Document 1DzELMq1RZD0QbdbDzQnb37Z

MEASUREMENT OF ASARCO ELP 0003603 Asbestos Textile Institute 1971 Printed in U.S.A. Price: S 1.00 per copy CONTt. SCOPE ............................................................... DEFINITION ..................................................... OUTLINE OF METHOD .................................. APPARATUS AND MATERIALS ................... CLEANLINESS.................................................. PREPARATION OF MOUNTING SOLUTION AEROSOL FIELD MONITOR AND FILTERS CALIBRATION OF EQUIPMENT .................. SAMPLING......................................................... COUNTING ...................................................... CALCULATION OF RESULTS ....................... INDUSTRIAL HYGIENE WORK SHEET ..... BIBLIOGRAPHY............................................... ASARCO ELP 0003604 ctile Institute 1971 ted in U.S.A. 51.00 per copy 2 CONTENTS Page ' SCOPE ................................................................................................................ 5 ' DEFINITION ..................................................................................................... 5 OUTLINE OF METHOD .................................................................................. 5 APPARATUS AND MATERIALS ................................................................... 5 CLEANLINESS.................................................................................................... 7 PREPARATION OF MOUNTING SOLUTION .............................................. 7 AEROSOL FIELD MONITOR AND FILTERS .............................................. 7 CALIBRATION OF EQUIPMENT .................................................................. 7 SAMPLING........................................................................................................ 10 COUNTING ....................................................................................................... 11 CALCULATION OF RESULTS ........................................................................ 14 INDUSTRIAL HYGIENE WORK SHEET ..................................................... 15 BIBLIOGRAPHY ................................................................................................ 16 3 ASARCO ELP 0003605 SAMPLING EUUIPMENT USED IN THE MEMBRANE FILTER METHOD .J 1. SCOPE: 1.1 This method covers a procedure fo fiber concentration in air. The proc( the determination of concentr' ! using phase contrast microscop. This method is also useful for the than 5 microns, the minimum lengt by the inherent limitations of ordina contrast optics. Further, this metho determinations only in areas where predominantly or entirely asbestos cedures for distinguishing between as: Ail fibers detected by this procedu fibers and are reported as such, uni hand to warrant other assumptions. This method can be used to assess concentrations to standards as set ft vincial statutory requirements for Asb 2. DEFINITION: 2.1 A fiber is any particle having a leng greater. 3. OUTLINE OF METHOD: 3.1 Airborne asbestos fibers are collected of air through a membrane filter by fibers are deposited on the filter. A representative section of the f i on a microscope slide, and exa .et (or 400x) using phase contrast optics, of fibers observed in a given area unde this figure is used to calculate the nun meter (cc.) of air sampled. Fiber concentrations are categorized v following manner; total number of fil rons, and greater than 10 microns per c1 4. APPARATUS AND MATERIALS: 4.1 Sample Collector: The samples shall be collected on a filt 45 ASARCO ELP 0003606 1. SCOPE: 1.1 This method covers a procedure for the determination of asbesto* fiber concentration in air. The procedure is designed specifically for the determination of concentrations of fibers 5 microns or longer using phase contrast microscopy. This method is also useful for the determination of fibers shorter than 5 microns, the minimum length detectable being limited only by the inherent limitations of ordinary light microscopy using phase contrast optics. Further, this method is meant to be used for fiber determinations only in areas where airborne fibers, if present, are predominantly or entirely asbestos fibers; it does not specify pro* cedures for distinguishing between asbestos and other types of fibers. All fibers detected by this procedure are assumed to be asbestos fibers and are reported as such, unless independent evidence is at hand to warrant other assumptions. This method can be used to assess conformance of asbestos fiber concentrations to standards as set forth by Federal, State, or Pro vincial statutory requirements for Asbestos Threshold Limit Value. 