American Journal of Industrial Medicine 22:49%504 (1992)
Death Certificates in Epidemiological Studies, Including Occupational Hazards: Inaccuracies in Occupational Categories Irving J. Selikoff", MD
We compared death certificates for asbestos-associated diseases (mesothelioma, lung cancer, asbestosis) in two asbestos workers' cohorts. One (insulation workers) had current or recent employment and a strong, continuing union support system which gave them much information about the effects of asbestos exposure. The second cohort, asbestos factory workers, had no such advantage. The factory had closed almost 30 years before, and its workers had dispersed into many areas of the state and nation. Accuracy of medical diagnosis was comparable in the two groups, but occupational listings were not. Three-quarters of the insulators' death certificates told of asbestos work, while virtually none of the factory workers' certificates provided such information, even for deaths of mesothelioma and asbestosis. The data indicate that disease categories, based on medical and pathological diagnoses, at least for asbestos-associated disease, tend to be accurate. Attempts to identify groups at risk by sorting occupational categories can give variable results, good for those with current exposures, much less satisfactory for those with long-past occupational exposures. 0 1992 Wiley-Liss, Inc. Key words: death certificates, occupational categories, asbestos-associated disease
INTRODUCTION
There have long been misgivings about the use of occupations as listed on death certificates in view of known inaccuracies and incompleteness [Lilienfeld, 19881. This has been true even for countries such as the United States and Great Britain, with well-established vital statistics agencies. In the former, for example, NIOSH in 1979 investigated the extent to which state and local vital registration offices coded and stored occupational information quoted on death certificates. Eleven states routinely coded occupation and six did so on a limited basis [Kaminski et al., 19811. Harrington [1984] reviewed British practices and found major flaws. A particularly widespread source of error has been recording the last occupation
*Dr. Selikoff died on May 20, 1992. Mount Sinai School of Medicine of The City University of New York, New York, NY. Address reprint requests to Dr. Stephen Levin, Mount Sinai School of Medicine, One Gustave L. Levy Place, Box 1059, New York, NY 10029-6574. Accepted for publication January 8, 1992. 0 1992 Wiley-Liss, Inc.
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[Harrington, 1984; Dubrow et al., 19871. This is particularly disadvantageous in occupational studies, in which, as Mayers [ 19521 noted more than four decades ago, occupational cancer is “more apt to have been caused by some previous occupational exposure” years before. This has been documented and emphasized repeatedly [Selikoff et al., 19801. Nor can one be at all confident that even the (last) occupation is necessarily accurate. Coggon et al. [1985] studied 39 middle-aged couples. Of 122 occupations detailed by the husbands, only 62 were accurately reported by their wives. Schade and Swanson [ 19881 compared interview lifetime work histories with death certificate entries and obtained a match rate of 47.9%.These were overall rates. When Schumacher [1986] specifically studied colon cancer patients in Utah, comparing interview information on occupation before death with what later appeared on the death certificate, there was agreement in 63%. Misclassification was random. This difficulty is unfortunate, since random scanning of occupational designations in computerized registry systems has the potential for useful hypothesis-seeking and pilot studies (and, with proper caution for its limitations, can still be used for these purposes), particularly for occupational groups (as, non-union and small workplaces) for which it is difficult to assemble cohorts [Dubrow et al., 19871. Many years ago, Breslow and his colleagues [1954] explored this possibility in an original and perceptive survey, although they found that death certificate occupational designations were insecure for a variety of reasons. The converse has also been found to be true; death certificates may not be concordant with known cases in cancer registries. Vianna and his colleagues [ 19811 studied 288 patients with histologically verified malignant mesothelioma in the N.Y. State Cancer Registry. One hundred seven death certificates were obtained. Sixty-seven (62.6%)had well established asbestos occupations listed. When detailed interviews were conducted, the percentage rose to 77.4%. The use of broad occupational categories can lead to difficulties. Minder and Vader [ 19881 studied pleural mesothelioma in Switzerland 1979-1985. Death certificate occupations gave an unexpected focus on “furniture workers,” with 12 observed on DC with 4.4 expected, and it was believed that “a new high-risk group” was identified. Schuler and Ruttner [1989] soon pointed out that “occupational titles are not sufficient for proving the presence or absence of exposure. A detailed occupational history is essential,” especially in view of asbestos’ latency. In their pathology series, they had seen “furniture workers” who had worked in railway car construction and repair workshops with opportunity for asbestos exposure. Merler and Ricci [ 19891 provided similar experiences.
PRESENT INVESTIGATION
The foregoing situation is perhaps even more disappointing than it would appear, since it speaks to death certificate occupation findings in general terms. There is little information on specific diseases related to known occupational exposures or what might be expected in particular cohorts, especially over time. We have therefore investigated the question of death certificate occupational categorization in two quite different asbestos occupational groups, both in relation to specific disease outcomes (lung cancer, mesothelioma, asbestosis) and to occupational designations with both recent employment and after long periods of latency following cessation of exposure.
Inaccurate Occupational Categorization
495
MATERIALS AND METHODS
We have studied the mortality experience of two cohorts of asbestos-exposed workers. In each instance, the investigation was prospective, facilitating the acquisition of material related to the cause of death, so that not only was the cause of death as categorized on the death certificate at hand (DC) but ascertainment after evaluation of all available material was analyzed (best evidence [BE]) [Selikoff and Seidman, 19911.
The first cohort was composed of the entire membership of the Insulation Workers’ Union’ in the United States and Canada on January 1, 1967. On that day, there were 17,800 men on its rolls. The entire group has been followed since. Details of the methodology utilized in the investigation have been reported [Selikoff et al., 1979; Hammond et al., 19791. Briefly, surveillance of the Union’s membership is accomplished by the officials of the International Office of the IAHFIAW and of the 120 local unions in all parts of the United States and Canada. If a member dies, we are notified and a death certificate is provided by the union or, if unavailable, it is obtained from the appropriate State Health Department. Medical attendants (personal physicians, hospitals, extended care facilities) are contacted and clinical material, including x-rays, requested. This is often supplemented by information from the surviving spouse or next of kin, from whom listings of those who participated in the worker’s medical care (over time, not only in the final illness) are sought, with promise of confidentiality and assurance that the information is for research purposes only. At the same time, histopathological material is requested from pathology departments, coroners, and, nowadays, from private pathology groups. Not only are pertinent records asked for, but opportunity for review of histological material (slides, blocks for special stains) by our Pathology Unit. Responses from both clinical and pathology facilities and physicians have been excellent [Selikoff, 19901. From January 1, 1967, to December 3 1, 1986, a total of 4,95 1 men died and the causes of death were ascertained in two ways-death certificate categorization (DC) and best evidence (BE). Death rates by cause were computed, based upon 301,592.6 person-years of observation [Selikoff, 19901, with expected deaths based upon death rates of the U.S. National Center for Health Statistics 1967-1986 for white males. We also recorded the occupation as listed on the death certificate, in each case. It was considered useful to note the exact designations rather than try to compress them into numerical codes, which tend to be restrictive [Breslow et al., 19541. As will be seen below, this helps retain the rich diversity of worker experience, while still presenting the essential designation of occupational categories. The second cohort was composed of all workers (933) employed by an asbestos (amosite) products factory in New Jersey at any time from June 15, 1941, when the factory opened, to December 31, 1945. The factory closed in November, 1954. This cohort has also been followed since, utilizing the same general methodological approach as with the first cohort. However, after the factory closed, follow-up was undertaken (periodic surveillance of all survivors and their families) by staff of the Department of Epidemiology of the American Cancer Society. Details of this study have also been reported [Seidman et al., 1979, 19861. ‘International Association of Heat and Frost Insulators and Asbestos Workers (IAHFIAW), AFL-CIO, CLC.
