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Can you imagine today's industry without the use of question: At what level of pulmonary asbestos content Fibers? Without any Fibers--be they organic or mineral, does disease begin? natural or man-made? Because industrial fibers are so The Occupational Safety and Health Administration ubiquitous and because industrial workers are exposed to (OSHA) has ruled that in the workplace there shall be not these fibers during manufacture and routine use, we must more than two fibers longer than 5 /im/cm3 of air. The examine whether fibers constitute any health hazard. ruling is restricted to fibers longer than 5 fim since one Let's first consider the two types of mineral fibers: cannot count shorter fibers accurately with a light natural materials such as asbestos and man-made ones microscope. such as fibrous glass, mineral wool, and ceramic Because of the health hazard associated with inhalation aluminum silicate. of asbestos dust, there has been an urgency to find mineral Mineral fibers have received great attention in recent fibers that do not endanger health. These substitutes, all years because of the serious diseases that have been man-made, include not only fibrous glass, mineral wool, associated with excessive exposures to asbestos dust. Four and ceramic aluminum silicate, but also fibers composed kinds of asbestos are in commercial use: chrysotile from of aluminum oxide, carbon, silicon carbide, titanium Canada, which constitutes more than 95% of the asbestos phosphate, and potassium titanate. used in this country; crocidolite and amosite from South Of all these man-made mineral fibers, only fibrous glass Africa, which make up the remainder of the asbestos used; and mineral or rock wool have been produced over a long and anthophyllite, which is mined in Finland but not used enough period (more than 40 years) to allow studies on in the United States. chronic effects. Information on the health of workers All asbestos, when inhaled in excessive amounts, causes exposed to its dust, bulwarked by experimental data, destruction of lung tissue and the development of scars allow us to conclude that fibrous glass dust does that result in inadequate ventilation of the lungs, not produce disease. It is a nuisance-type dust, so decreased oxygenation of the blood, pulmonary classified by the American Conference of hypertension, and right heart failure. These lung changes Governmental Industrial Hygienists (ACGIH) (4): comprise the disease asbestosis. If severe, it is a "Nuisance dusts have a long history of little adverse effect debilitating and often fatal disease. on lungs and do not produce significant organic disease or All four varieties of asbestos are also associated with toxic effect when exposures are kept under reasonable the development of lung cancer. However, epidemiologic control. The lung-tissue reaction caused by the inhalation studies have revealed that nearly all patients with of nuisance dusts has the following characteristics: 1) The asbestotic lung cancer have also been severely addicted to architecture of the air spaces remains intact. 2) Collagen cigarette smoking for most;of their lives (/). (scar tissue) is not formed to a significant extent. 3) The A third major asbestos-related disease is mesothelioma. tissue reaction is potentially reversible." This rapidly fatal, but relatively rare cancer develops in Although it appears that at the present time, no known the chest cavity or abdomen and occurs mostly among pulmonary disease can be attributed to the inhalation of people exposed to South African asbestos. Chrysotile has fiberglass (5), the classification of fiberglass dust as a a very low potential for causing mesotheliomas (2). In a nuisance-type dust has recently been challenged. This study of workers exposed only to chrysotile, only three out challenge threatens to impose crippling constraints upon of more than 2400 deaths that occurred over a span of 30 the utilization of all types of man-made mineral fibers years were caused by mesothelioma. that might serve as safe replacements for asbestos. The Laboratory investigations have shown that short challenge is based on animal experiments in which asbestos fibers (less than 5 fini in length) do not cause fiberglass as well as other mineral fibers were injected into lung disease in animals (3). Moreover, the lungs of city the abdomen of rats or implanted surgically into the chest dwellers, men and women alike, have been found to cavity of these animals (6-8). Many of the rats so treated contain asbestos fibers without demonstrable disease developed cancer in the region of the embedded mineral attributable to them. This raises the as yet unanswered fibers. It was concluded from these experiments that 436 CHEMTECH JULY 1980 HWBUI0003088 mineral fibers, regardless of their chemical composition, are capable of causing the development of cancer if their dimensions are within certain limits, namely, less than 0.5 fim in diameter and more than 10-20 fim in length. Is it proper to extrapolate from these results in rats to Paul Gross is director of pathology research at the Industrial Health Foundation. He served as distin guished research professor of patholo gy at the Medical University of South Carolina and as research professor of man? Those who answer "No" to this question support pathology of industrial diseases at the their conclusion by the somewhat facetious, but nevertheless pertinent statement that no one has advocated the injection of fiberglass or other mineral fibers into the chest cavity or the abdomen of mam But there are other reasons for opposing this extrapolation from rat to man: Rats develop similar cancers when University of Pittsburgh. Dr. Gross is a graduate of Adelbert College School of Medicine, and the Gradu ate School of Western Reserve Uni versity, He has published more than 200 articles and served