Document J3NnoKNRGeG2QNmxGmNEp1Qm6

4m. On* Hit. V* II. * t-4. I * ' NOTE: THK non impmt r. * ri N-Oirn,. i j i i THE METHOD USED BY THE US. PUBLIC HEALTH SERVICE FOR ENUMERATION OF ASBESTOS DUST ON MEMBRANE FILTERS Q. H. Edwaxbs and J. R. Lynch U-S. Department of Health, Education, and Welfare, Public Health Service. Bureau of Dbeaie PrvmiUoc and Environmental Control, National Center Tor Urban and Industrial Health. Oecupa* 1 Hmhh Program, 1014 Broadway, Cincinnati, Ohio (AreanmOO May 1967) Ahirnl Samphi of air-bome ndnenl dusts are collected by drawing air through ceihjlose Otar membrane Alters. Paruefcs smaller than nominal pore nzt are retained. Varying [ rats and filter bolder utnuuii the ilmnbuoon of dint across the filter face. Samples I on standard microscope slides using a high viscosity solution of membrane tiller MMriai it a mixture of diethyl oxalate and dimethyl phUntate to render the filter tnrapeuant. The meat ie ruble for 2S-30 days, but after tius period mtgtatxn of the dost | The gram aod fiber dust pnntdcv which lie on the mrthcr of the filter, are counted with a usmg 10X ije piuiiit and a 4 mm "high-dry" objective. The )W*d I with a Portoq crauaiia. Coant data am teuoiikd in a form allowing data i and ituhgql antdyaiB by Jemumc eomputar. The method, although not settable r with the tftmliolil limit value for asbestos that was di1 islopad from a i method, is highly suited for developing baste data for a more | i of the heat for asbsatca. INTRODUCTION lM tub earfy epidemiologic studies of the asbestos industry by Fulton (1935) and i (1933), tbs impinger was settled upon as tbs standard method for appraising Since lew fibenwere seen it was necessary to count both grains and fibers to obtain a statisdcalty useful count despite the assumption that ashesosis was caned by fibers. This inconsistency notwithstanding, dust control based on unptngcr regatta has considerably reduced asfaatons where it has been eoosdentiousiy applied in tbo asbestos textile industry. However, a number of investigators (Lynch and Sunn, 1955; Doll, 1935) have suggened other health hazards associated with irlmtiWt and a mote iclcvanl and semilire method is required for estimation of tho hazard, especially in industries using only pan asbestos in their product. A further weakness in the impinger method is that it is hot amenable to long personal samples. It is believed that personal samples best approximate.the worker's actual exposure, and Roach (1966) has recommended a sample duration of iO work shifts for mineral dusts. New methods were therefore needed, am} among those studied were grain and *' * ' 1 '__________ | BB 00 20735". * THIS DOCUMENT WAS -NOT A REtOftD- OF PPG INDUSTRIES, INC. DiD NOT COME FROM IT'S FILES AND CAMN'tff'fiE A0THENTICA1ED BY PPG INDUSTRIES, INC.7' 3227 i 3 G. H. Edwajum and J. K Lymcn fiber counts at 430X phase contrast on membrane filters that had been made trdttsparent. This paper.deals with the development and standardization of this method. The principle viable which needed to be considered was the mounting procedure in relation to maximum transparency and the cilcct of time on the dimensional stability of the mount. Methods using immersion oil, airplane ghte or acetone were found to be either too cumbersome or resulted in an imperfectly cleared or mottled filter, particularly as viewed With phase contrast optica. In methods which involved the application of liquid over the dust deposit the movement of the meniscus across the deposit sometimes caused redistribution of the dust. The use of a 50-50 mixture f diethyl oxalate-dimethyl phthalate was attempted and found to result in satis* factory clearance. However, since this medium dissolved the filter, the migration of particles resulted in changing counts with time and needed to be examined to evaluate the method. SAMPLING PROCEDURE Samples for count an collected on MiUipore* type AA filters* by personal samplers operated by battery powered pumps worn by the employees, and as simul taneous samples collected in conjunction with impingers. The filters are contained in plastic filter holders and are supported on thick pads which also aid in controlling the distribution of air 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 aiso hit.the filter and possibly cause damage. As an alternative, the face cap may be left is place and tha small plug removed. The