Silicosis in the twenty first century.

flint) is perhaps the oldest occupational disease, probably existing in the paleolithic period. Hippocrates and Pliny refer to the disorder. Some of the most tragic and wanton examples of occupational disease were due to silicosis, for example, how table blade grinding in Sheffield (1886) robbed workers of 25 years of life, or the Gauley Bridge disaster in West Virginia (1931). Perusing a recent standard pulmonary medicine textbook would suggest that simple silicosis is no longer a problem as it is " not associated with impairment or disability and even without effect on longevity in many although not all ". 1 Case closed, the silicosis story is over, or is it? In this issue of Occupational and Environmental Medicine, t' Mannetje and co-workers answer this question with an elegant and resounding " no " ! 2 In a carefully designed pooled analysis a clear exposure-response relation for silicosis and mortality is shown. Increased mortality is also seen at exposure levels below the current US Occupational Health and Safety Administration's permissible exposure limit (PEL) of 0.10 mg/m 3 for respirable crystalline silica. This conclusion is the culmination of considerable new knowledge concerning dose-response relations and method-ological developments in the past few decades. New knowledge has accumulated concerning associations between silica exposure and pneumoconiosis, Mycobacterium tuberculosis, and chronic obstructive pulmonary disease. A key development has been the classification of silica as a human carcinogen (class 1) in 1996 by the International Agency for Research on Cancer (IARC). 3 One of the silicosis related disappointments at the close of the past century was the failure to develop new treatments for pulmonary fibrosis based on the once promising tetrandrine and polyvinylpridine-N-oxide research. All silicosis related questions have not yet been answered. There is a need for improved radiographic diagnosis of sili-cosis. Experience from asbestos has shown that negative chest radiographs do not exclude the presence of pathologically demonstrable interstitial fibrosis. 4 Accurate and standardised chest radio-graphs are key in the diagnosis and prevention of silicosis. The International Labour Office's existing guidelines and standard radiographs are over 20 years old. The new ILO digitised version is being prepared and will hopefully be available in the near future. Standard-ised chest radiographs are not only helpful in diagnosing pneumoconioses, but also other forms of interstitial lung disorders. There is increasing experience with the use of high resolution computed tomography (HRCT). HRCT appears to be more accurate in the …