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Hazard ratios of lung cancer as a smooth function of A) unlogged and B) logged cumulative silica exposure estimated by penalized spline models (df = 2), China, 1960–2003. Solid lines represent hazard ratios of 25-year lagged cumulative silica exposure, with dotted lines indicating the 95% confidence interval. The vertical solid line represents the 95th percentile of cumulative silica exposure. For simplicity of presentation, the reference value of silica exposure was set to 0.
