Document YgE746mLd4bjvYJm3Yk8VJmn

V Occupational Health ! HAZARDS OF THE WORK ENVIRONMENT May R. Mayers, M.D. Formerly, Assistant Director, Chief of Medical Unit and Editor of Publications Division of Industrial Hygiene, New York State Department of Labor THE WILLIAMS & WILKINS COMPANY BALTIMORE 1969 PLAINTIFF'S EXHIBIT B&R-l I i i Copyright , 1969 The William* <k Wilkin* Co. 438 B. Preaton SL Baltimore, Maryland 31303 USA. Made in the United Stale* of America Library of Congret* Catalog Card Number 68-9180 Compoted & Printed at The Waverly Pres* ML Royal <fc Guilford Avenue* Baltimore, Maryland 31303 USA. j 294 BIOLOGICAL AND MEDICAL PERSPECTIVES in man. Many substances in the chemical and dye industries, which are capable of producing a hemorrhagic cystitis or methemoglobinemia, do not cause bladder cancer. The occupational diseases, with relatively few exceptions are not characteristically associated with occupational cancer. CHARACTERISTIC SITES FOR OCCUPATIONAL CANCER Skin Canoes Skin cancer is by far the commonest type of occupational cancer; and because precancerous lesions on the skin are readily visible, they are susceptible of early detection, and effective removal. Soot (which caused the early scrotal cancers in chimney sweeps), coal tar, shale oil, pitch, creosote, asphalt, fuel oils, crude mineral oil, and carbon black are all potentially carcinogenic to the skin. In the petroleum industry, wax pressmen and other workers exposed to petroleum frac tions, with a boiling point above 700F, can develop scrotal cancer, particularly when their trousers become saturated with the oil (3). Among other agents suspected of causing skin cancer are arsenic, and ultraviolet light. Skin cancer is not uncommon among farmers with heavy exposures to the sun. Workers exposed to external radiation, including X-ray and fluoroscopic equipment, can develop skin cancer unless adequately protected by proper shielding and other control measures discussed elsewhere (see Chapters 7 and 17, under Industry and Laboratories). Skin cancers are usually squamous cell carcinomas, which develop slowly and cannot be differentiated, pathologically, from similar skin cancers, of non-occupational origin. A careful history of significant exposure is indispensable, therefore, for a differential diagnosis. Lung Canceb The incidence of lung cancer is sufficiently great, in the general population, to be a matter of major concern, particularly because it has been steadily increasing in the last two or three decades. This increase has occurred during a period of tremendous technological de velopment; when workera were being exposed to an increasing variety of chemical and physical agents, some of which are present, as irritant and toxic air contaminants, in the form of dusts, gases, fumes, mists, etc.; when ^immunity air pollution has gradually increased; and when smoking has become a universal habit. It is natural enough to speculate that these factors have been important in the increasing incidence of lung cancer. On the other hand, it is difficult to determine the re spective contributions of each of these factors (4). Among the chemical carcinogens known to be capable of causing lung cancer, are certain of the nvES id dye industries, which s or methemoglobinemia, diseases, with relatively dated with occupational TIONAL CANCER occupational cancer; and readily visible, they are removal. Soot (which sweeps), coal tar, shale mineral oil, and carbon skin. In the petroleum posed to petroleum frac. develop scrotal cancer, (rated with the oil (S). cancer are arsenic, and on among farmers with :d to external radiation, can develop skin cancer Iding and other control f 17, under Industry rci^omas, which develop ically, from similar skin ul history of significant rntial diagnosis. [y great, in the general m, particularly because o or three decades. This lendous technological deto an increasing variety h are present, as irritant usts, gases, fumes, mists, ally increased; and when tural enough to speculate e increasing incidence of lit to determine the re. U). Among the chemical 5 cancer, are certain of the OCCUPATIONAL CANCER 295 chromates, nickel carbonyl, asbestos and arsenic. Whenever one is dealing with carcinogenic air contaminants, one must bear in mind that the eyes, nose and upper respiratory passages may also be involved under certain circumstances. Occupational lung cancers are characteristically broncho genic carcinomas, of the squamous cell type. Metaplasia of the bronchial epithelium appears to precede the appearance of the tumor. These tumors develop slowly, and may not be diagnosed for many years after cessation of exposure to the etiological carcinogenic agent. Chromates Both American and European experience