LUNG CANCER AMONG COKE OVEN WORKERS MINISTRY OF LABOUR, JAPAN

Transcription

1 Ind. Health. 1975, 13, 57. LUNG CANCER AMONG COKE OVEN WORKERS A REPORT TO LABOUR STANDARD BUREAU, MINISTRY OF LABOUR, JAPAN Prepared by a Task Group: Hiroyuki SAKABE (Chairman), Kenzaburo TSUCHIYA (Rapporteur of English version), Noboru TAKEKURA, Shigeru NOMURA, Shigezi KOSHI, Kazuo TAKEMOTO, Hidetsuru MATSUSHITA and Yukio MATSUO (Received November 18, 1974) In the largest iron and steel works in Japan, six cases of lung cancer had been found among coke oven workers from 1947 to Labour Standard Bureau of the Ministry of Labour organized a task group of specialists to conduct an investigation whether these cases should be considered as occupational. This paper is an English version of the report submitted to Labour Standard Bureau from the task group. An epidemiological survey conducted by the Ministry of Labour indicated that lung cancer incidence among retired blast furnace coke oven workers in the iron and steel works exceeded that of the expected number calculated from the general Japanese male polulation and the relative frequency of lung cancer cases to malignant neoplasia of all sites also exceeded that of the expected number. The task group was not able to conduct research on coke manufacturing chemical companies and manufacturing (specialized) companies because the number of lung cancer cases was too small. In 1972, six cases of lung cancer among coke oven workers (one of the largest iron and steel works in Japan) were reported as having occurred over a period of twenty-five years, from Since Kawahata (1938) reported twelve cases of occupational lung cancer in 1938 in the same industry, but among gas furnace workers, the question was raised whether these six new cases of lung cancer were of occupational origin, the old gas furnaces having been completely removed about thirty years previously and the working environment having been changed to a considerable extent. The Ministry of Labour appointed specialists to conduct an investigation in order to determine whether or not the workmen's compensation law should be applied to those six cases, i.e. whether should be considered as an occupational disease. According to a plan made up by the task group. the Ministry of Labour conducted an epidemiological survey on the incidence of lung cancer in all the coke oven industries of Japan. A questionnaire prepared by several members of the task group was sent out 57

2 H. SAKABE et al. to those industries through the Offices of Labour Standards Administration. The questionnaire was filled out by the industrial physician or chief health inspector of each industry. It included questions not only on lung cancer but also on cancer cases other than lung cancer, and in order to obtain information as to the history of those cases, questions about cigarette smoking were, of course, included. However, it was not always easy to obtain reliable information retrospectively on the history of cigarette smoking. Thus, in the analyses of the collected questionnaires, the factor of cigarette smoking was omitted. Nevertheless, other information such as the length of exposure to coke oven works and age of retirement was obtained with a high degree of reliability. The survey included eleven firms of various coke oven industries, and the response rate was 100%. The following is the report to the Ministry of Labour prepared by the task group. I. COKE OVEN WORKS IN JAPAN As of March, 1973, there was a total of 36 firms in Japan which possessed coke ovens under operation: 9 iron and steel works, 9 city gas companies, 7 coke manufacturing chemical companies, and 11 coke manufacturing companies. According to the survey taken by the Ministry of Labour in July, 1973, the number of coke oven workers at these firms was 5,458 (including 587 subcontractors) and the number of retired coke oven workers was 4,655. II. COKE OVENS Coke ovens are categorized as those for blast furnace coke, those for casting coke, and those for general coke, depending on the purpose for which the coke is manufactured. The furnace temperature of coke ovens is about 1,300 Ž for blast furnace coke, 1,200 Ž for general coke and 1,000 Ž for casting coke. III. INCIDENCE OF CANCER AMONG COKE OVEN WORKERS In 1973, the Ministry of Labour requested 16 firms which had coke ovens under operation for a long period of time to do a survey on the incidence of cancer among their coke oven workers (present and retired). The task group appointed by the Ministry of Labour investigated the incidence of cancer among retired workers based on the reports of 11 firms which submitted data on retired workers (4 iron and steel works, 4 city gas companies, and 3 coke manufacturing chemical companies and coke manufacturing companies). First, the incidence of cancer among retired coke oven workers of the 11 firms was investigated, and then the cases of retired workers of iron and steel works and city gas companies were studied. 58

