Silica and progressive systemic sclerosis (scleroderma): evidence for workers' compensation policy.

The occurrence of several confirmed cases of progressive systemic sclerosis (scleroderma) among male miners prompted a request by a member of the provincial parliament (MPP) of Ontario that the Industrial Disease Standards Panel (IDSP) evaluate the evidence for an occupational connection. A number of publications in reputable peer-reviewed medical journals offer case-control evidence gathered over four decades on three continents showing a rather clear-cut relationship between occupational exposure to crystalline silica and scleroderma. This article summarizes the evidence for a causal relationship and describes the process by which the members of the panel, using the criteria developed by Sir Austin Bradford Hill as a guide, made a finding of probable connection, the term mandated by the Workers' Compensation Act of Ontario. It provides insight into the difficulties encountered by those setting occupational disease policy when scientific certainty is unobtainable.