Document rpNMjrYj8KrQV17gyRrZobNw0

f fencer Mortality and Morbidity Among Rubber Workers ** .fiatd R. Monson 3 and Lawrence J. Fine 1 --~.<tRACT--Mortality and morbidity Irom cancer among a , o( 13.S70 white male rubber workers were examined. Each Jp /orked lor at least S years at the Akron, Ohio, plant of the Goodrich Company. The potential period ol follow-up was January 1, 1940 to June 30, 1976. Departmental work were based primarily on records maintained by Local United Rubber Workers. The occurrence of cancer was I^otured by death certificates and by a survey of Akron-area tumor registries from 1964 to 1974. Two types of i^^ytes were made: 1) an external comparison ol mortality rates Agf rubber workers versus rates' of U.S. white males, and 2) an comparison of cancer morbidity rates among persons were employed in various work areas of the plant. Excess 0f specific cancers (observed/expected numbers) among in specific work areas included: stomach and Intestine: making (30/14.4); lung: tire curing (31/14.1), fuel cells deicers (46/29.1); bladder chemical plant (6/2.4), and tire ijjdlm (16/10.7); skin cancer tire assembly (12/1.9); brain Tgmvtr tire assembly (8/2.0); lymphatic cancer tire building ?SX2): and leukemia: calendering (8/22), tire curing (8/2.6), tire finding (12/7.5), elevators (4/1.4), tubes (4/1.6), and rubber fabrics (4/1.1). Agents that may be responsible for these ex- ------- were considered.--J Natl Cancer Inst 61: 1047-10S3, March 1976 two reports were published in which jiJe mortality experience of rubber workers at the B. F. s^oodrich Company. Akron. Ohio, between January 1, 0, and June 30, 1974, was described (1, 2). Excesses iwt .several cancers were seen in groups of employees ptrho worked in specific departments. An employee was mb fered to have died from cancer only if cancer was f*P-4ied as the underlying cause of death on the death emificaie. Most of the analyses were based on the ^epanment in which an employee had worked the poogest. the present report, more details are considered pwh respect to the cancer experience and the work .r^Pcricnce of the Akron employees. Two additional of cancer mortality have been accumulated, and TjB'cases of cancer that have been identified have been jduded. An employee's departmental work experience .** been defined as the number of years he was "*piAied to have worked in the various departments. J?** estimate provides a rough measure of exposure to "^environmental conditions that prevailed. 1, 1971. The potential period of follow-up was from January 1, 1940. through June 30, 1976. Definition of cancer.--In the previous report (/), a person was defined as having cancer only if it was the underlying cause of death. In the present Teport, two additional criteria have been used: 1) Cancers that were listed on the death certificate but were not the under lying cause of death were included. 2) A survey was made of the tumor registries of four Akron-area hos pitals (Akron City. Akron General, St. Thomas, and Barberton Citizens). B. F. Goodrich employees whose cancers were diagnosed between approximately 1964 and 1974 were identified in this survey; these cancers were also included. In the original report. 980 men were determined to have died from cancer between January 1940 and June 30. 1974. In the current study, an additional 379 cases of cancer have been identified. Of these, 68 were the primary cause of death between June 30. 1974, and June SO, 1976; 81 were a secondary cause of death between January 1, 1940. and June 3, 1976; and 230 were incident cases identified solely from the Akron registries. We have essentially complete identification of fatal cancers in this population and an incomplete ascer tainment of the nonfatal cancers. Therefore, a compari son with an external population can be made only for mortality data. In analyses with morbidity data, we have used internal comparisons (see "Analysis of data"). Inasmuch as the identification of nonfatal cases of cancer was made without knowledge of a person's work experien.ee. the incomplete ascertainment should not lead to ahy important bias in within-plant com parisons. Validation of diagnosis of cancer.