Document jyDM6GxJBBGoVGY3jp8da6bNy

Castleman File: American Petroleum Institute w/c = with cover letter or memo If DATE = 0, undated CD-ROM Document #:API DATE published article from trade journal published advertisements newspaper article published government report government inspection results unpublished or internal report unpublished presentation from conference letter memorandum industry warning labels industry sales literature industry recommended practices meeting minutes (with attachments) membership list BC notes LJttSArt * 4NK. MICAS PHRULfcUM iNSTiWTI API 04607 I. I API HISTORY OF THE 1 SUBCOMMITTEE ! ON CARCINOGENICITY I9A5-I950 * i i API 04608 s^ ^ For x.u'onnation Only - Mot for Publication c A contribution of information to Members of API Medical Advisory Committee. 6-13-45. ATTENTION Technical Memo No. 45-214 Chemical Division Socony-Vacuum Oil Co., Inc. Research and Development Laboratories Paulsboro, New Jersey April 27, 1945 Mr. P. V. Keyser, Jr. Dr. A. A. O'Kelly Dr. W. P. Hawthorne Carcinogenic Hydrocarbons, Literature Survey A brief literature survey of the cancer-producing hydrocarbons has been made as requested by Dr. L. C. Beard in his letter (W. M. Holaday/ P. V. Keyser, Jr.) of April 12, 1945. Carcinogenic activity has been noted in various types of compounds including hydrocarbons, amino, azo and nitro compounds, hormones, and in organic compounds. This report will be confined to the hydrocarbons and hydrocarbon fractions identified as carcinogenic. Most of the carcinogenic hydrocarbons were originally identified in the pyrolysis products of coal, wood, petroleum and shale. In some cases these hydrocarbons exist, as such, in the original materials. The active hydrocarbons are almost without eocception polynuclear aromatic hydrocarbons and are conveniently classified under the parent hydrocarbons from which they night be derived. Thus, the three main types are classified as benzopyrenes, cholanthrenes, and benzanthracenes. I Identified Carcinogenic Hydrocarbons (7),(22).(45),(24), (12),(10),(5),(28), (29),(38),(47) I. Benzopyrenes 1,2-benzopyrene 3,4-benzopyrene 1,2,3,4, dibenzopyrene II. Cholanthrenes cholanthrene 20-methjrl cholanthrene 16,20-dimethyl cholanthrene 20-ethyl cholanthrene 15,16-benzdehydrocholanthrene N ' -2- 20-isopropyl cholanthrene 3-methyl cholanthrene meso-dihydro cholanthrene 4-methyl cholanthrene 5-methyl cholanthrene meso-dihydro 3-methyl cholanthrene 1-kc-tochoianthrene III. Benzanthracenes 1,2-benzanthrac ene 10-methyl-l,2-benzanthracene 9-methyl-l,2-benzanthracene 5,10-dimethyl-l,2-benzanthracene 5.9-dimothyl 1,2-benzanthracene 8.9-dimethyl 1,2-benzanthracene 4.10-ace 1,2-benzanthracene 9.10-dimethyl 1,2-benzanthracene 6.10-ace 1,2-benzanthracene 10 ethyl 1,2-benzanthracene 5 methyl 1,2-benzanthracene 5 n-propyl 1,2-benzanthracene 6 methyl 1,2-benzanthracene 5.6 dimethyl 1,2-benzanthrr.cene 6 isopropyl 1,2-benzanthracene 6.7 cyclopenteno-1,2 benzanthracene 3 hydroxy-1,2-benzanthracene 3 methoxy-1,2-benzanthracene 5 propyl-9,10 dimethyl-1,2 benzanthracene 5 ethyl-9,10 dimethyl -1,2 benzanthracene 5 methyl-7,8 dihydro-1,2 benzanthracene 1.2.5.6 dibenzanthracene 11,9 methylene-1,2,5,6 dibenzanthracene 1 ' ,2;*,31 tetrahydro-1,2 benzanthracene 5.6 cyclopenteno-1,2 benzanthracene IV. Miscellaneous sym. triphenyl benzene tetra-phenyl methane o-amino-azotoluene 9,10 dimethyl anthracene 1,2 cyclopenteno-510-aceanthrene ) The Nature of Petroleum Carcinogens The probability that the carcinogenic hydrocarbons in petroleum are of the same nature as those listed above has been indicated by various workers. Roffo (43) found that the fractions of fuel oil boiling between 270-300C, and 300-330C, produced tumors in eighty percent of the rabbits to whose skin these fractions were applied, and the absorption spectra of these fractions were similar to those of known cancer-producing compounds. Spectrographic analysis of distillates of all fuel oils tested showed the presence of the sane class of hydrocarbons. Twort and Fulton (59) 3tate that oils with a preponderance of paraffins have relatively little API 04610 -3- carcinogenic activity, but that carcinogenesis is high in oils with a preponderance of isocyclic compounds, Pessano (41) found that some of the products of combustion in gasoline engines are in the group considered carcinogenic. Eats respiring the products of combustion of fuel oil at high concentration developed carcinoma of the lungs. The liquid products formed by combustion of petroleum, when applied to the skin of rabbits, produced malignant tumors. A substance containing the benzo (o<) pyrene nucleus, with decidedly cancorogenic properties, has been isolated (32) from tar such as is used in paving roads, Tjhe prevalence of cancer among paraffin workers has been shown (63) to be due to irritating impurities- present in the crude paraffin wax. The pure paraffin (C,,.H_.) has been tested and found to be non-carcinogenic. 24 50 The Most Carcinogenic Petroleum Fractions Carcinogenic hydrocarbons have been shown to be more or less concentrated in certain fractions of petroleum. In general, the higher boiling fractions (fuel oil, lubricating oil, tar, etc.) contain more carcinogenic hydrocarbons than the lower fractions. Two petroleum oils used in cotton spinning mills yielded high boiling fractions 31 times as carcinogenic as the low boiling fractions (58), The heavier grade lubricating oils are said to be less potent than the spindle oils (54). Shale oil was found (58) to be about 12 times as carcinogenic as petroleum-well oils; the most potent shale oil fraction being the unfinished lubricating oil from which most of the paraffin wax has been removed but which has not been treat ed with sulfuric acid or filtered (54), Wood (62) found that while mineral oil of the type used therapeutically was not carcinogenic, heavy lubricating oils did show some carcinogenicity, and tar showed the same property to a larger degree. Twort and Lyth (60) investigated a range of commercial distillates of a topped Borneo crude oil. They found that the peak carcinogenic activity was associated with the fraction having a viscosity of 200-225 centipoises at 25C, and that the whole range of oils showed biological activity. This activity had been predicted from an examination of the physical properties of the oils which were alone sufficient to condemn their use as lubricants when likely to eome into contact with the user. Evidence of the presence of carcinogens in cracked mineral oil was noted (56) in an investigation of the oily, tarry material extracted from the soot cf the expansion chamber of a high-ccmpression, internal-combustion engine. This material was highly carcinogenic to the skin of mice. In general, the carcinogenic potency of crude shale oils decreased as the cracking temperature wab lowered but was still present at 400Centigrade. These investigators also found that a heavy grade of Diesel fuel oil was carcinogenic but that a light grade oil was not. Effect of Treatment of Oils on Carcinogenicity V/oodhouse (64) found that the petroleum ether extract of pitch and the SO2 extract of spindle oil distillate from a paraffin-base crude were carcinogenic, Lyth (36) noted, during careful fractionation of API 04611 -4- Scottish shale oil and a Persian oil, that all samples of petroleum oil which were treated with ethanol provided residues of lower carcinogenicity and higher refractive index and density than the original oil. Twort and Fulton (59) found that saturation by oxidation and reduction cr treatment by silica gels or clay reduced the cancerogenic activity of their mineral oils probably through adsorption and polymerization. Alcohol extraction and sulfuric acid treatment reduced the carcinogenicity of the oils by extracting the carcinogens. The same authors also found that the active agents could be concentrated by extraction with methyl sulfite or methyl suifate and picric acid. They suggested the process for treating oil for industrial use. Relation of Carcinogenicity to Fluorescence and Chemical and Physical Properties Twort and Twcrt (54) found that the cancer-producing properties of mineral oils appeared to. be related to their flueroscence; oils having a blue fluorescence seemed more active than those having a green fluorescence. Weiss (61) noted that strong fluorescence was almost confined to conjugated ring systems which possessed highly mobile electrons. Only the more symmetrically conjugated systems cr those which do net give rise to strongly ionic structures show fluorescence. The author compared the mobile electrons with metallic electrons and stated that carcinogenic hydrocarbons belong to this group of hydrocarbons. -Hieger (26) found that the fluorescence spectra of many carcinogenic substances show bands at wave lengths cf 4000, 4180, and 4400AC. These bands are similar to those cf the spectra of 1,2-benzanthracene, a known carcinogen of high potency. A relationship between physical properties and carcinogenicity was observed by Lyth (35) who stated that oils with a refractive index less than 1.5500 were non-toxic while oils with an index exceeding 1.5600 were highly toxic; Pennsylvania oils and certain mildly treated oils were an exception. The same author noted a relationship between the iodine value of untreated oils and carcinogenicity. Toxicity increased in the same order as the iodine value, Pennsylvania oils again excepted. Fieser and Hershberg (21) found that the behavior of polynuclear hydrocarbons in lead acetate oxidation, aldehyde reaction, and diazo-coupling indicated that the most carcinogenic hydrocarbons of the series tested possessed special susceptibility to substitution. Schmidt (48) discussed the theory of the box model of aromatic compounds and stated that the theory is especially successful in character izing the cancer-producing hydrocarbons as compounds with abnormally high electro gen density and low excitation energy. Other references relating structure and physical and chemical properties to carcinogenicity include Bradley (8); Clar (12); Dunlap and Warren (18); Fieser (19) and (20); Fieser and Campbell (22); Iball (28); Kennaway et al,, (29); Lundgren (34); Shear et al., (51); and Truhaut (53) More general references to known carcinogens, including reviews of the literature up to the date of the reference, are Addiaall (1); Andervont (2); Barry (3); Blanc (4); Boyland (5) .and (6); Brady (9); Bruce and Kahn (10); But&nandt (11); Cook (13) and (14); Cook et al., (16); Cook and Kennaway (15) and (17); Hartwell (24); Kewett (25); Kemack (30); API 04612 -5- Kirby^(31); Morton et al., (39); Roffo (42); Rondoni (44); Sampey (45); Sannie and Truhaut (46); Sasaki and Yoshida (47)} Schurch (49); Shabad (50); and Siboni (52). The greater part of the original references were unavailable and so were quoted directly from chemical abstracts. For these references the chemical abstract reference is listed in parentheses after the original reference in the bibliography. LJHjRMW /s/ L. J. Hillenbrand L. J. Hillenbrand BIBLIOGRAPHY .1. Addinall, C. R., Merck Report 44, 16-18(1935) (C.A.29,6203?) 2 Anaervont, H. B., Univ. Vfisconsin, Symposium on Cancer Sept, 1936. 54-66 (C.A.32,3612s) 3. Barry, G., et al., Proc. Roy. Soc. HL17. 318-51(1935) (C.A.29,51873) 4. Blanc, Thesis for degree Dr. of Pharmacy, Besancon 1936 (C.A.31.156^) .5. Boyland, E., Nature 130, 274-5(1932) (C.A.26,558l3) 6 Boyland, E, Am. Rev. Bicchem. 4,469-78(1935) (C.a.2^,51803) 7. Bradbury, J. T., et al., Cancer"Research 1, 635-94(1941) (C.A.25,8065^) 3. Bradley, W., Nature 137, 404-5(1936) (C./"^0,38783) .9. Brady, 0. L., Science Progress 28, 100-7(1933) (C.A.27,4217^) 10 Bruce, Y<. F., and Kahn, S. J., J. Am. Chem. Soc. 60, 1017-19 (1938) (C.A.32,4979) .11 3utenandt, A., *rch. exptl. path, pharm. 190, 74-91(1938) (C.A.^2,7372s) .12 Clar, E., iiromatische Kohlenwasserstoffe, Polycyclische Systeme, 65-73, Berlin, Springer-Verlag 1941 13. Cook, J. V/., Yale J. Biol. Med. 11, 1-13(1938) (C.*.22,221*) 14. Cook, J. W., Nature 145, 335-8(1940) , 15. Cook, J. W., and Kennaway, E. L., Am. J. Cancer 21, 50-97(1938) . (C.A.32,67313) 16 Cock, J. W., et al., Am. J. Cancer 29, 219-59(1937) (C.a.31,3982s) 17. Cook, J, W., and Kennaway, E. L., Am. J. Cancer 39, 381-428, 521-32(1940) (C.A.35,1053s) 13. Dunlap, C. E., and Warren, S., Cancer Research 1, 953-4(1941) (C.A.26,10825) " ' .19. Fieser, L. F., Am. J. Cancer J34, 37-124(1938) (C.A.H,1387s) 20 Fieser, L. F,, Univ. Penna. Bicentennial Ccnf. on Cause and Growth of ,. Cancer 1941, 1-27(C.A.15,8072s) 21 Fioser, L. F., and Hershberg, E. B., J. Am. Chem. Soc, 60, 2542-8(1938) 22 Fieser, L. F., and Campbell, W. P., J. Am. Chem. Soc. 60, 1142-5(1938) 23. Haddow, A., and Robinson, A. M., Proc. Roy. Soc. 3127, 227-87(1939) (C.A.33,6428^) 24. Hartwell, J. L., Nat. Cancer. Inst,, U. S. Public Health Service (1941) 25. Hewett, C. L., Current Science 5,527-30(1937) (C.A.31,5036^) 26. Hieger, I., Biochem. J. 24, 505^11(1930) (C.A.24,53691) 27. Hirst, H. R., and King, A. T., Nature 130, 578 and 810(1932) 28. Iball, J., Z. Krist. 9, 7-21(1936) (C.A.20,7412s) 29. Kennaway, E. L., et al., Cancer Research 2, 157-9(1942) (C.a.35,3250s) 30. Kermack, W. 0., Science Progress 28, 115-23(1933) (C.A.27,425o3) 31. Kirby, a. H, M., Nature 154. 668-9(1944) (C.A.29,976*) 32. Kling, A., at al., Bull. Acad. Med. 120, 130-43Tl938) (C.A.23,87795) 33. Luden, G., Can. Med. assoc. J. 17, 43-8 (1927) (C.A. 21, 956?-) 34. Lundgreri, H. P., Science 82, 130-3 (1935) (C.A. 29, 6611?) 35. Lyth, R., J. Ind. Hyg. 15 to4, 226-37 (1933) (C.A. 27, 51103) 36. Lyth, R., Nature 139. 374 (1937) (C.A. 2i> 4099?) 37. Lyth, R., and Twort, C.C., J. Hyg. 2> 269-72 (1938) (C.A. 32, 63238) 38. Morton, A. A., ot al., Science 82, 134 (1935) (C.A. 29, 6642) 39. Merten, A. A., et al., Am. J. Cancer, 26, 755-60 (1936) (C.A. 22> 5291''') 40. Nyrcp, J. E., Prctcplasma 1, 294-300 (1932) (C.A. 27, 29932) u. Pessano, J. E., Semana Med. (Buenos Aires) 1942 II, 210-14 (C.A. J7, 677) 42. Roffo, A. H., Neoplasmes 11, 77-89 (1932) (C.A. 26, 51452) 43. Rcffo, H., Bol. Inst. Med. Exptl. Estud. Cancer 17, 385-414 (1940) (C.A. 35, 14992) , 44. Rondcni, P., Chimica e Industria (Italy) 17, 148-54 (1935) (C.A. 29, 5176) API 04614 T (BIBLIOGRAPHY - CONTINUED) 45. Sampey, J. R., Cher.. Ed. 16, 461-6 (1939) 4b. Sannie, C., and Truhaut, R., Bull. asscc. Franc etude Cancer 23, 6-37 (1934) (C.A. 30, 52902) 47. Sasaki, T., ar.i Ycshida, T., Bull. rtsscc. Franc etude Cancer 24, 534-B (1935) (C.A. 30, 52904) 46. Schmidt, 0., Bor. 73A, 97-116 (1940) 49. Schurch, 0., and Winterstein, A., Z. Physicl. Chem. 236, 79-91 (1935) (C.A. 29, 81047) 50. Shaba.i, L. U., Arch. 3ci. Biel. (USSR) 22, 147-68 (1935) (C.n. 22, 56449) 51. Shear, M. J., et al., J. Nat. Cancer Inst. 1, 303-36 (C.n. 22* 44752'3) 52. Sibcni, R., Bell. chia. farm. 74, 709-20 (1935) (C.A, 22, 52B69) 53. Truhaut, R., Chiraie et Industrie 22, 419-32 (1938) (C.A. 22, 46521) 54. Twcrt, C. C., and Twort, J. U., J. Ind. Hyg. 13, 204-26 (1931) (C.n. 25, 52053) 55. Twcrt, C. C., and Twcrt, J. Li., Lancet 19341, 286-7 (C.A. 28, 5878^) 56. Twcrt, C. C., and Twcrt, J. a., Lancet 1935 II, 1226-8 (C.a. 22, 22555) 57. Twcrt, C. C., and Twort, J. U., Oil Colcur Trades J. 94, 251-5 (1938) .(C.A. 32, 79947) 5G. Twort, C. C., and Ing. H. R., Z. Krebsfcrsch 27, 308-51 (1928) ..(C.A. 23, 1972) 59. Twort, C. C,, and Fultcri, J. D., Z Krebeforsch 21, 543-73 (1932) (C.A. 26, 35755) 60. Twcrt, J. M., and Lyth, R., J. Hyg. 22, 161-9 (1939) (C.A. 22, 5C619) 61. Weiss, J., Nature 145, 744-5 (1940) 62. Weed, F. C., J. Am. lied, asscc. 94, 1641-3 (1930) (C.A. 24,48672) 63. Wocd, H. B., J. Cancer Research 13. 97-102 (1929) (C.A. 22, 3272?) 