Assessment of personal direct-reading dust monitors for the measurement of airborne inhalable dust

The performances of five portable direct-reading dust monitors were investigated in a wind tunnel for a range of industrial dusts and three sizes of aluminium oxide test dust to mainly determine their suitability for measuring the inhalable fraction of airborne dust in workplaces. The instruments tested were Split 2 (SKC Ltd), Sidepak (TSI Inc.), Dataram (Thermo Electron Ltd), PDS-2 (Sibata Scientific Technology Ltd) and the Respicon TM (Hund Ltd). The instruments' responses were compared with reference dust samplers. These were the IOM sampler for the inhalable fraction and the Casella cyclone sampler for the respirable fraction. All instruments are predominantly responsive to and are designed to measure particles in the respirable size range, although two of the instruments, the Split 2 and Respicon TM, are claimed to be capable of measuring inhalable-sized particles. For the purpose of the tests, major modifications to an existing wind tunnel dust injection system were made to facilitate the generation of uniform concentrations of large inhalable-sized dust particles at low air velocities. Each monitor greatly underestimated the measurement of inhalable concentration for all the dusts tested, although the linearity was good over a wide range of concentrations for any particular size distribution of dust. However, their calibration factors, defined as the ratio of reference inhalable concentration to monitor concentration, were especially sensitive to changes in particle size as the response of the instruments decreased rapidly with increasing particle size. The monitors generally overestimated the measurement of respirable dust concentration by up to a factor of about 2, apart from the PDS-2, which underestimated it by a factor of up to 3. There was, however, a great deal more scatter in the reference respirable concentration measurements owing to the collection of small dust samples. Therefore, monitor linearity and effects of monitor response to changes in particle size could not be accurately investigated for the respirable fraction. The sampling head of the Split 2 monitor incorporates an IOM inlet and filter to gravimetrically collect the inhalable fraction of airborne dust. This can give a concurrent reference measure of inhalable airborne dust concentration. However, poor sealing within the sampling head resulted in some of the sampled dust not reaching the backup filter. This resulted in the Split 2 underestimating the reference inhalable dust concentration, which meant that it could not be accurately used as a calibration standard. Communications with the manufacturers have since revealed that the sampling head has recently been redesigned in order to improve the seal and eliminate leakage. The Respicon sampler gravimetrically underestimated the inhalable dust concentration, and did so increasingly as the particle size increased.     

A method for establishing tentative occupational exposure limits for inhalable dust

Four-fold classification tables are used on five datasets containing 112 parallel personal measurements of total dust and inhalable dust. The classifications are carried out in such a way that the frequency of non-compliance is equal for total dust and inhalable dust. The results can be used as tentative occupational exposure limits (OELs) for inhalable dust, and the results range from 0.7 to 3.4 of OELs for total dust. The results depend on the industry and the content of the dust.     

Exposure levels and determinants of inhalable dust exposure in bakeries

The study's objectives were to measure full-shift exposure to inhalable dust in bakeries and define the determinants of full-shift exposure. Inhalable dust was measured gravimetrically. Ninety-six bakery workers, employed in seven different bakeries, participated in the study. Two side-by-side full-shift inhalable dust samples were obtained from each study participant on a single occasion. Samples were collected on 18 days selected at random. During the entire sampling period, bakers were observed and information on 14 different tasks was recorded at 15 min intervals. Other production characteristics were also recorded for each sampling day. These task and production variables were used in statistical modelling to identify significant predictors of exposure. The mean full-shift inhalable dust exposure was 8.2 mg/m³ (range: 0.1–110 mg/m³). A regression model explained 79% of the variability in exposure. The model indicated that tasks such as weighing, pouring and operating dough-brakers and reversible sheeters increased the exposure, while packing, catching and decorating decreased the exposure. Bread and bun production lines were associated with increased full-shift inhalable dust exposure, while cake production and substitution of dusting with the use of divider oil were associated with decreased exposure. Production tasks and characteristics are strong predictors of personal full-shift exposures to flour dust among bakers; these can be altered to reduce exposure levels.     

