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208 GERBER Void Incidentally, only three of our five pa tients were known to have had occupational exposures to asbestos (labor in asbestos plant; tile manufacturing; pipe insulation). The other two presumably belong in the category of asbestosis of unrecognized ori gin. Asbestos bodies have been found at autopsy in the lungs of a large proportion of males without occupational exposure, the incidence in this country ranging from 25 to 97%.10*13'14 It is now clear that less intense grades of asbestosis, even minor or trivial ones, can not be excluded from consideration in the background of these malignant tumors. Du ration rather than extent of asbestosis ap pears to be decisive. An average interval of 38.7 years has been observed between ini tial exposure to asbestos and death from lung cancer.11 Less intense grades of asbes tosis are more likely to be associated with malignant mesothelioma. According to Selikoff the intervals between initial exposure to asbestos and pleural or peritoneal meso thelioma average 34.8 and 43.0 years, re spectively.11 Perhaps the amount of asbestos fibers inhaled by an ordinary urban dweller is sufficient to cause minor grades of pulmo nary asbestosis. Asbestos fibers may become widely disseminated by the blood and lymph throughout the human body. SelikolT has found them in bone marrow, kid ney, liver, adrenal glands, and spleen.0 The possibility that they also enter the circula tion by penetrating the mucosal barrier of the gastrointestinal tract after ingestion with contaminated food must also be con sidered. The first step in proving the develop ment of malignant tumors as a result of occupational or environmental exposure to chemical or physical carcinogens is the com pilation and presentation of data such as these. The association of such exposure with increased incidence of tumors does not conclusively prove per se their etiologic relationship. Final proof must await the experimental induction of tumors by the incriminated agent. Experience in mani ready suggests the propensity of many ty^ of tissue to develop malignant tumors the presence of asbestosis. These and otl hazards of asbestosis, one of man's adl tions to his own environment, are ind numerous--and frightening. Acknowledgment. Sylvan E. Mooltcn, M.D, Vr, dlesex General Hospital, New Brunswick, N ; granted permission for use of the material a helped in the preparation of this paper. References Gloyne, S. R.: Two cases of squamous cardnon] of the lung occurring in asbestosis. Tuftera 17: 5-12. 1935. :'4 Hammond, E. C.. Selikoff, I. J., and Churgi>| Neoplasia among insulation workers in tl United States with special reference to itvtn abdominal neoplasia. Ann. N.Y. Acad St 132: 519-525, 1965. ' Kappeler, R,, Gugler, E., and Riva, GV: `jj Fragc des atypischen Morbus Waldcnstrfli Schweiz. Med. Wschr. 51: 1331-1336, 1959. '>; Lieben, J.: Malignancies in asbestos worker! Arch. Environ. Health 13: 619-621, 1966i-j Lynch, K. M., and Smith, W. A.: Pulmonat asbestosis. Ill: Carcinoma of the lung inu besto-silicosis. Amer. J. Cancer 24 : 56-60, 198F 6. Mancuso, T. E., and -Coulter, E. J.: Methocftjl ogy in industrial health studies. Arch. .Et viron. Health 6: 210-226, 1963. r;$ 7. Mancuso, T. F., and cl-Attar, A. A.: Mortalii pattern in a cohort of asbestos workers.^ Occup. Med. 9: 147-162, 1967. .. $ 8. Moolten, S. E.: Symposium on industrial png) moconiosis in New Jersey: Pathologic mani testations. J. Med. Sac. New Jersey (to be puf lished). i 9. Selikoff, I. J.: Discussion. Ann. N.Y. Acad. Scj 132: 595-602, 1965. 10. Selikoff, I. J.: Asbestosis and neoplasia. Am. 'J] Med. 42: 487-496, 1967. .11. Selikoff, I. J.: Personal communication. 12 Selikoff, I. J., Churg, J., and Hammond, E, Relation between exposure to asbestos at mesothelioma. New Eng. J. Med. 272: 5 565, 1965. 13. Thomson, J. G., and Graves, W. M.: Asbesta as urban air contaminant. Arch. Path'. 8; 458-464, 1966. 14. Utidjian, M. D., Gross, P., de Treville, R. T. E) Ferruginous bodies in human lungs: PreV| lence at random autopsies. Arch. Envir.pt Health 17: 327-333, 1968. Ip 15. Vigliani, E. C., Mottura, G., and Maraniki P.: Association of pulmonary tumors with? bestosis in Piedmont and Lombardy. N.Y. Acad. Sci. 132: 558-574, 1965. 16. Wagner, J. C., Slcggs, C. A., and Marchand,J Diffuse pleural mesothelioma and asbestosiS posure in North Western Cape Province. J3|, J. Industr. Med. 17: 260-271, I960.- ":f 17. Webster, I.: Mesotheliomatous tumors in So: Africa. Pathology and experimental patholgj Ann. N.Y. Acad. Sci. 132: 623-646, 1965.1