64. Wcodhouse, D. L., J. Inst. Petr. Tech, 20, 1057-63 (1934) (C.A. 29, 12369) i I ! I API 04615 Literature Review April 30, 1945 Library of the Technical & Research Division The Texas Company New York City I NOTE In view cf the immense amount of published information on various p'noses cf the cancer problem it should be emphasized that this literature review gives only a rapid survey cf developments in the field of cancer research as applied directly tc the petroleum, coal tar, oil shale and allied industries. While it is far from being complete, yet it is believed that most of the important work in this particular field has been covered, either in the report itself or in one cf the bibliographical references given in the appendix and referred tc at the bottom of page 1. M. P. Doss API 04617 THE CARCINOGENICITY OF BITUiUNOUS COMPOUNDS It has long been recognized that the incidence of skin cancer i3 greater among workers in certain industries and occupations than among the population as a whole. Attention was first directed in 1787 to the very high death rate result ing from scrotal cancer of chimney sweeps; it is eight times more common in these workers than in the general public in England, and in the United States the ratio cf cancer cases in chimney sweeps is double that of the general population^. In practically all cases it is the scrotum that is attacked; this is also the site in mule spinners cancer discussed later, Workers in ether industries coming into direct contact with tars, pitches, shale oils, etc. likewise shew a high incidence cf skin cancer, for example, laborers in plants making briquettes, tar reefing, wood preservatives, artificial gas, insulating compounds, shale products, etc. However, in spite cf the recognition of the fact that bituminous com pounds were apparently the cause cf skin cancer, it was- not until relatively recently that skin cancer was produced in laboratory animals by direct application cf tar. This was accomplished by the Japanese investigators Yamigawa and Ichikawal22 in 1915. Since then a great deal cf very careful work has been done in synthesizing and testing various organic compounds, particularly polycyclic aydrocarbons and derivatives. For lengthy reviews of this work, see References 8-12, 14, 17, 20, 22, 23, 26-29, 32-34, 74, and 87j particularly the review by J. L. Hartwell cf the National Cancer Institute covering 696 chemical substances, cf which 169 are reported to be carcinogenic^-. L. F. Fieser summarizes cur knowledge in this field as follows^; "As judged by all available data for the production cf skin and subcutaneous tumors in rats and mice, methylchclanthrene probably is the most potent cf the known chemical carcinogens. Systematic studies cf synthetic model compounds have shewn that the methyl group is cf nc importance tc the functioning cf the compound; . . that much, if net all of the efficacy of cholanthrene is retained in the analogous hydrocarbon 5,10-dimethyl-1,2-benzanthracene; and that the most significent structural feature <f cholanthrene or methylcholanthrene is the 1,2-benzanthracene ring system with a I -2- carbon substituent at the meso position 10, 10-Methyl-l, 2-benzanthracene evokes sarcomas in mice nearly as rapidly as methylcholanthrene, and, though it is distinctly less effective in the production of skin cancer, the substance constitutes the nearest approach in a simple model compound to a simulation of the biological properties of the hydrocarbon of more complicated structure. "All twelve possible monomethyl derivatives of the inactive 1, 2-benzanthracene have been synthesized rand tested for carcino genic .activity, and of these the 10-isomer is the most potent. The meso-substituted 9-methyl compound stands next in order of potency, followed closely by the 5-methyl derivative, which produced sarcomas in mice with a latent period about twice as long as that observed with 10-methyl-l,2-benzanthracene, Methylcholanthrene and benzpyrene can be regarded as 1, 2-benzanthracenes substituted at the meso positions 10 and 9, respectively, and in model compounds the combination of the two types of substitution is particularly favorable, 9,10-Dimethyl1,2-benzanthracene produced skin tumors in mice with remarkable rapidity and in this test surpasses methylcholanthrene in speed of action, though it is less effective when administered by subcutaneous injection. The thiophene isologue of the hydro carbon has comparable properties." Numerous attempts have been made to isolate the definite carcinogenic compounds in coal tar by means of distillation, solvent extraction, etc.73# but while very potent fractions have been obtained, the individual compounds have been difficult to separate. Kennaway and Hieger ^ proved the carcinogenicity cf 1,2,5,6-dibenzanthracene, the first pure carcinogenic hydrocarbon known. Ccck, Hieger and Hewitt ^4 in 1933 isolated 1,2-benzpyrene, 4,5-benzpyrene and 1,2-benzanthracene and estimated that the original coal tar pitch contained not 1-jss than 0.003% of the potent 1,2-benzpyrene. Several investigators 22, 24, 25 have attempted to correlate carcino genesis with fluorescence. For example, the cancer-producing material formed by the action of AlCl^ on tetrahydronaphthalene shows a blue-violet fluorescence, shewing three bands, 4000, 4180 and 4400 A.U., which are similar to the fluorescence spectrum of 1,2-benzanthracene 44, Kennaway and Hieger &2 suggest the possibility of the use of the fluorescence spectrum for-the preliminary ^^oaination of materials suspected of being carcinogenic. API 04619 -3- An important fact brought out by several investigators is that the temp-arature to which a tar, shale oil or petroleum oil has been subjected determines its carcinogenic activity. In general, it would seem that temperatures up to 500C. are without effect 52 but above that temperature carcinogens are formed, the maximum yield lying between 80C and 900C. 53, 59, Tar and pitch from gas works are far more active than that from coke ovens 58^ accounting for 70# of all cases of tar cancer in the United States while the coke oven product causes only 5# While petroleum residues resulting from moderate heat treatment are inactive 120^ yet by passing an inactive California petroleum through a tube at 380C. Kennaway and Leitch obtained a very active carcinogen 59, 60# Even an inactive medicinal paraffin oil heated to 330C. under 50 atms. pressure acquired some carcinogenic activity 1^1, Kennaway ^ likewise obtained an active material by passing isoprene through a tube filled with and heated to 820C. Watson H5 achieved similar results with turpentine at 850C, Acetylene yields an active product on being passed through a red hot tube 59 but it must be pointed out that treatment with AlCl^ at room temperature also produces an active compound ^1. On the other hand, synthetic lubricating oils produced by AICI3 polymerization at temperatures up to 150C. were entirely inactive 121. It is suggested that the condensation products of acetylene are of a more complicated nature and probably more unsaturated than those obtained from ethylene. The carcinogenic activity of tars depends apparently not only on the temperatures of their formation but also on the chemical compound used as the base stock 1^, For example, a tar made from pinene at 850C. was far more active than one from turpentine made similarly, the relative potencies being 100:19. Pinene tar3 made at 500, 600, 750, 850 and 950C. had relative potencies -hr cf 0, 12, 21, 100 and 6k. Oxidation of a synthetic tar at 100C. reduced its potency from 100 to 63, and at 150-160C. its potency fell to 0. Oxidation with an acetone solution of KMnC^ reduced the potency to 24; with pyridine as a solvent, almost to 0. The active constituents of synthetic tars form crystalline picrntes, the remaining filtrate being almost inactive, and the picrate extremely patent. Shole oil is carcinogenic, probably as a result of the high temperatures to which oil shale is subjected 3.04, However, temperatures below 400cC. give a relatively inactive product, 500cC. and above being required 3-01, In England where high temperature tar is used in briquette manufacture, there are many cases cf skin cancer among the workmen, which is not the case in France where the low temperature product is used. The greatest amount of investigation cf any type of occupational cancer has been carried out on mule spinners cancer in the cotton mills cf Lancashire, England. Scutham and Wilson 88 in 1922 first called attention the excessive occurrence of cancer in mule spinners. Women workers are not affected and about 70$ cf all cancer among mule spinners is cf the scrotum 84, apparently due to the fact that a mule spinner at work walks to and fro in front of his machine, leaning over the moving frame from time to time to join up broken ends of the yarn The base cf the frame is on a level with the groin and the spindles on the frame as they rapidly revolve throw off oil from their bearings onto the clothes. In the hot mills the men perspire freely and so wash off the natural grease cf the skin, thus allowing the oil closer contact 3-5, Irritation by the trousers and overalls also helps the process. It is interesting to note that no trouble of this sort was noticed in England until mineral oil replaced animal and vegetable oils as a lubricant 3-6, Henry ^3 estimates that 0.25$ of all cotton mule spinners in England suffer from scr,ctal cancer. On the other hand in the United States during 1926, for example, there were only 33 deaths from cancer of the -5- scrctura, cf which only three cf the victims were textile workers and three w<jre mule spinners; four cf the six were bom in England and the other two in Canada ^5, which tends tc show that mule spinner cancer is rarely contracted in tne United States. In a woolen mill in the United States employing about 200 mule stunners no cases of scrctal cancer were found Since the method of operating this equipment is the- same in both countries this striking contrast is attributed by Hamilton ^ to the fact that Scottish shale oil is used in the Lancashire rills. However, the literature is not entirely clear as tc the origin and type cf the oil used in Lancashire in mule spinning 53, Leitch 70 brings out a fact of possible significance, to the effect that cancer is nc t known in woolen spinning mills, even though the same machines are usod as in the cotton factories, but points out tho.t the rcon temperatures in the cotton mills are much higher, possibly resulting in mere relaxation cf the tissues cf the scrotum and permitting entry of oil into the sebaceous follicles. Bred:bank however, states that in the wc-clen industry piecing cf broken ends cf yam is dene with both hands with a forward level bending movement of the body and thus there is net the same friction of the clothes cn the scrotum as in the cotton mills. He admits, however, that the same oil is used in both types cf mills. , rts a result cf the preliminary investigation cf Scutham and i/ilscn mentioned above, the Manchester Cancer Commission, consisting of mere than fifty members, was organized in 1925 under the 'direction cf Dr. C. C. Twort tc investigate the mineral oils used in Manchester cotton mills. Lubricating oils from the various fields throughout the world were found to have widely varying degrees cf activity. A sample of Venezuela oil was very potent while Russian and Pennsylvanian salaries were cn an average less than one--tenth as active. Purified medicinal oil had nc carcinogenic properties end several saponifiable oils, such as sperm, olive, rape, cottonseed and neatsfoct oil, failed tc produce -6- tumcrs when applied to mice, even under the most severe experimental conditions. In general terms, the more saturated were the constituent hydrocarbons of the lubricating oil, the less capable were they of inducing cancer in experimental animals, the physical characteristics being the same -^lt This preliminary report was criticised severely in an editorial in the "Petroleum Times" of London in that while various oil companies (Anglo-American, Anglo-Persian and Shell-Mex) had contributed fcl,000 for two years for the support of this investigation, yet the Manchester Cancer Commission had not availed itself of the services and advice of experts from the oil industry relative to the characteristics and methods of treatment of petroleum oils. The Institute of Petroleum Technologists, while making no definite criticisms at this time of the work of the commission, formed a committee of its own to follow closely the work in progress ^3, in 1934 Dr. A. E. Dunstan, Dr. F. H. Garner and Mr. James Kewley of the Institute of Petroleum Technologists are shown as members of the Manchester Commission ^1, In 1933, Twort and Lyth of the Manchester Cancer Comnittee reported that by means of solvents, extracts were obtained of high refractivity and correspondingly high carcinogenicity. Their recommendations for the selection of an oil of low carcinogenicity were as follows: When selecting from several mineral oils with similar gravity, specify that with the lowest refractive index; when selecting from those with similar refractive index, specify that with the highest gravity; when selecting from those with similar refractivity, specify that with the highest viscosity; and when selecting from origin alone, choose in the following order: Russian, Pennsylvanian, Texas, Mid-continent, Mexican, Californian, Persian, Rumania, Borneo, Venezuelan, shale. However, it should be emphasized at this point that these authors state definitely that "adequate refining of any of the oils handled, of no matter what origin, results in a product ............... possessing only a very low API 04623 -7- carcinogenicity" 10Z*. Also, that a single extraction of an unrefined distillate with SC12 nay profoundly lower the activity of a previously very dangerous oil, wnile a second extraction may render it almost inert. They state that "it is nrobahly commercially feasible to treat oils of any origin, or oils of any degree of carcinogenic activity, so that they may be less dangerous than even the very best of the straight oils used today". They evidently assume that untreated textile oils are used in the Lancashire mills. Lyth of the Commission further stated 71 that when the refractivity* of an oil was less than 0.5500 it was found to be non-toxic, while when the value was greater than Q,5b00, the oil was highly toxic. Pennsylvanian oils and certain mildly treated oils were an exception. The iodine value of an oil seems to afford an indication of its toxicity, providing the oil has not been treated and again the higher the value, the more potent the oil. The toxicity increases in the same order as iodine value, except for Pennsylvanian oils which again occupy too high a position. The permanganate values are not regarded as of any value in connection with estimating the toxicity of oils. Lyth adds that extraction with alcohols, acetone, etc., clay and acid treatment, leads to a reduction in the potency, especially in the case of the more potent oils but a corresponding reduction in the rofractivity does not always occur. Where a marked reduction in the refractivity does occur, there is, without exception, a marked decrease in carcinogenicity; with a marked increase in refractivity, a corresponding increase in potency. Where the refractivity is not auch altered, the potency may or may not be affected and further tests are necessary. In spite of the apparent definite findings and recommendations of the Manchester Cancer Commission, the Cancer Research Committee of the Institute of Pctrolfcujp Technologists 51 wa3 not convinced that "the so-called incidence cf * (Refractivity Refractive Index - 1 . DENSITY ' API 04624 -8- cancer is in any shape or form connected with the use of spindle oils". No elaboration of this statement was given, but was possibly based on refined oils cnly being used as textile lubricants. An editorial in the "Petroleum Times" of London in 1937 once again attacked the conclusions of the Manchester Committee, pointing out that only one oil from each of a number of countries was examined . In 1937 the Federation of Master Cotton Spinners Association sent out a letter to its members_recojnnending that when purchasing spindle oils a guarantee should be obtained that the oil conforms to the specifications of the Manchester Cancer Commission, and that tests had shown that many of the oils in use at that time conformed to the specification. While throughout the reported work of the Manchester Cancer Commission it is stated repeatedly that acid or solvent treatment of a potent oil greatly reduces or eliminates its activity 97, 102, 104, 71} yet in 1939 