Solveig Føreland

Exposure to Fibres, Crystalline Silica, Silicon Carbide and Sulphur Dioxide in the Norwegian Silicon Carbide Industry

Objectives: The aim of this study was to assess personal exposure to fibres, crystalline silica, silicon carbide (SiC) and sulphur dioxide in the Norwegian SiC industry. Methods: Approximately 720 fibre samples, 720 respirable dust samples and 1400 total dust samples were collected from randomly chosen workers from the furnace, processing and maintenance departments in all three Norwegian SiC plants. The respirable dust samples were analysed for quartz, cristobalite and non-fibrous SiC content. Approximately 240 sulphur dioxide samples were collected from workers in the furnace department. Results: The sorting operators from all plants, control room and cleaning operators in Plant A and charger, charger/mix and payloader operators in Plant C had a geometric mean (GM) of fibre exposure above the Norwegian occupational exposure limit (OEL) (0.1 fibre cm−3). The cleaner operators in Plant A had the highest GM exposure to respirable quartz (20 μg m−3). The charger/mix operators in Plant C had the highest GM exposure to respirable cristobalite (38 μg m−3) and the refinery crusher operators in Plant A had the highest GM exposure to non-fibrous SiC (0.65 mg m−3). Exposure to the crystalline silica and non-fibrous SiC was generally low and between 0.4 and 2.1% of the measurements exceeded the OELs. The cleaner operators in Plant A had the highest GM exposure to respirable dust (1.3 mg m−3) and total dust (21 mg m−3). GM exposures for respirable dust above the Norwegian SiC industry-specific OEL of 0.5 mg m−3 were also found for refinery crusher operators in all plants and mix, charger, charger/mix and sorting operators in Plant C. Only 4% of the total dust measurements exceeded the OEL for nuisance dust of (10 mg m−3). Exposure to sulphur dioxide was generally low. However, peaks in the range of 10–100 p.p.m. were observed for control room and crane operators in Plants A and B and for charger and charger/mix operators in Plant C. Conclusion: Workers in the SiC industry are exposed to a mixture of several agents including SiC fibres, quartz, cristobalite, non-fibrous SiC and sulphur dioxide. Exposure levels were generally below the current Norwegian OELs; however, high exposure to fibres and respirable dust still occurs in the furnace department.

Lung cancer incidence among Norwegian silicon carbide industry workers: associations with particulate exposure factors.

Objectives An increased lung cancer risk associated with total dust exposure in the silicon carbide (SiC) industry has previously been reported. The aim of the present study was to examine the relative importance of specific exposure factors by using a comprehensive, historic job exposure matrix based on about 8000 measurements. Methods Cumulative exposure to total and respirable dust, respirable quartz, cristobalite, and SiC particles and SiC fibres was assessed for 1687 long-term workers employed during 1913–2003 in the Norwegian SiC industry. Standardised incidence ratios for lung cancer, with follow-up during 1953–2008, were calculated stratified by cumulative exposure categories. Poisson regression analyses were performed using both categorised and log-transformed cumulative exposure variables. Results The lung cancer incidence was about twofold increased at the highest level of exposure to each of the exposure factors (standardised incidence ratios 1.9–2.3 for all agents). Internal analyses showed associations between exposure level and lung cancer incidence for all investigated factors, but a significant trend only for total dust and cristobalite. In multivariate analyses, cristobalite showed the most consistent associations, followed by SiC fibres. Conclusions The results indicated that crystalline silica in the form of cristobalite was the most important occupational exposure factor responsible for lung cancer excess in the Norwegian SiC industry. SiC fibres seemed to have an additional effect.

Dust exposure is associated with increased lung function loss among workers in the Norwegian silicon carbide industry

