Document KJGEdBvxbVLx43wxz0EZg5kd2

..._... .. : . .~.. ~ . I * d 'Morbidit Richard R. Monson and Lawrence J. Fine 4 5 ..- 4~sTRACT-Mortaiity and morbidity from cancer among a :ohort of 13,570 white male rubber workers were examined. Each *an worked for at least 5 years.at the'Akron, Ohio, plant of the 3. F. Goodrich Company. The potential period of follow-up was irgm January 1. 1940 to June 30, 1976. Departmental work ,jstories were based primarily on records maintained by Local 15, United Rubber Workers. The Occurrence of cancer was fieasured by death certificates and by a survey of Akron-area ,ospital tumor registries from 1964 to 1974. Two types of lnaiyse~were made: 1) an external comparison of mortality rates ,f rubber workers versus rates of U.S. white males, and 2) an nternal comparison of cancer morbidity rates among persons #ho were employed in various work areas of the plant. Excess aseo of specific cancers (observed/expected numbers) among Morkers in specific work areas included: stomach and intestine: ubber making (30114.4): lung: tlre curing (31/14.1), fuel cells and/or deicers (46129.1); bladdee chemical plant (6/2.4), and tire iuiidlng (16l10.7); skin cancer: tlre assembly (12/1.9); brain :ancer: tire assembly (8/2.0); lymphatic cancer: tire building ,8/3.2); and leukemia: calendering (8/2.2), tire curing (8/2.6), tire iuiiding (12l7.5). elevators .(4/1.4), tubes (4/1.6), and rubber abncs (411.1)- Agents that may be responsible for these ex:esses were considered.4 Nati Cancer inst 61: 1047-1053, 1978. underlying cause of death. In the present report, two additional criteria have been used: 1) Cancers that were :. ' and 1974 were identified in this survey; these cancers In March 1976 two reports were published in which the mortality experience of rubber workers at the B. F. Goodrich Company, Akron, Ohio, between January 1, 1940, and June .30, 1974. was described (1, 2). Excesses of several cancers were seen in groups o employees who worked in specific departments. An employee was considered to have died from cancer only if cancer was specified as-the underlying cause of death on the death certificate. Most of the analyses were based on the. department in which an employee had worked the longest. . : : .., .. In the present report, more deiails are considered with respect to the cancer experience and the work zxperience of the Akron employees. Two additional years of cancer mortality have been accumulated, and 111 cases of:-cancer that havq"been. identified,have been . included. An.employee's departmental work experience has been defined a s . the 'number-.of years he .'was estimated to have worked in the various departments. This estimate provides a rough measure of exposure to the environmental conditions. .that prevailed. . .. . - \' . .. . ,. - . ... . .., . . .: - , ,. ABBRKVIATJOiNS Classification of ... C _....-_. .I..,k,-,,-.'... . .-... .. . -r. , ~-- were computed. for,specific' c a n e n in- specific depart. ments, with the -use.of.,data'on' all incident cancers. ents-in,-whid;:excess'cancer was suspected, no T h e standard 'used.-was..the.age-specific person-years ositive k o d a i i o n s .were made. If anything, this distribution of 'all 13,570 employees. T h e standard error sIight.underestimate of the $ize of an o, f..:.the' Lki.n. da..r.d_iz".ed ,,rate::.was- computed ( 4 ) . n .a>cl<partmentand a typ-1'e;-,,.of .cancer. i.z,iAnalys~were;.next::done according..to the .number of rtm'ktal ,'work "experience.-No years a n employee %workedin a department or group of ailable' from"'+mpany or' union departments._,If. an excess,of cancer was seen only in e:w&k. experience of employees. The men who had worked some minimum number of yean :btained primarily from the files of the in a departmen1 (for example, 5), in subsequent analy- u&.."