--The diagnosis of cancer among Akron employees was made initially from death certificates or from rosters compiled from hospital tumor registries. For each person who worked Abbreviations i'sku-. BNA"0-naphihylamine: ICD--tmernaiional Classification of Diseases: PAH=polycyclic aromatic hydrocarbons; PBNA"phenyl-d-naphthylamine. Methods firtition of population. -- B. F. Goodrich em^J^Tees included in this report were the white male members whose mortality experience was previdescribed (/). (Since the early 1940 s. all wage ^pioyees hate been union members.) One person was 0*"ed because of an error in the data; this left a Population of 13.570. Included was any Akron Tee who worked for at least 5 years prior to July 1 Received February 8. 1978: accepted April 27. 1978. * Supported by Public Health Service center gram 5-PI0-ES00002 from the National Institute of Environmental Health Sciences and by a contract with the B. K. Goodrich Company and the United Rubber. Cork. Linoleum, and Plastic Workers of America. 1 Department of Epidemiology. Harvard School of Public Health. 677 Huntington At:c.. Boston. Mass. 02115. j * Depaitment of Physiology. Hart aid School of Public Health. ' We are indebted to Laura Tat lot foe technical assistance anti to the medical tecotd librarians and tumor registrars of Akron City Hospital. Akiott General Hospital. Barbetum Citizen's Hospital, and St. Thomas Hospital of Akron. Ohio, for rccotd review assistance. in?*'' :*f. NO i. OCTOBER 1978 1047 J NATL CANCER INST BFG39186 25209001 1043 Monson and Pine in a department whose employees were found to have an excess rate of a specific cancer, an attempt was made to verify the diagnosis. If a person died in a hospital, that hospital was contacted and more details from the medical record were sought. If a person was identified from a hospital tumor registry, the patient's medical record was reviewed bv the hospital to verify the diagnosis. In general, the initial data were accurate. However, autopsy sometimes revealed that the person did not have cancer, or we found in a few instances that the person was not the B. F. Goodrich employee of the same name. Because corrections were made only for departments in which excess cancer was suspected, no false-positive associations were made. If anything, this procedure led to a slight underestimate of the size of an association between a department and a type of cancer. Definition of departmental work experience.--No precise data were available from company or union records as to the work experience of employees. The data used were obtained primarily from the files of the union. On the dues cards was entered the four-digit number of the department in which the employee was working. Whenever an employee changed departments, the new departmental number was entered in sequence. Although the date of the change was not recorded, a new card was made out every 4 dr 6 years. Therefore, the period when an employee worked in a specific department was known, and the actual year of entry into the department could be estimated. Prior to 1933. no departmental information was available from union records. All that was generally available from company records was the service date, that is. the year of employment adjusted for layoffs. In this analysis, the years between the service date and 1933 were assumed to be spent in the same department that the employee was in when the union was organ ized in 1933. This probably is a reasonable approxi mation: Prior to 1952 transfers from one plant division to another were uncommon, and consequently the opportunity to transfer from one department to an other was limited. Analysis of data.--The first step was to an; mortality experience from January 1, 1940. to 1976. of all employees as compared to U.S. whi (51. On the basis of an apparent excess of one cancers, specific departments were selected for analysis. Grouping of departments was done t excess of specific cancers was seen in departme had similar industrial processes or exposur ployees in departments with no excess of a cancer were grouped together as "residual" em Next, age- and time-standardized morbidii were computed for specific cancers in specific ments. with the use of data on all incident The standard used was the age-specific persr distribution of all 13,570 employees. The standa of the standardized rate was computed (t) Analyses were next done according to the nu years an employee worked in