Table II displayed the results of a number of studies that investigated silicosis and showed that the risk of silicosis (ILO category 1/1 or more) following a lifetime of exposure at the current OSHA standard of 0.1 is likely to be at least 5±10%. The exposure±response relation for silicosis looks nonlinear [Hnizdo and Sluis-Cremer, 1993], and is probably sigmoidal, as it is for asbestosis [Finkelstein, 1982]. Lifetime exposure at 0.1mg/m3 appears to put workers on the supra-linear portion of the exposure±response curve. Reduction of dust exposures would thus have a greater than linear bene®t in terms of risk reduction. Table II suggests that 30 years exposure at 0.1mg/m3 might lead to a lifetime silicosis risk of about 25%, whereas reduction of the exposure to 0.05mg/m3 might reduce the risk to under 5%.[Hnizdo and Sluis-Cremer, 1993].