3 LUNG CANCER AMONG COKE OVEN WORKERS 1. Incidence of cancer among retired coke oven workers of 11 firms 1.1. Two thousand two hundred one (2,201) workers who retired between 1947 and 1973 from the 11 firms were traced, and the incidence of total malignant neoplasia showed 91 cases of malignant neoplasia of all sites from 7 firms and 15 cases of lung cancer from 6 firms, as shown in Table 1. The retirement age for each firm was 55 years. (The retirement age at the Hiroshima Gas Company was 55 years until 1963 and 57 years after 1963.) Table 1. Incidence of malignant neoplasia among retired coke oven workers The comparison between the observed number of deaths from malignant neoplasia from 1949 to 1973 among 2,178 retired coke oven workers of the 11 firms and the expected number of malignant neoplasia calculated from the vital statistics on the general Japanese male population for the corresponding period of time with age adjustment is shown in Table 2. The expected number of malignant neoplasia of all sites was and the observed number was 91. Table 2. Expected and observed number of malignant neoplasia and lung cancer among 19,486 person years of retired coke oven workers at 11 firms between 1949 and In comparison with 15 deaths from lung cancer among retired coke oven workers at 11 firms between 1949 and 1973, the expected number calculated from the incidence among the general Japanese male population for the corresponding period of time with age adjustment showed 11.67, as shown in Table 2. There was no signficant difference between the observed and expected numbers. 2. Incidence of cancer among the retired coke oven workers of iron and steel works and city gas companies Coke ovens in the iron and steel works were used solely for manufacturing blast furnace coke, and coke ovens of city gas plants were used for manufacturing coke for blast furnaces, casting furnaces and general use. Therefore, it was decided to separate the two types of companies in order to obtain more accurate information. 59

4 H. SAKABE et al. The number of retired workers who were traced among coke manufacturing chemical companies and coke manufacturing specialized companies was too small to take into consideration The incidence of malignant neoplasia among retired coke oven workers from 4 iron and steel works and 4 city gas companies from 1949 to 1973 (Table 3) and the expected number of deaths due to malignant neoplasia calculated from the general Japanese male population for the corresponding period of time with age adjustment are shown in Table 4. For the iron and steel works, the expected number of malignant neoplasia was and the observed number was 36, with no significant difference between the two. For the city gas companies, the expected number was and the observed number was 51. Table 3. The number of the retired workers traced in the iron and steel works and the city gas companies. Table 4. Malignant neoplasia and lung cancer among retired coke oven workers in the iron and steel works and the city gas companies (5,646 person years for the iron and steel works companies) and 12,030 person years for the city gas companies) 2.2. Table 4 also shows the number of lung cancer deaths during the period from to 1973 among retired coke oven workers from 4 iron and steel works and 4 city gas companies in comparison with the expected number of lung cancer deaths calculated from the Japanese male population for the corresponding period of time. While the expected number of lung cancer deaths for the iron and steel works was 3.38, the observed number was as many as 8. There was a significant difference (p0.022) between the two figures. For the city gas companies, the expected number of lung cancer deaths and the observed number were 7.36 and 6 respectively. 60

