title: Exposure to environmental tobacco smoke (ETS) and risk of lung cancer in Montreal: a case-control study.
abstract: BACKGROUND
  The objective of the present study was to examine the association between environmental tobacco smoke (ETS) and risk of lung cancer among never smokers, defined as subjects who smoked less than 100 cigarettes in their lifetime.
  
  
  METHODS
  We conducted a population-based case-control study on lung cancer in Montreal, Canada (1996-2000) including 1,203 cases and 1513 controls. The present analysis is restricted to the 44 cases and 436 population controls who reported never smoking and completed the questionnaire on lifetime ETS exposure. Collected information included duration and intensity of exposure from multiple sources: inside home (parents, spouses, roommates and any other co-resident) and outside homes (in vehicles, social settings, and workplace). Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated between ETS and lung cancer, adjusting for age, sex, socioeconomic status (SES), and proxy respondent.
  
  
  RESULTS
  Overall there was no association between ETS cumulative exposure from all sources (measured in pack-years) and lung cancer: OR = 0.98 (95%CI: 0.40-2.38), comparing upper with lower tertiles of exposure. While there were no elevated ORs associated with ever having lived with parents who smoked (OR = 0.62; 95%CI: 0.32-1.21) or with spouses who smoked (OR = 0.39; 95%CI: 0.18-0.85), ETS exposure from sources outside homes was associated with a slight, although non-significant increased risk: OR = 2.30 (95%CI: 0.85-6.19) for the upper 50% exposed. There were no clear differences in ORs by age at exposure to ETS or by histologic type of tumour, though numbers of subjects in subgroup analyses were too small to provide reliable estimates.
  
  
  CONCLUSIONS
  No clear association between lifetime ETS exposure from all sources and increased risk of lung cancer was found in the current study.
authors.affiliation: McLaughlin Center of Population Health Risk Assessment, University of Ottawa, Ottawa, Canada. malzough@uottawa.ca.
authors.forename: Mustafa
authors.initials: M
authors.lastname: Al-Zoughool
authors.forename: Javier
authors.initials: J
authors.lastname: Pintos
authors.forename: Lesley
authors.initials: L
authors.lastname: Richardson
authors.forename: Marie-Élise
authors.initials: MÉ
authors.lastname: Parent
authors.forename: Parviz
authors.initials: P
authors.lastname: Ghadirian
authors.forename: Daniel
authors.initials: D
authors.lastname: Krewski
authors.forename: Jack
authors.initials: J
authors.lastname: Siemiatycki
mesh_terms: D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D016001:Confidence Intervals; D004781:Environmental Exposure; D005260:Female; D006801:Humans; D015994:Incidence; D008175:Lung Neoplasms / Q000139:chemically induced / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D016273:Occupational Exposure; D016017:Odds Ratio; D011792:Quebec / Q000453:epidemiology; D012307:Risk Factors; D014028:Tobacco Smoke Pollution / Q000009:adverse effects* / Q000032:analysis
chemical_list: D014028:Tobacco Smoke Pollution