&rds,was entered -ihe Sour-digit . ses men'.who 'worked 0-4 .years were not 'included. An partment in which the employee was advantage' of this 'exclusion. was that- overlap of depari- ' a n .employee changed departments, mental experience was greatly reduced. Therefore, departmental number was entered in sequence. whereas a hierarchical grouping of ..work experience .he.date of the. change was not recorded, a was used, there.'was, no .important uncertainty as to was 'made out every .4 or 6 years.' Therefore, which department an individual belonged. eriod when an: employee worked in a specific . Finally, a direct comparison was made between -men1 .was known, and the actual .year of entry into -the' department could be estimated. employees in departments with an excess of a specific cancer and employees in residual departments. The Prior to 1933;-no-- departmental information was observed numbers of cancer among,employees in se- available from union records. All ihat was generally lected departments were distributed according to char- available from company records was the service date, acteristics of age and time. T h e numbers expected that is. the year of employment adjusted for layoffs. In among these employees were computed on the basis of this analysis, the years between the service date and the age-specific rate of cancer,in the group of residual 1933 were assumed to be spent in the same department employees. These comparisons are illustrated in table that the employee was in when the union was organ- 2. ized in 1933. This probably is a reasonable approximation: Prior to 1952 transfers from one plant division RESULTS to another were uncommon, and consequently the Stomach and Intestinal Cancer opportunity to transfer from one department to an- other was. limited. As seen in table 1, stomach cancer (ICD code 151, 7th TABLE l.-Mortality and mm-biddy from cancer of the stumueh or intestine acurrding b work area Work area and minimum years in area' Rubber making,' So5l.+id YtiFres/track, E+ Yr Residual Total I No.of pernub 718 ' 307 12,545 13,570 Reported No. of deaths' Cumulative No. of casesd Observed Expected' Total cases Standardized rate' Rate ratio Stomach Intestine Stomach Intestine Stomach Intestine Stomach Intestine Stomach Intestine 12 13 5.7 6.5 13 17 63 (18) 78 (19) 2.2 2.0 4 8 2.1 3.0 4- 9 41 (20) 89 (30) 1.4 2.3 - -82 86 86.1 94.5 92 122 29 (3) 38 (3) 1.0 1.0 98 107 93.9 104.0 109 148 - c ' Employment in work areas is mutually exclusive and hierarchical from the top. * e No. of Deaths persons who worked at least the minimum number of occurring during the period January 1, 1940-June 30, years 1974. icn the area. _- Cases occurring during the period January 1. 1940-June 30. 1976. '' Calculated on the basis of U.S. mortality rates for white males. Rate/lOO.OOO persons/yr. Standardized by the direct method to the age-specific person-year distribution of all 13,570persons. V'alIunecsludanes par&es are compounding, SE. mixing. milling, and testing. ' J NATL CANCER INST VOL. 61. NO. 4. OCTOBER 1978 Cancer in Rubber Workers 1049 T ~ B L E2 . 4 b s e r v e d and expected cmes of stomach and intestine c u m e r .in selerled depnr-tmmrs. wcurdtn+jbo seltctmi chwartm$.ytic.v'' . ...------- / Characteristic Category -No. of cases among workers in rubber makingb No. of cases amonK workers in soiid tires/tracks* / M~ started working in department. yr yr started working in department NO. of yr worked in department Age at cancer occurrence, yr Yr .,f occurrence <35 35-44 245 <1925 1925-1939 2 1940 5- 14 15-24 2.25 <65 65-74 975 <1960 1960-1969 2 1970 Observed 13 15 2 3 20 7 11 11 8 10 11 9 6 16 8 Expected 6.7 4.5 3.2 3.9 7.4 3.0 5.8 4.7 3.8 5.8 4.9 3.6 5.6 5.5 3.2 Observed 5 2 6 5 :3 5 7 1 5 2 5 6 4 5 4 Expected 2.2 1.9 2.2 1.6 1.3 3.4 3.8 0.9 1.6 2.6 2.0 1.7 2.2 2.5 1.6 * Expected cases were calculated on the basis of age-specific morbidity rates for residual employees, as defined in table 1. b Minimum of 5 yr in work area. 1 revision) was increased i n men who worked at least 5 years in rubber making (compounding. mixing. milling, and testing laboratories). Intestinal cancer (ICD 152. 