variety paddy (GM: 0.25 mg/m3). Respirable dust and RCS emissions were considerably higher in the feeding and sieving sections than in the polishing section. Respirable dust and RCS exposure varied significantly (p < 0.001) with paddy variety. Respirable dust and RCS were highly correlated for different rice mills; however, the proportion of RCS in the dust was higher in the Sali variety paddy than in the Ranjit variety paddy. RCS exposure to the workers at the feeding and sieving sections was observed to be higher than the occupational exposure limits (OELs) published by Safe Work Australia, American Conference of Governmental Industrial Hygienists (ACGIH), National Institute for Occupational Safety and Health (NIOSH), Health and Safety Executive (HSE), and Factories Amendment Act, 1987, Government of India.

Hydrophobic/oleophobic nanofibrous filter media with bead-on-string structure for efficient personal protection of dust in mines.

Pneumoconiosis in mines occupied more than 90% of the total number of occupational diseases, poses tremendous pressure and challenges on the development of personal protection materials with high dust filtration efficiency and long-lasting comfortable wearing. In this study, a kind of polyethylene terephthalate (PET) based filter media with the bead-on-string structure and hydrophobic/oleophobic property was designed and fabricated by electrospinning technology. Nanoscale silicon dioxide (SiO2NPs) and fluorinated polyurethane (PU) used in this work were benefited for the microstructure, surface energy and hydrophobic/oleophobic property, respectively. The morphology and composition of the membranes were conducted by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and fourier transform infrared spectroscopy (FTIR). Furthermore, the filtration performance, pressure drop, moisture permeability and breathing comfortable performance were measured for the study of personal protection of dust. The results showed that at the air flow of 85 L min-1, PET/SiO2/FPU double-layer nanofibrous membrane showed high filtration efficiency and low pressure drop with the filtration efficiency of 99.96%, pressure drop of 142.5 Pa and quality factor of 0.055 Pa-1, respectively. A long term of 24 h water vapor test had proved that this membrane held an outstanding moisture permeability ability of 5296.325 g (m2 24 h)-1. Compared with the commercial 3701CN filter media, the advantages of the regular breathing frequency and strong heart rate control ability indicated that this PET/SiO2/FPU double-layer membrane had the better wearing comfortable performance with broad application prospects in the personal protection of dust in mines.

Exposure to dust and respiratory health among Australian miners.

PURPOSE: Occupational exposure to dust has been recognised as a significant health hazard to mine workers. This study aimed to investigate the association between exposure to inhalable (INH) and respirable (RES) dust and respiratory health among mine workers in Western Australia using an industry-wide exposure database. METHODS: The database comprised cross-sectional surveys conducted by mining companies for the period 2001-2012. The study population consisted of 12,797 workers who were monitored for exposure to INH and RES dust and undertook health assessments including a respiratory questionnaire and spirometry test. RESULTS: Despite the general trend of declining exposure to both INH and RES dust observed over the 12 years period, mine workers reported a higher prevalence of phlegm and cough when exposed to elevated concentrations of INH and RES dust. Logistic regression analysis further confirmed the positive association between INH dust exposure and the prevalence of phlegm with an adjusted odds ratio of 1.033 (95% CI 1.012-1.052). Overall, 6.3% of miners might have potential airway obstruction, and exposure to INH dust was associated with impaired lung function parameters. CONCLUSION: Exposure levels of INH and RES dust particles among mine workers have reduced considerably and were well below currently legislated occupational exposure limits. However, given the reported higher prevalence of phlegm and cough among those with elevated dust concentrations, there is a continued need for effective dust exposure monitoring and control in the mineral mining industry.

Occupational exposure to respirable crystalline silica among US metal and nonmetal miners, 2000-2019.

