title: Exposure-response relationships for select cancer and non-cancer health outcomes in a cohort of U.S. firefighters from San Francisco, Chicago and Philadelphia (1950-2009).
abstract: OBJECTIVE
  To examine exposure-response relationships between surrogates of firefighting exposure and select outcomes among previously studied US career firefighters.
  
  
  METHODS
  Eight cancer and four non-cancer outcomes were examined using conditional logistic regression. Incidence density sampling was used to match each case to 200 controls on attained age. Days accrued in firefighting assignments (exposed-days), run totals (fire-runs) and run times (fire-hours) were used as exposure surrogates. HRs comparing 75th and 25th centiles of lagged cumulative exposures were calculated using loglinear, linear, log-quadratic, power and restricted cubic spline general relative risk models. Piecewise constant models were used to examine risk differences by time since exposure, age at exposure and calendar period.
  
  
  RESULTS
  Among 19,309 male firefighters eligible for the study, there were 1333 cancer deaths and 2609 cancer incidence cases. Significant positive associations between fire-hours and lung cancer mortality and incidence were evident. A similar relation between leukaemia mortality and fire-runs was also found. The lung cancer associations were nearly linear in cumulative exposure, while the association with leukaemia mortality was attenuated at higher exposure levels and greater for recent exposures. Significant negative associations were evident for the exposure surrogates and colorectal and prostate cancers, suggesting a healthy worker survivor effect possibly enhanced by medical screening.
  
  
  CONCLUSIONS
  Lung cancer and leukaemia mortality risks were modestly increasing with firefighter exposures. These findings add to evidence of a causal association between firefighting and cancer. Nevertheless, small effects merit cautious interpretation. We plan to continue to follow the occurrence of disease and injury in this cohort.
authors: Division of Surveillance, Hazard Evaluations, and Field Studies, National Institute for Occupational Safety and Health, Cincinnati, Ohio, USA.
authors: Robert D
authors: RD
authors: Daniels
authors: Division of Surveillance, Hazard Evaluations, and Field Studies, National Institute for Occupational Safety and Health, Cincinnati, Ohio, USA.
authors: Stephen
authors: S
authors: Bertke
authors: Division of Surveillance, Hazard Evaluations, and Field Studies, National Institute for Occupational Safety and Health, Cincinnati, Ohio, USA.
authors: Matthew M
authors: MM
authors: Dahm
authors: Division of Surveillance, Hazard Evaluations, and Field Studies, National Institute for Occupational Safety and Health, Cincinnati, Ohio, USA.
authors: James H
authors: JH
authors: Yiin
authors: Division of Surveillance, Hazard Evaluations, and Field Studies, National Institute for Occupational Safety and Health, Cincinnati, Ohio, USA.
authors: Travis L
authors: TL
authors: Kubale
authors: Division of Surveillance, Hazard Evaluations, and Field Studies, National Institute for Occupational Safety and Health, Cincinnati, Ohio, USA.
authors: Thomas R
authors: TR
authors: Hales
authors: Division of Cancer Epidemiology and Genetics, National Cancer Institute, Gaithersburg, Maryland, USA.
authors: Dalsu
authors: D
authors: Baris
authors: Division of Cancer Epidemiology and Genetics, National Cancer Institute, Gaithersburg, Maryland, USA.
authors: Shelia H
authors: SH
authors: Zahm
authors: UC Davis Department of Public Health Sciences, University of California Davis, Davis, California, USA.
authors: James J
authors: JJ
authors: Beaumont
authors: Division of Surveillance, Hazard Evaluations, and Field Studies, National Institute for Occupational Safety and Health, Cincinnati, Ohio, USA.
authors: Kathleen M
authors: KM
authors: Waters
authors: Division of Surveillance, Hazard Evaluations, and Field Studies, National Institute for Occupational Safety and Health, Cincinnati, Ohio, USA.
authors: Lynne E
authors: LE
authors: Pinkerton
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D002423:Cause of Death; D002641:Chicago; D015331:Cohort Studies; D061388:Firefighters / Q000706:statistics & numerical data*; D006801:Humans; D015994:Incidence; D007938:Leukemia / Q000453:epidemiology* / Q000209:etiology / Q000503:physiopathology; D008175:Lung Neoplasms / Q000453:epidemiology* / Q000209:etiology / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009784:Occupational Diseases / Q000453:epidemiology / Q000209:etiology* / Q000503:physiopathology; D016273:Occupational Exposure / Q000009:adverse effects*; D015143:Philadelphia; D011379:Prognosis; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D018570:Risk Assessment; D012495:San Francisco; D016019:Survival Analysis