2. DEFINITION: 2.1 A fiber is any particle having a length to diameter ratio of 3:1 or greater. 3. OUTLINE OF METHOD: 3.1 Airborne asbestos fibers are collected by drawing a specified volume of air through a membrane filter by use of a suction pump. The fibers are deposited on the filter. A representative section of the filter is removed, properly mounted on a microscope slide, and examined at a magnification of 430x (or 400x) using phase contrast optics. The number and length range of fibers observed in a given area under the microscope is noted and this figure is used to calculate the number of fibers per cubic centi meter (cc.) of air sampled. Fiber concentrations are categorized with respect to length in the following manner; total number of fibers seen, greater than 5 mic rons, and greater than 10 microns per cubic centimeter of air. 4. APPARATUS AND MATERIALS: 4.1 Sample Collector: The samples shall be collected on a filter having a pore size of 0.8 i A5 ASARCO ELP 0003607 H 0.05 micrometers (microns), supported on a thick pad to control air distribution and mounted in a segmented enclosure (filter holder, field monitor) to prevent contamination of the filter prior to ex posure.* 1) 4.2 Cellulose Bands: The segments of the filter holder (field monitor) containing the filter and pad shall remain sealed against contamination until ready for examination. (2) 4.3 Tubing: Rubber or plastic tubing of suitable length is connected to the inlet side of the pump and to the filter holder assembly. One quarter inch inside diameter, non-collapsable tubing is recommended. 4.4 The suction pump shall be capable of providing a constant air flow rate of 2 liters per minute for the duration of a test when connected to the filter assembly through a required length of tubing. It is desirable, although not necessary, that the pump have an explosionproof motor. (3) 4.5 Microscope and Accessories: A binocular microscope fitted with phase contrast optics should be used for counting the asbestos fibers. Any reticle, such as Porton or Patterson Globe and Circle, which projects a constant counting area and has provision for sizing, is suitable. This procedure is written using the Bausch and Lomb phase-equipped microscope and the Porton reticle. All set up procedures correspond with this equipment. However, any good microscope with phase contrast accessories is acceptable. The reticle is mounted in the non-adjustable eyepiece and a stage micrometer is used to calibrate the dimensions of the counting area. Microscope slides size 3x1 inch and cover glasses No. l'A, 18mm. must be used. (1) A suitable filter assembly is a Type A A. 37mm,, 0.8 micron cellulose ester filter, pad and plastic "field monitor" -- obtainable from the Millipore Cor poration, Bedford, Mass, 01730. (2) Cellulose banas for this purpose may be obtained from theW. H. Jelly and Co., Inc., Franklin Park, Illinois 60131. (3) Suitable pumps may be obtained from: al Mine Safety Appliance Co., Pittsburgh. Penna. 15208; b) Willson Products, Div., Reading, Penna. 19603; cj Unico Environmental Instruments Inc., Fall River, Mass. 02720. 6 I 4.6 Miscellaneous: A 1:1 mixture of dimethyl phthalat for preparing the sample mounti1'- m Tweezers, scalpel, lens tissue, a., a ing cleanliness of the microscope and 5. CLEANLINESS: 5.1 All equipment used in fiber countir only for this purpose. Fiber countin; part of the laboratory; and. if pos microscope and accessories should t cedures for care of the microscope ar manufacturer's recommendations. 