Document 6wJKLwaLeeZjzd6yMnoGGRz8R

TEST FOR SCREENING ASBESTOS Walter'S. Kim James W. Carter, IT Richard E. Kupel U.S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE Public Health Service Center for Disease Control National Institute for Occupational Safety and Health Division of Physical Sciences and Engineering Cincinnati, Ohio 45226 October 1979 ApC 003327 DHEW (NIOSH) Publication No. 80-110 r. TEST FOR SCREENING ASBESTOS I. SCOPE AND APPLICATION This colorimetric test is applicable to the detection of magnesium (II) and iron (II) from asbestos in bulk samples. These samples Include sprayed on asbestos as well as ceiling tiles. The test is simple and can be readily used in the field to screen for the presence or absence of asbestos. The amount of the sample needed for the test is only about the size of a large pea. II. PRINCIPLE The is based upon the formation of j^glor complexes with Mg+2 and Fe released from asbestos. The Mg ^from chrysotile is completed with p-nitrophenylazo-a-naphthol. The Fe from crocidolite and anosite is completed with 1, lO-phenanthroline.^^ positive+Jest is indicated by the formation of colored complex for Mg and/or Fe , and it indicates possible presence of asbestos. III. INTERFERENCES The test is a colorimetric spot test for Mg+2 and Fe+2 , and is not specific for asbestos. A bulk sample may contain Mg and Fe compounds other than asbestos. Without treating the sample as in the Procedure, a few drops of color forming reagents are added directly to the sample. If either color forms, an interferring substance is present and the sample must be cleaned before the test is conducted to eliminate the interference. In this cleaning process, plaster, mineral wool, fiberglass, and soluble Mg and Fe compounds are removed before the screening test, preventing their interference. IV. SENSITIVITY, PRECISION, AND ACCURACY A sample containing more than 1% asbestos gives a positive color reaction. A total of 198 various field samples were tested before the Acid Wash steps were added to the Iron Test procedure. Results are listed be low: Results of the screening test without the Acid Wash. -y. No. of Samples 7. of Total True Positive 79 /.o False Positive 50 25- True * . . *. i... 69 35 False ----- 0 * j0~ ' ' ApO 003329 With the Acid Wash, the following results were obtained from 13 samples. Results of the screening test with the Acid Wash. No. of Samples % of Total True Positive 5 38 False Positive 0 0 True Negative 8 62 False Negative 0 0 V. APPARATUS 1. Teflon dish or white plastic plate 2. Plastic or glass rod 3. Dropping plastic pipet 4. 15 mL disposable plastic beaker 5. 25 mm size 0.8 pm mixed cellulose ester filter 6. 25 mm size polyvinyl chloride filter 7. 25 mm Swinnex filter holder and gasket 8. 10 mL disposable plastic syringe VI. REAGENTS (Reagent Grade) 1. Phosphoric acid, concentrated. 2. 10 N sodium hydroxide - Dissolve 40 g of NaOH in 100 mL of water. 3. Mg Reagent - Dissolve 1 mg of p-nitrophenylazo-a-naphthol in 100 mL of 2 N NaOH. Age at least a day. This reagent is stable . over a month. 4. Hydrofluoric acid - Dilute 20 mL of HF with 20 mL of water. Add 0.6 mL of concentrated HC1. 5. Fe Reagent - Dissolve 2 g of 1,10-phenanthroline in 50 mL of ethanol. This reagent is stable over a month. 6. Glycerin, reagent grade. 7. Acetic acid, concentrated glacial. 8. Sulfuric acid, concentrated. 9. Double de-ionizcd water. Apc 003330 VII. PROCEDURE A. Magnesium Test 1. Add a few drops of Mg Reagent directly to the sample. If blue color appears, wash the sample with glycerin before the test. Any sample containing plaster is also washed with glycerin. Glycerin Wash a. Place a small portion of sample, about the size of a large pea, in a plastic beaker. b. Add 5 drops of glycerin and mix well with a plastic rod or spatula. c. Rinse the plastic rod with a small amount of water into the beaker. d. Filter the sample through the filtration assembly consist ing of a syringe attached to the Swinnex filter holder loaded with a mixed cellulose ester filter and a gasket. e. Filter with a minimum of 5 washings or about 50 ml. of water. f. Transfer the filter to a Teflon dish for the Magnesium test. 2. Add a drop of H^PO^ and mix well by grinding the sample with a plastic rod. _* 3. Add 2 drops of 10 N NaOH and mix well. 4. Add 5 drops of Mg Reagent and stir briefly. Note any color change. 5. Add 5 more drops of Mg Reagent and observe the final color. 6. A blue color indicates that chrysotile may be present. 7. Samples giving a positive test may be sent to a laboratory for confirmation. If the magnesium test is negative, the sample must be tested for iron. B. Iron Test 1, Add fev drop? Pe Reagent directly to the sample. If a red color appears, wash the sample with the acetic--sulfuric acid mixture before the test. Samples containing fiberglass or mineral wool are also washed with the acid mixtur.o. *PC 003331 %' ; I;,-. Add Wash 1. Place a small portion of the sample, about the size of 'a large pea,ft|n a plastic'beaker.'