Impact of air distribution on efficiency of dust capture from metal grinding--bench test method

According to the Machinery Directive 2006/42/EC, one of the essential requirements relating to occupational safety and health hazards is to prevent dust pollution emitted by machinery during the implementation processes. Research on evaluation of emissions from machinery, according to the method of test bench using tracer gases, are currently being conducted in CIOP-PIB. This article presents some aspects of dust emission and efficiency of local exhaust ventilation (LEV) during metal grinding. Studies were performed with 10 sources of dust emissions during grinding. To evaluate the pollutants emission in the process of grinding metal products sulfur hexafluoride (SF(6)) was selected as a tracer gas. The results show that wherever dust is emitted, the LEV should be supported by the general ventilation. Ensure good interaction between all elements of modifying the air flow and the spread of pollutants in the surroundings of the LEV is essential to effective protection of human working zone against pollutants. We used five variants of ventilation: ventilation turned off, the LEV, one-way general ventilation, mixed general ventilation and displacement general ventilation. An increase in the efficiency of dust capture depending on the source of emission by 2.5-14% was observed. This confirms that characteristics of flow resulting from the operation of ventilation is important in the spread of pollutants in the room.

[Analysis of urine cadmium and blood cadmium of workers before and after the cadmium dust control]

OBJECTIVE

To analyze the urinary cadmium, blood cadmium and urinary beta2-MG of workers in a zinc powder processing plant before and after the cadmium dust control, and to explore the effects of dust control on the prevention and treatment of cadmium hazards.

METHODS

The on-site occupational hazard survey was used to investigate the changes of urine cadmium, blood cadmium and beta3-MG of 84 workers exposed to cadmium before and after the treatment by self-control analysis for evaluating the effects of dust control measures in a zinc powder processing plant.

RESULTS

After treatment of the cadmium dust, the geometric mean of zinc dust in the workplace significantly decreased from 3.38 mg/m3 to 2.22 mg/m3 (P < 0.01). The geometric mean concentration of blood cadmium [(2.19 +/- 1.19) microg/L] and urine cadmium [(1.96 +/- 0.74) microg/g Cr] before treatment were significantly higher than those of one year [(1.63 +/- 0.83) microg/L] and [(1.25 +/- 0.83) microg/g Cr] and two years [(1.36 +/- 0.95) microg/L] and [(0.94 +/- 0.72) microg/g Cr] after the cadmium dust control (P < 0.01), respectively. The positive correlations analysis between urine cadmium and blood cadmium concentration of one and two years before and after the cadmium dust treatment implied that there was significant difference (r = 0.466, P < 0.01).

CONCLUSION

Dust treatment could reduce the impact of low concentration cadmium on the urine cadmium and blood cadmium concentrations of the workers exposed to cadmium, and effectively prevent the cadmium poisoning.

Nurse case management and housing interventions reduce allergen exposures: the Milwaukee randomized controlled trial

OBJECTIVE

We examined the impact of a combination of home environmental interventions and nurse case management services on total settled dust loadings and on allergen concentrations in the homes of asthmatic children. METHODS Using a randomized longitudinal controlled trial study design, we randomly assigned homes of asthmatic children in Milwaukee to either a control (n = 64) or an intervention (n = 57) group. Control group homes received a visual assessment, education, bed/pillow dust mite encasings, and treatment of lead-based paint hazards. The intervention group received these same services plus nurse case management that included tailored, individual asthma action plans, provision of minor home repairs, home cleaning using special vacuuming and wet washing, and integrated pest management. Dust vacuum samples were collected from measured surface areas of floors in the TV room, kitchen, and child's bedroom at baseline and at three-, six-, and 12-month follow-up visits. Dust loading (mass per surface area) is a means of measuring total dust and the total amount of allergen present.

RESULTS

For the intervention group, geometric mean dust loadings declined significantly from baseline (39 milligrams per square foot [mg/ft2]) to postintervention (11 mg/ft2) (p < 0.001). Baseline dust loading, treatment group, visit, and season were significant predictors of follow-up dust loadings. Mean post-intervention dust loadings were 72% higher in the control group. The total amount of allergen in settled house dust declined significantly following the intervention because total dust loading declined; the concentration of allergens in settled dust did not change significantly.