6. PREPARATION OF MOUNTING SOLUT1 6.1 The mounting solution used in this dimethyl phthalate and diethyl oxak when the sample is to be counted wit If samples are to stand for longer perit should be used. This solution may 1 grams of membrane filter material pei pose of the dissolved materia' is to p viscosity as possible without being c viscous solution delays the migratic the center of the mount. The sampi apparent loss in concentration for app 7. AEROSOL FIELD MONITOR AND FILTH 7.1 The monitors may be reused af ai oughly in warm detergent water and ri 8. CALIBRATION OF EQUIPMENT: 8.1 Pump: The frequency of calibration is dep< handling of the instrument. The califc is carried out with a filter in piace. It intermediate standard be used in the ct 8.1.1 Suction pumps equipped with calibrated by a primary slant cedure is shown in Fig. 1. A direct measure of air volume d ASARCO ELP 0003608 ms), supported on a thick pad to control air id in a segmented enclosure (filter holder, it contamination of the filter prior to ex- t holder (field monitor) containing the filter lied against contamination until ready for of suitable length is connected to the inlet the filter holder assembly. One quarter inch ipsable tubing is recommended. e capable of providing a constant air flow e for the duration of a test when connected trough a required length of tubing. It is ecessary, that the pump have an explosion- esr Itted with phase contrast optics should be lestos fibers. Any reticle, such as Porton or le, which projects a constant counting area Ing, is suitable. This procedure is written omb phase-equipped microscope and the Tocedures correspond with this equipment. oscope with phase contrast accessories is l the non-adjustable eyepiece and a stage crate " - dimensions of the counting area. i 1 Incn and cover glasses No. lVj, 18mm. a Tyne AA. 37mm., 0.8 micron cellulos* *ter monitor" -- obtainable from the Milllpora Cor- :a may be obtained from theW, H. Jelly and Co., H31. .toed from: a) Mine Safety Appliance Co., Fitts'illson Procucts, Oiv.. Reading, Fenna. 19603; sruments Inc., Fall River, Mass. 02720. 6 4.6 Miscellaneous: A 1:1 mixture of dimethyl phthalate and diethyl oxalate is needed for preparing the sample mounting medium. Tweezers, scalpel, lens tissue, and a camel's hair brush for maintain ing cleanliness of the microscope and accessories are needed. 5. CLEANLINESS: 5.1 All equipment used in fiber counting should be isolated and used only for this purpose. Fiber counting should be done in the cleanest part of the laboratory; and, if possible, in a separate room. The microscope and accessories should be kept clean at all times. Pro cedures for care of the microscope and accessories should follow the manufacturer's recommendations. g. PREPARATION OF MOUNTING SOLUTION: 6.1 The mounting solution used in this method is a 1:1 mixture of dimethyl phthalate-and diethyl oxalate. This solution may'be used when the sample is to be counted within 24 hours after preparation. If samples are to stand for longer periods of time an alternate solution should be used. This solution may be prepared by dissolving 0.05 grams of membrane filter material per milliliter of solution. The pur pose of the dissolved material is to provide a solution with as high a viscosity as possible without being difficult to handle. The highly viscous solution delays the migration of particles outward from the center of the mount. The samples will remain stable with no apparent loss in concentration for approximately 30 days. 7. AEROSOL FIELD MONITOR AND FILTERS: 7.1 The monitors may be reused after each test by cleaning them thor oughly in warm detergent water and rinsing with distilled water. 8. CALIBRATION OF EQUIPMENT: 8.1 Pump: The frequency of calibration is dependent on the use, care, and' handling of the instrument. The calibration for the suction pump is carried out with a filter in place. It is suggested that a primary or intermediate standard be used in the calibration. 8.1.1 Suction pumps equipped with a floating-ball gauge may be calibrated by a primary standard. The set up for this pro cedure is shown in Fig. 1. A primary standard provides a direct measure of air volume displaced per unit time. / ASARCO ELP 0003609 I Before starting the calibration, be sure the pump battery is fully charged. Fill a 250 ml. graduate with water and invert in a beaker of water. Note the starting level in the graduate. Let the water come to room temperature. Adjust the ball float to one of the lines on the gauge scale. Insert the tubing from the discharge side of the pump into the graduate. Start the pump and timer simultaneously. As the liquid level in the graduate approaches the liquid level in the beaker, simultaneously stop the timer and lift the graduate from the