Thoracic Dust Research Articles

Working Conditions and Exposure to Dust and Bioaerosols in Sisal Processing Factories in Tanzania

Information was collected on working conditions and personal exposures to dust, bacteria, and fungi in sisal fiber processing factories in Tanzania to identify health hazards and possible needs for preventive measures. Walkthrough surveys were performed in the brushing and decorticating departments of six sisal factories. The number of departments showing adequate scores for ergonomics and work organization, physical working environment, and occupational health items were determined. Personal thoracic dust samples were collected during sisal processing and analyzed for concentration of dust (n = 24) and for fungi and bacteria (n = 32). In both departments, most items considered to be a prerequisite for a good working environment were either missing or inadequate. Ergonomic and physical hazards were observed. Repetitive strenuous tasks, awkward work postures, and high noise levels were found. Visible dust and inadequate ventilation were seen in the brushing departments, and wet floors were observed in the decortication departments. Personal protective equipment was hardly used. The arithmetic mean exposure of sisal processors was 1.2 mg thoracic dust/m3, 43 × 106 bacteria/ m3, and 2.35 × 106 fungal spores/m3. The highest exposure levels were measured in the decortication departments when machines were cleaned of waste. Significant differences were found for mean thoracic dust exposure and bacteria counts between the brushing and decortication departments and the security guards. Within individual departments, there were no significant differences in exposures between the different work tasks. A linear mixed effect model of thoracic dust including department as fixed effect explained 65% of the between-worker variability for thoracic dust exposure. The study shows that workers in sisal processing in Tanzania are exposed to bioaerosols, and suitable control measures should be implemented. More exposure studies are needed in this type of industry.

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/m3 to a range of 0.242 to 0.370 mg/m3; thoracic dust concentrations from 12.5 mg/m3 to a range of 0.774 to 1.23 mg/m3; and inhalable dust concentration from 47.2 mg/m3 to a range of 2.13 to 6.09 mg/m3. Silica concentrations were reduced from 0.308 mg/m3 to a range of 0.006 to 0.028 mg/m3 in the respirable size fraction, from 0.821 mg/m3 to a range of 0.043 to 0.090 mg/m3 in the thoracic size fraction, and from 2.71 mg/m3 to a range of 0.124 to 0.403 mg/m3 in the inhalable size fraction. Reductions in dust concentrations while using the four LEV systems were not statistically significantly different from each other.

A Survey of Size-Fractionated Dust Levels in the U.S. Wood Processing Industry

A survey of size-fractionated dust exposure was carried out in 10 wood processing plants across the United States as part of a 5-year longitudinal respiratory health study. The facilities included a sawmill, plywood assembly plants, secondary wood milling operations, and factories producing finished wood products such as wood furniture and cabinets. Size-fractionated dust exposures were determined using the RespiCon Personal Particle Sampler. There were 2430 valid sets of respirable, thoracic, and inhalable dust samples collected. Overall, geometric mean (geometric standard deviation) exposure levels were found to be 1.44 (2.67), 0.35 (2.65), and 0.18 (2.54) mg/m, for the inhalable, thoracic, and respirable fractions, respectively. Averaged across all samples, the respirable fraction accounted for 16.7% of the inhalable dust mass, whereas the corresponding figure for thoracic fraction as a percentage of the inhalable fraction was 28.7%. Exposures in the furniture manufacturing plants were significantly higher than those in sawmill and plywood assembly plants, wood milling plants, and cabinet manufacturing plants, whereas the sawmill and plywood assembly plants exhibited significantly lower dust levels than the other industry segments. Among work activities, cleaning with compressed air and sanding processes produced the highest size-fractionated dust exposures, whereas forklift drivers demonstrated the lowest respirable and inhalable dust fractions and shipping processes produced the lowest thoracic dust fraction. Other common work activities such as sawing, milling, and clamping exhibited intermediate exposure levels, but there were significant differences in relative ranking of these across the various industry segments. Processing of hardwood and mixed woods generally were associated with higher exposures than were softwood and plywood, although these results were confounded with industry segment also.