CONCLUSION

The combination of nurse case management and home environmental interventions promotes collaboration between health and housing professionals and is effective in reducing exposures to allergens in settled dust.

[Investigation about prevention behavior for dust workers in machinery, ceramic, and metallurgy industry]

OBJECTIVE

The purposes of this thesis were to study the behavior about workers exposed to dust and provide scientific basis for health promotion.

METHODS

We designed a questionnaire and carry it on the 746 dust workers in the 3 representative corporations of Machinery, Ceramic, and Metallurgy Industry. All data were input into computer. And a database was established with Excel. SPSS11.5 statistical analysis software was used to analyze the influence on protecting behavioral between the application of qualifications, different jobs, training or protection, and other aspects etc.

RESULTS

The rates were 94.4% and 75.3% about the regular physical examination and requirements for protective equipment. The rate of choosing an effective way of protection was generally low (15.4%). There was significant difference for among different educational background workers (P < 0.01). The rates of choosing an effective way of protection (20.3%), the regular physical examination (98.3%) and requirements for protective equipment (86.4%) in the dust workers who participated in the training of dust protection were superior than those who did not participated in the training. There was the significant difference (P < 0.05, P < 0.01). There was the significant difference for the rate of effective way of protection, regular physical examination, and requirements for protective equipment among the different corporations (P < 0.05).

CONCLUSIONS

Dust workers' using rate about the choosing an effective way of protection was generally low in Machinery, Ceramic, and Metallurgy Industry. Those who were not educated had a lower using rate about the protection behavior, regular physical examination, and requirements for protective equipment than those educated.

Effectiveness of dust control methods for crystalline silica and respirable suspended particulate matter exposure during manual concrete surface grinding

Concrete grinding exposes workers to unacceptable levels of crystalline silica dust, known to cause diseases such as silicosis and possibly lung cancer. This study examined the influence of major factors of exposure and effectiveness of existing dust control methods by simulating field concrete grinding in an enclosed workplace laboratory. Air was monitored during 201 concrete grinding sessions while using a variety of grinders, accessories, and existing dust control methods, including general ventilation (GV), local exhaust ventilation (LEV), and wet grinding. Task-specific geometric mean (GM) of respirable crystalline silica dust concentrations (mg/m³ for LEV:HEPA-, LEV:Shop-vac-, wet-, and uncontrolled-grinding, while GV was off/on, were 0.17/0.09, 0.57/0.13, 1.11/0.44, and 23.1/6.80, respectively. Silica dust concentrations (mg/m³ using 100-125 mm (4-5 inch) and 180 mm (7 inch) grinding cups were 0.53/0.22 and 2.43/0.56, respectively. GM concentrations of silica dust were significantly lower for (1) GV on (66.0%) vs. off, and (2) LEV:HEPA- (99.0%), LEV:Shop-vac- (98.1%) or wet- (94.4%) vs. uncontrolled-grinding. Task-specific GM of respirable suspended particulate matter (RSP) concentrations (mg/m³ for LEV:HEPA-, LEV:Shop-vac-, wet-, and uncontrolled grinding, while GV was off/on, were 1.58/0.63, 7.20/1.15, 9.52/4.13, and 152/47.8, respectively. GM concentrations of RSP using 100-125 mm and 180 mm grinding cups were 4.78/1.62 and 22.2/5.06, respectively. GM concentrations of RSP were significantly lower for (1) GV on (70.2%) vs. off, and (2) LEV:HEPA- (98.9%), LEV:Shop-vac- (96.9%) or wet- (92.6%) vs. uncontrolled grinding. Silica dust and RSP were not significantly affected by (1) orientation of grinding surfaces (vertical vs. inclined); (2) water flow rates for wet grinding; (3) length of task-specific sampling time; or, (4) among cup sizes of 100, 115 or 125 mm. No combination of factors or control methods reduced an 8-hr exposure level to below the recommended criterion of 0.025 mg/m³ for crystalline silica, requiring further refinement in engineering controls, administrative controls, or the use of respirators.

