PATTERNS OF MORTALITY IN ASBESTOS FACTORY WORKERS IN LONDON* M. L. Newhouse TUC Centenary Institute of Occupational Health London School of Hygiene and Tropical Medicine London WCIE 7HT. England G. Berry MRC Pneumoconiosis Unit Llandough Hospital Penarth, Glamorgan CF6 IXW, Wales
’ This paper reports the results of a mortality study of workers employed at an East London asbestos factory. The factory opened in 1913, at first producing chiefly asbestos textiles, but later, producing also insulation materials, particularly asbestos pipe sections and a variety of other products. Crocidolite asbestos was used until the late 1950s but also chrysotile and amosite. Both men and women were employed. The factory closed in 1968. The male cohort of 4600 men consists of all males who began work between April I , 1933, the date of implementation of the Asbestos Regulations of 1931, and March 31, 1964; the female cohort consists of 922 women, all of whom were first employed between January 1, 1936 and December 31, 1942, a period when wartime identity records facilitated followup. Identification details of these workers were sent to the Central Registers of the National Health Service and to the National Insurance Scheme, now administered by the Department of Health and Social Security. These registers identified the vital status of the workers and subsequently sent to us copies of death certificates for the deceased and for those who died during the study period. Previous reports on this study have been published.’-’ The present study was continued to December 31, 1975 and thus includes 5 additional years of data. Jobs have been classified into six grades of exposure.’ There was little difference in experience between grades 1-3 and grades 5 and 6, and these two groups are classified as “low-moderate” and “severe” exposure, respectively. The experience of laggers is considered separately. The levels of dust exposure have recently been reviewed and suggest that before 1945, the dust levels in such processes as opening, carding, and sectional pipe making and in most other production jobs averaged 20 fibers/ml or higher. In jobs classified by the authors as “low-moderate,” asbestos levels in the air were probably 5-10 fibers/ml. Only in nonproduction jobs and, possibly, brake-lining departments and departments that make rubber jointings were these levels below 5 fibers/ml. In 1946. dust suppression improved, and dust levels were probably reduced by 50%. In 1955, the textile departments moved to another location, and factory hygiene further improved, but many areas in the factory may have contained levels above the current industrial standard of 2 fibers/ml.
*This study was financed by a grant from the Medical Research Council.
53 0 0 7 7 - 8 9 2 3 / 7 9 / 0 3 3 ~ 5 3 $1.75/00 1979, NYAS
54
Annals New York Academy of Sciences
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Newhouse 8~Berry: Asbestos Mortality
55
MALECOHORT There have been 775 deaths among the male workers. An analysis of the 545 deaths that occurred among workers, excluding laggers, who had been followed for 10 years or longer is presented in TABLE1. Asbestos-related disease is rarely if ever manifest in those dying within 10 years of first exposure. In the Tables, the deaths from mesothelial tumors are given in parentheses but are included in the total number of observed deaths in any particular diagnostic category. There were 46 deaths from mesothelial tumors, 19 pleural and 27 peritoneal. All have been validated by histologic examination. Nearly all of the pleural tumors were identified among the intrathoracic tumors (carcinoma of the lung and pleura, ICD 162, 163). The peritoneal tumors weie included with gastrointestinal tumors if certified as a peritoneal mesothelioma (ICD 158) or if confused with carcinoma of the bowel or pancreas. They were included with “other cancers” if certified as carcinomatosis (ICD 199) or as sarcoma or other tumors. Two deaths from mesothelial tumors were identified among causes of death not shown in the Tables. There were, apart from pleural mesothelioma, 103 deaths from carcinoma of the lung, which remains the most common tumor of asbestos workers. Statistically significant excess mortality from chronic respiratory disease is only TABLE2 LAGGERS AND MATES ( I 368
All causes
Cancers of lung and pleura (ICD 162,163) Gastrointestinal cancer (ICD 150-158) Other cancers Chronic respiratory disease
MALES)
Observed
Expected
83*(10) 25*(4)
51.2 5.6 4.3 4.1 1.4
8 (5)
8 12
*p < 0.001.
