Document 71Gb7YrYN65am3M246YDDdq08

not FOR REPRODUCTION ok 1 t FURTHER DIE^-rUBUTlON. CONFIDENTIAL '&so % PLAINTIFF'S exhibit For Ac!rr.ir.istrollvs Uss C.'.y Drcf'i Copy i / i2 /12 > tlV V s - j* . #. V .i/i K _* t t 1 i 1 * * Vv Jm. nJ ^ V\ i\v^ ^ V i V PLAINTIFFS EXHIBIT U/V8Jf Of9 *W ^ w * t . itre* V I Cc\. ^ *j_4>~m * TV j Tw?w.'W.V*" ,*.Ti.*N \\i | MAKi\H W " ^ UW oI`MW II: C. W- <:' VI I ^C*4< / 4 C W w** Uoj >Tw**m:m*l*! CiCC*i* Svrv>>\ r.tcl Ccn:.'o: Administration * *" PROPOSED CRITERIA AND RECOMMENDED INTERIM STANDARD FOR ASBESTOS U. S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE Public Health Service Consumer Protection and Environmental Health Service Environmental Control Administration Bureau of Occupational Safety and Health Cincinnati, Ohio 00GS36 i- PREFACE Industrial experience has proved the need for criteria and standards to protect the health of workers exposed to an ever-increasing number of potential hazards at their work place. In order to provide relevant data from which valid criteria and effective standards couldJjc deduced,, re.au of.Occupational Safety and Health has projected^ a formal system of research with priorities determined on the basis_ of specified indices. It is intended to present successive reports as studies are completed and standards are sufficiently crystallized so as to bo feasible. The first report, which follows, concerns asbestos. Other reports will follow as the research and evaluation progresses. These standards arc not considered definitive and will be reviewed in the light of additional'data as research con tinues to keep protection of the worker's health as effective as the state of our technology requires. 1 am pleased to acknowledge the contributions made by members of my staff, who developed this project, and the valuable constructive comments made by the "Ad Hoc Review Committee." A list of these contributors and reviewers appears on page ii. Marcus M. Key, M.D. Director, Bureau of Occupational Safety and Health Environmental Control Administration Consumer Protection and Environmental Health Service i .000837 PROPOSED CRITERIA AND RECOMMENDED INTERIM STANDARD FOR ASBESTOS Table of Contents PREFACE ............................................................................. CONTRIBUTORS AND REVIEWERS....................................... INTRODUCTION........................................................................ RECOMMENDED INTERIM STANDARD................................. REVIEW OF PROBLEM............................................................. Uses of Asbestos .................................................................. Exposure to Asbestos............................................. Early Indications of Hazard.................................................. Development of Standards........................................................ MEDICAL ASPECTS OF ASBESTOS ........ EPIDEMIOLOGY........................................................................ - AIR SAMPLING METHODS........................................................ Collecting Sample Mounting Sample Stability Evaluation ANALYTICAL METHODS Internal Standard Technique for Chrysotile............................ External Standard Technique for Chrysotilc............................ Infrafred Spectroscopy............................................................. Differential Thermal Analysis of Chrysotile............................ Indirect Estimation of Chrysotile . ....................................... Evaluation of Methods.............................................................. page i ii 1 3 5 5 6 7 6 U 13 17 20 21 23 24 24 27 31 32 33 35 ill OOQQpt CONCLUSION REFERENCES r?-a '<L& iv 000839 . // ^\ .0/-T. . . INTRODUCTION This report presents the criteria and recommended interim standard ubich were prepared to meet the need for protecting the health of workers exposed to asbestos as delineated in "Position Paper on Asbestos" forwarded to the Surgeon General of the Public Health Service. In addition, available relevant data is made available- for use by the Secretary, Department of Health, Education, and Welfare, in the event that the Occupational Safety and Health Act of 1DG9 is enacted by Congress. Among other provisions, the Act requires the development of criteria by "The Secretary, Department of Health, Education, and Welfare.. .on the basis of such research, demonstrations, and experiments and any other information available to him..." The Bureau of Occupational Safety and Health, after a review of all data and consultations with others, formalized a system for the development of criteria upon which standards can be established to protect the health of approximately 80 million workers from exposure to hazardous chemical and physical agents. Priorities in this system are based on five indices: ' ' ------------ '-- toxicity (l)l'ihe number of workers potentially exposed; (2) the relative/index of a particular substance or physical agent; (3) the incidence of illnesses (or death); (4) the quantity of the substance produced and used in the United . States; and (5) 'the^increase or decrease in the quantity used over a period of years. 00G840 * 2 The judgments of-over 30 industrial hygienists from the states and private industry were considered in establishing a tentative priority list for over 90 chemical and two physical agents. Although an interim standard for coal dust was recommended to the Surgeon General in December 196S as a result of work that the Bureau had already completed, the information contained in this report on asbestos is the first formal presentation of results from the use of the system. 00GS41 I RECOMMENDED INTERIM STANDARD The U. S. Public Health Service recommends that occupational exposure to asbestos dust be controlled so that no person shall be exposed to a greater level than i2 fibersyfoer milliliter based on a count_of fibers gTcnter than 5^j in length as determined by the recommended method, which is described in this report. The interim standard recommended is based on recent unpublished epidemiological investigations by the U. S. Public Health Service and the 196S American Conference of Governmental Industrial Hygienists Threshold Limit Value. It will be subject to review and wall be revised as necessary. It is believed that adherence to this interim standard will reduce to an insignificant risk the occurrence of asbestosis. even among workers who may be exposed to asbestos dust for as long as 30 years. / 000842 / ' * I'* / / DISCUSSION C0GS43 5 REMEW OF PROBLEM Asbestos is a generic term that applies to a number of mineral silicates incombustible in air and separable into filaments. The most widely used in industry in the United States is chrysolilc (3MgO 2Si02 2H2O). a fibrous form of serpentine. Other types include amosite (3MgO IlFcO I6S1O2 2U20); crocidolile (Na.,0 3FcO Fe203 SSi02 1120); tremolite /~Ca Mg3 (SiC^).