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PUBLIC HEALTH BRIEFS

Causes of Death among Laundry and Dry Cleaning Workers AARON BLAIR, PHD, PIERRE DECOUFLE, ScD,

Introduction The use of carbon tetrachloride, trichloroethylene, tetrachloroethylene (perchloroethylene), and petroleum solvents as dry cleaning fluids may have resulted in hazardous exposures for workers in dry cleaning shops. With about 225,000 dry cleaning workers employed in some 26,000 establishments in the United States,' the number of exposed workers could be quite large. Although multiple chemical exposures are possible, tetrachloroethylene has become the solvent of choice since the 1950s and is used by approximately 75 per cent of the present plants2. The demonstrated carcinogenicity of carbon tetrachloride,3 trichloroethylene,4 and tetrachloroethylene5 in laboratory animals indicates a potential human health hazard and the need for epidemiologic studies to evaluate the health experience of exposed workers. To this end the National Cancer Institute has initiated a cohort mortality study using historical dues records maintained by Local No. 161 (St. Louis) of the Laundry, Dry Cleaning, and Dye House Workers' International Union. During the data collection phase of this study we obtained a limited set of mortality records for the period 1957-1977 from two Union locals. In this preliminary report, the relative frequency of specific causes of death in a small group of former laundry and dry cleaning workers is compared with the experience of the general population.

Materials and Methods Available for study were 330 death certificates of former members of two locals (Kansas City and St. Louis) of the Laundry, Dry Cleaning and Dye House Workers' International Union. The decedents were identified from death benefit lists (representing deaths of active or retired Union members in good standing), reports by relatives and friends, and obituary listings and, therefore, do not represent a complete listing of deaths among individuals ever belonging to these two locals. Although these individuals may have worked in laundry and/or dry cleaning establishments, Union records indicated that 279 had worked exclusively in dry cleaning shops while Union members. Sex, race, age at death, and underlying and contributing causes of death were abstracted from each death certificate. The underlying cause of death was classified according to the appropriate revisions From the Environmental Epidemiology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20014. Address reprint requests to Dr. Aaron Blair. This paper, submitted to the Journal May 8, 1978, was revised and accepted for publication

August 22, 1978. 508

AND

DAN GRAUMAN, MA

of the International Classification of Disease and converted to the 7th Revision Codes6 by a trained nosologist. The age, race, sex, and cause distribution of all deaths in the U.S. for the years 1957-1970 served as the standard of comparison. Expected deaths for five-year age and calendar year groups were calculated by applying the cause-specific, proportionate mortality of the appropriate race-sex group to the number of deaths in each age and calendar year category of the study population using a computer program developed by Monson.7 For deaths occurring after 1970, the expected distribution was estimated from the 1969-1970 data. The absence of a mortality matrix for nonwhite females in this program necessitated manual calculation of their expected mortality from U.S. Vital Statistics for 1957, 1962, 1966, and 19708-l' with the expected distribution of causes for death after 1970 estimated from the 1970 U.S. Vital Statistics. The statistical significance of differences between observed and expected numbers was assessed by a chi-square test with one degree of freedom.

Results The distribution of the 330 deaths among laundry and dry cleaning workers by race, sex and age is shown in Table 1. The predominance of women, particularly nonwhite women, is typical of this occupational group. As shown in Table 2, there were 87 deaths from cancer, whereas 67.9 would have been expected based on the proportionate mortality experience of the U.S. population. Cancers of the lung, cervix uteri, and skin contributed to the excess of cancer deaths. A slight excess of leukemia and liver cancer and deficit of breast cancer also occurred. The elevated proportionate mortality ratio (PMR) for cancer deaths was necessarily associated with a lower than expected relative frequency of other causes, especially circulatory diseases. Although the deviations were not statistically significant, the observed number of cancer deaths for each racesex group was greater than expected (PMRs ranged from 118 to 155), while consistent deficits of circulatory disease deaths occurred. Length of Union membership available from Union dues records from St. Louis served as an indication of the duration of exposure for 146 of the decedents. The cumulative years of membership ranged from less than 1 to 25, with a mean of 13.0 years. The length of Union membership was similar for cancer and non-cancer deaths, except for nonwhite males (Table 3). Among white females the cancer cases joined the Union at a younger age than non-cancer cases, while the reverse was true for the other race-sex groups. The employment history of decedents dying from leukemia and AJPH May, 1979, Vol. 69, No. 5

PUBLIC HEALTH BRIEFS TABLE 1 Distribution of Deaths by Race, Sex, Age, and Union History, 1957-1977

lung, liver, and cervical cancer was comparable to that for non-cancer and other cancer deaths.*

