Merete Drevvatne Bugge

Prevalence of airflow limitation among employees in Norwegian smelters: a longitudinal study

Aims To investigate the association between airflow limitation and occupational exposure and to compare a fixed limit with an age adjusted limit for airflow limitation. Methods 3924 employees in 24 Norwegian smelters and related workplaces were investigated annually over 5 years (n=16 570) using spirometry and a respiratory questionnaire on smoking habits and job category. Employees working full time on the production line were classified as line operators; subjects who never worked on the production line were regarded as non-exposed. A job exposure matrix (JEM) was available in most smelters. Airflow limitation was expressed as (i) forced expiratory volume in 1 s/forced vital capacity (FEV1/FVC ratio) <0.7 and (ii) FEV1/FVC ratio less than the lower limit of normal (LLN). Longitudinal analyses on the prevalence of airflow limitation were performed using a generalised linear mixed model. Results The prevalence of airflow limitation was stable during follow-up. The OR of airflow limitation during follow-up was 1.24 (95% CI 1.03 to 1.50) in line operators compared with unexposed subjects for FEV1/FVC ratio <0.7 and 1.44 (1.14 to 1.81) for FEV1/FVC ratio <LLN. A dose–response relationship was also found between prevalence of airflow limitation and dust exposure. The annual decline in FEV1 was −77.5 (SD 99.9) ml/year in subjects with FEV1/FVC ratio <0.7 and −83.8 (114.2) ml/year in subjects with FEV1/FVC ratio <LLN. Conclusion Prevalence of airflow limitation was higher in exposed than non-exposed employees. Both the FEV1/FVC ratio <0.7 and FEV1/FVC ratio <LLN identify subjects with accelerated annual decline in FEV1.

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.

Incidence of airflow limitation among employees in Norwegian smelters

We have investigated the association between the incidence of airflow limitation and occupational exposure. The employees (n = 3,924) were investigated annually during five years (n = 16,570) using spirometry. Exposure was classified using job category and a job exposure matrix. Airflow limitation was expressed using two indices: (i) as forced expiratory volume in one second/force vital capacity (FEV(1) /FVC) <0.7 and (ii) lower limit of normal (LLN). The incidence of airflow limitation was 21.2/1000 years(-1) and 15.1/1000 years(-1) using the fixed limit (0.7) and the LLN criterion, respectively. We found a dose-response relationship between the incidence of airflow limitation and tobacco consumption and with job-category in non-smokers. The associations between airflow limitation and covariates were independent of how airflow limitation was defined. The incidence of airflow limitation defined as FEV(l) /FVC <0.7 yielded higher incidence rates of airflow limitation than LLN. We found a significant association between the incidence of airflow limitation and occupational exposure in non-smokers.

0313 Mortality among norwegian smelter industry workers – a 55 year follow-up

Ambient air pollution is associated with increased incidence and mortality of cardiovascular disease. Time-series studies have shown that a 10 µg/m3 increase in mean 24 hour PM2 concentration increases the relative risk for daily cardiovascular mortality by 0.4% to 1.0%. In recent years, increasing concerns have been levelled at the ultrafine component of PM. Ultrafine particles are formed during combustion of materials, and are therefore abundant in the furnace area of metal smelter plants. In connexion with an ongoing project concerning occupational exposure to fine and ultrafine particles and risk of cardiovascular disease, an update of two large smelter worker cohorts has been performed. Mortality data were received from the Norwegian Causes of Death register for the period 1960–2014. The combined cohort consisted of 19 660 men, with nearly 650 000 person-years of follow-up. Preliminary analyses showed that both total mortality (SMR 1.09, 95% CI 1.07–1.11) and mortality from all cardiovascular diseases (SMR 1.03, 95% CI 1.00–1.06) were significantly increased compared to the Norwegian general male population. Workers with employment in furnace work had total mortality SMR 1.18 (95% CI 1.15–1.21) and cardiovascular mortality SMR 1.09 (95% CI 1.04–1.14). Smelter workers with no furnace work had total mortality SMR 1.01 (95% CI 0.99–1.04) and cardiovascular SMR 0.99 (95% CI 0.95–1.02). The further data analyses are currently in progress.

Fluctuations in heart rate variability of health care workers during four consecutive extended work shifts and recovery during rest and sleep

The aim of this study was to investigate fluctuations in heart rate variability (HRV), which reflect autonomic nervous system (ANS) function and potential psychological and physical strain, among 24 health care workers during work and sleep during four consecutive extended work shifts. Data included 24/36/12 h of HRV measurements, two logbooks, and a questionnaire. A cross-shift/cross-week design was applied. HRV was measured during work, leisure time, and sleep. The HRV data included time-domain [mean RR, SD of normal to normal R-R intervals (SDNN), and root mean square of the successive differences (RMSSD)] and frequency-domain [low frequency (LF)/high frequency (HF) ratio] parameters. HRV parameters revealed significant differences among work, leisure time, and sleep. Mean RR, RMSSD, and SDNN values were lower and the LF/HF ratio was higher on the first versus last day of the work period; however, the differences were most prominent in the morning hours. The results indicate higher levels of cardiovascular stress on the first versus fourth day of the working period, and measurements at night indicate a satisfactory recovery from the extended shifts.

Exposure related mortality from obstructive lung diseases among workers in the Norwegian silicon carbide industry

Objectives An excess mortality from asthma, chronic bronchitis, and emphysema, is previously reported from the silicon carbide (SiC) industry. Our objective was to study mortality from obstructive lung diseases (OLD) with relation to specific exposure factors, using a revised and extended job exposure matrix (JEM). Methods Cumulative exposures to quartz, cristobalite, SiC particles, and SiC fibres were assigned to a cohort of 1687 long-term SiC industry workers, using a detailed JEM. Standardised mortality ratios (SMRs) for underlying causes of death, 1951–2007, were calculated, and Poisson regression analyses of OLD as underlying or contributing cause of death were performed using categorised and log-transformed cumulative exposure variables. Results The SMR of OLD was increased at the highest level of cumulative exposure to all investigated exposure factors. In the internal analyses of OLD as underlying or contributing cause of death, a twofold increased risk was observed at both medium and high level of cumulative exposure to SiC particles, with a significant trend. In a model with log-transformed cumulative exposure variables, SiC particles was the exposure factor with the most stable increased risk estimate when controlled for other exposure factors, among workers with less than 15 years of total employment duration. Cristobalite seemed to be the most important exposure factor among workers with more than 15 years total employment. Conclusions Exposure to SiC and crystalline silica may contribute to OLD development among SiC industry workers in different time windows, and possibly through different mechanisms.