} J; and anthophyllitc /(MgFe)7 Sig 02o(011)2_/Since chrysotile accounts for about 93 percent of the asbestos used in the United States,^ the information on the relationship between asbestos dust exposure and its effects on workers is centered on the deleterious effects to workers from inhalation of chrvsotile asbestos, and this "dose- ,5 response" relationship is one of the criteria used in setting a hygienic standard for asbestos. Uses of Asbestos Almost one million tons per year of asbestos are used in the United States.1 Approximately 66 percent of the_asbe.stP&JLs.uscd in cement products (building materials); 2 percent is used in manufacture of asbestos textiles; friction materials such as brake linings and clutch facings consume A percent; asbestos paper, 7 percent; floor tile. 10 percent; paints, roof coating, and caulks, 3 percent; plastics, 1 percent; and miscellaneous uses account for 7 percent. * GOOQ 34 6 Exposure to Asbestos The domestic mining and milling of asbestos is a limited industry employing fewer than a thousand workers. Heavy dust exposures to workers in this industry, particularly to those milling the asbestos, have been observed. Heavy exposures to asbestos dust also occur at uncontrolled or poorly controlled operations in the manufacture and application of asbestos-containing products. In the use of asbestos, potentially high dust exposures occur in the mixing process in which asbestos is combined with other materials (cement, asphalt, vinyl, etc.). There are approximately 40,000 insulation workers who are exposed to asbestos dust. These workers also cause secondary exposures to an estimated three to five million other construction workers involved in the construction of commercial and industrial buildings. These same lnsula'tion workers also create secondary exposures in shipbuilding, where up to 60,000 workers may have secondary' exposures. ^ The dust exposure of workers in the construction (three to five million workers) and shipbuilding (250,000 workers) industries is extremely variable. Because of this variation and the small numbers of asbestos workers at any one location, asbestos dust exposures to these workers have never bcen.saUsfactorily estimated. 000S45 t. f 7 An estimated 50,000 workers are involved in the manufacture of asbestos-containing products. This figure does not include secondary manu facture of products which contain asbestos as electrical or thermal insulation, or products which include previously manufactured components containing asbestos. 2 Earlv Indications of Hazard - -- - -- - - ------- ------- Asa result of the increasing use of asbestos minerals, there has been an undercurrent of concern over their role as factors in human disease. Wien asbestos dust is inhaled in excessive amounts, a lung disease termed asbestosis may develop.2 This disease entity will be discussed in the .medical section of this document. The first record of a case of asbestosis was made by Montague Murray in 1900.2 The first complete description of the disease and of the "curious bodies" seen in lung tissue and sputum appeared in 1927 when Cooke4 and McDonald5 reported two cases of asbestosis and listed their reasons for believing that asbestos bodies originate from asbestos fibers that reached the lungs. Publication of their papers aroused general interest in the subject and additional reports appeared soon afterward. Hoffman6 was the first American to call atten tion to the magnitude of the asbestosis problem. In 1918 he reported that 13 deaths from asbestosis had occurred among asbestos tcxtlle_workers, and about the same time pancoast, Miller, and Landis7 reported on 17 cases of 8 asbestosis. Mill's publication was the first pathological report on asbestosis published in the United States, and in that same year, 1930, Lynch and Smith reported on asbestosis bodies found in the sputum of the asbestos workers. In Mere wether's abstract review, 10 emphasis is placed on the rela tion of asbestoris to working conditions. The clinical aspects of this disease are well documented. Gloyne's discussion of the pathology of asbestosis11 is particularly helpful. Middleton's Milroy lectures on pneumoconiosis^ contain a section of asbestosis. Egbert1^ in his summary of the literature reports on 28 fatal cases of asbestosis stated: "Active pulmonary tuber culosis was present in C instances of the total 28 cases; the fatal outcome was primarily the result of tuberculosis in 3 instances." The Annals of the New York Academy of Sciences presents a very excellent and lengthy docu mentation on the "Biological Effects of Asbestos.1 Development of Standards The industrial experience associating exposure to asbestos with the development of a potentially disabling pneumoconiosis in man has amply demonstrated the need for a standard to limit allowable exposures to asbestos dust. The first standard recommended was a threshold limit of .5 roppef for asbestos dust recommended by Dreesen et al.^ In 1936 after they had /- / /' 9 studied 5*12 employees in four asbestos textile plants where massive exposures occurred. The)- found numerous well-marked cases of pneumoconiosis at con centrations of dust above 5 millions of particles per cubic foot of air (mppcf), but only three dcrjbtful cases at concentrations under 5 mppcf. Believing that the 5 mppcf limit recommended by Drecsen et al. was inadequate to give complete working-life term protection against all forms of asbestos, the Committee on Hygienic Standards of the British Occupational Hygiene Society reviewed medical evidence from the United Kingdom and epidemiological data from the United States Public Health Service. In 196S they stated criteria for limiting exposure to chrysotile asbestos and recommended the following:*^ Dust Category Concentration Averaged over 3 Months (Fibers/cm^) Negligible Low Medium High 0 - 0.4 0.5- 1.9 2.0 - 10.0 over 10.0 / JK(Satc: 10 fibcrs/ml is equivalent to slightly less than 2 mppef.) Prior to establishing an asbestos standard based on American experience and applicable to American industry, researchers evaluated the health experience in asbestos plants. They found that the 5 mppcf limit was not sufficiently low to protect the workers who were exposed for 30 years. Balaer and Cooper* reported asbestosis among insulation workers exposed at levels not exceeding the time-weighted average of 5 mppcf. 