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Abstract

Objectives
To assess the hazard of tool vibrations, we need valid exposure measurements. The use of hand-attached accelerometers (vibration sensors) to measure hand-arm vibrations (HAVs) has become a popular approach. However, according to International Standard ISO 5349-2, the preferred attachment of accelerometers is at the tool handle. We compared measures of HAV between hand- and tool-attached accelerometers in rock drilling.


Methods
We measured HAV in five rock drillers using jackleg drills in normal working operations with simultaneous measures of both hand-attached and tool-attached accelerometers. Five to seven measurement cycles of 15 s were executed on each worker, resulting in a total of 29 measurement cycles. To identify possible differences in working technique, we recorded videos of tool handle handgrips during drilling.


Results
There was a significant difference (9.5 m s−2; P ≤ 0.05) in vibration magnitudes measured by the tool-attached accelerometers compared with the hand-attached accelerometers. The hand-attached accelerometer showed a lower vibration magnitude for all workers (range of difference: 2.3–14.6). The variation between the two accelerometer attachments was larger between workers than within workers (ICC = 0.68).


Conclusions
For measurements of HAV from jackleg drills, the use of hand-attached accelerometers may cause a lower recorded vibration level compared with tool-attached accelerometers. This difference is likely to vary depending on how workers grip the tool handle, and a misclassification of exposure will occur if workers grip the tool handle in a way that makes the accelerometer lose contact with the vibrating surface. Individual differences in how workers grip the tool handles should be considered when assessing HAV.

Abstract

Objectives
In the cement production industry, exposure to airborne particulate matter is associated with a decline in lung function and increased airway symptoms. Exposure to clinker—the major constituent of cement and supposedly the cause of the observed adverse health effects—was determined recently in 15 cement production plants located in 8 different countries (Estonia, Greece, Italy, Norway, Sweden, Switzerland, Spain, Turkey). It was shown that the median clinker abundance in the thoracic fraction varied between approximately 20% and 70% for individual plants. The present study complements the previous work by investigating the significance of job function as a determinant of clinker exposure.


Methods
The elemental composition (water and acid-soluble fractions separately) of 1,227 personal thoracic workplace samples was analyzed by positive matrix factorization (PMF) to determine the contribution of different sources to the composition of airborne particulate matter and to quantify the clinker content.


Results
Median thoracic mass air concentrations varied for individual job functions between 0.094 and 12 mg/m3 (estimated separately for different plants). The PMF 5-factor solution yielded median relative clinker abundances in the personal thoracic samples between 7.6% and 81% for individual job functions. Thoracic clinker air concentrations are highest for cleaning, production, and maintenance work, and lowest for administration and other work. Foremen and laboratory personnel show intermediate exposure levels. The plant was found to have a much higher contribution to the total variance of the thoracic clinker air concentrations than the job function. Thoracic clinker air concentrations (medians between 0.01 and 5.5 mg/m3) are strongly correlated with the thoracic mass air concentrations and to a lesser extent with the relative clinker abundance in an aerosol sample.


Conclusions
Job function is an important predictor of exposure to clinker in the cement production industry. As clinker is suspected to be the causal agent for the observed adverse health effects among cement production workers, the clinker air concentration may be a better exposure metric than thoracic air mass concentration despite the strong correlation between the two. Reduction strategies should focus on the most exposed job categories cleaning, production, and maintenance work.

Abstract

Objectives
To estimate the composition and exposure to clinker and other specific components in personal thoracic dust samples of cement production workers.


Methods
A procedure for the classification of airborne particles in cement production plants was developed based on classification trees. For this purpose, the chemical compositions of 27,217 particles in 29 material samples (clinker, limestone, gypsum, clay, quartz, bauxite, iron source, coal fly ash, and coal) were determined automatically by scanning electron microscopy (SEM) and energy-dispersive X-ray microanalysis (EDX). The concentrations of the major elements in cement (calcium, aluminium, silicon, iron, and sulphur) were used for the classifications. The split criteria of the classification trees obtained in the material samples were used to classify 44,176 particles in 34 personal thoracic aerosol samples. The contents of clinker and other materials were estimated, and the clinker contents were analysed statistically for differences between job types and job tasks.


Results
Between 64% and 88% of the particles from material samples were classified as actual materials. The material types with variable composition (clay, coal fly ash, and coal) were classified with the lowest consistency (64% to 67%), while materials with a more limited compositional variation (clinker, gypsum, and quartz) were classified more consistently (76% to 85%). The arithmetic mean (AM) of the clinker content in personal samples was 62.1%, the median was 55.3%, and 95% confidence interval (CI) was 42.6% to 68.1%. No significant differences were observed between job types. However, the clinker content in samples when workers handled materials with high clinker content was significantly higher than when materials with lower clinker content were handled, 85% versus 65% (P = 0.02). The limestone content was AM 14.8%, median 13.2% (95% CI 5.5 to 20.9), whereas the other materials were present with relative abundances of median ≤ 6.4%.