^. 2. Add 5 drops of concentrated acetic'add^ * 3. . Add 5 drops of concentrated sulfuric acid. Mix veil and ultrasonicate if available for 5 minutes. ' 5. Filter,, the sample through a polyvinyl chloride filter with a minimum of 5 washings or about 50 mL of water. 6. Transfer the filter to a Teflon dish and proceed with the Iron Test; 2. Add a drop of HF. solution and mix well. 3. Add 5 drops of Fe Reagent and observe the development of red 'Color. , v . ' * 4. The red color indicates that amoslte or crocldollte may be present. ,* - Notes S ,-T ; VIII. If both parts of the test give negative responses, there is a low probability that any asbestos' is present. Once the presence of mag nesium and/or iron is indicated, further analysis, if needed, is done in the laboratory to confirm, identify, the type,, and quantitate the percentage of asbestos. ' .v*v.-V REFERENCE i ' ;..lf V 1. Caution: Asbestos Dust. ;;A scriptographic booklet by Channlng L. Bete Co., Inc., Greenfield, Mass. Prepared in'cooperation with U.S. DHEtf, PBS, CDC, National*Institute for Occupational Safety and Health, Cincinnati, Ohio (1973). ' 2. Frit;: Feigl: Spot'Tests - Ini Inorganic Analysis. Translated by Ralph E. Oesper. Sth Edition? Elsevier Publishing Company, Amsterdam. (1958) p. 225-227; 3. Walter S. Kim, James W. Carter, II, and Richard E. Kupel: Quick Screening Test for Asbestos. U.Sv- DREW, PBS, CDC, NIOSH, Cincinnati, Ohio. To be published in AIHAJ. v;;' ,' APC 000332 Memorandum .1980-09-09 P^.ge Two Distribution: Alcoa Technical Center Environmental Health Laboratory Staff J. R. Stemler/J. Damiano, ATC-C R. Rolles/G. F. Lena, ATC-C Pittsburgh Office E. E. Rumberger T. B. Bonney C. Dixon R. W. Flanagan R. M. James P. H. Scott B. Siceloff M. J. Vaudreuil Plants and Subsidaries 0. E. Wilkinson/D. E. Huddleston, ACW R. C. Hinkle/E. M. Morgan, Badln N. Kloap, Bauxite L. L. Grubb, Cleveland R. Allen/J. V. Muncie, Corona K. W. Williams, Davenport W. W. Williams, Fort Mead W. D. Coker/J. B. Dolan, Lafayette L. M. Crivaro, Lancaster R. Andrew, Lebanon W. D. Helmick, Logans Ferry R. K. Morrow/G. D. Hicks, Massena W. J. Boutreis/R. V. Newsome, Mobile R. E. Podhora, Point Comfort J. L. Eicher/J. D. Gibbs, Richmond E. B. Parker/A. G. Clayton, Rockdale W. S. Stroud/J. C. Vergho, Tennessee J. A. Blessinger/L. L. Haisch, Vancouver A." B. Piecka, Vernon R. L. Parsons/K. P. Karsten, Warrick J. A. Thompson/H. F. ^illegass, Wenatchee T. V. Byerly, Marshall J. E. Stitt/J. Branch, Alcas Cutlery L. M. Altieri, American Powdered Metals H. W. McLaughlin, Buckeye Molding G. R. Hartnett, H. C. Products W. V. Kochanski, Lincoln Mfg. Co. T. A. Shdby/S. Huey, P.ce Magnet Wire M. M. Utz, Stolle Corp. H. E. Chandler,. Tifton Aluminum R. A. Williams, Wear-Ever Aluminum Foreign Locations E. D. Silva, Pocos De Caldas J. H. J. Erkins, Point Henry B. Chesson, Kuinana M. R. Borjas, Veracruz M. LeRoy, Pinjarra V. A. Correia, Suriname APC 003333 (KJlt)^(' TR N A. LEIDEL / USPHS/NIOSH MEMBRANE FILTER METHOD FOR EVALUATING AIRBORNE ASBESTOS FIBERS I SCOPE A This method describes the equipment and procedures for collecting, mounting, sizing, and counting asbestos fibers on membrane filters in the evaluation of breathing zone samples of airborne asbestos fibers. B The method has been successfully applied using 37 mm Millipore AA filters and small battery operated personal sampling pumps at a flow rate of 1.0 to 2. S liters per minute for time periods of 15 to ISO minutes at concentrations of 1 to 20 fibers (longer than 5 micrometers)/cubic centimeter. Large deviations from these conditions may result in filters with either too few or too many fibers, which will yield air concentration estimates of low statisticsl precision and accuracy, C This method considers only fibers with a length to width ratio of 3 to 1 or greater and a length greater than 5 micrometers. II SUMMARY OF METHOD A The sample is collected by drawing air through a membrane filter by means of a battery powered personal sampling pump. The filter is transformed from an opaque solid membrane to a trans parent, optically homogeneous gel. The fibers are sized and counted by phase-contrast microscope at 400-450X magnification. Ill SIGNIFICANCE / A This method was first used by the Asbestosis Research Council in Great Britain**) and later was slightly modi fied by the U. S. Public Health Service for asbestos dust studies in the United States*2). It has been specified as the . method of test*3) for the Federal Standard Prepared by Nelson A. Leidel, Stephen G. Bayer, and Ralph D. Zumwalde, NIOSH, 11/73. for asbestos in industrial air (29 C.F. R. Part 1910. 