American Journal of Industrial Medicine 13:731-734 (1988)

BRIEF COMMUNICATION

Asbestos Disease in Sheet Metal Workers: Proportional Mortality Update

David Michaels, PHD, MPH, and Stephen Zoloth, PhD, MPH

This paper, updating the findings of an earlier study, provides additional evidence that sheet metal workers in the construction trades are at increased risk for asbestos-related disease. A proportional analysis of cause of death among 331 New York sheet metal workers found a significantly elevated PMR for lung cancer (PMR = 186). In addition, there were six deaths attributable to mesothelioma (three classified as lung cancer deaths) and three death certificates mentioned asbestosis or pulmonary fibrosis, although none of these three deaths were attributed to these diseases.

Key words: construction workers, occupational disease, lung cancer, mesothelioma, asbestosis

INTRODUCTION

An earlier proportional mortality analysis of New York City sheet metal workers found elevated PMRs for cancers of the lung, colon and rectum, and mesothelioma [Zoloth and Michaels, 19851. This analysis was based on 385 deaths that occurred among members of Local 28 of the Sheet Metal Workers International Association, the union representing New York metropolitan area sheet metal workers, between January 1976 and April 1983. O n the basis of documented patterns of sheet metal worker exposure to asbestos, discussed in that paper and elsewhere [Paik et al., 1983; Reitz et al., 19721, the previous study concluded that these elevated PMRs could be attributable to asbestos exposure.

A study of mortality patterns in the four years subsequent to the initial study was conducted in 1987 in order to determine if sheet metal workers continued to have elevated risk of asbestos-related mortality. It should be noted that, in the intervening years, Local 28 expanded its membership through merger with several smaller New York metropolitan area sheet metal worker locals, resulting in a substantially larger local and benefit plan membership.

Program in Occupational Health, Department of Epidemiology and Social Medicine, Montefiore Medical CcntedAlbert Einstein College of Medicine, Bronx, New York (D.M., S.Z.). Hunter College School of Health Sciences, City University of New York (S.Z.) . Address reprint requests to Dr. David Michaels, Program in Occupational Health, Department of Epidemiology and Social Medicine, Montefiore Medical CenteriAlbert Einstein College of Medicine, I I 1 East 210th Street, Bronx, NY 10467. Accepted for publication January 4, 1988.

0 1988 Alan R. Liss, Inc.

732 Michaels and Zoloth

METHODS

After ten years in the union, members of Local 28 become vested in the pension plan administered by the local. In order for the death benefit to be paid, when a member of the plan dies the decedent’s beneficiary must send a copy of the death certificate to the plan. Beaumont et al. [I9811 have shown that data sets derived from records of benefit plans, where survivors have a financial incentive to report the member’s death, provide a reasonably representative sample of all deaths in the cohort.

The death certificates for every death reported to the benefit fund office of Local 28 between January 1983 and October 1986 were located. All deaths that were included in the initial study were excluded, as were a small number of women and non-whites, resulting in a study population of 331 white male sheet metal workers. Relevant information, including year of birth, race, sex, year of death, and all listed causes of death, was abstracted from the death certificates onto coding forms. These forms were sent to a nosologist for classification according to the International Classification of Disease (ICDA) revision in effect at the time of death. The New York City Department of Health, Division of Vital Statistics, provided the ICDA classification for those sheet metal workers who died in New York City, as well as copies of the death certificates for those deaths in ICDA categories 162 and 199, lung cancer and unspecified cancer, respectively. This was done to facilitate identification of mesothelioma deaths.

The life table program developed by Monson [ 19741, modified for use in a microcomputer by Maizlish [ 19861, generated expected numbers of deaths and calculated PMRs, or proportional mortality ratios (observed divided by expected, multiplied by loo), using comparable age, sex, race and year of death subgroups of the United States population. All underlying causes of death were recoded to the ICDA Eighth Revision, following the requirements of this program. PMRs were generated for all causes of death of interest, with the exceptions of mesothelioma and asbestosis, for which the U.S. mortality rate is too low to generate meaningful expected numbers.

