Chronic bronchitis in ex-coal miners working in the steel industry

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Abstract
Lowe, C. R., and Khosla, T. (1972).Brit. J. industr. Med.,29, 45-49. Chronic bronchitis in ex-coal miners working in the steel industry. Data are presented comparing ventilatory capacity and prevalence of chronic bronchitis in 3 012 ex-coal miners and 9 361 non-miners of similar age and social class, all employed at the time of the investigation in two intergrated steel works in South Wales. The ex-miners had substantially more chronic bronchitis and a poorer ventilatory capacity than the non-miners irrespective of age and smoking habits. Among smokers, 24·9% of ex-miners aged 45 to 54 had chronic bronchitis compared with 18·6% of non-miners. The corresponding prevalence rates among non-smokers of the same age group were 12·0 and 7·7 respectively. Smoking was a more important factor than coal mining. For example, the non-miners aged 45 to 54 who smoked had a higher prevalence rate of chronic bronchitis (18·6%) than the ex-miners who had never smoked (12·0%). Smoking also appeared to be a more important factor than age. For the non-miners who had never smoked there was no increase in prevalence with age; it remained at about 5% in adult life (25 to 34) until near retirement (55 to 64). Among the ex-miners the ventilatory capacity showed a decline with increasing number of years spent below ground, with a tendency to level off after 10 to 15 years. The mean ventilatory capacity of ex-miners aged 45 to 54 years who had worked 10 or more years below the ground equalled the mean level of non-miners 10 years older, in the age group 55 to 64 years. The possibility that the movement of bronchitics out of coal mines may explain these differences is discussed.