Fugitive dust emission source profiles and assessment of selected control strategies for particulate matter at gravel processing sites in Taiwan

Particles emitted from gravel processing sites are one contributor to worsening air quality in Taiwan. Major pollution sources at gravel processing sites include gravel and sand piles, unpaved roads, material crushers, and bare ground. This study analyzed fugitive dust emission characteristics at each pollution source using several types of particle samplers, including total suspended particulates (TSP), suspended particulate (PM10), fine suspended particulate (PM2.5), particulate sizer, and dust-fall collectors. Furthermore, silt content and moisture in the gravel were measured to develop particulate emission factors. The results showed that TSP (< 100 microm) concentrations at the boundary of gravel sites ranged from 280 to 1290 microg/m3, which clearly exceeds the Taiwan hourly air quality standard of 500 microg/m3. Moreover, PM10 concentrations, ranging from 135 to 550 microg/m3, were also above the daily air quality standard of 125 microg/m3 and approximately 1.2 and 1.5 times the PM2.5 concentrations, ranging from 105 to 470 microg/m3. The size distribution analysis reveals that mass mean diameter and geometric standard deviation ranged from 3.2 to 5.7 microm and from 2.82 to 5.51, respectively. In this study, spraying surfactant was the most effective control strategy to abate windblown dust from unpaved roads, having a control efficiency of approximately 93%, which is significantly higher than using paved road strategies with a control efficiency of approximately 45%. For paved roads, wet suppression provided the best dust control efficiencies ranging from 50 to 83%. Re-vegetation of disturbed ground had dust control efficiencies ranging from 48 to 64%.

Laboratory evaluation to reduce respirable crystalline silica dust when cutting concrete roofing tiles using a masonry saw

Respirable crystalline silica dust exposure in residential roofers is a recognized hazard resulting from cutting concrete roofing tiles. Roofers cutting tiles using masonry saws can be exposed to high concentrations of respirable dust. Silica exposures remain a serious threat for nearly two million U.S. construction workers. Although it is well established that respiratory diseases associated with exposure to silica dust are preventable, they continue to occur and cause disability or death. The effectiveness of both a commercially available local exhaust ventilation (LEV) system and a water suppression system in reducing silica dust was evaluated separately. The LEV system exhausted 0.24, 0.13, or 0.12 m(3)/sec of dust laden air, while the water suppression system supplied 0.13, 0.06, 0.03, or 0.02 L/sec of water to the saw blade. Using a randomized block design, implemented under laboratory conditions, the aforementioned conditions were evaluated independently on two types of concrete roofing tiles (s-shape and flat) using the same saw and blade. Each engineering control (LEV or water suppression) was replicated eight times, or four times for each type of tile. Analysis of variance was performed by comparing the mean airborne respirable dust concentrations generated during each run and engineering control treatment. The use of water controls and ventilation controls compared with the "no control" treatment resulted in a statistically significant (p < 0.05) reduction of mean respirable dust concentrations generated per tile cut. The percent reduction for respirable dust concentrations was 99% for the water control and 91% for the LEV. Results suggest that water is an effective method for reducing crystalline silica exposures. However, water damage potential, surface discolorations, cleanup, slip hazards, and other requirements may make the use of water problematic in many situations. Concerns with implementing an LEV system to control silica dust exposures include sufficient capture velocity, additional weight of the saw with the LEV system, electricity connections, and cost of air handling unit.

Preparation and characterization of porous composite filter medium by polytetrafluoroethylene foam coating

The high costs of ceramic and Teflon filter media for hot gas cleaning has limited their industrial applications. This paper presents a foam coating technology that can be used to produce an inexpensive and highly efficient filter for industrial applications. A new apparatus was designed and built that coats porous glass mats with liquid-phase polytetrafluoroethylene (PTFE). The machine generates bubbles, enables the formation of uniform micropores less than 45 microm in diameter, and produces a product with air permeability greater than 5.5 cm3/cm2/sec. The resulting filter was found to be thermally stable up to 270 degrees C without any visible distortion and was comparable in dust collection efficiency to other commercial filter media. In addition, its de-dusting efficiency was greater than 85%, which is similar to that of other test filter media.