Assessment of bioaerosols and inhalable dust exposure in Swiss sawmills

An assessment of wood workers' exposure to airborne cultivable bacteria, fungi, inhalable endotoxins and inhalable organic dust was performed at 12 sawmills that process mainly coniferous wood species. In each plant, samples were collected at four or five different work sites (debarking, sawing, sorting, planing and sawing cockpit) and the efficiency of sampling devices (impinger or filter) for determining endotoxins levels was evaluated. Results show that fungi are present in very high concentrations (up to 35 000 CFU m(-3)) in all sawmills. We also find that there are more bioaerosols at the sorting work site (mean +/- SD: 7723 +/- 9919 CFU m(-3) for total bacteria, 614 +/- 902 CFU m(-3) for Gram-negative, 19 438 +/- 14 246 CFU m(-3) for fungi, 7.0 +/- 9.0 EU m(-3) for endotoxin and 2.9 +/- 4.8 g m(-3) for dust) than at the sawing station (mean +/- SD: 1938 +/- 2478 CFU m(-3) for total bacteria, 141 +/- 206 CFU m(-3) for Gram-negative, 12 207 +/- 10 008 CFU m(-3) for fungi, 2.1 +/- 1.9 EU m(-3) for endotoxin and 0.75 +/- 0.49 mg m(-3) for dust). At the same time, the species composition and concentration of airborne Gram-negative bacteria were studied. Penicillinium sp. were the predominant fungi, while Bacillus sp. and the Pseudomonadacea family were the predominant Gram-positive and Gram-negative bacteria encountered, respectively.     

Occupational exposure to inhalable wood dust in the member states of the European Union

The aim of this study was to estimate occupational exposure to inhalable wood dust by country, industry, the level of exposure and type of wood dust in 25 member states of the European Union (EU-25) for the purposes of hazard control, exposure surveillance and assessment of health risks. National labour force statistics, a country questionnaire (in 15 member states, EU-15), a company survey (in Finland, France, Germany and Spain), exposure measurements (from Denmark, Finland, France, Germany, The Netherlands and the United Kingdom) and expert judgements were used to generate preliminary estimates of exposure to different types of wood dust. The estimates were generated according to industrial class (six wood industries, four other sectors) and level of exposure (five classes). These estimates were reviewed and finalized by national experts from 15 member states. Crude estimates were generated also for 10 new member states (EU-10). The basic data and final estimates were included in the WOODEX database. In 2000-2003, about 3.6 million workers (2.0% of the employed EU-25 population) were occupationally exposed to inhalable wood dust. Of those, construction employed 1.2 million exposed workers (33%), mostly construction carpenters. The numbers of exposed workers were 700,000 (20%) in the furniture industry, 300,000 (9%) in the manufacture of builders' carpentry, 200,000 (5%) in sawmilling, 150,000 (4%) in forestry and <100,000 in other wood industries. In addition, there were 700,000 exposed workers (20%) in miscellaneous industries employing carpenters, joiners and other woodworkers. The numbers of exposed workers varied by country ranging from <3,000 in Luxembourg and Malta to 700,000 in Germany. The highest exposure levels were estimated to occur in the construction sector and furniture industry. Due to limited exposure data there was considerable uncertainty in the estimates concerning construction woodworkers. About 560,000 workers (16% of the exposed) may be exposed to a level exceeding 5 mg m(-3). Mixed exposure to more than one species of wood and dust from wooden boards was very common, but reliable data on exposure to different species of wood could not be retrieved. This kind of assessment procedure integrating measurement data, company data, country-specific data and expert judgement could also serve as one model for the assessment of other occupational exposures.     

