Document EdzZqzwj88Ka6BQ5VRaNqYmVN

Asbestos health question perplexes experts When, asked to comment on research small that detection is extremely diffi directions before an international con cult and time consuming, placing re ference on the biological effects of in straints on the scope of research that gested asbestos in Durham, N.C., last can be reasonably undertaken. month, Dr. Paul F. Holt of Reading Perhaps 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 asbestos 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 Asbestos 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, be. It seems likely that asbestos occurs each less than 5 microns in length and naturally in much of the drinking about 0.2 micron in diameter. These fi water in the U.S. Environmental expo brils are hollow, and their large surface sure to it is increased by filtration of area and relatively high surface charge certain beverages and pharmaceuticals allow for great adsorption of trace through asbestos filters. Used exten metal ions to these particles. sively in construction for its fireproof The other asbestos minerals, collec ing qualities, asbestos contaminates tively referred to as the amphibole the air in most office buildings and minerals, have a significantly larger stores. An examination of lung sections fiber diameter and are solid fibers. of people living and working in New They have sodium, calcium, and iron York City has shown some fibers in the occurring in their lattice structures, in lungs of every person examined. Simi addition to magnesium and randomly lar results probably could be found in substituted trace metal ions. Although any other urban area in the nation. not used as extensively for industrial Clearly, there is a need to determine purposes, the amphibole minerals com whether this constant and widespread monly are found as contaminants of exposure is hazardous. To help evalu talc, chrysotile, and other widely used ate the danger associated with asbestos minerals. exposure as it is now understood and to Chrysotile fibrils are too small to be examine new directions in research to detected by conventional optical mi enable a more complete understanding croscopy. To identify these particles of the effects of asbestos ingestion and positively, Dr. Arthur M. Langer of exposure, the National Institute of En Mt. Sinai School of Medicine in New vironmental Health Sciences and the York City explains, a combination of Environmental . Protection Agency transmission electron microscopy, se sponsored last month's conference. At lected area diffraction, and micro tended by some 130 scientists and pub chemical analysis is needed. Others be lic health officials from 12 countries, lieve that scanning electron micro the conference emphasized the limited scopes could be useful in detecting amount of information available on the chrysotile in combination with some effects of low-level, prolonged expo type of chemical identification, but all sure. The scientists also pointed out agree that the main drawback to any how difficult it is to obtain accurate detection technique that requires elec information on these effects. tron microscopy. is the time involved There are three serious difficulties in for each analysis--about one man-day determining the effects of asbestos on per sample. Any investigation of the human health, the conference speakers occurrence of asbestos in the general agreed: population or in the environment must The term asbestos itself is mis consequently be very limited in scope. leading, for it encompasses a whole Amphibole asbestos fibers are larger. group of minerals that are distinct But they also require sublight micro from each other in chemical composi scopes for careful examination and tion, particle size, and probably biolog cannot be positively identified without ical effect. additional microchemical or selective Many of these particles are so area diffraction analysis. Chrysolite fibers in lung tissue The research workers at the confer ence expressed great hope that ad vances in automated analysis would make more extensive sampling possible by cutting down on the time required for analyzing each sample. Dr. Eugene P. White of Pennsylvania State Uni versity, for example, described a com puterized system for examining small particles using a scanning electron mi croscope that is currently used in his laboratory for analysis of coal mine dust. The most serious deterrent to under standing the biological effect of ingest ed and inhaled asbestos, however, is the long incubation period of certain asbestos-induced effects. Asbestos workers in the shipbuilding industry in the U.K. in the 1930's began ^o develop statistically high incidences of the pre viously rare cancer form mesothelioma in the late 1950's, more than 20 years after their asbestos exposure. Since that time, many other cases of the dis ease have been reported in patients who worked with asbestos 25 to 35 years earlier. Dr. Irving J. Selikoff, director of the Environmental Health Sciences Center at Mt. Sinai School of Medicine, pre 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 were very much more frequent among smok ing asbestos workers than among other smokers. In one study of 17,800 asbes tos insulation workers, of whom 9590 HWBUI0002734 dermal layer close to the gastrointesti nal tract, ingested asbestos is very poorly absorbed, if at all, through the lining of 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 walls 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 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 -'"`--'li- V--**^'' be used indiscriminately until conclu Asbestos cement worker wears mask to screen out chrysotile fibers 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 " s-.- >s. 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 a substantial number of these workers enter the body through the gastrointes two directions. The most reliable infor and determine, at the very least, which tinal tract, since relatively small mation on the health hazard of asbes asbestos forms are the most dangerous amounts of ingested asbestos appear to tos to man will come from one of the ones. penetrate the body. Last September research directions, studies of the ef The other direction of current asbes FDA began taking steps to eliminate fect of the mineral on man himself. tos research uses laboratory animals to the use of asbestos filters in the pro- , Thus, the studies that Dr. Selikoff and study details of the effect of the fibers duction of parenteral drugs. 0 FT'c* > his associates have begun on asbestos on tissues. The drawbacks of making EPA's Gordon Everett calls for stan workers in New York and New Jersey inferences from animal models were re dardization of reporting data so that are being continued and expanded. Dr. peatedly pointed out by speakers at the the necessarily limited amount of data . Selikoff points out that there are some conference. Especially in cancer re collected in each study can be usefully cases of mesothelioma in New Jersey search, different animal species often compared with results from other stud that cannot be traced to any asbestos respond substantially differently to the ies. He points out that information on exposure. These are being further in same agent. Consequently, many dif the biological effects of asbestos is very vestigated to see if a cause for them ferent animal models must be used and limited and that the effects of many can be found. Multiple effect correla compared if animal response is to be asbestos substitutes have not been in tions, such as that between cigarette reliably extrapolated to humans. vestigated at all. Before asbestos use is smoking and asbestos fiber inhalation, Animal studies seem to show that al banned, it should be certain that a are being looked for also. though inhaled asbestos can be found safer alternative is available, he cau Dr. Ian Webster of the National Re in the diaphragm, liver, and the epi tions. HWBUI0002735