Document 0gbbk1B20VovrD7DB88mLkkBM

2i>5 SC721 P SHAN ORlT j INO 35 British Journal of Industrial Mediant 19H4 ;4 Mortality experience of glass fibre workers 35-3R PLAINTIFF'S EXHIBIT I 2H S SHANNON. M HAYES. J A JULIAN. AND DCF MUIR - DOW-848 From the Occupational Health Program, McMaster Untveriirv Health Sciences Centre. Hamilton, Ontario LSH 3Z5, Canada :: ( ;/ y '7 / u-- 7 />' ^ abstract A hisiorical prospective mortality study was conducted at an insulating wool plant in Ontario. Canada, on 2576 men who had worked for at least 90 days and were employed between 1955 and 1977. Eighty eight deaths were found in the 97-2% of men traced. Mortality was compared by the person-years method with that of the Ontario population. Measurements taken since 1977 show very low fibre concentrations. The overall standardised mortality ratio (SMR) was 78%, significantly below 100. Among plant only employees, seven deaths were attributed to lung cancer compared with 4-22 expected, a non-significant excess (SMR = 166; 95% confidence limits 67 to 342). No confirmed cases of mesothelioma were observed and no other disease was significantly increased in plant workers. 1 ::!' M09000 1S Class fibre has many uses but is also under suspicion as a carcinogen since animal implantation work strongly implies that the dimensions of fibres are more important than their composition with respect to potential carcinogenicity.: Indeed animal studies have found that implantation of glass fibres can pro duce tumours in rats,' ` but studies of exposed indi viduals have failed to detect such effects,' * although Bayliss found an excess of non-malignant respirat ory disease.1 The present paper reports a historical prospective mortality study of workers engaged in the manufac ture of glass fibre. Of especial interest were lung and gastrointestinal cancers, particularly mesotheliomas. Attention was also to be given to non-malignant respiratory disease. Methods and material SITE OF STUDY An insulating wool plant in Samia. Ontario. Canada, was the location of the study. It opened in 1948 with about 200 hourly rated employees and currently has about 500. Initially, a steam blown fibre was produced but a change was made to centrifugallv formed fibres in 1961 A small flame attenuation process occupied a separate area from the mid-1950s until 1974. STUDY POPULATION It was originally planned to include all workers who Reccutd I? November 1982 Accepted 10 January 1983 had been employed for a total of 30 days at any time between the opening of the plant in 1948 and the end of 1977 It was discovered, however, that the main source of records of employees who lefl before 1969 was incompleie. By using income tax records of all employees who worked between 1960 and 1969 together with union records, group insurance rolls, and seniority lists from 1955 to 1962 it was possible io generate a complete list of all the men who had worked at least 90 days and were employed at any time from 1955 onwards. Although records of other employees who lefl before ihen were located, it was impossible to be sure that the list was com plete and would not omit a group among whom the number of deaths might be disproportionately high. In addition, il was noted that few, if any. women had genuine exposure to glass fibre. It was thus decided that the study group would comprise only those men who had worked at the plant between 1955 and 1977 and who had had at least 90 days' total employment; 2576 such men were studied. PERSONAL DATA AND work histories Wherever possible detailed work histones were compiled for the srudy subjects. Not all of these were available, however, although individuals could be divided into three groups: those who worked in the plant only, those who worked in the office area only, and those whose job entailed a combination of plant and office work ("mixed exposure"). In addition, other personal information--such as full name, date of birth, and last known address-- were extracted from ihe records These data were to 35 d4 CGPYR JtHT oAlTIbH N LLiNDwH ML Cl CAL. wCIH 9 AoS t.N 36 Shannon. Haws. Juhailn. assist in tracing those who had left the company The data were transcribed into machine readable form by study team personnel, using mainly a microfiche copy of the original document^ MORTALITY ASCERTAINMENT Vital status was unknown for most of the population and vanous methods were used to trace these men. Two students were hired to make contact with sub jects who might have remained in the area or with family or friends who could provide information. Driver licence bureaus in Ontario and other Cana dian provinces consented to a search of their data bases. Statistics Canada's Vital Statistics and Dis ease Registry found that some subjects had died and provided dates and official causes of death for these men as well as for those found to be dead through other means. Other follow up methods included the use of street directories and telephone books of the local area, current plant employees, driver licensing records, and the United States Department of Immigration and Naturalization. Sources of tracing were recorded and documentation retained ANALYSIS The primary analysis adopted the person-years approach described by Case and Lea.