The Occurrence of Pleural Calcification Among Asbestos Insulation Workers*

The earliest reports of pulmonary asbestosisclinical, anatomical, radiological -made no mention of pleural calcification. We can now appreciate that this absence of comment was not based upon inattention or incompleteness of observation. Rather, the asbestosis seen by Cooke, Wood, Haddow, Stewart, Simson, Lynch, Ellman, Pancoast, Pendergrass, Merewether, was in some respects not the same asbestosis seen today. A result of exposure under much more unfavorable conditions, the pulmonary fibrosis became extensive and disabling more rapidly, bringing patients to medical attention after shorter exposures. Fewer individuals were able to work for many decades in asbestos trades. Another factor which led to thinning out of the ranks was the large number of women among asbestos textile workers, who left work for home and were lost to industrial survey.' Since there were, in addition, many fewer employees in these trades to start with, the number reaching a 20-year-from-onset-of-exposure point of observation was small indeed. As we shall see from data presented here, calcification is usually not seen until this point is reached. Our predecessors, who made so many important contributions to the problem of asbestosis, could not have made this one. I t was not there for them to observe.