title: Lack of a protective effect of cotton dust on risk of lung cancer: evidence from two population-based case-control studies.
abstract: BACKGROUND
  Lung cancer is the leading cause of cancer death in North America. Exposure to cotton dust has previously been reported to decrease the risk of lung cancer.
  
  
  METHODS
  We used data from two large case-control studies conducted in Montreal from 1979-1986 (Study 1) and 1996-2002 (Study 2) respectively, to examine the association between occupational exposure to cotton dust and risk of lung cancer. Cases were diagnosed with incident histologically-confirmed lung cancer (857 in Study 1, 1203 in Study 2). Population controls were randomly selected from electoral lists and frequency-matched to cases by age and sex (533 in Study 1, 1513 in Study 2). Interviews for the two studies used a virtually identical questionnaire to obtain lifetime occupational and smoking history, and several lifestyle covariates. Each participant's lifetime occupational history was reviewed by experts to assess exposure to a number of occupational agents, including cotton dust. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated by unconditional logistic regression, adjusting for potential confounders.
  
  
  RESULTS
  The lifetime prevalence of exposure to cotton dust was approximately 10%-15% in both studies combined, with some variation by study and by sex. Overall there was no decreased risk of lung cancer among subjects exposed to cotton dust. Rather, among all subjects there was a suggestion of slightly increased risk associated with any lifetime exposure to cotton dust (OR = 1.2, 95% CI: 1.0-1.5). This risk appeared to be concentrated among cases of adenocarcinoma (OR = 1.6, 95% CI: 1.2-2.2), and among moderate and heavy smokers (OR = 1.3, 95% CI: 1.0-1.7). There was no association when restricting to cases of either squamous cell or small cell cancer, or among never smokers and light smokers. An analogous examination of subjects exposed to wool dust revealed neither increased nor decreased risks of lung cancer.
  
  
  CONCLUSIONS
  There was no evidence that cotton dust exposure decreased risks of lung cancer.
authors.affiliation: Environmental Epidemiology and Population Health Research Group, University of Montreal Hospital Research Center (CRCHUM), Tour Saint-Antoine, 850 St. Denis Street, Montreal, QC, H2X 0A9, Canada. klyorita@gmail.com.
authors.forename: Krista Yorita
authors.initials: KY
authors.lastname: Christensen
authors.affiliation: Environmental Epidemiology and Population Health Research Group, University of Montreal Hospital Research Center (CRCHUM), Tour Saint-Antoine, 850 St. Denis Street, Montreal, QC, H2X 0A9, Canada. jerome.lavoue@umontreal.ca.|Department of Environmental and Occupational Health, University of Montreal, Montreal, QC, Canada. jerome.lavoue@umontreal.ca.
authors.forename: Jérôme
authors.initials: J
authors.lastname: Lavoué
authors.affiliation: Environmental Epidemiology and Population Health Research Group, University of Montreal Hospital Research Center (CRCHUM), Tour Saint-Antoine, 850 St. Denis Street, Montreal, QC, H2X 0A9, Canada. marie-claude.rousseau@iaf.inrs.ca.|Department of Social and Preventive Medicine, University of Montreal, Montreal, QC, Canada. marie-claude.rousseau@iaf.inrs.ca.|INRS - Institut Armand-Frappier, Laval, QC, Canada. marie-claude.rousseau@iaf.inrs.ca.
authors.forename: Marie-Claude
authors.initials: MC
authors.lastname: Rousseau
authors.affiliation: Environmental Epidemiology and Population Health Research Group, University of Montreal Hospital Research Center (CRCHUM), Tour Saint-Antoine, 850 St. Denis Street, Montreal, QC, H2X 0A9, Canada. j.siemiatycki@umontreal.ca.|Department of Social and Preventive Medicine, University of Montreal, Montreal, QC, Canada. j.siemiatycki@umontreal.ca.
authors.forename: Jack
authors.initials: J
authors.lastname: Siemiatycki
mesh_terms: D000328:Adult; D000368:Aged; D002170:Canada / Q000453:epidemiology; D016022:Case-Control Studies; D032561:Cotton Fiber; D004391:Dust; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000453:epidemiology* / Q000209:etiology* / Q000517:prevention & control; D008297:Male; D008875:Middle Aged; D016273:Occupational Exposure / Q000009:adverse effects*; D016017:Odds Ratio; D011159:Population Surveillance; D012306:Risk
chemical_list: D004391:Dust