Race-Sex

Age at Death

Male

Discussion

Non-white

White Female

Male

Total Population, N = 330 12 14 5 41 27 44 27 8 36 Decedents Exclusively Dry Cleaners, N = 279 4 11 11 20-44 37 26 43 45-64 7 27 35 65+ Decedents with Union Dues Records, N = 146 20-44 4 7 0 14 45-64 18 23 26 5 65+ 13 20-44 45-64 65+

Female

25 79 12

20 51 7 9 22 5

Tetrachloroethylene, the predominant dry cleaning fluid in use since the 1950s, is an extremely stable chlorinated hydrocarbon. 12 Adverse health effects associated with exposure have included various liver abnormalities such as cirrhosis, hepatitis, hepatomegaly, and altered liver function tests,'3 eye, nose, and throat irritation,'4 nonspecific complaints related to central nervous system depression,2 and - altered EEG patterns.'5 The possibility of a carcinogenic hazard has been suggested by the occurrence of hepatocellular carcinoma in mice given tetrachloroethylene by gavage.5 In this study, the increased proportion of cancer deaths among laundry and dry cleaning workers suggests an elevated risk resulting from exposure to dry cleaning fluids. The slight excess of liver cancer is consistent with bioassay stud*Data available on request to authors.

TABLE 2-Observed and Expected Deaths and Proportionate Mortality Ratios with Chi-Square Values for Selected Causes of Death among Laundry and Dry Cleaning Workers, 1957-1 977 Cause of Death

All Causes Infectious and Parasitic Disease All Malignant Neoplasms Digestive System Stomach Large Intestine Biliary Passages and Liver Pancreas Lung, Bronchus, Trachea Breast Cervix uteri Kidney Bladder Skin Leukemia Other Cancers Diabetes Mellitus All Circulatory Disease All Respiratory Disease All Pneumonia All Other Causes

ICD Codes (7th Rev)

Observed Deaths

330

Expected Deaths

330

001-138 140-205 150-159 151 153

5 87 25 5 9

5.5 67.9 18.0

155-156 157 162,163 170 171 180 181

4 4 17 7

190,191 204 260 400-468 470-527 490-493

10 2 1 3 5 17 9 100 13 9 116

PMR1

Chi-square2 Values

100

5.9

91 128 139 147 152

0.000 6.423 2.474 0.360 1.124

1.7 3.1 10.0 10.1 4.8 1.0 1.2 0.7 2.2 19.9 8.7 125.9 15.0 8.4 107.0

235 129 170 69 208 200 83 429 227 85 103 79 87 107 108

2.050 0.052 4.446 0.994 4.670 0.215 0.084 4.301 2.552 0.357 0.005 9.264 0.183 0.000 0.994

3.4

(p < .05)

(p < .05)

(p < .05)

(p < .05)

(p < .005)

'PMR = Observed/Expected x 100 2X2 -(obs exp- 5) , where N = number of deaths, p = exp, and q = 1 - p. Npq The x2 used is only an approximation of the Mantel-Haenszel x2. The computer program7 used to calculate expected

values does provide the Mantel-Haenszel x2 for each race-sex group. However, since it does not provide the variance for each race-sex group we could not sum to get an overall estimate of the variance. The x2 we used with the variance = Npq is a slightly more conservative test than the Mantel-Haenszel x2. In tests of other data and on race-sex specific groups in this study we found the differences between the two methods to be small (generally in the 2nd decimal position) and better than using the expected value for the variance or a regular contingency table calculation.

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PUBLIC HEALTH BRIEFS TABLE 3-Comparison of Years of Union Membership and Age at Union Initiation for the 146 Decedents with Membership Records (St. Louis only) Non-Cancer Cases

Cancer Cases

Years of Membership White Males White Females Nonwhite Males Nonwhite Females TOTAL Age at Initiation White Males White Females Nonwhite Males Nonwhite Females TOTAL

Mean

N

Mean

N

t

15.7 12.0 14.4 11.6 13.3

9 14 11 10 44

15.3 12.7 8.1 12.0 11.9

18 34 24 26 102

0.04 -0.38 2.33 -0.19

43.7 42.8 36.5 35.2 39.8

9 14 10 10 43

46.8 46.9 37.3 36.7 42.7

18 34 19 19 90

-0.76 -1.46 -0.23 1.82

ies,4 5 but is based on a small number of deaths with only one coded as a primary liver cancer. The slight excess of leukemia deaths is intriguing in light of a report of five cases of chronic lymphocytic leukemia in a man and four offspring who worked in the family dry cleaning business.'6 The five leukemia deaths in this study were confined to whites for reasons that are not clear, although mortality from leukemia is generally about 50 per cent higher in whites than in nonwhites.'7 The cell types represented here (acute leukemia, two cases; monomyelogenous; myelogenous; and unspecified) are more suggestive of benzene exposure, 8-20 although other solvents may also be leukemogenic.21' 22 Benzene has been used in dry cleaning as a spot remover.23 Since the wage scale for laundry and dry cleaning workers is quite low, the excess of cervical cancer may reflect socioeconomic factors. Likewise, the excess of lung cancer may result from the inverse correlation between socioeconomic status and cigarette smoking.24 The small number of deaths, possible biases in the set of decedents obtained, and the general limitations of the PMR methodology necessitate cautious interpretation of the study results. However, this study raises the possibility that exposure to dry cleaning fluids may increase the risk of certain cancers and underscores the need for additional study of this occupational group.

