Dust Control Measures Research Articles

Modelling of airborne dust emissions in CNC MDF milling

All dust control measures are necessary to reduce dust exposure in MDF (Medium Density Fibreboard)-milling, because of the high amount and fineness of the dust produced and a potential risk of exposure to formaldehyde or other glue chemicals during the machining of MDF. The most effective way of reducing dust exposure is to reduce the emission of dust at the source. Airborne dust emission was studied and modelled in the milling. In the milling of MDF, airborne dust emission was much higher than in the milling of solid materials. Milling of MDF produced airborne particles with a mass median diameter of 6–7 µm. The most significant factor affecting the amount of dust created from milling was average chip thickness. In order to reduce the amount of dust, milling parameters should be chosen so that the average chip thickness is greater than 0.05 mm. The average chip thickness could be obtained with different milling parameters, for example with different combinations of feed and traverse rates. The same chip thicknesses resulted in around the same percentage fraction of fine dust mass regardless of how the average chip thickness was obtained. The relationship between the percentage fraction of fine dust mass from the removed mass (c%) and the chip thickness (hm) was modelled and presented in the form of c% = 0.194 h m -1. The model developed can be used to estimate the percentage fraction of fine dust mass as a function of chip thickness. The model can be used in optimisation programs for CNC milling machines to minimize the airborne dust generated and to reduce dust exposure.

The Role of Asbestos Fiber Dimensions in the Prevention of Mesothelioma

A recent interpretation of the pathogenetic role of asbestos fiber size in the development of mesothelioma and in the possibility of mesothelioma prevention needs clarification. This point of view is based on a biased interpretation of the literature. Epidemiologic, experimental, and molecular evidence suggests that the arguments for the role of fiber size relative to dose, dose-response effect, and genetic susceptibility are scientifically unsound. Their proponent also states that means available in the past for the implementation of dust-control measures and/or personal protective equipment would not have contributed to reducing the frequency of mesothelioma among exposed subjects, an argument again based on invalid assumptions.

A gaussian-box modeling approach for urban air quality management in a Northern Chinese City—II. pollutant emission abatement

A modeling framework by linking air quality simulation with system optimization was presented in this paper to develop cost-effective urban air quality management strategies in Fengnan district of China. The relation between the total allowable emission and wind speed as well as the relation between the total allowable emission and air-quality-guideline satisfaction were quantified based on the simulation results of the Gaussian-box modeling system. The area-source emission reduction objective in each functional zone of the study city during the heating and non-heating seasons was calculated based on such relations. A linear programming model was then developed to optimize the emission abatement which was subject to a number of dust and SO2 control measures. The economic objective of the air quality management strategy was to minimize the total emission control system cost while the environmental objective can still be satisfied. The environmental objective was reflected by the emission reduction objective of TSP, PM10 and SO2 corresponding to an air-quality-guideline satisfaction percentage of 80%. Consequently, the modeling system comprehensively took into account the information of emission reduction objectives, emission abatement alternatives, emission reduction cost, and related resources constraints. An optimal emission abatement strategy and the related cost were obtained for various pollution control measures. The results would provide sound bases for decision makers in terms of effective urban air quality management and ensuring healthy economic development in the study city.

The Effects of Dust on the Federally Threatened Valley Elderberry Longhorn Beetle

We combined a natural experiment with field surveys and GIS to investigate the effects of dust from recreational trails and access roads on the federally threatened Valley elderberry longhorn beetle ("VELB," Desmocerus californicus dimorphus) and its host plant, elderberry (Sambucus mexicana). Dust is listed in the species recovery plan as a threat to the VELB and unpaved surfaces are common throughout the riparian corridors where the VELB lives, yet the effects of dust on the VELB have been untested. We found that dust deposition varied among sites and was highest within 10 m of trails and roads, but was similar adjacent to dirt and paved surfaces within sites. Elderberry density did not differ with distance from dirt surfaces. Despite similar within-site dust levels, elderberry adjacent to paved surfaces were less stressed than those near dirt ones, possibly because increased runoff from paved surfaces benefited elderberry. Dust deposition across sites was weakly correlated with elderberry stress symptoms (e.g., water stress, dead stems, smaller leaves), indicating that ambient dust (or unmeasured correlates) influenced elderberry. Direct studies of the VELB showed that its distribution was not negatively affected by the proximity to dirt surfaces. Dust from low traffic dirt and paved access roads and trails, therefore, affected VELB presence neither directly nor indirectly through changed elderberry condition. These results suggest that the placement of VELB mitigation, restoration, and conservation areas can proceed independently of access roads if dust and traffic levels do not exceed those in our study site. Furthermore, dust control measures are likely to be unnecessary under such conditions. The potential effects of increased traffic and dust levels are addressed through a literature review.