a department or g departments. If an excess of cancer was seen men who had worked some minimum number in a department (for example, 5), in subsequem ses men who worked 0-4 years were not indue advantage of this exclusion was that overlap of menial experience was greatly reduced. Th< whereas a hierarchical grouping of work exp was used, there was no important uncertainty which department an individual belonged. Finally, a direct comparison was made b employees in departments with an excess of a ; cancer and employees in residual department, observed numbers of cancer among employees Iected departments were distributed according it acteristics of age and time. The numbers ex among these employees were computed on the b the age-specific rate of cancer in the group of rt emplovees. These comparisons are illustrated it '2. RESULTS Stomach and Intestinal Cancer As seen in table 1. stomach cancer (ICD code 15 Table 1.--Mortality and morbidity from cancer of the stomach or intestine according to work area Work &re& and minimum years in area* Rubber making.* 5+ yr Solid tires/track. 5+ yr Residual Total Reported No. of deaths* Cumulative No. of cases* No. of persons* Observed Expected* Total cases Standardized rate7 Rate rati Stomach Intestine Stomach Intestine Stomach Intestine Stomach Intestine Stomach Inu 718 12 13 5.7 6.5 13 17 63 (18) 78 (19) 22. 5 307 4 8 2.1 3.0 4 9 41 (20) 89 (30) 1.4 12.545 13.570 82 98 86 86.1 94.5 92 107 93.9 104.0 109 122 29 (3) 38 (3) 148 -- -- 1.0 -- 1 * * Employment in work areas is mutually exclusive and hierarchical from the top. * No. of persons who worked at least the minimum number of years in the area. ' Deaths occurring during the period January 1. 1940-June 30. 1974. 25203002 4 Cases occurring during the period January 1, 1940-June 30. 1976. ' Calculated on the basis of U.S. mortality rates for white males. ' Rate/100.000 persons/yr. Standardized by the direct method to the age-specific person-year distribution of all 13.570 P Values in parentheses are SE. ' Includes compounding, mixing, milling, and testing. J NATL CANCER INST BFG39187 VOl_ 61. NO 4. Cancer in Rubber Workers ih, ' --Observed, and expected cases of stomach and intestine cancer in selected departments, according to selected characteristic Hp Characteristic - inr'"1 working in department, yr working in department K.f yr worked in department it cancer occurrence, yr 1; v'of occurrence Category <35 35-44 >45 <1925 1925-1939 >1940 5-14 15-24 >25 <65 65-74 >75 <1960 1960-1969 >1970 No. of cases among workers in rubber making* Observed Expected 13 6.7 15 4.5 2 3.2 3 3.9 20 7.4 7 3.0 11 5.8 11 4.7 8 3.8 10 5.8 11 4.9 9 3.6 6 5.6 16 5.5 8 3.2 No. cl cases among workers in solid tires/tracks* Observed. Expected 5 2.2 2 1.9 6 2.2 5 1.6 3 1.3 5 3.4 7 3.8 1 0.9 5 1.6 2 2.6 5 2.0 6 1.7 4 2.2 5 2.5 4 1.6 fszpected eases were calculated on the basis of age-specific morbidity rates for residual employees, as defined in table * jnimunt of S yr in work area. sior; was increased in men who worked at least 5 in rubber making (compounding, mixing, milland testing laboratories). Intestinal cancer (ICD 153) was increased in men who worked at least 5 in rubber making and in those who worked at si 5 years in solid tires/tracks. As seen m table 2. the of cancers of the stomach and intestine among who worked at least 5 years in rubber making irred primarily in those who started working before 45. who started working after 1925. and who velo; cancer since 1959. For men who worked at st 5 >cars in solid tires/tracks, the excess was seen ilv at age 65 and above. [Pancreas Cancer ^ Pancreas cancer (ICD 157) was increased in two Pp&ssimilar departments--elevators and tire curing (taV jg||>le 3). The age-standardized rates in these departments f Eg!Were. respectively. 3.0 and 2.5 times higher than in 7th F*^edXeipenartw: hn did (S. not work at least 5 years in one of these Lung Cancer Excess lung cancer (ICD 162. 163) was seen in three departmental groupings: tire curing, tire molds, and in* fuel ceils/deicers (table 3). The excess lung cancer occurred only in men who worked at least 5 years in coring or in molds. For fuel cels/deicers. the excess was greater in men who worked 0-4 years than in those 1 who nr,i ;<,.(! a ionger period of time. Although several jRen a .