Tuberculosis, Silicosis, and the Slate Industry in North Wales 1927-1939

The slate industry had become a commercial enterprise in the counties of Caernarvonshire and Merionethshire in North Wales by the mideighteenth century. 1 At the end of the nineteenth century, this area included the two largest slate quarries in the world, Penrhyn Quarry near Bethesda and the Dinorwic Quarry at Llanberis, and the largest slate mine, Oakeley at Blaenau Ffestiniog, as well as fifty smaller mines and quarries scattered on the hillsides. 2 The industry was at its height at this time, employing 13-15,000 workers. Overseas competition and changing fashions in roofing adversely affected the industry in the early twentieth century and it was never to recover its former prosperity. In 1910 there were still 13,000 workers in the industry, but by 1945 the number had dropped to 3,520. 3 A recent study of the health of the workers in the industry by J. R. Glover et al., published in 1980, showed pneumoconiosis to be very prevalent. 4 Tuberculosis has not been a major problem in that industry or elsewhere in Britain since the early 1950s when streptomycin and related drugs were introduced. However, Glover’s study showed many of the lungs of the older miners to have healed tuberculous lesions, indicating a very high prevalence of tuberculosis among workers in the industry some thirty years previously. Modern epidemiological studies suggest that silicosis and pneumoconiosis predispose to tuberculosis. 5