has confirmed the etiological role of certain of the chromates in the production of lung cancer. As a result of the independent studies of Machle and Gregorius (5) and Baetjer (6), the chemical compounds believed to be responsible are the hexavalent chromium compounds, Na and K monochromate or I dichromate, and zinc chromate, inhaled as dust. Most of these cases ! were found to be bronchogenic carcinoma. An exposure of 4 years ap: peared to have been sufficient in some cases. In most cases, however, there were a great many more years of exposure. A characteristic latent period, of varying duration, between cessation of exposure and the development of the lung cancer has been observed. Asbestos Bronchogenic carcinoma, originally thought to be associated solely with the disease, asbestosis, has now come to be accepted as due to j the inhalation of asbestos dust, even in the absence of asbestosis. The j tumor is usually found in one of the lower lobes, where asbestos fibers are most numerous (7). In other types of bronchogenic carcinoma, the upper lobes appear to be more characteristically involved (5). Tumors have also been found to develop elsewhere in the body, particularly in the pleura and peritoneum. These pleural and peritoneal tumors'are mesotheliomata, a very rare type of cancer at the present time. The fact that they develop at sites remote from the initial sites of deposi tion of the asbestos fibers in the lung3, has raised interesting questions of transport and migration. All of these tumors, found.. in., persons exposed to asbestos dust, usually develop after very long latent periods, but they may apparently also develop following a relatively limited exposure. Some are not diagnosed until many years had elapsed since the last exposure. The precise type of asbestos fiber appears to be of some importance as an etiological factor (see Chapter 4). Reviewing the changing medical picture over the years, resulting from exposure to asbestos dust, Gilson (9) suggests that, in . the early \ r ! r j t 'i i \ j 296 BIOLOGICAL AND MEDICAL PERSPECTIVES days, exposures were high and workers died young, perhaps from com plications such as pneumonia or pulmonary tuberculosis. As living and working conditions improved, however, and tuberculosis became less prevalent in the community, workers lived long enough to develop progres sive pulmonary fibrosis, and other features of asbestosis, often ending in cor pulmonali. Under modem conditions of exposure, on the other hand, workers develop only moderate degrees of asbestosis, and live long enough to develop bronchogenic carcinoma. He suggests that, in the mesothelioma, we are witnessing the very long-range effects of low-grade exposure to asbestos dust. This is an interesting historical perspective. The pathogenesis of this disease is quite obscure at the present time, and many conjectural model constructs are under intensive investigation. Environmental exposures to asbestos dust are apparently not con fined to the . workers expoeedi Here we find so-called "neighborhood. cases," analogous to those found in relation to beryllium exposure-- the development of the disease in persons wio had never worked with these substances; and even those who live within a considerable radius of the plants. Contact with the dust on workers' clothing, when they are brought home to be laundered, is believed to be a possible ex planation in some cases, but not all. It has, been suggested that other coexisting sources of community air pollution, which go unrecognized at the present time, may play contributing roles. There are apparently great differences in individual susceptibility not only among workers exposed to asbestos dust, but among persons living in the neighboring communities.. Ionizing Radiation The lung cancers which develop in miners exposed to radioactive ores are believed to be caused primarily by the radon gas given off and its degradation daughters. This has been discussed in Chapter 14, under Mining. Bladdeb Camceb As in the case of lung cancer, bladder cancer has been on the increase throughout the world during recent decades, and this has stimulated in tensive research as to the etiological factors involved. In industry, the carcinogenic aromatic amines include beta-naphthylamine, para-amino diphenyl, auramine and magenta. Benzidine is still controversial. Alpha.naphthylamine which had long been suspected of being carcinogenic is no longer suspect. It is now believed that because it is a contaminant of betanaphthylamine, it was improperly included among the bladder carcino gens. Aniline, which had also been suspect, is not carcinogenic. There are a number of chemical agents which can produce cancer of the bladder in animals, but not in man.