Evaluation of Worker Exposure to Airborne Dust in Cotton Ginneries

Airborne dust in cotton ginneries is a nuisance as well as a potential respiratory hazard. The workers in ginneries are subjected to vagaries of airborne dust pollution. Exposure to dust causes cough, cold, fever, breathing difficulties and may even lead to lung disorders if exposed for long term. Dust concentration in mg! m3 of PM 2.5 11m and PM 10 11m was measured at different workstations. Time weighed average (TWA) of airborne dust of PM 2.5 and PM10 was found up to 2.30 and 3.75 mg/m3 respectively in conventional ginneries. In automatic ginneries, workers are exposed to TWA of airborne dust levels of PM 2.5 and PM 10 up to 0.20 and 0.58 mg/m3 , respectively. The workers in all types of ginneries are exposed to dust concentrations above the permissible limits in all workstations. The thoracic dust and respirable dust concentration levels were observed above the permissible limits in all the workstations. Workers employed in automatic ginneries are comparatively less exposed to airborne dust than conventional and semi-automatic ginneries. Workers stationed at press house, pala house and at lint opener are subjected to higher levels of airborne dust.

Field Performance of the RespiConTMfor Size-Selective Sampling of Industrial Wood Processing Dust

The RespiConTMsampler is a multistage virtual impactor that simultaneously collects the ISO/CEN/ACGIH size fractions of inhalable, thoracic, and respirable particulate matter. The field performance of the device for measurement of industrial wood processing dust was evaluated against reference size-selective samplers: the IOM sampler (inhalable dust), the GK 2.69 cyclone (thoracic dust), and the SKC aluminum cyclone (respirable dust). Seventy-one sets of area samples were collected from 10 wood processing plants, with the samplers mounted either in the free-field or on a two-dimensional “bluff body.” The geometric mean (range) dust levels across all plants measured by the reference samplers were: inhalable, 1.35 mg/ m3(0.11–11.06); thoracic, 0.31 mg/m3(0.05–1.38); and respirable, 0.10 mg/m3(0.02–0.54). In comparing the RespiCon with the reference samplers, there was no significant difference between sampling in the free-field versus bluff-body modes. For inhalable dust, there was no significant difference between the RespiCon and the IOM sampler after applying a correction factor of 1.5× to the extrathoracic data obtained from the RespiCon. Without the correction factor, the RespiCon undersample inhalable dust by an average of 23%. For thoracic dust, the RespiCon was shown to oversample the extrathoracic dust fraction resulting in an overall error of 48%. A simple correction based on the inhalable and thoracic dust levels reported by the RespiCon is proposed. For respirable dust, there was a significant difference between the RespiCon and the SKC cyclone, but the data were equivocal due to imprecision in measurement of the low respirable dust concentrations encountered and the likelihood of bias in the reference sampler. Overall, the RespiCon sampler appears to be a suitable size-selective sampling device for industrial wood processing dust, although adjustments should be made to the inhalable and thoracic dust results.

Development of a New Method for Measuring the Protection Provided by Respirators against Dust and Microorganisms

The efficiency of respirators is usually determined by the protection factor, which is the ratio of the particle concentration outside the respirator to that inside the respirator. Most studies on workplace protection factors (WPF) of respirators have focused on the measurement of total mass concentrations, ignoring the effect of particle size. Furthermore, there appear to be no previous studies on protection factors against biological particles. In this study, a prototype personal sampling setup was developed for determining the protection provided by respirators against non-biological and biological particles in the size range of 0.7–10 μm. The range covers respirable and thoracic dust particles as well as most bacterial and fungal spores. The setup is compatible for field use in workplace environments and was optimized by minimizing particle losses in its aerosol transmission system. Theoretical modeling, laboratory tests, and field tests were performed for design optimization. After accounting for aerosol deposition mechanisms due to gravity, inertia, and turbulence affecting aerosol transmission through the straight and bending sections of specialized tubing, the theoretical data showed best agreement with the laboratory and field data for a tube diameter of ½ inch (~1.27 cm) among the three tested diameters. Tubing of this diameter also had the least amount of particle losses, and can be directed either above the ear or above the shoulder of the person whose respiratory protection is being evaluated. In addition, the ability of the setup to measure the WPF when a human subject donned a respirator was demonstrated successfully during soybean unloading. This study suggests that the new setup is a promising tool for future studies on evaluating respiratory protection against airborne dusts and microorganisms in occupational environments.

