Respirable Dust Measurements Research Articles

In Mine Comparison of Diesel Particulate Sampling Methods

Abstract In an effort to quantify diesel particulate exposures in the mining industry, various organizations have developed diesel particulate sampling instruments. These instruments work on a variety of different principles. These principles include the use of size-selective sampling utilizing inertial impaction, the measurement of respirable combustible dust (RCD), and the measurement of elemental carbon. The RCD methods provide measurements of whole diesel particulate. The size-selective and elemental carbon methods provide a measurement of a fraction of the diesel particulate matter. The size-selective and RCD methods are limited by gravimetric analysis. The elemental carbon method is limited by filter loading. A series of tests were conducted to compare the measurements obtained with the various diesel particulate sampling instruments and analytical methods. The tests were conducted at two underground mining facilities, a zinc mine and a potash mine. Similar tests are scheduled to be conducted in coa...

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.

Level and distribution of employee exposures to total and respirable wood dust in two Canadian sawmills.

Personal respirable (N = 230) and total (N = 237) dust measurements were made in two coastal British Columbia sawmills using a sampling strategy that randomly selected workers from all jobs in the mills over two seasons. Information about job title, department, season, weather conditions, location of the job relative to wood-cutting machines, and control measures also was collected at the time of sampling. Only 16 respirable wood dust samples were above the detection limit of 0.08 mg/m3; all 16 had levels < or = 0.20 mg/m3. Total wood dust concentrations were also low (36% less than the detection limit), with a mean of 0.51 mg/m3, and ranging from < 0.08 to 52 mg/m3. Measurements of exposure taken close to chippers, planers, and multiple saws had the highest total wood dust levels. Sawmill department and booth enclosures also were associated with wood dust concentrations, while local exhaust ventilation and weather conditions were not. Wood dust levels in this study were generally lower than in other studies of this industry, but most sawmill investigations report mean wood dust concentrations lower than those measured in the furniture and cabinetmaking industries, where concerns about wood dust exposures initially were raised.

Exposure-response relationships for coal mine dust and obstructive lung disease following enactment of the Federal Coal Mine Health and Safety Act of 1969.

Underground U.S. coal miners were studied cross-sectionally for the association of respirable coal mine dust exposure with pulmonary function and symptoms of airways obstruction. The study group included 1,185 miners participating in Round 4 of the National Study of Coal Workers' Pneumoconiosis who had started mining in or after 1970 when comprehensive exposure regulations first came into effect. Quantitative estimates of cumulative exposure, derived using respirable dust measurements taken by the Mine Safety and Health Administration over the entire study period, were used in linear and logistic regression models on indicators of pulmonary function and chest symptoms while controlling for smoking status, pack-years, and other potential confounders. Statistically significant associations between log cumulative exposure and decrements in FVC, FEV1, and FEV1/FVC were observed. In logistic models, statistically significant associations of cumulative exposure with increasing prevalence of FEV1 and FEV1/FVC less than 80% predicted and symptoms including chronic phlegm, chronic bronchitis, breathlessness, wheeze, and wheeze with shortness of breath were found. It is concluded that exposures to respirable coal mine dust present in U.S. mines since 1970 continue to affect respiratory health in underground miners.

Calibration of the Hund tyndallometer for measuring environmental tobacco smoke in a test duct