153) was increased in Inen w h o worked at least 5 yeat in rubber making and in those who worked at leahi 3 years in solid tiredtracks. As seen in table 2, the csct'ss of cancers of the stomach and intestine among men who worked at least 5 years in rubber making occurred primarily in those who started working before age 45, who started working after 1925, and who developed cancer since 1959. For men who worked at least 5 years in solid tiredtracks, the excess was seen onlv ai age 65 and above. Pancreas Cancer Pancreas cancer (ICI) 157) was increased in t w o dishimilar departments-elevators and tire curing (table 3). T h e age-standardized rates in these departments were, respectively, 3.0 and 2.5 times higher than in men who did not work at least 5 years in one of these depatm e n is. Lung Cancer Excess lung cancer (ICD 162. 163) was seen in three deii;;, [mental groupings: tire curing, tire molds, and h e 1 cells/deicers (table 3). T h e excess lung cancer orcutred onlv in men who worked at least 5 vears in started working there prior to 1940. T h e predominant excess of lung cancer in these men occurred under age 65 (30 observed, 17.6 expected), before 1970 (30 observed. 16.2 expected), and in men 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 who 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 production as well as tire assembly). In the previous study (I), men who worked in warehouse/shipping .had the ereatest excess of bladder cancer. In the data Dresented . .: +' YO50 Monson and Fine Work area and minimum years in arean Elevators, 5+ Tire curing, 5 + Residual Total Tire curing, 5 + Tire molds, 5 + Fuel cells/deicers, 5+ Fuel cells/deicers, 0-4 Residual Total persons * Observed Expected' 259 660 12,651 13,570 661 272 1.139 1,051 10,447 13,570 Pancreas cancer 5 6 42 53 Lung cancer 26 9 23 20 156 234 20 36 54 7 60.3 15.0 5.7 20.0 12.8 199.6 253.1 TrihI CHI s .6 8 52 66 31 10 26 20 196 283 . -._ 47 (20) 41 (15) 16 (23 1_ -._ _ _ I" " __. 3 -_c {I 25 ---1 li 150 (27) 136 (43) 97 (20) 134 (34) 69-( 5 ) -z. 2.2 20 14 Ir4 -i il Prostate gland cancer Material conservation, 25+ Final finish, 2 5 t Machine maintainance, 5+ Machine maintainance, 0-4 Residual Total Chemical, O+ Tire building, 5+ Raw material warehouse/shipping, O+ Finished goods warehouse, O+ Residual Total 28 88 846 402 12,206 13,570 784 1,969 513 445 9,859 13.570 4 4 7 1 66 82 Bladder cancer 2 7 4 4 31 48 0.4 1.2 6.8 2.0 78 6 89.0 1.2 5.3 1.7 1.5 29.8 39.5 4 274 (136) 7.6 4 88 (46) 2.4 15 59 (15) 1.6 7 75 (28) 2.1 111 141 36-(3) -1 0 -- 6 61 (25) 25 16 36 ( 9 ) 1.5 4 26 (13) 1.1 5 36 (16) 1.5 64 95 24-( 3 ) -1.0 Skin cancer Tire assembly, 5+ Residual Total 1,299 2 1.8 12 47.0 (14.1) 6.5 -12,271 13,570 7 9 15.2 17.0 23 35 7.2 (1.5) -1.0 Tire assembly, 5+ Residual Total 1,299 12,271 13,570 Brain cancer 7 13 20 4.3 20.8 25.1 .~ 8 22.2 (7.9) -L 17 25 5.4-(1.3) -1.0 Lymphatic cancer Tire building, 5 t Residual Total 1,969 11,601 13.570 6 15 21 Leukemia 2.3 18.9 21.2 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, O+ Residual Total 316 42 1 1,957 252 339 280 10,005 13,570 4 5 7 3 4 4 28 55 1.5 8 57 (21) 36 1.8 8 50 (18) r,l 6.1 12 26 ( 7 ) 1.2 4 46 (29) 'r 1.3 4 40 (20) 2.5 0.9 4 55 (28) 3.5 -30.2 43.0 38 78 16-( 3 ) 1.0 Employment in work areas is mutually exclusive and hierarchical from the top. No. of persons who worked a t least the minimum number of years in the area. ' Deaths occurring during the period January 1, 1940-June 30, 1974. 