Twort and Lyth ^7 investigated acid and clay treated distillates from a Borneo oil and found them to be active, the maximum potency being at a viscosity of 200-250 cp at 25cC. Molecular distillation gave a greater concentration of the carcinogenic material than was obtained by ordinary distillation at from 3-10 mm. In confirmation of previous findings the middle fractions of this Borneo oil were mostly responsible for pathological changes in the organs, A carcinogenic shale oil was separated by molecular distillation into fractions which were subjected to chromatographic adsorption. Two apparently pure hydrocarbons have been isolated and are being investigated 2,109, A recent report (1941) by C. C. Twort of the Manchester Cancer Conmission states that animal tests are variable, lengthy and costly and that a ^re reliable estimate of the carcinogenicity of oils can be obtained from the refractive index and viscosity. (Yet the data on which selection of these two properties was based were obtained by means of this variable skin test.) -9- VJoodhouse of the Birmingham Cancer Research Laboratory also states that mouse tests to determine carcinogenicity are difficult to correlate with human tendencies to cancer unless these animal tests are strongly positive or negative -j-^l. For example, two oils were tested (a) from a spinning mill where no cases of mule spinners cancer had been recorded, and (b) from a mill where six cancers had recently been reported. Mouse tests indicated slight carcinogenic properties in the case of the two oils but a greater action on mice of (a) than (b). Dr. E. M. Brockbank, chairman of the Manchester Cancer Commission, has briefly summarized the investigations of the Commission in a recent publication ^-6, He lists the hygienic precautions to be exercised in mule spinning and urges the adoption of the oil specification given previously by Twort. He also makes this interesting generalization: "As a general rule an oil that is strongly dermatitic will not be strongly carcinogenic and vice versa". This is also mentioned by Kennaway ^ who states that cyclohexene (which is non-carcinogenic) is extremely irritating to the skin and should produce cancer if chronic irritation were an essential factor in carcinogenesis. \_ As mentioned previously, shale oils are very carcinogenic and in the Scottish shale industry the case incidence of skin cancer is about 0.1$ per annum among the oil workers but 0,5$ among the paraffin workers 53 (this is based on a 28 year record). This activity of paraffin is restricted by Schwarz and Tulipan to the crude product, the refined wax being inactive, which view is supported by Wood H9 who states that the active components are present only in the crude paraffin oils. _ Vfith regard to the refining of petroleum oils. Wood made an investigation of refineries in Pennsylvania and found no scrotal cancer, which was confirmed by Heller However, Heller found evidence of carcinogenic compounds in Mid-Continent oils as refined in plants in Ohio and Indiana. Here il boils are fairly common and in some cases lead to skin cancer. In one case API 04626 -10- a paraffin pressman in the Middle T.7est was treated for "wax boils" for three years when a cancerous growth developed on the right foreara and was removed, but eight years later a second similar growth in the same place had to be removed. Heller also found records of cases of skin cancer in another refinery, using crude from the Lima field; eight cases had occurred in this refinery and one was fatal. All of these cancers were preceded by warts. The length of exposure before malignancy appeared varied from four to thirty four years. The part most often affected was the scrotum and all but one man worked in the paraffin department. These cases were caused by unrefined oils and Hamilton 40 states that so far there is no proof of the occurrence of skin cancer in the U.S. from the use of refined lubricating and spindle oils which have- been acid-treated, Heller ^ believes that the relative freedom from occupational cancer in the U.5. is due to the mechanization of industrial processes, preventing direct contact with the pitch and tar; the extensive employment of negroes, who are apparently less subject to skin irritants than whites; the use of refined lubricants from crudes which are poor in carcinogenic properties, and the use of tar from coke-ovens instead of from gas works, Phillips ^ reports the particulars of a study carried out by the U.S. Public Health Service as to the incidence of occupational cancer in Texas. The records of.1190 individuals having microscopically verified skin cancers were analyzed, covering the period 1920 to 1940, The occupation of the largest group of these patients was outdoor work (farming and ranching); the work of housewives comes next in order, followed by various activities requiring moderate outdoor life. The professions were next, followed by laborers and carpenters. The / railroad and petroleum industries furnished few cutaneous cancers. Uafafer and Sitgreaves in a U.S. Public Health report issued in 1940 ^7 analyze 70 cases of cancer recorded for the male members of the sick benefit plan " il refining company during the period 1933-38; there were 46 deaths. The death rate was 0.78 par 1000 and a frequency of 1.2 per 1000 (all U.S. death rate t 1 -11 0.96 p^r 1000). Almost 70% of the deaths were related to the digestive system and the rate for this site was higher than in the total population. Deaths from cancer of the genito-urinary system was b.5% of the total, compared to 15.056 in the case of the total population. In 1934 Campbell-^0, 21 laboratory tests on mice with dust obtained from tarred roads. This dust caused warts and cancer of the skin and in six months 24 out of 59 mice showed typical tar warts, half of which developed malignancy. This finding was confirmed by Kling, Samsonow and Heros, ^4, 65 who also separated a substance containing the benzopyrene nucleus from the tar. However, Hogouneg ^ is doubtful of the danger from read tar since it usually takes years of direct contact of coal tar to the skin to produce skin cancer. (Teutschlaender 91 calls attention to the fact that almost all industrial cancers require an exposure of about ten years before growth appears, although a few cases may arise much later.) Valade m likewise is of the opinion that while primary lung tumors can be induced in mice painted with tar or exposed to inhalation of dust from tar roads, yet these results cannot be transferred to humans. Animals other than mice should be employed in experiments and an inquiry should be carried out on workers exposed daily to such dusts. While the manufacture of briquettes in England is attended by a high cancer rate, 58 since high-taaperature tar is used, yet in the few plants in the U.S. making briquettes eapeer is entirely absent, partly due to the lack of contact with the binder since the process here is entirely mechanized and partly due to the use of petroleum asphalt as a binder, This finding was confirmed by Wood 120 in his investigation of briquette manufacture in Pennsylvania. The addition of glycerides 9 reduces the carcinogenic potency of mineral oils but net to as great an extent as lanolin. Speakman and Chamberlain state that while alcohols have not been used for this purpose there can be little doubt that such polar compounds will reduce the risk of cancer formation by promoting emulsification, since an oil which is easily and completely removed from the skin API 04628 -12- must curry less risk than one which is difficult tc emulsify. These investigators also believe that polar compounds in a mixture with mineral oil may, however, function in yet another way. It is known that the carcinogenic agents of mineral oil when associated with unsaturated compounds are free to concentrate at any surface tc which the oil is applied, the ncn-pclar paraffin molecules offering little or nc resistance. However, when oil-soluble polar compounds, such as cleyl alcohol or wool-fat ether, are mixed with mineral oil they concentrate at the surface, excluding the less polar carcinogenic hydrocarbons. Sequeira stresses the necessity of absolute cleanliness of body and clothing, the application of castor oil p0 exposed surfaces and medical inspection every three months. Brcckbank ^-5 suggests a mixture of lanolin and olive oil be applied to the skin. Duckham advocates the use of an oil-sclvent cleanser similar tc the ether soap used in hospitals in order to remove all of the lubricant from the pores In view of the suggested use of lanolin the following should be of i. particular interests Dr, $. V. Ccwdry, of the '.Vashingtcn University School cf Medicine, St, Louis, has just announced (N.Y. Herald Tribune April 29, 1945) that cells can be sensitized to become cancer cells by treating them with a substance which dees not cause cancer and which will even prevent powerful cancer-producing chemicals from exhibiting that property. .. For example, when the powerful carcinogen methylchclanthrene is mixed with lanolin it is without action when applied tc the skin cf mice, although alone it always results in cancer. However, when these mice were then treated with methylchclanthrene in benzene they developed cancers more quickly and tumors cf greater virility than mice which had not received the cancer-preventing treatment. MPD-VL DVJS -13- K3FEH3NC3S 1. Anon., Cancer from Spindle Oil, Oil and Color Trades J., July 2, 1937, 3^ A letter sent out by the General Committee of the Federation of Master Cotton Spinners1 Association recommends that when purchasing spindle oil members should obtain a guarantee, that the oil conforms to a specification of the Manchester Cancer Committee which recently issued a fofaila claimed to minimise the so-called cancer-producing elements of mineral oil. Tests showed that many of the oils in use at present con form to this specification and are obtained at regular prices. 2, > Anon,, Cancer and Mineral Oils, Oil and Color Trades J,, 102, 695 (19^2) The report of the Manchester Committee on Cancer, issued for the year ended October, 19^1, states that in efforts to isolate and char acterize individual carcinogenic hydrocarbons from shale oil, recently appreciable quantities of crystalline material have been obtained, but it is too early to discuss results in detail. As far as can be judged, all fractions obtained from Venezuelan Oil by chromatographic adsorption are active. Proprietary colioids have varying effects, depending on the conditions of the experiment, A colloid containing a chlor-compound was found less efficacious than an olive oil-lanoline mixture as protection against the carcinogenic action of shale oil, while the reverse appeared to be the case when the carcinogenic agent used waB benzpyrene* 3. Anon,, The Problem of Cancer. Petroleum Times, 2j[, 59, 300 (193) (a) The following appeared in a recent issue of the British Medical Journal in connection with the use of mineral lubricating oils in the Lancashire cotton mills: "The Manchester Cancer Committee, while studying the part played in the production of malignant growths by the lubricating oils used in cotton mills, has obtained information about the earcinogenetic power of various oils and the concentration within then of a cancer-producing principle. In the course of this research, two pure compounds of known chemical composition have been proved capa ble of producing tumors, and a study has been made of the factors which change a non-caroinogenic into an active carcinogenic substance. Al ready some of the methods for destroying the cancer-producing power of certain oils have proved to be effective, at least in part, and one method led to the preparation of a purified oil which, when subjected to vigorous test, has failed altogether to produce cancerous growths. Representatives of the cotton industry, after comparing this oil with . the crule untreated oil have said that its lubricating power is unim paired, and the Manchester Committee is therefore able to hold out the hope that before long it may be possible to put on the market on oil ( which fulfills the needs of industry without being a source of danger 'to the workers." Assuming that the use of spindle oils be such a source of danger, it almost necessarily follows that other lubricating oils which come into closer physical contact with the worker must be sources of higher potential danger than any of the light lubricating oilB used in the . looms of the Lancashire cotton industry. It night be proved upon in vestigation that little difficulties Vo-uld present themselves in the production of a spindle oil which is noa-c&rcinogenie, and lest the present attack widens itself to include the whole range of mineral lubricating oils, it would be advisable to make an investigation of the most embracing character. API 04630 -14- 4, Anon., A Dangerous Report on Lubricants ani Cancer, Pet. Times, 27, 31^-320 (1932) Criticizes the report of the Manchester Cancer Committee in that the Connittee has accepted contributions of l000 for two years from the Anglo-American, the Anglo-Persian and the Shell lies but has not availed itself of the services and advice of experts from the oil iniustry relative to the character ani methods of treatment of petroleum oils. 5, Anon., Manchester Connittee on Cancer Report. Pet. Times, 2J5, 295 (1937) The 1935-36 report of the Manchester Committee on Canc.pr claims that "with a knowledge of the refractive index of an oil, ani of the viscosity, one can fora a more reliable estimate of its cancer-producing powers than.by the application of the sample to the skin." It is pointed out, however, that Binilar conclusion in the 1933-3^ report was based on insufficient evidence and that some discrepancies with animal tests were admitted, and that in the 193^-1935 report the animal tests were reverted to. It is also pointed out that the above conclusion was based on the examination of anly one oil from each of a number of countries. 6, Occupational Cancer of the Skin. Annual Report, Chief Inspector of Factories and Workshops, Year 1937* a table showing distribution of epithelionatous ulceration by industry for each of the years 1933-1937 is given in an abstract in American Journal of Cancer, ^4, 6lO (Dec. 193&)* Tar distilling ani cotton mule spinning.take the greatest toll. The increased 1937 figures for tar distilling cases is attributable to voluntary periodical examin ation in some plants. 7. Alapy, H. Cancer Prophylaxis by Preliminary Treatment with Carcinogenic Polycyclio Hydrocarbons. Z. Krebsforsch. 48, 3209 (1938) Mice and rats were treated with very small doses of 3 carcinoeenic hydrocarbons (beaso-pyrene, metlylcholanthrene and 1, 2, 5. 6-iibenzan- thracene as a method of protection against the implantation later of highly virulent tumors, Usually a single subcutaneous injection was made of the carcinogenic agent dissolved in sesame oil. The most effi- ' cient dose in mice was 1.5-37 *oi the most favorable time U0-70 days, before the implantation of the tumor emulsion. Dibenzanthracene was . somewhat the most effective. The protection in mice was only slight. Development of the tumor was delayed 5-6 lays and for ^-6 days was slow. Growth then became rapid and on the 17th or 18th day after implantation of the tumor the tumors were of the same size in the animals with treat ment and the control animals . No hindrance to tumor growth was obtained in rats given l-100y doses, occasionally 150-180y doses 3-4-80 days before implantation of the tumor. A definite active protection cannot be obtained by this method. .. 8. Bachmann, W. 2. et al. PPrrooiduuction of Cancer by Pure Hydrocarbons. Proc. Roy. Soc. , 343-6S (1937) -- respect to high carcinogenic potency, methylchclanthrene is not surpassed by any compound yet tested, although it is almost equaled by cholanthrene. Production of carcinoma is favored by introduction of substituents into the 5 position of the 1, 2-benzanthracene mol.; API 04631 15- 2-Me-31 4~benzophenanthrene 1b carcinogenic to a high degree as are certain hexacyclic hydrocarbons derived from the pentacyclic hydrocarbon 3, 4-benzopyrene. 