Summary To make a preliminary determination as to whether a potential health hazard exists for workers exposed to dry cleaning solvents (carbon tetrachloride, trichloroethylene, and tetrachloroethylene), we analyzed the causes of death of 330 deceased laundry and dry cleaning workers by the proportionate mortality method. The increased risk for malig510

(p

0.032)

nant neoplasms resulted primarily from an excess of lung and cervical cancer and slight excesses of leukemia and liver cancer. Although the number of deaths was small, the increased risk of cancer noted in this investigation underscores the need for additional epidemiologic studies of this occupational group.

REFERENCES 1. Bureau of the Census. County Business Patterns, 1970. Washington, DC, USGPO, 1972. 2. NIOSH Current Intelligence Bulletin 20. Tetrachloroethylene. DHEW (NIOSH) Publication No. 78-112, 1978. 3. International Agency for Research on Cancer. IARC monographs on the evaluation of carcinogenic risk of chemicals in man. Vol. 1:53-60, 1972. 4. National Cancer Institute Carcinogenesis Technical Report Series No. 2. Carcinogenesis Bioassay of Trichloroethylene. DHEW Publication No. (NIH) 76-802, 1976. 5. National Cancer Institute Carcinogenesis Technical Report Series No. 13. Bioassay of Tetrachloroethylene for Possible Carcinogenicity. DHEW Publication No. (NIH) 77-813, 1977. 6. Manual of the International Statistical Classification of Diseases, Injuries, and Causes of Death. Seventh Revision. Geneva, WHO, 1957. 7. Monson RR: Analysis of relative survival and proportional mortality. Computers and Biomed Res 7:325-332, 1974. 8. Vital Statistics of the United States, 1957. Vol. II. Washington, DC, USGPO, 1959. 9. Vital Statistics of the United States, 1962. Vol. II. Mortality, Part A. Washington, DC, USGPO, 1964. 10. Vital Statistics of the United States, 1966. Vol. II. Mortality, Part A. Washington, DC, USGPO, 1968. 11. Vital Statistics of the United States, 1970. Vol. II. Mortality, Part A. Washington, DC, USGPO, 1974. 12. Hawley GG: The Condensed Chemical Dictionary. New York, Van Nostrand Reinshold Company, 1977. 13. NIOSH Criteria for a Recommended Standard Occupational Exposure to Tetrachloroethylene. DHEW Publication No.

(NIOSH) 76-185, 1976. 14. Stewart RD, Baretta ED, Dodd HC, et al: Experimental human exposure to tetrachloroethylene. Environ Health 20:224-229, 1970. AJPH May, 1979, Vol. 69, No. 5

PUBLIC HEALTH BRIEFS 15. Stewart RD, Hake CL, Forster HV, et al: Tetrachloroethylene Development of a Biologic Standard for the Industrial Worker by Breath Analyses. Rep. No. NIOSH-MCOW-ENUM-PCE 74-6, 1974. 16. Blattner WA, Strober W, Muchmore AV, et al: Familiar chronic lymphocytic leukemia immunologic and cellular characterization. Ann Intern Med 84:554-557, 1976. 17. Mason TJ, McKay FW: U.S. Cancer Mortality by County: 1950-1969, Washington, DC, USGPO, DHEW Publication No. (NIH) 74-615, 1974. 18. Aksoy M, Erdem S, DinCol G: Leukemia in shoe-workers exposed chronically to benzene. Blood 44:837-841, 1974. 19. Vigliani EC: Leukemia: Occupational chemical factors. Proceedings of the XI International Cancer Congress. Vol. 3:248252, 1975. 20. Infante PF, Wagoner JK, Rinsky RH, et al: Leukemia in benzene workers. Lancet July 9:76-78, 1977.

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21. McMichael AJ, Spirtas R, Kupper LL, et al: Solvent exposure and leukemia among rubber workers: An epidemiologic study. JOM 17:234-239, 1975. 22. Brandt L, Nilsson PG, Mitelman F: Occupational exposure to petroleum products in men with acute non-lymphocytic leukemia. Brit Med J 1:553, 1978. 23. International Labor Office. Encyclopedia of Occupational Health and Safety. Vol. 1:411-412, 1976. 24. Public Health Service. Adult Use of Tobacco-1975. USDHEW, Center for Disease Control, NIH, 1976.

ACKNOWLEDGMENTS This paper was prepared for presentation at the 1978 meeting of the Society for Epidemiologic Research.

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