W Chen et al. Am. J. Ind. Med. (2006) Vol.49 p 67 – 76
“Exposures to Silica Mixed Dust and Cohort Mortality Study in Tin Mines: Exposure-Response Analysis and Risk Assessment of Lung Cancer”
In those with silicosis the risk of lung cancer varied with exposure; a clear rise in risk was detected once exposure to total dust exceeded 70 mgm-3 years. Respirable crystalline silica comprised around 4% of total dust in each mine.