on numerous advisory boards. injected with many nonfibrous materials which are known to be incapable of causing cancer in man. According to the National Cancer Institute's Ad Hoc Committee on the Evaluation of Low Levels of Environmental Chemical Carcinogens, a substance, although carcinogenic to animals, should not be considered a potential cancer Daniel C. Braun is president of the In dustrial Health Foundation, Inc. and was a lecturer on industrial hygiene at the University of Pittsburgh School of Medicine. He is also a lecturer on occupational health at the. University hazard to man if the carcinogenic effect clearly results of Pittsburgh Graduate School of from physical, father than chemical induction or where the route of administration is grossly inappropriate in terms of conceivable human exposure (9). It is therefore apparent that the challenge to the present classification of man-made mineral fibers as nuisance- Public Health. Dr. Braun graduated as a chemical engineer from the Car negie Institute of Technology night school and from the University of Pittsburgh School of Medicine. He has served as medical director of the type dusts rests upon inappropriate extrapolation of the Pittsburgh Coal Company and U.S. results of rat carcinogenesis experiments to man. It is also Steel and he has published extensively on industrial hygiene and apparent that until OSHA makes an official ruling with occupational medicine. respect to this challenge, there will remain much carbon disulfide and sulfuretted hydrogen. The first is a indecision, not only in the production, fabrication, and use chemical essential to the process; the second is a by of man-made mineral fibers, but also in the research and product, troublesome and of ho use. Carbon disulfide is a development of promising new substitutes for asbestos. dangerous toxin, capable of causing changes in the Let's turn now to organic fibers, both natural and gastrointestinal, cardiovascular, endocrine, and central synthetic. Natural organic fibers include those of nervous systems. Sulfuretted hydrogen causes severe * vegetable origin, such as cotton, jute, and hemp, and those conjunctivitis and disturbances of vision including color derived from animals, such as wool, cashmere, and hair. blindness. These ill effects are almost completely confined Synthetic fibers may be cellulosic, e.g., rayon, cellulose acetate and triacetate, or noncellulosic, e.g., acrylic, to the manufacture or processing of the organic fibers and do not occur in their use or application. polyester, and nylon. The great majority of the noncellulosic, synthetic fibers The literature indicates that few respiratory difficulties are inert and innocuous. When fibers in this class cause are associated with synthetic fibers, although they may problems, it is likely to be due to some unreacted present special problems as discussed later. Natural fibers, on the other hand, and their vegetable or animal dusts can ingredient used in the synthesis of the resin or fiber. We thus note that some dangers pxist due to the pose a threat to the respiratory system. The diseases attributable to exposure to these fibers and dusts often presence of fibers and their precursors. It is essential that workers in industry be protected from known harmful result from an immunological reaction to antigens exposures. Yet it is equally important that we don't consisting of bacteria, fungi, molds, and plant enzymes or prevent the use of harmless material through the to protein toxins in the fibers themselves. Examples include byssinosis from raw cotton, hemp, and flax and inaccurate extrapolation of animal data. bagassosis from sugar cane trash. The symptom-complex References varies from one substance to another. Byssinosis is (1) Sclikoff, I. J.; Hammond, B. C.; Churg, J. "Asbestos Exposure, Smoking characterized by shortness of breath on the first workday and Neoplasia," J. Am. Med. Assoc. 1968,204, 106. of the week and a decrease in ventilatory function. Byssinosis, also called "brown lung disease," unlike "black lung disease," is not distinguished by abnormal pigmentation of the lung tissue. It is a disease characterized by disturbed lung function without recognizable microscopic changes in the lung tissue. (2) McDonald, J. C,, et al. "Mortality iii the Chrysotile Asbestos Minesand Mills of Quebec," Arch. Environ. Health 1971,22, 677. (3) Gross, P. "Is Short-Fibered Asbestos Dust a Biological Hazard?", Arch. Environ. Health 1974,29, 11S. (4) "TLVs Threshold Limit Values for Chemical Substances in Workroom Air," Adopted by ACG1H for 1977, American Conference of Governmental Industrial Hygienists. (5) Morgan, W. K. C.; Seaton, A. "Occupational Lung Diseases," W. B. Byssinosis is caused by the bract associated with the raw cotton and not by the cotton fibers themselves. Saunders Co.: Philadelphia, 1975. p. 116. (6) Stanton, M. F.; Wrench, C. "Mechanism of Mesothelioma Induction with Asbestos and Fibrous Glass," J. Natl. Cancer Inst. 1972,48, 797. Other organic fibers may cause asthma or an acute pneumonitis. Problems associated with synthetic cellulosic fibers and resins stem from chemicals used in the production process and from unreacted precursors or contaminants coating the fibers. For example, in the viscose process of artificial silk or rayon production, two toxic substances are present, (7) Pott, F.; Friedrichs, K. H. "Tumors in Rats after Intraperitoneal Injection of Fibrous Dust (German),'' Natumissenschaften 1972,59, 318. (8) Wagner, J. C., et al. "Mesothelioma in Rats after Inoculation with Asbestos and Other Materials," Brit. J. Cancer 1973,28, 173. (9) National Cancer Institute, Ad Hoc Committee on the Evaluation of Low Levels of Environmental Chemical Carcinogens: Report to the Surgeon General, USPHS, April 22,1970. Authors' address: Industrial Health Foundation, Inc., 5231, Centre Ave., Pittsburgh, Pa. 15232. CH&MTECH JULY 1980 437