Environmental risk factors for lung cancer in Iran: a case-control study

Methods Between October 2002 and October 2005, 242 (178 male, 64 female) patients with histologically confirmed lung cancer and two controls for each patient (242 hospital controls and 242 visiting healthy controls) matched for age, sex and place of residence were interviewed using a structured questionnaire on potential risk factors for lung cancer, including environmental and occupational exposures. Associations between risk factors and lung cancer were assessed using conditional logistic regression. Results Smokers were 66.5% of all cases (85.4% of men and 14.1% of women) and smoking was the strongest correlate of lung cancer in multivariate analysis [odds ratio (OR) 5.4, 95% confidence interval (CI) 3.2-8.9]. Occupational exposures to inorganic dusts (OR 4.2, 95% CI 2.8-6.7), chemical compounds (OR = 3.4, 95% CI 2.1-5.6) and heavy metals (OR 3.0, 95% CI 1.3-7.0) were also independent risk factors for lung cancer. Conclusions In our study, smoking was the principal risk factor for lung cancer. However, preventable exposures in the environment, including occupational settings, should not be ignored.