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Asbestos health question perplexes experts When asked t> comment on research small that detection is extremely diffi directions before an international con cult and time consuming, placing re ference n the biological effects of in straints on the scope of research that gested asbestos in Durham. N.C., last can lie reasonably undertaken. month. Dr. Paul F. Holt of Reading I'erha|>s the most serious diffi University. England, summed up the culty in asbestos research, however, is feeling of the whole conference in his the very long period between initial ex response. The main question to be in posure and evidence of biological ef vestigated. he said, is: Does ashestos fects. In the case of mesothelioma, an matter, or doesn't it? asbestos-induced cancer of the linings Coming after more than 40 years of of the abdomen and chest, this time published research on the biological ef period is usually 25 to 35 years. fects of asbestos--research that has Ashestos is any of several silicate been greatly intensified over the past minerals existing in fibrous form. The 10 years in the U.S. and abroad--this Federal Register lists six main types of seems a very preliminary question to asbestos mineral, each with its own still be under investigation. Neverthe chemical composition. To add further less, although asbestos is known to confusion, each of these chemical cause severe lung damage and to raise forms exists in both a fibrous or "as- the likelihood 'of certain cancers devel bestiform" variety and in a nonfibrous oping following heavy exposures, the type that is sometimes considered an effect of smaller doses on the general asbestos mineral and sometimes not. population isn't at all clear. Chrysotile asbestos is the most dis It seems very farfetched that asbes tinct asbestos form and the one most tos could be dangerous. Dr. Holt says, widely used in industry. A magnesium but if it is, then everyone is in very se silicate hydroxide, chrysotile exists in rious trouble. And indeed they would nature as a bundle of very small fibrils, The research workers at the confer be. It seems likely that ashestos occurs each less than 5 microns in length and ence expressed great hope that ad naturally in much of the drinking vances in automated analysis would water in the li.ii. Environmental expo brils are hollow, and their large surface make more extensive sampling possible sure to it is increased by filtration of area and relatively high surface charge by cutting down on the time required certain beverages and pharmaceuticals allow for great adsorption of trace for analyzing each sample. Dr. Eugene through asbestos filters. Used exten metal ions to these particles. P. White of Pennsylvania State Uni sively in construction for its fireproof ing Qualities, asbestos contaminates the air in most office buildings and stores. An examination of lung sections The other asbestos minerals, collec tively referred to as the amphibole minerals, have a significantly larger fiber diameter and are solid fibers. versity, for example, described a com puterized system for examining small particles using a scanning electron mi croscope that is currently used in his of people living and working in New They have sodium, calcium, and iron laboratory for analysis of coal mine York City has shown some fibers in the occurring in their lattice structures, in dust. lungs of every person examined. Simi addition to magnesium and randomly The most serious deterrent to under lar results probably could be found in substituted trace metal ions. Although standing the biological effect of ingest any other urban area in the nation. not used as extensively for industrial ed and inhaled asbestos, however, is Clearly, there is a need to determine purposes, the amphibole minerals com the long incubation period of certain whether this constant and widespread monly are found as contaminants of asbestos-induced effects. Asbestos . exposure is hazardous. To help evalu talc, chrysotile, and other widely used ' workers in the shipbuilding industry in ate the danger associated with asbestos minerals. the U.K. in the 1930's began to develop exposure as it is now understood and to Chrysotile fibrils are too small to be statistically high incidences of the pre examine new directions in research to detected by conventional optical mi viously rare cancer form mesothelioma enable a more complete understanding croscopy. To identify these particles in the late I95Q's, more than 20 years of the effects of asbestos ingestion and positively. Dr. Arthur M. Langer of after their asbestos exposure. Since exposure, the National Institute of En Mt. Sinai School of Medicine in New that time, many other cases of the dis vironmental Health Sciences and the York City explains, a combination of ease have been reported in patients Environmental Protection Agency transmission electron microscopy, se who worked with asbestos 25 to 35 sponsored last month's conference. At lected area diffraction, and micro years earlier. tended by some 130 scientists and pub chemical analysis is needed. Others be Dr. Irving J. Selikoff, director-of the lic health officials from 12 countries, lieve that scanning electron micro Environmental Health Sciences Genter the conference emphasized the limited scopes could be useful in detecting at Mt. Sinai School of Medicine.