93a), in the U.S. Public Health Service Criteria Document on occupational exposure to asbestos**), and in sampling procedures of the Occupa tional Safety and Health Administration, Department of Labor* 5) IV DEFINITIONS A For definitions of terms used in this method, refer to ASTM Definitions D 1356, Terms Relating to Atmospheric Sampling and Analysis. V INTERFERENCES All particulates with a length to width ratio of 3 to 1 or greater and a length greater than 5 micrometers should, in the absence of other information, be considered to be asbestos fibers and counted as such. VI APPARATUS A Sampling Equipment The personal sampling equipmem train consists of l) personal sampling pump, 2) tubing, 3) clothing spring clip, 4) tubing-to-field monitor metal adaptor, and 5) field monitor (collecting filter and holder). 1 sampler pump. The pump must be battery powered and weigh leas than 2 pounds (0.91 ktf. The pump must be capable of sampling at 1.0 to 2.5 1pm against a flow resis tance of 7.6 inches H2O (1.4 cm Hg) for 8 continuous hours on a fully charged battery. See Note A for sources of pumps that have been found satisfactory for this method. 2 Tubina. Laboratory tubing such as rubber or plastic with 6 mm bore (1/4 inch) and about 90 cm length (3 feet). APC 003334 USPHS/NIOSH Membrarts Filter Method t 3 nothing serine elln. Thie clip attaches the rubber tubing to the lapel or ahlrt of the individual being moni tored. See Note B for the eource of a clip that has been found satisfactory - for this method. Large apring paper clips will also work. 4 Tubins-to-field monitor adaptor. See See Note C for a source of an adaptor that has been found satisfactory. 5 Field monitor (collecting filter and holder!. The only field monitor currently approved by the National Institute for Occupational Safety and Health is manufactured by the Millipore Corporation. The unit consists of: l) A three-section styrene plastic case designated Milllpore Aerosol Monitor Case. 2) a 37 mm diameter plain white cellulose ester membrane filter designated Milllpore AA (nominal pore size of 0.8 micro meter) , 3) a support pad. and 4) two plastic sealing caps. If a large num ber of samples are to be taken, it will be leas expensive to reuse the plastic cases. Great cars must be taken in the cleaning and reassembly process. The outside mating surfaces of the field monitors should be covered with "shrink-fit" sealing bands to seal the units and provide a writing surface for filter identification. See Notes D and E. B Optical Equipment For general guidance on microscopes consult Needham(*) and Clark'7' under phase contrast microscopes and accessories. 1 Microscope body with binocular head. 2 10X Huygenian eyepieces are recom mended. Other eyepieces can be substituted if necessary.3 * * 3 Koehler illumination (preferably built in and having provisions for adjusting light intensity). 4 A Porton reticle is recommended. Others such as the Patterson Globe and Circle can be substituted, if necessary. 5 Mechanical stage. 6 Abbe or Zeralke condenser fitted with phase ring (or Heine) with a numerical aperture (N. A.) equal to or greater than the N. A. of the objective. 7 40-45X (N. A. 0. 65 to 0. 75) positive phase contrast achromatic objective. 8 Phase-ring centering telescope or Bertrand lens. B Green filter, if recommended by microscope manufacturer. 10 Stage micrometer with 0.01 mm subdivisions. C Filter Mounting Equipment Experience has shown that certain equip ment is useful for efficient sample mourn ing. The following items are recommended for extracting and mourning a portlon'of' the filter onto the microscope. 1 Microscope slides: 2.5 by 7.5 cm (oos inch by three inches) glass slides are most commonly used. Sample number, data, initials, etc., can be conveniently written on a frosted end slide. 2 Cover slips: Cover slips are a neces sary part of the slide mount and optical system. The shape should be appro priate for the else of the filter wedge. The appropriate cover slip depends upon this objective to be used. Ordi narily objectives are optically cor rected for a 11 1/2 (0.17 millimeter) thickness cover slip. Improper cover glass thickness will detract from the final image quality. 3 Scalpel: A scalpel is needed to re move a portion of the filter to be 2 APC 003335 USPHS/NIOSH Membrane Filter Method examined. A number-ten curved blade scalpel works very well. 4 Tweeters: A pair of fine-tipped tweeters is used to remove the membrane filter slice from the field monitor and place it upon the slide. 5 Lens tissue: To insure cleanliness, use of a lint-free lens tissue is recommended. This tissue should also be used for wiping mounting tools and for cleaning slides and cover* slips. 