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Selikoff
From 1941 to the end of 1990, there were 740 deaths among the 933 men in this cohort. Death certificates were obtained for each, causes of death ascertained (both DC and BC), and occupation as listed on the death certificates recorded. RESULTS In this investigation, we have been primarily concerned with two facets of the experiences of both cohorts: 1. accuracy of causes of death as categorized on the death certificates; and 2. occupations as listed on the death certificate; in particular whether they reflected, in greater or lesser degree, the known exposures to asbestos in each group.
The cohorts differed substantially in ways other than the nature of their asbestos work. The first-insulation workers-were long-term members of a tight-knit union, with roots going back to 1910 [Selikoff et al., 19651. During the 20-year period of our observation (1967-1986), this association continued and even when retirement or illness occurred, ties with the union continued with special membership status, access to pension and disability funds, as well as many personal ties with other members of their local unions forged over their working lifetimes. In the second cohort, on the other hand, when workers left the factory in New Jersey, they dispersed and either returned to pre-war trades or went into other jobs. They no longer maintained contact with each other, nor was there a union to which they continued to belong. Many had had but short-term employment-days, weeks, months, a few years-while few worked the entire 13 years until the plant closed [Seidman et al., 19861. Their asbestos employment might have left a continuing fiber burden in their lungs, with associated disease risk, but was, for many, an incident in their employmenthistories which often was obscured over subsequent decades, by the passage of time. The insulation workers, then, could be characterized as a currently employed group with workers aware of their history of asbestos exposure and the factory group as a previously exposed cohort, revisited after considerable passage of time, when asbestos exposure might not have been recollected by the worker, nor known to families or medical attendants. In summary, the problems we addressed focused on how recording of mortality experience differed with regard to a) accuracy of death certificate disease categories (which reflects medical care and diagnosis), and b) occupational designation on death certificates, particularly whether such designation gave information (or even some hint) of previous asbestos exposure. Insulation Workers We have recently reported [Selikoff and Seidman, 19911 on accuracy of death certificatediagnoses of lung cancer in the cohort being analyzed. To put it succinctly, there was a high degree of accuracy with relatively few false positives and false negatives. Findings are summarized in Table I. For this study, we elected to analyze the cohort’s mesothelioma experience; 458 deaths occurred of this disease, 1967-1986, including 173 ascertained deaths of pleural mesothelioma and 285 peritoneal.
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497
TABLE I. Lung Cancer Among Asbestos Insulation Workers in the US and Canada, 19674986 Death certificate (DC) Lung cancer Other neoplasms Asbestosis Other Total
Lung cancer ascertained (BE)
No.
No.
1,008 1,119 20 1 2,623
%9 92 9 98
4,951
1,168
%
96.1 8.2 4.5 3.7
Death certificate diagnoses were much less accurate than for lung cancer, with only 89 pleural and 92 peritoneal cancers appropriately categorized on the certificates (39.5%). A considerable variety of mesothelioma nomenclature was recorded, and has been reported [Selikoff and Seidman, 19921. This experience with mesothelioma on death certificates is by no means unusual; indeed, it seems to be the rule [Connelly et al., 1987; Newhouse et al., 19851. Insofar as occupational designations on death certificates are concerned, these were for the most part accurate and gave clear evidence of asbestos exposure. However, semantic variability was frequent. For this reason, it may be useful to list the occupations as they appeared on the death certificates of the 458 insulators who died of mesothelioma (Table II). We examined whether occupation on death certificate varied substantially when disease categories did not indicate mesothelioma (Table III). It did not appear to. Asbestos Factory Workers From 1941 to 1990, a total of 740 of the 933 men employed during 1941-1945 died, 429 in 1965 or later (58%), with, thus, at least 20 years from onset of their work. Six hundred eighteen (83.5%) died after the plant closed in November 1954. Very few had transferred to other units of the same company or had gone to other asbestos exposure jobs [Seidman et al., 19861. Thus, when death occurred during 1955-1990, the individuals concerned had no asbestos employment facility to which they were attached and certainly no necessary reason for anyone to relate what had occurred to exposures decades before. Moreover, unlike the insulators, who had become well aware of their asbestos hazards after 1964 [Selikoff et al., 19641, most of the factory workers had not been indoctrinated about asbestos risks during their periods of employment (1941-1954). We have studied 198 consecutive deaths in three asbestos-disease categories in this population-lung cancer (136), mesothelioma (17), asbestosis (45)-as ascertained by best evidence after review of all available material. Our analyses, as with the insulation workers, focused on two aspects: first, accuracy of medical diagnoses as reflected in death certificate categories and, second, occupational designations as recorded. Death certificate diagnoses for these asbestos-associated diseases were relatively accurate, when compared with ascertained diagnoses as achieved by best evidence evaluation, and compared well with those recorded for the insulation workers (Table IV). These results speak highly for the acumen of the medical attendants of
498
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TABLE 11. Occupational Designations on k t b Certificates of 458 Asbestos Insulation Workers Who Died of Pleural and Peritoneal Mesotbelioma, 1967-1986 1. Asbestos workep-162 (35.4%) Asbestos-3 Asbestos applicator-1 Asbestos business agent-] Asbestos insulator-9 Asbestos laborer-1 Abbestos lagger-I Asbestos mechanic-3 Asbestos worker-141 Insulation asbestos worker-2 2. Insulator-1 16b(25.3%) Commercial and industrial insulatiow-1 Commercial insulator-] Heat and frost insulator-5 Heat insulator-] Industrial insulatio~i-4 Insulatior+3 Insulation engineer-3 Insulation mechanic-4 Insulation worker-] Insulator-82 Pipe insulator-1 1 3. Pipe coverer-36 (7.9%) Asbestos coverer-] Asbestos pipe coverer-2 Pipe coverer-32 Pipe cover insulator-1 4. Installer-20 (4.4%) Asbestos installer-8 Heat and frost installer-1 Installation-2 Installer-2 Insulation installer-7 5 . Construction-43‘
(9.4%) Constructio*4 Construction foreman-1 Construction superintendent-2 Construction worker-2 Employee, worker-I4 Laborer-] Leading man-l Maintenance-1 Mechanic-I0
5 . ConstructiodContinued)
pipe cutter-3 Pipe fitter-3 Steamfitter-1 6. Executive positions 57d (12.4%) Administrative assistant-1 Business agent-1 Contractor-5 Employer-3 Engineer-8 Employer-3 Estimator-2 Executivs-I Field superintendent4 Foreman-3 Labor representativc+l Manager-4 Office floater-] Office manager-2 Owner-1 hner-Operati011-3 Partner-] Resident-] Sales engineer-] secretary-treasurer-1 Supervisor-superintendent-7 Union official4 Vice president-4 7. Other occupations--13d (2.8%) City manager-] Fmr-1 FinnUl-1 Greenhouse-1
Marina manager-] Marina owner-I Merchant-] Minister-1 Quartermart1 Real estate-] Self-employebl Truck driver-] Upholsterer- I
8. Not recorded-Y (1.5%) 9. Workplace or union local-4
(0.9%)
Curiously, the word “lagger” appeared only once, unlike British practice. The emphasis on commercial and industrial work is noteworthy. The men in this union are employed in commercial and industrial rather than residential insulation (housing projects, powerhouses, industrial plants, refineries, energy production, nuclear facilities, chemical facilities, etc.). The word “mechanic” is also significant-it designates a recognized high degree of experience, skill and competence. It does not categorize the individual as a mechanic in the automobile-mechanic sense of the term.There is a similar connotation to the word “engineer,” which is not meant to indicate an academically trained individual. It is worth noting, too. the heat and frost labels-this union’s jurisdiction control. not insulation for sound, decorative purposes, or in the building hades covers insulation for temperafireproofmg. ‘These men worked in the construction industry, of course, so that this category is not entirely inappropriate. It is insufficiently precise, however. A few cases (steamfitter, pipe fitter) may have either been in e m r or referring to alternate jobs the men had taken. dMen began work as youngsters many years before. During the years of latency [Selikoff et al., 19801 some achieved either leadership positions in their unions or joined insulation f m in executive positions. It is by no means unusual for an employer, owner of a small f m , to retain his union membership. While this might make computers stumble when seeking meaningful occupational categories to test against disease outcome data, it accurately reflects industrial conditions in the building trades. ‘Men may leave insulation work for a variety of reasons (sometimes, health) and, infrequently, their last occupation is not recorded. a
Inaccurate Occupational Categorization
499
TABLE 111. Asbestos Work Designated in Occupational Categories in Deaths From Mesothelioma Among Insulation Workers With Other Disease Diagnoses on Certificate Death certificate
Asbestos work
Construction
Executive
1-4 68.2%
5 11.8%
6 14.1%
7-9 5.9%
5 11 4
5 16 3
3 5 2
~
Table I1 groups Lung cancer Other neoplasms Non-neoplastic diseases
All other ~~
13 (50%)
90 (73.8%) 13 (59.1%)
~
TABLE IV. Accuracy of Death Certificate Classification of Causes of Death Among Asbestos Factory Workers, 1941-1990 Classification on death certificate Cause of death A. Lung cancer (136) Lung cancer Other neoplasms Asbestosis Other diseases B. Mesothelioma (17) Mesothelioma Other neoplasms Asbestosis Other diseases C. Asbestosis (45) Asbestosis Lung cancerhesothelioma Other neoplasms Other diseases
No.