5 LUNG CANCER AMONG COKE OVEN WORKERS 2.3. Thus, there was no signifiicant difference with regard to the incidence of malignant neoplasia of all sites between the retired coke oven workers of the iron and city gas industries and Japanese males in general. Nevertheless, the retired coke oven workers of the iron and steel works showed a higer incidence of lung cancer than the general Japanese male population (p 0.022), while the retired coke oven workers of the city gas industry did not show any significant difference in the incidence of lung cancer. 3. Percentage of lung cancer in malignant neoplasia. The aforementioned survey may not have covered all the retired workers, since they were not all available for the follow-up observation. Therefore a further study was performed in order to observe relative frequency of lung cancer in malignant neoplasia of all sites Table 5 shows the relative frequency of lung cancer cases to malignant neoplasia of all sites among retired coke oven workers between 1949 and 1973 of the 11 companies (observed) and that of the Japanese male population for the corresponding period of time with age adjustment (expected). There was no significant difference petween the two figures. Table 5. Relative frequency of lung cancer to Malignant neoplasia among the retired coke oven workers of 11 companies Table 6 shows the observed relative frequency of lung cancer cases to malignant neoplasia of all sites among the coke oven workers of 4 iron and steel works and 4 city gas companies between 1949 and 1973, and the expected frequency calculated from the Japanese male population for the corresponding period of time with age adjustment. There was a significant difference between the two figures for the iron and steel works, while there was no significant difference for the city gas companies. Table 6. Percentage of lung cancer in malignant neoplasia of all sites among the retired coke oven workers of the iron and steel works and the city gas industry. 61

6 H. SAKABE et al In conclusion, the relative frequency of lung cancer cases to malignant neoplasia of all sites among the retired coke oven workers in the total of 11 companies and 4 city gas companies did not show significant difference from that of the general Japanese male population with age adjustment, whereas in the case where the iron and steel works only were selected for observation, the relative frequency of lung cancer in comparison with the Japanese male population showed a significant difference (p 0.05). 4. Age of lung cancer onset and working period at coke ovens In order to study the relationship between the age of lung cancer onset and working period, a total of 18 cases of lung cancer was collected from the retired coke oven workers including workers who retired before 1947 and present coke oven workers (3 cases) of 4 iron and steel works and 4 city gas companies. The result is shown in Table 7. Table 7. Age of lung cancer onset and working period at coke ovens. Note: 1) Among lung cancer cases of city gas companies, age of onset could not be traced for 5 cases, and the age of death was used instead. 2) Numbers in parenthesis show lung cancer deaths from the iron and steel works only. As shown, lung cancer occurred after five years of working and at the age of over about 50 years (except one individual whose age was 44). Among coke oven workers of the iron and steel works, lung cancer occurred after 10 years of working and at the age of over 50 years. 5. Working period at coke ovens and length of period from leaving coke oven work to onset of lung cancer As for working period at coke ovens and length of period from leaving coke oven work to onset of lung cancer in the two industries as shown in Fig. 1, 13 cases whose dates of detection were reliably confirmed indicate that the disease occurred over 7 years after having left coke oven work in workers who worked less than 18 years. With the exception of 2 cases (7 years and 15 years), workers who worked more than 18 years 62

7 LUNG CANCER AMONG COKE OVEN WORKERS Fig. 1. Relationships between working period at coke ovens and length of period from leaving coke oven work to ocurrence. Remarks: "0" on the ordinate means "presently working" had lung cancer within 3 years after retirement. It should be noted that lung cancer onset in the city gas industry shows a shorter working period and a longer period between leaving and onset, in comparison with the iron and steel works. 6. Smoking habits Among 18 cases of lung cancer, 10 people were smokers, 2 non-smokers, and there was no information on smoking or non-smoking habits for 6 people. Reliable material concerning the amount of smoking could not be obtained. 63