^pre- amount of information available on the effects of low-level, prolonged expo sure. The scientists also pointed out how difficult it is to obtain accurate information on these effects. There are three serious difficulties in determining the effects of asbestos on human health, the conference speakers agreed: The term asbestos itself is mis leading. for it encompasses a whole group of minerals that are distinct from each other in chemical composi tion, particle size, and probably biolog ical effect. . ' Many of these particles are so chrysotile in combination with some type of chemical identification, but all agree that the main drawback to any detection technique that requires elec tron microscopy is the time involved for each analysis--about one man-day per sample. Any investigation of the occurrence of asbestos in the general population or in the environment m.ust consequently be very limited in scope. Amphibole asbestos fibers are larger. But they also require sublight micro scopes for careful examination and cannot be positively identified without additional microchemical or selective area diffrflrtinn onaltraie sented data to the conference from sev eral mortality studies of occupationally exposed asbestos workers in New York and New Jersey. His studies show in creases in interthoracic cancer and mesothelioma more than 20 years after heavy asbestos' exposure. In addition, he found that although lung cancer deaths did not appear to be more frequent among nonsmoking, asbestos workers than among the gen-. eral nonsmoking population, they werevery much more frequent among smok- CQ ing asbestos workers than among other G o smokers. In one study of 1.7,800 asbes-- > dermal layer close to the gastrointesti nal tract, ingested asbestos Js. very poorly abjwrbedr`r~at all, throurh th* lining ot the stomach and colon. Dr! John M. G. Davis of the institute of Occupational Medicine, Edinburgh, Scotland, could detect no asbestos passing through the stomach or intesti nal wails of rabbits fed asbestos fibers in his laboratory. However, Dr. R. D. Pontefract of the Canadian Food Re search Laboratories injected an asbes tos sample directly into the stomachs' of laboratory animals and was able to detect about 0.1% of his sample in the epiderm. In studies with baboons. Dr. Webster found that very little ingested asbestos penetrates the walls of the stomach and colon and that almost all that does is of the smaller chrysotile type. Studies with inhaled asbestos also show that the fiber that is ab sorbed is predominantly the chrysotile type. Conclusive evidence on the effect of environmental levels of asbestos on man, or even reliable estimates of what that level is, will not be available for some time. In the meantime, current n asbestos exposure may be causing can- . cers that will not be detectable until the next century. Thus, representatives of regulatory agencies present at the conference agree with asbestos research workers that asbestos presents too much of a threat to human health to Asbestos cement worker wears mask to screen out chrysolite fibers be used indiscriminately until conclu sive evidence is available. There is not . yet complete agreement, however, on were smokers, there were five to six search Institute for Occupational Dis what sort of regulation should be im times the predicted number of deaths eases in Johannesburg, .Republic of plemented. from lung cancer among the smokers. South Africa, told the conference of a Dr. William Eisenberg of the Food A smaller study of insulation workers massive effort by the South African and Drug Administration explains that in New York showed 10 times the ex government to establish the danger of it is not possible for FDA to run elec pected number of deaths caused by asbestos exposure. South Africa mines tron microscopy analyses of all the po lung cancer among the workers who both amphibole and chrysotile types of tential sources of asbestos contamina smoked cigarettes. asbestos. The government hopes to' tion under its jurisdiction. At present, The question of most concern to conduct mortality studies on all of the analysis by polarized light microscopy public health officials, and the area of workers in these mines since 1953. is used to determine purity of foods most intensive research at present, is Most of the workers come from no and drugs, even though this method the effect of asbestos exposure at inter madic groups living in the desert re probably misses many of the smaller mediate levels and the effect of low- gions of South Africa. They work in the and more easily absorbed asbestos fi level exposure to asbestos in combina mines for brief periods then return to bers that may be present in these ma- . tion with low levels of other carcino their homes, making them very diffi terials. FDA's main concern, according gens that are often present in the cult to keep track of. Nevertheless, the to.Dr. Eisenberg, is with parenteral environment. government hopes to be able to follow drugs rather than with substances that Research on these questions takes two directions. The most reliable infor mation on the health hazard of asbes tos to man will come from one of the research directions, studies of the ef fect of the mineral on man himself. Thus, the studies that Dr. Selikoff and his associates have begun on asbestos workers in New York and New Jersey are being continued and expanded. Dr. Selikoff points out that there are some cases of mesothelioma in New Jersey that cannot be traced to any asbestos exposure. These are being further in vestigated to see if a cause for them can be found. Multiple effect correla tions, such as that between cigarette smoking and asbestos fiber inhalation, are being looked for also. Dr. Ian Webster of the National Re a substantial number of these workers and determine,- at the very least, which asbestos forms are the most dangerous ones. The other direction of current asbes tos research uses laboratory animals to study details of the effect of the fibers on tissues. The drawbacks of making inferences from animal models were re peatedly pointed out by speakers at the conference. Especially in cancer re search, different animal species often respond substantially differently to the same agent. Consequently, many dif ferent animal models must be used and compared if animal response is to be reliably extrapolated to humans. Animal studies seem to show that al though inhaled asbestos can-lie found in the diaphragm, liver,: and the`epi enter the body through the gastrointes tinal tract, since relatively small amounts of ingested asbestos appear-to penetrate the body. Last September FDA began taking steps to eliminate - the use of asbestos filters in the pro duction of parenteral drugs. EPA's Gordon Everett calls for stan dardization of reporting data so that the necessarily limited amount of data collected in each study can be usefully compared with results from other stud ies. He points out that information on the biological effects of asbestos is very limited and that the effects of many asbestos substitutes have not been in vestigated at all. Before asbestos use is banned, it should be certain that a safer alternative is available, he cau tions. -