9. Badger, G. M. et al. Production of Cancer by Pure Hydrocarbons. Proc. Hoy. Soc. B122, U39-67 (19^0) Information as to tha most effectual method for the production of any particular tutor (painting, subcutaneous injection, feeding) is not decisive; in the two latter the fur is always contaminated, and inhala tion and swallowing cannot be excluded by any of the methods. The 3. 4-benzophenanthrene compounds possess carcinogenic properties, and apparently are more active than the benzanthracenes in the production of multiple tumors, cbolangioma, and tumors of the lung; the 1, 2-sub- etltuted compounds are more active with resppct to gastric tumors. Compounds substituted on the 1, 2-side are usually more carcinogenic than those substituted on the 6, 7. 8-side. Among the 1, 2-benzanthracenes, the 5-n-Bu, 5-n-Aa, and 5-&-hexyl resemble the 3. U-benzophenanthrones in their association with a higher incidence of lung adenomas and multi pie tumors, and a deficiency in earcnca production. .. 10. Badger, G, U. et al. Production of Cancer by Pure Hydrocarbons. Proc. Hoy. Soc. B131. 170-82 (1942) In the series of Sj^lkyl derivatives of 1, 2-benzanthracene (Me, Bt, Pr, iso-Pr, Bu, CrfJjj, CgBij, C-jHj^) the higher members showed progres sive diminution or carcinogenic power on the shin; member with more than 3 C atoms in the side chain did not produce sarcoma. Tith derivatives of 3, 4-benzophenaathrene, substitution in position 2.and, to a lesser extent, in position 1, promoted carcinogenic action; most of' these com pounds were deficient in power to produce sarcoma. 1. 2. 3* 4-Tetraimethylphenanthrene had a slight but distinct ability to produce skin . tumors. 3, 4, 5* 6-Dibenzofluorene had no action on the skin and there by differed from the 1, 2, 3, 4-, 1, 2, 5, 6-, and ,1,2, 7, 8-compounds. 1, 2, 3, 6-Dlbenzocarbazole exhibited a slight tendency to produce tumors of the liver. While multiple tumors could not be ascribed with certainty to the action of the administered compounds, the most striking cases of multiplicity occurred under the influence of 2, 3, U-substituted phenanthrenes, 1, 2, 5, $-diben*oearbazole and 1, 2-3, 6-dibenzacridine.. 11. Barry, G. et al. Production of Cancer by Pure Hydrocarbons. Proc. Hoy. Soc. B117. 318-51 (1935) A large number of compounds, -chiefly tetracyclic and pentacyclic aromatic hydrocarbons, were tested for cancer-producing action, with alee as experimental animals . Considerable cancer-producing power was possessed by 1, 2-benzopyrene (from coal-tar pitch), methylcholanthrene (a ieriv. of deoxycholic acll of bile) and 3. 4-benzophenanthrene. In order to be carcinogenic, derive, of 1, 2-benzanthracene must contain . substituents In positions 5 **1 6. , 12. Bergmnn, 7. Mechanism of Tumor Production by Chemical Agents. Cancer Research, 2, 660. (1942) The following principles for tumor production by chemical agents are hypothetically established; 1. The form and size of a carcinogenic hydrocarbon and of its related heterocyclic compounds determine its activity. Every substance which imitates more or less closely a given parent structure resembles it also in its blastomatogenic action. -16- ' 2. In the living cell, the carcinogens are adsorbed, "by an acceptor possessing a definite adsorption area. This sets an upper limit for the dimensions of the active compounds, A lower limit is given by a decrease in adsorbability with decreasing size of the molecule. 3* All carcino gens are conceived as parts of an "ideal carcinogenic structure,'.' A carcinogen can be inactivated by additions which prevent its proper adsorption. The mechanism of this hindering effect is discussed. 13, Bonser, G. M. Tumors of the Skin Products by Blast-Furnace Tar, Lancet 1, 775-6 (1932) " The results obtained with four samples were remarkably similar to Berenbluu's and blast furnace tar is therefore carcinogenic, though not so potent as the gas tar employed. The reason that.it haB been innocu ous for man 1b that the yield is small, and it is regarded as a waste product and is disposed of without further handling, . l4. Boyland, E. and Brues, A. U. Carcinogenic Action of Dibenzcarbazoles. Proc. Roy. Snc. 1223. U29-hl (1937) Cancer of the bladder is unduly frequent among chemical workers, and those dealing with naphthylamines and benzidine seem most liable to the disease. It has hot been demonstrated satisfactorily that naphthyl amines are carcinogenic, and it is possible that it is not they which are responsible for cancer of the bladder, but impurities formed during their manufacture, such as dinaphthylaminee and dibenzcarbazoles. Sub stances of this nature were therefore tested for carcinogenic activity by painting on the skin of mice and one (which proved most active on mouse skin) also by subcutaneous Injection into rats, . The most active was 3:^:5:6-dibenzcarbazole but this was toxic. It produced malignant skin tumors in mice in ISO days. Of the other sub stances tested, l.*2s5:6-iibenzcarbazole was carcinogenic and 1:2:7: S-dinbenzcarbasole feebly so. The dinaphthylaminee, 0-aninoazotoluene, known to produce hepatoma, and diamino-azobenzene (chrysoidine) all failed to produce tumors on the skin of mice. Spindle-cell sarcomata, one of which was proved transplantable, were produced in rats by sub- * curaneous injections of a colloidal suspension of 3j^J 6-dibencarbs* so le. - 15, Brockbank, E.U. Mule-Spinner's Cancer. Brit. Med. J., 622-3 (U.26,4l) 16. Brockbank, X. M. Hale Spinners Cancer. Epithelioma of the Skin in Cotton Spinners. H. K. Lewis and Co., Ltd., London. 36 pp, (19^1) the first known case of scrotal cancer ia a mule spinner was re* ported in Manchester in 1887, 37 yoars after the introduction of mineral lubricating oil; before that time sperm oil and neatsfoot oil had been the principal lubricants. It is now known that cancer of the skin, whether of the .scrotum or elsewhere, in mule apinners is caused by carcinogenic ooopounde which are present in mineral lubricating oils though not in lubricants derived from animal or vegetable sources. Some mineral oils are more carcinogenic than others, that derived from shale being particularly dangerous, and it has been leaaned by experience .that cancer is more likely to be caused if the sane lubricant is used con tinuously, than if the kind of oil employed is occasionally changed. It has been found also that by mixing animal or vegetable oil with mineral oil the carcinogenic potency of the lubricant may be abated. API 04633 -17- 17. Burrows, H,, Hieger, I., and Kennaway, E. L. Experiments in Carcinogenesis: the Effect of the Subcutaneous and Intraperitoneal Injection of lard, Olive Oil and Other Patty Material in SatB and Mice, J, Path. Bact, . 419-26 (1936) 13, Campbell, J, A. Experimental Production of Cancer by Dust Obtained from Tarred Hoads. Brit. Med. J., 2.3.3^. 233-4 This dust caused warts and cancer of the skin of mice with metaetases sometimes in the lungs; in 6 months 24 out of 59 mice showed . typical tar warts, half of which developed malignancy. 19. Campbell, J. A, The Effects of Hoad Dust "Freed" from Tar Products "jpon the Incidence of Primary Lung Tumors of Mice. Brit. J, Exptl. Path. IS, 215-24 (1937). . It has been shown that dust from tarred roads causes cancer of the skin of mice, Hoad dust minus tar, as removed by benzene, does not cause cancer of the skin of mice; it stimulates the production of lung tumors in mice, but not to so great extent as when the tar is also present, . 20. Campbell, J. A, Carcinogenic Agents Present in the Atmosphere and Incidence of Primary Tumors in Mice. Brit. J. Exp. Path., 20, 122-32 (April, 1939) The author has continued Mb research on substances that might induce lung tuaops. He employed chimney soot and soot scraped from exhaust pipes of engines burning heavy oils. Hats were exposed to these dusts for 10 min* an hour for 6 hrs., 5 days a week for 1 yr. The death rate of both groups was well within the limits of that for the controls but the number of lung tumors was somewhat higher. Of those exposed to exhaust pipe soot, 33$ living 10 mos. or more developed tumors. The . most active substances tested was dust from tarred roads. Data are also given on mice whose skin was painted with "tar" from these substances, 21. Clark, H. Y. Cancer from Lubricating Oils. Oil-Color Trades J., 11.9*3^. 1278-9 . . 22. Cook, J. V*, Hewett, C. and Hieger, I. Coal-Tar Constituents and Cancer. Mature, r$0, 926 (1932) Several hydrocarbons were isolated from coal tar which were active . in producing cancers and which had the typical fluorescence spectrum of carcinogenic fractions. The most active hydrocarbon Isolated was 1, 2beasopyrene which produced cancer in half the time required by 1, 2, 5, 6-dibensanthracene. Ferylene and 4, 5-bonzopyrene were also isolated, 23. Cook, J, V. et al. Production of Cancer by Pure Hydrocarbons. (a) Proc. Boy, Soc. (London), Bill, 455-84 (1932); (b) Proc. Hoy. Soc. (London), BmT 485-96 (1932) (a) Mice were.used as exptl, animals, and a study was male of the action of 22 different polycyclic aromatic hydrocarbons, contg. 3-8 rings in their reep. noIs. and applied in soln. to the interscapular region, usually twice weekly. Of these pure compds. only 1, 2, 5. 6-dibenzan thracene and certain closely related compds, produced cancer; it was active in 9 Ufferent solvents, and was effective when applied in 0.003$ soln. in CgHg, Of 273 mice treated with this conpd., 107 developed tumors. including 77 epitheliomas and 21 papillomas. API 04634 -18- (b) The investigation has been extended to include 52 aidnl. poly cyclic aromatic conpds . Tumors were produced "by 6-iBCpropyl-l, 2- benzanthracene, 5, 6-cyclopenteno-l,2-benzanthracene, phenanthroacenaph- thene, and 5 derive. of 1,2,5,6-dibenzeuuhracene: 2'-4ie, 3'-'ule, 9-*3H2, 9-tieO, 9,10 (C6H^K2)2. ' 2k. Cook, J. W,, Hewett, C. 1, and Kieger, I. The Isolation of Cancer-Producing Hydrocarbons from Coal Tar. J, Chen. Soc., 395-405 (1933) The preparations derived from coal tar pitch by a variety of solvent extraction nethois, the fractions separated by formation of picrates, distillation and crystallization, and the hydrocarbons, 1:2-benzpyrene, and 4;5-benzpyrene, perylene and 1,2-benzanthracene, have proved carcino genic and have given the sane fluorescence spectrum (bands at 4(X)0, ^180 and 44oQA), The original coal tar pitch contained not less than 0.0035b of 1, 2-benzpyrene. 25. Cook, J. W. Synthesis and Biological Effects of Carcinogenic Hydrocarbons. Chen, and Ind., ^4, 1022-3 (1935) Certain forns of skin cancer due to occupation causes in industries where shale oil, coal tar and lubricating oil are.employed, have been shown to be due to the benzanthracene group of hydrocarbons which also impart fluorescence to the oils. The exact nature of cancer formation in the human body has not been explained although a similar benzanthra cene hydrocarbon has been found to be produced by body changes from substances normally present in the human body. . 26. Cook, J. W. Carcinogenic Hydrocarbons and Their Relationship to the Sterols. Chea. tfeekblai, 32, 563-6 (1935) Review of historical development of recognition of the cancer- producing constituents of coal tar and earlier investigations; the development of fluorescence spectroscopy and the systematic study of ' synthetic carcinogenic hydrocarbons including a summary of the results obtained from the examination of a complete series of tetra- and penta- cyclic hydrocarbons and a moderately wide range of benzanthracene derivatives. The speculation is advanced that a mesc H atom in a completely aronatio structure plays sone role in the carcinogenic process. The isolation cf 1,2-bensopyrene from coal tar and itB synthe sis are recounted and. an account is given of the cyclization of bile acid derivatives, and the eventual synthesis of methylcholanthrene, a carcino genic hydrocarbon related to the sterols. It is inferred thAt there is sone ensymic factor present in the animal body which is capable of effecting dehydrogenation of the sterol ring system and thAt excessive activity of this factor may conceivably contribute to the production in vivo of carcinogenic compounds. . 27. Cook, J. V., et al. Chemical compounds as Carcinogenic Agents. An. J. Cancer, 2^, 219-59 (1937) A full survey is given of the carcinogenic chemicals, dealing both with their chemical relationships and their biologic effects, bringing together, under well chosen headings, all the naterial published up to the end of 1936* They include not only the hydrocarbons of the benzan thracene type, but also the azo compounds, estrin, the styryl quinoline derivative discovered by Browning et al,, and the inorganic compounds zinc chloride and arsenic. A bibliography of 194 references is appended. 19- 23, Cook, J, W. and Kennaway, E, L. Chemical Compounds as Carcinogenic Agents, First Supplementary Reoort: Literature of 1937* Am. J. Cancer, 33, 50-97 (1938) Authors present an exhaustive review of this subject which should be of interest to all industrial physicians. It continues the earlier review and the two reports together have bibliographies totaling 37U references. 29> Davis, E. Chemical Carcinogenesis, Drugs, Dyes, Remedies and Cosmetics with Particular Reference to Bladder Tumors. J. Urol. l4 (1943) Author discusses at considerable length the large number and variety of proved chemical carcinogenic agents which may be introduced into the body by ingestion, inhalation, injection or cutaneous application. He strongly inclines to the theory of some chemical carcinogenic agent. Many are cited such as derivatives of coal tar, crude mineral oils, an anilin dye "intermediate", azo dyes and estrogenic substances. The aniline bladder tumor of dye factory works develops after years of ex posure to what are probably extremely small daily doses. The theory is advanced that there may be many other carcinogenic agents as yet unknown which are unknowingly encountered in the routine of daily life, and perhaps through the use of many drugs, patent medi cines and eosmetics, vitamins, sex hormones, and the tremendous list of anilin dyes used in the coloring of food stuffs.and fabrics. 30. Downing, J. G. Industrial Dermatoses. J. Ind. Hyg., 1J, 138-I65 (1935) A review with 208 references. A section on chemical agents includ ing inorganic compounds, hydrocarbons and crude coal tar products and . other organic compounds; treatment and legal.aspects. 31. Fell, 'A. Oil Button (Elaiokoniosis) i PresseMed., Uo, 1541-2 (1932) Description of a dermatitis in industrial workers caused by heavy , mineral oils, including treatment and prophylaxis. I 32. Fieser, L. F. Carcinogenic Activity, Structure, and Chemical Reactivity of Polynuclear Axweatic Hydrocarbons. Am. J, Cancer, JU, 37-12^ (1938) A long review which includes; 1. a.critical evaluation and compari son of the methods for determining carcinogenic activity; II, informal tion concerning the preparation and purification and the eeimnereial sources of the carcinogenic hydrocarbons; III, 4 summary of the work on correlation of chemical structure and carcinogenic activity, and IV, a summary of investigations on the metabdlic fate of various active hydro carbons. There is a very extensive bibliography. .. 33 Fieser, L. F. Production of Cancer by Polynuelear Hydrocarbons. Univ. Penna. Bicentennial Conf* Cause and Growth of Cancer, 1-27 (19^1) . A review devoted to N-containing carcinogens, relation of carcino genic hydrocarbons to the steroids, carcinogenic activity, chem. struc ture and chem. reactivity, nature of a possible reaction leading to carcinogenesis and of the metabolism reaction. If carcinogenic hydro carbons can be produced at times in the body by steroid metabolism, their most likely precursors are among the steroids of the adrenal cortex. The initiating action of a hydrocarbon in carcinogenesis probably involve# substitution in the hydrocarbon at its most reactive center, probably a direct interaction of the hydrocarbon with an S-S linkage of the cell API 04636 20- protoplasm. Metabolic elimination of a carcinogen probably is a detoxi cation produced by a mechanism different from that leading to carcipo- genesis, and involving a different point of attack in the mol. The reaction of detoxication and that of carcinogenesis are competitive. Detoxication may involve biol. hydroxylation to a phenolic deriv., or conversion into derive, of oercapturic acid. . jU. Fieser, L. F. and Fieser, M. Carcinogenic Hydrocarbons. "Organic Chemistry", 1944, 814-26. Carcinogenic activity and structure; correlation with chemical reactivity; methods of pynthesizing carcinogenic hydrocarbons. . 