%
112 9 4 11
82.4
10 5 0 2
58.8
22 0
48.9
0 23
these workers (in New Jersey and elsewhere in the United States, where many had gone). The physicians and pathologists did not have the advantage of being alerted to asbestos-related risk by virtue of current asbestos employment. One mesothelioma death occurred in 1951, the next in 1966 (24 years latency) and the rest from 1970 to 1988 (29 to 47 years latency). The data for asbestosis were similar. There were only five deaths from this disease in 1954 or before. The 39 others occurred during 1956-1989, folbwing 15-48 years latency. Yet this did not prevent a high proportion (48.9%) from having a correct diagnosis recorded on the death certificate (Table V). There was thus not great difference in accuracy of death certificate diagnoses between the insulators (1967-1986) and the asbestos factory workers (1941-1990) despite the considerable variation in the nature of support systems of the two groups insofar as asbestos information of the workers was concerned. Diagnosis depended upon accuracy of medical evaluation (as translated onto death certificates). There was considerable competence in diagnosis of diseases for workers in both cohorts. It was quite another matter when we came to occupational designation on the
500
Selikoff TABLE V. Occupational Designations on Depth CeMcates in 198 Consecutive Deaths of Lung Cancer, Mesothelioma, and Asbestosis in Former Asbestos Factory Workers Death certificate occupation Antique dealer Mist Baker Bartender Bookkeeper Bus driver Carpenter Caterer Chefkook Chemical mixer Chemist Clerk Confectioner Contractor Custodian Deck man Driver Dyeddyer’s helper Electrician Electronic technician Engineer Executive Finisher Foreman Grinder Grit blaster Grower Guard Hatter Helper Ice maker Inspector Janitor Laborer Machine operator Machinist Maintenance Mason Mechanic Mill worker Millwright Miner Owner Packer Painter Plastics Plumber Porter Postman Press operator
Cause of death Lung cancer
Mesothelioma
Asbestosis
0 0
I 0 0 0 0 0 0 0 0
0 1 0 1 1 0 1 0 2
0 1 1
0
1
0 0 1
3 1 4 1 0 1 1 1 2 1 1 4
2 1
2 1 1
2 1 1
0 1 0 0 1 1 2 9 2 6 13 4 5 1 0 1 2 1 5 1 1 1 1 1
0 0 2 0 0 0 0 0 0 0 0 0 0 0 0 1
0 0 0 0 0 0 0 1
0 0 1
0 0 0
2 0 0 0 0 0 0 0
0
0 0 2 1
0 0 3 0 1 0
0 1 1 0 0 1 0 1 1
0 0 0 7 0 1 3 0 1 1 0 0 1 0 1 0
0 0 0 0
Total 1 1 1 1 1 1 4 1 6 1 1 2 1
3 5 1 1
7 2 2 2 1 2 3 1 1 1
2 1 1 1 1
2 16 2 8 16 4 7 2 1 1 5 1 6 1 1 1 1 1 (continued)
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501
TABLE V. Occupational Designations on Death Certlllcates in 198 Consecutive Deaths of Lung Cancer, Mesothelioma, and Asbestosis in Former Asbestos Factorv Workers IContinued) Death certificate occupation Printer Produce manager Proprietor Real estate Restaurant Salesman Security Service man Sheetmetal Shipyard worker Sodder Stationary fireman Steward Store room Super Supervisor Tavern owner Textile Truck driver Typesetter Upholsterer Waiter Warper Watchman Weaver Welder Not available Expert asbestosa President asbestos companyb Total
Cause of death Lung cancer Mesothelioma Asbestosis Total 1 1 1 0 1 2 3 1 1 1 1 2 1 1 1 1 0 2 5 1 1 1 0 1 8 0 7
1 0 0 1 0 1 0 0 0 0 0 0 0 0 0 0 0 1 1 0 0 0 0 0 0 0 0
0 0 0 0 0 0 1 0 0 0 0 1 0 0 0 2 1 1 0 0 0 0 1 1 1 1 0
1 1 1 1 2 9 1 7
0 0
1 1
0 0
1 1
136
17
45
198
1 1 1 1 1 3 4 1 1 1 1 3 1 1 1 3 1 4
6
This man was the chief engineer of the company. He formulated its principal product from 1934 to 1936. He died in 1951 of mesothelioma, 10 years after the New Jersey company began operations, but he had had asbestos exposure in other plants of the company dating back several decades [Bettes, 19711 and extensive experience in the asbestos industry [Wild, 19211. %e death certificate properly identified him as the president of an asbestos company at the time of d e a t h 4 u t it was not the company being studied. He had been plant manager there until he left to go to another city, to head the U.S. affiliate of a British asbestos company. He died in 1970 of a peritoneal mesothelioma, 29 years after beginning work in the N.J. plant, but had had prior asbestos experience before his work there.