Determinants of inhalable dust exposure in the European carbon black manufacturing industry

A large study to investigate the respiratory health effects of occupational exposure to carbon black in the European carbon black manufacturing industry commenced in 1987. During the study, a large amount of personal occupational exposure data was collected. This article describes the empirical models used to study the determinants of inhalable dust exposure, using data from 16 factories collected in the third and last cross-sectional phase of this study. Information on activities during the measurements was collected using short job category-specific questionnaires. In addition, questionnaires were completed by factory representatives on the implementation of control measures and changes in production process since the first cross-sectional phase. Mixed effects analyses of variance models were used to identify determinants of exposure, while taking into account the within- and between-worker (random) variance components. The results of these models show that, for any job category, factory is a strong predictor of exposure in this industry. These differences could not be explained entirely by factors such as age of the factory or the control measures implemented since the first phase of the study. Surprisingly, implementation of local exhaust ventilation systems had an effect that was counterintuitive; for example, in warehouses where local exhaust ventilation systems had been implemented, higher dust exposure levels were found compared to those where such control measures had not been installed since the first cross-sectional survey. Season appeared to have some effect on exposure for some job titles, with generally relatively low exposures being found in the summer. Finally, a number of activities were identified that caused higher levels of dust exposure, most notably "changing of filters" and "clean-up of carbon black spills."     

Field comparison of two inhalable samplers used in Italy to measure the wood dust exposure

Background: Particle size affects the performance of personal air samplers used to measure dust exposure in the workplace. Few field studies have been conducted for comparing the performance of personal inhalable samplers.

Objective: To compare wood dust sampling with two inhalable samplers: IOM (Institute of Occupational Medicine) and Italian cone.

Methods: 136 Italian cone/IOM paired samples and 136 passive IOM samples were collected in 30 Italian woodworking industries. The valid number of sample pairs was 114. Ultra-large particles were collected by passive IOM. The sampling membranes were weighed and the size particles were measured. Mass differences in active and passive IOM samples were calculated (IOM-Δ).

Results: Statistical analysis of all 114 Italian cone/active IOM paired results showed a significant mass difference (P < 0.05) and no significant mass difference for sanding and cutting woodworking processes. The Italian cone/IOM-Δ paired results consistently showed no statistically significant mass differences in any woodworking processes. Both samplers performed similarly when ultra-large particles mass contribution was not considered.

Conclusions: These findings confirm the presence of ultra-large particles in woodworking. The Italian cone and IOM samplers can be used interchangeably for personal wood dust exposure assessment, when the wood activities produce small-size particles.     

Personal inhalable dust and endotoxin exposure among workers in an integrated textile factory

Abstract

The aim of this study was to determine personal exposure to inhalable dust and endotoxin levels among workers in an integrated cotton-processing textile factory and exposure variability across the different work sections. Full shift measurements were carried out using inhalable conical samplers with 37?mm glass-fiber filters. Personal inhalable dust was determined gravimetrically, and endotoxin levels were analyzed by kinetic chromogenic Limulus Amebocytes Lysate assay. The geometric means of personal dust and endotoxin concentrations were 0.75?mg·m^?3 and 831 EU·m^?3, respectively. The highest dust and endotoxin concentrations were observed in carding section (1.34?mg·m^?3 and 6,381 EU·m^?3, respectively). Altogether, 11% of dust and 89% of endotoxin samples exceeded workplace exposure limits. This study showed a moderate correlation between inhalable dust and endotoxin (r?=?0.450, p?<?0.001). Our findings indicate that low dust exposure does not guarantee a low exposure to endotoxin.     

Field comparison of personal samplers for inhalable dust

The performances of two designs of personal inhalable fraction sampler, which have been shown to differ in laboratory wind tunnel studies, were assessed in 23 real industrial environments, relative to the collection of dust by a simulated worker. This took the form of a mobile, articulated, breathing robot which was fitted with an oral filter, and could be moved around the workplace to follow and mimic real workers. Statistical analysis of the resulting data show that if a small correction for bias is applied there is no significant difference either between the personal samplers as predictors of the 'real' worker exposure, or in the reproducibility obtained with the two personal samplers. The ratio between dust concentrations measured simultaneously on opposite lapels was greater than 2 on more than 5% of occasions, and is believed to be largely due to real concentration gradients in the environments sampled. It would appear that the differences between sampler performances demonstrated in laboratory studies are not significant under conditions encountered in the field.     