seen, as previously, among those with long and severe exposure. Asbestosis was given as the cause of death in 13 instances but as the underlying cause of death in 34 of the deaths from lung cancer and in 27 of the deaths from either pleural or peritoneal mesothelioma. In four instances, coronary thrombosis was the actual cause of death. In the majority of the above cases, exposure had been long and severe. TABLE2 shows the mortality experiences of the laggers. The majority of these men were first employed after 1955. It is the custom, however, for laggers to work on contract for various employers, and some may have had previous exposure, so we are not entirely sure of their durations of exposure. Only approximately 2% of the entire group has been followed for 30 years or longer, but to date their experience is not dissimilar from that of other severely exposed male workers. Mortality experience was also examined according to the length of followup, and an analysis of the standardized mortality ratios (SMRs) for cancers of the lung and pleura is presented in TABLE 3. In general, the SMR increases with increased length of followup and with increasing exposure, but for those with long exposure, the SMRs are higher in the group with followups between 20 and 30 years. Only 20% of these workers have been followed up for 30 years or longer, and currently about half of the deaths from mesothelial tumors occurred between 20 and 30 years after their first
56
Annals New York Academy of Sciences TABLE3 LUNG A N D PLEURA
C A N C E R S OF THE ~
~
IN
~
MALES(SMRS) ~~
~~~
~~~
Low to Moderate
Length of Follow-up (years) 10-20 2G30 30 +
Exposure 2 Years 104 159 278
Severe Exposure c 2 Years > 2 Years
112 26 1 I84
255 218 265
463 67 5 446
employment. However, as has been demonstrated previ~usly,~ the number of deaths from mesothelial tumors will continue to rise for some time. In TABLE 4, we have made a finer subdivision of job categories and of periods of employment in the factory. It is noteworthy that in categories 1 and 2, ground workers, canteen workers, and productive workers with very little and short exposures to dust, the SMR was 176, and there were three deaths from mesothelial tumors. Up to 1955, the estimated level of asbestos in the air was 2-5 fibers/ml. However, when we turn to the death rates for mesothelial tumors graded by exposure category (TABLE5), we find that the rates reveal, as in previous a n a l y ~ e sa, ~ very definite relationship to length and severity of exposure. FEMALECOHORT Due to name changes at marriage, women were more difficult to trace than were men. and the vital status of only 77% was ascertained in 1971. By December 31, 1975. 225 had died. Because the last date of entry to the cohort was the end of 1942, all women who have survived and were traced have been followed for more than 30 years. Over 400 women were employed in the traditionally female jobs of carding, spinning, and doubling; 100 were employed in mattress making. Crocidolite was used heavily in textile departments, exposure was generally estimated to be very high, and women were also employed in other production departments, and also, a small group in offices, canteens, and other low-exposure departments. The same pattern of analyses has been adopted, and TABLE6 shows the observed versus the expected mortality in the general population, for groups with 10 years or more of followup. TABLE4 CANCERS OF LUNG A N D PLEURA(SMRs)
Exposure Category Low to moderate 1-2 3
Duration of Exposure 2 2 Years
2-5 Years
5 or More Years
176 I26
0 351
216 152
247 238
227 236
714 567
Severe 4 5
Newhouse & Berry: Asbestos Mortality,
57
In the low-moderate exposure group, there was one death from a mesothelialpleural tumor. In all, there were 13 pleural-mesothelial tumors ideptified and eight peritoneal tumors, approximately the same proportion of all deaths (( 10%) as among the males. Among the severely exposed women with long exposures, there was a greater excess of lung cancer than among males with similar exposure. Also, apart from peritoneal mesotheliomas, there was an excess of deaths from gastrointestinal tumors and other cancers. Cancers of the ovary, uterus, and breast were analyzed separately. In the group of severely exposed women with long periods of employment, statistically significant excesses of cancer of the breast (obs., 6; exp., 2.1; p < 0.05) and ovary (obs., 3; exp., 0.74; p < 0.05) were noted. Not too much reliance can be placed on a single set of figures from one comparatively small cohort of women, and other factors related to marital status and parity that may operate in industrially employed women may be of importance. As in the males, the mesothelioma death rate (TABLE 5) relates clearly to the degree and length of exposure. T A E I C5 MMOTHELIOMA DEATHRATES ~
