Document MJD6vK0NQwLgjEnDYL6wGG33j

WRGoni4gg Scientific Communications u A. Brown18 copy---- ; ----------- 1 a, . . rLMiPtiirr o If EXHIBIT |I WRG-672 1 Asbestos Air Pollution Irving J. Sclihoff, MD; William J. Nicholson, PhD; and Arthur M. Longer, PhD, New York Findings ol mesothelioma among individuals living in the vicinity ol asbestos plants suggested that asbestos air pollution might occur. Measure ment ol asbestos (chrysotile) content ol ambient air In New York City and other locations showed levels ol 10 to 50 X 10** gm/cu m, and lungs ol New York residents examined at autopsy regu larly showed chrysotile librils. Occurrence ol asbestos air pollution Is now established. What have not yet been defined, however, are the dimensions of disease hazard which may be associated. Epidemiological considerations sug gest that it is Improper to equate the several kinds of asbestos exposure: direct occupational, Indirect occupational, exposure in family cir cumstances, neighborhood contamination, and general community asbestos air pollution. Since most urban air pollution Is derived from com mercial and industrial sources, the asbestos in dustry has both Important responsibility and opportunity lor Its control. Early in the 1960s, the problem of as bestos disease was disseminated from the occupational area into the general environ ment Three germinal observations were re sponsible for this. First Kiviluoto reported finding 499 cases of parietal pleural calcification among 6,312 residents of a rural county in Finland.1 This came very much as a surprise, since the type of calcification observed Itad previously been Submitted for publication Feb 9, 1971; accepted Feb 17, 1972. From Mount Sinni School of Medicine of the City University of New York, New York. ' Head before the American Medical Axvicintion Research Conference on Ait Pollution, New Orleans, Oct 0. 1970. Reprint rcqueul* to Director. Fnvironmrnlal Sci ences laboratory. Mount Sinni School of Medicine, Fifth Aveimr and 100th Street, New York lOO-'O (Dr. SeliUolf). described primarily in asbestos workers,5 usually more than 20 or 30 years after start ing work3; yet the cases were not among asbestos workers, but among fanners and farmers' wives. The asbestos link, however, was there; the county did have an asbestos mine. The natural supposition was that as bestos air pollution from the mine was re sponsible, a presumption that was strength ened when the specific type of asbestos pro duced by the mine (anthophyllite) was found in the air up to 50 km away,4 and asbestos bodies were demonstrated in the lungs of cattle grazing in the nearby fields.1 The same year (1960) saw a second wor risome communication. Wagner ct als re ported 47 cases of pleural mesothelioma in a part of South Africa which was important for asbestos mining. They noted potential asbestos contact for most of the patients two or more decades before, in many instances merely the result of living in the general area or of chance contact in a family setting. While pleural mesothelioma had previously been attributed to asbestos exposure,* the strength of this association had not been appreciated. More pertinent was the demon stration that it could result from other than occupational exposure. Amplification soon followed. Newhouso and Thompson1 studied all mesotheliomas at the London Hospital. They confirmed the close association with asbestos, 31 of the 76 subjects having had occupational exposure. They also confirmed the imjxirtance of nonoccupational contact; of the 45 who had not worked with the material, nine had lived in the households of asbestos workers and 11 liad lived, decades before, within one-half mile of an aslieslos plant. Arch Kticirnn Jlraltli--Vol 25, July 1072 1! 2 ASBESTOS All! POLLUTION--SELIKOFF ET AL Licbcn nnd Pistnwka rcjwrtcd similar find nnd we would not expect their risk to ings in Pennsylvania.11 duplicated in the general imputation. B. : , i Wlinl appeared to be a strong link in the part of their risk disseminated, with chain of evidence for environmental asbestos dusts from their work? What sort of dos*-r. disease was the report in 1963 by Thomson sponsc curve arc we dealing with? Is the:* , etui* that asbestos bodies were commonly to threshold which, once crossed, leads to -~r. r be found in tho lungs of the general popula ous hazard of neoplasia? An hypothi. c tion of Capetown, South Africa. They ex could be formulated that such a thresh; ; pressed a drop of lung tissue fluid onto a calls for very little asbestos (since rrr.: slide, examined it by optical microscopy, amounts may still reflect billions of fiber.