discharge tube. The pump is still operating. The mouth of the graduate should remain below the level of water in the beaker during this step. Stop the pump and note the final, level in the graduate. Calculate the flow rate in standard liters/min. from the formula. Q = V; - Vf x 60 x K T 1000 where: Q Vi Vf T 60 1000 K = flow rate in standard liters/min. = initial volume in ml. from graduate. = final volume in ml. from graduate. = time in seconds of calibration. = conversion from seconds to minutes when T is in seconds. = conversion from ml. to liters. = factor taking into consideration -- tempera* ture and pressure corrections. To calculate the value of K, use the following formula, Pa --Pv _ 530 760 X -160 + F where: Pa = atmospheric pressure in mmHg. Pv r vapor pressure of water at room tempera- - ture in mmHg. F = room temperature in F Duplicate tests should be run at each major scale division on the flowmeter gauge. On a plot of flowmeter setting 8 t ) versus air flow rate (Q), dra the points. From this line, th ing to two liters/min. 'e' adjusted to this setting n An alternate method for cali test meter, which is an i method, the pump's suction ment of water in the meter l displacement is indicated by After the meter is leveled and the apparatus is assembled a watch, time the wet test mett If the meter does not indicat adjustment should be made proper setting. The actual air times a conversion factor (K-. The calculation of the value above in the primary calibrati 8.2 Microscope: Before using the microscope for coun must be in proper adjustment. This pro 8.2.1 Screw the lOx and 43x phas nosepiece and insert the lOx e 8.2.2 Position the lOx objective fslide on the stage, turn on th diaphragm on the condenser ai 8.2.3 Set the phase ring to th men. c 8.2.4 Close the iris diaphragm on : point where only a small brig Adjust the iris set screws on t is centered in the field. 8.2.5 8.2.6 Focus sides of Decagon with Sides will appear blue when fo< ed down. The proper focus is phragm to cover entire field of With the phase ring setting stil piece and insert the centerint 9 ASARCO ELP 000361O the calibration, he sure the pump battery is 111 a 250 ml.'graduate with water and invert *ater. Note the starting level in the graduate, umf room temperature. Adjust the ball he liu__ on the gauge scale. Insert the tubing urge side of the pump into the graduate, and timer simultaneously. As the liquid duate approaches the liquid level in the eously stop the timer and lift the graduate Tge tube. The pump is still operating. The raduate should remain below the level of iker during this step. Stop the pump and el in the graduate. yat rate in standard liters/min. from the /-,-Vfx60xK T 1000 How rate in standard liters/min. nitial volume in ml. from graduate. !inal volume in ml. from graduate. ame in seconds of calibration. conversion from seconds to minutes when T is in seconds. conversion from ml. to liters. actor taking into consideration -- temperaurer * pressure corrections. -alue oi K, use the following formula. Pa --Pv 530 760 460 + F tmospheric pressure in mmHg. apor pressure of water at room temperaare in mmHg. oom temperature in F could be run at each major scale division r gauge. On a plot of flowmeter setting 8- versus air flow rate (Q), draw the best straight line through the points. From this line, the flowmeter setting correspond ing to two liters/min. is determined. The pump should be adjusted to this setting when taking samples. An alternate method for calibrating pumps is by using a wet test meter, which is an intermediate standard. In this method, the pump's suction is determined by the displace ment of water in the meter by the gas being measured. This displacement is indicated by a dial on the face of the meter. After the meter is leveled and the sight gauge properly filled, the apparatus is assembled as shown in Fig. 2. Using a stop watch, time the wet test meter displacement for one minute. If the meter does not indicate two LPM at 6" H2O, then an adjustment should be made on the pump to obtain the proper setting. The actual air flow rate is the calibrated rate times a conversion factor (K) for temperature and pressure. The calculation of the value of K is the same as described above in the primary calibration procedure. 