BACKGROUND: In metal and nonmetal (M/NM) mines in the United States, respirable crystalline silica (RCS) exposures are a recognized health hazard and a leading indicator of respiratory disease. This study describes hazardous exposures that exceed occupational exposure limits and examines patterns of hazardous RCS exposure over time among M/NM miners to better inform the need for interventions. METHODS: Data for this study were obtained from the Mine Safety and Health Administration (MSHA) Open Government Initiative Portal for the years 2000-2019, examining respirable dust samples with MSHA-measured quartz concentration >1%. Descriptive statistics for RCS were analyzed for M/NM miners by year, mine type, sector, commodity, occupation, and location in a mine. RESULTS: This study found the overall geometric mean (GM) for personal exposures to RCS was 28.9 µg/m3 (geometric standard deviation: 2.5). Exposures varied significantly by year, mine type, sector, commodity, occupation, and location in a mine. Overall, the percentages of exposures above the MSHA permissible exposure limit (PEL for respirable dust with >1% quartz, approximately 100 µg/m3 RCS) and the National Institute for Occupational Safety and Health RCS recommended exposure limit (REL, 50 µg/m3 ) were 11.8% and 27.3%, respectively. GM exposures to RCS in 2018 (45.9 µg/m3 ) and 2019 (52.9 µg/m3 ) were significantly higher than the GM for all years prior. The overall 95th percentile of RCS exposures from 2000 to 2019 was 148.9 µg/m3 , suggesting a substantial risk of hazardous exposures above the PEL and REL during the entire period analyzed. CONCLUSIONS: The prevalence of high exposures to RCS among M/NM miners continues in the past 20 years and may be increasing in certain settings and occupations. Further research and intervention of the highest exposures are needed to minimize the risks of acquiring silica-induced respiratory diseases.

Use of prototype side stream filtration system to control dust levels in a commercial swine farrowing building.

Swine meat provides an essential global food source. Due to economies of scale, modern U.S. swine production primarily occurs indoors to maintain an optimal environment across the stages of swine production. Indoor concentrations of dust and contaminant gases in swine production buildings increase in the winter months due to reduced ventilation to optimal building temperature. In this study, an engineering control technology designed to recirculate the air in a swine farrowing room through a mobile air handling unit containing high-efficiency particulate filters was presented. A mobile solution could be easily deployed as an intervention method if an infectious disease outbreak occurs at a swine operation. The performance of this control technology was evaluated following deployment in a production farrowing barn for a period of 6 weeks during the winter in the Midwestern United States. Contaminant concentrations of inhalable dust, respirable dust, and carbon dioxide were measured in the room treated by the prototype system and compared to contaminant concentrations measured in an untreated "control" room. Over 6 weeks, the mean inhalable and respirable dust concentrations observed during the study period for the "treatment" room were 2.61 and 0.14 mg/m3, respectively, compared to 3.51 and 0.25 mg/m3, respectively, for the control room. The mobile recirculating ventilation system, operating at a flow rate of 45 m3/min (5 room air exchanges per hour), reduced the inhalable dust by 25% and respirable dust by 48% as measured with a real-time aerosol monitor, when compared to the control room. In addition, no concentration differences in carbon dioxide and relative humidity between the treatment and the control rooms were observed. Inhalable and respirable concentrations of dust were significantly reduced (p = 0.001), which demonstrates an essential improvement of the air quality that may prove beneficial to reduce the burden of disease among both workers and animals.

Study on the optimal parameter range of droplet-wrapped respirable dust in spray dustfall by mesoscopic method.

Coal miners on the fringes of cities are often exposed to respirable dust hazards. Spray is one of the most effective dust reduction measures. When studying the coupling and collision behavior of droplets and dust particles, it is helpful to optimize the parameter range of the droplets to capture dust particles at the mesoscopic level, to determine the effect of the spray field on the dust particles at the macroscopic level. In this study, the volume of fluid (VOF) method was used to track the interface of multiphase flow. A numerical simulation of 13 working conditions was carried out using the control variable method. Based on the numerical simulation results, we obtained the optimal parameter range for dust to be encapsulated by droplets. To confirm the reliability of the simulation, we independently developed an experimental system and conducted experiments. The simulation results obtained were measured using the experimental system, and an optimal droplet parameter range of 7 µm to settle dust in a coal mining face was determined. Numerical simulation using a mesoscopic method to study dust-spray coupling produced reliable results, which can be used in the practical application of spray dust reduction and has wider relevance for practical engineering.

Thermogravimetric analysis of respirable coal mine dust for simple source apportionment.