35. Firquet, J. and Malter, M. A. Pitch Cancer bb an Occupational Disease. Archive de Medecine Social et d'Hygiene et Bevue de Pathologie et de Physiologie du Travail, II, 797-807 (1939-Uo) . The authors report their experiences made in medical supervision of 126 workers in the province of Liege, working with pitch or tar.. There were found two epithpliomata only, and no lung cancers. V. Henry made a chemical examination of various pitches as to their content in 1.2 ben- zeaeanthracene.and 3*4 benzopyrene, (the two most effective cancerogenic substances in animals) and he found in the pitch 1-3$ of the first, traces up to 0.4$ in.the second. The examination of the pitch dust ip the two briquette factories revealed mostly large particles: in the work shop 80$ of a diameter of 50-100u, in the storage rooms 90$ of 20-50u. Therefore it seems--according to the authors--that substances which are cancerogenio to animals are not for men, but more research is neces sary. (The material is much too slight for any conclusions in the opinion of the abstractor.). ' 37. Gafafer, f. U. and Sitgreaves, E. Disabling Morbidity and Mortality frpm Cancer among Male Employees of Oil Befining Company, with Beference to Age, Site and Duration, 1933~3S,inclusive, TJ.S. Pub. Health BeptB. 1517-1526 8.23.40) .. . 38. Guglieninetti, M. Do Macadam Beads Produce Cancer* Bull. Acad. Med,, 122, 89-94 U939) The author first reviews the literature. He questioned various hospitals in some of Germany1s large cities regarding the number of observed cases of cancer and sent, these reports to the managers of the road building system in these cities. Increase of cancer was affirmed . but without relation to macadam roads. 39. Hamilton, Alice. Cancer from Tar Mnd Petroleum, "Industrial Poisons of U.S.", . 410-7 (1925) 1 40. Hamilton, Alice. "Industrial Toxicology", 134, 253-4 . Occupational cancer is rare in France. In.the TJ.S. the only pub lished case up to 1930 WR8 the case of a man who had worked for 20 yrs. at the paraffin process in a petroleum refinery. In 1928 the Health Committee of the League of Nations requested its members to aid in a world-wide inquiry into the occurrence of occupa tional cancer by undertaking a study of the question in their own countries. The Bockefeller Foundation then made it possible for Imre API 04637 '21- Heller to make an Intensive investigation in this country, and his report was published in 1930* Heller confirmed the impression held by American authorities on cancer, that those of occupational origin are very very rare in the United States. He found in the records of the two New York hospitals specialising in cancer only 37 caseB of skin cancer that could possibly be traced to tar and tar products, 26 of these occurring among men handling gaB-house tar or pitch, only two in coke-oven tar or pitch workers. In a Cleveland plant making carbon and dry batteries, imported English gas-house pitch was used vp to 1906, when it was supplanted by American coke-oven pitch. There were 21 oases of cancer among the work ers in this plant, only 4 of which were in men handling coke-oven pitch, and these were not considered by the physician in charge to be indubitable cases . 41. Hartwell, J, L. Survey of Compounds which have been Tested for Carcinogenic Activity. U. S. Public Health Service, 371 pp. (1941) This bulletin represents a survey of the field of chemical carcino genesis in the higher animals: the action of carcinogens on isolated tissues, tissue cultures, plants, protozoa, and bacteria is not consid-. ered. The literature is covered to 1939. and the compilation also, includes experiments with 153 compounds from the unpublished work of Dr. 'M. J. Shear and Hr. H. L. Stewart of the National Cancer Institute. The results of the testing of 6l of these compounds are newly reported, while 45 are new to the whole cancer literature. Altogether the work comprises data referring to 696 chemical substances: of these, 169 are reported to be carcinogenic, apart from 23 observed as causing paiilomas only. After an introductory discussion, the bulletin takes the form of a tabular review on the following class ification (figures in parentheses show the number of entries for each category): A. Inorganic substances (35) B Organic compounds: I, Aliphatic (36); II, Polycyclic [dicyclic (26), trieyclie (37). tetracyclic (152), pentacyclic (llU), hexacyclic and higher (25)J J III, Aso-compoundB (39)t IV. SteroidB (86); V, Hetero cyclic (59)! VI, Unclassified (77). Vlthin this arrangement, compounds are individually numbered and then grouped according to prototypes and alphabetically. The tables give structural formulae, literature references, particulars of species, strain, sex, and number of animals used, preparation, dosage, and rout? of administration of compounds, nature of sites of tumors induced, with details of duration of experiment and survival rates and other remarks. The above conditions shew the wide range of information necessary in order to assess the carcinogenic activity of a given compound. The author draws attention to the incompleteneea of the data for many of the com pounds liatel, and urges tha more systematic investigation of compounds already stuiiel in a preliminary fashion, and for the filling of large gaps among substances which it would seem desirable to test. The review is completed by a bibliography (over 1200 references) and separate indexes to compounds, routes of application, vehicles, animal species, and tunor- . sites. .t 4?, Heller, I. Occtqpational Cancers (inU.S.). J. Ind. Hyg., 12, 169-197 (1930) The chemical properties of gas-works, coke-oven, producer-furnace and blast-furnace tar9 and pitch are briefly outlined with a view to correlating these properties to cancer incidence among workmen in the industries involved# As a result of extensive surveys and health record API 04638 -23- examns., gas-works tar and pitch were responsible for 10.2$ of the cases while coke-oven tar and pitch were held responsible for only 5*^ Coke- oven tar is much the less injurious especially when cognizance is taken of the fact that coke-oven tar is used much more extensively. The presence of olefins in gaB-works tar seems to be of particular importance and may be a cause of oil cancer. Occupational cancer does not occur in the briquet mfg. industry . Mineral oils vary in carcinogenic activity according to their olefin or uneatd. hydrocarbon content. There is no method for.the detn. of the amt, of olefins in the various erode oils; if such a method existed, it would be possible to measure the cancer- producing power of mineral oils. Cancer is not attributable to the occu- pagion of mule spinner in the U.S., possibly because of the carefully refined lubricating oils used on the machines, thus ensuring relative freedom from olefins or unsatd. hydrocarbons. . .. Iji Henry, S. A, Study of Tatal Cases of Cancer of the Scrotum. J. Am, Med, Assn., 102, l667 (1937) Ul*. Hieger, I, , Spectra of Cancer-producing Tars and Oils and of Related Sub stances. Bioehem. J,, 24, 505-11 (1930) . 45, Hoffman, F. L. Mule Spinners Cancer. Monthly labor Rev, of U.S., 7, U57-- . 475 (192S) . 46. Hoffman, W. J. Industrial Cancer. Prevent, Med,, 6, 7-31* (193^) Une of the seven types of industrial cancer discussed is cancer of skin in workers exposed to coal, tar, pitch, soot, shale, petroleum and arsenic. They may cause an epitheliomatous form of cancer. Hogouneng, L. The Ceacerlgenic Hydrocarbons from Tar and the Tarring of Roads. Ann. Hyg# Publ. Socials, 2J, 1-7 (1939) The cancerlgenio hydrocarbons found in coal tar produce skin cancer in exposed workers usually only after direct contact with the skin for long periods of time* It is believed that man is much more resistant to the action of these materials than lab, animals. ... Hueper, V. C. Cancer in Relation te Occupation and Environment, Bull. Am. Soc. Control Cancer, 25, Ho, 6 (June, 19^3) Owing to induetrial development, the general population and factory workers in particular, are exposed tomary new environmental factors, many cf which are disease producing. Occupational cancers are caused by nuaerome chemical and physical ngenta. Among them are the heavy metals, nitrates, aromatic ynina oompounds, benzol, asbestos, mineral oil, soot, ` radio-active substances, ultraviolet radiation and X-rays. The author citeB statistics taken mainly from the records of industrial concerns, but points out their shortcomings. Cancer of the urinary tract due to coal-tar is the most recent addi tion to the list of occupational cancers. It is most frequent in the aniline dye and related industries. Hone Office, Rept. of Departmental Comm, to Consider Evidence eo to Occurrence of Epitheliomatuus Ulceration Among Mule-Spinners. (London, 1926) Contains a bibliography on cancer among petroleum refiners. API 04639 -23' 50. Hunt, S. S An Investigation into the Incidence of Cancerous or Frecancerous Skin Lesions Among Tar Workers in New South Wales. Med. J. Australia, 8.26.33. 281-3 The general conclusion is that tar used in New South Wales for local road-work is not a serious danger. .. 51. I.P.T. Cancer Research Committee. Carcinogenicity of Spindle OilB. J. Inst. Pet. Tech., 2J, 205 (1937) The I.P.T. Committee has not been convinced that the so-called incidence of cancer is in any Bhape or form connected with the use of spindle oils. . 52. International Labair Office. Carcinogenicity of Oils. Ind. and Labour Informa tion, ju, 279 (1930) Tars at varying temperatures have been prepared to determine, at what temperature carcinogenic compounds are formed, from which experiments it would appear that such compounds begin to be formed between 5^0 aaA 600, the maximum yield lying between 800 and 900 C. Attempt is now being made to determine the constitution of a few apparently pure or almost pure compounds isolated from such tars. Applying their standard test for determination of carcinogenicity, the staff found that olive oil, neats- foot oil, sperm oil were non-cancer producing and they have reason to suppose that natural skin fat is an important factor in the prevention of cancer. , .53 International LabourOffice. "Occupation and Health", I, 5^7 (19311) < II.' 837, 1156 (1931*) Before mineral oils came into vogue the practice in textile mills was to use sperm, lard and neat's-foot oils and to some extent castor oil and colza oil. Henry states that shale oil was introduced about 1850 and American petroleum oil about 1864, and that, towards 1872, these oils were being used as components of spindle oil* also that Russian oil was first Imported about 1880, Rumanian oil about 1900 and Persian oil about 1909, and all these were.used for this class of lubricating oil before the war. During the war Scottish shale oils naturally came more into use for lubricating purposes. Oil refiners have their own private formulae for mixings, but there is no doubt that the bulk of the oil sold for lubricating spindles, during the past forty years has been principally made up of natural mineral oil. . According to the 1929 report of the Manchester Cancer Committee, in the distillation of tars, the carcinogenic products begin to form at a temperature ranging from 500 to 600 C. and reach a maximum at between 800 and 900 C. The addition of sulfuric acid at the time of use suffices to make the oils harmless without injuring or modifying their lubricating power. . .. 51*. International LabourOffice, Occupational Tumors. Suppl. to Occupation and Health, I.L.O., Geneva, (Oct, 1939) Carcinogenic substances are discussed under the headings of hydro carbons, non-radioactive inorganic compounds, radioactive substances and radiation, and parasites and microbes. Attention is called to the ab sence of any common physical or chemical characteristics shared by these various cancer-producing agents. I API 04640 24- It is suggested that the cancer problem is essentially biochemical and that its solution will come with the discovery of the nature and cause of the intra-cellular chemical changes which follow the application . of a carcinogenic agent, , 55? Jordan, H. Zsqperinental studies on the Production of'Cancer by Gas-works Tar, Z. Krebsforschung, lg, 39-55 (1922) Author has corroborated the work of others; in white mice treated with tar for four months or less, 100# showed either cancer cr precancer- our changes. When the tar was distd. at 400 the volatile fraction did not produce these changes but the residue produced the typical prolifera tive changes in about 5 the tine required with the whole tar. No prolif eration could be produced with anthracene oil. Different nice showed a narked difference in the rapidity with which they developed proliferation with the same ant. of injury by the tar. Apparently the work was not followed to a point to det, just how many of the mice with precancerous changes would have developed actual carcinoma. . 56. Kennaway, E. L. The formation of a Cancer-producing Substance from Isoprene, . J. Path. Bact. 2J, 233-8 (192U) . 56A. Kawahata, K. Lung Cancer Among Generator-Gas Workers in the Steel Mills. Gann, ^2, 367-88 (1938) . During the past $ years, 21 cases of primary lung carcinoma were observed among the generator-gas workers at the Tawata Iron-Steel Mills, These workers have av# service periods of 16 years, .In no other sections of the mills has such frequent appearance of lung cancer been noticed. The workers are ejqpose^. to the spraying of gas contg, heavy dust. The inhaled gas contained about 0.7# of gaseous or.dust-like tar. Analyses showed creosote oil 24,56#, phenols 0.31#, cresols 0,07#, naphthol 4.65#, anthracene 2,00#, pitoh oil 62,67# and water 5*74#, The metastases may appear very early in the brain, spinal cord and lymph nodes. The dura tion of lung canoer is very short, about 7 months. . .. > 57. Kennaway, E. L. Cancer-Producing Constituents of Coal Tar. Brit. Med.J., 564-7 (1924) Canoer formation by tar products was investigated by author. Only higher fractions boiling at 25O-5OO0 C. were found active in inducing . cancer (creosote, green oil, crude anthracene and pitch). . 58. Kennaway, E. L. Cancer-Producing Tars and Tar fractions. J. Ini. Hygiene 462-88 (1924) Experiments on several thousand mice and analysis of a great mass of clinical records indicate that tar cancer.is caused by a very small Quantity of an unstable compound that exists in the high-boiling fraction (2500 to 500) of a high-tenp. coal tar, i.e,, creosote oil and anthra cene oil. Purified anthracene, like all other pure compounds tried, did not produce cancer. Splashing with hot, crude anthracene or creosote oils seems to be the usual method of contact. Shale oil produces cancer but is less active.-than gas works tar; crude petroleum is much less active; and blast-furnace tar (a low-temp., tar) does not produce cancer. The briquetting industry has reported more than,half of the known cases of tar cancer. Tar made by distilling coal at a low temperature (below 550) produces cancer very slowly or not at all. h?l 04641 25- 59. Kennaway, E. L. Experiments on Cancer-Producing Substances. Brit. Med. J., II, 1-4 (1925) . Cancer has been produced in mice by substances obtained by heating CgHg, isoprene, yeast, human skin to temps, ranging from 700 to 920. A petroleum which produced no tumors of any kind in nice in a prolonged experiment showed vsary active cancer-producing properties after exposure ' to 880. 