Exposure to Wood Dust, Microbial Components, and Terpenes in the Norwegian Sawmill Industry.

Sawmill workers are exposed to wood dust (a well-known carcinogen), microorganisms, endotoxins, resin acids (diterpenes), and vapours containing terpenes, which may cause skin irritation, allergy, and respiratory symptoms including asthma. The health effects of most of these exposures are poorly understood as most studies measure only wood dust. The present study assessed these exposures in the Norwegian sawmill industry, which processes predominantly spruce and pine. Personal exposures of wood dust, resin acids, endotoxin, fungal spores and fragments, mono-, and sesquiterpenes were measured in 10 departments in 11 saw and planer mills. The geometric mean (GM) and geometric standard deviation (GSD) thoracic exposures were: 0.09 mg m-3 dust (GSD 2.6), 3.0 endotoxin units (EU) m-3 (GSD 4.9), 0.4 × 105 fungal spores m-3 (GSD 4.2), 2 × 105 fungal fragments m-3 (GSD 3.2), and 1560 ng m-3 of resin acids (GSD 5.5). The GM (GSD) inhalable exposures were: 0.72 mg m-3 dust (2.6), 17 EU m-3 (4.3), 0.4 × 105 fungal spores m-3 (3.8), and 7508 ng m-3 (4.4) of resin acids. The overall correlation between the thoracic and inhalable exposure was strong for resin acid (rp = 0.84), but moderate for all other components (rp = 0.34-0.64). The GM (GSD) exposure to monoterpenes and sesquiterpenes were 1105 µg m-3 (7.8) and 40 µg m-3 (3.9), respectively. Although mean exposures were relatively low, the variance was large, with exposures regularly exceeding the recommended occupational exposure limits. The exposures to spores and endotoxins were relatively high in the dry timber departments, but exposures to microbial components and mono-and sesquiterpenes were generally highest in areas where green (undried) timber was handled. Dust and resin acid exposure were highest in the dry areas of the sawmills. Low to moderate correlation between components (rp ranging from 0.02 to 0.65) suggests that investigations of exposure-response associations for these components (both individually and combined) are feasible in future epidemiological studies.

Sputum neutrophils are elevated in smelter workers, and systemic neutrophils are associated with rapid decline in FEV1.

OBJECTIVES: In a previous study on smelter workers we, found significant relationship between exposure to dust and accelerated annual decline in forced expiratory volume in 1 s (FEV1). In this cross-sectional study at the end of a follow-up, we aimed to investigate the possible association between annual decline in FEV1 and markers of airways, and systemic inflammation in smelter workers. METHODS: Employees (n=76 (27 current smokers)) who had been part of a longitudinal study (9-13 years) that included spirometry (>6 measurements) and respiratory questionnaires, performed induced sputum, exhaled NO and had blood drawn. Participants with annual decline in FEV1≥45 mL were compared with participants with annual decline <45 mL; also 26 non-exposed controls were included. RESULTS: Compared with non-exposed controls, smelter workers demonstrated a significantly increased percentage of neutrophils (mean (SD)) (57% (17) vs 31% (15)) and matrix metalloproteinases 8 (MMP-8) levels in sputum, and MMP-9, surfactant protein D (SpD) and transforming growth factor ß (TGFb) levels in blood. A significant association in FEV1≥45 mL was found for blood neutrophils when controlling for smoking habits (OR=1.7 (95% CI 1.0 to 2.8), p=0.045). Airway and blood protein markers were not associated with annual decline in FEV1. CONCLUSIONS: All workers displayed airway and systemic inflammation characterised by increased levels of neutrophils and MMP-8 in sputum, and MMP-9, SpD and TGFß in blood compared with non-exposed controls. Blood neutrophils in particular were significantly elevated in those workers with the most rapid decline in lung function. A similar observation was not seen with airway neutrophils. In the present study, we were able to identify systemic but not airway inflammatory markers that can predict increased decline in FEV1 in smelter workers.

Increased Decline in Pulmonary Function Among Employees in Norwegian Smelters Reporting Work-Related Asthma-Like Symptoms.

OBJECTIVE: To investigate associations between work-related asthma-like symptoms (WASTH) and annual pulmonary function decline among employees of 18 Norwegian smelters. METHODS: A 5-year longitudinal study in which WASTH was defined as a combination of dyspnea and wheezing that improved on rest days and vacation. RESULTS: A total of 12,966 spirometry examinations were performed in 3084 employees. Crude annual decline in forced expiratory volume in 1 second (FEV1) (dFEV1) was 32.9 mL/yr (95% confidence interval, 30.5 to 35.3), and crude annual decline in forced vital capacity (FVC) (dFVC) was 40.9 mL/yr (37.8 to 43.9). After adjustment for relevant covariates, employees reporting WASTH showed higher dFEV1 by 16.0 m:/yr (3.4 to 28.6) and higher dFVC by 20.5 mL/yr (6.0 to 35.0) compared with employees not reporting WASTH. CONCLUSION: Work-related asthma-like symptom was associated with greater annual declines in FEV1 and FVC, indicating a restrictive pattern.