8.2 Microscope: Before using the microscope for counting, its phase contrast optics must be in proper adjustment. This procedure is described below. 8.2.1 Screw the lOx and 43x phase contrast objectives into the nosepiece and insert the lOx eyepieces. 8.2.2 Position the lOx objective for viewing, place a specimen slide on the stage, turn on the illuminator, and set the iris diaphragm on the condenser about half open. 8.2.3 Set the phase ring to the 0 position and focus on the speci men. 8.2.4 Close the iris diaphragm on the illuminator down to the point where only a small bright area is visible in the field. Adjust the iris set screws on the illuminator until this spot is centered in the field. 8.2.5 Focus sides of Decagon with phase contrast control knob. Sides will appear blue when focused up and red when focus ed down. The proper focus is mid-point. Open the iris dia phragm to cover entire field of view. 8.2.6 With the phase ring setting still at 0, remove the right eye piece and insert the centering telescope. Adjust the tele- 9 ASARCO ELP 0003611 8.2.7 8.2.8 8.2.9 scope until the dark circle comes into sharp focus and lock it in position with the set screw provided. Turn the phase ring to the 10 setting. By using the adjust ment screws on the side of the condenser, move the rings until they are perfectly concentric. Rotate the 43x objective into viewing position and turn the phase ring to the 43 setting. Align the two rings as described in 8.2.7. Remove the telescope and replace the lOx eyepiece. Use fine adjustment for proper focus. The microscope is now adjusted for phase contrast viewing at 430k magnification. 8.3 Reticle: The microscope must contain a reticle. Calibration of the reticle is done by means of a stage micrometer. The Porton reticle is a rec tangle divided into two squares. The counting area is divided into six rectangles which constitutes the left square. A series of circles in which every other circle doubles in diameter is located on the top and bottom of the large rectangle. The diameter, D, of each is given by the formula: D = Ia/ 2n where L is a unit of length and N represents the circle number. The length of the large reticle is 200 L units. By measuring the actual length of the rectangle using the stage micrometer and dividing this value by 200, the value of L at 430x magnification is obtained. With this value for L, the actual dia meter of each of the circles can be determined. The calibration of the Porton reticle need be done only once, unless the eyepieces or objectives are changed, the magnification is altered in any way, or the microscope had been disassembled for cleaning prior to use. 9. SAMPLING: 9.1 The suction pump battery must be in a fully charged condition before each test. Recommended battery life for constant pumping rate is furnished by the manufacturer and must not be exceeded for any one test (see paragraph 4.4). 9.2 After inserting pad and filter into each of the plastic holders (Aerosol Field Monitors) they are immediately capped and plugged. The junc tures of the holders are then sealed with cellulose bands. All loaded monitors must be carried to the test sites in a closed carry ing case. An extra monitor must be taken along to serve as a blank. All monitors must be marked for identification. 10 9.3 At the test site, the top section of t filter" testing. The outlet plu- e an appropriate length of 1/4 in,... cu the pump intake. Sampling can be ei In taking general area samples it assembly be mounted on a tripod floor level. For a personal sample tl bly is worn by the person being t close to the person's breathing zone The sampling time should be gauged the filter for satisfactory counting. E avoided since no dilution is possit flow rate of two liters per minute, field monitor must be re-sealed. 10. COUNTING: 10.1 Remove the cover of the field monit be examined. Cut out a pie shaped s> scalpel. The section to be about 1 cm. 10.2 Place a drop of mounting solution on the drop into a shape corresponding tc 10.3 Remove the sample section from the i tweezers and deposit it. sample side t and cover with a clean cover giass. 1 with the tweezers until it is in ir.tima tion and solution, being carefu' ` t cover glass. Mounts may take 3i. . n tion is completely dissolved. 10.4 Place a sample slide on the stage and fo< because dust is retained only in the top The total fiber count should be a: lea.