death certificates. For the 198 deaths of lung cancer, mesothelioma, and asbestosis among the factory workers, there was virtually no indication of occupational asbestos exposure (Table V). There were no other occupational designations of asbestos exposure. In general, industries as recorded on the death certificates were consistent with occupations as
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Selikoff
TABLE VI. Deaths with Potential Asbestm Exposure DC cause of death
Occupation
Industry
Asbestosis Lung abscess Pulmonary fibrosis Asbestosis
Laborer Finisher Laborer Millwright
[The N.J.asbestos company] Asbestos company [The N.J.asbestos company] Asbestos manufacturing
categorized. There were four deaths, however, in which “industry” gave evidence of potential asbestos exposure (Table VI). Thus, altogether, six of 198 deaths (3.0%) had some evidence on the death certificate that asbestos was involved (ascertained on best evidence as 1 lung cancer, 2 mesothelioma, 3 asbestosis). We separately analyzed the 16 men in this group who had worked 10 or more years in the plant. Occupations on death certificates were marginally more accurate (Table VII). CONCLUSIONS We have compared death certificate classifications in two cohorts of asbestosexposed workers-asbestos insulation workers ( 1967-1986) and asbestos factory workers (1941-1990). Apart from both having had significant asbestos exposure, the two groups were dissimilar in many important ways at the times when deaths occurred (Table VIII). We were interested in whether these differences would be reflected in greater or lesser accuracy in death certificate categorizationof causes of death and occupations. We anticipated, a priori, that the latter would show little evidence of asbestos work for the factory group, since the factory had closed in 1954 and the men had gone on to other employment. With the tendency to list last occupation on death certificates, prior asbestos work would not be expected to be recorded on death certificates. We also anticipated that medical diagnosis might suffer to some extent in the latter group since the patients and their families would not necessarily have alerted their medical attendants to the possibility of previous asbestos exposure as a potential etiological factor. Neither, of course, would be the case for the long-term asbestos workers in the insulation cohort, who had current or recent exposure, and who lived in an asbestos worker culture with personal contacts and ample information about asbestos hazards. As matters turned out, we were partly right and partly wrong. Correct-with regard to occupations on death certificates-in that asbestos insulation work (with many semantic variations) was found on three-quarters of the insulators’ death certificates but asbestos work in any form was rare on the factory workers’ certificates, even for deaths attributed to mesothelioma and asbestosis. It was as if their previous asbestos work (with much asbestos-associated disease) was not to be retrieved or recalled from a nebulous past, superceded by many other kinds of employment. Parenthetically, the blue collar workers of the factory tended to remain in blue collar trades, and their asbestos-associated disease would have been recorded in these new trades, with prior exposure unrecognized in our computer and registry-driven data analyses. But this effect of latency is hardly new.
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TABLE VII. Deaths Among Workers With >10 Years in Same Workplace DC cause of death Occupation Industry Lung cancer Lung cancer Lung cancer Lung cancer Lung abscess Asbestosis Asbestosis Lung cancer Lung cancer Peritoneal mesothelioma Peritoneal mesothelioma Asbestosis Asbestosis Heart disease Asbestosis Asbestosis
Maintenance Laborer Watchman Stationary fireman Finisher Maintenance Paint company Maintenance Engineer Expert asbestos President asb. co. Plumber Tavern owner Stationary fireman Superintendent Millwright
Paint company Not recorded Printing company Hospital Asbestos company Paint company Not recorded Machinery Not recorded [Name of the asbestos company] Not recorded Retired Tavern Machine shop Magnetic products Asbestos manufacturing
TABLE VIII. Comparison of Asbestos Insulation and Factory Workers
Current or recent asbestos work Effective support system with knowledge of asbestos Indoctrination concerning asbestos-associated disease Personal contact with other asbestos workers
Insulation workers
Factory workers
Yes Yes Yes Yes
No No No No
We were pleasantly surprised to find our second concern unwarranted. Disease classification for both groups was comparable. The medical care offered the factory workers years after their last asbestos work was very much as appropriate as that of the insulation workers, in the same disease (asbestos-associated)categories. Medical and pathological diagnosis was independent of patient and family opportunity for awareness of asbestos’s potential for disease. These observations have relevance for public health approaches to occupational disease identification and quantitative evaluation based on death certificate registrations. Disease categories, at least for asbestos, tend to be accurate. Attempts to identify groups at risk by sorting occupational categories can give variable resultsgood for those with current exposures, much less satisfactory for those with long-past occupational exposures. ACKNOWLEDGMENTS I am grateful to my associate, Janet S. Kaffenburgh, for her exigent attention to the compilation of these data since the inception of this prospective study. Mrs. Kaffenburgh died on June 25, 1992. Support for statistical analysis from NIOSH-ALOSH is gratefully acknowledged. REFERENCES Bettes JA Jr (1971): Chapter V. Keasbey & Mattison Company. In “The History of the Asbestos Textile Industry in the United States.” Asbestos, February pp 2-12.
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Breslow L, Hoaglin L, Rasmussen G, Abrams HK (1954):Occupations and cigarette smoking as factors in lung cancer. Am J Public Health M171-181. Coggon D, Pippard EC, Acheson ED (1985):Accuracy of occupational histories obtained from wives. Br J Ind Med 42563-564. Connelly RR, Spirtas R, Myers MH, Percy CL, Fraumeni JF (1987): Demographic patterns for mesothelioma in the United States. JNCI 78:1053-1060. Dubrow R, Sestito JP, Lalich NR, Burnett CA, Salg JA (1987): Death certificate-based occupational mortality surveillance in the United States. Am J Ind Med 11:329-342. Hammond EC, Selikoff IJ, Seidman H (1979): Asbestos exposure, cigarette smoking and death rates. Ann NY Acad Sci 330:473-490. Harrington JM (1984): Occupational mortality. Scand J Work Environ Health 10347-352. Kaminski R, Bmkert J, Sestito J, Frazier T (1981): Occupational information on death certificates. A survey of state practices. Am J Public Health 71525426. Lilienfeld DE (1988): Editorial. Occupation on the death certificate: To use or not to use, that is the question. Am J Ind Med 1 4 119-120. Mayers MR (1952): Industrial cancer of the lungs. N.Y.S. Department of Labor Monthly Review 31:21-24, 27-28. Merler E, Ricci P (1989): Letters to the Editor. Re: Malignant pleural mesothelioma among Swiss furniture workers: A new high-risk group, by CE Minder, JP Vader. Scand J Work Environ Health 15:439-440. Minder CE, Vader JP (1988): Malignant pleural mesothelioma among Swiss furniture workers. A new high-risk group. Scand J Work Environ Health 14252-256. Newhouse ML, Berry G, Wagner JC (1985): Mortality of factory workers in East London 1933-80. Br J Ind Med 42:4-11. Schade WJ, Swanson GM (1988): Comparison of death certificate occupation and industry data with lifetime occupational histories obtained by interview: Variations in the accuracy of death certificate entries. Am J Ind Med 14:121-136. Schuler G, Ruttner JR (1989):Letters to the editor. Mesotheliomaamong Swiss furniture workers. Scand J Work Environ Health 153440442. Schumacher MC (1986):Comparison of occupation and industry information from death certificates and interviews. Am J Public Health 76:635-637. Seidman H, Selikoff IJ, Hammond EC (1979): Short-term asbestos work and long-term observation. Ann NY Acad Sci 330:61-89. Seidman H, Selikoff IJ, Gelb SK (1986): Mortality experience of amosite asbestos factory workers: Dose-responserelationships 5 to 40 years after onset of short-term work exposure. Am J Ind Med 10479-5 14. Selikoff IJ (1990): Historical developments and perspectives in inorganic fiber toxicity in man. Env Health Persp 88:269-276. Selikoff U, Churg J, Hammond EC (1964): Asbestos exposure and neoplasia. JAMA 188:22-26. Selikoff IJ, Churg J, Hammond EC (1%5):The occurrence of asbestosis among insulation workers in the United States. Ann NY Acad Sci 132:139-155. Selikoff IJ, Hammond EC, Seidman H (1979): Mortality experience of insulation workers in the United States and Canada. Ann NY Acad Sci 330:91-116. Selikoff IJ, Hammond EC, Seidman H (1980): Latency of asbestos disease among insulation workers in the United States and Canada. Cancer 46:2736-2740. Selikoff IJ, Seidman H (1991): Asbestos-associateddeaths among insulation workers in the United States and Canada, 1967-1987. Ann NY Acad Sci 643:l-14. Selikoff IJ, Seidman H (1992): Use of death Certificates in epidemiological studies, including occupational hazards. Variations in discordance of different asbestos-associated disease on best evidence ascertainment. Am J Ind Med 22:481-492. Vianna NJ, Maslowsky J, Roberts S, Spellman G, Patton RE3 (1981): Malignant mesothelioma, epidemiologic patterns in New York State. N Y S J Med, April 735-738. Wild RLR (1921): Asbestos mattress covering. Asbestos 3 5 .