8 H. SAKABE et al. IV. OTHER MATERIALS 1. "Survey report on cancer among coke oven workers" prepared by the Yahata Iron and Steel Works, Shin-Nihon Iron and Steel Company, ) A. Lung cancer among coke oven workers 1) No lung cancer was found in 14,149 person years among present coke oven workers (between April and March, 1970). 2) 6 cases in 3, person years of retired coke oven workers were found (between April, 1947 and October, 1972). B. Comparison with other workers (present and retired) of the Yahata Iron and Steel Works 1) The expected number of lung cancer deaths for the present coke oven workers was 0.56 and the observed number was 0. 2) The expected number of lung cancer deaths for the retired coke oven workers ws 3.16 and the observed was 6. There was no significant difference between the two figures. 3) The expected number of lung cancer deaths was 3.72 and the observed was 6 for the total of present and retired coke oven workers. There was no significant difference between the two figures. C. One death by lung cancer was found among the present coke oven workers between March, 1970, and October, D. Lung cancer incidence among the coke-oven workers was not found to be higher than that of the other workers of the same firm (p=0.1). However, this survey was done in comparison with the workers of ther work places of the same firm, and not with the general Japanese male population. 2. "An epidemiological study on lung cancer deaths among industrial workers" by Tsuchiya and Okubo2) Research was done in 1969 on cancer deaths from 1966 to 1968 for about 760 companies which have more than 1,000 workers in Japan. A significantly higher incidence of lung cancer was found among workers between the ages of 50 to 54 years in 59 plants including 20 iron and nonferrous metal plants where coke was handled, as shown in Table Medical report by J. W. Lloyd (Lloyd, J. W. "Long-term mortality study of steel workers. V. Respiratory cancer in coke plant workers"3) The task group discussed this paper in detail and reached the conclusion that the results of Lloyd's study should be taken into consideration in making the decision as to whether or not the six cases in question are related to occupational exposure. In his 64

9 LUNG CANCER AMONG COKE OVEN WORKERS Table 8. Expected and observed number of cases of lung cancer among workers in 59 plants where coke was handled. Tsuchiya and Okubo, 1974 (Ref. 7) Table 9. Temperature runge of carbonizing chambers and excess of lung cancer reported. Lloyed, J.W., et al (Ref. 4) study, Lloyd paid attention to the relationship between oven temperature and lung cancer excess ratio (%), as shown in Table 9. As shown in the table, the higher the temperature is, the higher the rate of lung cancer cases. In 1972, Redmond and Lloyd expanded the coverage of the survey and did a detailed cohort study on lung cancer among 4,661 coke oven workers. The relative risks of lung cancer were 6.87 (significant difference with p 0.01) for full topside workers with 5 or more years experience, 3.22 (significant difference with p 0.01) for workers who were engaged both in topside and side-oven works for 5 or more years, 2.10 for the specialized side-oven workers with 5 or more years experience and 1.70 (no significant difference) for all men with less than 5 years exqerience. There was a question as to whether the high incidence of lung cancer among coke oven workers might partly be related to smoking. Regarding this matter, National 65

10 H. SAKABE et al. Institute for Occupational Safety and Health in the United States stated in its report, "Criteria for a recommended standard, occupational exposure to coke oven emission, 1973," that after having compared the result on smoking habits among American veterans and the lung cancer death rate among coke oven workers, it was not possible to prove a significantly higher incidence of lung cancer deaths among coke oven workers than that of other steel workers solely on the basis of smoking habits because the lung cancer death rate of topside workers is much higher than that of heavy smokers among veterans. 4. Study of the relationship between exposure to coal tar pitch volatiles and lung cancer occurrence among coke oven workers (Mazumdar et al.)5) In 1973, Mazumdar et al. measured the concentration of coal tar pitch volatiles to which coke oven workers were exposed and studied the relationahip between the concentration and the incidence of malignant neoplasia among coke oven workers. They found that the level of coal tar pitch volatiles above an oven is three times higher than that at the side of an oven, and indicated the relationship between lung cancer occurrence and the accumulated exposure (concentration x exposure period in months). They concluded that lung cancer occurrence is related to both the level and period of exposure. 5. Carcinogenic effect of coke oven emission on animals There has been no experiment on the carcinogenic effect of coke oven emission as a whole, but each element of emission was studied individually and benzo(a)pyrene was separated as a carcinogen. Furthermore, several skin carcinogenes were found in coal tar. The chemical structures of these are as follows: Benzo(a)pyrene 9, 10-dimethyl-1, 2-benzanthracene 1, 2, 5, 6-dibenzanthracene 3, 4, 8, 9-dibenzopyrene 3, 4, 9, 10-dibenzopyrene Dibenzo(a, h)acridine Horton et al.6) (1963) reported that a squamous-cell tumor was found in the lungs of 5 out of 33 C3H mice which had been expesed to atomized coal tar at 100 mg/m3 for 35 weeks in the inhalation experiment. Laskin et al.7) (1970) reported that the rats which had inhaled benzo(a)pyrene and sulfur dioxide together were found with changes in bronchial mucous membranes and tumors of bronchogenic origin, but there were no such changes among the rats which had inhaled the above two separately. The above reports and other sources imply that the existence of coal tar and volatiles from coal tar in the coke oven emissions can be at least a partial reason for a high cancer incidence among coke oven workers in iron and steel works. 66