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/height(2), per mg/m(3) increase in dust exposure was -2.3 (95% CI -3.8 to -0.79) (mL/m(2))×year(-1). In an employee of average height (1.79 m) and exposure (1.4 mg/m(3)) the estimated contribution to the annual change in FEV1 associated with dust was 10.4 mL/year. The annual change in FEV1/height(2) in current, compared with non-smokers was -1.9 (-7.2 to 3.4) (mL/m(2))×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/m(2))×year(-1) and -49.0 (-80.2 to -17.8) (mL/m(2))×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.

The incidence of work-related asthma-like symptoms and dust exposure in Norwegian smelters.

RATIONALE: The prevalence of respiratory symptoms among employees in smelters is positively associated with dust exposure. OBJECTIVES: To investigate the association between the incidence of work-related asthma-like symptoms (WASTH) and dust exposure. METHODS: All the employees were invited to participate in a 5-year longitudinal study. The outcome of WASTH was defined as the combination of dyspnea and wheezing improving on rest days or vacation in an individual who had no asthma previously. Information about smoking and occupational status was obtained from a questionnaire. A job exposure matrix of total dust was developed. Multivariate data analyses were performed using Cox regression. MEASUREMENTS AND MAIN RESULTS: The total follow-up time of the employees (n = 2,476) was 8,469 years, and the median follow-up time for participants was 4.0 years. During the follow-up, 91 employees developed WASTH, and the corresponding incidence rate for WASTH per 1,000 person-years was 8.9 (7.3-10.9) (95% confidence interval in parentheses). The risk ratio of WASTH increased significantly (P = 0.0001) with dust exposure in the middle and high categories (1.0-2.9 and ≥ 3.0 mg/m(3)). Stratified analyses showed that the effect of current dust exposure varied with both previous exposure (PE) to dust and fumes (P = 0.006) and airflow limitation (AFL) (P = 0.033). The final analyses showed that the risk ratios for WASTH per 1 mg/m(3) increase in current dust exposure were 1.1 (0.93-1.2), 1.4 (1.1-1.8), 1.6 (1.1-2.3), and 1.9 (1.2-3.0) for the categories (PE+/AFL-), (PE-/AFL-), (PE+/AFL+, and (PE-/AFL+). CONCLUSIONS: In conclusion, dust exposure was associated with an increased incidence of WASTH.

The association between symptoms and exposure is stronger in dropouts than in non-dropouts among employees in Norwegian smelters: a five-year follow-up study.

PURPOSE: We have investigated the association between respiratory symptoms and dust exposure among employees in 18 Norwegian smelters using a longitudinal design. METHODS: All employees (N = 3,084) were examined annually for 5 years (12,996 health examinations). At each examination, the subjects reported if they had respiratory symptoms, coded as 1 (yes) or 0 (no), on a respiratory questionnaire. Symptom score was constructed as the sum of symptoms (0-5). Full-time workers in the production line were classified as line operators; subjects never exposed in the production line were regarded as non-exposed. The remaining individuals were classified as non-line operators. A job-exposure matrix regarding dust exposure was also available. Analyses of repeated measurements were performed using generalised linear mixed model with log-link (Poisson regression). Adjustments were made for overdispersion. RESULTS: The mean age at inclusion was 39.0 years, and 89% were men. The median dust exposure in tertiles 1-3 was 0.19, 1.76 and 3.47 mg/m(3). The longitudinal analyses showed that the association between symptoms-score ratio (SSR) and job category was significantly stronger in dropouts compared with non-dropouts (p = 0.01). Among the dropouts, SSR was 1.61 (95% confidence interval: 1.27-2.05) and 1.39 (1.09-1.77) in line operators and non-line operators compared with non-exposed employees, respectively. The corresponding SSR for subjects who completed the study was 1.13 (1.01-1.27) and 1.12 (1.00-1.26), respectively. Similarly, among the dropouts, the SSR between the second and the first tertile was 1.28 (1.05-1.55) and 1.37 (1.13-1.66) between the third tertile and the first tertile. CONCLUSIONS: Line operators had more respiratory symptoms than non-exposed employees. This effect was significantly stronger in dropouts than in those who continued their jobs, indicating that there is a selection of subjects without respiratory symptoms in this industry.

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.

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 (FEV(1)/FVC ratio) <0.7 and (ii) FEV(1)/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 FEV(1)/FVC ratio <0.7 and 1.44 (1.14 to 1.81) for FEV(1)/FVC ratio

Dust exposure assessed by a job exposure matrix is associated with increased annual decline in FEV1: a 5-year prospective study of employees in Norwegian smelters.