6 Glass rod or spatula; A spatula or fire-polished glass rod is needed to spread the mounting solution on the slide. 7 Wheaton Balsam bottle: This special glass container has a glass top which prevents contamination of the mounting solution. A glass rod is included for dispensing the solution. VH REAGENTS Chemicals should be reagent grade, free from particles and color, conforming to the specifications of the Committee on Analytical Reagents of the American Chem ical Society, where such specifications are available. A Dimethyl Phthalate B Diethyl Oxalate Vm SAFETY PRECAUTIONS A Avoid getting the mounting solution on the skin. Wash skin with soap and water if contact, occurs. DC SAMPLING A General Information Refer to the Recommended Practice D 1357, for Planning the Sampling of the' Atmosphere and Recommended Practice D 2009, for Collecting by Filtration and Determination of Mass, Number, and Optical Sizing of Atmospheric Particu lates. These guides are cited only for general principles, as they are intended primarily for air pollution measurements at fixed sampling stations. B Calibration The personal sampling pump should be recharged prior to calibration and then calibrated^) against a bubble meter, wet test meter, spirometer, or similar device at 1.0 to 2.5 1pm. The sampling train used in the calibration (pump, hose, filter) should be the same as the one used in the field. The calibration should be of sufficient accuracy that the 98% con fidence limits on the flowrate are 10% (two standard deviations). C Mounting the Sampler Fasten the sampling pump to the worker' belt and fasten the field monitor to the lapel or shirt front (as close to the face as is practical). Remove the cover of the plastic monitor making certain the exposed filter is facing downward. Turn on the pump and adjust to the previously calibrated flowrate (1.0 to 2.5 1pm). Immediately record the following informa tion in a logbook: 1 Filter number 2 Pump start time and date 3 Flow rate 4 Subject's name 5 Tjrpe of operation 6 Ventilation controls and/or if worker is wearing a respirator approved for asbestos. The pump should be checked periodically during the sampling period for proper operation and flowrate. D Optimum Sampling Times LeidelO) has described the requirements for optimum sampling times for airborne 3 APC 003336 1'SI`HS/NIOSH Membrane Filter Method iislx-sto* fiber*. A nomogram to aid in Ihe calculation of these times is shown as Figure 1. For typical microscope field areas and pump flow rates the optimum collection times are about 50 to AO minutes. The nomogram is in tended as a guide to be used where no prior knowledge of the air concentration in uvoilable. If, after sampling for the time* recommended by Figure 1, the sample is very heavily loaded (greater than 10 fibers/field), then the air con centration probably greatly exceeded ihe ceiling standard of JO flbers/cm3. Conversely if the filter fiber density is very low (less than 1 fiber/field) then the air concentration probably was less than the 1976 TWA Standard of 2 fiher*/cm3. The nomogram gives the the sampling times which produce optimum fiber densities on the filter (1 to 5 fibers/field) for air concentrations >f 1 to 10 fibers/cm^. If the air concentrations are very high or verv low, then graphs given by l.eidc|i9) would aid in the calculation of the proper sampling times. If there is ; dense visible cloud, short (5-IS min utes) sampling times should probably be used. To sample for the ceiling standard of jo fibers/cm3, a 15-minute period should be used. I-: Knd of Sampling Period Remove the field monitor, replace the plastic top cover and the small end caps, and store the monitor. Always shut off the pump when changing monitors to avoid i.'ontnminating or damaging the pump. Record the pump ahutoff time in the logbook. F Blanks With each batch (25 to SO filters) of samples submit two unopened filters which have been subjected to the same handling as the samples except that no air has been drawn through them. Label these as blanks. If the blanks yield fiber counts greater than about 5 fibers/ 100 fields, then the entire sampling procedure should be examined carefully for the cause of contamination. G Shipping The field monitors in which the samplers are collected should be shipped in a rigid container with sufficient pocking material to prevent crushing. H Numbers of Samples When sampling for the ceiling standard only one sample (15-minute minimum duration) is theoretically necessary. How ever, several 15-minute samples should be taken during expected periods of peak air concentrations to allow for detection of grose sampling or counting errors. When sampling for determination of noncompliance with the 8-hour TWA Standard one should continuously sample as