ABSTRACT
From the time of Ramazzini (1633-1714) until the twentieth century symptoms and signs were the only clinical and epidemiological criteria available for the diagnosis of occupational respiratory diseases during life. Radiography eventually allowed objective assessment, with acceptable specificity [1], of the prevalence of silica and coal pneumoconioses, the two commonest industrial pulmonary complaints of the period. The inevitable emphasis on radiographic evaluation led to refinements in methodology which increased the accuracy and sensitivity of the technique for epidemiological purposes; major advances related 12to the control of observer variation and the development of quantitative (grading) procedures. As a result, some understanding was obtained of the relationships among radiographic response, exposure, and functional status. These advances, together with improved measures for environmental appraisal and control, provided a rational approach to the design of appropriate surveillance programs and permitted the setting of reasonable confidence limits for the incidence of new cases in the future.