<-U borh in juei cells and deicers, the excess ,un< ..liter was associated with each department `ndqx-mierniv I Eor men who worked in tire curing, an excess of UnS cancer was seen in each category of the age- and 'mc-Mandardized characteristics, except for those who ft* ^5fUxl working after age 45 (1 observed. 2.5 expected). c major employment in the fuel cell/deicers deparicn,s was during World War II: therefore, few men started working there prior to 1940. The predominant excess of lung cancer in these men occurred under age 65 (30 observed, 17.6 expected), before 1970 (30 ob served. 16.2 expected), and inTnen who worked fewer than 25 years (45 observed. 28.8 expected). Prostate Gland Cancer Two apparently unrelated departments--material conservation and final finish--were identified in which 4 men who had worked at least 25 years developed (and died from) prostate gland cancer (ICD 177).`Even though these men were older than the residual group, the age-standardized rates of prostate gland cancer were considerably elevated (table 3). Excess cancer of the prostate gland was also seen in men wHio worked in machine maintenance, with the greatest excess being seen in those who worked a relatively short time. Bladder Cancer Bladder cancer (ICD 181) was seen to the greatest excess in men who ever worked in the chemical plant and in those who worked at least 5 years in tire building (which includes band. bead, and tread pro duction as well as tire assembly). In the previous studv (I), men who worked in warehouse/shipping had the greatest excess of bladder cancer. In the data presented in table 3. the excess in these departments is minimal. Among men who worked in the chemical plant or in tire building, excess bladder cancer was seen only in those who started working in the departments between 1925 and 1940 (13 observed. 5.9 expected) and who worked at least 15 years in the department (18 observed. 9.9 expected). Skin Cancer Skin cancer (ICD 190. 191) was seen to excess in men who worked in tire assembly (table 3). This is the work VOL t. OCTOBER 1978 BFG39188 2S2QS003N; CER INST Cancer in Rubber Workers : ^--Observed and expected eases of stomach and intestine cancer in selected departments, according to selected characteristic.' P- Characteristic Category No. of cases among workers in rubber making* Observed Expected No. of cases among workers in solid tires/tracks* Observed Expected - tarted working in department, yr <35 13 6.7 5 2.2 35-44 IS 4.5 2 1.9 >45 2 3.2 6 2.2 working in department <1925 3 3.9 5 1.6 1925-1939 20 7.4 3 1.3 >1940 7 3.0 5 3.4 yr worked in department 5-14 11 5.8 7 3.8 * 15-24 11 4.7 1 0.9 >25 8 3.8 5 1.6 at cancer occurrence, yr <65 10 5.8 2 2.6 d error v 65-74 11 4.9 5 2.0 >75 9 3.6 6 1.7 nbrrtl Mof occurrence <1960 6 5.6 4 2.2 1960-1969 16 5.5 5 2.5 up * >1970 8 32. 4 1.6 >nly ran | anal*, ed. A* txoected cases were calculated on the basis of age-specific morbidity rates for residual employees. as defined in table 1. finimum of 5 yr in work area. cion; was increased in men who worked at least 5 started working there prior to 1940. The predominant iepaix* rs in rubber making (compounding. mixing, mill- excess of lung cancer in these men occurred under age refore. , and testing laboratories). Intestinal cancer (ICD 65 (30 observed. 17.6 expected), before 1970 (30 ob- ?ricn<r , 153) was increased in men who worked at least 5 served. 16.2 expected), and in men who worked fewer as to rs in rubber making and in those who worked at than 25 years (45 observed. 28.8 expected). st 5 years in solid tires/tracks. As seen In table 2. the of cancers of the stomach and intestine among who worked at least 5 years in rubber making Prostate Gland Cancer irred primarily in those who started working before Two apparently unrelated departments--material 45. who started working after 1925. and who conservation and final finish--were identified in reIo 'I cancer since 1959. For men who worked at which 4 men who had worked at least 25 years least 5 >ears in solid tires/tracks, the excess was seen developed (and died from) prostate gland cancer (ICD sly at age 65 and above. 