[Improving the system of methods covering clinical and rentgenologic observation over workers exposed to dust aerosol]

The article deals with analysis of clinical and rentgenologic changes in various pneumoconiosis types over 1960 to 2007 in Novosibirsk region. Findings are that analogous plain film fails to diagnose pulmonary pneumoconiosis. Pneumoconioses associated with "minimal" dust invasions in 10-15% of cases are not revealed by plain films.

Monitoring surface water chemistry near magnesium chloride dust suppressant treated roads in Colorado

Magnesium chloride (MgCl2)-based dust suppression products are commonly used throughout western United States on nonpaved roads for dust suppression and road stabilization by federal, state, and county transportation agencies. The environmental implications of annually applying these products throughout spring and summer months on adjacent stream chemistry are not known. Sixteen streams were monitored biweekly for 1 to 2 yr in two Colorado counties for a suite of water quality variables up and downstream of nonpaved roads treated with MgCl2-based dust suppression products. Eight of 16 streams had significantly higher downstream than upstream concentrations of chloride or magnesium over the entire monitoring period (p<or=0.05). Mean downstream chloride concentrations ranged from 0.17 to 36.2 mg/L and magnesium concentrations ranged from 1.06 to 12.8 mg/L. Several other ions and compounds, including those commonly found in dust suppression products such as sodium, calcium, and sulfate, were also significantly higher downstream at some sites. Downstream electrical conductivity (EC), chloride and magnesium concentrations were positively correlated with road surface area draining water toward the stream and yearly amount of MgCl2 applied (R2=0.75, 0.51 and 0.49, respectively), indicating that road managers can limit the amount of product entering roadside streams by assessing drainage characteristics and application rates in best management practices. Although MgCl2-based dust suppressants did move into some roadside streams, the concentrations detected were below those reported to adversely affect fresh water aquatic organisms, but the ultimate fate of these ions in Colorado waterbodies are not known.

Man-made vitreous fibers in office buildings in the Helsinki area

Several sources of man-made vitreous fibers (MMVFs) may exist in an office environment causing irritation symptoms among occupants. In 258 office buildings, the occurrence and density of settled MMVFs on surfaces were measured by two sampling methods. Altogether, 1113 samples of settled dust were collected from surfaces with plastic bags and gelatine tape and were analyzed with a scanning electron microscope and a stereomicroscope, respectively. Tape samples from 68 buildings were collected from frequently cleaned (n = 162) and seldom cleaned (n = 57) room surfaces in 56 and 29 offices, respectively, and from supply air ducts (n = 24) in 10 offices. MMVFs longer than 20 microm were counted with a stereomicroscope. Irritation symptoms were recorded with a questionnaire. More than 60% of the surface dust and almost 90% of the samples collected from supply air ducts contained MMVFs. The density of MMVFs longer than 20 microm ranged from < 0.1 to 5 fiber cm(- 2). The mean density of the MMVFs was about two times higher on the seldom cleaned surfaces than on the frequently cleaned surfaces. The density was usually under 0.2 MMVF cm(- 2) in surface dust of offices without emission sources of MMVFs. The measurements combined with qualitative analysis of settled dust can help to localize relevant sources of fiber emissions. Altogether, in 40% of the buildings, several occupants had repeated irritation symptoms that were verified by occupational health care personnel.

The effect of debris accumulation on and filter resistance to airflow for four commercially available vacuum cleaners