- r and in one quarter of 500 consecutive autop fibrils, or both), and that asbestos works-, sies, found structures apparently identical pass it early in their careers. with those seen in asbestos workers' lungs. Such an hypothesis, or some variation c- But these were not asbestos workers; they it, ^ is not inconsistent with observation- had been ordinary citizens of this large city. made in the last several years. Neoplasm- Thomson and associates concluded that the such os pleural and peritoneal mesothsh- subjects had inhaled asbestos in the course oma, occur in excess even among asbestos of their urban living, from the many asbes workers with little or no radiological evi A tos products about them. With knowledge of dence of asbestosis, suggesting that en ii what exposure to these fibers could do under sures insufficient to cause asbestosis rr_i; industrial circumstances as a background, still produce neoplasia. The spread of thi? and with the observations of Wagner et al5 separation is not established, but it is appar as an example, they suggested that we were ent recently that while lower dust levels L* now faced with a "modem urban hazard" industry may prevent much asbestosis, such and predicted that asbestos-associated neo levels will not necessarily prevent cancer." plasms would rival cigarette-induced lung It is not now known how low a threshold cancer in the future. must be to prevent asbestos-associated neo It should be noted that the prediction of plasms. Thomson and associates9 is an extrapola tion. It is a wide step from occupational Asbestos in Lungs exposure, with large numbers of asbestos bodies, to community contamination, with, - as a rule, far fewer bodies, particularly with It thus became important to know whether little knowledge of a dose-disease response asbestos truly was a common contaminar: relationship. Also, the particles described of urban dwellers' lungs. The demonstratior. had the appearance of those seen in asbestos that "asbestos bodies" were to be regularly workers, but some uncertainty existed that found at autopsy in many cities of ths these necessarily had an asbestos core,10 es world14 confirmed the finding of Thomson t; pecially since it had been known for 30 al,* but did not settle the question. It was years that such bodies could be found after not known whether the cores were necessari exposure to other fibers as well.11 ly asbestos, an uncertainty resulting frerr Despite these caveats, the three reports, technical difficulties involved in analyzir.r taken together, posed a problem that is now such cores.17 MS. Mm coin very real. Occupational asbestos exposure In recent months, the impasse has beemay be associated with serious risk; for resolved by direct search for asbestos fiber- you example, among nsbestos insulation workers and fibrils.1* Investigation of 3,COO consecu oxyj in the New York metropolitan area at this tive autopsies in New York had shown thu: Y time, approximately one in five deaths is "asbestos bodies" were common; optical mi lank due to lung cancer, one in ten is due to croscopic examination of 17o, X 1 sq cm c: atrw with A mesothelioma, one in ten to gastrointestinal lung tissue in each of these cases, showed cancer, and one in ten to asbestosis and cor asbestos bodies in 1,449 (48.3%) (Table 1 . built pulmonale.1711 These men have been ex It is likely that, had a greater volume c; thro posed to amounts of asbestos surely greater tissue been submitted for study, asbestos oxyj than those in the surrounding community, bodies would have been found in all the and pcrc (Lli Arch Environ Health--Val 25, July 1972 ASBESTOS MR POLI.UTION-SF.I.IKOFF KT AL 3 Table 1.--Asbestos Bodies in 3,000 Consecutive Autopsies In New York City, 1966 to 1968* Mala F*m*l* Talal At* No. <i 1-19 2/73 0/7 20-39 34/102 40 59 316/606 60-79 eo+ 555/997 106/18C Total 1.013/1.971 * From Linger it al. % 2.8 0.0 33.3 52.1 55.7 57.7 51.4 No. 2/53 4/25 19/58 108/247 220/491 83/155 436/1.029 % 3.8 16.0 32.8 43.7 44.8 53.5 42.4 No. 4/126 4/32 53/160 424/853 775/1.488 189/341 1.449/3.000 % 3.2 12.5 33.1 49.7 52.1 55.4 48.3 Table 2.--Numbers of Asbestos Bodies* Asbestos Bodies 0 1-4 5-14 15+ Ago <i 122 2 2 0 1-19 28 4 00 20-39 107 53 00 40-59 429 359 45 20 60-79 713 630 105 40 80+ 152 156 40 3 Total 1,551 1.204 192 63 Sax Male Female 958 (48.6%) 593 (57.6%) 802 (40.7%) 392 (38.1%) 152 (7.7%) 40 (3-9%) 59 (3.0%) 4 (0.4%) Total 1.551 1,194 192 63 From Linger et !. Total 126 32 160 853 1.488 341 3,000 1.971 (100.0%) 1.029 (100.0%) 3.000 cases, except perhaps the infants and very allowed qualitative analysis,17 with ap young children. preciation that the unique structure of The same examination showed that, in chrysotile allows its specific identification by addition to coated particles ("asbestos high magnification electron microscopy. bodies"), uncoated inorganic fibers were Chrysotile fibers or fibrils, or both, were also readily seen (Table 2). Fibers