177). Even though these men were older than the residual group, the age-standardized rates of prostate [Pancreas Cancer gland cancer were considerably elevated (table 3). Excess'.cancer of the prostate gland was also seen in .Pancreas cancer (ICO 157) was increased in two men who worked in machine maintenance, with the F&ssimilar departments--elevators and tire curing (ta greatest excess being seen in those who worked a lkie 3). The age-standardized rates in these departments `were, respectively. 3.0 and 2.5 times higher than in relatively short time. J*en who did not work at least 5 years in one of these wdepart: .,s. Bladder Cancer ispr;TIJ-Ung Cancer Bladder cancer (ICD 181) was seen to the greatest excess in men who ever worked in the chemical plant and in those who worked at least 5 years in tire Excess lung cancer (ICD 162. 163) was seen in three building (which includes band. bead, and tread pro departmental groupings: tire curing, tire molds, and duction as well as tire assembly). In the previous study ' cells/deicers (table 3). The excess lung cancer (/). men who worked in warehouse/shipping had the occurred only in men who work'd at least 5 years in greatest excess of bladder cancer. In the data presented curing or in molds. For fuel cel*/deicers. the excess in table 3. the excess in these departments is minimal. greater in men who worked 0-4 years than in those Among men who worked in the chemical plant or in } who wr.rxed a longer period of time. Although several men A ,,ii koth jn juej ceus an{( deicers, the excess tire building, excess bladder cancer was seen only in those who started working in the departments between ,UI'< .ittter was associated with each department 1925 and 1940 (13 observed. 5.9 expected) and who tndepetnlrntly. worked at least 15 years in the department (18 observed. For men who worked in tire curing, an excess of Untt cancer was seen in each category of the age- and 9.9 expected). "me-standardizcd characteristics, except for those who lifted working after age 45 (1 observed. 2.5 expected). Skin Cancer e major employment in the fuel cell/deicers depart ments was during World War II; therefore, few men Skin cancer (ICD 190. 191) was seen to excess in men who worked in tire assembly (table 3). This is the work vot_ ' sr> t. 0CT08ER 1978 BFG39189 2S20905 CANCER INST 1050 Monson and Rne ( *> 4 Table 3.---Mortality and morbidity from cancer according to work arta - Reported Mo. of deaths' Cumulative Mo. of cases* Work area, and minimum years in area' p^ers*ons Observed Expected* Total eases Standardized rate7 Rat rati Pancreas cancer Elevators. 5+ Tire curing. 5-tResidual Total 259 5 2.0 6 47 (20) aA 660 12.651 13.570 6 42 53 3.6 8 41 (15) *> s 54.7 60.3 52 66 16- (2) Lung cancer Tire curing, 5+ Tire molds. 5+ Fuel cells/deicers. 5+ Fuel cells/deicers. 0-4 Residual Total 661 26 15.0 31 150 (27) ?2 272 1.139 9 23 5.7 20.0 10 26 136 (43) 97 (20) 2.6 14 1.051 10.447 13.570 20 156 234 12.8 199.6 253.1 20 196 283 134 (34) 69 (5) X9 X0 Prostate gland cancer Material conservation. 25+ Final finish. 25+ Machine maintainanee. 5+ Machine maintainanee. 0-4 Residual Total 28 88 846 402 12.206 13.570 4 4 7 1 66 82 0.4 4 274 (136) 7.6 L2 4 88 (46) 2.4 6.8 15 59 (15) 1.6 2.0 7 75 (28) 2.1 78.6 111 36 (3) 1.0 89.0 141 711 -- Bladder cancer Chemical. 0+ 784 2 12, 6 61 (25) 2.5 Tire building. 5+ L969 7 5.3 16 36 (9) X.5 Raw material warehouse/shipping. 0+ 513 4 1.7 4 26 (13) i.i Finished goods warehouse. 0+ 445 4 1.5 5 36 (16) X.5 Residual 9.859 31 29.8 64 24 (3) 1.0 Total 13.570 48 39.5 95 -- Skin cancer Tire assembly. 5+ Residual Total 1.299 12.271 13.570 2 L8 7 15.2 9 17.0 12 47.0 (14.1) 6.5 23 7.2 (1.5) 1.0 35 -- -- Tire assembly. 5+ Residual Total Tire building. 5+ Residual Total 1.299 LL271 13.570 1.969 11.601 13.570 Brain cancer 7v 13 20 Lymphatic cancer 6 15 21 4.3 20.8 25.1 2.3 18.9 2L2 8 22.2 (7.9) 4.1 17 5.4 (1.3) 1.0 25 -- -- 8 15.7 (5.6) 2.5 19 27 6.4 (1.5) -- 1.0 -- - Calendering. 5+ Tire curing. 15+ Tire building. 5+ Elevators. 5+ Tubes. 5+ Rubber fabrics. 0+ Residual Total Leukemia 316 4 1.5 8 57 (21) 3.6 421 5 1.8 8 50 (18) 3.1 1.957 7 6.1 12 26 (7) 1.6 252 3 1.2 4 46 (29) 2.9 339 4 1.3 4 40 (20) 2.5 280 4 0.9 4 55 (28) 3.5 10.005 13.570 28 55 30.2 43.0 38 78 16 (3) -- 1.0 ~ * Employment in work areas is mutually exclusive and hierarchical from the top. * Mo. of persons who worked at least the minimum number of years in the area. 25203005 * Deaths occurring during the period January 1. 1940-June 30. 1974. * Cases occurring during the period January l. 1940-June 30. 