60, Kennaway, E. L. and Leitch , A. The Anatomical Distribution of the Occupational Cancer. J. Ind. Hygiene, J. 69 (1925) . gl. Kennaway, E. J. Further Experiments on Cancer-Producing Substances. Biochen. j., 24, 497-504 (1930) Carcinogenic substances were obtained by the action at roomtemperatura of AICI7 on acetylene, xylene, naphthalene, naphthalene and bromobenzene and tetrahydronaphthalene, the last two being the most active. Two cancers were also obtained in a series of 10 mice painted with a bo In. of 1,2,7,8-dibenzanthmcene. a-Phenylnaphthalene was prepared by action of AICI3 on CgHcpr and C1(^3 T*1" distillates up to 342 C. containing the hydrocarbon were inactive but the residue in the flask was highly carcinogenic. Cyclohexane, cyclohexane, styrene, hydrophenanthrene, hydrochrysene, hydroretene, perylene, naphthalene and various naphthalene derivatives . all gave negative results. 62. Kennaway, 1. L. and Hiegsr, I. Carcinogenic Substances and Their Fluorescence Spectra. Brit. Med. J., No. 3622, 1044-6 (1930) This paper is a review of a large amount of work by the authors in an attempt to correlate fluorescence with carcinogenesis. Tar oils, spinile and shale oils, which show carcinogenic properties are also strongly fluorescent. . 63. Kewley, J. Cooperation. J. Inst. Pet. Tech., 18, 242 (1932) . Mention of the formation of a committee by the Institute of Petro leum Technologists to follow the work of the Manchester Cancer Committee. 64. Kling, A., Samssonor, N. and Heros, M. The Tarring of Highways as a Possible Agent in the Causation of Pulmonary Cancer. Bull. Acad. Med. 120, 130- ^3 U93S) ." Xxpts. in mice showed that the tar, as used on roads, produces cutaneous tumors and malignancy in the lungs. A substance contg. the bears (a) pyrene nucleus of decidedly cancerogenic properties has been sepd. from the tar, , 63. Kling, A., Samssonov, N. and Heros, M. Possible Relationship between Tarring of Highways and the Increase of Incidence of Pulmonary Primary Cancer, Bull. Acad. Med., 121, 78^-91 (1939) Since tar contains benzopyrene, a recognized cancerigenic agent, it cannot be considered as inoffensive. Experiments on mice definitely con firm this assumption. API 04642 <26- ggt Koelsch, F. Cancer and Occupation. Monatschr. Krebsbekampf. S. T (1937) The author, in the form of an abstract, presents a survey of the relation between cancer and occupation. He includes bone cancer caused by radioactive substances, skin cancer from soot, tar, paraffin and lubricating oils (of which those boiling between 250-500* are of especial importance), skin cancer from arsenic as well as cancer and sarcoma from ultraviolet and sunlight. . ,. 67, Kunae, G. Mineral Oil and Cancer. Chenu Ztg., 52* 407-8 (1935) A study of .the map of Germany indicated that the number of deaths from cancer was always greatest in regions where mineral oil was.found, refined or used, Yhile no definite relation is established, the author suggests the possibility of the existence of such a relationship. Further research, on this problem is indicated. It.is pointed out that mineral oil by itself does not cause cancer. It may, however, become one of the contributing factors, together with others. . , g. Lane, C. G. Occupational Dermatitis. Arch* Dermatol, and Syphil. U3, 1S4 (1941) . Describes the case of a 68 yr. old machinist who for 3 yrs. had a dermatitis of the face, arms, axillae and lower abdomen. There wore scattered areas of tan-brown hyperkoratotic follicles and follipular, plugs. Keratoses were presont on the scrotum and thero were keratotic areas on the arms. Aytopsy revealed carcinoma of the esophagus. Dr. Lane believes the skin changes to be due to oil to which the man was exposed in his 40 yrs. as a machinist, and that the condition is that described by Yhito among machinists, oil.workers and mule spinners in England. It apparently Is rarely seen in this country, possibly because . oils employed here are lesB carcinogenic. 69. Lauber, B. J., Hildebrand, X. and Schocke, H. Possible Therapeutic Action of Carcinogenic Hydrocarbons in Treatment of Cancer. Z. Ges. Exptl. Med., 225. 370-94 (1939) Essentially less harmful therapeutic measures are available. The . dangers are demonstrated on mice treated with.methylpbolanthrene, 70. Leitch, A. Uula Spinners1 Cancer and Mineral Oils. Brit. Med. J., 2, 941-3 (1924) ... " Bendsred an inert California oil very active by heating it. (No details as to temperature, etc.). Crude o1]ls from Assam, Borneo, Egypt, Burma and Badarpur produce malignant growths. Galician, Russian, Californian and Persian samples . were negative. 71* Lyth, R. The Relation of Carcinogenicity of Mineral Oils to Certain Physical and Chemical Characteristics of These Oils. J. of Ind. Hyg. 15, 226-37 (1933) . 72. Lyth, R. Molecular Distillation of Lubricating Oil. Nature, 1J9, 374 (1937) A brief report is givon of the distillation of a Scottish shale oil, using a specially.designed molecular still. The most striking result is the inversion in the change in the physical properties going up the tem perature scale, i.e., the first fractions show higher refractive indices and densities than the original oil, with gradually descending values from fraction four as the temperature is raised. Lata on the properties API 04643 f 27- of the shale oil distillates are tabulated. These experiments are part of an investigation.of the interrelation of refractive index and viscosity to activity on injection, and thereby carcinogenicity . when applied to the skin. . 73. Mioscher, G.,.Almasy, F, and Zehender, Z. Is Thero a Connection Between the Benzpyrene Contont and the Carcinogenic Effect of Tar? Schweiz. Med. Wchnschr. Jl. 1002-7 (1941) . The authors have examined the benzpyrene contont of gas tar in various towns in Switzerland, using a method dovisod by Alnasy. Then the tars were purified and their carcinogenic effect determined by painting on mice* The investigators tried to evaluate the re sults by means of a statistical method in order to ovorcome the difficulty offored by the fact that many mice die in the long period needed for the experiments. They find a simple, regular relationship botweon the benzpyrene content and the carcinogenicity , of.the tarf 7U, Murray, J. A., et al. Discussion on Experimental Production of Malignant Tunops. Proc. Hoy. Soc. (London) B113. 268-92 (1933). A symposium in which some attention is paid to carcinogenic . chon, compounds, and to tho innunochemistry of cancer. 75, O'Brien, H. P. The Problem of Cancer and Oil. Petroleum Times, 27, U62 (1932) . An open letter to tho editor of tho Petroleum Times (London) in answer to an editorial in the issue of March 19th. The writer points out the humanitarian and scientific values derived from the cancer research of tho Manchostor Committee and criticizes the technological viewpoint of the editorial. . 76. 0 Donovan, W, J. Cancer from Handling Anthracene Coke in the Dye Industry. Sr. J. Demat. and 9|ph., . . Three cases of cancer in a factory employing only 23 men. 77 Phillips, C. Helationship between Skin Cancer and Occupation in Texas: Heview of 1569 Teriflod Lesions Occurring in 1190 Patients. Texas . State J. Med., 36, 613-16 (19^1) 78. Prossor-lhite, B. "The Dematorgoses" 199-238 (193*0 Dermatitis and cancor from petroleum products, shale and tors. . Excellent review. 80. Hoffo, A. H. Experimental Be search on tho Production of Pulmonary Tumors by the Distillates of Puel Oil. Presse Med., 938 (I9U0) The author demonstrated ?n oil, taken from tho streots of Buenos Aires, identical to that from motor car exhaust, which con tains carcinogonip substances. Hoffo had rots Inhale the combustion gasos of fuel oil and later found a number of pulmonary cancers among the animals. By injecting a distillate 'of the fuel oil into . .the auricle of rabbits, he produced tuners in 80^. G. and Oberling, C. Can Tarring of Hoads be Considered as a Cause of Pulmonary Cancer? Bull, Acad. Med. 120, 181-90 (1933) Tho danger is not considered to be of significance although the possibility is admitted. API 04644 28- 82. Schreus, E. T. and Zurhelle, E, Experimental production of Tumors with Tar9 from Various Sources and with Paraffin. Deut. Med. Wochschr. 49, 633-4 (1923) . Author investigated the poisonous action of paraffin oil and tar constituents by painting mice twice a week. After six months a state of malignancy was obtained with paraffin oil. Coal tar readily develops malignant tumors. Various purified acid and basic fractions from coal tar give negative results, The neutral tar oil is most offectivc as a tumor inducer. _ #. S3* Schwartz, L. Skin Diseases in Oil Refineries. Safety Eng., 210 (Nov. 1934) It has been found that workers in oil refineries have a percentage above the average for carcinoma of the chock and of the lip . An unusual provalonoe of pigmented papillomata on tho hands, foroarms and legs of workers in oil refineries and among machinists in contact with oil and grease was also noted. About 10$ of such workers were found to have theso growths. Tho uso of totally enclosod manufacturing systems and of protective ointments is suggested. . 84, Schwartz, L. and Tulipan, L. "Occupational Disoasos of the Skin", 1939. 5^4. 85* Scott, A. Occupational Dermatosos of the Paraffin Workers in Scottish Shale . Oils. Brit. Med. J., 3.28.22, 381-5 . 56. Sequoira, J. E. Cancer and other Diseases of the Skin Caused by Minoral Oils. Konya qnd E. African Mod. J., 6, 18-23 (1929) . 87. Smyth, H. F. Review of Literature for 1926-193^, iac. Report of Committee on Industrial Skin Irritants to dm. Public Health Assn. . 88. Southa m and Wilson. Cancer of the Sprotun. .Brit. Med. J,, 2, 971-3 (1922) 89. Speaknan, J. 3. and Chamberlain, N. H. Trans. Faraday Soc., 29, 367--S (1933) In a study of the carcinogonlc pptency of mineral oils, Twart has shown that `the addition of glycerides reduces their potency, although no . oil qurpassos lanolin in this respect. . ., l,90. Toleky, L. Occupational Cancor. Acta d. Intemat. Ver, f. Krobshekonpfusg, 253-75 U93S) Several isolated coses of lung cancer among generator workers have been reported and among works exposed to coal lust, tar and tar distil . latos, but the somber is snail* 91. Toutschlaonder, 0. Industrial Cancer, especially tho Typos Occurring in Germany. Z. fuor Krebsforsch. ^2, 614-27 (1930) Discussos x-ray cancer, cancer of briquetto workers, mule spinnors1 cancer, which has not appearod in Germany, and paraffin cancer among tho so who work in the petroleum industry. 92. 5crutaciilaoiidoi>, 0. Occupational Cancer, with Spocial Consideration of its Prevention and Legislation on tho Suhjoct. Med. Walt. 11, 1267-72 (1341-5 (1937) ~ Occupations ir. which there is danger of dovelopmont of cancor are reviewed* many data are given regarding substances considered carcinogenic, API 04645 29- the location of malignant tumors, their latont period, protective measure of an Industrial-hygienic typo, quostions of insuranco, otc. There is no sp. agent common to all carcinogenic substances as a pronoter of cancer growth. . Touschlaonior, 0. Does Tar Require Ultra Violet Light to Produce Skin Cancor? Klin. Wchnschr., 16, 12SU-5 (1937) Whito nico wore paintod with tar. Cancers developed not only in the irradiatod aninhls hut also in thoso kopt in a dark chanter so that not only a preparatory but also an independent cancorogenic effoct oust be ascribod to |ar. . ., Toutschlaender, 0. Light and Skin Cancer. Ztschr. f. KrobBforsch. 50, Sl-92 (19^0) . The author investigates the problen of shether cr not a photodynanic influence is necessary in tho genesis of tar cancer. Ho conducted ex periments on tarred nice kept ip a dark roon. Since skin cancor developed on tho painted skin, it is ovidont that ultra-violet light is not a requisite in tar cancor genesis. The sane is shown by the development of spontaneous skin cancers in two wild groy house nice that lived in a briquet factory. .Nevertheless there is a widespread boliof that both cancer of radiant source and tar cancer of the Bkin are caused by cyclic hydrocar bons. According to Boffo, both typos are originated by oxidation and decomposition of oholesterol |n the tissues which nay be causod by radia tion as well as by chonlcal influence--cancer-provoking cyclic hydro carbons aro finally generated. Prophylaxis must, therefore, guard against tho influence of on? or both factors. ... . Touraino, A. and Bour, H. Cancer from Lubricating Oils, Rev. Mod. Franc. 20, 285-92 (1939) -. A very complete review of cancor from lubricating oils, its occur rence, . cliniaal symptoms and tho medico-legal aspects of such.cases. Twort, C. C. and Zsg, H.R. Mulo Spinners' Cancor and Mineral Oils. Lancet 1, 752 (1928). . ; " Twort, C. C. and Fulton, J. B. Xxporiaonts on the Nature of the Carcinogenic Agents in Uinoral. Oils. J. Path, and Bacteriol., ^2, 1U9-I6I (1929) From a consideration of the chemical reactions involved, tho authors are of the opinion that it is to benezonoii hydrocarbons that cortain mineral oils owe their carcinogenic properties. Treatment of tho oils with sulfuric acid led to almost total abolition of their car cinogenic properties, and similar rosuits were obtained by the adoption of methods of oxidation.and reduction. Twort, C. C. and Twort, J. M. Studios on tho Origin of Cancer. Ztschr. f. Krebsforsch,, 2, U91 (1930) This is a general survey of the work of the Tworts, and is based on experiments on ^5,000 mice, & smaller number of rata, guinea-pigs, rabbits, and on the use of some hundreds of varieties of tars and oils of various capacities to cause cancer. There is but little probability that an acquired physiological immunity against cancer-producing substancos oxists. Tho authors' various substances are divided according to their API 04646 *30- cancer-forming capacity in mice, so that every group has about ton times _ the power of the preceding ono. 99. . 100. Twort, C. C. and Twort, J. M. Classification of Four Thousand Experimental Cil and Tar Skin Tumours of Mice. The study from which this classification was made was based upon 29,100.animals. , Twort, C. C. and Fulton, J, D. Further Eaqporimonts on the Carcinogenicity of Synthetic Tars and Thoir Fractions. J. Path. Bact. ^1, 119-43 (1930). 101, Twort, C, C. and Twort, J, M. Tho Carcinogonic Potency of Mineral Oils. J. Ind. Byg. 5, 204-22 6 (1931) . Painting mice with refined shalo oil induces cancer more roadily than painting with refinod potroleum well oil. The most potent fraction from shalo oil is unfinished lubricating oil from which most of tho paraffin wax has boon removed but which had not been treated with BgSOi; and filterod. Tho 4 heavier grade oils are lest potent than spindle oils. The Cancer-producing property of oils appears to be relatod to fluores cence. Oils having a bluo fluorescence soem more active than thoBo having a groon fluoresconce, Chrysone dissolved in oleic acid possesses carcinogonic properties, 102. Twort, C. C. and Twort, J. M. The Bolative Potoncy of Carcinogenic Tars and Oils. J. Hyg., 29, 373-9 (193D . A mothod baSooen devised whoreby the potoncy of any givon carcino gonic agent can be compared with that of a standard agent. A unit of carcinogenicity- UX. - has been established, and a concentration of 500 carcinogenic units por cubic centimeter is considerod to induco the maxisum rolativo rospouse in a niaals whon tho agent is applied twico a week. The carcinogonic powors of oils rato as follows, in descending order; Shalo, Venezuelan, Bo moo, Bunanlan, Persian, Californian, Mexican, Mid*-Ccntinental, Texan, Pannpylvaaian, and Russian. Byppthotlcal standard agent Penn, pdl . Cal. pet. oil Oil Bo. 3 Shale Oil Pitch Gas tar Pinepe synthetic tar Effoet of refining Ponn. pil Mothyl sulfite oxtract Oil Bo. 3 Distillate 300-380<>C./I2nn Methyl sulfite oxtract Shale oil ' Oxidized at 150-l60C. Pinono synthetic tar concentrato Oxidizod at 100C. Cxiiizod at l(SO-l6oC. 100,0 0,1 3.* 0..6 4S.0 25,0 94.0 706,0 . 0,1 22,0 0,6 12,0 53t 48,0 0,3 3745.0 2369.0 58.0 API 04647 '31- J] Twcrt, C. C, and Pulton, J, D. Concentration of the Carcinogenic Principle in Oils and Tars. J. fuor KrebBforsch. 