Resurgence of coal mine dust lung diseases in the central Appalachian region of the United States and elsewhere has spurred a range of efforts to better understand respirable coal mine dust (RCMD) exposures and sources. Thermogravimetric analysis (TGA) of RCMD samples can enable the dust mass to be fractionated into three main components: coal, non-carbonate minerals, and carbonates. These are expected to approximate, respectively, the three primary dust sources in many underground mines: the coal seam being mined, the surrounding rock strata (i.e., typically dominated by non-carbonate minerals) being drilled or mined along with the coal, and the rock dust products (i.e., typically made from carbonate-rich limestone or dolostone) being applied in the mine to mitigate explosibility hazards. As proof of concept, TGA was applied to respirable dust samples that were laboratory-generated from real source materials representing 15 mines. Except in the case of two mines, compositional results were generally consistent with expectations. TGA was also applied to RCMD samples collected in standard locations of 23 mines (including the 15 mines represented by the dust source materials). Results showed significantly different compositions with respect to sampling location and geographic region (i.e., within and outside of central Appalachia). To further interpret the RCMD results, a simple source apportionment model was built using the dust compositions yielded from the source materials analysis. Model results indicated that, on average, about twice as much dust was sourced from mining into rock strata than from mining the target coal seam. This finding is particularly important for mines extracting relatively large amounts of rock along with the coal or for mines that frequently encounter high-silica rock strata.

Development of a size-selective sampler combined with an adenosine triphosphate bioluminescence assay for the rapid measurement of bioaerosols.

In this study, a size-selective bioaerosol sampler was built and combined with adenosine triphosphate (ATP) bioluminescence assay for measuring the bioaerosol concentration more rapidly and easily. The ATP bioaerosol sampler consisted of a respirable cyclone, an impactor to collect bioaerosols onto the head of a swab used for ATP bioluminescence assay, a swab holder, and a sampling pump. The collection efficiency of the impactor was tested using aerosolized sodium chloride particles and then the particle diameter corresponding to the collection efficiency of 50% (cut-off diameter) was evaluated. The experimental cut-off diameter was 0.44 µm. The correlations between ATP bioluminescence (relative light unit; RLU) from commercially available swabs (UltraSnap and SuperSnap, Hygiena, LLC, U.S.A.) and colony forming unit (CFU) were examined using Escherichia coli (E. coli) suspension and then the conversion equations from RLU to CFU were obtained. From the correlation results, the R2 values of UltraSnap and SuperSnap were 0.53 and 0.81, respectively. The conversion equations were the linear function and the slopes of UltraSnap and SuperSnap were 633.6 and 277.78, respectively. In the lab and field tests, the ATP bioaerosol sampler and a conventional Andersen impactor were tested and the results were compared. In the lab tests, concentrations of aerosolized E. coli collected using the sampler were highly correlated to those from the Anderson impactor (R2 = 0.85). In the field tests, the concentrations measured using the ATP bioaerosol sampler were higher than those from the Andersen impactor due to the limitations of the colony counting method. These findings confirm the feasibility of developing a sampler for rapid measurement of bioaerosol concentrations, offering a compact device for measuring exposure to bioaerosols, and an easy-to-use methodological concept for efficient air quality management.

Early radiographic pneumoconiosis is associated with impaired exercise gas exchange among coal miners with normal resting spirometry.

RATIONALE: We sought to determine if radiographic pneumoconiosis predicts abnormal gas exchange during exercise in coal mine workers with preserved resting lung function. METHODS: We analyzed data from former coal miners seen between 2006 and 2014 in a single clinic specializing in black lung evaluations. We limited the analysis to those with normal resting spirometry and an A-a gradient at peak exercise ≥10 mmHg. We used multivariable logistic regression to estimate predictors of A-a gradient widened to >150% of the reference value. We focused on chest radiographs consistent with pneumoconiosis, taking into account higher silica exposure mining activities and years underground, and adjusting for cigarette smoking, obesity, and coronary artery disease. RESULTS: Of 5507 miners, we analyzed data for 742 subjects with normal spirometry and all key clinical variables available, of whom 372 (50.1%) had radiographic evidence of pneumoconiosis. All but 21 had small opacity profusion of less than 2/1. The median A-a gradient at peak exercise was 108% of reference value (interquartile range, 81%-141%). In the multivariable analysis, radiographic pneumoconiosis was associated with increased odds of widened A-a gradient (odds ratio [OR], 2.47; 95% confidence interval [CI], 1.7-3.7). Limited to 660 subjects with normal diffusing capacity for carbon monoxide, the odds were similarly increased (OR, 3.20; 95% CI, 1.5-3.6). DISCUSSION: Among coal miners with preserved resting lung function, radiographic evidence of early pneumoconiosis more than doubled the odds of abnormal exercise physiology. Impairment in pneumoconiosis occurs in early disease and may only be evident on exercise testing.