Discussion
Automated particle analysis by SEM-EDX followed by classification tree analysis quantified clinker with fairly high consistency when evaluated together with raw materials that are expected to be airborne in cement production plants. The clinker proportions for job types were similar. Tasks a priori ranked by assumed clinker content were significantly different and according to expectations, which supports the validity of the chosen methodology.


Conclusions
The composition of personal samples of mineral aerosols in the cement production industry could be estimated by automated single particle analysis with SEM-EDX and classification by a classification tree procedure. Clinker was the major component in the thoracic aerosol that cement production workers were exposed to. Differences between job types were relatively small and not significant. The clinker content from tasks was in agreement with assumptions.

Published version, source at http://doi.org/10.1016/j.jaad.2016.03.033 . License CC BY-NC-ND 4.0 . ; Background The age-adjusted incidence of cutaneous squamous cell carcinoma (cSCC) in the Nordic countries has increased during the last 60 years, and the identification of occupational variation in the relative risk of cSCC may have preventive implications. Objective We sought to describe variation in the relative risk of cSCC between occupational categories in Finland, Iceland, Norway, and Sweden. Methods This is a historical prospective cohort study based on record linkages between census data for 12.9 million people and cancer registry data from 1961 to 2005. Standardized incidence ratios for cSCC were estimated for 53 occupational categories with the cSCC incidence rates for the national population of each country used as reference. Results During follow-up, 87,619 incident cases of cSCC were reported to the national cancer registries. In all countries combined, significant increased standardized incidence ratios were observed among seamen, military personnel, public safety workers, technical workers, teachers, transport workers, physicians, dentists, nurses, other health workers, religious workers, clerical workers, administrators, and sale agents (standardized incidence ratios between 1.08 and 1.77). Limitations Information on occupation was based on 1 point in time only. Conclusion The occupational variation of the relative risk of cSCC might be associated with socioeconomic factors, and to some extent to occupational exposures.

Abstract

Objectives
This study aimed to assess the exposure to a selection of aerosols and gases in the work environment for workers performing tunnel construction using tunnel boring machines (TBMs), to identify determinants of exposure based on the information available and to calculate robust estimates of exposure using a statistical model. The focus was particulate matter (PM) and respirable crystalline silica (RCS). In addition, concentrations of nitrogen dioxide (NO2), elemental carbon (EC), and oil mist were assessed.


Methods
Personal sampling was conducted from February 2017 to February 2019. PM in the thoracic and the respirable aerosol fractions was collected, and RCS was determined in the respirable aerosol fraction. Context information was collected on questionnaires. Because the workers could participate in the sampling more than once and multiple measurements were performed on the same date a mixed model was used in the analysis. Concentrations of PM and RCS are presented as estimated and measured geometric means (GMest and GMmea) and estimated arithmetic mean (AMest) in addition to the median. Measured concentrations of NO2, EC, and oil mist are presented as geometric means.


Results
A total of 290 and 289 personal samples of PM in the thoracic and respirable aerosol fractions were available for analysis, respectively. Work title/work location, type of work (production, maintenance, or a combination of the two), and date of sampling were identified as determinants of exposure. Workers in the front of the TBMs had the highest exposure to PM and RCS. The GMest of RCS exposure varied from 35 to 413 μg m–3 depending on the work title. The geometric standard deviations for measured RCS concentrations by work title ranged from 1.6 to 3.5. A total of 16 samples of NO2 and EC and 12 samples of oil mist were collected. Maximum values of NO2 and EC were 54 µg m–3 and 23 µg m–3, respectively. The maximum measured value of oil mist was 0.08 mg m–3.


Conclusions
All TBM workers were exposed to PM and RCS. Exposure to RCS may be substantial, and workers in front of the TBM were exposed to the highest concentrations of both PM and RCS. A day-to-day variation was found, probably caused by differences in drilling activities. Preventive measures are warranted to keep the exposure to PM and consequently the exposure to RCS as low as possible to protect the health of workers in tunnel construction.

Abstract
The use of tunnel boring machines (TBMs) for tunnel excavation is expected to increase in the coming years. Workers near and on the TBM are exposed to fine mineral particles, including α-quartz. The particle size distribution has implications on health effects, monitoring and control strategies as well as accurate α-quartz quantification. The aim of our study was to investigate and characterize the particle size distribution of particulate matter including α-quartz associated with tunnel excavation by TBMs in an area dominated by metamorphic rocks (e.g., gneiss).
Sioutas cascade impactors were used to collect personal samples (n=14) on three separate days. The impactor fractionates the dust in five size fractions, from 10 µm down to below 0.25 µm. The filters were weighted, and the α-quartz concentrations was measured by X-ray diffraction (XRD) analysis using the NIOSH 7500 method. Scanning electron microscopy (SEM) was used to determine size and elemental composition of individual particles.
Most of the particulate mass was found on the first three impactor stages (0.5-10 µm. There were no observable differences in the size distribution for the three sampling days and for the various work tasks. However, the α-quartz proportion varied for the three sampling days indicating a dependency on petrology. The size distribution of the calculated respirable α-quartz fraction was different from the calibration material, which most likely affects the accuracy of the measured α-quartz air concentrations. Knowledge of the particle size distribution is important for dust control actions since they should reduce the respirable α-quartz fraction.