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 persons, Values i n parentheses are sE. area where the components of the tire are put together. Most of the skin cancers were of the squamous cell type and 4 were fatal. Since skin cancer is usuall) not J NATL CANCER INST fatal, most of the skin cancer was ascertained in lilt' hospital tumor registry review, which covered [hf period 1964-1974. T h e excess occurred mainly in men VOL. 61, NO. 4, OCTOBER 19i8 K Cancer in Rubber .Workers *,bo worked at least 25 years in tire assembly (8 searching process used. T o the extent that these pat- observed. 0.9 expected). terns are in accord with knowledge of exposure pat- terns, inferences as to causality may be made. I Gastrointestinal Cancer Bra111 cancer (ICD 193) was seen to excess in men ,,+o worked in tire assembly (table 3). It occurred only T h e excess of cancers of the stomach and the in men under the age of 65 (8 observed, 1.3 expected) intestines among men who worked in processing tends u,j in those who started working after 1925 (8 ob- to support causal association. Excesses-of these Cancers grved, 1.8 expected). Brain cancer was seen mainly in have been reported in other studies of rubber workers men who worked less than 15 years in the department (5-7). These excesses also tended to occur in areas (7 observed, 1.4 expected). where the ingredients of rubber are compounded and mixed (8-101. Lymphatic Cancer and Leukemla Tradiiionally, the processing area has been dusty, with a large fraction of the nonrespirable airborne L; liphatic tumors (ICD 200, 202) were seen to excess particulates likely to be trapped on the surface of the in men who worked at least 5 years in tire building respiratory tract and eventually swallowed. Following @le 3). Leukemia (ICD 204) was seen to excess in are several compounds that should be considered as the men who worked in six different departments. Except agents responsible for the excess stomach and intestinal for tire building, the rate for leukemia in each of these cancer. departments was at least 2.5 times the rate in the Carbon black-Carbon blacks were introduced into residual workers. the rubber industry during World War I. Three com- These two diagnostic categories were grouped in mon types ofcarbon blacks have been used: 1) channel further analyses. An association of interest is with the black (average particle diameter, 5-30 nm), 2) furnace pear that work in the department started. For men black (30-80 nm), and 3) thermal black (120-150 nm). whc \tarted working after 1945, no excess leukemia or T h e furnace type is the most common. Many furnace lymphatic cancer was seen (4 observed, 4.5 expected). blacks have surface-adsorbed PAH that can be extracted Also. only a slight excess was seen in men who worked by organic solvents (11).Some of these adsorbed PAH less than 15 years in one of these departments (10 have been shown to be carcinogenic and mutagenic in observed, 8.2 expected). animals or bacterial test systems (11- 15). Whereas The specific diagnosis of the leukemias or lymphatic current exposure to carbon black rarely exceeds 1 tumors among the men who worked in one of the mg/m3 (mass respirable), past exposures were probably departments specified in table 3 were: lymphosarcoma, higher, inasmuch as the threshold level is 3 mg/m' 9 cases; reticulum cell sarcoma, 1 case; malignant (16). In one study of workers exposed to carbon black lymphoma. 1; lymphatic leukemia, 19; myeloid leukemia, 15; monocytic leukemia, 2; and other and unywcified leukemia, 4. 