thicker found in every specimen (Fig 1). In four of than 1.0/i were almost universally to be the 28, background contamination could found; most of these arc as yet still uniden conceivably have been responsible for the tified, although some were diatom frag findings. In 24 of the 28, the number found ments, glass fibers, or phytoliths. We were was greater than background counts could' more concerned, however, with thinner fi explain (Table 4). The morphological ap bers, less than 1.0/i in diameter, since these pearance and other characteristics of these would be more consistent with chrysotile, fibers and fibrils are recorded elsewhere.1* * the asbestos variety making up 95% of the It is evident that chrysotile asbestos is a asbestos used in the United States. Such common contaminant of the lungs of New thin fibers were also commonly present, be York City residents at this lime. Similar ing found in 1,038 of the 3,000 cases, and electron microscopic observations have been tending to vary proportionately with the recorded in London,70 where not only was number of asbestos bodies (Table 3). chrysotile asbestos found in almost 80% of Hie critical information was obtained by cases, but it was noted to be the most com examining, in 28 of the 3,000 cases, a very mon and most abundant of all fibers detected. small portion of lung (conservatively esti The question inherent in the observations mated at 10~c) by a technique which of Thomson and associates* in 19G3, "is Arch Environ Health--Vol 25, July 1072 x !I i r C MS/ Mo< com you o*)I Y lank atm< with A built thro oxy{ and pcrc (Llil a vis 4 ASBESTOS Mil POLLUTION--SELIKOFF ET AL Tabic 3.---Correlation o( Inorganic Fibers with Asbestos Bodies in Lungs of 3,000 Consecutive Autopsies in New York City, 1966 to 1968* Percentage of cases showing asbestos bodies in relation to occurrence of thin inorganic fibers Thin Inorganic fibers Asbestos Bod lot 0 O No. 1,168 % 59.5 1-4 No. X 332 38.3 5-14 No. % 35 28.0 1-4 70S 35.9 424 49.0 52 41.6 5*14 70 3.8 89 10.3 21 IG.8 15+ 13 0.00 20 2.3 17 13.6 Total 1.902 65.4 865 28.8 125 4.1 Percentage ol cases snowing thin inorganic fibers In relation to occurrence ol asbestos bodies Asbaslos Bodies 15 + No. X 16 33.3 13 27.1 6 12.5 13 27.1 48 1.6 Thin Inorganic fibers 0 1*4 5-14 15+ Total O No. 1.168 332 35 16 1.551 X 75.3 21.4 2.3 1.0 51.7 1-4 z p * 705 424 52 13 1.194 59.0 35.5 4.3 1.1 39.8 5-14 No. X 76 39.6 89 46.3 21 10.9 6 3.1 192 6.4 15 + No. X 13 20.6 20 31.7 17 27.0 13 20.G 63 2.1 Correlation was done by optical microscopic study. Irom ganger el al." Table 4.--Chrysotile in 28 Cases Studied by Electron Microscopy Group i 2 3 4 5 "Blank grids" No. of Chrysotilo Flbors 4- Fibrils S9 10-50 51-99 100-200 201 S9 Case* 4/28 11/28 6/28 4/28 3/28 ooe Mil. 3 5 1 4 3 ... Foma Is 1 6 5 0 0 ... chrysotile asbestos commonly found in the lungs of urban dwellers at this time?" has now been answered, "Yes, unequivocally." Relation of Asbestos Lung Burden to Environmental Asbestos Disease There are few data at this time that would allow judgement of the significance of the asbestos we have found in lung tissue of urban residents. Whether or not the amounts present as (he result of other than occupational exposure arc : ssocialcd with frequent risk of disease is not known. In part, this is a reflection of the scarcity of data concerning the 'asbestos content of lungs in general, including those of asbestos workers. Such data as arc available suggest that the amount in lungs of the latter is quite small, ranging from 0.6% to 0.001% of lung weight.*11* It would be expected to be even lower in those not occupationally ex-, posed. No information is at hand concerning the asbestos, content of the lungs among the cases of Wagner et al,5 or Newhouse and Thompson,* or those of other cases with environmental disease.53-*4 Nor is there quantitative information concerning the as bestos content of the lung in individuals ir. the general population without stigmata o: asbestos. This is rather urgently needed, with age, sex, residence, and occupational exposure taken into account. Studies now in progress in our laboratory and elsewhere (P. D. Pooley, ThD, oral communication [July 1970]) indicate that suitable quantitative techniques for estimat ing asbestos lung content will be feasible nnd that fairly accurate estimates, npproxi- Arch Environ Ilcallh--Vo/ 25, July 1972 X 1 Y*~ Fig 1 .