11 LUNG CANCER AMONG COKE OVEN WORKERS V. SUMMARY 1. Lung cancer incidence among retired blast furnace coke oven workers in the iron and steel works exceeded that of the expected number calculatdd from the general Japanese male population (significant difference with p 0.05). 2. The relative frequency of lung cancer cases to malignant neoplasia of all sites also exceeded that of the expected number (significant difference with p 0.05). 3. The task group was not able to conduct a research on coke manufacturing chemical companies and coke manufacturing (specialized) companies because the number of lung cancer cases was too small. 4. The present study, the reports by Lloyd, and others indicate that there is little possibility of lung cancer occurring among coke oven workers of less than about 5 years work experience in the field, and the occurrence of cancer caused by the exposure to coke oven emission among coke oven workers is seen to increase among those with about 5 or more years coke oven work experience. VI. RECOMMENDATIONS BY THE TASK GROUP CONCERNING PRECAUTIONARY MEASURES AGAINST LUNG CANCER FOR COKE OVEN WORKERS IN THE IRON AND STEEL WORKS 1. Facilities Employers should promote the mechanization of the work, technical development of remote control to cast coal into a coke oven, and improvement of facilities such as local exhaust and dust collecting systim in order to minimize the exposure of workers to coke oven emissicn. 2. Working arrangements Employers should set up a standard of operating procedure and a standard for the use of respiratory protective devices for each working area or position in order to minimize the exposure of workers to coke oven emission. 3. Health control A. Employers should provide physical check-ups for coke oven workers at the time of employment and position change and periodically thereafter, and also provide periodic physical examinations for present workers of the iron and steel works who have left coke oven work. B. Physical check-ups should concentrate on early discovery of lung cancers and malignant neoplasia of the skin and other areas. C. Employers should develop a recording system with a long-term record preservation of physical check-ups, as well as results of working environment measurements. 67

12 H. SAKABE et al. 4. Education of workers Employers should educate workers on the dangers of coke oven emission and provide caution signs in the necessary areas. 5. Health control for the retired The Ministry of Labour should consider the possibility of applying the personal record system to retired coke oven workers. Under such a system, retired workers would carry notebooks showing the results of periodical physical examinations as well their history of exposure to coke oven emission. It would be appropriate to apply this system to coke oven workers who have had 5 or more years work experience in the field. REFERENCES 1) Yahata Iron Works, Nippon Steel Corporation (1972). Kokusu Kojo ni Kansuru Chosa Hokoku (Study of Coke Oven Factories), an informal report. Yahata. (in Japanese) 2) Tsuchiya, K. and Okubo, T. (1974). Jap. J. Ind. Health, 16, 438 (in Japanese) 3) Lloyd, J.W., Redmond, C.K., Ciocco, A. and Rush, H.W. (1972). J. Occup. Med., 14, ) National Institute for Occupational Safety and Health, Public Health Service, U.S. Department of Health, Education and Welfare. (1973). Criteria for a Recommended Standard \ccupational Exposure to Coke Oven Emission. Washington. 5) Mazumdar, S., Redmond, G.K. and Sussman, N. (1973). A preprint for presentation at the 66th Annual Meeting of the Air Pollution Control Association, Chicago. 6) Horton, A.W., Tye, R. and Stemmer, K.L. (1963). J. Nat. Cancer Inst., 30, 31. 7) Laskin, S., Kuschner, M. and Drew, R.T. (1970). Inhalation Carcinogenesis, (Edited by Hanna, M.G. Jr., Nettesheim, P. and Gilbert, J.R.), pp U.S. Atomic Energy Commission, Division of Technical Information, Washington. 68