There were three major new findings: (a) long term (>5 years) occupational exposure to cold and draught was associated with a significantly increased prevalence of chronic bronchitis; compared with others, and adjusted for confounders, the odds ratio (OR) with 95% confidence interval (95% CI) was 1.4 (1.1 to 1.7), p=0.004; (b) a significant J shaped association existed between alcohol use and bronchitis, p<0.001, with the lowest prevalence found among moderate users; (c) a significant gene by environment association existed between smoking and the NS-phenotype in the MNS blood group; only among smokers was the NS-phenotype associated with a significantly decreased risk of chronic bronchitis, OR 0.67 (0.47-0.97), p=0.02.