Objectives To investigate the relationship between dust exposure and annual change in lung function among employees in Norwegian silicon carbide (SiC) plants using a quantitative job exposure matrix (JEM) regarding total dust. Methods All employees, 20–55 years of age by inclusion (n=456), were examined annually for up to 5 years (1499 examinations). Spirometry was performed at each examination, and a questionnaire encompassing questions of respiratory symptoms, smoking status, job and smoking history, and present job held was completed. A JEM was constructed based on 1970 personal total dust exposure measurements collected during the study period. The association between lung function and total dust exposure was investigated using linear mixed models. Results The annual change in forced expiratory volume (FEV) in one second per squared height, FEV1/height2, per mg/m3 increase in dust exposure was −2.3 (95% CI −3.8 to −0.79) (mL/m2)×year−1. In an employee of average height (1.79 m) and exposure (1.4 mg/m3) the estimated contribution to the annual change in FEV1 associated with dust was 10.4 mL/year. The annual change in FEV1/height2 in current, compared with non-smokers was −1.9 (−7.2 to 3.4) (mL/m2)×year−1. The estimated overall annual decline in FEV1 among current and non-smokers in the highest exposed group was −91.2 (−124.3 to −58.1) (mL/m2)×year−1 and −49.0 (−80.2 to −17.8) (mL/m2)×year−1, respectively. Conclusions Dust exposure, expressed by a quantitative JEM, was found to be associated with an increased yearly decline in FEV1 in employees of Norwegian SiC plants.

Mortality from non-malignant respiratory diseases among workers in the Norwegian silicon carbide industry: associations with dust exposure

Objectives Increased mortality from asthma, chronic bronchitis and emphysema has previously been reported among workers in the silicon carbide (SiC) industry. The objective of the present study was to evaluate the influence of specific exposure factors on mortality from obstructive lung diseases (OLD), using a newly revised job-exposure matrix. Materials and methods 1687 long-term workers employed in 1913–2003 in the Norwegian SiC industry were characterised with respect to cumulative exposure to quartz, cristobalite, SiC particles and SiC fibres. Standardised mortality ratios (SMRs) for underlying causes of death, 1951–2007, were calculated stratified by category of cumulative exposure, and Poisson regression analyses of OLD were performed using cumulative exposure variables. Results An increased total mortality (SMR 1.1, 95% CI 1.0 to 1.2) and increased mortality from cancer, non-malignant respiratory diseases and external factors, were observed. The SMR of OLD was increased at the highest level of cumulative exposure to all investigated exposure factors. In the internal analyses, a twofold increased risk of OLD was observed with increasing levels of cumulative exposure to SiC particles. In a multivariate model, SiC particles showed the most stable increased risk estimate when controlled for other exposure factors, among workers with less than 15 years of employment. Among workers with more than 15 years of employment, crystalline silica, primarily cristobalite, seemed to be the most important exposure factor. Conclusion Exposure to SiC and crystalline silica may contribute to OLD development among SiC industry workers in different time windows, and possibly through different mechanisms.

Quantitative Determination of Airborne Respirable Non-Fibrous α-Silicon Carbide by X-ray Powder Diffractometry

OBJECTIVES The purpose of the present investigation was to establish a method for the determination of airborne respirable non-fibrous silicon carbide (SiC). The main application is within the industrial production of SiC. METHODS Due to the complex airborne aerosol mixture of crystalline compounds in the SiC industry, X-ray powder diffractometry was selected as the most appropriate method. Without any international standard material for the respirable fraction of non-fibrous SiC, pure and suitable products from three SiC plants in Norway were selected. These products have a median particle diameter in the range 4.4-5.1 mum. The method is based on thin sample technique, with the dust deposited on a polycarbonate filter. Absorption correction is done by standard procedures with the use of a silver filter, situated below the polycarbonate filter. RESULTS The diffraction line used for quantitative determination was selected carefully. This was done to avoid interferences from quartz, cristobalite, and graphite, which all are airborne components present in the atmosphere during the industrial process. The instrumental limit of detection for the method is 12 microg. CONCLUSIONS This method has been used to determine airborne non-fibrous SiC in a comprehensive ongoing project in the Norwegian SiC industry for further epidemiological studies. The method is fully applicable for compliance work.

Characterisation of Exposure to Ultrafine Particles from Surgical Smoke by Use of a Fast Mobility Particle Sizer

