Irregularly shaped small shadows on chest radiographs, dust exposure, and lung function in coalworkers' pneumoconiosis.

The predominant shapes of small opacities on the chest radiographs of 895 British coalminers have been studied. The aims were to determine whether irregular (as distinct from rounded) small opacities can be identified reproducibly, whether their occurrence is related to dust exposure, and whether they are associated with excess prevalence of respiratory symptoms or impairments of lung function. Six of the doctors responsible for regular radiological surveys of all British coalminers each classified all 895 radiographs twice and independently, using the International Labour Organisation's 1980 classification system. The majority view was that 39 films showed predominantly irregular small opacities, 131 showed predominantly small rounded opacities, and 587 showed no small opacities. Readers' opinions varied about the presence and shapes of shadows on the other 138 films. In general, consistency between readers (and within readers on repeated viewings) was satisfactory. The occurrence and profusion of irregular shadows were related significantly both to the men's ages and additionally to their cumulative exposure to respirable coalmine dust as determined from 15 years' dust monitoring close to where the miners had worked. For any given level of exposure, the average level of profusion of the small irregular opacities was less than the corresponding profusion of small rounded opacities. The prevalence rates of chronic cough and phlegm, and of breathlessness, were higher in those with small irregular opacities than in those with no small opacities (category 0/0), but the differences were not statistically significant after adjustment for other factors including smoking habits. The presence of irregular (but not rounded) small shadows was associated with an impairment in respiratory function averaging about 190 ml deficits in both FEV1 and FVC. These deficits were not explicable in terms of the men's ages, body sizes, and smoking habits and they were in addition to the lung function losses attributable to the miners' dust exposure as such. It is concluded that the presence and profusion of small irregular opacities should be taken into consideration when assessing the severity of coalworkers' simple pneumoconiosis.

Characteristics of coalminers who have suffered excessive loss of lung function over 10 years.

From a longitudinal study of respiratory health of coalminers, we have selected 29 smokers and 12 non-smokers with the greatest decline in FEV1 over a ten year period and have compared them with 29 smokers and 14 non-smokers with the least decline. In order to identify syndromes associated with rapid decline in FEV1, we made a clinical and physiological examination of these men five years after the end of the ten year period of measured FEV1 decline. There was no substantial difference in mean lung function between rapid and slow decliners at the time of examination. However, the rapid decliners as a group had an excess of respiratory symptoms, a significantly lower mid-expiratory flow rate and an excess of early and mid-inspiratory crackles on auscultation. Lung function was only abnormal by conventional standards in one third of the smoking rapid decliners. These men had either airflow obstruction (accompanied in three cases by evidence of emphysema) or a concentric reduction of both FEV1 and FVC. There was no excess of atopy nor of history of childhood respiratory illness in rapid decliners. We conclude that it is likely to be difficult to detect the rapid decliners among working men on the basis of a single examination and that at present detection must depend on serial measurements of FEV1.