passage of air through this 4 mm opening at a flow rate of 2 L per min produces a velocity of 265 cm/sec, which yields an impaction parameter of -0-0811 Tor 1 micron (p) unit density spheres. Although this impaction parameter would predict a very low collection efficiency of. Ip particles by impaction, some larger partides would tend to be impacted on the center of the filter. This was found not to alfeci count distribu tion, which b dominated by small particles; however, it does result in obscuring a TMn portion of the filter, porticuibrly if many large particles are present, as In friction product plants. The thud alternative was to drill 6 additional 4 mm hobs in some face and to fit these perforated caps to the filter bolder during sampling. Tib.reduced the velocity to 3S cm/sec thus etiimnatmg the impaction problem while Still protecting tha filter from damage. MOUNTING'THE SAMPLE - The "wnwft'm medium, used in this method b prepared by dissolving 0*1 g of membrane filter per-ml of a 1:1 solution oTdimethyl phthalate and diethyl oxalate. The **,~~f proportions of the 3 components are not critical, but the medium must have as high a viscosity a possible without being difficult to handle. The index of refraction of the medium Una prepared b No * 1*47. *MHBfiOre* fDtm are l^meil b dm rarer dree the method was developed asms dm brand of SUra, Siimbr techraancs may bedevelotwd foe other 6her brands. .. TRaac. W. awl Won*. J. A. 11*52) An**. M. tijj. S, 4. i THIS DOCUMENT WAS not a-REOORD of I?? 'TMSTR,ES* INC- DID not gome from pTvSpF^ca^otbea^het,catEd BY .PPG INDUSTRIES, INC. '' . I BB 0020736 1 . 3223 w j j. > NOTE: THIS 00t- NOT COME FRO''* r'"G 1W Miked for cmunmtian of astMea dial on mamhraue filters J To prepan. a sample for microscopic examination, a drop or the mounting medium H placed on a freshly cleaned standard (25 mm x 75 mm) microscope 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 an is excised from the filter using a scalpel and foreeps^and placed dust side up on the drop of mounting solution (Fig. ]). A #1J cowslip carefully cleaned with lens tissue is placed over the filter wedge. Slight pressure on the covcrslip achieves contact between it and the mounting medium. Gnriwg of the filter with this method d slow, requiring about 15 min. The sample may be examined as soon as the mount is transparent. The txaraitioc of the dust-supporting substrate from tramlucent solid membrane filter crilulose 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 washing away or redistribution of the dust. The optical homogenity of the resulting mount is nearly perfect, with only a slight background granularity under phase contrast, which disappears within I or 2 days. STABILITY Observers noted a reduction with time in apparent concentration for samples mounted with only dimethyl phthalate and diethyl oxalate. By observation, this loss w due to the migration of the dust partides outward from the center through the grlatinoas material of the fixed mourn, with a decrease in areal concentration. H* cause of this migration was not determined bat may be related to a disordering or distortion of the membrane filter polymer caused by partial solution. To Aimi-- the magnitude of this loss, a group of samples was mounted using 1:1 dimethyl phthalate and diethyl oxalate only, and counted at 1-3 day intervals for periods ranging up to 76 days. Counts were displayed as fractions in per cent of the original, or first day counts (Fig. 2J. At the end of 1 week, samples mourned by this method yielded only 75 per cent of their original values. By 30 days after mounting. I' I tta. X Pmvsii ie'pcfCMaar rf wswl rrock email with tone for the oriental 1:1 dtmrthrl yfrtnlwf anfiyl mate* aoiw amMo^dw^hish vucuiuty mature CMuming CL1 g/mt of : THIS DOCUMENT 'WAS NOT A RECORD OF PPG INDUSTRIES, INC. DID NOT COME FROM IT'S FILES AND CANNOT BE AUTHENTtCAiEtf BY PPG INDUSTRIES, INC. : ______ ;________ " *" 7 BB 0020 737 .. 