Occupational exposure to crystalline silica in artificial stone processing.

Respirable Crystalline Silica (RCS) is a hazardous substance with known effects that can be well correlated with exposure levels that still persist in many traditional sectors, such as construction or stone processing. In the past decade, exposure scenarios for RCS have been found in the sector of artificial stone processing. The aim of this study is to evaluate the levels of RCS in facilities specialized in the production of artificial stone countertops and other accessories for the furnishing of kitchens, bathrooms, and offices after the introduction of some preventive technical measures such as wet processing or local exhaust ventilation systems. The study involved 51 subjects in four facilities. Personal silica exposure assessment was carried out using GS3 cyclones positioned in the breathing zone during the work shift. Quantitative determination of silica was carried out by X-ray diffraction analysis. Respirable dust levels were in the range 0.046-1.154 mg/m3 with RCS levels within the range <0.003-0.098 mg/m3. The highest exposure was found in dry finishing operations. Although there was a remarkable reduction in RCS exposure levels compared to what was observed in the past before the introduction of preventive measures, the data still showed hazardous exposure levels for some of the monitored activities.

Experimental study on dust removal optimization of shearer external spray in air velocity.

In order to clarify the influence of air velocity on the atomization effect of shearer external spray and optimize dust suppression performance, the dust removal experiment was carried out by utilizing the self-designed external spray experiment platform. The effect of three kinds of air velocity on the atomization effect of main spray parameters was investigated to clarify the influence of air velocity on the atomization effect of shearer external spray and optimize dust suppression performance. The results showed that the influence of air velocity on droplet size and distribution width of the droplet size was slightly less than the spray pressure. The average diameter of the droplet was 54.211 µm, and the particle size distribution of the droplet was more uniform and concentrated when air velocity was 2 m/s, the pressure was 5 MPa and nozzle diameter was 1.0 mm. When the air velocity was less than 2 m/s and the spray pressure was 3-5 MPa, the atomization effect was better by using 1.0 or 1.2 mm diameter nozzle. Through on-site applications and optimization, the leeward total dust removal efficiency of the shearer can reach 79.43%, and the maximum increase range can reach 18.51 percentage points. The respiratory dust removal efficiency of the shearer can reach 87.45%, and the maximum increase range can reach 11.87 percentage points.

Temporal trends in respirable dust and respirable quartz concentrations within the European industrial minerals sector over a 15-year period (2002-2016).

OBJECTIVES: Since 2000 the European Industrial Minerals Association's Dust Monitoring Programme (IMA-DMP) has systematically collected respirable dust and respirable quartz measurements from 35 companies producing industrial minerals. The IMA-DMP initiative allowed for estimating overall temporal trends in exposure concentrations for the years 2002-2016 and for presenting these trends by type of mineral produced, by jobs performed and by time of enrolment into the DMP. METHODS: Approximately 32 000 personal exposure measurements were collected during 29 sampling campaigns during a 15-year period (2002-2016). Temporal trends in respirable dust and respirable quartz concentrations were studied by using linear mixed effects models. RESULTS: Concentrations varied widely (up to three to four orders of magnitude). However, overall decreases in exposure levels were shown for the European minerals industry over the 15-year period. Statistically significant overall downward temporal trends of -9.0% and -3.9% per year were observed for respirable dust and respirable quartz, respectively. When analyses were stratified by time period, no downward trends (and even slight increasing concentrations) were observed between 2008 and 2012, most likely attributable to the recent global economic crisis. After this time period, downward trends became visible again. CONCLUSIONS: Consistent and statistically significant downward trends were found for both exposure to respirable dust and respirable quartz. These downward trends became less or even reversed during the years of the global economic crisis. To our knowledge, this is the first time that analyses of long-term temporal trends point at an effect of a global economic crisis on personal exposure concentrations of workers from sites across Europe.

The toxicity of respirable South African mine tailings dust in relation to their physicochemical properties.