--Association of chrysolite fibrils and incompletely digested lung tissue. Arrows Indicate "hidden" fibrils in partially digested tissue. Arch Environ Health--Vol 25. July 1072 X lI 6 ASBESTOS Mil I'OLLUTlON--SF.UKOt'F ET At. mating nn order of magnitude, arc to be anticipated in the future. Asbestos Air Pollution It is probably nn entirely justified concept that the asbestos found in urban dwellers' lungs is derived from the initiation of air contaminated with these fibers. Very little is known, however, of the conditions of such contamination, and facile assumptions should be avoided nt this time. An example of where an "obvious" expla nation might also be inaccurate may be found in the assumptions adopted to explain Kiviluoto's1 observations. It seemed natural to expect that the demonstrable anlhophyllite asbestos air pollution from the mine and mill was etiologically related to the equally demonstrable asbestotic pleural calcification in the population living about that point source. It turns out, however, that this may not be the entire explanation, and that inti mate contact with local asbestos-bearing rocks, including those used in building houses, saunas, barns, and the like, might also play a role.23 Indeed, the latter association better ex plains almost identical epidemiological find ings in Bulgaria, where, again, pleural calci fication was found in a rural population. In this district, too, an asbestos mine was being worked, but it was an underground mine and had opened only in 1943, too recently for its discharges to be expected confidently to have had the cfleet noted3* (the lapsed period between initial exposure and evi dence of pleural calcification is 20, 30,40, or more years). As in Finland, the local field rocks have a high asbestos content and arc used for various structures by the farming population, which then may have intimate contact with what is shed from them. More important, .perhaps, the soils tilled by these farmers can be demonstrated to have asbes tos fiber (anthophyllitc) content. The im portance of this observation was empha sized by the discovery that those farmers working plots without asbestos soil contami nation had little pleural calcification, where as farmers working soil with anthophyllite readily showed the radiological changes.It may bo that similar explanations will la conic available for the finding of endemic pleural calcification in some rural areas of Czechoslovakia.-'7* At first, it seems somewhat surprising that so few data nrc available concerning the asbestos content of ambient air, especially since so much is known regarding the asbes tos content of' air within the work place. Perhaps the l>cst explanation is that once the factory gales are passed, a whole new set of technical problems is encountered, and sampling procedures, analytical approaches, and measuring methods useful for industrial controls nrc no longer applicable. Fiber Identification.--Under the indus trial circumstances, there is usually no prob lem to knowing exactly what is being mea sured, since the materials being used are cither well characterized or can be readily analyzed. Thus, whatever fibers arc seen can be confidently labelled ns "chrysotile," "cro- cidolitc," "amosite," "fibrous glass," and other types. ^ If these same fibers were to be seen in a random sample, especially if they arc small, our confidence disappears. All that can be said is that inorganic fibers are present. Even then, if these fibers were found in very large numbers, identification could be readi ly accomplished by such mass tccliniques as x-ray diflraclion. When they occur singly or randomly scattered in small numbers, these techniques are no longer applicable; and readily available alternate approaches, such as polarized light microscopy, hardly liave the same definitive assurance. While it is true that analytical attack on single fibers is still possible, these approaches (including electron microprobc analyses, electron dif fraction, and electron microscopy) are time- consuming and often restricted by the size of the particle available for analyses. Particles and Fibers.--There has long been an anomaly in particle counting for asbestos threshold levels. In the United States, a threshold level was proposed in 1938 for occupational ex|X)sure to asliestos, based upon experiences necessarily limited to that point.30 The recommendation reflect ed the instrumental restrictions of the times and were based upon counting of "particles" by optical microscopy. U was recognized that such particles could either be fibrous or nonfibrous and that the proportion could vary widely according to the materials used. A(ch Etwirtm ItfnUh--Vol 25, July 1072 Arrh Environ lli'ttllli--Vol 25. July 1972 8 ASBESTOS AIR POLLUTION--SELIIiOFF ET AL Fig 3.--Adsorption of chrysotlle fibrils onto surface of diatom. Fibrils would not be seen by optical microscopy. process studied, or oilier factors. Since the presumption is that only the fibers are re* sponsible for the biological effect, such ana lytical dilution is hardly acceptable at this time, and current approaches to industrial threshold limit values arc based entirely on fiber count. Out even here, the matter is not eo easily disposed of, since the admixture of particles and fibers often includes surface interactions among them. Figures 2 and 3 show particles of clay and a diatom collect ed near a construction site by one of us (A.M.L.). Oy light microscopy these would be categorized as "particles.