Optimisation of the SIMPEDS personal sampling cyclone to the ISO sampling convention for thoracic dust

Optimisation of the SIMPEDS personal sampling cyclone to the ISO sampling convention for thoracic dust

Variability of Particle Size-Specific Fractions of Personal Coal Mine Dust Exposures

This study estimated the ratio of the tracheo-bronchial dust fraction to the fraction collected by a respirable dust sampler for a variety of job classifications found in conventional, continuous, and longwall coal mining sections. The ratios could then be applied in epidemiologic studies to existing respirable dust measurements to estimate thoracic mass concentrations for evaluation of the relative importance of the respirable and thoracic dust fractions to obstructive lung disease. Data collected include particle size distributions from four U.S. underground coal mines using eight-stage personal cascade impactors. A total of 180 samples were examined by mine, occupation and occupations grouped by proximity to the mine face, and by mining technology. Several fractions--that collected by the 10-mm nylon cyclone, the American Conference of Governmental Industrial Hygienists respirable and thoracic particulate mass fractions, and the estimated alveolar and tracheo-bronchial deposition fractions--were estimated. These were not significantly different when grouped by occupation, by proximity of work to the mine face, or by the type of mining technology in use. Distributions from one mine varied from the others, perhaps because it used diesel equipment in the haulage ways, which contributed to the fine aerosol fractions. Results suggest that although the tracheo-bronchial dust fraction may contribute to the development of obstructive lung disease, occupation-specific tracheo-bronchial dust fractions are not likely to produce stronger exposure-response estimates than the historically collected respirable dust concentrations.

Proposal for Converting “Total” Dust Limits to Inhalable and Thoracic Dust Limits

Abstract One step in the implementation of new particle size-selective sampling definitions of inhalable, thoracic, and respirable dust that are becoming internationally accepted is the establishment of appropriate limits on the concentrations of airborne dusts. The preferable approach is to analyze toxicological and epidemiological studies that incorporate sufficient particle size information to obtain particle size-selective dust limits directly. In the absence of such information but with sufficient information about the collection efficiency of the current “total” dust sampler and about the range of workplace aerosol size distributions for the material being considered, there is a rational approach to converting current “total” dust limits to approximately equivalent inhalable or thoracic dust limits, which is described briefly. Currently, there is very little information about the collection efficiency of the “total” dust personal sampler that is used most commonly in the United States. Because of this, there is insufficient information to take even the second approach outlined above. However, recommendations can be developed for converting current “total” dust limits to tentative inhalable or thoracic dust limits using guidelines presented here. Side-by-side sampling comparisons are strongly recommended to discover discrepancies. To illustrate this approach, formulas are proposed for converting current “total” dust limits established in the United States to tentative inhalable or thoracic dust limits (inhalable particulate matter [IPM]- and thoracic particulate matter [TPM] - threshold limit values [TLVs]), whichever is appropriate for the material under consideration:

Thoracic Dust Exposures on Longwall and Continuous Mining Sections

Abstract Past data on the prevalence of symptoms of chronic bronchitis and decreases in pulmonary function indicate a potential problem due to deposition of coal mine dust in the bronchial airways. Difficulty with dust control in certain jobs indicates that chronic bronchitis may continue to be a problem. Compliance with the respirable dust standard does not equally limit the thoracic dust exposure of all miners. Coal mine dust size distributions indicate that thoracic dust levels may be as high as five times respirable dust levels in some work areas on continuous mining sections and seven times respirable dust levels in some work areas on longwall mining sections. The largest thoracic dust generating sources are the longwall shearer, shield support advancement, and the continuous miner. The worst case scenario for thoracic dust exposure occurs on bidirectional cutting longwall mining sections where some mine personnel are very likely to work downwind of the shearer and/or support advancement for a signif...