Mortar removal with right-angle grinders can cause excessive exposure to respirable crystalline silica. To control this dust exposure, vacuum cleaners need to exhaust 2.3 m(3)/min (80 cubic feet per minute) from the grinder's exhaust hood. Maintaining this airflow while collecting as much as 15.9 kg (35 lb) of debris in the vacuum cleaner has been problematic. A laboratory study was conducted to evaluate how mortar debris affects vacuum cleaner airflow and filter pressure loss. Four vacuum cleaners were tested. Two of the vacuum cleaners used vacuum cleaner bags as a prefilter; the other two vacuum cleaners used cyclones to reduce the amount of debris that reaches the filter. Test debris was collected by a masonry restoration contractor during actual mortar removal using a grinder fitted with a hood. The hood is attached to a vacuum cleaner with cyclonic pre-separation. The vacuum cleaner fan curves were obtained experimentally to learn how pressure loss affects vacuum cleaner airflows. Then, 15.9 kg (35 lb) of mortar removal debris was sucked into the vacuum cleaner in 2.27-kg (5-lb) increments. Before and after adding each 2.27-kg (5-lb) increment of debris, vacuum cleaner airflows were measured with a venturi meter, and vacuum cleaner static pressures were measured at the inlet to the vacuum cleaner motor, and before and after each filter. The vacuum cleaners equipped with cyclonic pre-separation were unaffected by the mass of debris collected in the vacuum cleaner and were able to maintain airflows in excess of 1.98 m(3)/min (70 cfm) throughout the testing program. As debris accumulated in the vacuum cleaners that used bags, airflow decreased from 2.3 m(3)/min (80 cfm) to as little as 0.85 m(3)/min (30 cfm). This airflow loss is caused by the increased airflow resistance of the bags that increased from less 0.03 kPa/m(3)/min (0.1 inches of water per cfm) to 16.7 kPa/m(3)/min (1.9 inches of water/cfm). Apparently, vacuum cleaners using bags should be used in applications where adequate dust control can be achieved at airflows less than 0.85 m(3)/min (30 cfm). Vacuum cleaners with cyclonic pre-separators provided superior and cost-effective dust control compared with vacuums with bags when dust loading was high and when more than 30 cfm of airflow is needed for dust control.

Dust control technology usage patterns in the drywall finishing industry

A telephone survey was conducted to quantify drywall finishing industry usage rates of dust control technology, identify barriers to technology adoption, and explore firm owner perception of risk. Industry use of the following technologies was described: wet methods, respiratory protection, pole sanders, ventilated sanders, and low-dust joint compound. A survey instrument composed of both Likert-type scaled items and open-ended items was developed and administered by telephone to the census population of the owners of member firms of trade associations: Finishing Contractors Association and Association of the Wall and Ceiling Industries. Of 857 firms, 264 interviews were completed. Along with descriptive statistics, results were analyzed to examine effects of firm size and union affiliation on responses. Responses to open-ended items were analyzed using content analysis procedures. Firm owners rated the risk of dust to productivity and customer satisfaction as low-moderate. Half rated the dust as having some impact on worker health, with higher impacts indicated by owners of small firms. Among the available control technologies, respiratory protection was used most frequently. Several barriers to implementation of the more effective control technologies were identified. Barriers associated with technology usability, productivity, and cost, as well as misperceptions of risk, should be addressed to improve dust control in the drywall finishing industry.

A new technique for characterizing the efficacy of fugitive dust suppressants

The Portable In-Situ Wind Erosion Laboratory (PI-SWERL) instrument was evaluated for testing the effectiveness of dust suppressants for a range of native and constructed soils. The PM10 (particles with diameter < or = 10 microm) emissions from dust suppressant-treated and untreated soil surfaces were measured periodically over 14 months. No statistically significant differences were found among soil surfaces treated with three dilution mixtures of the dust suppressant. The temporal variation of PM10 emissions from treated and untreated plots for native and constructed soil textures indicated that: (1) reductions of PM10 emissions by the dust suppressant were significant within 2-3 months after the application and diminished substantially thereafter, (2) decomposition of the protective treated layer resulted in high PM10 emissions for longer environmental exposure times, and (3) emissions from untreated soil surfaces declined over time because of the formation of a natural crust. These results demonstrated that the PI-SWERL can provide qualitative and quantitative information on PM10 emissions for a range of soil textures and can be used to estimate the effectiveness of dust suppressants exposed to actual environmental (i.e., weather and solar radiation) conditions over long periods of time.