large a portion of the work day as is feasible. Normally this would mean 6 to 10 con secutive samples on the same man. How ever, if this is not feasible the 8-hour TWA air concentration can be estimated from fewer than 6-10 samples. Leidel and BuschdO) have shown an optimum number would be 4 to 7. Refer to (10) for treatment of the data for the determination on noncompliance. See Jonee and BrieftU) for how to treat data taken for an environ mental monitoring program. X CALIBRATION AND STANDARDIZATION A Porton Reticle The asbostoe fiber count procedure con sists of comparing fiber length by com parison with calibrated circles, and counting all fibers greater than 5 micro meters in length within a given counting field area. It is recommended that a Porton reticle be used for this purpose. The Porton reticle is a glass plate in scribed with a series of circles and rectangles. The square on the left, divided into six rectangles, is defined as the counting field. APC 003337 USPHS/NIUSH Membrane Filter Method B Placement in Eyepiece The Porton reticle is placed inside the Huygenian eyepiece where it rests on the field-limiting disphragm. The reticle should be kept clean, since dirt on the reticle is in focus and will com plicate the counting and sizing process. For mounting in other eyepieces such as a Ramsden, a counting collar must be used. C Stage Miorometer The Porton reticle cannot be used for counting until it has been properly calibrated with a stage micrometer. Most stage micrometer scales are approximately two millimeters long and are divided into units of one-hundredth of a millimeter or ten micrometers. O Microscope Adjustment Follow the manufacturer's instructions while observing the following guidelines. 1 The light source image must be in focus and centered on the condenser iris or annular diaphragm. With a 10X objective in place, place the stage micrometer on the mechanical stage, focus, and center the image. Change to the 40-45X objective and adjust the first scale division tn coincide with the left boundary of the Porton rectangle. Count the number of divisions between the left and right boundaries of the long horizontal dimension of the largest rectangle, e stimating any portion of the final division. This measurement repre sents 200 L units and one divides the measurement by 200 to find "L". The large rectangle is 100 L units long on the short vertical dimension. The calculated "L" is inserted into the formula D * L (2^)1 where "N" is the circle number (indicated on the reticle) and "D" is the circle diameter. Since the circle diameters vary logarithmically, every other circle doubles in diameter. For example, number three is twice the diameter of number one; number four is twice the diameter of number two. When the circle sizes have been determined, the counting field area consisting of the left six smaller rectangles can be calcu lated from the relation 10,000 L2. This completes the reticle calibration for this specific objective - eyepiece - recticle combination. 2 The object for examination must be in focus. XI PROCEDURE 3 The illuminator field iris must be A Mounting in focus, centered on the sample, and opened only to the point where the field of view ia illuminated. A very important part of the sample eval uation is the mounting process. This process involves a special mounting 4 The phase rings (annular diaphragm and phase-shifting elements) must be concentric. medium of prescribed viscosity. The mixture must be stirred periodically until the filters have dissolved and a homogeneous mixture is formed. The normal shelf life of the mounting solution E Porton Reticle Calibration Procedure is about six months. Twenty milliliters of mounting solution will prepare approxi Each eyepiece-objective-reticle combina mately 300 samples. tion on the microscope must be calibrated. Should any of the three be changed (dis B Sample Mounting assembly, replacement, zoom adjustment, etc.) the combination must be re-calibrated. Calibration may change if interpupillary distance is changed. For proper calibra tion, the following procedure should be followed closely. Cleanliness is important! A dirty work ing area may result in sample contamina tion and erroneous counts. The following steps should be followed when mourning a sample. 5 APC 003338 i fSPHS/NIOSH Membrane Filter Method 1 Clean the alldee end cover Blips with lens tissue. Lay the slide down on a clean surface with the frosted end up. It is a good practice to rest one edge of the cover slip on the slide and the other edge on the working surface. By doing this, you keep the bottom surface (the one which contacts the filter) from becoming contaminated. B Label the slide with the sample num ber and current date before proceed ing to the next filter. 