2, 543-73 (1932) In tho attempt to osbobs U.C, by physical and chemical characteris tics, the specific gravity, refractive index and iodine number appeared noBt pronising, though other features nay also ultimately prove to bo of value. Twort. C. C* and Lyth, E, The Selection of Non-carcinogonic fron Carcinogenic Oils. J. Hyg., 21, 461*--73 (1933) All the animal and vegetable oils tested by the authors on animals have proved to be incapable of inducing tumor formation during the life of their animals . On the other hand, oleic acid and linoleic acid, unsaturated fatty acids which nay be present in commercial saponifiable oils, have frequently Induced tumor formation; observations which in thoir opinion are of the highest importance in relation to many cancers other than those of tho skin, and possibly even of those of the skin it self. It has been found that the carcinogenic constituents of a given crude are not equally distributed in the various products of distillation obtained fron this crude The activity of the first products to come over in tho still, the motor spirits, etc., is negligible, and that of the lamp oils, burning oIIb, light fuel, etc., is also of little account, but when we reach the boiling rango of tho lubricating oils a definite carcinogenic activity may become manifest. Among the latter the most active grades are, on the whole, the spindle grades, closely followed by oils of a Eeiwood viecosity of $00 to 1500 at 70 P., with a gradual docroase in activity as one approaches the Internal combustion engine (motor car) grades. The crude oils themselves, as a rule, aro somewhat Iobs potont than the motor ear oils, but of course, it will necessarily depend upon tho amount of refining to which the latter have been subjected bofore.being marketed. . ' . Tnort, C. C. and. Twort, J. M. Carcinogenicity of Spindle Oils. Oil and Colour Trades J., 1193-4 (1937) . A physical aSS an a nimal test for oarcinogenicity and a physical and an animal test for dermatieity of mineral textile oils are described. The average results of these tests on 66 oils (excluding shale oils) collect ed 5-10 yrs. ago and on 66 oils collected recently are tabulated. (The animal test for carcinogenicity is not yet completed for the recent oils.) These results Indicate that the original oils are definitely worse than the recent oils in both the dermatitis tests, while in the cancer physical test there is no significaht difference. It is expected that tho figures for the' recent oils in the animal tost of carcinogenicity will be lower than these of the original oils. --- It is concluded, however, that little is being dono to improve mule spindle oils fron the biological standpoint. There aro also indications that the average oil used in some of the cotton-spinning towns is more dongorous than that used,in others. , Twort, C, C. and Twort, J, M. Notes on Sone of the Procedures Adopted for Assessing the Biological Activity of Mineral Oils. Oil Colour Trades J., 251-5 (1938) . .' Mineral oils nay induce dermatitis or cancer of tho skin. In dotg. tho carcinogenic aspect 3 essential detns. are made: d., n and kinetic 04648 API -* viscosity (VI), The data collected are based on the utilization of. formulas for assessing the biol. activity, especially from its carcino genic aspect. In Formula A, R = (n-l)/d where R = sp. refractivity, n = refractive index and,d * density. In Formula B, R = n-(d/2). Formula A is used in obtaining the cancer refractivity CR from Formula C which is CR Re 3(4-0.900)/20. In Formula D the refined cancer re fractivity RCR = CR - (KV/50). Results, where thpso mineral oils havo bpon employod, ore shown in tables in which mineral oils are grouped according to toxicity and according to the n drop. Tho significance of d. in rolation to tho n drop among oils of similar toxicity and the significance of viscosity in relation to tho n drop among oils of apparently similar toxicity aro Bhown. Tho real difficulty in arriving at tho true biol. activity with greater accuracy is the lack of uni formity pf tho inert fully hydrogenated constituents. There is quite good correlation betweon caroinogonicity, refractivity, n drop and . toxicity. ' . 107. . 108. . Twort, J, M. and Lyth, R. The Concentration of Carcinogenic Materials in Mineral Oils by Distillation Prccessos. J, Hyg. 22.* 161-9 (1939) Twolvo acid-treated lubricating cuts of a crude, Borneo mineral oil, wore testod for carcinogenic activity. Tho wholo range was bio logically active, which activity had boon foreseen from an examination of tho physical dharaotoristies. Tho poak activity was around a vis cosity of 200-250 Centipoisos at 25 C. Molecular distillation gave a groater concentration of the carcinogenic material than ordinary dis tillation at from 3-10 nn. In confirmation of previous findings, the middle fractions of a Borneo orudo.oil were mostly responsible for pathological changes in tho organs--fatty infiltration of th6 liver and hyaline degeneration of the spleon. Dong tumors were more prcvalont than is usuai when this type of agent is usod for testing carcisogenity for tho skin. Their incidence was rathor higher in the more viscous fractions: this inoldonoe was apparently not correlated with carcino- gonity.for the skin* Twort, J, M. and lyth, R.' Skin Cancer due to Handling Coal Tors Used for Preservation of Tifhing Sets* Nature, 3)44, 446 (1939) Several fishermen contracted cancer of tho skin after .handling the tars. Mouse eapts. showed that different eoal taTs differed in their ca rciaogenie activity, although ell producod soap cancers. Creosote oil and anthracene oil were also carcinogenic. Only coal tar nado in vortical low-Wtp. retorts should be used on nets. . 109. Twort. C* 6. Male-Splnnors * Caacor: Die Nood for Using the Correct Oils. 011-eolourTrados J., 8*29.41, 326 fhe eancar-producing powers of ninoral oils used in the cotton industry from dlfforont fields of origin, in tho crude and refined statos, wore thoroughly examined and tho resul ts showod that,there is a danger of any one producing cancer of tho skin if applioi long onough but tho oils from oortain fields are tho noro likoly to do so. Special attontion was paid to fhe examination of the physical characteristics of various mineral oils, and it was proved that a knowledges of their refractive index and viscosity provides a noro reliable estimate of their cancer-producing powers than the application of the sample to the skin. This test is accurate, rapid and inexpensive, while that with tho Bkin is variable, lengthy and costly. API 04649 BS- The chiof lino of investigation has "boon a continuation of the work on tho molecular distillation of mineral oils with tho ohjoct of isolat ing the substancos responsible for thoir carcinogenic activities. Animal oaqjorinonts with fractional iistillatos from a Vonezuolon oil aro in progress. Fractions obtained by nolocular distillation of a carcinogonic shale oil have boon subjoctei to chromatographic absorption and two apparently puro hydrocarbons havo boon isolatod in small quantity; those aro being investigated chemically. Fainting experiments with fractions obtained by this mathod hayo shown that many of thorn aro highly toxic for nico. None of the substancos so for tostod has boon shown to possess a high carcinogonic activity. A few spindle grade oils and threo oils intended as vohicles for Insocticides have boon tosted for carcinogenicity. A. colloidal material intendod as a protective against carcinogenic oils has boon tested. Thero aro indications that it has sone protective action. Tho carcinogonic activity of two products formed during the purifi cation of carbonisation has boon tostod, and found to bo loss than that , of the avorago gas tar. . 110. Ullmann, K., Oppenheim, U. and Eille, J. E. J. Ind. Hygiene, 8, 288, 364 (1926) "' Tho lesions caused by crude petroleum are the sane as tho so caused by crude coal tar, showing the analogous substancos must bo present in both. The final products of distillation aro tho most active, 0specially paraffin oil. The carcinogenic agent is presont in fractions from 200 0. to 4^0 C., but it is not cortain that tho sane substance CBusos both dermatitis and epithelioma. ,, 111. Yalado, P. Cancer of tho Hman lung from Dust from Tarred EoadB. Fresso Mod., . 2.1.39, 161 . . . . 112. . Van Therdscho, M. X. Chemical Cancer. Ing. Chin., 20, 30-5 (193) Uoro than twico as many casos of cancer due to soot wore found among swoopere then raong any, other occupation. Personal eloanllnoss and clothing that fits tightly'around the oxtremitios and around tho nock aro the bes$ peeventiwae. Similar care will do much toward preventing cancer due to exposure to gasoline and its derivatives, paraffins, oIIb, and groases. Such precautions are ovon more nocoesary in eases exposed to tar, pitch, rosin or aniline dyos. Strict medical sup ervision and tho use of proceases which avoid contact of tho workers with tho product will furthor redn.ee the danger. ,. 113. Wampler, J. J. Occupational Diseases of the Skin (by L. Schwarz). "Indus trial Medicine", 1943, 327-9 Chimney sweeps1 cancer has been reported in England more frequently than in any other country. It is said that the Incidence of cancer among chimney sweeps is eight times more common than among the general population. Ca ncer of tho scrotum of chimney swoops, however, is on the decline in England and it is reported as being practically non-esistoat in othor countries, except for an isolated casp or two in Germany. Tho local irritation and rubbing in of the soot as the swoop is cramped in descending tho chimney is said to be tho cause. API 04650 Tar is usod in building roads, in making roofing paper and folt. Pitch is used for making conduits, lacquers, insulating matorial, groasos, and mineral cements, and workers at thoso occupations aro affoctod with comedonos, tumors, warts, koratosos, and opitholioma, mostly of tho scrotum, lip, face and hands* No cases of mulo spinners' cancer havo boon roported from Franco, Germany, Russia, or Poland. Tho author nodo examinations of thousands of nulo spinnors employed in tho Unitod States and did not find any cosos of scrotal cancor, although thoro wore maiy casos of folliculitis and koratosos of tho thighs caused by oil-soaked trousors. . , llU, . Waniok, H* kolanodorma and Keratoses from the Action of Asphalt. Arztl. Sachverst. Ztg., 66, 49 (1940). In th? preparation of cork plates (heat-insulation plates of asphalt and cork) such dust develops under very unfavorable working conditions. Two wprkors, who had boon working for threo months, suffored from pignontation, inflammatory changes and hyperkeratoses of tho face, forearms and hands. Tho hypexplastic procossos wore,intensified in the older workers* The symptoms wore aggravatod by light. The intensive action Qf asphalt dust is considered to bo tho cause* 115* . Watson. A. 7*. Tar Cancor in Mice, III, An Apparatus for tho Preparation undor Standard Conditions of a Bigily Potent Carcinogenic Agont of Low Toxicity. Brit. Jour. Ixpor. Path., 12, 44L-7 (1931) . With an ada ptation of the apparatus of Hague and Whoolor tho author has tuoceeded in naldag from purified turpentine, at 8900 C. a relatively aon-toxio tar which olicitod tumors after 210 days in 90$ of tho survivors from a group of 37 nice; most of these growths were malignant* , ., 116. . Wolwart. Cancer from Paraffin fax and Mineral Oils* Soifona. Ztg., 62, 792-3 (1935) " Host chemists and dermatologists boliovo that workors in paraffin factories got cancor from the paraffin itsolf whilo Schorbor and Toutsch- laender claim that eaneer does not cono from paraffin but from mineral . . .. 117. TTindaus, A. and Bennhak, 3* Soso Derivatives of 3,4-Benzopyreno. Z. Physiol. Chon. 24$, 256-66 (1937) By analogy to xrays( roys produco and arrays euro cancer") , carcinogenic hydrocarbons should bo tested for possible thorapoutic values* Suggos tive rosul ts havo boon obtained with 3,4-bonzopyme, (I)* 118. Wood, 7. C. The Nos-Corelnogonic Nature of Purifiod Mineral Oils. J. Ac* Mod. Assn., 24, l64l (1930) ' Tho gonoral clinical ovidenco that thoye exists no rolation botwoen tho therapeutic use of refinod potroleun products and the oceurronco of cancer is confirmed by experimental studies* , 119* Wood, H, B. Paraffin Not Productive of Cancor. J. Cancor Bos*. 13, 97-102 . (1929) . Tool H. B. Skin Losioae Among Tar Workors. J. Cancor Hos., l^i 54-9 (1929) Different typos and composition of tars are discussed. Only tar obtained from tho distn. of coal at high temps. contains a substance i i 1 API 04651 -38** carcinogenic to certain lab. animals. Workmen handling coal tar showed , tar warts as a result, hut no other effect. No irritant action on the . human skin was found from low temp, distillate tar or from.petroleum, tar. 121, Woodhouse, D. L. Carcinogenicity of Synthetic Lubricating Oils. J. Inst. Pet. Tech., 20, 1057-63 (193*0 . 122. Yamagiwa and Ichikawa. Experimental Study of the Pathogenesis of Carcinoma. J. Cancer Res., Ill, 1-21 (1919) In 1915 produced cancer by the experimental application of tar to tho ear of a laboratory animal. API 04652 FOR INFORI'ATION ONLY - NOT FOR PUBLICATION A CONTRIBUTION OF INFORMATION TO IT!BINS OF A.p.I. I^OICAL ADVIRPRY COI7TTTEE SHELL OIL COMPANY, INCORPORATED WOOD RIVER RESEARCH LABORATORIES REPORT NO. M-12^7 JULY 2, 19^5 CABCCTOGBUC HYDROCARBONS AND RELATED CQMPOUHDS A LIBERATORS REVIEW H. H. ZUHOEMA API 04653 Exportation of This Report is Subject to License Under the National Defense Act SHELL OIL COMPANY, INCORPORATED WOOD RIVER RESEARCH LABORATORIES REPORT NO. M-12^7 JULY 2, 19*0 SUBJECT: CARCINOGENIC HYDROCARBONS AND RELATED COMPOUNDS A LITERATURE REVIEW AUTHOR: H. H. ZUTUEMA Industrial cancer vOs first recognized In England in the latter part of the eighteenth century, when It was established that chimney sweeps were particularly liable to cancer of the scrotum.3 This was caused by soot. Progress In this field of study was very slow at first, and It was not until 1915 that two Japanese Investi gators announced the first case of carcinoma In an experimental animal. They produced first papillomas and then true cancer of the epidermis on the ears of rabbits by painting with tar over long periods of time. 39 During the thirty years that have elapsed since that discovery, a great deal of work has been done with various coal tar and petroleum fractions and pure compounds either occurring in these fractions or prepared synthetically. Numerous species of tost animals, Including mice, rats, fowl, rabbits, and dogs have been used, and many methods of application, Including oral administration, Intramuscular, Intravenous, and subcutaneous Injection, and painting on the akin. The method that appears to be the most widely used at present consists of painting a solution on the akin of a special In bred strain of sloe. Mice are preferred over animals having longer life-spans since they respond more rapidly. The special strains are used to Increase the precision of the test. Painting la preferred to other methods of application because there la less likelihood of Interference by simultaneous spontaneous carcinomata. The carcino genicity of a given ocmpoupd Is influenced by many factors including the genetlo constitution of the animal species and strain, Its age and sex, the diet, the physical condition of the animal, the purity of the compound, the dose, the physical state of the compound, the solvent used, and the route or site of application. 