RESULTS

The proportional mortality ratios for major causes of death are presented in Table 1 . Statistically significant elevated PMRs were seen for all malignant neoplasms (PMR = 148), as well as for cancers of the stomach (PMR = 259), liver (PMR = 260), lung (PMR = 186), and other lymphatic tissue (PMR = 252). A non-significant excess was seen for colon cancer (PMR = 149).

There were six deaths caused by mesothelioma, and a seventh whose death certificate listed “mesothelioma (suspected)” under “othcr significant conditions. ” Of these, the pleura was the primary site of three, and the primary site was not specified for the remaining three which were assigned the ICDA classification of 199. Since the three pleural mesothelioma cases were given the ICDA classification of 162 by the nosologist, they are included in the observed number of lung cancer deaths. However, reclassification of these deaths would not materially alter the observed excess in lung cancer mortality. Finally, three death certificates mentioned either asbestosis or pulmonary fibrosis, although none of these three deaths were attributed to these diseases.

Asbestos Disease in Sheet Metal Workers 733

TABLE I. Proportional Mortality Among Sheet Metal Workers

ICDAa Cause of death Observed Expected PMRb 95%CIc

140-209 150 151 153 154 155-6 157 162 185 I88 189 200-209

200

204 -207 202-203,

208 370-458

460-519 492

d

126-1 74 9-419

127-527 84-267 9-41 1

101-666 26-247

143 -243 29-159 6-212

28-528 62-244

15-774

7-296 117-543

80-100

45-108 14-203 - -

All malignant neoplasms Cancer of esophagus Cancer of the stomach Cancer large intestine Cancer of rectum Cancer of the liver Cancer of pancreas Cancer of lung Cancer of prostate Cancer of bladder Cancer of kidney All lymphatic and

hematopoietic cancer Lymphosarcoma and

reticulosarcoma Leukemia and aleukemia Cancer of other

All diseases of

Nonmalignant respiratory diseases Emphysema

lymphatic tissue

circulatory system

-

111 I 7

I I 1 4 3

48 5 1 3 8

1

1 6

152

18 2 -

75.11 I .65 2.71 7.37 1.68 I .54 3.73

25.78 7.41 2.43 1.73 6.51

0.91

2.26 2.38

169.74

25.94 3.81 -

148’ 61

259‘ 149 59

260” 81

186‘ 67 41

173 123

109

44 252e

90

69 52 -

d - Mesothelioma 6

aInternational Classification of Disease, Eighth Revision. bProportional Mortality Ratio = observed divided by expected multiplied by 100. ‘95% Confidence interval. dAll mesothelioma deaths in this study were classified as either lung cancer or “site not identified” cancer deaths. ep< .05. ‘p<.OI.

DISCUSSION

The results of this study, especially the elevated lung cancer PMR and the observed cases of mesothelioma, a disease almost exclusively attributable to asbestos exposure, strongly support the contention that sheet metal workers are at increased risk of mortality from asbestos-related disease. The previous study found 0.8% of the study population (3 of 385) died of mesothelioma; the 1.8% of the deaths in this study attributable to mesothelioma (6 of 33 1) demonstrates that this disease continues to be an important cause of mortality in this population.

While the limitations of PMR analyses are well known [e.g., Wong and DecouflC, 19821, the results of this study provide further evidence that asbestos exposure continues to cause excess disease among sheet metal workers. These findings support the results of our previous mortality study [Zoloth and Michaels, 19851, as well as those of two investigations into the prevalence of asbestos disease among sheet metal workers. [Michaels et al., 1987; Baker et al., 19851.

734 Michaels and Zoloth

ACKNOWLEDGMENTS

Financial support for this study was provided by the Sheet Metal Industry Promotion Fund of New York City. The authors gratefully acknowledge the assistance of its Executive Director-Counsel, William Rothberg, as well as the officers, members and staff of Metropolitan Local 28 of the Sheet Metal Workers International Association. In addition, we would like to thank Margot Lacher, RN, MPH and Barbara Aiken of the Department of Epidemiology and Social Medicine, Jean Lee, Acting Director of Biostatistics, New York City Department of Health, and Donald L. Lipira, Assistant State Registrar, Bureau of Vital Statistics, New Jersey State Department of Health, for their assistance.

This project was supported in part by a PSC-CUNY research award to S . Zoloth.

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