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 DISCUSSION rubber compounds. Many are petroleum or coal tar In analyLing these data, we relied heavily upon searching for associations between specific cancers and work in departments in which specific substances were used. We grouped such departments when consistent associations were seen. This strategy was used because oI the complexity of the work patterns within the plant and because of general uncertainty as to the nature of the halard of working in the rubber industry. This strategy requires cautious interpretation of any association. To judge whethw any cancer-department associa- tion is likely to be causal, independent data must be evaluated. Such data include other studies of mortality and morbidity among human populations and toxicologic studies on animals. Also, internal consistency in the data can be used. If products (18).Processing oils, common softeners, contain modest amounts of PAH. Other compounds used as softeners or plasticizers include coal tars, asphaltum fluxes,6 and petroleum-derived waxes. Coal tars have been suspected of causing a wide range of human cancers (IQ A n t i o x i t a n f s and accelerators.-Several of these agents are suspected of being carcinogenic on the basis of animal studies (A), of forming carcinogenic metabolites (B), or of being mutagenic in bacterial systems (C) (20-23): antioxidants-4-isopropoxydiphenylamine (A), N , N-diphenyl-+r>henylene diamine (C), PBNA , iB), and sy&2/3-naphihyl-&phenylene (C); tors-2-mercaptobenzothiazole (A). N-oxydiet benzothiazole (A), hexamethylenetetramin excesses of a specific cancer are found in departments that have a common exposure, it seems reasonable to consider the Dossibilitv that the association is causal. In the analysis in.,which the cancer morbidity rates in one. recent:.: study ;of :rubber workers, . n o -excess of .bladder,,cancer...was.: found , ( 5 ) .!e !, ;f ~ ;.---. ; T h e ' ek&s--of bladder cancer in chemi'l:. workers is relatively ' small. T w o of. the ' men ' worked only for 1 year in the chemical plant. However; two others worked for at least 15 years with th? PBNA autoclave; . ....._ therefore, a causal connection must be seriously considered. (A third man who worked with PBNA lrom i 1952 to .1962 died from bladder cancer on October 6, men who worlcIin tire 1976.) BNA.or one of its metabolites is the substance rge numbers: .pi.- similar believed to have'-.caused bladder cancer in rubber has been reported. (6). workers in earlier.studies. PBNA has been demon- increased death rates strated to metabolize to BNA in the body (22). eported an increase in dity-among current curing workers in Skin Cancer and Braln Cancer ' (25).. In the curing area, the likely ts of the curing fume.. Excesses of cancers of- the skin and brain were latihation of the basic observed among men who worked in tire assenbly tires. T h e major constituents are departments. Both types of cancers have large rate ntioxidants,' accelerators, and low- ratios: 6.5 and 4.1, respectively. Most of the skin boiling constituents of softeners (26). T h e amount of cancers were of the basal cell or squamous types and .. I PAH i n the'curing fume would not be great because of I their h-_igh boiling points. Another possible exposure were located predominantly on the neck and head. The skin cancer excess occurred in men who started work- was to talc;-which was used to dust some types of tires. ing before 1940, whereas the brain cancer excess was An excess of lung cancer has been reported in talc present in men who started working after 1940. miners (27). Few unique exposures were noted in this area. One T h e excess of lung cancer in men who work in the possibility was carbon tetrachloride, a potent animal .:...,.