Construction planning and design: Beyond the infection control risk assessment

ISSUE: Hospital construction and renovation projects have been associated with outbreaks of infection in immunocompromised patients. Successful implementation of dust control measures requires a partnership between infection control (IC), project managers, and contractors throughout the project from the planning and design phase to final clean-up. PROJECT: The hospital and medical center is a 607-bed tertiary-care teaching facility in Detroit, where construction and renovation projects are routine events. The infection control risk assessment (ICRA), incorporated in planning and design phases, identified risks and recommended appropriate infection control precautions. Despite these efforts, IC noted frequent breaches of dust control measures. We identified an opportunity to improve the management of construction-related infection risks associated with a projected 5-year master facility expansion plan by implementing strategies beyond our current ICRA process. An infection control construction permit (ICCP), listing key personnel contact information and a description of dust control methods, was displayed at the entrance of Class III and IV projects. Training of contractors was supported by IC through initiation of a formal orientation program and onsite education. Infection control practitioners surveyed construction projects daily utilizing a standardized checklist. Non-compliance issues were addressed directly with the contractors and project manager, trended on a corrective action log, and communicated to administration as appropriate. An infection control construction planning module was added to the hospital intranet that included the ICRA, ICCP, educational materials, daily checklist, signage, IC contact information, and a link to the IC home page. RESULTS: Communication between IC and construction groups and compliance with dust control measures has improved. Education to improve contractor and employee awareness of health risks associated with construction has contributed to improved project design and containment measures. LESSONS LEARNED: Implementation of the ICCP, daily monitoring, and promotion of the educational module has enhanced the importance of the role of IC during construction and renovation projects throughout the facility. Risk prevention strategies, identified as part of the ICRA process, must be implemented consistently using a multidisciplinary approach to ensure the safety of patients, employees, and visitors.

Comments on “Recent Developments in Low-Level Lead Exposure and Intellectual Impairment in Children”

Comments on “Recent Developments in Low-Level Lead Exposure and Intellectual Impairment in Children”

Prevalence of respiratory symptoms among wheat flour mill workers in Ibadan, Nigeria.

While investigations into occupational health problems of various groups of workers have been conducted in Nigeria, so far, very little attention has been paid to the health status of workers in the grain industry. The prevalence of respiratory symptoms among wheat flour mill workers and control groups in a medium size industrial setting in Nigeria was studied. The study employed a cross-sectional analytical design. Data were collected using structured interviews, work-site observations, and physical examination. Respondents consisted of 91 flour-millers, 30 matched internal controls from the maintenance unit of the same flour mill factory, and 121 matched external controls. Fifty-four percent of the flour-millers reported at least one respiratory symptom compared with 30% of the internal controls (P < 0.05) and 19% of the external controls (P < 0.001). Most symptoms were significantly more prevalent among the flour-millers compared with control subjects, and this trend was more evident amongst non-smokers than ex-smokers. The study concluded that wheat flour mill workers in Nigeria, like grain workers elsewhere, were at an increased risk of developing both pulmonary and non-pulmonary symptoms compared with control subjects. The result has implications for improved dust control measures in the grain industry in Nigeria.

Dust control measures in the construction industry.

Quartz is a human carcinogen and a causative agent of silicosis. Exposure levels often exceed exposure limits in the construction industry. The need for effective control measures is high, but the complex structure of the construction industry, the variability in sources of exposure and the frequent changes of worksite makes it difficult to implement even simple and potentially effective control measures. The aim of this study was to evaluate the impact of control measures for reducing quartz dust exposure and to assess the extent of their use. Full-shift respirable dust measurements (n = 61) and short-term measurements among construction workers were performed and results of a questionnaire study among 1335 construction workers were analysed. Full-shift measurements showed respirable quartz exposure levels up to 63 times the maximum allowable concentration (MAC) value (0.075 mg/m(3)). More than half of the measurements were above the MAC value. Control measures were not very strongly associated with the full-shift exposure estimates, but the short-term measurements showed large reduction factors (>70%) when wet dust suppression or local exhaust ventilation was used. The effectiveness of control measures is potentially high, and a significant part of the construction worker population is indeed using them on a regular basis. Still, both the exposure study and questionnaire survey show that the use of respiratory protection is the most widely used preventive measure in the construction industry. Respiratory protection might not always reduce exposure sufficiently. Only the combined use of more than one control measure can reduce exposures to acceptable levels.