000S4S 4 / 10 As a result of Its own recent epidemiological investigations considered with the work of others, the U. S. Public Health Sendee recommends an interim standard for asbestos of 12 fibers per milliliter greater than 5 microns in length. The membrane filter method of measurement^used is that in which only fibers greater than 5 microns in length are counted. The British define a "fibre" as a particle longer than 5p and having a ratio of length to breadth greater than 3:1.^ It is believed that this limit will reduce to an insignificant risk the occurrence of asbestos disease among workers eventhose who maybe exposed to asbestos dust for as long as 30 years. However, the following must be emphasized: *' 1. One limit for "all types" does not reflect the differences in biologic activity of the different types of asbestos; " 2. The interim standard does not recognize differing biologic activities of different forms of each type of asbestos; / 3. The limit does not take into consideration differences in trace metal content that may result in display of genetic differences in susceptibility; and V-- 4. The interim standard gives no assurance that it will protect agaijist ' malignancies. oon.^Q? 11 MEDICAL ASPECTS.OF ASBESTOS Asbeslosis Is a diffuse, pulmonary disease in which fibrosis is the dominant reaction to the prolonged retention in the lung of asbestos fibers and/or dust.^ It is now widely accepted that asbestos dust inhaled in suf ficient quantity as occurs in those occupationally exposed, in the absence of dust control, may be carcinogenic to the human lung. *9 In rats the inhala tion of chrysotile has been associated with a 35 percent prevalence of lung cancer. 20 `The question of the significance of the relationship of asbestos to lung or other cancer in the occupational neighborhood is unsettled at presen*t.*/' Asbestos is not a systemic poison. No minimum lethal dose has been established and no distinct blood or urine derivatives have been found. The prin cipal pulmonary lesions caused by asbestos are des cribed/ as regional atelectasis; interstitial, mucosal, and focal fibrosis; and bronchiolar fibrosis. This diffuse non-nodular fibrosis involves the primary framework of alveolar wall, interlobular septa, and visceral pleura with a consequent alveolar-capillary block.Either distortion, distention, or stenosis of the bronchi with a fine diffuse emphysema along withthe fibrosis are additional factors causing respiratory disability. The perivascular fibrosis observed injmost cas^sjcontributes^tojhe development of cor pulmonale or right heart failure. Usually the disease G00S50 process is.dispersed throughout the lung , but is more accentuated 12 sub-plcurallv and at the bases of the Jungs where the amplitude of the breathing movements is greatest. Many alveolae may contain asbestos fibers surrounded by a protein capsule giving an indication of exposure, but not necessarily a diagnosis of asbestosis. Asbestos fibers may con centrate around lesions such as inactive tubercular lesions or bronchiectic areas. The progressive alveolar capillar}' block initially results in a slightly decreased vital capacity, but a normal lung volume at rest. There is fairly normal maximal breathing capacity with normal distribution of inspired gases, hyperventilation first on exercise and later at rest and slightly reduced oxygen saturation of arterial blood at rust. There is a progressive reduction of arterial oxygen saturation on exercise as well as a decrease in oxygen diffusion capacity. The arterial oxygen saturation may __ , a. . .* #. . stay within normal limits until late in the disease process, or it may pre cede radiological manifestations. The gaseous diffusion across the alveolar-capillary membrane may occasionally be only slightly abnormal. .......... ......... ........ -a--^ .**- * Breathlessness associated with a cough occurs relatively early and becomes progressively worse. The symptoms begin insidiously with dysp nea of the exertional type and crackling rales later followed by exercise cyanosis and dyspnea. Symptoms of airway obstruction are often absent. 0008S1 13 Clubbing is. present \n advanced cases. Severely impaired ventilation and reduced pulmonary capacity are often found in the advanced disease. The late complications of asbestosis include acute and chronic right heart fail ure and progressive cardio-respiratory failure, both of which are the most frequent terminal scqualac. In contrast to other pneumoconiosis, asbestosis is relatively infrequently complicated by bronchitis, bronchopneumonia, or pneumonia. X-rays, when positive, show a ground glass appearance and occasionally the finest stippling. A honey-combing effect in the lungs with pleural plaques and pleural thickening are also present. The cardiac silhouette may be blurred. Concurrent exposures to other dusts may give a coarse pattern. Othor diseases definitely related to occupational exposure to asbestos include:^ / (1) Bronchogenic Carcinoma - A cancer originating in the bronchi of the lung. (2) Mesothelioma - A cancer originating in the lining of the pleural ....- ....... ' and peritoneal cavities. (3) Asbestos_Wart - A benign fibrotic nodule in the skin resulting from Implantation of asbestos spicules. GGO: * rr I 14 The epidemiological evidence, or thr .ncidcnce and prevalence of these diseases, in the American worker is not known. It was not appreciated that exposure to asbestos dust could produce mesotheliomas, as well as gastrointestinal cancers, until Selikoff studied a cohort of 632 asbestos workers in the insulation trade. His report firmly established that work in this asbestos industry is associated with excessive incidence of asbestosis, lung cancer, pleural and peritoneal mesothelioma, and possible gastrointestinal cancer (1/2 stomach and 1/2 colon).17 In an asbestos workers union in the New York area with G32 members in 1942, there were 349 deaths by the end of 19GS; only 251 were to be expected according to mortality patterns representative of the general population.17 The excess was attributed to asbestosis and lung cancer. *Lung cancer ' accounted for one death in five, seven times the expected rate. No deaths from mesothelioma were expected; yet twenty were observed. The incidence of gastrointestinal cancer was three times the expected. "^Smokers who work in the asbestos insulation trade face over 92 times the risk of lung cancer as compared with non-smokers in other industries^7 000853 15 EPIDEMIOLOGY Two major epidemiological surveys have been performed relating asbestos dust levels with asbestosis. The 1938 United Suites Public Health Sendee survey by \V. C. Drcesen ct al.3 observed that ''clean-cut" cases of asbestosis were found only in dust concentrations exceeding 5 mppef. Only five persons were exposed over JO years to asbestos dust concentrations from 0 to 4.9 mppef. The longest exposure was 1G years to any concentra tion. None of the 39 persons exposed to dust concentrations below 2.5 mppef had a case of asbestosis. Only six persons had been employed more than five years. Three doubtful cases of asbestosis fell in the range 2. 