9 The sample should become transparent after about fifteen minutes. If the filter appears cloudy, it may be nec essary to press very lightly on the cover slip. This is rarely necessary. 2 Wipe all the mounting tools clean with lens tissue and place them on a clean surface <i.e., lens tissue). When mounting a series of filters the scalpel should be wiped clean before cutting each sample. 3 Using a glass rod which is supplied with the Wheaton balsam bottom, apply a small drop of mounting solu tion onto the center of the slide. It may be necessary to adjust the quanti ty of solution used or the site of the wedge. The correct amount will re sult in the solution extending only slightly beyond the filter boundary. If the quantity is greater than this, adverse particle migration will occur. 4 With the spatula or a supplemental glass rod, spread the mounting media into a triangular shape. The size at this triangle should coincide with the dimension at the filter wedge. 3 Separate the middle and bottom sec tions of the field monitor case to ex pose the fragile filter. Cut a triangu lar wedge from the center to the edge of the filter using the scalpel. The size of the wedge should approximate one-eighth at the filter surface. 10 Discard the sample mount after three days if it has not been counted. Crys tals which appear similar to asbestos fibers may begin to grow at the mount ing media/air interfaces. They sel dom present any problems if the slide is examined before three days. In any case, stay away from the filter's edges when counting and sizing. C Counting and Sizing i Pjpding toapccttag anting JiddaPlace the slide on the mechanical stage and position the center of the wedge under the objective lens and focus upon the sample. Nearly all of the particulates (particles and fibers) will be found in the upper ten to fifteen micrometers of the filter surface. When counting and sizing, continual use of the fine focus control is required to insure that nothing is missed. Start counting from one end of the wedge and progress along a radial line to the other end (count in either direction from circumference to wedge tip). Random fields are selected, without looking into the eyepieces, by slightly advancing the slide in one direction with the mechanical stage control. 6 Grasp the filter wedge with the tweezers in the outer area of the filter which D Achieving Comparable Results was damped between the monitor case sections. Do not touch the filter with your fingers. Place the wedge, sampled 1 Size only fibers with a length to width ratio greater than or equal to 3:1. side up, upon the mounting medium. 2 Count only fibers greater than 6 micro 7 Pick up the cover slip with the tweezers and carefully place it on the filter wedge. Once this contact has been made, -do not reposition the cover alio. meters in length. (Be as accurate as possible in accepting or rejecting fibers near this length). Measure curved fibers along the curve to estimate the total length. APC 003339 USPHS/NIOSH Membrane Filter Method 3 Count as many fields at necessary to yield a total count of at least 100 fibers. Exceptions: a) count at least 20 fields even if you count more than 100 fibers and b) stop at 100 fields even if you haven't reached 100 fibers. 4 Select the field of view without look* ing through the microscope's eye pieces to eliminate unconsciously selecting "heavy" or "light" areas. Reject and do not count all other fibers. Refer to Figures 2 through 7. XU CALCULATIONS A Calculation of Airborne Concentration Asbestos fiber airborne concentration may be calculated from the following formula: c . (F - B)(W) ** (A)(V) 5 The fields are selected along the entire length of a radial line running between the outside perimeter and the tip of the wedge. Where: C * Airborne fiber concentration in fibers >5 Mm/cm3 6 When an agglomerate (mass of mate rial) covers a significant portion of the field of view (approx. 1/6 or greater) reject the field and select another. (Do not Include it in the number of fields counted). However, report the fact as it may have mean ing to sampling or medical personnel. F Average fiber count in fibers >5 Mm/field. B Average fiber count of blank(s) or control filteds) in fibers >5 Mm/ field. (It is subtracted to elimi nate the error or background con tamination). 7 Bundles of fibers are counted as one fiber unless both ends of a fiber crossing another can be clearly re solved. 