Influence of family income on hospital visits for asthma among Canadian school children

Background: A study was undertaken to investigate the mechanisms by which socioeconomic status may influence asthma morbidity in Canada. Methods: A total of 2968 schoolchildren aged 5–19 years with reported...

Partnering Makes the Owens Lake Project Feasible

Partnering Makes the Owens Lake Project FeasibleThe Los Angeles Department of Water and Power (LADWP) is currently engaged in remediation of the nation's largest dust (PM10) emissions source: Owens Dry Lakebed. In July 1998, LADWP signed a memorandum of agreement (MOA) with the Great Basin Unified Air Pollution Control District (District) to implement dust control measures at the lakebed. Recognizing the challenging aspects of the Owens Lake...Author(s)M. MadisonR. ColesR. HarasickT. SchadeJ. NelsonG. HilleSourceProceedings of the Water Environment FederationSubjectSession 57 - International and Local Issues: Creative FinancingDocument typeConference PaperPublisherWater Environment FederationPrint publication date Jan, 2002ISSN1938-6478SICI1938-6478(20020101)2002:12L.525;1-DOI10.2175/193864702784164019Volume / Issue2002 / 12Content sourceWEFTECFirst / last page(s)525 - 525Copyright2002Word count119

Evaluation of instruments for dust monitoring in United Kingdom coal mines

The United Kingdom Respirable Dust Regulations for underground coal mines are currently under review; new regulations that are under development will introduce new dust measurement methods and monitoring strategies.Research was undertaken to evaluate instruments for the monitoring of dust and quartz in United Kingdom coal mines and to determine current levels of personal dust exposure in the industry. The aim of the research was to identify instruments capable of being deployed more flexibly in a range of mine workings. The CIP10 respirable dust sampler, developed by CHERCHAR, was identified as a suitable instrument for both personal and fixed-point measurements of respirable dust and quartz. In fixed-point measurements the CIP10 results were highly correlated with colocated results obtained with the MRE 113a horizontal elutriator—the instrument stipulated in the current United Kingdom regulations. As the CIP10 is small, light and has a long battery life, it can be used for full-shift personal dust monitoring in both large and small mines.Personal respirable dust exposures measured during an underground survey that formed part of the research were lognormally distributed with a median value of 1.8 mg/m3 and a geometric standard deviation of approximately two. There was limited evidence of higher mean exposures for certain mine-workers. In general, personal exposure measurements did not differ greatly from fixed-point measurements. The introduction of personal monitoring in United Kingdom coal mines will, however, enable the most highly exposed individual mine-workers to be identified and dust control measures to be directed in a cost-effective manner. Personal monitoring was found to be particularly useful in the assessment of localized dust concentrations in smaller mines and in the development areas of larger mines, where representative fixed-point sampling can be problematic.

Dermatitis in a particleboard manufacturing facility.

Exposure to wood dust and other chemicals used in particleboard manufacture may cause contact dermatitis. To assess the prevalence and nature of skin complaints in the refining and drying department of a particleboard manufacturing facility following introduction of a new process, workers were assessed by a physician, using a standardized questionnaire concerning symptoms, past and family history, workplace exposures, and use of protective equipment. Cutaneous examination and patch testing were then performed. Questionnaire results showed that workers complained of rash, nasal and eye irritation, as well as cough and bothersome odours. Cutaneous examination identified a heterogeneity of skin problems, with dermatitis being mainly irritant rather than allergic. Quaternium-15 (Dowicil 200) was the only allergen to which more than 1 individual reacted. Aside from the odours, exposure to wood dust could account for the other reported symptoms. Allergic reactions on patch testing were few and did not explain the dermatitis; most skin reactions were irritant. Recommendations to the company included improved dust control, through ventilation and personal hygiene measures, as well as protective clothing. The investigation highlights how the introduction of a new process may focus attention on health complaints that have been present for some time before.

A CASE STUDY IN ENVIRONMENTAL CONFLICT RESOLUTION BETWEEN THE COMMUNITY AND THE RAND LEASES MINE TAILINGS DUMP

Community complaints about the negative impact of dust fall-out from a nearby mine tailings dump led residents of Meadowlands, a suburb of Soweto, to join in a monitoring network together with NACA, scientific institutions,NGO's and the mining company involved.&#x0D; Both indoor and outdoor samples showed high fall-out rates. A community-driven initiative to resolve the conflict with the mininghouse concerned led to public involvement and a subsequent commitment by the mining house to implement and maintain dust control measures. Monitoring will continue to measure the success of these measures.

