Disability and coal workers' pneumoconiosis.

The Industrial Injuries Advisory Council has reaffirmed the view that simple pneumoconiosis does not produce disability or shorten life. This is often true but, without overlooking the importance of chronic bronchitis, such conclusions are wrong in many instances.Chronic bronchitis is probably commoner in miners without pneumoconiosis than in those with it, and an uneven distribution of bronchitis may mask the effects of pneumoconiosis. Cough and sputum in a miner with pneumoconiosis are not always due to chronic bronchitis. Disability is usually judged on measurement of vital capacity and forced expiratory volume, factors which cannot be expected to be significantly altered by simple pneumoconiosis alone. Other tests may show abnormalities which lead to ventilation and perfusion inequalities and to an increase in the ventilatory cost of exercise. Focal emphysema, often a consequence of simple pneumoconiosis, develops slowly and its influence on disability is delayed.Disagreements arise because epidemiologists expect all lungs with simple pneumoconiosis react in the same way, and they want a quantitative relation between simple pneumoconiosis and emphysema before attributing one to the other.There are major difficulties in assessing disability but there is little justification for the regular application of the rule that if the results of ventilatory tests are normal disability is not present and if they are abnormal this is due to something other than simple pneumoconiosis.