2 5 While carcinogenic properties are generally associated with certain polynuclear aromatics and their derivatives, there are many substances entirely unrelated to these compounds which have been re ported as having similar cancer-producing ability. Among these may be mentioned asbestos54'57 , inorganic compounds of arsenic end of zinc25, aqueous potassium hydroxide end aqueous hydrochloric acid25, ethyl alcohol 5, glucose3 5, fructose2 5, and a auabcr of nitrogen compounds, most of which contain one or more benzene rings25. Radio active elements and compounds are not included in this discussion since the mechanism of their producing cancer la probably quite different, i.e., physical rather than chemical. Materials which havo been roported API 04654 Beport No. M-1247 2 as carcinogenic and whose carcinogenicity is probably due to the prejence or polynuclear aromatics include coal tar and pitch26'27 blue shale oil5, mineral oils and asphaltu~, tobacco tar39, tars obtained in the destructive distillation of teauand coffee40, diesel fuel52, distillates from Borneo crude petroleum5'4, combustion gases from fuel oilul, the SOo extract from a spindle oil produced from a paraffinic crude petroleum54, the products obtained by heating acetylene, isoprene, yeast, a non-careinogenic petroleum fraction, or human shin to' 700 - 900C-J0, and the products obtained by treating acetylene, xylene, naphthalene, or tetrahydronaphthaleno with aluminum chloride3 . The carcinogenicity of tars produced by heating various substances tends to increase with increasing temperature.3 14 s it is probable that the carcinogenic hydrocarbons present in certain coal tar and petroleum fractions were to a large extent formed during the process Bteps and were not present in the coal or crude petroleum from which they were derived. However, the carcinogenicity of a given fraction depends upon the source as well as the method of processing, according to the Manchester Committee on Cancer49, the following order of increasing carclnogenlolty prevails: Russian, Pennsylvania, Texas, Mid-Continent, Mexican, California, Persia, Romanian, Borneo, Venezuela, and shale. Ala corresponds roughly to the order of increasing aromati city. . A large number of compounds have been tested for carcino genicity. Hartwell has published a survey25 which Includes 696 compounds tested. Of these, 146 were carcinogenic, and 23 additional ones produced papillomas but no true cancers. While some of these compounds have been tested under only one or two sets of conditions, others have been studied vary extensively. The three compounds that have received the most detailed study are the three derivatives of 1,2-benzanthracene: 1,2,9,6-dibeozaathaoene, 3,4-benzpyrene, and 20methylcholanthrene. All three are potent carcinogens. It has been estimated that they have been investigated in 60 different labora tories.20 A list of most of the known carcinogenic compounds is given la Table l,pcgce 5JQ, Structures, complete with numbering systems, are included, since lack of uniformity among various in vestigators in this field has led to some confusion. There is fortunately lees deviation in the current papers than in the case of thoae written ten to fifteen years ago. lhe numbering used in this report corresponds to that used by Hartwell25. It should be understood that the carcinogenicity of the-compounds shown in Table 1 varies considerably in degree and that the results have been verified by several laboratories in some cases whilo in others the results of only one or two experiments are available. Bie reader is referred to Hartwell for more detailed information and for re ference to the original experiments. It will be observed that most of the compounds are either hydrocarbons or their derivatives containing at least three benzene rings or nitrogen compounds con taining at least two benzene rings. More specifically, the first of these classes consists, with only throe exceptions, of derivatives API 04655 Report No.. M-1247 3 of phenanthrene. The exceptions are tetraphenylmethane, trlphenylbenzene. and trlphenylethylene. In Table 1 the hydrocarbons are subclassLfled further as derivatives of 1,2-benzanthracene, 3,4-benzpyrene, cholanthrene, end other derivatives of phenanthrene. Examination of the structures shows that all of these are derivatives of phenanthrene. While the work that has been done on the production of cancer by exposure to various compounds has made It possible to draw certain conclusions regarding the effect of chemical structure, It Is not as yet possible to predict with any degree of certainty the carcinogenicity of a given compound from Its structure. A phenanthrene derivative may or may not, for example, be carcinogenic depending upon such factors as the length of an alkyl side chain, ^he position of a benzene ring , or tho position of an alkyl group. However, a paraffinic or naphthenic hydrocarbon or one containing only one or two benzene rings may with a reasonable degree of confidence be assumed to be non-carcinogentc. The amount of compound required to produce an experimental cancer on a test animal Is surprisingly small. Coses of 1,2,^,6-di benzanthracene and 3,4-benzpyrene as small as 2.5 and 4 micrograms, respectively, give positive results when applied to mice.^-'Discontinuous application, e.g., once a weok, of a given total quantity of material Is moro effective than continuous exposure.15 A single application of 20methylcholanthrono In 0.6^ bontone solution Is capable of producing cancer on the akin of mice. Us lbea different carcinogenic hydrocarbons, e.g., methylcholanthrone, benzpyrene, and dlbenzanthracene, are applied successively the effeot Is additive33. The investigators who made this observation offer the hypothesis that carclnogenlsls Is essentially an acciznulatlon of abnormal protein within the cell. Since eo many compounds have been tested for carcinogenicity It is only natural that several attempts have been made to correlate this property with other properties, either physical or chemical. Such a correlation would be extremely useful In that the determination of the physioal or chemical property would be such simpler than the rather long and tedious prooess of exposing experimental animals to the substanoe in question, ylooresoenoe spectra have received more study in this regard then sny other propertyp.7.88. ^The author of a reoent paper made the statement that all known oarllnogenlc chemicals are fluorescent.113 However, It la obvious from a glance at Table 1 or Hartwell's tabulation that this la too broad a olalm. However, many Investigators have used fluorescence spectra to good advantage in this field, and there appears to be a definite correlation with carcinogenicity, at least with certain types of compounds. The correlation may be due In part to the fact that fluorescence spectra have been used as a guide in selecting fractions from coal tar for physiological tests; it is conceivable that other carcinogenic com pounds, which are not fluorescent, exist or could be synthesized. A rough parallelism between the carcinogenicity of poly nuclear aromatics and the dlazo coupling reaction has been observed.21.22 Attempts have also been made to correlate refractive Index, or more specifically, specific refraction, with the carcinogenicity of oils. API 04656 Report No. M-12^7 k The Manchester Committee on Cancer49 recommended that spindle oils of various ranges of specific gravity have specific refraction values below certain limits to assure the absence of carcinogenic properties. However, it is obvious that thore can be no general correlation between a physical property of this nature and carcinogenicity, for slight changes in structure, such as the position of a methyl group, which would have little effect upon optical properties, affect carcinogenic properties profoundly; furthermore the presence of a large concentra tion of a non-carcinogenic aromatic would raise the specific refraction of a mixture much more than would the presence of a small amount of a potent carcinogen. The probability of obtaining a general correlation between carcinogenicity and some more easily determined property would be greatly enhanced if there were a clearer understanding of the mechanism of the action of carcinogenic compounds. It is, of course, very difficult to obtain such an understanding, for so little Is known . about cancer itself. Whether or not carcinogenisis by hydrocarbons and related compounds is in any way connected with spontaneous cancer is a question that has received much conjecture. That such a relationship does exist is suggested by the fact that certain derivatives of estradiol (see Table 1) which Is closely related to the sex hormone estrone, are carcinogenic. Spontaneous cancer quite often occurs in the reproductive organs. Furthermore, the very potent carcinogen, 20-methylcholanthrene, can be produced by the degradation of deaoxychcllo acid, cholic acid, or cholesterol, the first two of which are normal constituents of human bile and the last of which is present in all tissues of the human body.2*2 These degradation reactions were, however, conducted under drastic conditions which are in no manner related to those prevailing physiologically, and there is no evidence that 20-methyloholanthrene Is formed in the body through the degradation of bile acids or cholesterol. The possible connection between cancer produced spontaneously and carcinogenisis by sethylcholanthrene or related compounds therefore remains a matter of conjecture, at least for the present. There has, for obvious reasons, bean little attempt to induce cancer in human beings through exposure to the various com pounds that are carcinogenic to mloe. There is, therefore, no direct correlation between the susceptibility of man and the test animals. There is, of course, an Indirect correlation of occupational cancer largely through exposure to coal tar and dye intermediates caused by materials which are carcinogenic to mice. However, many of the compounds shown in Table 1 do not occur in any products known to have caused occupational cancers, and it is conceivable that some compounds harmful to mice are innocous to man. until that can be proved, the only safe policy is to regard all compounds which are harmful to mice as dangerous and to avoid exposure by humane. EEZ:VAC API 04657 Report No. M-1247 5 TABLE 1 CARCINOGENIC COMPOUNDS All compounds listed by Hartwell25 unless otherwise indicated. 1. Derivatives of The following derivatives of 1,2 -benzanthrac ene: 3-methyl 5-methyl 6-methyl 9-methyl 5-ethyl 10-ethyl 5-n-propyl 5-n-butyl2 5-n- amyl2 5-n-hexyl2 . 6-i-propyl 3-hydroxy 10-hydroxy ^ 10-aldehyde, -C 0 H0 lO-methylaneacetcxy, -i-O-C-CH^ E H0 i 10-methylenecarboaetboxy, -C-C-0-CH3 H H i lO-cyanomethyl, -C-CN H 3-methoxy 10-methoxy 4.9-dimethyl 4.10-dimethyl 5.6-dimethyl 5.9-dimethyl 5 ,10-dimethyl 6.7-dimethyl 9.10-dimethyl 6,7-dimethyl 9,10-dimethyl 5-chloro, 10-methyl 7-chloro, 10-methyl 5-cyano, 10-methyl 7-cyano, 10-methyl , 1,2,7,8-dibenzanthracene31 1,2,5,6-dibenzanthrac ene API 04658 Beport Ho. M-1247 6 The following derivatives of 1,2,5,6-41130112 anthracene: 9-methoxy 2' -methyl 3'-methyl 4-methyl 9-methyl H 1' ,9-methylone -c- EH 4.10-dimethylone, -6-C- ' HH 3,4" -dimethylene (phenanthra- 6,9-dimothylene acenaphthene) 2. Derivatives of HHH 5.6-oyolopenteno -6-C-(j- HHE 6.7-cycloponteno 1', 2 ', 3 ', 4-' -tetrahydroNa salt of 9,10-endo alpha,beta succinic acid: 5-aldehyde 4-' -methyl 5-methyl 1',2''-dihydro, 4'-methyl 3. Derivatives of Cholarsthrscene l',2',3',4'-tetrahydrc 10-acetyl 3,4,8,9-dihenzpyrene 5,10-4ihydro-3,4,8,9-di benzpyrene 7-methyl,1,2,3,4-dibenzpyrene Cholanthrene The following derivatives of cholanthrene: 20-methyl 20-ethyl 20-isopropyl 20-tert-butylJ u 15.20- dimethyl 16.20- dimethyl 15-hydroxy, 20-methyl 15-heto, 20-methyl API 04659 Beport No. M-12^7 k. Other Derivatives of Phenanthrene Colchicine 7 The following derivatives of 3, 4-benzphenanthrene 1-methyl2 2-methyl2 2-ethyla 2-isopropyl2 7-methyl2 8-methyl2 2,9-diethyl 2-methyl, 1,2,3,4- dihenzphennnthene Cholesterol oleate 1,2-dimethyl chrysene2 5-methyl chrysene17 4.5-methylene chrysene17 5.6-dimethyl chrysene17 API 04660 Beport No. M-12U7 8 Eguilonin "benzoate 0 Estradoil caprylate 0 CH j-(CE2) r,-C-0' 1,2-cyolopentene phenanthreno2 5. Other Aromatic Compounds Te traphonylmothane 1,3,5-triphenylbenzene Trlphenylothyleno 33 API 04661 Report No. M-1247 6. Organic Compounds Containing Nitrogen 2-amino, 1-naphthol Alpha naphthylamine13 Eeta-naohthylanine * 0II O| H Acetylcholine, CH3-C-0-CH2-N-(CH*)3 o-amino azotoluene rv p-dimethyl aminoazobenzene (butter yellow) 9 Scarlet red r~\CH, / 7~\ N = N \ \_y / /\ Indole W Syyryl 430 H Benzidine1' -NHa . API 04662 Report No. M-12^7 10 1,2 1,2,7,8-dibenzacridine 3,4,5>6-dibenzcarbazole 7. Miscellaneous Arsenic trioxide Potassium arsenlte Aqueous hydrochloric acid Aqueous potassium hydroxide Zinc chinrids Zinc sulfate Ethyl alcohol Fructose Glucose Galactose API 04663 Report No M-1247 BIBLIOGRAPHY 1. Auld, S. J. M., J. Hist. Pet. Tech., 24, 577-33 (1936). 2. Badger. G.M., Cook, J.W., Hevett, C.L., Kennavay, E.L., Kennavay, ' N. M., Martin, R.H., and Rotlnson, A.M., Proc. Roy. Soc., B129, 439-67. (1940) 3. Badger, G.M., Cook, J.W., Hevett, C.L., Kennaway, E.L., Kennaway, ' N.M., and Martin, R.H., Proc. Roy. Soc., B131, 170-82 (1942). 4. Barry, G-, Cook, J.W., Haslevood, G.A.D., Hevett, C.L., Hleger, I., and Kennaway, E.L., ibid, B-117, 313-51 (1935). 5. Berenhlum, I., and Schoental, R., Brit. J. Erp. Path., 24, 232-9 (1943) 4 6. Bottomley, A.C., and Tvort, C.C., Am. J. Cancer, 21, 781-3 (1934). 7. Bruce, V.F., and Todd, F., J. Am. Chem. Soc., 6l, 157-61 (1939) 8. Campbell, J.A., Brit. J. Exp. Path., 15, 287-94 (1934). 9. Campbell, J.A., Ibid, 20, 122-32 (1939) 10. Cook, J.W., Nature, 14^, 335-8 (1940). 11. Cook, J.W., Haslevood, G.A.D., Hevett, C.L., Hleger, I., Kennaway, I.L., and Mayneord, W.V., Am. J. Cancer: 2g, 219-59 (1937). 12. Cook, J.V., and Kennaway, E.L., Ibid, 50-97 (1938). . 13. Cook, J.W., and Kennaway, E.L., Ibid, 39, 381-428, 521-82 (1940). 14. Oook, J.W., Hleger, I., Kennaway, E.L., and Mayneord, W.Y., Proc. Boy. soc., Bill, 455-84 (1932). 15. Cramer, V., and Stovell, R.E.,Cancer Research, 3. 668-81. (1943) 16. Dobrovolskaya-Zavadskayu, N., Compt. rend. soc. biol., 129-, 1055-7 (1938). 17. Daalap, C.E., and Warren, S., Cancer Research, 3, 606-7 (1943). 18. Evans, E.E., J. Urol., 38, 212-15 (1937). ' 19. Fieaer, L.F., "Chemistry of Phonanthrone", Reinhold Publishing Company, N.Y., (1937). API 04664 Report Ho. M-I2U7 Bibliography (Continued) 20. Fleser, L.F., Am. J. Cancer, 34, 37-124 (1938). 21. Fleser, L.F., and Campbell, W.P., J. Am. Cbem. Soc., 60, 1142-5 (1938). "" 22. Fleser, L.F., and Fleser, M., "Organic Chemistry", pages 814-26, Heath and Co., Boston, Mass., 1944. 23. Gottschalk, R.G., Proc. Soc. Exp. Biol. Med., 2, 369-73 (1942). 24. Haddov, A.#, and Robinson, A.M., Proc. Roy. Soc., B127 , 277-87 (1939). 25. Hartvell, J.L., U.S. Public Health Service, Hat. Inst. Health, Hat. Cancer Inst., 1941, "Survey of Compounds which Have Been Tested for Carcinogenic Activity", 371 pp. 26. Heller, I., J. Ind. Hyg., 12, 169-97 (1930). 27. Henry, S.A., Kennavay, H.M., and Kennavay, E.L., J. Hyg., 31, 125-37 (1931). " 28. Hieger, I., Bioehem. J., 24, 505-11 (1930). 29. Hueper, W.C., J. Ind. Hyg., 16, 255-79 (1934). 30. Kennavay, J.L., Brit. Med. J., 1925. II 1-4. 31. Kennavay, E.L., Bioehem. J., 24, 497-504 (1930). 32. Kennavay, E.L., and Hieger, I., Brit. Med. J., 1930, No. 3622, 1044-6. '. - 33> Lavik, P.S., Moore, P.R., Ruech, H.P., and Baumann, C.A., Cancer Research, 2, 189-92 (1942). 34. Linzbsch, A.J., and Vedler, H.W., Arch. Path. Anat. (Virchow's), 307, 387-409 (1941). 35* Loeb. L., Alexander's "Colloid Chemistry", Vol. V, 995-1050 (1944), Reinhold Publishing Co., N.Y. 36. Morton, A.A., Clapp, D.B., and Brand, C.F., Science, 82, 134 (1935). " 37. Norimann, M., Z. Erebaforach., 47, 288-302 (1938). API 04665 Report Ho. M-124? thbiioaraphy (Concluded) 38. Robson, J.M., and> Bonser, G.M., Nature, 142, 836 (1936). 39. Roffo, A.H., Prensa Med. Argentina, 26, 721-38 (1939)* 40. Roffo, A.S., Bol. Inst. Med. Exp. Estud. Cancer, 1^, 741-56 (1939). 41. Roffo, A.H., Ibid, 16, Ho. 52j 1-6 (1939). 42. Roffo, A.H., ibid, 1J, 661-98 (1940). 43. Roffo, A.&., and Roffo, A.Z., Jr., Ibid, 20, 143-87 (1943). 44. Shear, M.J., Letter, J., and Perrault, A., J. Hat. Cancer Inst., 2, 99-113 (1941). 45. Simpson, V.L., and Cramer, V., Cancer Research, 3, 6o4-5 (1943). ' " 46. Stallybrass, C.O., J. State Med., ^4, 249-68 (1926). 47. Stovell, R.E., and Crtmer, v., Cancer Research, 2, 193-7 (1942). " 48. Tvort, C.C., and Pulton, J.D., j. Path. Bact., 33, 119-43 (1930). 49. Tvort, C.C., MiLyth, B., J. Hyg., 464-73 (1933). 50. Tvort, C.C., Ml Tvort, J.M., J. lad. Hyg., 13, 204-26 (1931). 51. Tvort, C.C., and Tvort, J.M., J. Hyg., 22, 373-9 (1930). 52. Tvort, C.C., and Tvort, J.M., ibid, 130-49 (1935). 53- Tvort, C.C., and Tvort, J.M., Lancet, 1935, II, 1226-8. 54. Tvort, J.M., and Tvort, C.C., J. Hyg., 39, 161-9 (1939). 55. Woodhouae, D.L., J. Inat. Pet. Tech., 20, 1057-63 (1934). 0 For those wishing to acquire a acre extenslre background in this field, a review by Fleser20 Is recommended as a good starting point, followed by the original papers by Cook and co-workers. For a detailed tabulation of carcinogenic compounds Hartwell's book25 should be consulted. API 04666