* whichever is less. If a fiber crosses the limits of the coui two adjacent sides are counted. Tne sid. of the counter, but they are always th The fibers counted are estimated as teither the top or bottom of the reticle three size groups: all fibers seen, all fib and all fibers longer than ten microns. 11 ASARCO ELP 0003612 rk circle conies into sharp focus and lock the set screw provided. ag to *he 10 setting. By using the adjust- he the condenser, move the rings actly concentric. ijective into viewing position and turn the 3 setting. .Align the two rings as described cope and replace the lOx eyepiece. Use or proper focus. The microscope is now contrast viewing at 430x magnification. lain a reticle. Calibration of the reticle is micrometer. The Porton reticle is a rec- juares. The counting area is divided into tutes the left square. A series of circles in loubles in diameter is located on the top ictangle. The diameter, D, of each is given where L is a unit of length and N er. The length of the large reticle is 200 L actual length of the rectangle using the ding this value by 200, the value of L at lined. With this value for L, the actual diai can be determined. Ion Teticle need be done only once, unless * are changed, the magnification is altered ->cop- ' `d been disassembled for cleaning -y must be in a fully charged condition nended battery life for constant pumping lanufacturer and must not be exceeded for 14.4). er into each of the plastic holders (Aerosol mmediately capped and plugged. The juncsn sealed with cellulose bands. be carried to the test sites in a closed carrymust be taken along to serve as a blank. All for identification. 10 9.3 At the test site, the top section of the monitor is removed for "open filter'' testing. The outlet plug is removed, the adapter inserted, and an appropriate length of 1/4 inch tubing is connected between it and the pump intake. Sampling can be either general area or personalized. In taking general area samples it is recommended that the filter assembly be mounted on a tripod approximately five feet above floor level. For a personal sample the entire pump and filter assem bly is worn by the person being tested with the filter attached as close to the person's breathing zone as is feasible. The sampling time should be gauged to obtain sufficient material on the filter for satisfactory counting. Excessive dust deposits should be avoided since no dilution is possible. Sampling shall be at an air flow rate of two liters per minute. When the test is completed the field monitor must be re-sealed. 10. COUNTING: 10.1 Remove the cover of the field monitor to expose the filter that is to be examined. Cut out a pie shaped section of the filter using a clean scalpel. The section to be about 1 cm. on the arc side. 10.2 Place a drop of mounting solution on a clean frosted-end slide. Smear the drop into a shape corresponding to the size of the sample section. 10.3 Remove the sample section from the plastic field monitor with clean tweezers and deposit it, sample side up, onto the mounting solution and cover with a clean cover glass. Press lightly on the cover glass with the tweezers until it is in intimate contact with the sample sec tion and solution, being careful not to trap any bubbles under the cover glass. Mounts may take 30-60 minutes before the sample sec tion is completely dissolved. 10.4 Place a sample slide on the stage and focus on the top surface of filter because dust is retained only in the top 10 to 15 microns of the filter. The total fiber count should be at least 100 fibers, or twenty fields, whichever is less. If a fiber crosses the limits of the counting field, only those crossing two adjacent sides are counted. The sides chosen are at the discretion of the counter, but they are always the same for any given counter. The fibers counted are estimated as to length, using the circles at either the top or bottom of the reticle. The counts are recorded in three size groups: all fibers seen, all fibers longer than five microns, and all fibers longer than ten microns. 