Death Certificates in Epidemiological Studies, Including Occupational Hazards: Inaccuracies in Occupational Categories Irving J. Selikoff", MD
We compared death certificates for asbestos-associated diseases (mesothelioma, lung cancer, asbestosis) in two asbestos workers' cohorts. One (insulation workers) had current or recent employment and a strong, continuing union support system which gave them much information about the effects of asbestos exposure. The second cohort, asbestos factory workers, had no such advantage. The factory had closed almost 30 years before, and its workers had dispersed into many areas of the state and nation. Accuracy of medical diagnosis was comparable in the two groups, but occupational listings were not. Three-quarters of the insulators' death certificates told of asbestos work, while virtually none of the factory workers' certificates provided such information, even for deaths of mesothelioma and asbestosis. The data indicate that disease categories, based on medical and pathological diagnoses, at least for asbestos-associated disease, tend to be accurate. Attempts to identify groups at risk by sorting occupational categories can give variable results, good for those with current exposures, much less satisfactory for those with long-past occupational exposures. 0 1992 Wiley-Liss, Inc. Key words: death certificates, occupational categories, asbestos-associated disease
INTRODUCTION
There have long been misgivings about the use of occupations as listed on death certificates in view of known inaccuracies and incompleteness [Lilienfeld, 19881. This has been true even for countries such as the United States and Great Britain, with well-established vital statistics agencies. In the former, for example, NIOSH in 1979 investigated the extent to which state and local vital registration offices coded and stored occupational information quoted on death certificates. Eleven states routinely coded occupation and six did so on a limited basis [Kaminski et al., 19811. Harrington [1984] reviewed British practices and found major flaws. A particularly widespread source of error has been recording the last occupation
*Dr. Selikoff died on May 20, 1992. Mount Sinai School of Medicine of The City University of New York, New York, NY. Address reprint requests to Dr. Stephen Levin, Mount Sinai School of Medicine, One Gustave L. Levy Place, Box 1059, New York, NY 10029-6574. Accepted for publication January 8, 1992. 0 1992 Wiley-Liss, Inc.
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[Harrington, 1984; Dubrow et al., 19871. This is particularly disadvantageous in occupational studies, in which, as Mayers [ 19521 noted more than four decades ago, occupational cancer is “more apt to have been caused by some previous occupational exposure” years before. This has been documented and emphasized repeatedly [Selikoff et al., 19801. Nor can one be at all confident that even the (last) occupation is necessarily accurate. Coggon et al. [1985] studied 39 middle-aged couples. Of 122 occupations detailed by the husbands, only 62 were accurately reported by their wives. Schade and Swanson [ 19881 compared interview lifetime work histories with death certificate entries and obtained a match rate of 47.9%.These were overall rates. When Schumacher [1986] specifically studied colon cancer patients in Utah, comparing interview information on occupation before death with what later appeared on the death certificate, there was agreement in 63%. Misclassification was random. This difficulty is unfortunate, since random scanning of occupational designations in computerized registry systems has the potential for useful hypothesis-seeking and pilot studies (and, with proper caution for its limitations, can still be used for these purposes), particularly for occupational groups (as, non-union and small workplaces) for which it is difficult to assemble cohorts [Dubrow et al., 19871. Many years ago, Breslow and his colleagues [1954] explored this possibility in an original and perceptive survey, although they found that death certificate occupational designations were insecure for a variety of reasons. The converse has also been found to be true; death certificates may not be concordant with known cases in cancer registries. Vianna and his colleagues [ 19811 studied 288 patients with histologically verified malignant mesothelioma in the N.Y. State Cancer Registry. One hundred seven death certificates were obtained. Sixty-seven (62.6%)had well established asbestos occupations listed. When detailed interviews were conducted, the percentage rose to 77.4%. The use of broad occupational categories can lead to difficulties. Minder and Vader [ 19881 studied pleural mesothelioma in Switzerland 1979-1985. Death certificate occupations gave an unexpected focus on “furniture workers,” with 12 observed on DC with 4.4 expected, and it was believed that “a new high-risk group” was identified. Schuler and Ruttner [1989] soon pointed out that “occupational titles are not sufficient for proving the presence or absence of exposure. A detailed occupational history is essential,” especially in view of asbestos’ latency. In their pathology series, they had seen “furniture workers” who had worked in railway car construction and repair workshops with opportunity for asbestos exposure. Merler and Ricci [ 19891 provided similar experiences.
PRESENT INVESTIGATION
The foregoing situation is perhaps even more disappointing than it would appear, since it speaks to death certificate occupation findings in general terms. There is little information on specific diseases related to known occupational exposures or what might be expected in particular cohorts, especially over time. We have therefore investigated the question of death certificate occupational categorization in two quite different asbestos occupational groups, both in relation to specific disease outcomes (lung cancer, mesothelioma, asbestosis) and to occupational designations with both recent employment and after long periods of latency following cessation of exposure.
Inaccurate Occupational Categorization
495
MATERIALS AND METHODS
We have studied the mortality experience of two cohorts of asbestos-exposed workers. In each instance, the investigation was prospective, facilitating the acquisition of material related to the cause of death, so that not only was the cause of death as categorized on the death certificate at hand (DC) but ascertainment after evaluation of all available material was analyzed (best evidence [BE]) [Selikoff and Seidman, 19911.
The first cohort was composed of the entire membership of the Insulation Workers’ Union’ in the United States and Canada on January 1, 1967. On that day, there were 17,800 men on its rolls. The entire group has been followed since. Details of the methodology utilized in the investigation have been reported [Selikoff et al., 1979; Hammond et al., 19791. Briefly, surveillance of the Union’s membership is accomplished by the officials of the International Office of the IAHFIAW and of the 120 local unions in all parts of the United States and Canada. If a member dies, we are notified and a death certificate is provided by the union or, if unavailable, it is obtained from the appropriate State Health Department. Medical attendants (personal physicians, hospitals, extended care facilities) are contacted and clinical material, including x-rays, requested. This is often supplemented by information from the surviving spouse or next of kin, from whom listings of those who participated in the worker’s medical care (over time, not only in the final illness) are sought, with promise of confidentiality and assurance that the information is for research purposes only. At the same time, histopathological material is requested from pathology departments, coroners, and, nowadays, from private pathology groups. Not only are pertinent records asked for, but opportunity for review of histological material (slides, blocks for special stains) by our Pathology Unit. Responses from both clinical and pathology facilities and physicians have been excellent [Selikoff, 19901. From January 1, 1967, to December 3 1, 1986, a total of 4,95 1 men died and the causes of death were ascertained in two ways-death certificate categorization (DC) and best evidence (BE). Death rates by cause were computed, based upon 301,592.6 person-years of observation [Selikoff, 19901, with expected deaths based upon death rates of the U.S. National Center for Health Statistics 1967-1986 for white males. We also recorded the occupation as listed on the death certificate, in each case. It was considered useful to note the exact designations rather than try to compress them into numerical codes, which tend to be restrictive [Breslow et al., 19541. As will be seen below, this helps retain the rich diversity of worker experience, while still presenting the essential designation of occupational categories. The second cohort was composed of all workers (933) employed by an asbestos (amosite) products factory in New Jersey at any time from June 15, 1941, when the factory opened, to December 31, 1945. The factory closed in November, 1954. This cohort has also been followed since, utilizing the same general methodological approach as with the first cohort. However, after the factory closed, follow-up was undertaken (periodic surveillance of all survivors and their families) by staff of the Department of Epidemiology of the American Cancer Society. Details of this study have also been reported [Seidman et al., 1979, 19861. ‘International Association of Heat and Frost Insulators and Asbestos Workers (IAHFIAW), AFL-CIO, CLC.