The Hund tyndallometer (Type TM Digital μP) has recently been used to study the air quality in SAS aircraft. This publication contains an evaluation of its performance in measuring environmental tobacco smoke (ETS), comparing its output with the gravimetric method which was used for measuring respirable dust concentration (van der Wal 1988). The influence of several parameters, such as the age of ETS, the type of smoke (main stream or side stream), and the relative humidity was investigated. The Hund measurements of ETS generated by a smoking machine (ISO 7210) in a test duct were calibrated against gravimetric measurements of respirable dust trapped on teflon membrane filters. An accurate calibration was, however, not possible for outputs of less than 1 mV. This is 0.1% of the electrical output range (IV) and corresponds to 100μg/m 3 of respirable dust. For times of up to 7 min and relative humidity (RH) levels between 8 and 72%, the ageing of ETS did not appear to influence the output of the Hund. RH levels in this range also did not clearly influence the instrument response factors. Higher RH levels did, however, affect the response factor, probably due to condsenation of water vapour on the particles. The average response factors for three types of cigarettes were respectively 177, 173, and 138 mg m −3 V −1. The average response factor of the Hund for measurements taken during SAS flights was 131 mg m −3 V −1, with a relative standard deviation of 24%. As some of the measurements did not meet the Hund preconditions (output <1 m V, gravimetric concentration <100 μg m −3), they meet excluded from this evaluation. The Hund tyndallometer can be a useful instrument to collect additional information of real-time peak concentrations under limiting operating conditions.

Correction

FIGURES 4(a) and (b) have been redrawn after correcting a computer programming error. The last sentence on p. 311 of the original article should now read ‘To obtain the respirable concentration according to the proposed definition, respirable concentrations measured according to the BMRC definition would have to mutiplied by a factor between 0.84 and 1.0 for log-normal size distributions for which σg > 2 and for which at least 10% of the ambient aerosol is respirable by the BMRC definition.’ Assertions in the Abstract and Summary that the proposed definition differs approximately equally from the BMRC and ACGIH definitions are not entirely accurate, since for log-normal size distribution having σg > 2 respirable concentrations measured according to the proposed definition would differ less from those measured according to the BMRC definition than from those measured according to the ACGIH definition. Many respirable dust concentrations measured nominally according to the BMRC definition are obtained using cyclone samplers whose collection efficiency curves resemble more those of the ACGIH present and proposed definitions of respirable dust than that of the BMRC definition, so definitive statements about differences between the proposed definition and current practices are difficult. The proposed definition is a compromise which would require current respirable dust measurement practices to be altered slightly to reach international consensus on a single definition. [The corrections do not change the conclusions of the paper.]

Hard-rock mining exposures affect smokers and nonsmokers differently. Results of a community prevalence study.

The physiologic consequences of occupational dust exposure, their relation to smoking, and their reversibility with cessation of exposure remain controversial. To address these questions, we studied a random sample of male residents of Leadville, Colorado when the major employer, a hard-rock mine, had been closed for 5 to 11 months. Subjects were interviewed for respiratory symptoms and occupational history, underwent plethysmographic measurements of lung volume and airflow, and performed a single breath diffusing capacity procedure. Dyspnea was the only respiratory symptom exacerbated by mining exposures. Cumulative dust exposure, estimated with historic respirable dust measurements for mining job titles and weighted by time at the job, was associated with decreases in maximal expiratory flow rates when controlled for smoking, age, and height. However, determinations of plethysmographic lung volume that allowed calculation of flow rates at equivalent absolute lung volume indicated that dust effects differed in never-smokers and smokers. In never-smokers, dust exposure was associated with decreased lung volume, increased flow rates, and increased DLCO/VA. In smokers, dust exposure was associated with increased lung volume, lower flow rates, and lower DLCO/VA than that accounted for by smoking. We suggest that hard-rock mining exposures result in irreversible pulmonary function changes of airflow limitation in smokers and of a restrictive nature in never-smokers.

Modern Real-time Aerosol Samplers

Abstract A number of direct reading aerosol instruments useful for industrial hygiene measurements and research have been developed in the last 15 years, many with government support. These instruments have attempted to address various industrial hygiene problem areas, including making real-time respirable dust measurements, making personal dust exposure measurements, and calibrating personal sampling devices. This discussion covers a review of a selected number of instruments, ranging from simple photometers to a more sophisticated size distribution measurement system. Several laboratory and field applications of these and similar instruments are presented.

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

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

Critique of 1985 ACGIH report on particle size-selective sampling in the workplace.