1976. ' Calculated on the basis of U.S. mortality rates for white males. 7 Rate/100.000 persons/yr. Standardized by the direct method to the age-specific person-year distribution of all 13.570 pers Values in parentheses are SE. area where the components of the tire are put together. Most of the skin cancers were of the squamous ceil type and 4 were fatal. Since skin cancer is usuallv not J NATL. CANCER INST fatal, most of the skin cancer was ascertained u> hospital tumor registry review, which covered period 1964-1974. The excess occurred mainlv in 1 VOL 61. NO. 4. OCTOIU * BFG39190 ( Cancer In Rubber Worker , worked at least 25 years in tire assembly (8 0.9 expected). 3.0 2.5 i a id Cancer in cancer (ICD 193) was seen to excess in men worked in tire assembly (table 3). It occurred only jcn under the age of 65 (8 observed. 1.3 expected) those who started working after 1925 (8 ob1.3 expected). Brain cancer was seen mainly in ^who worked less than 15 years in the department jjfcbjerved. 1.4 expected). -ij .0 jhatlc Cancer and Leukemia lymphatic tumors (ICD 200. 202) were seen to excess ^men who worked at least 5 years in tire building Me 3)- Leukemia (ICD 204) was seen to excess in who worked in six different departments. Except -tire building, the rate for leukemia in each of these rtments was at least 2.5 times the rate in the iduat workers. lese two diagnostic categories were grouped in ter analyses. An association of interest is with the that work in the department started. For men started working after 1945. no excess leukemia or iphatic cancer was seen (4 observed*. 4.5 expected), a. only a slight excess was seen in men who worked than 15 years in one of these departments (10 red. 8.2 expected). ie >pecific diagnosis of the leukemias or lymphatic aors among the men who worked in one of the irtments specified in table 3 were: lymphosarcoma, cases: reticulum cell sarcoma. 1 case: malignant iphotna. 1; lymphatic leukemia. 19: myeloid leu[kcmia. 15; monocytic leukemia. 2: and other and specified leukemia. 4. MSCUSSION In analyzing these data, we relied heavily upon arching for associations between specific cancers and ork departments in which specific substances were used. U`e grouped such departments when consistent ^^associations were seen. This strategy was used because ^ the complexity of the work patterns within the plant 5 3%and because of general uncertainty as to the nature of It hazard of working in the rubber industry'. This JS "nnegy -requires cautious interpretation of any associa>on. To judge whether any cancer-department associaton is likely to be causal, independent data must be evaluated. Such data include other studies of mortality f and morbidity among human populations and toxi cology -.tudies on animals. AK`>. internal consistency in the data can be used. If of a specific cancer are found in departments at have a common exposure, it seems reasonable to ^nriMder the possibility that the association is causal. ,,n analyses in which the cancer morbidity rates in rcsidual" workers were used to compute the expected nntber of cases of cancer among workers in specific "apartments, the resultant patterns of ohserved-to-exP^ted ratios would largely be independent of the data VOl~ "l Nn t. OCTOBER 1978 searching process used. To the extent that these pat terns are in accord with knowledge of exposure pat terns, inferences as to causality may be made. Gastrointestinal Cancer The excess of cancers of the stomach and th intestines among men who worked in processing tend to support causal association. Excesses of these cancer have been reported in other studies of rubber worker (5-7). These excesses also tended to occur in area where the ingredients of rubber are compounded an< mixed (8-10). Traditionally, the processing area has been dustv with a large fraction of the non respirable airborn. particulates likely to be trapped on the surface of th. respiratory tract and eventually swallowed. Followini are several compounds that should be considered as th. agents responsible for the excess stomach and intestina cancer. Carbon black.