4%
Selikoff
From 1941 to the end of 1990, there were 740 deaths among the 933 men in this cohort. Death certificates were obtained for each, causes of death ascertained (both DC and BC), and occupation as listed on the death certificates recorded. RESULTS In this investigation, we have been primarily concerned with two facets of the experiences of both cohorts: 1. accuracy of causes of death as categorized on the death certificates; and 2. occupations as listed on the death certificate; in particular whether they reflected, in greater or lesser degree, the known exposures to asbestos in each group.
The cohorts differed substantially in ways other than the nature of their asbestos work. The first-insulation workers-were long-term members of a tight-knit union, with roots going back to 1910 [Selikoff et al., 19651. During the 20-year period of our observation (1967-1986), this association continued and even when retirement or illness occurred, ties with the union continued with special membership status, access to pension and disability funds, as well as many personal ties with other members of their local unions forged over their working lifetimes. In the second cohort, on the other hand, when workers left the factory in New Jersey, they dispersed and either returned to pre-war trades or went into other jobs. They no longer maintained contact with each other, nor was there a union to which they continued to belong. Many had had but short-term employment-days, weeks, months, a few years-while few worked the entire 13 years until the plant closed [Seidman et al., 19861. Their asbestos employment might have left a continuing fiber burden in their lungs, with associated disease risk, but was, for many, an incident in their employmenthistories which often was obscured over subsequent decades, by the passage of time. The insulation workers, then, could be characterized as a currently employed group with workers aware of their history of asbestos exposure and the factory group as a previously exposed cohort, revisited after considerable passage of time, when asbestos exposure might not have been recollected by the worker, nor known to families or medical attendants. In summary, the problems we addressed focused on how recording of mortality experience differed with regard to a) accuracy of death certificate disease categories (which reflects medical care and diagnosis), and b) occupational designation on death certificates, particularly whether such designation gave information (or even some hint) of previous asbestos exposure. Insulation Workers We have recently reported [Selikoff and Seidman, 19911 on accuracy of death certificatediagnoses of lung cancer in the cohort being analyzed. To put it succinctly, there was a high degree of accuracy with relatively few false positives and false negatives. Findings are summarized in Table I. For this study, we elected to analyze the cohort’s mesothelioma experience; 458 deaths occurred of this disease, 1967-1986, including 173 ascertained deaths of pleural mesothelioma and 285 peritoneal.
Inaccurate Occupational Categorization
497
TABLE I. Lung Cancer Among Asbestos Insulation Workers in the US and Canada, 19674986 Death certificate (DC) Lung cancer Other neoplasms Asbestosis Other Total
Lung cancer ascertained (BE)
No.
No.
1,008 1,119 20 1 2,623
%9 92 9 98
4,951
1,168
%
96.1 8.2 4.5 3.7
Death certificate diagnoses were much less accurate than for lung cancer, with only 89 pleural and 92 peritoneal cancers appropriately categorized on the certificates (39.5%). A considerable variety of mesothelioma nomenclature was recorded, and has been reported [Selikoff and Seidman, 19921. This experience with mesothelioma on death certificates is by no means unusual; indeed, it seems to be the rule [Connelly et al., 1987; Newhouse et al., 19851. Insofar as occupational designations on death certificates are concerned, these were for the most part accurate and gave clear evidence of asbestos exposure. However, semantic variability was frequent. For this reason, it may be useful to list the occupations as they appeared on the death certificates of the 458 insulators who died of mesothelioma (Table II). We examined whether occupation on death certificate varied substantially when disease categories did not indicate mesothelioma (Table III). It did not appear to. Asbestos Factory Workers From 1941 to 1990, a total of 740 of the 933 men employed during 1941-1945 died, 429 in 1965 or later (58%), with, thus, at least 20 years from onset of their work. Six hundred eighteen (83.5%) died after the plant closed in November 1954. Very few had transferred to other units of the same company or had gone to other asbestos exposure jobs [Seidman et al., 19861. Thus, when death occurred during 1955-1990, the individuals concerned had no asbestos employment facility to which they were attached and certainly no necessary reason for anyone to relate what had occurred to exposures decades before. Moreover, unlike the insulators, who had become well aware of their asbestos hazards after 1964 [Selikoff et al., 19641, most of the factory workers had not been indoctrinated about asbestos risks during their periods of employment (1941-1954). We have studied 198 consecutive deaths in three asbestos-disease categories in this population-lung cancer (136), mesothelioma (17), asbestosis (45)-as ascertained by best evidence after review of all available material. Our analyses, as with the insulation workers, focused on two aspects: first, accuracy of medical diagnoses as reflected in death certificate categories and, second, occupational designations as recorded. Death certificate diagnoses for these asbestos-associated diseases were relatively accurate, when compared with ascertained diagnoses as achieved by best evidence evaluation, and compared well with those recorded for the insulation workers (Table IV). These results speak highly for the acumen of the medical attendants of
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TABLE 11. Occupational Designations on k t b Certificates of 458 Asbestos Insulation Workers Who Died of Pleural and Peritoneal Mesotbelioma, 1967-1986 1. Asbestos workep-162 (35.4%) Asbestos-3 Asbestos applicator-1 Asbestos business agent-] Asbestos insulator-9 Asbestos laborer-1 Abbestos lagger-I Asbestos mechanic-3 Asbestos worker-141 Insulation asbestos worker-2 2. Insulator-1 16b(25.3%) Commercial and industrial insulatiow-1 Commercial insulator-] Heat and frost insulator-5 Heat insulator-] Industrial insulatio~i-4 Insulatior+3 Insulation engineer-3 Insulation mechanic-4 Insulation worker-] Insulator-82 Pipe insulator-1 1 3. Pipe coverer-36 (7.9%) Asbestos coverer-] Asbestos pipe coverer-2 Pipe coverer-32 Pipe cover insulator-1 4. Installer-20 (4.4%) Asbestos installer-8 Heat and frost installer-1 Installation-2 Installer-2 Insulation installer-7 5 . Construction-43‘
(9.4%) Constructio*4 Construction foreman-1 Construction superintendent-2 Construction worker-2 Employee, worker-I4 Laborer-] Leading man-l Maintenance-1 Mechanic-I0
5 . ConstructiodContinued)
pipe cutter-3 Pipe fitter-3 Steamfitter-1 6. Executive positions 57d (12.4%) Administrative assistant-1 Business agent-1 Contractor-5 Employer-3 Engineer-8 Employer-3 Estimator-2 Executivs-I Field superintendent4 Foreman-3 Labor representativc+l Manager-4 Office floater-] Office manager-2 Owner-1 hner-Operati011-3 Partner-] Resident-] Sales engineer-] secretary-treasurer-1 Supervisor-superintendent-7 Union official4 Vice president-4 7. Other occupations--13d (2.8%) City manager-] Fmr-1 FinnUl-1 Greenhouse-1
Marina manager-] Marina owner-I Merchant-] Minister-1 Quartermart1 Real estate-] Self-employebl Truck driver-] Upholsterer- I
8. Not recorded-Y (1.5%) 9. Workplace or union local-4
(0.9%)
Curiously, the word “lagger” appeared only once, unlike British practice. The emphasis on commercial and industrial work is noteworthy. The men in this union are employed in commercial and industrial rather than residential insulation (housing projects, powerhouses, industrial plants, refineries, energy production, nuclear facilities, chemical facilities, etc.). The word “mechanic” is also significant-it designates a recognized high degree of experience, skill and competence. It does not categorize the individual as a mechanic in the automobile-mechanic sense of the term.There is a similar connotation to the word “engineer,” which is not meant to indicate an academically trained individual. It is worth noting, too. the heat and frost labels-this union’s jurisdiction control. not insulation for sound, decorative purposes, or in the building hades covers insulation for temperafireproofmg. ‘These men worked in the construction industry, of course, so that this category is not entirely inappropriate. It is insufficiently precise, however. A few cases (steamfitter, pipe fitter) may have either been in e m r or referring to alternate jobs the men had taken. dMen began work as youngsters many years before. During the years of latency [Selikoff et al., 19801 some achieved either leadership positions in their unions or joined insulation f m in executive positions. It is by no means unusual for an employer, owner of a small f m , to retain his union membership. While this might make computers stumble when seeking meaningful occupational categories to test against disease outcome data, it accurately reflects industrial conditions in the building trades. ‘Men may leave insulation work for a variety of reasons (sometimes, health) and, infrequently, their last occupation is not recorded. a
Inaccurate Occupational Categorization
499
TABLE 111. Asbestos Work Designated in Occupational Categories in Deaths From Mesothelioma Among Insulation Workers With Other Disease Diagnoses on Certificate Death certificate
Asbestos work
Construction
Executive
1-4 68.2%
5 11.8%
6 14.1%
7-9 5.9%
5 11 4
5 16 3
3 5 2
~
Table I1 groups Lung cancer Other neoplasms Non-neoplastic diseases
All other ~~
13 (50%)
90 (73.8%) 13 (59.1%)
~
TABLE IV. Accuracy of Death Certificate Classification of Causes of Death Among Asbestos Factory Workers, 1941-1990 Classification on death certificate Cause of death A. Lung cancer (136) Lung cancer Other neoplasms Asbestosis Other diseases B. Mesothelioma (17) Mesothelioma Other neoplasms Asbestosis Other diseases C. Asbestosis (45) Asbestosis Lung cancerhesothelioma Other neoplasms Other diseases
No.