11 '/ ASARCO ELP 0003613 ' PRIMARY CALIBRATION ns S3 <F c Z o H< cc CO a< < 5LU CC tHil z Fig. No. 1 12 ASARCO ELP 0003614 JON Aerosol Filter Holder (Top Removed) Millipore Filter CJ 3 ASARCO ELP 0003615 10.5 In shifting from one area of examination to another, the choice must ' be random. Once chosen, the field must be counted regardless of the number of fibers observed. In shifting from one field to another the operator should take his eyes away from the eyepieces and concen trate them on moving the stage to a new location. The choice of the new location should be arbitrary, except that areas near the edge of - the sample should be avoided. During the count it is very important to constantly adjust the fine focus back and forth. This brings into focus fibers that might not be seen otherwise. 11. CALCULATION OF RESULTS: The concentration of fibers shall be expressed as the number of fibers per cubic milliliter of air reported to two (2) significant figures only. . (Av. Fiber Count) (Filter Area) Concentration * (Fidd (Sample Volume) (1000) where: Av. Fiber Count: Average Fiber Count Per Size Range. Filter Area: 855mm2 for 37mm. dia. membrane filters. Field Area: Area of counting field in mm2. Sample Volume: Total Time x Flow Rate, Express in liters. 1000: Converts liters to milliliters. If blanks are used, subtract the average blank count of the same size range from the average fiber count. INDUSTRIAL HYGtcNE V 1. STATION NUMBER ppPflRTMPNT PU f>\ ANT DIVISION DATE SAMPLED DATE ANALYZED 1 ti: Tt Et V* .2 STATION LOCATION 3. SPECIFIC PROOUCT AND MATERIALS _____ OPERATORS AND PROTECTION ______ VENTILATING CONTROL .6 DRAFTS T0TAL 7. REMARKS -------------- ANAL YSIS: TLV: SAMPLED BY P/cr F/cc 14 TOT. ASARCO ELP 0003616 a of examination to another, the choice must <en, the fie,ld must be counted regardless of the Tve'd. In shifting from one field to another the ais * away from the eyepieces and concenthe . ,,e to a new location. The choice of the s arbitrary, except that areas near the edge of avoided. During the count it is very important *e fine focus back and forth. This brings into not be seen otherwise. JLTS: shall be expressed as the number of fibers per d to two (2) significant figures only. Count) (Filter Area) a) (Sample Volume) (1000) .age Fiber Count Per Size Range, for 37mm. dia. membrane filters, unting field in mm2. I Time x Flow Rate, Express in liters, o milliliters. the average blank count of the same size range INDUSTRIAL HYGIENE WORK SHEET 1. STATION NUMBER . DEPARTMENT PLANT 01 VISION OATE SAMPLED OATE ANALYZED , . PUMP NUMBER . . RATE .TIME FINISHEO. . TIME STARTED . . ELAPSED TIME . VOL. SAMPLED . .L/M. .MIN. _CC 2. STATION LOCATION 3. SPECIFIC PROOUCT AND MATERIALS (Field Area) 4. OPERATORS ANO PROTECTION (Initials) 5. VENTILATING CONTROL 6. DRAFTS TOTAL FIBERS >5u (Blank) (Concentration) >10u 7. REMARKS ANALYSIS:. TLV:. SAMPLED BY . _F/cc .F/cc | 14 TOT.. AV. . 15 ASARCO ELP 0003617 BIBLIOGRAPHY ON MEMBRANE FILTER METHOD 1. Edwards, G. H. and J. R. Lynch: The U. S. Public Health Service Method for Membrane Filter Enumeration of Asbestos Dust, Unpub lished, 1966. .2 Ayer, E. A. and J. R. Lynch: Measurement of Dust Exposures in the Asbestos Textile Industry. American Industrial Hygiene Association, Journal 27, September -- October 1966. 3. Ayer, H. E,, G. H. Edwards, J. J. Fanney, Jr., and J. R. Lynch: Relation ship of Impinger Counts to Fiber Concentrations by Membrane Filter in Asbestos Textile Plants. Delivered at the annual meeting of the Ameri can Industrial Hygiene Association, Houston, Texas, 1965. 4. Bayer, S. G., T. A. Brown, and R. D. Zumwalde: Equipment and Pro cedures for Mounting Millipore Filters and Counting Asbestos Fibers by Phase Contrast Microscopy. H.E.W. Public Health Service, February, 1969. 5. Transactions of the Thirtieth Annual Meeting of the American Con ference of Governmental Industrial Hygienists. Subcommittee on Threshold Limit Values, St. Louis, Mo., 196S. 6. Weidner, R. B.: Personal Respirable Mass Sampling Procedure, H. E. W. Occupational Health Program, 1968. 7. Technical Note No. 1, Measurement or Airborne Asbestos Dust by the Membrane Filter Method, Asbestos Research Council, England, 1969. 8. Technical Data Note No. 13, Standards for Asbestos Dust Concentration for Use with Asbestos Regulations, Her Majesty's Stationary Office, England, 1969. 9. Hygiene Standards for Chrysotile Asbestos Dust, Committee on Hygiene Standards of -the British Occupational Hygiene Society. Published in Ann. Occupational Hygiene Volume II, 1968. 16 J ASARCO ELP 000361