--Carbon blacks were introduced intc the rubber industry during World War I. Three com mon types of carbon blacks have been used: 1) channe black (average particle diameter, 5-30 nm), 2) furnaci black (30-80 nm). and 3) thermal black (120-150 nm) The furnace type is the most common. Many furnaci blacks have surface-adsorbed PAH that can be extractec by organic solvents (11). Some of these adsorbed PAP have been shown to be carcinogenic and mutagenic ir animals or bacterial test systems (11-15). Wherea: current exposure to carbon black rarely exceeds 1 mg/mJ (mass respirable), past exposures were probably higher, inasmuch as the threshold level is 3 mg/m; (16). In one study of workers exposed to carbon black during its production, no excesses of cancers were found (17). Softeners, extenders, and plasticizers.-- In the pro cessing area, these substances are added to nearly all rubber compounds. Many are petroleum or coal tat products (18). Processing oils, common softeners, con tain modest amounts of PAH. Other compounds used as softeners or plasticizers include coal tars, asphaltum fluxes.* and petroleum-derived waxes. Coal tars have been suspected of causing a wide range of human cancers (19). Antioxidants and accelerators.--Several of these agents are suspected of being carcinogenic on the basis of animal studies (A), of forming carcinogenic metab olites (B). or of being mutagenic in bacterial systems (C) (20-23): antioxidants--4-isopropoxydiphenvlamine (A) . iV. iV-diphenvl-p-phenylene diamine (C). PBNA (B) , and sym-2/i-naphihyl-p-phenylene (C): accelera tors--2-mercapioben.zoihiazole (A). <V-oxydiethylene-2benzoihiazole (A), hexamethylenetetramine (A), and bis(dimethyldithiocarbamato)zinc (A). Several compounds have been extensively used. For example. 1 million pounds of PBNA were used each _____ 25203CO * Asphaltum oil or fluxes are black, tarry materials obtained bv partial blowing (oxidation) of 0111 residue* from the distillation of petroleum. J NATL CANCER INST BFG39191 1052 Monson and Fine ( r year. Although PBNA is metabolized to BNA. a potent bladder carcinogen (22). we found no excess bladder cancer among processing workers. It is interesting that no excess lung cancer was found in the processing area. We earlier reported an increase of respiratory morbidity among processing room workers (24). Pancreas Cancer The excess pancreas cancer in men who worked in elevators and in tire curing is of questionable im portance. The excesses are based on relatively small numbers, and these departments do not share any common exposure. Lung Cancer The excess lung cancer in men who work in tire curing is based on relatively large numbers. A similar excess among curing workers has been reported (6). Curing workers in Akron had increased death rates from pneumonia (/). We also reported an increase in respiratory morbidity among current curing workers in other tire plants (25). In the curing area, the likely causal agents are the constituents of the curing fume. This fume is the result of the volatilization of the basic ingredients in the tires. The major.constituents are rubber polymers, antioxidants, accelerators, and lowboiling constituents of softeners (26). The amount of PAH in the curing fume would not be great because of their high boiling points. Another possible exposure was to talc, which was used to dust some types of tires. An excess of lung cancer has been reported in talc miners (27). The excess of lung cancer in men who work in the tire molds area is small. This is a standard metal machining shop and the only likely adverse exposure is to cutting oils. Nitrosamines, which are animal car cinogens. are present in cutting oils (28). However, no excess of lung cancer was seen in a study of exposure to cutting oils (29). The data on lung cancer in men who worked in fuel cells/deicers is unusual in that the excess was seen mainly in men who worked a relatively short time. This is not surprising, inasmuch as employment in this department occurred largely during World War II. If this is a causal association, a chlorinated organic solvent or acetylene black most likely was responsible because exposure to these agents was higher here than in other departments. In the deicer operation, acetylene black was sprayed on metal. Also, ethylene dichloride was used predominantly in these areas. This substance has been reported to be a bacterial mutagen (JO). Prostate Gland Cancer Excesses of prostate gland cancer among all rubber workers have been reported (5. 