Variations in exposure to inhalable wood dust in the Danish furniture industry. Within- and between-worker and factory components estimated from passive dust sampling

Variability of exposure to wood dust at large factories in the Danish furniture industry was studied. Three repeated exposure measurements of 292 workers at 38 factories were included in the study. The measurements were carried out by use of personal passive dust monitors. The components of variance were estimated by means of a random effects ANOVA model. The ratio of within- to between-worker variance was 1.07. Based on this result, and three repeated exposure measurements, the observed relation between health outcome and exposure will be attenuated to 74% of the true value. Grouping by factory showed very poor exposure contrast, as the contrast in exposure level among factories was as low as 0.15.     

Exposure to inhalable flour dust in Canadian flour mills

In 1999, the American Conference of Governmental Industrial Hygienists (ACGIH(R)) proposed a Threshold Limit Value (TLV(R)) of 0.5 mg/m(3) for flour dust with a sensitization notation. The Labour Program of the Department of Human Resources Development Canada (HRDC), following notice of the intention to set a TLV, conducted a study of the levels of exposure to flour dust in flour mills across Canada to verify existing conditions, as well as to decide whether to adopt the proposed TLV or reference some other value. As part of the study, a relationship between flour dust concentrations obtained by using Institute of Occupational Medicine (IOM) samplers and closed-face 37-mm cassettes was examined and the literature on the health effects of exposure to flour dust was reviewed. A total of 104 millers, packers, sweepers, bakery mix operators, and others (mixed tasks) from 14 flour mills were sampled over an 8-hour work shift using IOM samplers. The results indicate that 101 employees (97.1%) were exposed to levels exceeding 0.5 mg/m(3), 66 employees (67.3%) to levels exceeding 5 mg/m(3), and 44 employees (42.3%) to levels exceeding 10 mg/m(3). For comparison purposes, flour dust measurements were also taken in a highly automated flour mill using state-of-the-art technology. The results suggest that even with the most up-to-date technology and proper cleaning operations in place, the flour milling industry may not be able to reduce the flour dust levels to below the TLV of 0.5 mg/m(3). According to the measurements of inhalable and total dust concentrations, the IOM sampler appears to be a more efficient collector of inhalable airborne particles up to 100 microm than the closed-face 37-mm cassette.     

Trends in levels of inhalable dust exposure, exceedance and overexposure in the European carbon black manufacturing industry

In an attempt to investigate the relationship between exposure to carbon black and respiratory morbidity, a study of the complete carbon black manufacturing industry in Western Europe was commissioned. As part of this study, a large number of personal inhalable (n=8015) dust exposure measurements was taken during three phases of data collection between 1987 and 1995. Repeated measurements on the same worker were taken in the last two phases, which enabled the estimation of the within- and between-worker components of variance. Simultaneously, the fixed effects of phase and factory were estimated using mixed-effects analysis of variance. The results show that the personal inhalable dust exposure has reduced significantly since the first phase of the study. In addition, the interaction term between phase and factory was significant in most job categories, confirming that the reduction of exposure was not equal across all factories.When all factories were considered together, the probability that the mean exposure of a randomly selected worker (overexposure) or the probability that the exposure on a randomly selected day for a randomly selected worker (exceedance) was higher than 3.5mg m(-3), was 10% or less for all job categories in the last phase. However, when the factories were considered separately, it appeared that the probability of overexposure or exceedance was in excess of 10% for the job categories 'Fitter/Welder', 'Warehouseman' and 'Site crew' for a number of factories. Therefore, even though exposure levels of inhalable dust have dropped considerably across the whole carbon black manufacturing industry in Western Europe, further reductions in exposure levels are required in these areas to make sure that the probability of overexposure and exceedance falls below a level of 10%.     