5 to 4.9 mppef. This study was conducted when dust concentrations were high and before industry initiated control methods. Few of the workers studied were exposed for long periods of time to low levels of asbestos dust, 3 which is the environ mental condition most prevalent today. / The British Occupational Hygiene Society's stud}- ''Hygiene Standards for Chrysotile Asbestos"** related airborne fiberj9yclsj.\ith incidence of asbestosis. According to this report, approximately one percent (no more than three percent) of the workers would exhibit early clinical signs of . * asbestosis at an accumulated exposure of approximately 100^ fiber years per cubic centimeter. This parameter relates concentration of fibers with the duration of exposure. The figure of 100 fiber years per cubic centimeter COOSS'l 16 could represent an averageexposure of two fibers per cubic centimeter for 50 years, or four fibers per cubic centimeter for 25 years, or 10 fibers per cubic centimeter for 10 years. , -------- ------------ A third study was initiated in 1964 by the United States Public Health Sendee and is scheduled for completion in 1972. This study will relate the quantities of asbestos dust breathed by the workers to the harmful health effects attributed to asbestos; most particularly cancer. Other environmen tal factors such as worker smoking habits will be evaluated. The primary purposes of this study were to determine the dust levels at which asbestosis occurs and the level at which no excess cancer occurs. Trace metals, as well as the carcinogenic oils in asbestos dust, may be im portant in the mechanism of causation of cancer and asbestosis and arc included in this investigation. COOS' > X Ir' 1 N***7 - 17 METHODOLOGY AIR SAMPLING METHODS The original epidemiology of asbestos by Drecsen ct al.3 used midget impinger count data as an estimate of dust exposure. All of the dust particles seen, both grains and fibers, wore counted since too few fibers were seen to give an accurate measurement. The resulting count concentration was a measure of overall dust levels ratheT than a specific measurement of the asbestos concentration. This method was satisfactory at that time since exposures were massive and the control measures installed to reduce overall dust levels also reduced the asbestos dust levels. As dust levels were reduced, it became necessary to measure the biologically appropriate attribute of the dust cloud. At equal levels of overall dustiness, the concentration of asbestos could vary considerably from textile ............... manufacture (75-S53, asbestos) to insulation (5-25*5- asbestos). Furthermore, / if the limit were lowered below the 5 mppcf used previously and dust counts taken by the impinger technique, it would be necessary to consider the effect of background dust, which could be as high as 1 mppcf. A number of methods for measurement of asbestos dust concentrations have been used in the United States Public Health Sendee epidemiological study of the asbestos product industry. 21,22,23,24 gaScd on the data the Y.' / 'preferred index of asbestos exposure is the concentration of fibers longer COCS^G 18 than 5counted on membrane filters at 430X with phase contrast illumination. 2G This method has been adopted as the standard field sampl- ing method by the United States Public Health Service. Based on measurements in the asbestos textile industry, a concentration of 6 fibers/ml longer than Sp. is appro>rimately equivalent to 1 mppef. If this relationship is used, the intended change in the Threshold Limit Values (TLV) adopted by the American Conference of Governmental Industrial Hygienists (ACGIH) of 2 mppef based on the impinger methods Is equivalent to 12 fibers/ml longer than 5Although the British have re frained from standardizing on a single method of measurement, most recent measurements have been performed by a method essentially identical to the fiber count method described in detail below, and the British interim standards for chrysotile asbestos dust are stated in these terms. * ' When exposures arc measuredin industries other than asbestos textiles, the asbestos fiber concentration is generally lower than ' 12 fibers/ml when the impinger concentration is at 2 mppef. Since the ACGIH TLV is concerned with asbestos exposure, it should be considered exceeded only when tie fiber concentration is over 12 fibers/ml as the dust being counted in the impinger may include cement, resin, and other non asbestos materials. ^ 000857 19 Collecting Sample The recommended atmospheric sampling procedure is the method described by Edwards and Lynch.25 Breathing r.onc samples for count are collected on Milliporie type AA filters in personal samplers operated by battery powered pumps and worn by the employees. The filters are contained in plastic filter holders and are supported on thick pads which also aid in controlling the distribu tion of sir through the filter. Several methods of admitting air to the filter have been attempted. With the face cap removed and the filter completely exposed, the air may enter the filter evenly, but large high velocity particles and foreign objects may also hit the filter and possibly cause damage. As an alternative, the face cap may be left in place and the small plug removed. The passage of air through this 4 mm opening at a flow rate of 2.1 liters/min produces a velocity of 2G5 cm/sec. which yields an Impac tion parameter of 0.0S1 for a 1-micron unit density sphere. Although this impaction parameter would predict a very low collection efficiency of 1jx particles by impaction, some larger particles would also tend to be im pacted on the center of the filter. This was found net to affect count distribution, which is dominated by small particles; however, it does result GOOSES 20 In obscuring a small portion of the filter, particularly if many large particles are present, as in friction product plants. The third alternative was to drill 6 additional 4-mm holes in some face caps and to fit these perforated caps to the filter holder during sampling. This reduced the velocity to 3S cm/sec, thus eliminating the impaction prob lem while still protecting the filter