PATTERNS OF MORTALITY IN ASBESTOS FACTORY WORKERS IN LONDON*

Transcription

1 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 191, 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 195s but also chrysotile and amosite. Both men and women were employed. The factory closed in 196. The male cohort of 46 men consists of all males who began work between April I, 19, the date of implementation of the Asbestos Regulations of 191, and March 1, 1964; the female cohort consists of 922 women, all of whom were first employed between January 1, 196 and December 1, 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 1, 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- 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 2 fibers/ml or higher. In jobs classified by the authors as low-moderate, asbestos levels in the air were probably 5-1 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 dust suppression improved, and dust levels were probably reduced by 5%. 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 /79/~5 $1.75/ 1979, NYAS

2 54 Annals New York Academy of Sciences t! B e P e, 1!2 t P * B La e f d I. f s

3 Newhouse ~ Berry: Asbestos Mortality 55 MALE COHORT 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 1 years or longer is presented in TABLE 1. Asbestos-related disease is rarely if ever manifest in those dying within 1 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, 16). The peritoneal tumors weie included with gastrointestinal tumors if certified as a peritoneal mesothelioma (ICD 15) 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, 1 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 TABLE 2 LAGGERS AND MATES (I 6 MALES) Observed Expected All causes *(1) 51.2 Cancers of lung and pleura (ICD 162,16) 25*(4) 5.6 Gastrointestinal cancer (ICD 15-15) (5) 4. Other cancers 4.1 Chronic respiratory disease *p <.1. seen, as previously, among those with long and severe exposure. Asbestosis was given as the cause of death in 1 instances but as the underlying cause of death in 4 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. TABLE 2 shows the mortality experiences of the laggers. The majority of these men were first employed after 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 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. 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 2 and years. Only 2% of these workers have been followed up for years or longer, and currently about half of the deaths from mesothelial tumors occurred between 2 and years after their first

4 ~ ~ ~ ~~ ~~~ ~~~ 56 Annals New York Academy of Sciences TABLE CANCERS OF THE LUNG AND PLEURA IN MALES (SMRS) Length of Low to Moderate Exposure Severe Exposure Follow-up (years) <2 Years >2 Years c2 Years >2 Years G I 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 (TABLE 5), we find that the rates reveal, as in previous analy~es,~ a very definite relationship to length and severity of exposure. FEMALE COHORT 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 By December 1, 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 years. Over 4 women were employed in the traditionally female jobs of carding, spinning, and doubling; 1 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 TABLE 6 shows the observed versus the expected mortality in the general population, for groups with 1 years or more of followup. TABLE 4 CANCERS OF LUNG AND PLEURA (SMRs) Exposure Duration of Exposure Category 22 Years 2-5 Years 5 or More Years Low to moderate I Severe

5 Newhouse & Berry: Asbestos Mortality, 57 In the low-moderate exposure group, there was one death from a mesothelialpleural tumor. In all, there were 1 pleural-mesothelial tumors ideptified and eight peritoneal tumors, approximately the same proportion of all deaths (( 1%) 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 <.5) and ovary (obs., ; exp.,.74; p <.5) 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. TAEIC 5 MMOTHELIOMA DEATH RATES Exposure Category and Duration ~ Rate per 1, (years) Pleura Peritoneum S years S years Males Low to moderate < I ,5 9 Severe < ,42 14 >2 7 I Laggers <2 2 7,9 6 > ,69 I6 Females Low to moderate Severe <2 5 9, , 6 ASBESTOS AND CIGARETTE SMOKING A survey of smoking habits of a selected cohort of male factory and all surviving female workers was made between April and August A greater proportion of both men and women smoked, or had smoked, than in the general population of England and Wales, after taking into account the factor of age.6 Among men, 74% of the factory population smoked compared with 66% expected from national figures. For women, 49% smoked, and 2% had previously smoked compared with 4% and 1% expected, respectively. Thus, the excess mortality due to lung cancer reported above is in part due to smoking; however, this bias is small and may be represented by factors of 1.1 and 1.2 for men and women, respectively. A prospective survey of

6 TABLE 6 MORTALITY EXPERIENCES OF FEMALE FACTORY WORKERS a E Exposure Category Severe E Low to Moderate <2 Years >2 Years 4 (9) (96) Cause of Death Observed Expected Observed Expected Observed Expected g v) z CD (199) % 2 All causes 4*(1) 22. t(1) 65.6 W(7).4 P, Cancers of lung and pleura (ICD 162,16) *(1).5 15$(7) ~ 4 ). e Gastrointestinal cancer (ICD ) I.9 14t(4) w 2.6 Other cancers (2) $(1) 5. Y -7 Chronic respiratory disease lot.2 *p <.5. g tp <.1. a $p <.1. 2

7 Newhouse & Berry: Asbestos Mortality 59 TABLE 7 OBSERVED AND EXPECTED MORTALITIES FROM LUNG CANCER (AUGUST 1971 TO DECEMBER 1975) Smokinp. Habit Observed Exwcted' Men Never I.6 Past and current Women Never I.1 Past and current 6.97 'Allowing for smoking habits. mortality is now in progress. Only 2 deaths from lung cancer had occurred by December 1, 1975, and the current results are presented in TABLE 7. Two of the lung cancer deaths occurred in workers who had never smoked. There are insufficient data to analyze in more detail, but the results are consistent with our earlier findings5 that asbestos and smoking appear to combine multiplicatively in producing lung cancer. Firm conclusions must, however, await the accumulation of more data. 1 MALES 9 - *; a 7 6 I * Years since first employment FIGURE 1. Proportion of surviving male subjects.

8 6 Annals New York Academy of Sciences Finally, FIGURES 1 and 2 show the proportions of males and females, respectively, who survived at 5-year intervals after their first employment compared to the expected survival rates in unexposed populations. In the males, the rates begin to decline more steeply than expected about 25 years afer first exposure; in the women, this decline began about 5 years earlier. At 5 years after first exposure, the differences between the observed and expected survival rates are approximately 7% for men and 1% for women. Under conditions that prevailed in the past, men and women who start work in their early twenties would have markedly diminished life expectancies. FEMALES I I I Years since first employment FIGURE 2. Proportion of surviving female subjects. REFERENCES 1. NEWHOUSE, M. L A study of the mortality of workers in an asbestos factory. Brit. J. Ind. Med NEWHOUSE, M. L., G. BERRY, J. C. WAGNER & M. E. TUROK A study of the mortalityof female asbestos workers. Brit. J. Ind. Med NEWHOUSE, M. L Asbestos in the workplace and the community. Ann. Occup. Hyg NEWHOUSE, M. L. & G. BERRY Predictions of mortality from mesothelial tumors in an asbestos factory. Brit. J. Ind. Med. : BERRY, G., M. L. NEWHOUSE & M. E. TUROK Combined effects of asbestos exposure and smoking on mortality from lung cancer in factory workers. Lancet: TODD, G. F Statistics of Smoking in the United Kingdom. 6th edit. Research paper 1. Tobacco Research Council. London.