8 For fibers that eroas either one or two sides of the counting field, the following procedure is used to ob- tain a representative count. First, arbitrarily select a) the left and bottom sides and b) the upper and lower left corners or vertical di rection as "decision aids." Then count any fiber greeter than 6 micrometers in length, but only If the fiber: a lies entirely within the counting area or, b crosses the left or bottom sides, or c crosses the upper or lower left corners, or d crosses both the top and bottom sides. W* 8S5 mm2 for 37 mm diameter filter (the portion of the Millipore filter which is exposed when mourned in the field monitor case, i.e., the effective filter area). A * The area of the counting field of a calibrated reticle expressed in mm2 /field. V Total air volume collected through filter expressed in milliliters. Xm PRECISION AND ACCURACY A An accuracy and precision study of the membrane filter counting procedure for asbestos has been conducted by Conway and Holland. (l2) They conducted an intra laboratory study involving six counters. Three of the counters were experienced while the other three had only a short familiarisation with the rules for fiber counting. The conclusions of the study included: 1 The precision of the procedure for filters not containing an abundance of 7 AFC 003340 USPHS/NIOSH Membrane Filter Method fine fibers can be estimated by a standard deviation of 16. 2%. This value includes variation among counters and observed interaction effects. 2 The accuracy of the procedure for similar filters may be estimated for a 100-fiber count by a standard deviation of 21.4%. This assumes that the contribution of the overall variance from the nonuniform fiber distribution is additive. 3 The fiber concentration varies significantly between angular sectors on a given filter. Where approximately 100 fibers are counted, the standard deviation of the fiber count distribution for the whole filter appears to be represented by 1.6 * (n)I, rather than (n)I which is a property of the Poisson distribu tion, where (n) is the total number of fibers counted. 4 A high percentage of very fine fibers on the niter esn significantly affect the standard deviations and confi dence limits for counts by different counters. After combining variations in fiber concentrations over the entire filter with those for different counters it was concluded: a For filters with a low concentra tion of fine fibers, the standard deviation is estimated at 21% and the 95% confidence Interval is + 43%. b For filters with a high concentra tion of fine fibers, the standard deviation is estimated at 25% and the 95% confidence interval la 50%. B Lynch, Kronoveter, and Leidel*1 have also reported on the precision of the method. Their intralaboratory study utilized the data from a large number of dust counts made by different methods by experienced counters over a period of years in an epidemiologic study of the asbestos products industry. They concluded that the standard deviation of counts of fibers longer than 5 micrometers on membrane filters could be estimated from the relation (n)*59i. Thus for counts of about 100 fibers, the stan dard deviation could be estimated at about 15. 2% and the 95% confidence limits at + 30.4%. These values are lower than the precision values reported by Conway and Holland. ^2) REFERENCES 1 Asbestos Research Council: "The Measurement of Airborne Asbestos Dust by the Membrane Filter Method: Technical Note," Dr. S. Holmes (Secretary) P.O. Box 40, Rockdale Lancashire, Great Britain (1969). 2 Edwards, G. H. , and J. R. Lynch: "The Method Used by the U. S. Public Health Service for Enumeration of Asbestos Dust on Membrane Filtersr" Annals of Occupational Hygiene. 11, 1-6 (1968). 3 Federal Register. 37. 22142-22144 (18 Oct. 1972). 4 U.S. Department of Health, Education, and Welfare, Public Health Service, National Institute for Occupational Safety and Health: "Criteria for a Recommended Standard-Occupational Exposure to Asbestos," HSM-72-10267 (1972). 5 U.S. Department of Labor, Occupational Safety and Health Administration, "OSHA Sampling Data Sheet No. 2-Asbestos," (Unpublished - Jan. 1972). 6 Needham, G. H.: "The Practical Use of the Microscope," Charles C. Thomas Publishing Corp. Springfield, Illinois (1958). 7 Clark, G. L.: "The Encyclopedia of Microscopy," Rheinhold Publishing Corp. N.Y. (1981). 8 American Conference of Governmental Industrial Hygienists: "Air Sampling Instruments for Evaluation of Atmospheric 8 APC 003341 USPHS/NIOSH Membrane Filter Method Contaminants," Fourth Edition, Section K, Air Movers and Samplers, pp K-26K-31. P.O. Box 1937, Cincinnati. Ohio (1972). 9 Leidel, N. A.: "Optimum Sampling Times for Airborne Asbestos Fibers," USPHS. NIOSH TR-82, (1972). 10 Leidel, N. A., and K. A. Busch: "Statistical Methods for the Determina tion of Noncompliance with Occupational Health Standards." USPHS. NIOSH TR-76, (To be published 1973). 11 Jones, A. R., and R. S. Brief: "Eval uating Bensene Exposures," A1HA J. 22. 610-613 (1971). 