from damage. Mounting Sample The mounting medium used in this method is prepared by dissolving 0.1 g of membrane filter per ml of 1:1 solution of dimethyl phthalatc and diethyl oxalate. The exact proportions of the three components arc not critical, but the medium must have as high a viscosity- as possible without being difficult to handle. The index of refraction of the medium thus pre pared 'is Nd = 1.47. To prepare a sample for microscopic examination, a drop of the / mounting medium is placed on a freshly cleaned standard (25 mm x 75 mm) microscopic slide, using a dropper or applicator. The volume of the drop is approximately 0.05 ml. A wedge-shaped piece about 1 cm x 2 cm is ex cised from the filter with a scalpel and forceps and placed dust side up on the drop of mounting solution. A No. J-l/2 coverslip, carefully cleaned with lens tissue, is placed over the filter w'edge. Slight pressure on the coverslip achieves contact between it and the mounting medium. G00S59 21 Clearing: of the filter with this method is slow, requiring about 15 minutes. The sample may be examined as soon as the mount is transparent. The transition of the dust-supporting substrate from the translucent solid, membrane filter, cellulose ester material to a transparent, optically homogeneous gel is very gentle, and at no time does a meniscus sweep across the dust deposit. Rather, the substrate slowly softens beneath the dust, and there is no opportunity for the washing away or redistribution of the dust. The optica] homogeneity of the resulting mount is nearly perfect, with only a slight background granularity under phase contrast, which disappears within one or two days. Stability Observers noted a reduction with time in apparent concentration for samples mounted with only dimethyl phthalate and diethyl oxalate. Observe- / tion indicated that this loss was due to the migration of the dust particles outward from the center through the gelatinous material of the fixed mount, with a decrease in concentration in that area. The cause of this migration was not determined, but may be related to a disordering or distortion of the membrane filter polymer caused by partial solution. To determine the magnitude of this loss, a gToup of samples was mounted using 1:1 dimethyl phthalate and diethyl oxalate only, and counted at 000860 4 22 one- to three-day intervals for periods ranging up to 76 days. Counts were displayed as fractions In percent of the original, or first day counts. At the end of one week, samples mounted by this method yielded only 75 per- cent of their original values. By 30 days after mounting, the counts using this method had declined lo 40 percent of their first day value, and continued at this level with no further decline until counting was terminated 7G days after mounting. A group of samples mounted as described in the section Mounting Sample using high-viscosity mounting medium were counted at one-day intervals for 11 days. No loss of concentration was apparent over this short period and a second group was similarly mounted and counted for a period of 4G clays. No loss of concentration was detectable during the first 30 days, but the count declined to 85 percent of its original value by the 4Glh day, when the scries was terminated. A 6-mm square of membrane filter with a vacuum-deposited film of carbon was mounted in the manner described to provide a macroscopic observation of the distortion of the filter areas. After a few days, the square began to disintegrate at the edges, but the major portion showed no discon tinuity during the initial 30 day period. By the end of G2 days, most of the aquaie had disintegrated and the fragments migrated over an area 1G mm x 17 mm. 00GS61 23 Evaluation The filler samples mounted in the manner previously described arc evaluated in terms of grain and fiber concentration, and fiber size. Binocular research microscopes equipped with fixed mechanical stages have been used. Phase contrast optics fitted to these instruments include an Abbe condenser with rotating phase turret and a fmm ''high-dry achromatic -objective used for all membrane filter determinations. In all cases 3 OX Huygens eyepieces, one of ubich contained a Porton reticle at the level of the field-limiting diaphragm, were used. The left half of the Porton reticle field served to define the counting area of field. A ribbon filament illuminator was critically adjusted to provide Kohler illumination through a clear blue filter. Twenty fields-located at random on the sample were counted and total grains, total fibers, fibers greater than Sand fibers greater than 10^i were recorded. Any particle having an aspect ratio of three or greater was considered a fiber. 000562 7ANALY ICA L METHODS . 24 Modem analytical methods and instrumentation used in the i dentin cation and characterization of asbestos minerals include x-ray diffraction, atomic absorption spectrophotometry, emission spectroscopy, electron microscopy, electron microprobc, thcrmoannlysis plus the necessary sample preparation procedures.28 Internal St^nihrd Technique for Chrysolite Chrysotile mnv be determined by the x-ray diffraction and internal standard technique. 5 9 Sample Preparation. The substances to be analyzed may be classified as settled dust samples or as bulk samples of process materials. Settled dust samples analyzed for nonfibrous minerals by x-ray diffraction are usually passed through a 325-mesh sieve in the preparatory procedure. Fibrous structures, such as asbestos, do not have the aerodynamic properties associated with approximately spherical airborne particles; hence the / preparation of asbestos-containing settled dusts consists only in a preliminary- screening of gToss particles followed by grinding to less than 3.5 microns. 9 This is accomplished by dry grinding in a mixer mill for ten minutes. Bulk samples may be obtained from the materials used in an industrial process. An alumina-ceramic vial and mixer mill are wed in preparing this type of sample for analysis. A representative portion of the bulk sam ple is pulverized in the mixer mill, as described for settled dusts. 