Field comparison of inhalable and total dust samplers for assessing airborne dust in swine confinement barns

Inhalable and total dust sampling devices were compared for evaluating airborne dust in swine confinement buildings. Measurements from three swine facilities (n = 77 paired means) were obtained by area sampling using the IOM (Institute of Occupational Medicine, Edinburgh, U.K.) inhalable dust sampler and a 37-mm closed-face total (TCF) dust sampler. The overall geometric mean IOM concentration (1.18 mg/m(3), geometric standard deviation [GSD] = 2.00) was significantly greater (P < 0.05) than the overall geometric mean TCF concentration (1.08 mg/m(3), GSD = 1.98). Regression analysis with IOM and TCF values as independent and dependent variables, respectively, yielded a factor of 0.86 (+/-0.04 95% confidence interval), which can be used to estimate TCF values from the IOM measurements. Additional paired sampling data were obtained to compare the following pairs of dust samplers: (1) IOM sampler and conical inhalable sampler (CIS) (n = 20 paired means), (2) IOM and open-face total (TOF) dust samplers (n = 14), (3) CIS and TCF samplers (n = 19), and (4) TCF and TOF samplers (n = 8). Paired t-tests showed significantly (P < 0.05) higher IOM concentrations than the CIS sampler; no significant difference (P > 0.05) was found for the other three pairs compared. It may be necessary to establish work-specific conversion coefficients to obtain a reasonable estimate of worker exposure to total dust from measurements using other types of dust sampling devices.     

Laboratory and field testing of sampling methods for inhalable and respirable dust

The performance of four sampling devices for inhalable dust and three devices for respirable dust was tested with different kinds of dusts in the laboratory and in the field. The IOM sampler was chosen as the reference method for inhalable dust, and the IOM sampler provided with the porous plastic foam media was used as the reference method for respirable dust. The other tested instruments were the Button sampler, the optical Grimm aerosol monitor, and the Dekati two-stage cascade impactor with cutoff sizes of 10 and 4 mu m. The study confirmed the applicability of the IOM and Button samplers. The new foam product followed the respirable criteria well. However, the foam sampler was unstable for measuring inhalable dust, probably due to its moisture absorption. In addition, high dust loads should be avoided with the foam sampler due to increase in filtering efficiency. The concentrations of inhalable dust measured with the Button sampler, the Grimm monitor, and the impactor sampler were usually close to those measured with the reference sampler. On the other hand, impactor sampling yielded higher respirable dust concentrations than the reference method in the field, which may have been caused by particle bounce; high dust loads should be avoided while using the impactor. The results also showed that the Grimm monitor enables real-time dust concentration determinations that are accurate enough for routine monitoring of occupational exposure and for testing efficiency of control measures in workplaces.     

Determinants of exposure to inhalable particulate, wood dust, resin acids, and monoterpenes in a lumber mill environment.

In a lumber mill in the northern inland region of British Columbia, Canada, we measured inhalable particulate, resin acid, and monoterpene exposures, and estimated wood dust exposures. Potential determinants of exposure were documented concurrently, including weather conditions, tree species, wood conditions, jobs, tasks, equipment used, and certain control measures. Over 220 personal samples were taken for each contaminant. Geometric mean concentrations were 0.98 mg/m3 for inhalable particulate, 0.49 mg/m3 for estimated wood dust, 8.04 micrograms/m3 for total resin acids, and 1.11 mg/m3 for total monoterpenes. Multiple regression models for all contaminants indicated that spruce and pine produced higher exposures than alpine fir or mixed tree species, cleaning up sawdust increased exposures, and personnel enclosure was an effective means of reducing exposures. Sawing wood in the primary breakdown areas of the mill was the main contributor to monoterpene exposures, so exposures were highest for the barker operator, the head rig operator, the canter operator, the board edgers, and a roving utility worker in the sawmill, and lowest in the planer mills (after kiln drying of the lumber) and yard. Cleaning up sawdust, planing kiln-dried lumber, and driving mobile equipment in the yard substantially increased exposures to both inhalable particulate and estimated wood dust. Jobs at the front end of the sawmill where primary breakdown of the logs takes place had lower exposures. Resin acid exposures followed a similar pattern, except that yard driving jobs did not increase exposures.     