12 Conway, R. E., and Holland, W. D.: "Statistical Evaluation of the Procedure for Counting Asbestos Fibers on Mem brane Filters," LFE Corporation Richmond, CA. Prepared for Asbestos Information Assoc/North America, New York. N.Y. (1973). 13 Lynch, J. Ri, K. J. Kronoveter, and N. A. Leidel: "Validity of the Poisson Distribution in Dust Counting," USPHS, NIOSH, TR-83, (To be published 1973). ACKNOWLEDGEMENTS: The authors gratefully acknowledge the suggestions and assistance of the following indivlduale: Philip J. Bierbaum, George A. Carson, R. Earle Conway, John M. Dement, Lorice Ede, Harry Ettinger, Geoff Knight, William H. Krebs, Kay Kumler, Jeremiah R. Lynch, Robert Magor, and Milton Sheinbaum. Special thanks are due John F. Vining, HI for assembling the initial version of this report. Finally very special thanks are due Myra D. Brooks, Mary K. Geimeler, and Pauline j. Elliott for typing the many versions of this report. NOTES A Sources Of personal sampler Pumas 1 Mine Safety Appliance Company 201 North Braddock Avenue Pittsburgh, PA 15208 2 National Environmental Instruments, Inc. P.O. Box 590 Warwick, RI 02888 3 Willson Products Division P. O. Box 622 Reading, PA 19603 b Sours? 9f clvthing gprlng.sltp Catalog number 1140 John F. McGuire Company 120 Bacon Street Pawtucket. RI 02860 C Source of tubins-to-field monitor adaptor Catalog number LH/L Beetion, Dickinson, A Company Rutherford. NJ D Source of field monitor 1 Complete monitor (plastic case, filter, pad, and caps), catalog number MAWP 037AO (50/box). 2 Filters and pads only, catalog number AAWP 03700 (100/box). 3 Monitors only, catalog number M0000 37AO (50/box), from the Milllpore Corporation Ashby Road Bedford, MA 01730 E Source of sealing bands Cellulose bands, white, opaque, 41 X 25, #26 (minimum order 2500) Walter H. Jelly k Company 2822 Birch Street Franklin Park, IL 60131 9 APC 003342 USPHS/NIOSH Membrane Filter Method 4 zuui * V3UV (T13U 3dOOSOM9IM - V Ii i ll.nll.il?....!... ?.. ............I.ll i . . ............ ... T EXAMPLE > 1.7 1pm 1/ 8 6 e CJ * ii (M % !I 3 hi < tt I I r--j--i" ii i r i m i | "i" f i i r i i i i | i lS 2/ Mimi|w *3WIX SNDdNVS /NMIUrfO 3 o(A .TT| 8 0 1 ito* ! 41 5 r i u i| i i i ' r-- t l i | i M i **T ` 31VW MOId dNTM- Ud i --i ; o 10 APC 003343 Evaluating Airborne Ambcto nwi O OO o O OO >4 H n i i" ' i i Figure'2. COURT, fiber erouti both top od bottoe aides. i 4 t % O OO oO OO *. ___ Figure 3. COURT as one fiber. Figure 4. COURT, fiber crosses left side. nn t i i t t * oooOOOO O Figure 9. COURT, fiber crosses bottoa side. ti 4 t a t t ooOOOOO -ns s n il Flgurdsp. COURT, fiber crosses loser left corner. Figure 7. COURT, fiber crosses upper left corner. AFC 003344 APC 003346 \ -tv IlM? 6 0 |oo*4to&'.$r \b - ^'OH, i S-l-K ***X ^ f * I,7/( 100 b *wlb 0?C -wf *#f M * Tsvy I I.valuanmi Airbomt Asbestos thisl APC 003347 Part No. T113, Model BC Personal Air Sampler complete with pump, rechargable battery, and sampling head (Including cyclone and pre-welghcd cassette $*>13.00 Part No. T16124, Battery Charger with charging leads for above $ 50.00 Part No. T121, pre-welghed cassettes, 10 cassettes/package $ 13.00 Willson Products Division, ESB Inc. P. 0. Box 62? Reading, Pa. 19603 Mllllpore Field Monitors, Cat.No. MAWP 037 A0, 50/carton Mllllpore field monitor refills, Cat.No. AAWP 037 00, 100/box Forceps Mllllpore Corporation Bedford, Mass. 01730 Dispensing Buret, 1000 ml or 2000 ml (any chemical supply house) Diethyl Oxalate (Kthyl Oxalate) Dimethyl Phthalate (Methyl Phthalate) (any chemical supply house) $ 30.00 1 s.. APC 003348 1) N51MP Series 50 Phase Teaching Microscope wit^i 4x scanning n objective, lOx phase 45x phase object Ives jxjjuias k 2) Case lor above, Cat.No. A01650 (optional) 3) Spare bulb, Cat.No. A0611 4) Burrell Cat.No. 58-492, AO-400 microscope stage micrometer, 2 ami scale in 200 parts on 75 x 25 mm slide 5) Huygenian eyepiece lOx, AO-C1142 (must accept 21 mm dia. eyepiece reticle) 6) Part No. 30,084 porton reticle 7) Cat.No. 12-552 microscope slides, 75 x 25 mm, one frosted end 8) Cat.No. 12-52OB micro cover glass, square, size 22 mm sq 9) Lens tissue 10) Luer Slip adapter, Cat.No. LH/L 1/4" I.D. hose connector S448.00 $ 38.00 $ .50 $ 30.00 $ 30.00 $ 17.50 $ 5.40/ gross $ 3.06/ S 1*75 Burrell Corporation 2223 Fifth Avenue Pittsburgh, Pa. 15219 1-2-3-4-5 Edmund Scientific Co. 300 Edscorp Bldg. Barrington, N.J. 08007 6 Fisher Scientific Co. 7-8-9 585 Alpha Drive Pittsburgh, Pa. 15238 (or any chemical supply house) Environmental Compliance Corp. 400 Groentree Rd. Pittsburgh, Pa. 15220 10 APC 003349 ASBESTOS COUNT RECORD SHEET SAMPLE _OPERATION PLOW TIME VOLUME DATE______________________________________ FILTER AREA (mm2) _________ FIELD AREA (mm2) _________ K AV.COUNT CONCENTRATION COMMENTS 0 5 10 15 20- 25' SUB-TOTALS FIBERS/ FIELDS AVRRAOE NET COUNT X E AIR VOLUME SAMPLED (557 FIBERS/al ^003350