title: Mortality from non-malignant respiratory diseases among workers in the Norwegian silicon carbide industry: associations with dust exposure.
abstract: OBJECTIVE
  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.
  
  
  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.
  
  
  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.
authors.affiliation: Department of Occupational Medicine and Epidemiology, National Institute of Occupational Health, Oslo, Norway. mdb@stami.no
authors.forename: Merete Drevvatne
authors.initials: MD
authors.lastname: Bugge
authors.forename: Solveig
authors.initials: S
authors.lastname: Føreland
authors.forename: Kristina
authors.initials: K
authors.lastname: Kjærheim
authors.forename: Wijnand
authors.initials: W
authors.lastname: Eduard
authors.forename: Jan Ivar
authors.initials: JI
authors.lastname: Martinsen
authors.forename: Helge
authors.initials: H
authors.lastname: Kjuus
mesh_terms: D017554:Carbon Compounds, Inorganic / Q000633:toxicity*; D004391:Dust; D005500:Follow-Up Studies; D006801:Humans; D008171:Lung Diseases / Q000139:chemically induced / Q000401:mortality*; D008297:Male; D009664:Norway / Q000453:epidemiology; D009784:Occupational Diseases / Q000139:chemically induced / Q000401:mortality*; D016273:Occupational Exposure / Q000009:adverse effects*; D012189:Retrospective Studies; D012307:Risk Factors; D017655:Silicon Compounds / Q000633:toxicity*; D012822:Silicon Dioxide / Q000633:toxicity; D013997:Time Factors
chemical_list: D017554:Carbon Compounds, Inorganic; D004391:Dust; D017655:Silicon Compounds; D012822:Silicon Dioxide; C022088:silicon carbide