The past and present of pneumoconioses.

Pneumoconioses are still a common cause of chronic lung disease. In industrialized countries, improvements in working conditions and dust control measures have led to a decrease in the incidence of severe forms of silicosis, coal worker pneumoconiosis, and parenchymal asbestosis. However, the diversity of settings in which silica and asbestos are used fuels a continued input of cases, and the burden of cases related to remote exposures is still considerable. Overall, the clinical picture of the classic pneumoconioses and their complications has not changed substantially. However, their limits and links have expanded toward systemic and connective tissue disease, idiopathic pulmonary fibrosis, and antineutrophil cytoplasmic autoantibody-positive vasculitides. Immunologically mediated occupational lung diseases have emerged, such as berylliosis and hard-metal disease. Advances in imaging, mineralogic analysis of bronchoalveolar lavage fluid, and immunologic techniques have been instrumental in describing new patterns of disease and are helpful in litigious or difficult cases.

Effect of Interventions on Children's Blood Lead Levels

Trail, Canada, has been the site of an active lead/zinc smelter for nearly a century. Since 1991, the Trail Community Lead Task Force has carried out blood lead screening, case management, education programs targeted at early childhood groups and the general community, community dust abatement, exposure pathways studies, and remedial trials. From 1989 through 1996, average blood lead levels of children tested for the first time declined at an average rate of 0.6 microg/dl/year, while blood lead levels in Canadian children not living near point sources appeared to be leveling off following the phase-out of leaded gasoline. Since there was no concurrent improvement in local environmental conditions during this time, it is possible that the continuing decline in Trail blood lead levels has been at least partly due to community-wide intervention programs. One year follow-up of children whose families received in-home educational visits, as well as assistance with home-based dust control measures, found that these specific interventions produced average blood lead changes of +0.5- -4.0 microg/dl, with statistically significant declines in 3 years out of 5. Education and dust control, particularly actions targeted toward higher risk children, appear to have served as effective and appropriate interim remedial measures while major source control measures have been implemented at the smelter site.

Radiographic and spirometric findings in diatomaceous earth workers.

Diatomaceous earth is a noncrystalline form of silica; in processing, calcining leads to formation of cristobalite, a form of crystalline silica. Four hundred ninety-two currently employed diatomaceous earth workers in a large mine and processing facility had chest radiographs performed and interpreted by the International Labour Office (ILO) system. Two hundred sixty-seven subjects underwent spirometry testing. Exposure indices for total dust (largely diatomaceous earth) and cristobalite were reconstructed for each individual based upon personnel records. Analysis demonstrated the following prevalences of radiographic findings: 5% had ILO scores > or = 1/0, and 25% had scores of 0/1 or higher. Regression analyses showed that there was a relationship between both total cristobalite exposure and total dust (largely diatomaceous earth) exposure and the ILO score. Radiographic patterns are not typical of those of classic silicosis. Linear regression analyses for forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), and FEV1/FVC ratio did not demonstrate a relationship between cumulative exposure and lung function. Such analyses were performed using all subjects and stratified by smoking status. There were differences in spirometric data according to radiographic ILO category, but the results were inconsistent and did not permit determining if physiologic changes are associated with radiographic change or if this is due to confounding. Overall, the study suggests that diatomaceous earth pneumoconiosis (radiographically defined) is an entity distinct from silicosis. Recent exposure levels may produce radiographic abnormalities but do not lead to demonstrable physiologic effect. The prevalence of the disorder has diminished markedly in response to modern dust control measures. Ongoing medical surveillance is recommended in workers with potential exposure to significant quantity of material.