Characterizing potential water quality impacts from soils treated with dust suppressants

Two separate laboratory experiment series, surface runoff and steady-state seepage, were performed to determine if dust suppressant products can be applied to soils with an expected minimal to no negative impact on water quality. The experiments were designed to mimic arid field conditions and used two soils (clayey and sandy) and six different dust suppressants. The two experiments consisted of: (i) simulated rainfall (intensities of 18, 33, or 61 mm h(-1)) and associated runoff from soil trays at a surface slope of 33%; and (ii) steady-state, constant head seepage through soil columns. Both experiment series involved two product application scenarios and three application ages (i.e., to account for degradation effects) for a total of 126 surface runoff and 80 column experiments. One composite effluent sample was collected from each experiment and analyzed for pH, electrical conductivity, total suspended solids (TSS), total dissolved solids, dissolved oxygen, total organic carbon, nitrate, nitrite, and phosphate. Paired t tests at 1 and 5% levels of significance and project specific data quality objectives are used to compare water quality parameters from treated and untreated soils. Overall, the results from this laboratory scale study suggest that the studied dust suppressants have minimal potential for adverse impacts to selected water quality parameters. The primary impacts were increased TSS for two synthetic products from the surface runoff experiments on both soils. The increase in TSS was not expected based on previous studies and may be attributed to this study's focus on simulating real-world soil agitation/movement at an active construction site subjected to rough grading.

A wood-strand material for wind erosion control: effects on total sediment loss, PM10 vertical flux, and PM10 loss

Fugitive dust from eroding land poses risks to environmental quality and human health, and thus, is regulated nationally based on ambient air quality standards for particulate matter with mean aerodynamic diameter < or = 10 microm (PM10) established in the Clean Air Act. Agricultural straw has been widely used for rainfall-induced erosion control; however, its performance for wind erosion mitigation has been less studied, in part because straw is mobile at moderate wind velocities. A wood-based long-strand material has been developed for rainfall-induced erosion control and has shown operational promise for control of wind-induced erosion and dust emissions from disturbed sites. The purpose of this study was to evaluate the efficacy of both agricultural straw and wood-strand materials in controlling wind erosion and fugitive dust emissions under laboratory conditions. Wind tunnel tests were conducted to compare wood strands of several geometries to agricultural wheat straw and bare soil in terms of total sediment loss, PM10 vertical flux, and PM10 loss. Results indicate that the types of wood strands tested are stable at wind speeds of up to 18 m s(-1), while wheat straw is only stable at speeds of up to 6.5 m s(-1). Wood strands reduced total sediment loss and PM10 emissions by 90% as compared to bare soil across the range of wind speeds tested. Wheat straw did not reduce total sediment loss for the range of speeds tested, but did reduce PM10 emissions by 75% compared to a bare soil at wind speeds of up to 11 m s(-1).

Reducing silica and dust exposures in construction during use of powered concrete-cutting hand tools: efficacy of local exhaust ventilation on hammer drills

Concrete cutting in construction is a major source of exposure to respirable crystalline silica. To reduce exposures, local exhaust ventilation (LEV) may be integrated into the hand tools used in concrete cutting. Volunteers from the New England Laborers Training Center participated in a field study focused on the use of LEV on concrete-cutting hammer drills. A randomized block design field experiment employing four workers measured the efficacy of four hood-vacuum source combinations compared with no LEV in reducing dust and silica exposures. Using four-stage personal cascade impactors (Marple 294) to measure dust exposure, a total of 18 personal samples were collected. Reductions of over 80% in all three biologically relevant size fractions of dust (inhalable, thoracic, and respirable) were obtained by using any combination of hood and vacuum source. This study found that respirable dust concentrations were reduced from 3.77 mg/m(3) to a range of 0.242 to 0.370 mg/m(3); thoracic dust concentrations from 12.5 mg/m(3) to a range of 0.774 to 1.23 mg/m(3); and inhalable dust concentration from 47.2 mg/m(3) to a range of 2.13 to 6.09 mg/m(3). Silica concentrations were reduced from 0.308 mg/m(3) to a range of 0.006 to 0.028 mg/m(3) in the respirable size fraction, from 0.821 mg/m(3) to a range of 0.043 to 0.090 mg/m(3) in the thoracic size fraction, and from 2.71 mg/m(3) to a range of 0.124 to 0.403 mg/m(3) in the inhalable size fraction. Reductions in dust concentrations while using the four LEV systems were not statistically significantly different from each other.