Current views on pathological aspects of asbestosis (the unresolved questions and problems).

The present criteria for the diagnosis of asbestosis are discussed, as are previous attempts to correlate the pathological with the clinical and radiological findings and the problem of the variable distribution of asbestos forms in routine sections taken from undoubted cases of asbestosis. Establishing lesser degrees of asbestosis is important, and lower limits need to be defined. Evidence is presented, with illustrative examples, of the value of concentration techniques; even for diagnostic purposes there is occasionally a need for more sophisticated electron microscopy techniques. The occurrence and the extent of diffuse interstitial inflammatory changes as part of the biological effects of asbestos exposure are illustrated; and the difficulties inherent in cases where there has been exposure to other dusts as well as to asbestos are described.