Further Thorium Lung Burden Data on Mineral Sands Workers

The thorium lung burdens of 19 workers in the mineral sands industry of Western Australia were measured using in vivo gamma counting. The thorium lung burdens ranged from 11 Bq to 181 Bq with a geometric mean of 42 Bq (GSD = 2.2). Measurements of the amount of exhaled thoron in breath were conducted on 145 workers using a double filter tube method. The activity of 224Ra freely emanating 220Rn at the mouth ranged from the minimum detection limit of 0.4 Bq to 3.6 Bq. A comparison of the data for workers who had undertaken both in vivo lung counting and breath measurements yielded a mean thoron exhalation rate of 3.7 ± 1.2%. The estimated geometric mean thorium lung burden of the workers from the thoron-in-breath tests was 10 Bq (GSD=2.2), corresponding to a geometric mean employment period of 9.0 y (GSD=2.0). The lung burdens from the exhaled thoron data were compared with the predicted lung burdens for each worker, as estimated from the total inhaled activity from personal air sampling records and a retrospective assessment. The average ratio of measured to predicted values was about a factor of two higher than predicted which suggests that a review of parameters used in the internal dose assessment protocol may be necessary. The discrepancy could be due to the accuracy of the inhaled activity, the validity of the metabolic data (e.g. pulmonary deposition fraction, biological clearance half-life), the particle size of dust, or the mode and rate of breathing. A dose assessment of the 64 workers above the minimum detection limit using the ICRP 66 lung model predicts a geometric mean value of 16 mSv.y-1 for the annual committed effective dose from intake of thorium ore dust over an employment period of 11.5 y. Seventeen per cent of the workers were estimated to have an average annual internal dose in excess of 20 mSv over the duration of their employment in the industry. Most of the inhaled radioactivity was attributed to early years of employment since extensive dust control measures have been implemented in recent years.

A cohort study of graphite workers in Sri Lanka.

A cohort of workers from a graphite mine in Sri Lanka was studied in 1987, 1990 and 1993. Radiographic lesions were found in 8.5%, 8.9% and 4.1% of the workers in these respective rounds. When workers with radiographic lesions were clinically examined, a total of 18 cases of graphite pneumoconiosis and seven cases of active pulmonary tuberculosis were detected in the three rounds. The prevalence of both these diseases showed a decline in 1993 when compared to 1987. This favourable situation was probably the result of dust control measures introduced in the mine after 1972. Five workers developed graphite pneumoconiosis in the course of the study. They had worked in the mine for an average of 22.6 years. The right lung appeared to be more vulnerable than the left.

Dust conditions of stope sections in zones of "force action" on K12 coal seams

In order to increase the daily loading per stope, accelerate preliminary workings, and create safe conditions for conducting mining operations on the floor of the Saranskaya mine of the Karagandaugol` Production Association, wells were drilled from the surface for hydraulic fracturing ({open_quotes}disjointing{close_quotes}) of the series of coal seams K{sub 7}, K{sub 10}, K{sub 11}, and K{sub 12}. The indexes of the {open_quotes}force actions{close_quotes} on the coal seams are listed, and data on the takeoff of methane from the wells drilled into the seams are presented. As the object of investigation of dust conditions in certain worked sections, the characteristics of which are shown in seam K{sub 12} was selected, which is high-gas and blowout-hazardous, and is classed in groups 4-6 with respect to dust level. The K{sub 12} seam consists of 20 bands of coal interlayered with argillites with a thickness of 0.2-2.5 cm, with inclusion of pyrite interlayers with the coal. The seam was worked by regular longwalls along the strike. The dust control measures that are being implemented in the stopes of the mine consist of wetting the coal in place and the use of a typical watering system mounted on the combines.

Preventing asthma epidemics due to soybeans by dust-control measures.

The inhalation of soybean dust released during the unloading of soybeans into a silo caused outbreaks of asthma in Barcelona, Spain. This study was designed to determine morbidity due to asthma and serum IgE reactivity before and after the installation of filters in the silo. We measured soybean-allergen concentrations in 136 samples of air collected for 9 months before and 24 months after the installation of filters. We compared the number of days on which there was an unexpected increase in emergency room visits for asthma, the number of days on which the number of emergency room visits for asthma in one four-hour period was so high that it was unlikely to be due to chance, and the mean daily number of emergency room and intensive care unit admissions for asthma for a total of 60 months before and after filter installation. Serum IgE antibodies against soybean allergens were measured in 38 patients before and after filter installation. The concentration of airborne soybean allergens on days when soybeans were unloaded decreased from 324 to 25 U per cubic meter after the installation of filters (P < 0.001). The number of days on which there was an unusually large number of visits to the hospital for asthma and the number of days on which asthma was epidemic both decreased significantly (both P < 0.001), from 29 to 6 and from 18 to 0, respectively. The mean daily number of emergency room and intensive care unit admissions for asthma on days when soybeans were unloaded decreased from 8.3 to 5.4 and from 0.26 to 0.01, respectively (both P < 0.001). The mean serum IgE antibody concentrations in the 38 patients studied decreased from 2 Pharmacia reference units per milliliter to 1 (P < 0.001). Installing filters on silos to prevent airborne dissemination of allergenic soybean dust eliminates outbreaks of asthma caused by inhalation of the dust, thus supporting the idea that the avoidance of allergens helps prevent asthma.