Exposure Category and Duration (years) Males Low to moderate
’ This paper reports the results of a mortality study of workers employed at an East London asbestos factory. The factory opened in 1913, at first producing chiefly asbestos textiles, but later, producing also insulation materials, particularly asbestos pipe sections and a variety of other products. Crocidolite asbestos was used until the late 1950s but also chrysotile and amosite. Both men and women were employed. The factory closed in 1968. The male cohort of 4600 men consists of all males who began work between April I , 1933, the date of implementation of the Asbestos Regulations of 1931, and March 31, 1964; the female cohort consists of 922 women, all of whom were first employed between January 1, 1936 and December 31, 1942, a period when wartime identity records facilitated followup. Identification details of these workers were sent to the Central Registers of the National Health Service and to the National Insurance Scheme, now administered by the Department of Health and Social Security. These registers identified the vital status of the workers and subsequently sent to us copies of death certificates for the deceased and for those who died during the study period. Previous reports on this study have been published.’-’ The present study was continued to December 31, 1975 and thus includes 5 additional years of data. Jobs have been classified into six grades of exposure.’ There was little difference in experience between grades 1-3 and grades 5 and 6, and these two groups are classified as “low-moderate” and “severe” exposure, respectively. The experience of laggers is considered separately. The levels of dust exposure have recently been reviewed and suggest that before 1945, the dust levels in such processes as opening, carding, and sectional pipe making and in most other production jobs averaged 20 fibers/ml or higher. In jobs classified by the authors as “low-moderate,” asbestos levels in the air were probably 5-10 fibers/ml. Only in nonproduction jobs and, possibly, brake-lining departments and departments that make rubber jointings were these levels below 5 fibers/ml. In 1946. dust suppression improved, and dust levels were probably reduced by 50%. In 1955, the textile departments moved to another location, and factory hygiene further improved, but many areas in the factory may have contained levels above the current industrial standard of 2 fibers/ml.
*This study was financed by a grant from the Medical Research Council.
53 0 0 7 7 - 8 9 2 3 / 7 9 / 0 3 3 ~ 5 3 $1.75/00 1979, NYAS
54
Annals New York Academy of Sciences
3
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8
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Newhouse 8~Berry: Asbestos Mortality
55
MALECOHORT There have been 775 deaths among the male workers. An analysis of the 545 deaths that occurred among workers, excluding laggers, who had been followed for 10 years or longer is presented in TABLE1. Asbestos-related disease is rarely if ever manifest in those dying within 10 years of first exposure. In the Tables, the deaths from mesothelial tumors are given in parentheses but are included in the total number of observed deaths in any particular diagnostic category. There were 46 deaths from mesothelial tumors, 19 pleural and 27 peritoneal. All have been validated by histologic examination. Nearly all of the pleural tumors were identified among the intrathoracic tumors (carcinoma of the lung and pleura, ICD 162, 163). The peritoneal tumors weie included with gastrointestinal tumors if certified as a peritoneal mesothelioma (ICD 158) or if confused with carcinoma of the bowel or pancreas. They were included with “other cancers” if certified as carcinomatosis (ICD 199) or as sarcoma or other tumors. Two deaths from mesothelial tumors were identified among causes of death not shown in the Tables. There were, apart from pleural mesothelioma, 103 deaths from carcinoma of the lung, which remains the most common tumor of asbestos workers. Statistically significant excess mortality from chronic respiratory disease is only TABLE2 LAGGERS AND MATES ( I 368
All causes
Cancers of lung and pleura (ICD 162,163) Gastrointestinal cancer (ICD 150-158) Other cancers Chronic respiratory disease
MALES)
Observed
Expected
83*(10) 25*(4)
51.2 5.6 4.3 4.1 1.4
8 (5)
8 12
*p < 0.001.