*' Yet, by elec tron microscopy, it was found Hint numer ous fibers (fibrils) were attached to the sur face of the particles (opposite surface charges). In such circumstances, any biolog ical eflcct of the fillers could be incorrectly attributed to particles. The question of size and magnification is critical. Fiber-Fibril.--Mich asliestos fiber variety is quite difTcrcnt chemically, physically, structurally, and morphologically.** Chryso lite seems unique in its tendency to physical instability under a number of circumstances. The chrysotile "fiber" is not a unit whole but is, rather, composed of a large number of individual fibrils, each from 300 to 400 Angstroms. Under industrial circumstances, it is recognized that when a population of fibers is counted, "invisible" fibrils arc also present,31 but that the optically visible fibers reflect, in varying proportions under differ ent circumstances, the total chrysotile popu lation, even though there is only one filler for a very large number of fibrils. Also, with proximity to the industrial source, many fibers arc still present, not having been sub jected to influences which could result in their separation into fibrils. In the ambient air, however, very little is known about the proportion of fibers to fibrils. The matter is of some importance. Arch Em'iron Health--Vo! ?.i. July 1072 ASDF.STOS AIR POLLUTION--SELIKOFF ET AL 9 > < observed chrysotile fibrils with lengths less than 1,000 A in many instances; when these aro enmeshed in sampling debris, not only is high magnification electron microscopy nec essary, but visual scanning may be inade quate, and inferior to photographic re cording.17 It may be worth noting that such small particles arc at present subject to identifica tion by their morphological characteristics only; structural and microchcmical analysis by electron microprobc or electron diffrac tion study has many difficulties. It may be hoped that instrumental advances will reme dy this situation (greatly improved micro probe definition can be anticipated, for ex ample). Turkcvich's "World of Fine Parti cles"" is surely with us. Quantitation.--Under industrial circum stances, there is little difficulty in estimating the quantity of asbestos in a given sample of air. From this, the surface area of the fibers can be estimated or directly measured by nitrogen absorption or other techniques. It is even possible to conceive of gravimetric methods, rather than the more laborious Fig 4.--Single, short fibrils collected 3/16 of mile downwind of chrysotile source. Arrow Indicates posi tion of clay particle. counting of fibers. Quantitation is much more difficult in ambient air samples and, in our experience, only approximations can presently be obtained. since not only must number be categorized Current Approaches to Asbestos Air Sam as fiber and fibril, but the surface area and pling.--With the foregoing factors in mind, potential biological effect might be quite the absence of published information on as different with the same total chrysotile bestos levels in urban ambient air may be mass, with different percentage fibrillation. understood. Few air monitoring agencies The proportion of fibers to fibrils cannot be have had available the technical equipment determined without the electron microscope. for the examination of ultramicroscopic as Size.--Thus, a critical factor in studying bestos fibrils. Moreover, even those fibers asbestos air pollution is the utilization of seen by optical microscopy in air samples techniques which will measure very small required elaborate techniques (such as elec- particles. It is unlikely that approaches tron diffraction or microprobe analysis) for which do not include the electron micro positive identification. scope will be effective. Indeed, one might Present approaches to quantitating asbes add that high magnification electron micros tos levels in ambient air, using ultramicro copy will be needed, including magnifica scopic techniques, have sought two objectives. tions of at least 20,000x (direct), and prob The first is to obtain a measure of lire mass ably over 40,000 x. Wliilc optical micros- of asbestos per unit of air volume at various . copy may be suitable as a guide for locations in urban centers and later, for occupational asbestos exposure, it has insur comparative purposes, in more rural areas. I mountable inadequacies in studying asbestos This would provide a stable