-- tire molds area is small. This is a standard metal machining shop and the only likely adverse exposure is carcinogen (33). This solvent was added to ()!her solvents to reduce flammability. T w o exposures m,: be to cutting oils. Nitrosamines. which are animal car- related to the excess skin cancer. One is exposure to rhe cinogens, are present in cutting oils (28). However, no drum resins, which contained coal tars and which have excess of lung cancer was seen in a study of exposure been associated with skin cancer in other industries to' cutting oils (29). -- (19). T h e second is exposure to the accelerator hexa- The data on lung cancer in men who worked in fuel methylenetetramine, a suspected animal carcinogen cells/deicers is unusual in that the excess was seen that has been described as a common cause of derrna- mainly in men .who worked a relatively short time. titis among tire builders (21, 34). This is not surprising. inasmuch as employment in .. . . .I this department occurred largely during World War 11. 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 (30). Prostate Gland Cancer ._ Excesses of prostate gland cancer among all rubber workers have been reported (5, 7). T h e 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 enI gineering shop; the most likely causal exposure would and adhesives, particularly those for use in bonding .. . I _. VOL. 61. NO. 4, OCTOBER 1978 Cancer in Rubber Workers metal to rubber, and to some repair or patching cements. The most common solvents used in this conlpany were refined petroleum solvents, principally hiai: .:est gasoline and varnish maker's naphtha. All refii. cl petroleum solvents are complex mixtures of h!&.ocarbons and contain a low percentage of benzene. .\nv substance responsible for the excess of leukemia or 1. 1 , ~ ~ p h a t iccancer is believed to have been removed or *&red in the work environment, inasmuch as men ,,ho started work after 1945 do not have an excess rate these diseases. For two other reasons, we hesitate to attribute the excess of leukemia solely to benzene. First, the predomin;lnt leukemia was lymphatic. Epidemiologic evidence [a: ;I association between benzene and lymphatic letik nia is less convincing than the evidence for an as50c-iatioriwith other leukemias (36, 37). Second, one of the areas. with excess leukemia deaths also has an excess of lymphosarcoma, a tumor not known to be associated with benzene. In summary, several associations between work area arid specific sites of cancer are likely to be causal. These are the association of gastrointestinal cancer with the processing area, lung cancer with curing, Icukrrnia with extensive organic solvent exposures, and cnii - w of the skin and other sites with the tire aswiibly area. Fortunately, many of these associations no longer hold for workers who started jobs after 1940. Whether specific chemicals can be identified as having k e n responsible is problematic because of the complex nature of the work environment. T h e only realis(IC approach to prevention must be based on a general reduction in exposure to substances used in h e manufacture of rubber products. REFERENCES ( 1 ) , M M O N S ~RNR. NAKANOKK: ,Mortality among rubber workers. I. White male union employees in Akron. Ohio. Am J Epidemiol 103:284-296, 1976 ( 2 ) -: Mortality among rubber workers. 11. Other employees. Am J Epidemiol 103:297-303, 1976 ( 3 ) MONSONRR: Analysis ot relative survival and proportional mortality. Comput Biomed Res 7:325-332. 1974 ( J ) D0t:RING CR, FORHESRL: Adjusted death rates. PTOCNail Acad Sci USA 25:461-467. 1939 ( $ 1 '-!(;.MK:IIAEIA. J. SPrR'r,\S R. K I P P E R LL: An epidemiologic ,tudy of mortality within a cohort of rubber workers. 19641972. J Occup iMed 16:458-464, 1974 ( 6 ) Fox AJ, C:ot.[.ik.R PF: A survey of occupational cancer in the rubber and cablemaking industries: Analysis of deaths occurring in 1972-74. Br J Ind Med 33249-264. 