000863 25 Procedure. The ground duct or bulk sample is first scanned with the diffractometer to establish a qualitative diffraction pattern. This preliminary analysis will verify tic presence or absence of chrysotilc and will demonstrate the presence of possible interfering substances, which arc discussed in a sub sequent section. Chrysotilc is confirmed as present by comparison of the sample's qualitative pattern with that of the pure mineral, if the pattern is found, a rough estimation of the percentage of chrysotilc is then made. A mixture of the dried sample and the aquamarine, each weighed separately, is prepared. The combined weights should be approximately 1 g. The percentage of aquamarine in the mixture should be approximately the estimated percentage of chrysotilc in the sample. The mixture is then wotted "with isopropanol and ground in a mechanically driven boron carbide mortar for 15 minutes.. After this final grinding the mixture is dried at 110C and packed in the sample holder of the diffractometer for analysis. The ratio of the area under the aquamarine 3.2S-A peak to the area under the chrysotile 3.G3-A peak Is computed from the digital print-out record. Background corrections are applied to determine the net area of a given peak. The average background count, calculated from the values provided over a fixed interval extending on each side of the diffraction peak, Is used to calculate the total integrated background correction under the -diffraction peak. 000S64 4 N . r) \ %` 2G With the standard curve taken as a reference, the ratio of the weight of aquamarine to the weight of chrysotilc is determined. The percentage of chrysotile is computed from the ratio of aquamarine to chrysotilc, the weight of the dust sample, and the weight of the added aquamarine as follows*. (A x 100)/(S x R) = To Chrysotile Where: A = weight of aquamarine S c weight of sample R * ratio of aquamarine to chrysotilc (by weight) as read from the calibration curve m Standardization. A Brazilian aquamarine is used as the internal standard. The clearest portion of this mineral is selected for milling, anti the ground material which passes through a 323-mesh sieve serves as the source of the internal standard. The sieved fraction of the aquamarine was sized by electron microscopy; 99 < of its panicles measured 3.0 microns or less. The ground chrysotile used in the preparation of the standard samples was also sized by electron microscopy; 99* of its fiber lengths measured 2.5 microns or less. The standard curve is obtained by application of the procedure to a cries of mixtures of aquamarine and chrysotile. This series includes OOGS weight ratios of aquamarine to chrysotile of 0.5:1, 1:1. 2:1, 3:1, 4:1, and 5:1. Each mixture, in approximately 1-g samples, is mixed in the mill and finally ground in a mortar, as described under Procedure. The ratios of 27 the intensities of the aquamarine 3. 2F-A peak to the chrysotilc 3.G3-A peak (both corrected for background) are plotted against the weight ratios to obtain the standard curve. Each plotted ratio is the average of three to five replicate packings and scannings of each mixture of sample and internal standard. External Standard Technique for Chrvsotilo Chrysotilc may also be determined by an x-ray diffraction and external technique. ^0 Procedure. The substances to be analyzed may be classified as settled dust, bulk samples of process materials, or airborne dust samples. The preparation of asbestos-containing settled dusts consists of a preliminary screening of gross particles followed by grinding to fiber lengths of less than 3. 5 microns. This is accomplished by dry-grinding in a mixer mill for ten minutes. Bulk samples may be derived from the starting materials, / intermediates or finished products encountered in industrial processes. A representative portion of a bulk sample is pulverized in the mixer mill as described for settled dusts. The technique of mounting representative portions of dust samples on & molecular membrane filter has been described by Talvilie and Brewer.**1 For this purpose, a known weight of the finely comminuted sample is sus pended in 250 ml of water in an MCA volumetric flask. Proper distribution of the material in water is insured by use of a wetting agent. Then the 000S6S 28 sample, which may include agglomerations, is dispersed with the aid of a small ultrasonic bath. An aliquot of the thoroughly agitated suspension, containing a known amount of the sample, is filtered using a molecular membrane filter. This method provides a sample of known weight on the filter. This technique has proved to be applicable to dust samples containing asbestos fibers whose sizes are of the magnitude described in this paper. In-plant samples of airborne asbestos collected on membrane filters arc analyzed without size reduction. From fiber size measurements made at this facility, the range and the mean values have been determined to be of the same order of magnitude as those of the asbestos standards used to calibrate the method. In-plant samples of airborne asbestos fibers collected on membrane filters may not be uniformly distributed on the filters. As a uniform distri bution of the fibers is required for this procedure, an even distribution of the collected fibers is obtained by removing the sample from its original filter and redepositing it on a second filter. This is accomplished by placing the original filter sample in a test tube containing a few drops of a suitable wetting agent and sufficient water to cover the filter. The test tube is then Immersed in an ultrasonic bath for five minutes to remove the dust deposit from the filter. The original filter is then removed from the teat tube and the suspended dust is redeposited on a second filter using the technique described above. This is also a convenient point to aliquot heavy dust samples. 000567 29 The membrane filter-with the aliquot of dust adhering to its surface is mounted in the x-ray diffractometer. A qualitative scan, usually at l/min, . is run on the sample to establish the presence or absence of asbestos min erals and of possible interferences. The area under the major diffraction peak of each asbestos mineral present in the dust sample is determined in order to calculate the weight of that particular form of asbestos. If the major diffraction peak is affected by that of another mineral present in the dust, then the second most intense peak of tic asbestos mineral is used for a quantitative determination. While determining the area of a peak, the diffractometer is operated at a lowscanning speed (0. 2/min) and a slit combination of 1 beam slit, medium Sollcr slit, and 0.2 detector slit. The area under the peak i$ computed from tbc digital printout record. Background corrections are applied to determine the net area of a given peak. The average background count cal culated from a fixed Interval extending on each side of the diffraction peak is used to calculate the total integrated background correction under the diffraction peak. The net area of a given peak, computed from the printout data, is referred to a standard curve relating peak area, expressed in counts, to the weight of the appropriate asbestos mineral, expressed in milligrams. The latter quantity is the amount of the mineral represented in the aliquot portion pf the analyzed sample. 