* using a com puter program written by one of us (JJ). Age and calendar specific death rates were computed and compared with those of the Ontario male popula tion. Indirect adjustment was made and SMRs calcu lated. Statistical tests of significance were applied by treating the observed number of deaths as a Poisson variate with a mean equal to the expected number of deaths. When the expected number was greater than three, the approximation to the normal distribution was adopted. The statistical tests were two-sided; an a of DOS was used as the primary level of significance. Because the numbers are small. 95`r confidence intervals have been calculated for some SMRs to indicate the range of possible values. environmental data Historical exposure data were not available for the period of study Samples taken in 1978 and 1979 suggest that optical microscopy counts are rarely over 0-2 fibrevml and the mean levels in were below (H fibresml. ^ Results .......... N. Table 1 shows the distribution of person-years by age and calendar period. It should be noted that some men were employed before 1955 but were only under observation from 1955 onwards. Only 502 men contributed person-years beyond 20 years from their first exposure (13 of these were office workers who would have had very little exposure to fibrous glass dust). The number of men exposed 15 or more years was 303. eight of whom were office employees. All but 74 men were traced, giving a follow up rate of 97-2%. Seventeen of those not found were believed to have emigrated to the United States. Of the remainder, a search of the National Mortality Data Base at Statistics Canada did not yield a death record. Since it is very probable that if any had died in Canada a dealh certificate would have been located, the effective follow up can be considered greater than 97 2%. Eighty eight men were found to have died and death cernficates were located for all but one of them. Additional daia suggested that this death was due to ischaemic heart disease and this cause has been used in the analysis. The expected number of deaths was 113-3 giving a significantly low S.MR of 78`T (;*,' = 5-65. p 0 02). While at least a part of the deficit might have been expected in an occupational population, when 'he analysis was restricted to observation at least 10 years alter hrst employment the SMR was still low--56 dealhs observed v 75-54 expected. SMR * 74 One would have expected ihe healthy worker effect lo have largely attenuated. Mortality was examined by dividing Ihe popula tion into the three groups described aBove (plant only, office only, and mixed exposure). Table 2 shows the observed and expected deaths by ICD chapter headings for those categories with ai least three deaths. Circulatory diseases were fewer than expected in plant only employees but slightly more numerous in men with mixed exposure. Neither difference was statistically significant. Mortality from >............ ...... .... " ".T...... .i-'-:. *T:;:------ -- : .... ....... --......... , i l............ ............. . - 1.......... ST000604 Table I Person- veers at risk bv age and calendar period Calendar period 1955-9 IWM mj-9 1970-4 1V7S-7 TouJ 25 43) 334 1670 2066 1630 6)33 25- tool 1177 1312 2340 2561 . 9091 J5 - 636 1U1 1 1447 1351 1048 V>9 ) Agr > - 154 437 770 1171 M2 3514 53 - 94 181 257 42V 407 1368 63 - j 19 88 127 103 >40 *75 0 : 5 18 33 38 Total 242 1 3361 5749 8202 6684 26417 lr..... . : experience of glass fibre Markers Mortality b\ major cause group for plant, ofpt e. and mtsed exposure groups Plant oni r 0 Circulator* disease* AU cancan Acndcntv. violence etc Respiratory due*** Di*e-irve sysiem dtsorden Other ciuMt Total 30 17 13 4 3 5 72 O " Observed number 0/ deaths. Expected number ot deaths. SMR " SiandirdiKd mortality nno - Q * J 00. E 4074 16-36 22 3) *-31 4 00 6-78 94.97 74 103 58 9! 76 74 76 Ofltv 0f 3 3- 70 2 1 5) 0 2 30 0 042 0 040 l 0 70 6 v.'3 5W* ai 131 n n 0 143 37 -Wtxtd 0E 7 3 83 1 1 36 " 1 39 0 036 0 039 0 057 Hi 8 10 SMR 183 64 144 0 0 0 m all cancers was almost identical with that expected (20 observed v 19-65 expected) with little variation by exposure. Deaths due to accidents and other vio lent causes were low. significantly so for plant only workers (*,' - 4-02. p - 0-04). Non-malignant respiratory diseases accounted for four deaths. All these occurred in plant workers among whom the SMR was 91 The remaining causes of death showed no excess Mortality from more specific causes is shown in table 3. Ischaemic heart disease was low in plant workers and high in mixed exposure employees, although neither difference from expected was statistically significant (gf " 3-29 and 3-44, p > 0 07 and U-06 respectively). Seven deaths from lung cancer were observed in plant only employees against 4-22 expected. The SMR of 166. though, was not statistically significant (at,1 " 1-83. p 0-18). Among office workers the SMR was 560 but with only two deaths the excess was not statistically significant (p = O 10). The 95% confidence interval on the lung cancer SMR for plant only workers was 67 to 342. Because of the width of this interval the data were considered by duration of exposure and by time since first exposure. An increase in the SMR with increasing levels of these variables would suggest a genuine relationship. Table 4 shows these data. While the numbers of deaths become even fewer, the data do not support