seen, as previously, among those with long and severe exposure. Asbestosis was given as the cause of death in 13 instances but as the underlying cause of death in 34 of the deaths from lung cancer and in 27 of the deaths from either pleural or peritoneal mesothelioma. In four instances, coronary thrombosis was the actual cause of death. In the majority of the above cases, exposure had been long and severe. TABLE2 shows the mortality experiences of the laggers. The majority of these men were first employed after 1955. It is the custom, however, for laggers to work on contract for various employers, and some may have had previous exposure, so we are not entirely sure of their durations of exposure. Only approximately 2% of the entire group has been followed for 30 years or longer, but to date their experience is not dissimilar from that of other severely exposed male workers. Mortality experience was also examined according to the length of followup, and an analysis of the standardized mortality ratios (SMRs) for cancers of the lung and pleura is presented in TABLE 3. In general, the SMR increases with increased length of followup and with increasing exposure, but for those with long exposure, the SMRs are higher in the group with followups between 20 and 30 years. Only 20% of these workers have been followed up for 30 years or longer, and currently about half of the deaths from mesothelial tumors occurred between 20 and 30 years after their first
56
Annals New York Academy of Sciences TABLE3 LUNG A N D PLEURA
C A N C E R S OF THE ~
~
IN
~
MALES(SMRS) ~~
~~~
~~~
Low to Moderate
Length of Follow-up (years) 10-20 2G30 30 +
Exposure 2 Years 104 159 278
Severe Exposure c 2 Years > 2 Years
112 26 1 I84
255 218 265
463 67 5 446
employment. However, as has been demonstrated previ~usly,~ the number of deaths from mesothelial tumors will continue to rise for some time. In TABLE 4, we have made a finer subdivision of job categories and of periods of employment in the factory. It is noteworthy that in categories 1 and 2, ground workers, canteen workers, and productive workers with very little and short exposures to dust, the SMR was 176, and there were three deaths from mesothelial tumors. Up to 1955, the estimated level of asbestos in the air was 2-5 fibers/ml. However, when we turn to the death rates for mesothelial tumors graded by exposure category (TABLE5), we find that the rates reveal, as in previous a n a l y ~ e sa, ~ very definite relationship to length and severity of exposure. FEMALECOHORT Due to name changes at marriage, women were more difficult to trace than were men. and the vital status of only 77% was ascertained in 1971. By December 31, 1975. 225 had died. Because the last date of entry to the cohort was the end of 1942, all women who have survived and were traced have been followed for more than 30 years. Over 400 women were employed in the traditionally female jobs of carding, spinning, and doubling; 100 were employed in mattress making. Crocidolite was used heavily in textile departments, exposure was generally estimated to be very high, and women were also employed in other production departments, and also, a small group in offices, canteens, and other low-exposure departments. The same pattern of analyses has been adopted, and TABLE6 shows the observed versus the expected mortality in the general population, for groups with 10 years or more of followup. TABLE4 CANCERS OF LUNG A N D PLEURA(SMRs)
Exposure Category Low to moderate 1-2 3
Duration of Exposure 2 2 Years
2-5 Years
5 or More Years
176 I26
0 351
216 152
247 238
227 236
714 567
Severe 4 5
Newhouse & Berry: Asbestos Mortality,
57
In the low-moderate exposure group, there was one death from a mesothelialpleural tumor. In all, there were 13 pleural-mesothelial tumors ideptified and eight peritoneal tumors, approximately the same proportion of all deaths (( 10%) as among the males. Among the severely exposed women with long exposures, there was a greater excess of lung cancer than among males with similar exposure. Also, apart from peritoneal mesotheliomas, there was an excess of deaths from gastrointestinal tumors and other cancers. Cancers of the ovary, uterus, and breast were analyzed separately. In the group of severely exposed women with long periods of employment, statistically significant excesses of cancer of the breast (obs., 6; exp., 2.1; p < 0.05) and ovary (obs., 3; exp., 0.74; p < 0.05) were noted. Not too much reliance can be placed on a single set of figures from one comparatively small cohort of women, and other factors related to marital status and parity that may operate in industrially employed women may be of importance. As in the males, the mesothelioma death rate (TABLE 5) relates clearly to the degree and length of exposure. T A E I C5 MMOTHELIOMA DEATHRATES ~
Exposure Category and Duration (years) Males Low to moderate