estimate, since pollution of (lie ambient air. fiber size distributions change as sampling is In addition to the fine diameter of the undertaken at different distances from as fibrils, it has been our experience that many bestos emission sources. Equal numbers of of them arc quite short, as well. We have fibers can represent significantly different I l Arch F.nvirtni llnillh--Vol 25, July 1072 ii I l 10 ASBESTOS AtIt POLLUTIOS'--SHUXCHT AT AL amount*, by weight, of asbestos. Moreover, it is not currently known how strongly bio logical clTcct is dependent on filter size. This being so, n measure by mass or weight may bo more conservative for the establishment of air quality criteria and standards, since the biological etTect of a sample dominated by large fibers may be overestimated. Secondly, fiber size distribution is impor tant At the moment, to obtain such a distri bution at each sampled site is time-consum ing, and the presence of other material and existing transfer and sampling methods may distort the observed fiber distribution. How ever, experiences in current studies suggest that these problems can be overcome, and that complete fiber size distributions will be obtained at selected sites in the near future. Sample Preparation.--In our studies, air samples were collected on membrane filters having an effective pore size of cither 0.8/* or 1.2/1. While this pore size is larger than the largest dimension of some asbestos fi brils, it lias been found that the surface charge properties of the filter and the asbes tos, as well os the circuitous path through the filter, allow virtually complete collection of all asbestos material. Both high-volume samplers capable of drawing 40 cu ft/min through an 8 x 10inch filter, and small battery-operated per sonnel monitoring samplers with a capacity of 2 liters/min through 8 sq cm, were found effective in sample collection. Portions of each collected sample were ashed in an acti vated oxygen ashcr which oxidized the mem brane filter and all organic or carbonaceous material in the sample.34 The residue, con sisting mostly of fly ash and mineral matter, was dispersed on a microscope slide by grinding in a solution of 1% nitrocellulose in amyl acetate for two to five minutes. Upon evaporation of the amyl acetate, the dispersal was scanned for uniformity by op tical microscopy and a representative area chosen for transfer to an electron micro scope grid for scanning. During this procedure, those chrysolite fiber bundles present are broken into their elementary fibril form. 'Die grid is scanned at 42,000X in an electron microsco|x\ Typ ically, six grids are prepared of each sample, and three HIO/i X 100// squares of each grid arc scanned. 'Hie mass of nslx'slos is ob tained by measuring the volume of asbestos per grid square and multiplying by the ap propriate density. Figure 4 shows several Isolated fibrils in an ambient air sample ns seen by electron microscopy. Usually, only single fibrils, if any, arc observed in the microscopic field. However, as one takes samples near sources of asbestos, more large filter bundles are present in the initial sample. As these are disperser! during sample preparation, oc casionally some groups of fibrils remain in tact The presence of these bundles, or even localized fibril clumps, gives rise to a varia tion between samples greater than one would expect from statistical considerations alone. However, the scanning of many grid squares serves to average their cflcct Results of Initial Investigations.--Am bient air levels were measured at various sites in New York City. These samples were taken at selected locations of the sampling network of New York City's Department of Air Resources. The sites were nil located on public buildings distant from any known significant source of asbestos. The chrysotile content of ambient air in the various sam pling locations was as follows: Manhattan, 25 to 60, asbestos air level in 10'* gm/cu m; Bronx, 25 to 28, asbestos air level in 10'* gm/cu m; Brooklyn, 19 to 22, asbestos air level in 10'* gm/cu m; Queens, 18 to 29, asbestos air level in 10`* gm/cu m; and Staten Island, 11 to 21, asbestos air level in 10-* gm/cu m. While preliminary in nature, the samples from Manhattan tended to be higher than those from oilier boroyghs. Lowest values were usually from sites most distant from densely populated business areas fSlatcn Island). While amounts ranging from approxi mately 10 to 100 X 10'* gm/cu m of sam pled air may appear to be exceedingly small quantities of asbestos, it is well to recall that chrysotile aslieslns easily frag ments into ultimate fibrils 300 to 400 A in diameter and often 2,000 A or smaller in length. Thus, 10-* gin of chrysotile asbes tos could represent a million fibrils. That Manhattan has