The criteria recently proposed by ACGIH for judging the acceptability of respirable and other dust fraction samplers are analyzed. Implications on the sampling of workplace aerosol are determined. With the consideration of both bias and imprecision, the overall accuracy limited by the criteria is estimated for the sampling of coal mine dust as characterized by various researchers. The accuracy limits thus found appear to be excessively broad. As an example with actual workplace dust distributions in the sampling of a single aerosol (mass median diameter = 18.6 micrometers and geometric standard deviation = 2.3) with respirable dust concentration near 2 mg/m3, two samplers acceptable according to the proposed criteria could be found giving respirable dust measurements equal to 0.71 mg/m3 and 4.3 mg/m3 (even after excluding 5% of the low and high measurements from each sampler, respectively). Large variation in samplers acceptable according to the criteria is found for many other distributions as well; this indicates that tighter requirements are necessary. Seldom attained are both the single-sample +/- 25% accuracy at the 95% confidence level required of sampling/analytical methods endorsed by the National Institute for Occupational Safety and Health (NIOSH) and the tighter ISO dust fraction measurement requirement that 67% of the measurements of a sampled dust fall within 10% of a true value. Suggestions are given for sharpening the criteria without eliminating all samplers from acceptability.

Evaluating dust exposures in foundries by a screening test.

During the period 1978–1983 industrial hygiene consultants made 2185 ‘personal’ measurements of respirable dust throughout 35 Danish foundries. The mass of dust collected and the crystalline silica content were determined. Four-fold table analysis was used to evaluate the application of an exposure zone screening limit value (EZSLV), based on the gravimetric concentration alone, with the aim of reducing the number of samples requiring costly silica analysis. Factors for consideration were the relationships between EZSLV and the probability of false negatives, the probability of false positives and the predictive values. Various strategies for establishing the EZSLV are discussed. Restriction of silica analysis to samples that exceed the EZSLV reduces the analytical burden by 30% if a probability of 5%of false negatives is acceptable and by 20% if a probability of 1 % of false negatives is acceptable.

Comparison of Mass Concentrations Determined With Personal Respirable Coal Mine Dust Samplers Operating at 1.2 Liters Per Minute and the Casella 113A Gravimetric Sampler (MRE)

Measuring respirable dust concentrations in coal mine environments is currently done using approved personal respirable dust sampling equipment operating at a flow rate of 2.0 liters per minute (Lpm). Measurements made with approved coal mine dust sampling equipment are converted to equivalent concentrations that would be obtained with a Mining Research Establishment (MRE) instrument known as the Casella 113A gravimetric sampler, using a conversion factor of 1.38. NIOSH has recently recommended that coal mine dust samplers (CMDS) used to measure respirable dust levels in mine environments be operated at 1.2 Lpm and measured concentrations be multiplied by 0.91 to obtain an equivalent MRE concentration. The purpose of this recommendation is to reduce systematic error caused by the variation in mine dust distributions. This paper presents and discusses data collected in the laboratory and in underground coal mines to evaluate the recommended 1.2 Lpm flow rate and 0.91 conversion factor. Comparative measurements were obtained in the laboratory with the CMDS operating at 2.0 and 1.2 liters per minute and the MRE, using aerosols of coal and limestone dust of varying particle size distribution. Similar comparative measurements were made in a number of underground coal mines at locations with environments having particle size distributions representative of different underground mining operations. It was concluded from this study that there is no significant change in the variability associated with the constant factor used to convert respirable dust measurements, obtained with approved respirable CMDS, to equivalent MRE measurements when the flow rate of the CMDS is reduced from 2.0 to 1.2 Lpm.

