Mortality of slate workers in north Wales

In a study in 1975 of the mortality experienced over six years by two groups of men one group had been exposed to slate dust and the other had had no previous exposure to dust. In non-smokers there was no material excess mortality associated with past exposure to dust but in smokers there was a pronounced (26%) excess. In the slate workers the risk for smokers was on average 76% greater than for non-smokers, and increased with severity of pneumoconiosis; in those who had not been exposed to dust the risk was 50% greater for smokers than non-smokers. In ex-smokers among those who had been exposed to slate dust the risk of death was higher in those with the lower lung function initially. No such association was detected in the other groups.