INTRODUCTION: Decades of mining in South Africa has given rise to hundreds of tailings storage facilities (TSFs) and several tonnes of waste. These TSFs have contributed to air pollution due to the lack of proper rehabilitation measures. Currently, it is not known whether tailings emissions could be the cause of respiratory-related ill effects. In addition, the physicochemical properties that may govern their toxicity have not yet been identified. AIM: The aim of this research was to determine the toxicity of tailings dust and identify the physicochemical properties likely to govern toxicity. METHODS: Dust samples were collected from five TSFs in the Gauteng and North West Provinces of South Africa and sieved to enrich the airborne particle fraction more likely to be inhaled. Thereafter, their physicochemical characteristics were assessed i.e. size distribution, specific surface area, shape, surface elemental composition, mineral composition, total elemental composition and surface activity. In addition, the toxicity and cellular internalization of the particles were assessed using the BEAS-2B epithelial and U937 monocytic-macrophage cell lines.Results: The results showed that all tailings dusts showed toxicity, particularly in the BEAS-2B cell line. This toxicity could have been governed by either their elemental composition, e.g. high transition elements e.g. Fe, Cu, Cr and V in the dusts from TSF 4, or a combination of other physicochemical properties, e.g. higher quartz content, lower size and higher surface area in the dusts from TSF 1. CONCLUSION: These results provide mechanistic evidence to support future epidemiological studies attempting to link tailings dust exposure to adverse health effects.

Multiple environmental and psychosocial work risk factors and sleep disturbances.

BACKGROUND: This study aimed to investigate the relationship between multiple psychosocial and environmental work risk factors and sleep disturbances. METHODS: This cross-sectional study was conducted among 90 workers in a brick factory in Iran. The health and safety executive (HSE) tool, Epworth Sleepiness Scale (ESS), and Stop-Bang questionnaire were used to determine psychosocial factors, subjective sleepiness, and obstructive sleep apnea (OSA), respectively. Standard objective methods were used to assess the environmental risk factors, including noise, light, heat stress, and respirable particles. RESULTS: Most psychosocial and all environmental work factors were moderately to highly correlated to the ESS score. There were also moderate correlations between the demands (including work load, work patterns, and work environment), role (including a clear understanding of the employees about their role in the organization), and lighting variables and the Stop-Bang score. The results of multivariate logistic regression analysis showed that job control, wet bulb globe temperature (WBGT), and respirable dust were predictive of an ESS score indicating abnormal sleep status and noise was predictive of a Stop-Bang score predictive of OSA. CONCLUSIONS: The results suggest that stressors, especially noise, heat stress, and respirable dust, are related to the employees' indices of sleep disturbance independent of other potential workplace confounding factors. These results can highlight the importance of considering multiple psychosocial and environment work risk factors for implementing occupational health and ergonomics interventional programs to prevent sleep disturbances in the workforce.

[Dose-response relationship analysis between cumulative coal dust exposure and pneumoconiosis risk].

Objective: To explore the dose-response relationship between the cumulative coal dust exposure and the cumulative prevalence rate of pneumoconiosis among the coal miners, and to provide a basis for the revision of exposure concentration limits standards of the respirable coal dust and the total dust. Methods: A retrospective cohort study was conducted to study the coal miners in 11 state-owned coal mines from January to August 2013. 21000 coal miners in the 9 coal mines were adopted in the furthre study after the bias treatment.The occupational health records of coal miners from the date of coal production to the end of 2012 in each coal mine were collected. Based on the cumulative dust exposure group of the respirable coal dust and that of the total dust, both the miner's cumulative prevalence rate of pneumoconiosis were calculated by the life table method respectively. The dose-response relationship between the cumulative coal dust exposure and pneumoconiosis risk was established (subject to logistic regression model) . Assuming the cumulative prevalence rate is not higher than 1% after 30 or 25 years of exposure to coal dust and the safety factor is 1.2, the exposure concentration limits of the respirable coal dust and the total dust were calculated by the logistic regression equations with one-sided interval statistical control. Results: There were 3224 pneumoconiosis patients (15.35%) altogether. The dose-response relationship between the cumulative respirable coal dust exposure and the cumulative prevalence rate of pneumoconiosis is a logistic regression equation logistic(r)=5.649lgDr-16.573 (R(2)=0.925) , and the legistic regression equation for the total dust, is logistic(t)=5.712lgDt-18.767 (R(2)=0.897) . When the prevalence rate of pneumoconiosis after 30 years of exposure to coal dust is not higher than 1%, the exposure concentration limits of the respirable coal dust and that of total dust contact are 2.2 mg/m(3) and 4.8 mg/m(3), which are similar to those of national occupational health standards of China (2.5 mg/m(3) and 4 mg/m(3)) . When the prevalence rate of pneumoconiosis after 25 years of exposure to coal dust is not higher than 1%, the exposure concentration limits of the respirable coal dust is 2.7 mg/m(3). Conclusion: It is recommended to strictly implement the current national occupational health standard and abolish the relevant safety production industry standard.