RATIONALE: The relationship between dust exposure and annual decline in lung function among employees in the smelting industry is unknown. OBJECTIVES: The aim of the study was to investigate the relationship between annual change in lung function and occupational dust exposure among workers in 15 Norwegian smelters. METHODS: All employees (n = 2,620) were examined annually for 5 years (11,335 health examinations). At each examination spirometry was performed and a respiratory questionnaire was completed. The smelters were grouped as follows: (1) ferrosilicon alloys (FeSi) and silicon metal (Si-metal); and (2) silicon manganese (SiMn), ferromanganese (FeMn), and ferrochromium (FeCr). A job exposure matrix was available on the basis of 2,619 personal dust exposure measurements. The association between lung function expressed as FEV(1) and FVC per squared height (height(2)) and dust exposure was investigated using multivariate linear mixed model analyses. MEASUREMENTS AND MAIN RESULTS: The annual change in FEV(1)/height(2) (deltaFEV(1)) related to dust exposure in the FeSi/Si-metal and SiMn/FeMn/FeCr smelters was -0.42 (95% confidence interval, -0.95 to 0.11) and -1.1 (-2.1 to -0.12) (ml/m(2)) x (mg/m(3))(-1) x year(-1), respectively. The annual decline in FEV(1)/height(2) was 1.6 ml/m(2) (0.15 to 3.1) steeper in smokers than in nonsmokers. The median geometric mean of the time-weighted dust exposure concentration levels of the employees was 2.3 mg/m(3) in the FeSi/Si-metal smelters and 1.6 mg/m(3) in the SiMn/FeMn/FeCr smelters. Among nonsmokers, deltaFEV(1) was -0.86 (-1.6 to -0.10) and -1.1 (-2.5 to 0.25) (ml/m(2)) x (mg/m(3))(-1) x year(-1) in the FeSi/Si-metal and SiMn/FeMn/FeCr smelters, respectively. Thus, for a 1.80 m tall employee the annual decline in FEV(1) associated with average dust exposure was 5.7 ml/year in the SiMn/FeMn/FeCr smelters, and 6.4 ml/year for a nonsmoker in the FeSi/Si-metal smelters. CONCLUSIONS: In all smelters combined, the annual change in FEV(1) was negatively associated with increasing dust exposure. This association was also significant among workers in SiMn/FeMn/FeCr smelters and among nonsmokers in the FeSi/Si-metal smelters.

Prediction of dropout from respiratory symptoms and airflow limitation in a longitudinal respiratory study.

OBJECTIVES: This study investigated the possibility that employees reporting respiratory symptoms were more likely than asymptomatic workers to dropout of a respiratory study carried out in Norwegian smelters. METHODS: The study included 3924 employees in 24 Norwegian smelters. They were examined annually using a respiratory questionnaire and spirometry. The employees who did not meet for the follow-up within 18 months prior to the end of the study were considered dropouts. The data were analyzed using Cox regression for time-dependent covariates. RESULTS: The total and the median follow-up times were 16 997 and 4.9 years, respectively. The overall dropout rate was 44.5 [95% confidence interval (95% CI) 41.5-47.8 per 1000 person-years]. The hazard ratio (HR) for dropout was 1.38 (95% CI 1.15-1.66) for the workers reporting any respiratory symptom compared with the asymptomatic workers. The effect was the strongest among the employees who reported dyspnea, and it was stronger regarding symptoms at the last visit than for the baseline symptoms. Similarly, the hazard ratio for dropout for those with an airflow limitation [forced expiratory volume/forced vital capacity below the 5th percentile of the predicted value] was 1.31 (95% CI 1.01-1.69) when they were compared with employees without any airflow limitation. CONCLUSIONS: Respiratory symptoms and airflow limitation are important predictors of dropout from a longitudinal respiratory study.

Production of silicon metal and alloys is associated with accelerated decline in lung function: a 5-year prospective study among 3924 employees in norwegian smelters.

OBJECTIVES: To investigate the association between decline in lung function and production of alloys in the Norwegian smelting industry. METHODS: All employees (N = 3924) were examined annually for 5 years (16,570 examinations). The employees were classified into three categories: 1) line operators (employed full time in the production line), 2) nonexposed (no exposure last year), and 3) non-line operators (remaining subjects). The outcome variable was expressed as forced expiratory volume in 1 second per squared height (FEV1/height(2)). RESULTS: In the subcohorts of the ferrosilicon/silicon metal and silicon carbide industries, the differences between line operators and nonexposed workers were -2.3 (-4.3 to -0.3) (CI = 95%) and -5.6 (-10.4 to -0.7) mL/(m(2) x year), respectively. CONCLUSION: Line operators in the ferrosilicon/silicon metal and silicon carbide industries had a steeper annual decline in FEV1/height compared with nonexposed workers.