1976 (7) z ~ N n j t : t . w v i c : i tD, T.wt.wEJ , SYMONS M: Mortaliiy experience of a cohort of rubber workers, 1964-1973. J Occup Med 1 8 387-394, 1976 ( 8 ) M(;Mi<:tx,wi.AJ. SPtRrJ\sR. G.\MHI.LJ:F, et al: hlortality among tubber workers: Relationship to specific jobs. J Occup Med 18:178-185, 1976 ( 9 , A~njc~.aovic:D~.r Txut.x~:rJ:, SVMONMS , el al: Mortality of rubber workers with reference to work experience. J Occup &led 19597-405. 1977 (10, :$f.\Xc:trso TF: Epidemiological investigation of occupational cancers in the rubber industry, In The New Multinational Health Hazards (Levinson C, ed). Geneva: International Chemical Federation, 1975, pp 80-136 (11) N.\tl <:A, Nt..\t, J , SI'E,LIRRIVI)AC: LA study of the physiological effects of carbon black. 1. Ingestion. Arch Ind Health 1721- 28. 1958 12) NE.\[.J. T R I ~ : WNM: Isolation of a n unknown carcinogenic polycyclic hydro-carbon from caibon blacks. Health Lab Sci 9~32-38, 1972 1 3 ) Got,t>(1:C:arbon black adsorbates: Separation and identification of a carcinogen and some oxygenaied polyat-omatics. Anal Chem 47:1469-1472. I975 14) EIS~NSI.\IYEI . Cot.u A: C:).clopenta(c,d)pyrene: A highly muta- genic polycyclic aromatic hydrocaubon: Proc Nail Acad Sci Us11 78~1667-1669. 1978 (15) M(:(:.\NN J. C i r o i E. Y.\&i,\s,\idE. el a\: Deiecrion of carcinogens a\ mutagem in the Salmonella/micro~rnetest: Assay of 300 chemicals. Proc Natl Acad Sci US,\ 72:5135-5139. 1975 (26) M(.C:ORAII(.KW E : Environmental Health Contiol for the rubber indubtry. Rubber (:hem Techno1 44512-530. 1971 ( I 7) IN<..\I.L.S TH. R I S ~ ~ ~ ~ . ~ . I R I H ,R\ R: RPIe;r.ioNdic \earth for cancer in the carbon black industry. ,\ich Environ Health 2:429-433. 1961 ( I B ) B. F. (hodrich Rubbet Company: Manual of RubbeI Manufac- tiire. ,\kron: B. F. h o d r i c h Rubber <:o., 1933. p 181 (19) Certain polycyclic aromatic hydrocarbons and heterocyclic com- pounds. [ARC: Monogr Eva1 <:arcinog Risk <:hem Man 3:25- 29, 1973 (20) Bionetics Reseach Labs. Inc: E~~a111atio1f)ncarcinosenic. teratci- genic, and mutagenic activities o f w1tr.te.d pesticides and in- diistrial chemicalh. v o l . I. Carcinogenic scudy. Kensington, .Md.: Bionetics Research Labs. Inc.. pp 66. 86-87. 1968 (22) National Institute of Occupational Safety and kkdlth: Suspecred <;arcinogens. 2d ed. Wahhington. 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J O c c q Med i6345-349. 1974 (28) FINKI.t..\ JF: Nitrosamines in ctitling fluids. In (:titrent Intelli- gence Biillerin. Rockville, Md: NIOSH. October 6. 1926 (29) l k : o t ' f f i i . E P: cancer mortality among workei-b e x ~ x ) w Jt o cut- ting oil mist. Ann NY Acad Sci 271:94-101. 1976 (30) CER3.i M. KYPENOV.\ H: Mutagenic activity o f chloroethylene\ analywd by xlreening \piern tests. Mural Res 46214-215. 1977 ( 3 1 ) L ~ h t t NR A , Lt.t; JS, W.\(;ONI;RJ K . ei al: Cancer mortality among cadmium pi-oducrion worker>. Ann N Y hcad Sci 27 I: 213-279. 1976 (32) L\SERA. H.\SKF.RME: Tumors of the urinaty bladder as a n oc- cupational disease in the riibber industry. Br J Prev Soc Med 839-50, 1954 (33) WE~SBERCXERK. Carcinogenicity studies of halogenated hydro- carbons. Environ Health Perspect 21:7-16. 1977 (34) KOHER GM. H.\YIItvtsI' ER: Poisonings in the rubber industry. In Industrial Health. Philadelphia: P. Blakiston, 1924. pp 535-545 (35) M(:M~(:it.i~.At.J. SPIRI'.\SR. KI'PPLR LL: Solvent exposure and ' - leukemia among rubber workers: An epidemiologic srudy. J Occup Med 17234-239. 1974 (36) VlGt.l.\NI E<:: Leukemia ahbociated with benrene exposure. Ann NY Acad Sci 271:143-151. 1976 (37) INF,\NI'b: PF, RINSKYRA, W.K;ONER JK. et al: Leukemia in ben- zene workers. Lancet 2:76-78. 1977 VOL. 61. NO. 4. OCTOBER 1978 J NATL CANCER INST