the hypothesis of a link between occupa tional exposure to glass fibre and increased lung cancer mortality. Permission was granted by the Ontario Registrar General s Office to contact the hospitals in which the deaths from cancer had occurred. All but two such deaths occurred in Ontario. The records showed one man with stomach cancer in whom the clinical history suggested the possibility of mesothelioma. He started working with the cornpans m 1948 at age 38. left in 1966. and died in 1976 Tissue samples were sent to the Canadian Tumour Reference Centre to confirm or refute this diagnosis. Of three pathologists who reviewed the material, two believed it to show a sarcoma, while the third thought that mesothelioma was a distinct possibilits On balance, therefore, it was concluded that a diagnosis of mesothelioma could not be confirmed. Cerebrovascular deaths and those due to cancers of the digestive organs and peritoneum were roughly equal to their expected numbers. Three deaths were ascribed to "bronchitis, emphvsema. and asthma." although since these three causes accounted (or one death each, further comment seems unwarranted. Among plant only workers the three cancers of the genitourinary organs gave a SMR" of 161. Three different sites were affected, however genital organs, kidney, and bladder Lymphatic and haematopoietic malignancies had a SMR (in plant workers) of 92 12-1) observed i- 2T8 expected). Table 3 Mortality from trlectrd rouses for plant, office and mned ripouirr groups Spm/u cause Ischacrtuc Kean drscaac Lung cancer Cerebrovascular Cancer ot digestive organs and peritoneum SroncKdJi. emphysema and asthma Cancer of genitourinary organs. Lvmphaijc and haematopoietic malignancies Plant onl\ O E SMR 20 29 92 67 7 4 22 166 3 5 18 97 5 5 34 94 3 1 62 186 3 1 *6 161 2 2 ] 8 YJ t Sfficr nnh l> t 3 2 67 7 036 H 0 49 0 047 0 f> M 0 0 18 0 023 ill* 112 5 Ml U 0 u 0 u Sturd exposure O E SMR 7 2 94 238 0 044 0 0 04 1 a 0 OJI a u u 15 0 1 0 14 694 0 O 18 0 ;------- ...----- ;..i............ .... .........-....... 0 I| 0 9 0 fl 0 . 1 S 38 Table 4 Lung canctr mortality by duration of rxposurr and by amt jmet firtt eipoiurt -- plant only n-orkm Ttmenoct fint tspmurt (yean) <10 *10 Due--on afupouZ/e (y--n) O >5 OE SM* O l 0*31 32 J I 0*45 723 0 0-28 3 3 1* J.W/f 0 137 Dbcaaiu A major focus of the study was on lung cancer. As noted, the 93% confidence interval on the SMR for that cause for plant workers was very wide (67 to 342). Indeed, the power of ^he study to detect (at an a of 0-05) a true twofold risk of lung cancer mortal ity was only 42%. The more detailed breakdown (table 4), however, did not suggest a genuine rela tionship. Examination of hospital records found a possible case of mesothelioma, but further patholog ical examination could not confirm this Among other diseases of interest, none showed a significant excess. Indeed, both cancers o(the diges tive organs and peritoneum and non-malignint respiratory disease were slightly fewer than expected. No other disease produced a statistically significant SMR, except for accidents and violence. The reason for the shortfall is not clear. The age standardised male death rate from these causes in Lambton couniy (in which the plant is located) from 1966 to 1976 was 103-6 compared with 100 9 for Canada as a whole, so local factors were apparently not responsible.' Because the plant opened in 1948 and the study period ended in 1977 no follow up beyond 3U jears Shannon. Hoyts, Julian. t~nd Muir from first exposure could be achieved. (It was expected when the study was planned that collated mortality data after 1977 for Canada would not be available.) Nevertheless, it is hoped that this popula tion will continue to be followed up and the analjsis repealed in several years We are grateful to all who helped with this research, In particular we thank Fiberglass. Canada, for finanrial support and for (heir continued involvement in this research endeavour; the Energy and Chemical Workers Union. Local 914, for their unremitting cooperation; members of the joint managementlabour steering committee; and pathologists, Drs Elliot McGaughey. Rene Lefebre, and Andrew Churg for reviewing tissue samples. We also thank Mrs Pat Yake for typing the many drafts of this report and for organising materials and meetings throughoul the project and Ms Sandy Martin for her valuable help in the early stages of this project. References Siftmon MF. Wrer<h C MecfUAiim* ol metoeVbomj iniroduc- aon tth jrvd fibrouft |U*i J Vrf Canctr Inn J969.4J ' D*n* JMG TV Abrofrruc effect erf miner*! dun loaded uuo iV p4eu/Ai of mce Be J ip PaPoi 1972,53 190*701 * Hi# jw whitfhejd *5. C*meron 10, Hedtecock GA GUu ftbrn. ibience erf pulmontry hatt/d in production orker 8r J Ind Med I973JO 174-9 * Grow ?. Tumi J. DeTfcvitk RTP Luoft erf worker* cipoced io fibre |Uu i uud? trf iheir paiboiofK ch*fl| and their dux conteni Aeth *rriroti HraiA 1971.13 67-7$ ' Bijrku DL. Dement iM Wiforver JK. Bkjt? HP Monliv pti* term imonf fibrou* |J*u production worker* Ann SY Acad So 197*.27J 3 24-33 * Cft*r FLAM. Lei AJ MuXjrd jji po*onin(. chroeuc bronchiti ftjNd hjft| cancrr Be J Per* Sor Med 1953,9 62-77 ' NitkonjJ Heftith nd WrHare Mostadiv aiiat of Canada Vcrf 7 Genial ~ioruu/ Ottftwft NHW. I 980 J-l 23. j. ___ j__ _____ \___ _ ....-- ' cn a CD cn cn -C3 :