title: Pooled exposure-response analyses and risk assessment for lung cancer in 10 cohorts of silica-exposed workers: an IARC multicentre study.
abstract: OBJECTIVE
  Silica is one of the most common occupational exposures worldwide. In 1997 the International Agency for Research on Cancer (IARC) classified inhaled crystalline silica as a human carcinogen (group 1), but acknowledged limitations in the epidemiologic data, including inconsistencies across studies and the lack of extensive exposure-response data. We have conducted a pooled exposure-response analysis of 10 silica-exposed cohorts to investigate lung cancer.
  
  
  METHODS
  The pooled cohort included 65,980 workers (44,160 miners, 21,820 nominees), and 1,072 lung cancer deaths (663 miners, 409 nonminers). Follow-up has been extended for five of these cohorts beyond published data. Quantitative exposure estimates by job and calendar time were adopted, modified, or developed to permit common analyses by respirable silica (mg/m3) across cohorts.
  
  
  RESULTS
  The log of cumulative exposure, with a 15-year lag, was a strong predictor of lung cancer (p = 0.0001), with consistency across studies (test for heterogeneity, p = 0.34). Results for the log of cumulative exposure were consistent between underground mines and other facilities. Categorical analyses by quintile of cumulative exposure resulted in a monotonic trend with odds ratios of 1.0. 1.0, 1.3, 1.5, 1.6. Analyses using a spline curve also showed a monotonic increase in risk with increasing exposure. The estimated excess lifetime risk (through age 75) of lung cancer for a worker exposed from age 20 to 65 at 0.1 mg/m3 respirable crystalline silica (the permissible level in many countries) was 1.1-1.7%, above background risks of 3-6%.
  
  
  CONCLUSIONS
  Our results support the decision by the IARC to classify inhaled silica in occupational settings as a carcinogen, and suggest that the current exposure limits in many countries may be inadequate. These data represent the first quantitative exposure-response analysis and risk assessment for silica using data from multiple studies.
authors.affiliation: National Institute for Occupational Safety and Health, Cincinnati, USA. nsteenland@cdc.gov
authors.forename: K
authors.initials: K
authors.lastname: Steenland
authors.forename: A
authors.initials: A
authors.lastname: Mannetje
authors.forename: P
authors.initials: P
authors.lastname: Boffetta
authors.forename: L
authors.initials: L
authors.lastname: Stayner
authors.forename: M
authors.initials: M
authors.lastname: Attfield
authors.forename: J
authors.initials: J
authors.lastname: Chen
authors.forename: M
authors.initials: M
authors.lastname: Dosemeci
authors.forename: N
authors.initials: N
authors.lastname: DeKlerk
authors.forename: E
authors.initials: E
authors.lastname: Hnizdo
authors.forename: R
authors.initials: R
authors.lastname: Koskela
authors.forename: H
authors.initials: H
authors.lastname: Checkoway
mesh_terms: D000395:Air Pollutants, Occupational / Q000009:adverse effects* / Q000592:standards; D002274:Carcinogens, Environmental / Q000009:adverse effects*; D015331:Cohort Studies; D007692:Diatomaceous Earth / Q000009:adverse effects; D005500:Follow-Up Studies; D006046:Gold / Q000009:adverse effects; D006801:Humans; D016014:Linear Models; D008175:Lung Neoplasms / Q000453:epidemiology / Q000209:etiology* / Q000401:mortality; D008452:Maximum Allowable Concentration; D008906:Mining; D009784:Occupational Diseases / Q000453:epidemiology / Q000209:etiology* / Q000401:mortality; D018570:Risk Assessment; D012822:Silicon Dioxide / Q000009:adverse effects* / Q000592:standards; D012829:Silicosis / Q000150:complications
chemical_list: D000395:Air Pollutants, Occupational; D002274:Carcinogens, Environmental; C007886:granite; D007692:Diatomaceous Earth; D006046:Gold; D012822:Silicon Dioxide