“…To avoid the influence of sex, it was decided to include in our study only men; to ensure a minimal duration of exposure it was decided to include workers with at least 5 years experience; welders with major chronic respiratory, heart, or chest wall diseases or with previous exposure to respiratory hazards were excluded Of the 182 welders who fulfilled the above criteria 173 (= 95 %) were investigated. Their age ranged from 22-57 (mean 34 1) years; 81 were smokers ( 47 %), 59 never smoked ( 34 %), and 33 ( 19 %) were ex-smokers, the smoking habit being similar to other working males in this country (Racoveanu et al , 1975) After identification of the worker, a respiratory symptoms questionnaire (MRC, 1966) was filled in by interview by one of the authors, attention being paid to the medical and occupational history. The definitions of chronic cough and chronic bronchitis were those recommended by the questionnaire instructions; dyspnea was recorded only if severe enough that the subject had to walk at his own pace on the level; wheezing and paroxysmal dyspnea were recorded only if present frequently between colds The interview was followed by a physical examination W C W C W C W C < 30 30 16 7 5 22 15 59 36 31-40 41 22 17 5 21 14 79 41 41-50 9 8 7 4 14 5 30 17 51 + 1 2 2 2 2 2 5 6 Total 81 48 33 16 59 36 173 1 oo W = welders; C = controls.…”