INTRODUCTION Electrosurgery is a method based on a high frequency current used to cut tissue and coagulate small blood vessels during surgery. Surgical smoke is generated due to the heat created by electrosurgery. The carcinogenic potential of this smoke was assumed already in the 1980s and there has been a growing interest in the potential adverse health effects of exposure to the particles in surgical smoke. Surgical smoke is known to contain ultrafine particles (UFPs) but the knowledge about the exposure to UFPs produced by electrosurgery is however sparse. The aims of the study were therefore to characterise the exposure to UFPs in surgical smoke during different types of surgical procedures and on different job groups in the operating room, and to characterise the particle size distribution. METHODS Personal exposure measurements were performed on main surgeon, assistant surgeon, surgical nurse, and anaesthetic nurse during five different surgical procedures [nephrectomy, breast reduction surgery, abdominoplasty, hip replacement surgery, and transurethral resection of the prostate (TURP)]. The measurements were performed with a Fast Mobility Particle Sizer (FMPS) to assess the exposure to UPFs and to characterize the particle size distribution. Possible predictors of exposure were investigated using Linear Mixed Effect Models. RESULTS The exposure to UFPs was highest during abdominoplasty arithmetic mean (AM) 3900 particles cm(-3) and lowest during hip replacement surgeries AM 400 particles cm(-3). The different job groups had similar exposure during the same types of surgical procedures. The use of electrosurgery resulted in short term high peak exposure (highest maximum peak value 272 000 particles cm(-3)) to mainly UFPs. The size distribution of particles varied between the different types of surgical procedures, where nephrectomy, hip replacement surgery, and TURP produced UFPs with a dominating mode of 9nm while breast reduction surgery and abdominoplasty produced UFPs with a dominating mode of 70 and 81nm, respectively. Type of surgery was the strongest predictor of exposure. When only including breast reduction surgery in the analysis, the use of one or two ES pencils during surgery was a significant predictor of exposure. When only including hip replacement surgery, the operating room was a significant predictor of exposure. CONCLUSION The use of electrosurgery resulted in short-term high peak exposures to mainly UFPs in surgical smoke. Type of surgery was the strongest predictor of exposure and the different types of surgical procedures produced different sized particles. The job groups had similar exposure. Compared to other occupational exposures to UFPs involving hot processes, the personal exposure levels for UFPs were low during the use of electrosurgery.

Personal exposure to ultrafine particles from PVC welding and concrete work during tunnel rehabilitation

Objectives To investigate the exposure to number concentration of ultrafine particles and the size distribution in the breathing zone of workers during rehabilitation of a subsea tunnel. Methods Personal exposure was measured using a TSI 3091 Fast Mobility Particle Sizer (FMPS), measuring the number concentration of submicrometre particles (including ultrafine particles) and the particle size distribution in the size range 5.6–560 nm. The measurements were performed in the breathing zone of the operators by the use of a conductive silicone tubing. Working tasks studied were operation of the slipforming machine, operations related to finishing the verge, and welding the PVC membrane. In addition, background levels were measured. Results Arithmetic mean values of ultrafine particles were in the range 6.26×105–3.34×106. Vertical PVC welding gave the highest exposure. Horizontal welding was the work task with the highest maximum peak exposure, 8.1×107 particles/cm3. Background concentrations of 4.0×104–3.1×105 were found in the tunnel. The mobility diameter at peak particle concentration varied between 10.8 nm during horizontal PVC welding and during breaks and 60.4 nm while finishing the verge. Conclusions PVC welding in a vertical position resulted in very high exposure of the worker to ultrafine particles compared to other types of work tasks. In evaluations of worker exposure to ultrafine particles, it seems important to distinguish between personal samples taken in the breathing zone of the worker and more stationary work area measurements. There is a need for a portable particle-sizing instrument for measurements of ultrafine particles in working environments.

Determinants of Exposure to Dust and Dust Constituents in the Norwegian Silicon Carbide Industry

INTRODUCTION The aim of this study was to identify important determinants of dust exposure in the Norwegian silicon carbide (SiC) industry and to suggest possible control measures. METHODS Exposure to total dust, respirable dust, quartz, cristobalite, SiC, and fiber was assessed in three Norwegian SiC plants together with information on potential determinants of exposure. Mixed-effect models were constructed with natural log-transformed exposure as the dependent variable. RESULTS The exposure assessment resulted in about 700 measurements of each of the sampled agents. Geometric mean (GM) exposure for total dust, respirable dust, fibers, and SiC for all workers was 1.6mg m(-3) [geometric standard deviation (GSD) = 3.2], 0.30mg m(-3) (GSD = 2.5), 0.033 fibers cm(-3) (GSD = 5.2), and 0.069mg m(-3) (GSD = 3.1), respectively. Due to a large portion of quartz and cristobalite measurements below the limit of detection in the processing and maintenance departments (>58%), GM for all workers was not calculated. Work in the furnace department was associated with the highest exposure to fibers, quartz, and cristobalite, while work in the processing department was associated with the highest total dust, respirable dust, and SiC exposure. Job group was a strong determinant of exposure for all agents, explaining 43-82% of the between-worker variance. Determinants associated with increased exposure in the furnace department were location of the sorting area inside the furnace hall, cleaning tasks, building and filling furnaces, and manual sorting. Filling and changing pallet boxes were important tasks related to increased exposure to total dust, respirable dust, and SiC in the processing department. For maintenance workers, increased exposure to fibers was associated with maintenance work in the furnace department and increased exposure to SiC was related to maintenance work in the processing department. CONCLUSION Job group was a strong determinant of exposure for all agents. Several tasks were associated with increased exposure, indicating possibilities for exposure control measures. Recommendations for exposure reduction based on this study are (i) to separate the sorting area from the furnace hall, (ii) minimize manual work on furnaces and in the sorting process, (iii) use remote controlled sanders/grinders with ventilated cabins, (iv) use closed systems for filling pallet boxes, and (v) improve cleaning procedures by using methods that minimize dust generation.