Correlations Between Measurements with RAM-land Gravimetric Samplers on Longwall Shearer Faces

Simultaneous RAM-1 and gravimetric personal sampler respirable dust measurements were made by the Bureau of Mines at two locations adjacent to a moving shearer on longwall faces. These locations were (1) 4.6 to 6.1 m (15 to 20 ft) on the ventilation intake side of the shearer headgate drum and (2) at the shearer midpoint, between the two operators. Despite the fact that the RAM-1 monitors were laboratory-calibrated to give equivalent readings, underground readings were often lower, particularly at the intake side of the shearer. The RAM-gravimetric ratio of all readings was 0.53 at the intake position and 0.75 at the midpoint position for all data. When only head-to-tail cut passes were analyzed, the RAM-gravimetric ratios were 0.53 at the intake position and 1.00 at the midpoint position. The difference between RAM arid gravimetric dust readings is attributed to a combination of factors such as ambient air velocity and cyclone orientation.

An Epidemiologic Study of Respiratory Disease in Workers Exposed to Polyvinylchloride Dust

The respiratory health of workers exposed to polyvinylchloride (PVC) dust has been investigated in 818 selected men from the current and past work force of a factory manufacturing PVC. In a cross-sectional survey, the lung function, prevalence of respiratory symptoms and chest radiographic abnormalities were compared with estimates of individual PVC dust exposures based on detailed occupational histories and current measurements of respirable PVC dust.

Epidemiological study of respiratory disease in workers exposed to polyvinylchloride dust.

The respiratory health of workers exposed to polyvinylchloride (PVC) dust has been investigated in 818 men sampled from the work force of a factory manufacturing PVC. In a cross-sectional survey, the lung function and prevalences of respiratory symptoms and chest radiographic abnormalities were compared with estimates of individual PVC dust exposures based on detailed occupational histories and current measurements of respirable PVC dust. Complaints of slight exertional dyspnoea were associated with PVC dust exposure, though age and smoking effects were much stronger. The forced expired volume in one second (FEV1) and forced vital capacity (FVC) were inversely related to dust exposure after age, height, and smoking effects had been taken into account. This effect was seen principally in cigarette smokers, and there was suggestive evidence that PVC dust exposure and cigarette smoking interacted in the reduction of FEV1 and FVC. Gas transfer factor was not related to dust exposure. The chest radiographs were read according to the ILO U/C classification by three experienced readers. One reader recorded a low prevalence of small rounded opacities, and these were not related to age or dust exposure. Another reader recorded a higher prevalence of small rounded opacities category 0/1 or more, and these were related to age but not to dust exposure. The third reader recorded the highest prevalence of small rounded opacities (though none greater than category 1/1), and these were independently related both to age and to PVC dust exposure, indicating an effect of PVC dust on the appearance of the chest radiography. These appearances were so slight that only the higher sensitivity of this reader in the interpretation of profusion of small rounded opacities on the ILO U/C scale enabled detection of this effect of PVC dust. In conclusion, exposure to PVC dust is associated with some deterioration of lung function, slight abnormalities of the chest radiograph, and complaints of slight dyspnoea. The mean decline in FEV1 associated with the average dust exposure experienced in the study was small, though some of the men with higher dust exposures may have suffered clinically important loss of lung function as a result of their occupation.

A new mass sensor for respirable dust measurement.

A new portable instrument measures mass concentration in the 100 mug/m3 range of airborne dust particles smaller than 10 mum. An electrostatic precipitator desposits particles as small as 0.01 mum onto a piezoelectric micro-balance sensor. The instrument utilizes digital readout and a built-in sensor cleaner.

The validity of gravimetric measurements of respirable coal mine dust.

While the gravimetric method of assessment of coal dust exposures is superior to the microscopic count method in the ease, speed, and precision of the final measurement, there are shortcomings in the validity of sampling and interpretation. Data and experience with the gravimetric method are presented to demonstrate the significance of these shortcomings in relation to the legal requirements and standards for use of this method in coal mines. Errors inherent in the sampling or introduced by inadequately trained technicians using the method can have unwarranted serious import on coal mine operations. The gravimetric method has not been sufficiently correlated against pulmonary response to inhaled dust in this country to validate a standard to be strictly enforced with possibilities of severe penalties.