higher levels of as bestos than other boroughs is to lv expected, as greater use of asbestos in building con struction takes place in I hat Imrongh. Dur ing the past ten years, it has lieen common .Arch ICiiriritn Iltullli--Vul 25. July 1072 Pr ta. pior tx tlv or o\ pNt OK IS-- C:r lo\ic. wS da-Nrf riv SO: ar: upr wir vr- 7 me: in r of : foil: lev* a;:* AIT; 10four rv -a T esta tker na:: be i area quir car. of Er of cs-v ho - whi. ASBESTOS AIR POLLUTION--SEUKOFF ET AL 11 practice to spray fireproofing material con taining from 10% to 30% asbestos, onto girders, spandrels, .and decking of high-rise office buildings. Often, inadequate precau tions were taken by contractors to contain the spray material and extensive "snowfalls" of asbestos-containing material took place over widespread areas of Manhattan. This practice was of such obvious concern tliat New York City has banned the spraying of asbestos fireproofing, effective ns of Feb 2G, 1972.** Prior to the implementation of New York City's regulations, data were obtained in lower Manhattan at various sites in the vicinity of buildings under construction where spray fireproofing with asbestos-con taining materials was used. During the two days on which data were obtained, the as bestos levels in 10*' gm/cu m were as follows: 6ite 1, downwind from a spray Eourcc, 45 to 80; site 2, 45* downwind from one source and upwind from others, 15 to 30; site 3, upwind from any source, 20; site 4, down wind from a spray source. 45; and site 5, upwind from any source, 20. Hie data in New York have been supple mented by measurements in other urban and in more rural areas. The chrysotilc content of air in three selected locations was as follows: Philadelphia, 45 to 100, asbestos level in 10*' gm/cu m; Ridgewood, NJ, 20, asbestos level in 10*' gm/cu m; and Port Allegany, Pa, 10 to 30, asbestos level in 10*' gm/cu m famositc fibers were also found in the air of this community; a facto ry using this material was present). . These data, though still limited, serve to establish that, at least in the areas sampled, there is a background of chrysotilc contami nation of the ambient air and that this may be higher about construction sites in urban areas. Much more information will be re quired, however, before reliable estimates can be made concerning quantitative levels of such contamination. Epidemiological Perspectives Environmental Disease.--The occurrence of asbestos pollution of urban air is now established. What has not been defined, however, are the dimensions of disease which may lie associated with this jioliulion. Indeed, it Is hardly proper to speak of "as bestos air pollution" in general terms. There arc different sets of circumstances in which such pollution can occur, varying in inten sity, intimacy, and duration of exposure. Lapsed Period.--A problem common to all types of asbestos air pollution is the long lapsed period between onset of exposure and appearance of disease. In general, this is 20, 30, 40, or more years insofar as neoplasia is concerned. There are variations, of course. It may be that intensity of exposure is one such variable; others could include fiber va riety, fiber size, competitive risk of asbestosis,*8 cofactors such as cigarette smoking," trace elements, and perhaps other concomi tant air pollutants. Defined Populations.--It should be recog nized that the different kinds of asbestos air pollution are not limited to well separated compartments. Exposure to general commu nity asbestos air pollution may be over whelmed by indirect occupational exposure, in the ease of a construction workman. Simi larly, the asbestos inhaled by virtue of fami ly contact in the household of an insulation worker could hardly be attributed to the scant asbestos fibrils in the air of a rural community in which that employee hap pened to live. Such permutations are com mon and may be misleading unless identi fied. When considering neighborhood air pollution about an asbestos plant (30 years ago, since it would be these people with whose fate we would now be concerned) it is well to remember that, at least in the 1930s and 1940s, people who worked in a plant tended to live near it Thus, the population about a plant being studied would have to be well characterized, to identify those with direct occupational exposure, before the ef fects of neighborhood contamination could be evaluated. Sources and Control Sources for nsbestos air pollution can be looked at in two ways. They can be identi fied and measured without reference to ex posed populations. Epidemiological atten tion may then be attracted to these "con tamination sources in search of disease." Alternatively, sources for asbestos air pollu tion can be studied in'relation to their po tential for ex|iosurc of htunan