000868 31 analyses performed for Hie standardization of the method involved two to three determinations per filter. . These absolute deviations, represented as milligrams of a specific mineral, were uniform over most of the usable range of the method. The relative standard deviations were as follows: 1. 8 to 5* for 1 to 10 mg of chrysotilc, 2 to 5% for 1 to ? mg of crocidolitc, and 2 to 5.5" far 1 to 8 mg of amositc. On the basis of these data, the working ranges of the quantitative method are 1 to 10 mg of chrysotile and 1 to S mg of crocidolitc or amositc if the deviations are to be held within the indicated limits. Infrared Spectroscopy Infrared spectroscopy involves mixing a dust sample with potassium bromide to make a pellet which is inserted into the TR spectrometer to obtain^ a spectrum of the sample components. From this spectrum one can Identify the major dust components. Method (Qualitative!. A 0.3-mg dust sample (ground so that greater than 90% of the particles are less than 5 microns In diameter) is mulled for 5 minutes with 300 mg infrared quality potassium bromide until thoroughly mixed. This mixture is pressed in a 13-mm die for five minutes at 25 tons pressure after an initial five minutes of evacuation. A clear pellet about nnnQ^Q 32 0.79 to 0. S3 mm will result. This jxjUct is then placed in the insti'ument and scanned from G to 30 microns. From the resulting spectrum one can identify the asbestos constituents.^2 Method (Quantitative). Although this method has not been used for the quantitative determination of asbestos components, experiments have shown that 10 micrograms of quartz can be detected on cd 3x scale expansion. In a 10 mg sample this is 0.1T sensitivity. Only under certain conditions could asbestos minerals be quantified. Differential Thermal Analysis of Chrysotilc The implication of chrysotile as a causative agent in certain types of pneumoconiosis has resulted in the appearance of numerous methods of analysis (both quantitative and qualitative) for chrysotile. One of these methods is differential thermal analysis (DTA). * The relatively simple DTA experiment measures temperature difference between a sample and an inert reference material as both are heated or cooled at a uniform rate. By indicating the gain or loss of heat from a system, DTA signifies when a component undergoes a physical change such as fusion, sublimation, or vaporization. Since these physical changes generally occur at different temperatures, a unique thermogram can be ob tained for most thermally active materials. 000870 33 While the principle behind DTA has been known for a long time, it has only been recently that acceptable thermal analysis equipment has become commercially available. Consequently, the DTA technique will undoubtedly improve with time. A large number of chrysotilc samples from various locations throughout the world have already been characterized by DTA.33-3G The two principal reactions with chrysotilc arc a broad endolherm between COO and 720C and an exothermic peak about 810C. These- peak locations can be shifted by varying the particle size of the sample or the heating rate. Differential thermal analysis has also been used to detect the presence of chrysotilc in filled resins.3? Indirect Estimation of Chrysotile An indirect estimation of chrysotilc may be made by utilizing the / determination of magnesium in chrysotile-bearing samples by atomic absorp tion spectrophotometry. Chrysotile asbestos, a hydrated magnesium silicate, is readily broken down by mineral acids. On acid treatment the combined magnesium is dis solved out and can be determined by atom absorption. If the general formula (3MgO 2Si02 2HoO) is used for chrysotile, the theoretlca.1 magnesium content is about 26%. With this information and the 000871 if 0 W' 34 magnesium content of a given sample, it would be possible to calculate the approximate amount of chrysotile in the sample. The assumption would have to be made that the sample contained no other magnesium-bearing compounds other than chrysotilc. Most of the samples analyzed to date have been airborne particulates collected on membrane filters. Sample Treatment. To the membrane filter sample in an acJdclcaned Phillips beaker is added 10 ml of GN 1IC1. The sample is then heated on a hotplate (130C) for 20 to 30 minutes to totally break down the chrysotilc. The resulting solution is transferred to suitable volumetric glassware and adjusted to a known volume. Analysis. The magnesium content of the sample is determined by atomic absorption spectrophotometry. Both single element and multielement hollow cathode devices have been used to produce the Mg 2S52A resonance / % line which is used for the analysis. The percent absorption at this line is used to calculate the magnesium content of the samples. Aqueous standards arc prepared from a stock solution made from a pure magnesium compound and a standardization curve is run. The range of the method as used is 0 to 2^ig of Mg per ml of solution. Each standard is 0.3N in HC1. The absorption for unknown samples is referred to the standard curve. The magnesium content in ug per ml is determined, and a firyil value 000872 for total magnesium in the samples is calculated by using the total volume figure for each sample. This method has been used primarily for small samples (0.20^tg) obtained by using personal samplers. Large samples require such dilution that considerable error may le introduced by dilution factors alone. Evaluation of Methods There is no recommended procedure for the determination of chrysolilc. Additional research is needed to develop analytical techniques which are capable of permitting a differentiation between the massive and fibrous forms. Also, there is a need for more sensitive procedures to identify single fibers which arc encountered in biological samples. 36 CONCLUSION The criteria, the interim standard, and the method for the collection and evaluation of dust exposures to asbestos recommended in this report are based on the best epidemiologic data and analytical methods that now exist. On the basis of these data an interim standard is recommended to control workers' exposures to asbestos at no more than 12 fibers per milli liter as determined by the recommended method of counting only those fibers greater than 5 microns in length. The criteria do not include desirable data apt lobe developed; c.g., all of the facts that should be known about asbestosis. the relationship be tween exposure to the various forms of asbestos and the increased incidence of cancer associated with workers exposed to asbestos, the relationship i between asbestos dust levels and minimal health effects. Nor is there a recommended analytical technique to differentiate massive forms of asbestos from the fibrous forms although several techniques arc described in this report. As the results of additional research in these and other areas become known, the criteria and interim standard for asbestos and the techniques utilized in control will be reviewed and modifications issued if necessary'. 