3229 . NOTE: THIS Of / NOT COME FRi 4 < O. H. Ebwmoi tad J. K Lymm the counts using this method had declined to 40 per cent of their first day value, and continued at this level with no further decline until countine vra* terminated 76 days after mounting. it A group of samples mounted in the method described in the section Mounting tht Samper using high-viscosity mounting medium were counted at 1-day intervals for 11 days. No loss of areal concentration was apparent over this short period and a second group was similarly mounted and counted for a period of 46 days. The composite of these'two series is shown in Fig. 2. No loss of concentration was detectable during the first 30 days, but the count declined to 83 per cent of its original vuiwe by the 46th day, when the series 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 discontinuity during the initial 30 day period. By the end of 62 days, most of the square had disintegrated, and the fragments migrated over an area 16 mm x 17 mm. EVALUATION The fiber samples mounted in the manner previously described are evaluated in term 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 routing phase turret and a 4 atm "high-dry" achromatic objective used for all membrane filter determinations. In all cases IOX Huygens eyepieces, one of which contained a Porton reticle at the lead of the field-limiting diaphragm, were used. The left half of the Porton reticle field served to define the counting area, or field. A ribbon filament Uhumtutor was critically adjusted to provide Kohler fllumina tion through a dear blue filter. - Twenty fields located St random on the sample were counted and total grains, toul fibers, fibers greater then 5p, and fibers greater than IOp were recorded. Any fuvtkk having aa aspect ratio of 3 or greater was considered a fiber. - X2CORDINO OP DATA Sacs It was recognized early in the study of the asbestos products industry that An huge number of samples to be collected would present a burdensome data pro cessingproblem. the data wav collected on forms designed for transcription to punch cards (Ft*. 3). Computer programs were then written to calculate dust concentrations and to produce statistini summaries consisting of mean, standard deviation, median. for any group of samples by plant, operation, job. type; etc. These programs, written in Autoomth'(Fortran II) arc applicable to any problem using the sample and cosmt forms as source documents. Additional analyses possible are correlation and fegressioa of simultaneous samples and Poisson index of dispersion of field counts for various counters. inti* GOCUMENT.WAS NQT A RE "PPG INDUSTRIES, *NC.- DID NOT CO IT'S FILES AND-CANNOT BE AUTHEf. BY PPG INDLfStRIES, INC. I BB THIS DOCUMENT WAS NOT A RECORD OF .J>RGJNySTMES, INC. DiD NOT COMMON IT'S FILES AND CANNOT BE AUTMENTTLAI ED . BY PPG INDUSTRIES, INC,.V (****-1 j_BB 0020739 j * w. 3231 U\J ic. IliiJ 1 - - NOT-COlvlE friUtf rVG r-il TN fcritinrt used tof cmimcniion Of tsbnios dust on membrane (Uteri i * EEO res T/S4 I* eg b>t rta rvsHTKO. ien.t ea i irn n c a u <* Tvrc hatuni count count pww n no. QEEZ3E3 mmci I M > **** uimmtm MMa ran s o no cts. n?T^n unnmm n It IT SCANS M* 31 5 m form weed for the ersfouion at dust waplws talon on membrane Wtera. .t m*i.e. r_. U mm striated naanbrane filter, 3 TM Bnuinat zone ampie, C - General ample, S -- Sequential temple. C * Count (lstX A " Recount. COUNT in's OA/ TOHrX rnrliniri the maaiuficauoa. M. NO provide* far (or csfibnuon purpoeee, and LFmod K trm iiaht-Aeld and ptaa rrwtrm. SUMMARY A *"* for sampling and counting asbestos dust using membrane Alters Ins bats developed and evaluated. The mounting medium developed dears the Alter gently so as to not redistribute the dust deposit, and produces a mount with adequate Ammonal stability for a period of 30 days. This method has been used in developing environmental data in connection with ihe Public Health Service study of the asbestos products industry, and is recommended for research studies in other dusty trades altlionfh not for application to Threshold Limit Values. A system of data handling Involving cketronic computer processing, "which is also applicable to other studies. THIS DOCUMENT WAS NOT/A RECO-D PPG INDUSTRIES, INC. DID NOT COME ,T IT'S FILES AND CANNOT BE AUTHENTICA BY- PPG INDUSTRIES, INC, --b7o020I L . 3232  G. H. Eowawh and J. R. Lynch I REFERENCES Dou. R. (fB5) ft-. J. M 12. *1-15. Dmbhm, W. C. Dalla Valix. J. M, EnwAam, T. I- Miuxa, J. M. and Sams, R. R- (1938) FubL HUh. BuiL No. 241, U.S. Governmem Prmtmp Office. Waalu. D-C. hunt,'W, R, Ooour, A- Matowws, J. L. and Houtz, R. L. (1935) Special Bud. 42, Pom. Dept, of Labor and Induury. Lynch. K. M. and Smtm, W. A. (1933) A-n,J. Cam'tr 24,56-44. RoAQt, S. A. (1946) M ML //>t. A. J. XI, I. | BB 0020741 | 3233