7). The excess cases of prostate gland cancer are not likely due to a common exposure, because no apparent link exists among the departments. Machine maintenance is a standard en gineering shop: the most likely causal exposure would be to cutting oils (28). Although cadmium expo* has been reported to be associated with prostate g|a cancer (31). exposure in this plant was not apprecial Bladder Cancer Cancer of the urinary bladder has long been reci nized as a disease of rubber workers (32). However one recent study of rubber workers, no excess bladder cancer was found (5). The excess of bladder cancer in chemical workers relatively small. Two of the men worked only fQl year in the chemical plant. However, two oth worked for at least 15 years with the PBNA autocla therefore, a causal connection must be seriouslv Cc sidered. (A third man who worked with PBNA frc 1952 to 1962 died from bladder cancer on October 1976.) BNA or one of its metabolites is the substar believed to have caused bladder cancer in rubl workers in earlier studies. PBNA has been demc strated to metabolize to BNA in the body (22). Skin Cancer and Brain Cancer Excesses of cancers of `the skin and brain w observed among men who worked in tire assemt departments. Both types of cancers have large rr ratios: 6.5 and 4.1. respectively. Most of the sk cancers were of the basal cell or squamous types ai were located predominantly on the neck and head. T skin cancer excess occurred in men who started wor ing before 1940. whereas the brain cancer excess w present in men who started working after 1940. Few unique exposures were noted in this area. Oi possibility was carbon tetrachloride, a potent anim carcinogen (33). This solvent was added to oth solvents to reduce flammability. Two exposures may related to the excess skin cancer. One is exposure to tl drum resins, which contained coal tars and which ha been associated with skin cancer in other industri (19). The second is exposure to the accelerator hex methylenetetramine. a suspected animal carcinog< that has been described as a common cause of derm titis among tire builders (21, 34). Leukemia and Lymphatic Cancer Excesses of leukemia were found in many depai ments where solvents were extensively used. Sohen were used in calendering, extrusion, tire buildin tubes, and rubberized fabrics. An association be'.wet solvent exposure and lymphatic and hematopuiet cancer has been reported in another group of rubb workers (35). Also, excesses have been reported rubber workers in general (l. 6. 7). We have examined work practice manuals and vent recipes and have discussed work practices wt> older employees to identify the predominant sol'Cexposure during the late 1920`s to the early 1940 -> h clear that benzene was not used as a general-purp solvent. Its use was restricted to special rubber ceme" and adhesives, particularly those for use in bond'1 J NATL CANCER INST BFG39192 2320Em07 .TOO' *r ( ( Cancer in Rubber Work* 'Mjrj 3^n(j :abie. ry % i 31 to rubber, and to some repair or patching aenis. The most common solvents used in this mXnpany were refined petroleum solvents, principally jKhch-tesi gasoline and varnish maker's naphtha. All jeJnned petroleum solvents are complex mixtures of Krdrocarbons and contain a low percentage of benzene. Snv substance responsible for the excess of leukemia or Cniphatic cancer is believed to have been removed or <Juced in the work environment, inasmuch as men 1*3 >tarted work after 1945 do not have an excess rate thv-e diseases. for two other reasons, we hesitate to attribute the s of leukemia solely to benzene. First, the predom- nt leukemia was lymphatic. Epidemiologic evidence an association between benzene and lymphatic kemia is less convincing than the evidence for an iation with other leukemias (36. 37). Second, one the areas with excess leukemia deaths also has an cess of lymphosarcoma, a tumor not known to be iated with benzene. ?In summary, several associations between work area land -;.<cific sites of cancer are likely to be causal, ese are the association of gastrointestinal cancer th the processing area, lung cancer with. curing, leukemia with extensive organic solvent exposures, and cancers of the skin and other sites with the tire Assembly area. 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