Reconstructing historical exposures to elongate mineral particles (EMPs) in the taconite mining industry for 1955-2010.

As part of ongoing epidemiological studies for assessing the association between exposure to dust from taconite operations and the development of respiratory diseases, the goal of this study was to reconstruct the exposures of workers to elongate mineral particle (EMP) in the Minnesota taconite mining industry from 1955-2010. Historical NIOSH-7400 and equivalent EMP personal exposure data were extracted from two sources: (1) the Mine Safety and Health Administration (MSHA) online database recorded for all inspection results since 1978 with 655 EMP monitoring records from 1978-2010 for 13 MSHA Mine IDs associated with this study; and (2) the mining companies' internal monitoring reports contained 96 personal EMP exposure records. NIOSH-7400 EMP personal exposures were measured for workers in different jobs in all active mines in 2010 by obtaining 1,285 personal samples. After data treatment, all data were grouped into seven mines and eight departments. Within each mine-department, the yearly EMP mean concentration in f/cc for each year of operation was predicted using two approaches. The performance of two approaches varied by situation. The assumptions underlying each approach described in this article have limitations. A linear regression based on limited historical measurements and those made in 2010-2011 (Approach 1) does not yield reasonable and plausible values of the slope. Approach 2 assumes that the EMP and the respirable dust in the same department share the same historical time trend. This approach allowed us to avail of the more reasonable slope estimates from the historical respirable dust data set and yielded more plausible historical exposure estimates for most locations. This work with two different job exposure matrix (JEMs) provides a unique research opportunity to study the potential impact of exposure assessment to epidemiological results. Both JEMs are being used to assess associations between EMP and respiratory disease in epidemiological studies.

[Design and Evaluation of Miniature Cyclones for Dust Indicators].

Dust indicators based on light scattering photometers are widely used to measure aerosol concentrations in work environments. These concentrations at workplaces in Japan are measured by these dust indicators and calibrated by mass concentration in order to control workers' exposure to dust. The mass concentration in a specific point in a workplace is measured simultaneously with a dust indicator. The mass concentration of the respirable fraction of dust particles should be determined by the gravimetric method with low volume air samplers or other devices, but some dust indicators are not equipped with a size separator for respirable fraction, and we used to get unstable results at the calibration. In this study, we designed miniature cyclones for a dust indicator and evaluated their performances of respirable fraction and PM2.5 fraction.

Experimental study on effects of drilling parameters on respirable dust production during roof bolting operations.

Underground coalmine roof bolting operators exhibit a continued risk for overexposure to airborne levels of respirable coal and crystalline silica dust from the roof drilling operation. Inhaling these dusts can cause coal worker's pneumoconiosis and silicosis. This research explores the effect of drilling control parameters, specifically drilling bite depth, on the reduction of respirable dust generated during the drilling process. Laboratory drilling experiments were conducted and results demonstrated the feasibility of this dust control approach. Both the weight and size distribution of the dust particles collected from drilling tests with different bite depths were analyzed. The results showed that the amount of total inhalable and respirable dust was inversely proportional to the drilling bite depth. Therefore, control of the drilling process to achieve proper high-bite depth for the rock can be an important approach to reducing the generation of harmful dust. Different from conventional passive engineering controls, such as mist drilling and ventilation approaches, this approach is proactive and can cut down the generation of respirable dust from the source. These findings can be used to develop an integrated drilling control algorithm to achieve the best drilling efficiency as well as reducing respirable dust and noise.