Abstract

Objectives
Cement belongs to the most used building materials. Clinker is the major constituent of cement, and it is believed that the strong increase of pH after hydration of clinker minerals is responsible for the observed decline in lung function of cement production workers. Information on clinker exposure at workplaces in the cement production industry is scarse. The aims of this study are to determine the chemical composition of thoracic dust and to quantify workplace exposure to clinker in cement production.


Methods
The elemental composition of 1250 personal thoracic samples collected at workplaces in 15 plants located in 8 different countries (Estonia, Greece, Italy, Norway, Sweden, Switzerland, Spain, Turkey) was determined by inductively coupled plasma optical emission spectrometry (ICP-OES), separately for water- and acid-soluble fraction. Positive matrix factorization (PMF) was used to determine the contribution of different sources to the dust composition and to quantify the clinker content in 1227 of the thoracic samples. In addition, 107 material samples were analysed to facilitate interpretation of the factors obtained by PMF.


Results
The median thoracic mass concentrations varied for individual plants between 0.28 and 3.5 mg/m3. PMF with 8 water-soluble and 10 insoluble (i.e., acid-soluble) element concentrations yielded a five-factor solution: Ca, K, Na sulfates; silicates; insoluble clinker; soluble clinker-rich; and soluble Ca-rich. The clinker content of the samples was calculated as sum of the insoluble clinker and soluble clinker-rich factors. The median clinker fraction of all samples was 45% (range 0–95%), and varied between 20% and 70% for individual plants.


Discussion
The 5-factor solution of PMF was selected on the basis of several mathematical parameters recommended in the literature as well as the mineralogical interpretability of the factors. In addition, interpretation of the factors was supported by the measured apparent solubility of Al, K, Si, Fe, and to a lesser extent Ca in material samples. The total clinker content obtained in the present study is considerably lower than estimates based on the Ca concentrations in a sample, and somewhat lower than estimates based on Si concentrations after selective leaching with a methanol/maleic acid mixture. The clinker abundance in workplace dust of one plant investigated in the present contribution was also estimated in a recent study by electron microscopy, and the good agreement between both studies gives confidence in the results of PMF.


Conclusions
The clinker fraction in personal thoracic samples could be quantified from the chemical composition by positive matrix factorization. Our results allow for further epidemiological analyses of health effects in the cement production industry. As these estimates are more accurate for clinker exposure than aerosol mass, stronger associations with respiratory effects are expected if clinker is the main cause of these effects.

Abstract
Tunnel boring machines (TBMs) are used to excavate tunnels in a manner where the rock is constantly penetrated with rotating cutter heads. Fine particles of the rock minerals are thereby generated. Workers on and in the vicinity of the TBM are exposed to particulate matter (PM) consisting of bedrock minerals including α-quartz. Exposure to respirable α-quartz remains a concern because of the respiratory diseases associated with this exposure. The particle size distribution of PM and α-quartz is of special importance because of its influence on adverse health effects, monitoring and control strategies as well as accurate quantification of α-quartz concentrations. The major aim of our study was therefore to investigate the particle size distribution of airborne PM and α-quartz generated during tunnel excavation using TBMs in an area dominated by gneiss, a metamorphic type of rock. Sioutas cascade impactors were used to collect personal samples on 3 separate days. The impactor fractionates the dust in 5 size fractions, from 10 µm down to below 0.25 µm. The filters were weighted, and the α-quartz concentrations were quantified using X-ray diffraction (XRD) analysis and the NIOSH 7500 method on the 5 size fractions. Other minerals were determined using Rietveld refinement XRD analysis. The size and elemental composition of individual particles were investigated by scanning electron microscopy. The majority of PM mass was collected on the first 3 stages (aerodynamic diameter = 10 to 0.5 µm) of the Sioutas cascade impactor. No observable differences were found for the size distribution of the collected PM and α-quartz for the 3 sampling days nor the various work tasks. However, the α-quartz proportion varied for the 3 sampling days demonstrating a dependence on geology. The collected α-quartz consisted of more particles with sizes below 1 µm than the calibration material, which most likely affected the accuracy of the measured respirable α-quartz concentrations. This potential systematic error is important to keep in mind when analyzing α-quartz from occupational samples. Knowledge of the particle size distribution is also important for control measures, which should target particle sizes that efficiently capture the respirable α-quartz concentration.