000873 37 REFERENCES 2. Hendry, N.W. The Geology. Occurrences, and Major Uses of Asbestos. Annals of the New York Academy of Sciences, Vol. 132, Art. 1, pp. l-7r.fi. 19C5. Biological Effects of Asbestos. 2. Asbestos position paper. DHEW, USPHS, BOSH. 19G9. 3. Dreescn. ct al. A Study of Asbestos in the Asbestos Textile Industry. Public Health Bulletin No. 2-1, August 1938. 4. Cooke. W.E. Pulmonary Asbestosis. British Medical Journal, Vol. 2, pp. 102-4-1023, 1927. 5. McDonald, S. Histology of Pulmonary Asbestosis. British Medical Journal, Vol. 2, pp.-1025-1926, 1927. G. Hoffman. F.L. Mortality from Respiratory Diseases in Dusty Trades (Inorganic Dust). Bulletin of U. S. Bureau of Labor Statistics No. 231, ^ pp. 176-160. 192 S. 7. Pancoast, H.K., T.G. Miller, and H.R.M. Landis. A Roentgenologic Study of the Effects of Dust Inhalation Upon the Lungs. Transactions. Association of American Physicians, Vol. 32. pp. 97-108, 1917. 8. Mills, R. G. Pulmonary Asbestosis; Report of a Case. Minnesota Medicine, Vol. 13. pp. 495-499, 1930. 9. Lynch, K.M. and W.A. Smith. Asbestos Bodies in Sputum and Lung. >. Journal of the American Medical Association, Vol. 95, pp. 659-661, '1930. 000874 38 10. Mcrcwclher. E.R.A. A Memorandum on Asbestosis. Tubercle. Vol. 15. pp. C9-S1; 109-118; 152-159. 1933. 11. Gloyne, S.R. The Morbid Anatomy and Histology of Asbeslosis. Tubercle. Vol. 14. pp. 445-451; 493-497; 550-558. 1933. 12. Middleton, E. L. Industrial Pulmonary Disease Due to the Inhalation of Dust. Lancet. Vol. 231. ppl-9: 59-G4, 193G. 13. Egbert, D.S. Pulmonary Asbcstosis. Report of :t Case with Necropsy Findings. American Review of Tuberculosis, Vol. 31, pp. 25-34, 1935. 14. Lane, ct al. Hygiene Standard for Chrysotilc Asbestos Dust. Annals of Occupational Hygiene, Vol. 11, pp. 47-69, 1968. 15. Dalr.cr, J.L. and W. C. Cooper. M.D. The Work Environment of insulating Workers. American Industrial Hygiene Association Journal, Vol. 29, No. 3, pp. 222-227, May-June 19GS. 16. The Pneumoconioses. American Medical Association Council on Occupational Disease. Archives of Environmental Health, Vol. 7, pp. 130-171, August 1963. 17. Selikoff, I.J., E.C. Hammond, andj. Churg. Asbestos Exposure, Smoking, and Neoplasia. The Journal of the American Medical Association. Vol. 204, pp. 106-112, 1968. 000875 J V:-.; ) 9* * . M .: - v 39 IS. "Asbestos" Report of the Section on Nature and Prevalence Committee on Occupational Diseises of the Chest. American College of Chest Physicians, Diseases of the Chest, Vol. 45, p. 1, January 19G4. ' ID. Gross, P., M.D. andR.T.P. deTrcville, M.D. Ferruginous Bodies on the Human Lung. Archives of Environmental Health, Vol. 17, September 19G5. 20. Gross, P., M.D., ct al. Experimental Asbestosis in the Development of Lung Cancer in Rats with Pulmonary Deposits of Chrysotilc Asbestos Dust. Archives of Environmental Health. Vol. 15, pp. 343-355, September 19G7. 21. Ayer, H.E. andJ.R. Lynch. Motes and Fibers in the Air of Asbestos Processing Plants and Hygienic Criteria for Airborne Asbestos. Pro ceedings of an International Symposium Organized by the British - Occupational Hygiene Society, pp. 532-522, September - October,. 19G5. 22,, Lynch, J.R. and H.E. Ayer. Measurement of Asbestos Exposure. Journal of Occupational Medicine, Vcl. 10, No. 1, pp. 21-24, January 19GS. 23. Lynch, J.R. and H.E. Ayer. Measurement of Dust Exposures in the Asbestos Textile Industry. American Industrial Hygiene Association Journal, Vol. 27, pp. 432-437, 19GG.` * 24. Keenan, R. G. andJ.R. Lynch. Techniques for the Detection, Identification and Analysis of Fibers. (Draft 3/5/69 - presentation at the American Industrial Hygiene Association Conference, Denver} 1969. . 000876 *) #* 40 25. Edwards, C.H. and J.R. Lynch. The Method Used by the U. S. Public Health Service for Enumeration of Asbestos Dust on Membrane Filters. Annals of Occupational Hygiene, Vol. 11, pp. 1-6, Pergamon Press 19G8. 2G. Lynch, J.R., H.E. Ayer, and D. L. Johnson. The Measurement of Exposure to Airborne Mineral Fibers. (Presented at the American Industrial Hygiene Association Conference, Denver) 19G9. 27. Ayer, H.E., J.R. Lynch, andJ.H. Fanney. A Comparison oflmpingcr and Membi*ane Filter Techniques for Evaluating Air Samples in Asbestos Plants. Annals of the New York Academy of Sciences, Vol. 132, pp. 274-2S7, 19G5. 26. Keenan, R. G. and R.E. Kupcl. Modem Analytical Techniques for Evaluating Mixed Environmental Exposures to Fibrous and Particulate Dusts in the Asbestos Industry. Presented at the Dth Conference on Methods in Air Pollution and Industrial Hygiene Studies, Pasadena, , California, 19G8. 29. Crable, J.V. andM.J. Knott. Application of X-Ray Diffraction to the Determination of Chrysotile in Bulk or Settled Dust Samples. American Industrial Hygiene Association Journal, Vol. 27, p. 383, 1966. 30. Crable, J.V. Quantitative Determination of Chrysotile, Amosite, and Crocidolite by X-Ray Diffraction. American Industrial Hygiene Association Journal, Vol. 27, p. 293, 19GG. onnft'7'7 . 41 Talvitie, N.A. andL.W. Brewer. X-Ray Dilfraction Analysis of Industrial Dust. American Industrial Hygiene Association Journal, Vol. 23. p. 214, 19G2. Taylor, D.G., C.M. Ncnadic. and J.V. Crablc. Infrared Spectra for Mineral Identification. American Industrial Hygiene Association Journal (In Press). Qaiscr, M.A., M.K. Ali, and A. Khan. Mineralogy of Some Asbestos from Northwest Pakistan. Paldstan Journal of Scicnllfic Industry' Research, Vol. 10, pp. 110-120. 1907. Martinez. E. The Effect of Particle Size on the Thermal Properties of Serpentine Minerals. American Mineralogy, Vol. 1C, p. 901, 19GG. Faust, G.T., andJ.J. Fahey. The Scrpentino Group Minerals. U. S. Geological Survey Professional Papers, 3S4-A, 92 p., 19C2. * Vermaas, F.ll.S. The Thermal Characteristics of Some Transvaal, Serpentines and the Production of Forstcritc. Journal of the Chemical Metal and Mining Society of South Africa, p. 191, January 1953. Manley, T.A. Characterization of Filled Amino Resins by Thermal Analysis. Plastic Institutes Transactions, Vol. 35, p. 525, 19G7. 000878