Weighing imprecision and handleability of the sampling cassettes of the IOM sampler for inhalable dust

The weight stability of the sampling cassette of the IOM sampler for inhalable dust was tested in several weighing experiments. The results show that the reliability of repeated weighings was good, but the absorption of water vapour was slow and varied considerably among cassette specimen. The exponential time constant for water absorption was approximately 4 days, and 15-20 days were needed to obtain weight stability. With the help of cassette blanks the imprecision in dust weight could be held below 0.05 mg, if the cassettes were allowed one week's storage in the weighing room before weighing, both before and after sampling. The IOM sampling cassettes seem to consist of a few subsets, each with identical relative weight increase in a weighing room. To keep the variability low it is important that both the blanks and the cassettes used for sampling come from the same subset. Experiments indicate that the conducting plastic of the IOM sampling cassette may be replaced with another kind of plastic with similar electrical conductivity, but whose humidity absorption is 30 times lower. A lid, which is weighed with the cassette, was designed so that the potential dust loss from the cassette proper to the commercial transport clip was eliminated. A flow adapter, which simplifies the measurement of the air flow during personal sampling, was designed.     

Identification of agricultural tasks important to cumulative exposures to inhalable and respirable dust in California

Little data exists on the determinants of agricultural dust exposure, particularly in dry climates. Annual exposure indices to inhalable and respirable dust were constructed by exposure estimates for specific tasks, task duration, and task frequency. The estimates of exposure levels were based on actual field measurements and subjective dust exposure ranking. The task duration and frequency data were obtained by questionnaire from 546 farm operators in California. Annual exposure indices were analyzed to determine which tasks were major contributors to chronic dust exposure. The important tasks were identified by comparisons of the cumulative distribution of exposures for all tasks and the cumulative distribution of exposures with one task deleted. Thirteen and 11 tasks were identified to be important to both inhalable and respirable dust exposures, respectively. Tasks identified to be important to agricultural exposure may be ascribed to exposure duration more than to exposure intensity. Information on task-specific exposure is important for developing control strategies in the agricultural workplace.     

Retrospective exposure assessment for respirable and inhalable dust, crystalline silica and arsenic in the former German uranium mines of SAG/SDAG Wismut

OBJECTIVES: Starting shortly after the reunification of Germany and lasting up to the end of the 1990s, an extensive series of retrospective exposure investigations for the East German uranium mining industry was performed in order to provide information about the exposure situation of the miners towards respirable dust, inhalable dust, crystalline silica and heavy metals. It should provide the necessary information for legal compensation of miners with potential industrial diseases as well as for epidemiological research. METHODS: Extensive side-by-side measurements using original historic equipments as well as comprehensive evaluation of the time increments of specific jobs with respect to exposure relevant tasks were performed. After attributing average exposures to the tasks, shift exposures for the jobs could be calculated. RESULTS: By the end a comprehensive job exposure matrix for all underground jobs of the German uranium mining industry was developed for the components mentioned, including arsenic where relevant. In the early days of SAG/SDAG Wismut dust and silica exposures were extremely high with respirable dust up to 20 mg/m(3) and respirable crystalline silica well above 2 mg/m(3) as shift averages. Beginning from about the early 1960s dust control measures started to improve conditions dramatically. CONCLUSIONS: It is absolutely necessary to invest sufficient effort for the estimation of exposure situations of past technological environments. Especially, the situation of early mechanised mining, characterised by low ventilation, dry drilling techniques and generally lacking dust control measures was characterized by extreme shift exposures. It is important to keep these in mind when metal mining exposure in different environments is considered.