title: Lung cancer incidence among Norwegian silicon carbide industry workers: associations with particulate exposure factors.
abstract: OBJECTIVE
  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.
authors.affiliation: National Institute of Occupational Health, Pb. 8149 Dep, Oslo N-0033, Norway. mdb@stami.no
authors.forename: Merete Drevvatne
authors.initials: MD
authors.lastname: Bugge
authors.forename: Kristina
authors.initials: K
authors.lastname: Kjærheim
authors.forename: Solveig
authors.initials: S
authors.lastname: Føreland
authors.forename: Wijnand
authors.initials: W
authors.lastname: Eduard
authors.forename: Helge
authors.initials: H
authors.lastname: Kjuus
mesh_terms: D017554:Carbon Compounds, Inorganic / Q000009:adverse effects*; D002617:Chemical Industry; D004391:Dust; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008175:Lung Neoplasms / Q000453:epidemiology / Q000209:etiology*; D008297:Male; D015999:Multivariate Analysis; D009664:Norway / Q000453:epidemiology; D009784:Occupational Diseases / Q000453:epidemiology / Q000209:etiology*; D016273:Occupational Exposure / Q000009:adverse effects* / Q000032:analysis; D009790:Occupations; D052638:Particulate Matter / Q000009:adverse effects*; D016012:Poisson Distribution; D012825:Silicon / Q000009:adverse effects*; D017655:Silicon Compounds / Q000009:adverse effects*; D012822:Silicon Dioxide / Q000009:adverse effects*
chemical_list: D017554:Carbon Compounds, Inorganic; D004391:Dust; D052638:Particulate Matter; D017655:Silicon Compounds; D012822:Silicon Dioxide; C022088:silicon carbide; D012825:Silicon