Radiological surveys of working quarrymen and quarrying communities in Caernarvonshire.

Interest in the possible occupational lung diseases associated with slate-quarrying appears to date from the Registrar-General's Decennial Supplement, 1921, on Occupational Mortality (Registrar-General, 1927). Britten's review (Britten, 1928) showed that slate-masons and slate-workers had a significantly raised mortality from respiratory tuberculosis although it was much lower than that of tinand copper-miners. At roughly the same time, Wade (1927) called attention to the excessive mortality from tuberculosis of the slate-workers in the Gwyrfai rural district in North Wales. Since then, most of the references in the international literature about this subject have referred to Wales, but descriptions of cases of pneumoconiosis in slatequarry workers have been published in other countries. In France, Feil (1935) found relatively little pulmonary disease amongst slate-workers in Mayenne and Anjou. He attributed this to the low content of free silica (7%) in the slates there. In Germany, Schairer (1940) described egg-shell calcification in two slate workers; Koelsch (1950) described the radiographic appearances, and Ceelen (1951) described one case. In Italy, Frola (1942) described the radiographic appearances in 34 slateworkers; and cases have been reported from the United States by Rogers (1932) and Mansur (1951). In Wales, Wade's report was followed by the survey by Sutherland and Bryson (1930) who found clinical evidence of pulmonary fibrosis amongst 56 out of 120 slate-quarrymen. A few years later Chalke (1933) showed that 28% of the tuberculous males in the county of Caernarvon were slateworkers while this industry only absorbed 11% of the male population. Davies (1939) reported the results of examining 117 slate-workers chiefly from Merionethshire and, as a result, silicosis amongst slate-workers who worked underground was scheduled under the Workmen's Compensation Act. The section of the industry involving work above ground was not so scheduled. Davies (1942) reviewed silicosis amongst coal-miners and slateworkers in Wales. Later a committee of the Ministry of Works, under the chairmanship of Mr. F. Rees, reported on the Welsh slate industry (Ministry of Works, 1947). They considered that the fear of pneumoconiosis was preventing men entering the industry and recommended that the pneumoconiosis problem should be attacked at once. The relative position of tuberculosis mortality in the Gwyrfai rural district has not improved since the time of Wade's original investigation. In 1928 the tuberculosis death rate was 285 per 100,000 persons compared with a figure of 96 for England and Wales. In 1951 the figures were 110 and 31 respectively. In 1952 there was therefore evidence that pneumoconiosis-probably silicosis-was prevalent amongst slate-workers in North Wales, and that the tuberculosis death rate in the slate-quarrying areas was abnormally high. For these reasons, the Gwyrfai Rural District Council asked the Welsh Board of Health for an investigation, and as a result a survey was carried out by the Mass Radiography Service of the Welsh Regional Hospital Board in 1952-53, which is the subject of this paper.