. (1971). Brit. J. industr. Med., 28,[226][227][228][229][230][231][232][233][234][235][236]. Insulation workers in Belfast. 3. Mortality 1940-66. One hundred and seventy men were identified as making up the total population of insulation workers in Belfast in 1940. This is an analysis of all the information about deaths that has emerged from tracing these men up to the end of 1966. Five remain untraced, and the mortality experience of the remainder is compared with that of other men in Northern Ireland over the period. There were 98 deaths when only 37 were expected. The number of deaths occurring exceeded those expected throughout the period 1940-66 and the increase was statistically significant during the period 1950-55 and onwards. There was an especially high mortality (compared with other Northern Ireland males) due to cancer of the lung, mesothelioma of the pleura and peritoneum, cancer of the gastrointestinal tract, and fibrotic lesions of the lungs. The ratio of observed over expected deaths was 2-6 for all causes, 3 9 for all cancers, and 17-6 for cancers of the lower respiratory tract and pleura. Those men finally classified as dying from lung cancer showed evidence of lung fibrosis whereas those classified as dying from mesothelioma did not. Comparisons within the group failed to show any relationship between age at first exposure or duration of exposure and the excessive mortality. There were too few non-smokers to show the significance of smoking.The first two studies Langlands, Wallace, and Simpson, 1971) were concerned with the health of men still employed as insulators; the third study is an attempt to evaluate the deaths which have occurred in this occupational group. For a complete picture of the occupational hazard it would also be necessary to find out the proportion of men who had to leave this occupation for medical reasons other than death. But records giving the reasons why men changed to lighter work or became unemployed were nonexistent and information about those who drew sickness benefit was scanty and hard to come by. Therefore, it was decided to restrict the enquiry to the frequency and causes of death. As there were no specific regulations concerning the handling of asbestos in Northern Ireland up to the time of the enquiry, there were no official records of the numbers of men employed. Because of this lack of official recognition, few patients were referred to the pneumoconiosis panels and no special arrangements were in existence for recording the causes of death in this group. The enquiry was conducted in three stages-the identification of the population at risk, the identification of the men who had died and, finally, the analysis of the information which could be obtained about these deaths.To define the population at risk, a preliminary investigation of the employers' and trades union records was made. Work on the other two studies had indicated that these records were not complete and became progressively less so the further back they were traced. But other work on the mali...

A follow-up study of 162 men already working as insulators (laggers) In the first studies of insulation workers (laggers) in Belfast, the men who were still at work showed no gross evidence of disability due to asbestos exposure Langlands et al., 1971). However, investigation of a group of men who had been employed in insulation work in 1940 revealed an unexpectedly high mortality (Elmes and Simpson, 1971). The deaths in excess of those expected were due to lung cancer, mesothelioma and gastrointestinal tumours. There were also some due to pulmonary fibrosis in the earlier years. The men had been followed up to the end of 1966 and of the original 170, five were untraced and 98 had died. This paper reports the fate of the survivors and reviews the mortality experience of the. whole group to give a clearer picture of the health hazard of the occupation over the period . Methods THE POPULATIONThe initial total population of Belfast insulation workers (laggers) in 1940 was 170 men. Details of the method of identifying them are given in the previous paper (Elmes and Simpson, 1971). The survivors were seen at two to three-year intervals as part of a continous surveillance of all past and present workers in Northern Ireland whohad worked

. Insulation workers in Belfast. 2. Morbidity in men still at work. Two hundred and fifty-two (93 Y.) of the insulation workers in Belfast were examined by chest x-ray, questionnaire, clinical examination, and tests of respiratory function. The frequency of chest x-ray abnormality, lung field or pleural, increased from 13 % in men who had worked for less than 10 years to 85 % in men who had worked for 30 or more years in the industry. Pleural calcification was found in 15 x-rays. There was evidence suggesting that some men had pleural fibrosis or calcification due to exposure to asbestos in childhood. Rales were present in 61 % and clubbing in 11 % of men with lung field abnormality, but these were not common when the x-rays showed only pleural abnormality. Where the lung fields were involved there was a restrictive defect with impairment in lung function most marked in the forced vital capacity and single breath carbon monoxide transfer factor, but where the pleura was involved without lung field involvement there was a tendency to impairment of ventilatory function with a normal transfer factor. Cigarette smoking was associated with a greater impairment of lung function than was x-ray abnormality.Asbestos insulation has been used for many years in the Belfast shipyards. Since the second world war it has also been used increasingly in the construction of large buildings such as factories and hospitals. All insulation of ships or buildings in Belfast is subcontracted to a number of firms which specialize in this work. The present survey was undertaken to assess the effect on health of exposure to asbestos in men currently working in the trade, and to obtain a record which will form a baseline for a follow-up of this group of men. MethodsThe men were contacted from lists given by their trade union and their employers. Two hundred and seventy-two men were working as insulators (apprentices, trained insulators, and insulator's labourers) during the present investigation and results from 252 (93%) are available for analysis. These include the 50 men in the series reported in study 1 (Wallace and Langlands, 1971). There were 17 refusals and in three men the results were incomplete. Thirteen women were employed by one of the firms in making asbestos or fibreglass quilts (known as 'mattresses') for insulation work. The women were all seen but their results are not included in the main analysis.The clinical history was taken by one of the authors (M.S.), who is a social worker, using the M.R.C. long respiratory questionnaire with special emphasis on the industrial history (Medical Research Council, 1960). It was not possible to obtain any information about relative exposure to different types of asbestos or to assess the time each individual had spent working with asbestos as distinct from other material, such as fibreglass, used in insulation, but the men were asked whether they had ever done 'limpet spraying' of asbestos which exposes the operator to a high concentration of asbestos dust. A 217

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