%
112 9 4 11
82.4
10 5 0 2
58.8
22 0
48.9
0 23
these workers (in New Jersey and elsewhere in the United States, where many had gone). The physicians and pathologists did not have the advantage of being alerted to asbestos-related risk by virtue of current asbestos employment. One mesothelioma death occurred in 1951, the next in 1966 (24 years latency) and the rest from 1970 to 1988 (29 to 47 years latency). The data for asbestosis were similar. There were only five deaths from this disease in 1954 or before. The 39 others occurred during 1956-1989, folbwing 15-48 years latency. Yet this did not prevent a high proportion (48.9%) from having a correct diagnosis recorded on the death certificate (Table V). There was thus not great difference in accuracy of death certificate diagnoses between the insulators (1967-1986) and the asbestos factory workers (1941-1990) despite the considerable variation in the nature of support systems of the two groups insofar as asbestos information of the workers was concerned. Diagnosis depended upon accuracy of medical evaluation (as translated onto death certificates). There was considerable competence in diagnosis of diseases for workers in both cohorts. It was quite another matter when we came to occupational designation on the
500
Selikoff TABLE V. Occupational Designations on Depth CeMcates in 198 Consecutive Deaths of Lung Cancer, Mesothelioma, and Asbestosis in Former Asbestos Factory Workers Death certificate occupation Antique dealer Mist Baker Bartender Bookkeeper Bus driver Carpenter Caterer Chefkook Chemical mixer Chemist Clerk Confectioner Contractor Custodian Deck man Driver Dyeddyer’s helper Electrician Electronic technician Engineer Executive Finisher Foreman Grinder Grit blaster Grower Guard Hatter Helper Ice maker Inspector Janitor Laborer Machine operator Machinist Maintenance Mason Mechanic Mill worker Millwright Miner Owner Packer Painter Plastics Plumber Porter Postman Press operator
Cause of death Lung cancer
Mesothelioma
Asbestosis
0 0
I 0 0 0 0 0 0 0 0
0 1 0 1 1 0 1 0 2
0 1 1
0
1
0 0 1
3 1 4 1 0 1 1 1 2 1 1 4
2 1
2 1 1
2 1 1
0 1 0 0 1 1 2 9 2 6 13 4 5 1 0 1 2 1 5 1 1 1 1 1
0 0 2 0 0 0 0 0 0 0 0 0 0 0 0 1
0 0 0 0 0 0 0 1
0 0 1
0 0 0
2 0 0 0 0 0 0 0
0
0 0 2 1
0 0 3 0 1 0
0 1 1 0 0 1 0 1 1
0 0 0 7 0 1 3 0 1 1 0 0 1 0 1 0
0 0 0 0
Total 1 1 1 1 1 1 4 1 6 1 1 2 1
3 5 1 1
7 2 2 2 1 2 3 1 1 1
2 1 1 1 1
2 16 2 8 16 4 7 2 1 1 5 1 6 1 1 1 1 1 (continued)
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501
TABLE V. Occupational Designations on Death Certlllcates in 198 Consecutive Deaths of Lung Cancer, Mesothelioma, and Asbestosis in Former Asbestos Factorv Workers IContinued) Death certificate occupation Printer Produce manager Proprietor Real estate Restaurant Salesman Security Service man Sheetmetal Shipyard worker Sodder Stationary fireman Steward Store room Super Supervisor Tavern owner Textile Truck driver Typesetter Upholsterer Waiter Warper Watchman Weaver Welder Not available Expert asbestosa President asbestos companyb Total
Cause of death Lung cancer Mesothelioma Asbestosis Total 1 1 1 0 1 2 3 1 1 1 1 2 1 1 1 1 0 2 5 1 1 1 0 1 8 0 7
1 0 0 1 0 1 0 0 0 0 0 0 0 0 0 0 0 1 1 0 0 0 0 0 0 0 0
0 0 0 0 0 0 1 0 0 0 0 1 0 0 0 2 1 1 0 0 0 0 1 1 1 1 0
1 1 1 1 2 9 1 7
0 0
1 1
0 0
1 1
136
17
45
198
1 1 1 1 1 3 4 1 1 1 1 3 1 1 1 3 1 4
6
This man was the chief engineer of the company. He formulated its principal product from 1934 to 1936. He died in 1951 of mesothelioma, 10 years after the New Jersey company began operations, but he had had asbestos exposure in other plants of the company dating back several decades [Bettes, 19711 and extensive experience in the asbestos industry [Wild, 19211. %e death certificate properly identified him as the president of an asbestos company at the time of d e a t h 4 u t it was not the company being studied. He had been plant manager there until he left to go to another city, to head the U.S. affiliate of a British asbestos company. He died in 1970 of a peritoneal mesothelioma, 29 years after beginning work in the N.J. plant, but had had prior asbestos experience before his work there.