populations. Arrli Environ IlentIli--Vo! 25, July 1972 X 1' 12 ASBESTOS AIR POLLUTION--SELIKOFF ET AL At this time, both approaches arc ham pered by inadequate information on U>c relative significance of peak exposures com pared to constant background contamina tion. There is clinical evidence which indi cates that heavy cx|>osurcs for brief periods (days, weeks, months), with retention of the inhaled fibers for the rest of the individ ual's lifetime, may carry serious disease potential.37 Therefore, intermittent high peak exposures may carry an unusual risk, especially when added to the cumulative retention associated with background pollu tion over long periods of time. Adequate information is needed concern ing the natural history of asbestos air pollu tion, including persistence, variations with meteorological conditions, and ultimate fate.13*42Asbestos fibers, being mineral, may persist in the environment for long periods. It is not known, however, if this is so, or to what extent attrition occurs by a variety of physical processes. We have found amosite asbestos fibers in the settled dust and in the household air, within homes which liad been occupied 15 years before by workmen of an amosite factory. Similarly, both settled dust and ambient air in a construction work man's home contained chrysotile fibers at levels beyond those usually observed as background. Neighborhood contamination from factory sources may also be associated with long persistence of the mineral fibers. In preliminary studies, we have found this to be true of both superficial soil contamina tion and settled dust on attic rafters in such neighborhoods. It is apparent that informa tion concerning persistence and fate of as bestos air pollution would be important, if only as a background to the evaluation of air levels from current emission sources. Natural Sources of Asbestos Air Pollu tion.--It is likely that some air contamina tion occurs from natural sources. Serpentine rock outcroppings occur in many parts of the United Stales and other countries. Studies in our laboratories suggest that, on an ultramicroscopic level, serpentine very frequently contains some fibrous mineral comixmcnts, which arc properly classified as chrysotile. In addition, some outcroppings contain frank chrysotile veins. Such chrysotile-containing rocks arc widely distributed, although not necessarily in commercial concentrations. Nevertheless, abrasion and weathering of such surfucc formations might be accompanied by release of chrysotile fi bers into the surrounding air. Industrial and Commercial Sources.--Al though natural sources for asbestos air pol lution should be considered, it is likely that they add only an infinitesimal amount to the asbestos air burden in urban areas. Most is derived from commercial and industrial sources. Here, emission-source inventories can be prepared and would include trans port and storage of raw fiber supplies, man ufacture of the many useful asbestos-con taining products, transport and end-use of these products, their weathering, and ulti mate disposal as waste. In general, the po tential for pollution varies with the degree of fixation of .the fiber in the product Approximately two thirds of the asbestos used in the United States is used in con struction products. Ship building and repair, and waste disposal of asbestos products are important areas for study. Spraying of as bestos-containing mineral fiber insulation has already been mentioned. Factory emis sions arc an obvious, and controllable, diffi culty. Housekeeping in all asbestos-using fa cilities may turn out to be a knotty problem, and ultimately associated with much asbes tos air pollution. This investigation was supported in part liy Public Hcnllli Service grants OH 00.105 and F.S 00358. 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Ann NY Acad Sei University Press, 1970. pp 108-110. 132:530-548, 1965. 21. Sundius N, Bydgcn A: Dcr ataubinlialt einer 37. Selikoll IJ, Bader RA. Bader ME, et al: aabesiosis-lungen und die bcschaflcnhcit der sogenn- Asbestosis and neoplasia. Amer J Med 42:487-496, h ter asbestosis . korperehen. Arch Cewerbepoth 8:2G- 1967. I- 80. 1938. 38. Asbestos: The Need for and Feaiibility of Air 22. Beattie J, Knox JF: Studies of mineral con Pollution Control*. Committee on Biological Effects tent and particle sire distribution in the lungs of of Atmospheric Pollutants. Washington, DC, Na \ asbestos tcxlilo workers, in Davies CN: Inhaled tional Academy of Sciences, 1971. t i ERRATUM In a recent nrliclc* by Slicrwin anti Yuen, "Silicone Fluid for Ihc Metering and Monitoring of Nitrogen Dioxide" (24:331, 1972), the number "5.23 ppm" in tins l I third line of column 1 on page 331 should read "3.93 NO-." I I Arch Environ Health--Vol 25. Juiy 1072 i I!