Predictors of Respiratory Protective Equipment Use in the Norwegian Smelter Industry: The Role of the Theory of Planned Behavior, Safety Climate, and Work Experience in Understanding Protective Behavior

Previous research has revealed a higher prevalence of respiratory symptoms in Norwegian smelter workers compared to average population controls. Nevertheless, respiratory protective equipment (RPE) is not always used, even in situations with high exposure risk. A questionnaire was distributed to workers in the Norwegian smelting industry to investigate the relationship between psychological factors and self-reported use of RPEs. Response rate was 567/1,253. A scale measuring attitudes toward behavior (ATT), subjective norms (SN), perceived behavioral control (PBC), and behavioral intention (BI) was constructed based on the Theory of Planned Behavior (TPB). Reliability and Confirmatory Factor Analyses partially supported the theoretical structure of the TPB-based scale, the Work Experience Measurement Scale (WEMS) and the Short Scale for Safety Climate (SC). A model explaining the relationship between observed variables, latent constructs from TPB, WEMS and SC was developed by SEM-analysis. Significant influence on BI from ATT (β = 0.31 p < 0.01), SN (β = 0.36 p < 0.01), and SC (β = 0.19, p < 0.01) emerged. Among the observed variables included, relationship status (β = −0.12 p < 0.05), education level (β = 0.09, p < 0.05), previously completed respirator fit-testing (β = −0.09, p < 0.05) and average hours spent in exposed areas (β = −0.09) p < 0.05) had significant influence on behavioral intention. The model explained 48% of the variance in BI. BI and PBC significantly predicted PB, with β = 0.65 and β = −0.06, respectively. Results of this investigation can help facilitate further work and development of health & safety routines within industrial settings.

Multi-element analysis of airborne particulate matter from different work tasks during subsea tunnel rehabilitation work

ABSTRACT Tunnel rehabilitation work involves exposure to various air contaminants, including airborne particulate matter (APM). Little is known on the contents of different chemical components of APM generated during tunnel work. The objective of the present study was to characterize exposure to APM and various elements for different job categories in different size fractions of APM during a subsea tunnel rehabilitation project carried out in Western Norway. Personal as well as stationary samples of inhalable, thoracic and respirable dust were collected from workers divided into 11 different job categories based on work operations performed, and air concentrations of a range of elements were determined using high-resolution inductively coupled plasma-mass spectrometry (HR-ICP-MS). Overall, APM concentrations were low, but with some measurements exceeding the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV) for inhalable particles, and considerable proportions of respirable and especially inhalable APM exceeding 10% of the TLVs. For most elements, air concentrations measured were quite low, in the ng/m3 range, except for the major crustal elements Si, Fe, Al, and Mg, which were found to be in the µg/m3 range. Asphalt millers overall had the highest exposure levels for APM and most measured elements; for instance, mean concentrations of V, Rb, and Mn were 380, 210, and 2000 ng/m3 in inhalable and 33, 44, and 310 ng/m3 in respirable APM. Mounting PVC membrane seemed to generate elevated levels of Cr, Zn, Sn, Pb, Sb, As, Mn, Fe, and Ni, whereas typical bedrock elements were elevated during drilling activities compared to the low exposed categories lead car drivers, foremen/surveyors, drivers of heavy-duty vehicles, and electricians. Overall, stationary samples contained lower amounts of dust and elemental constituents compared to personal samples. Elemental air concentrations were highly variable with occasional elevated values for APM and certain elements, particularly Cr and Zn.