death certificates. For the 198 deaths of lung cancer, mesothelioma, and asbestosis among the factory workers, there was virtually no indication of occupational asbestos exposure (Table V). There were no other occupational designations of asbestos exposure. In general, industries as recorded on the death certificates were consistent with occupations as
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TABLE VI. Deaths with Potential Asbestm Exposure DC cause of death
Occupation
Industry
Asbestosis Lung abscess Pulmonary fibrosis Asbestosis
Laborer Finisher Laborer Millwright
[The N.J.asbestos company] Asbestos company [The N.J.asbestos company] Asbestos manufacturing
categorized. There were four deaths, however, in which “industry” gave evidence of potential asbestos exposure (Table VI). Thus, altogether, six of 198 deaths (3.0%) had some evidence on the death certificate that asbestos was involved (ascertained on best evidence as 1 lung cancer, 2 mesothelioma, 3 asbestosis). We separately analyzed the 16 men in this group who had worked 10 or more years in the plant. Occupations on death certificates were marginally more accurate (Table VII). CONCLUSIONS We have compared death certificate classifications in two cohorts of asbestosexposed workers-asbestos insulation workers ( 1967-1986) and asbestos factory workers (1941-1990). Apart from both having had significant asbestos exposure, the two groups were dissimilar in many important ways at the times when deaths occurred (Table VIII). We were interested in whether these differences would be reflected in greater or lesser accuracy in death certificate categorizationof causes of death and occupations. We anticipated, a priori, that the latter would show little evidence of asbestos work for the factory group, since the factory had closed in 1954 and the men had gone on to other employment. With the tendency to list last occupation on death certificates, prior asbestos work would not be expected to be recorded on death certificates. We also anticipated that medical diagnosis might suffer to some extent in the latter group since the patients and their families would not necessarily have alerted their medical attendants to the possibility of previous asbestos exposure as a potential etiological factor. Neither, of course, would be the case for the long-term asbestos workers in the insulation cohort, who had current or recent exposure, and who lived in an asbestos worker culture with personal contacts and ample information about asbestos hazards. As matters turned out, we were partly right and partly wrong. Correct-with regard to occupations on death certificates-in that asbestos insulation work (with many semantic variations) was found on three-quarters of the insulators’ death certificates but asbestos work in any form was rare on the factory workers’ certificates, even for deaths attributed to mesothelioma and asbestosis. It was as if their previous asbestos work (with much asbestos-associated disease) was not to be retrieved or recalled from a nebulous past, superceded by many other kinds of employment. Parenthetically, the blue collar workers of the factory tended to remain in blue collar trades, and their asbestos-associated disease would have been recorded in these new trades, with prior exposure unrecognized in our computer and registry-driven data analyses. But this effect of latency is hardly new.
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503
TABLE VII. Deaths Among Workers With >10 Years in Same Workplace DC cause of death Occupation Industry Lung cancer Lung cancer Lung cancer Lung cancer Lung abscess Asbestosis Asbestosis Lung cancer Lung cancer Peritoneal mesothelioma Peritoneal mesothelioma Asbestosis Asbestosis Heart disease Asbestosis Asbestosis
Maintenance Laborer Watchman Stationary fireman Finisher Maintenance Paint company Maintenance Engineer Expert asbestos President asb. co. Plumber Tavern owner Stationary fireman Superintendent Millwright
Paint company Not recorded Printing company Hospital Asbestos company Paint company Not recorded Machinery Not recorded [Name of the asbestos company] Not recorded Retired Tavern Machine shop Magnetic products Asbestos manufacturing
TABLE VIII. Comparison of Asbestos Insulation and Factory Workers
Current or recent asbestos work Effective support system with knowledge of asbestos Indoctrination concerning asbestos-associated disease Personal contact with other asbestos workers
Insulation workers
Factory workers
Yes Yes Yes Yes
No No No No
We were pleasantly surprised to find our second concern unwarranted. Disease classification for both groups was comparable. The medical care offered the factory workers years after their last asbestos work was very much as appropriate as that of the insulation workers, in the same disease (asbestos-associated)categories. Medical and pathological diagnosis was independent of patient and family opportunity for awareness of asbestos’s potential for disease. These observations have relevance for public health approaches to occupational disease identification and quantitative evaluation based on death certificate registrations. Disease categories, at least for asbestos, tend to be accurate. Attempts to identify groups at risk by sorting occupational categories can give variable resultsgood for those with current exposures, much less satisfactory for those with long-past occupational exposures. ACKNOWLEDGMENTS I am grateful to my associate, Janet S. Kaffenburgh, for her exigent attention to the compilation of these data since the inception of this prospective study. Mrs. Kaffenburgh died on June 25, 1992. Support for statistical analysis from NIOSH-ALOSH is gratefully acknowledged. REFERENCES Bettes JA Jr (1971): Chapter V. Keasbey & Mattison Company. In “The History of the Asbestos Textile Industry in the United States.” Asbestos, February pp 2-12.
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Breslow L, Hoaglin L, Rasmussen G, Abrams HK (1954):Occupations and cigarette smoking as factors in lung cancer. Am J Public Health M171-181. Coggon D, Pippard EC, Acheson ED (1985):Accuracy of occupational histories obtained from wives. Br J Ind Med 42563-564. Connelly RR, Spirtas R, Myers MH, Percy CL, Fraumeni JF (1987): Demographic patterns for mesothelioma in the United States. JNCI 78:1053-1060. Dubrow R, Sestito JP, Lalich NR, Burnett CA, Salg JA (1987): Death certificate-based occupational mortality surveillance in the United States. Am J Ind Med 11:329-342. Hammond EC, Selikoff IJ, Seidman H (1979): Asbestos exposure, cigarette smoking and death rates. Ann NY Acad Sci 330:473-490. Harrington JM (1984): Occupational mortality. Scand J Work Environ Health 10347-352. Kaminski R, Bmkert J, Sestito J, Frazier T (1981): Occupational information on death certificates. A survey of state practices. Am J Public Health 71525426. Lilienfeld DE (1988): Editorial. Occupation on the death certificate: To use or not to use, that is the question. Am J Ind Med 1 4 119-120. Mayers MR (1952): Industrial cancer of the lungs. N.Y.S. Department of Labor Monthly Review 31:21-24, 27-28. Merler E, Ricci P (1989): Letters to the Editor. Re: Malignant pleural mesothelioma among Swiss furniture workers: A new high-risk group, by CE Minder, JP Vader. Scand J Work Environ Health 15:439-440. Minder CE, Vader JP (1988): Malignant pleural mesothelioma among Swiss furniture workers. A new high-risk group. Scand J Work Environ Health 14252-256. Newhouse ML, Berry G, Wagner JC (1985): Mortality of factory workers in East London 1933-80. Br J Ind Med 42:4-11. Schade WJ, Swanson GM (1988): Comparison of death certificate occupation and industry data with lifetime occupational histories obtained by interview: Variations in the accuracy of death certificate entries. Am J Ind Med 14:121-136. Schuler G, Ruttner JR (1989):Letters to the editor. Mesotheliomaamong Swiss furniture workers. Scand J Work Environ Health 153440442. Schumacher MC (1986):Comparison of occupation and industry information from death certificates and interviews. Am J Public Health 76:635-637. Seidman H, Selikoff IJ, Hammond EC (1979): Short-term asbestos work and long-term observation. Ann NY Acad Sci 330:61-89. Seidman H, Selikoff IJ, Gelb SK (1986): Mortality experience of amosite asbestos factory workers: Dose-responserelationships 5 to 40 years after onset of short-term work exposure. Am J Ind Med 10479-5 14. Selikoff IJ (1990): Historical developments and perspectives in inorganic fiber toxicity in man. Env Health Persp 88:269-276. Selikoff U, Churg J, Hammond EC (1964): Asbestos exposure and neoplasia. JAMA 188:22-26. Selikoff IJ, Churg J, Hammond EC (1%5):The occurrence of asbestosis among insulation workers in the United States. Ann NY Acad Sci 132:139-155. Selikoff IJ, Hammond EC, Seidman H (1979): Mortality experience of insulation workers in the United States and Canada. Ann NY Acad Sci 330:91-116. Selikoff IJ, Hammond EC, Seidman H (1980): Latency of asbestos disease among insulation workers in the United States and Canada. Cancer 46:2736-2740. Selikoff IJ, Seidman H (1991): Asbestos-associateddeaths among insulation workers in the United States and Canada, 1967-1987. Ann NY Acad Sci 643:l-14. Selikoff IJ, Seidman H (1992): Use of death Certificates in epidemiological studies, including occupational hazards. Variations in discordance of different asbestos-associated disease on best evidence ascertainment. Am J Ind Med 22:481-492. Vianna NJ, Maslowsky J, Roberts S, Spellman G, Patton RE3 (1981): Malignant mesothelioma, epidemiologic patterns in New York State. N Y S J Med, April 735-738. Wild RLR (1921): Asbestos mattress covering. Asbestos 3 5 .
