1. Significant risk increase with silica exposure in tin miners (PAH, radon, arsenic likely important confounders); non-significant exposure response in pottery workers; author states: only "limited support" for association of silica exposure and lung cancer; relationship;with silicosis
2. Elevated lung cancer risk only in stone shed workers employed prior to 1930
3. foundries >20 yrs; "Correlation" found between silicosis at time of radiography (1967-9) and lung cancer incidence during follow up (through 1985); probable confounders
4. By the end of 1987, of 628 deaths observed, 59 were from lung cancer (SMR 1-43) and 77 were from non-malignant respiratory disease (SMR 2-27). Mortality of white men in the USA was used as the reference population, but comparison against local county rates gave similar results. Semiquantitative measures of cumulative exposure, estimated from work histories and information of past environmental conditions in the plant, were shown to correlate with relative risks for both lung cancer and non-malignant respiratory disease. A weighting procedure, applied to adjust these exposure estimates for respirator use, could conceivably have introduced some bias into the analyses. As judged by the limited information obtained on cigarette smoking, there was no indication of important confounding from this source. A study of past chest radiographs in this cohort, the results from which will be linked to updated mortality information, has been initiated but this investigation is still underway
5. We are aware of the results of two further cohort studies which have been presented orally, one at an international meeting in Cincinnati in September 1992 (Carta et a!)23 and the other at the annual meeting of the British Thoracic Society in December 1992 (Benn et al).24 Neither reported evidence of excess risk, but final assessment must await their full publication. Investigators at the US National Institute of Occupational Safety and Health (NIOSH) have performed an update of their mortality study at the Homestake Mine, the results of which have recently been presented.25 Mortality from lung cancer was not significantly increased when national rates were used (1-13; 95% CI 0 93 to 1-36); there was a marginal excess when county rates were employed (1I 27