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OEFIN11ION: Total aerosol mass NUISANCE DUST. TOTAL M61H00: 0500 ISSUED: 2/15/84 OSHA: 15 mg/m3 N10SH: no standard ACGIH: 10 mg/m*, total dust less than II quartz PROPERTIES: quartz less than II tl] SYNONYMS: boron oxide (CAS #1303-86-2) and nuisance dusts [1] including alunina (CAS #1344-28-1), calcium carbonate (CAS #1317-65-3), cellulose (paper fiber; CAS #9004-34-6), glycerin mist (CAS #56-81-5), limestone (CAS #1317-65-3), etc. SAMPLING_________________________________________ MEASUREMENT________________ I SAMPLER: FILTER (tared 37-mn, 5-pm PVC filter) FLOW RATE: 1.5 to 2 L/min VOL-MIN: 25 L @ 15 mg/m* -MAX: 133 L P 15 mg/m* '.TECHNIQUE: GRAVIMETRIC (FILTER WEIGHT) i iANALYTE: airborne particulate material I !BALANCE: 0.01 mg sensitivity or better; use same ! balance before and after sample ! collection ; SHIPMENT: routine SAMPLE STABILITY: indefinitely BLANKS: 2 field blanks per 10 samples BULK SAMPLE: none required __________________ ACCURACY_____________ ICALIBRATION: National Bureau of Standards ! Class M weights I '.RANGE: 0.3 to 2 mg per sanple I !ESTIMATED LOO: 0.2 mg per sample \ ! PRECIS ION: 0.08 mg per sarrple [3] < I RANGE STUDIED: 8 to 28 mg/m* BIAS: not significant OVERALL PRECISION (sp): 0.056 [2] APPLICABILITY: The working range is 3 to 20 mg/m* for a 100-L air sanple. This method is nonspecific and determines the total dust concentration to which a worker is exposed. It nay be applied, e.g., to gravimetric determination of fibrous glass [4] in addition to the other ACGIH nuisance dusts [1], INTERFERENCES: Organic and volatile particulate matter may be removed by dry ashing [4]. OTHER METHODS: This method is similar to the criteria docunent method for fibrous glass [4] and Method 5000 for carbon black. This method replaces Method S349 [5]. Impingers and direct-reading instnments may be used to collect total dust sanples, but these have limitations for personal sanplinq.______________________________________________________________ 2/15/84 0500-1 NUISANCE DUST. TOTAL HETHOO: 0500 EQUIPMENT: 1. Environmental chamber at constant temperature and tumidity (e.g., 20 *C 0.3 C and 50% + 5% RH). 2. Sampler: 3 7-mm PVC, 2- to 5-pm pore size morbrane or equivalent hydrophobic filter and cellulose supporting pad in 37-nm cassette filter holder. 3. Personal sampling punp, 1.5 to 2 L/min, with flexible connecting tubing. 4. Microbalance, capable of weighing to 0.01 mg. 5. Vacuim desiccator.. 6. Static neutralizer: e.g., Po-210; replace nine months after the production date. SPECIAL PRECAUTIONS: None. PREPARATION OF FILTERS BEFORE SAMPLING: 1. Dry filters and backup pads under vacuim in the vacuim desiccator for at least 15 min. 2. Release the vacuim, remove the desiccator cover and equilibrate the filters in the environmental chamber for at least 1 hr. 3. Number the backup pads with a ballpoint pen and place them, numbered side down, in filter cassette bottom sections. 4. Weigh the filters in the environmental chanter. Record the filter tare weight, Wj (mg). a. Zero the balance before each weighing. b. Handle the filter with forceps (nylon forceps if further analyses will be done). c. Pass the filter over an antistatic radiation source. Repeat this step if filter does not release easily from the forceps or if filter attracts balance pan. Static electricity can cause erroneous weight readings. 5. Place the weighed filters on top of the backup pads in the filter cassette bottom sections and allow to stand an additional 8 to 16 hrs in the environmental chamber. 6. Reweigh the filters. If this tare weight differs by more than 0.01 mg from the first tare weight obtained in step 4 above, discard the filter. NOTE: Insert a rod through the outlet hole of the filter cassette bottom section to raise the backup pad and filter so that the filter can be grasped with forceps. 7. Assemble the filter in the filter cassettes and close firmly so that leakage around the filter will not occur. Place a plug in each opening of the filter cassette. Place a cellulose shrink band around the filter cassette, allow to dry and mark with the same niirber as the backup pad. SAMPLING: 8. Calibrate each personal sampling pimp with a representative sampler in line. 9. Sample at 1.5 to 2 L/min. Do not exceed a total filter loading of approximately 2 mg total dust. SAMPLE PREPARATION: 10. Wipe dust from the external surface of the filter cassette with a moist paper towel to minimize contamination. Discard the paper towel. 11. Remove the top and bottom plugs from the filter cassette. Place the filter cassettes in a vacuum desiccator under vacuim for at least 15 min, followed by equil4bration for at least 1 hr in the environmental chanber. 12. Remove the cassette band, pry open the cassette and remove the filter. Handle the filters very gently by the edge to avoid loss of dust. 2/15/84 0500-2 hi HETHOO: 0500 NUISANCE DUST. TOTAL NOTE: If the filter sticks to the underside of the cassette top, very gently lift away by using the dull side of a scalpel blade. This nust be done carefully or the filter will tear. CALIBRATION AND QUALITY CONTROL: 13. Zero the microbalance before all weighings. Use the same microbalance for weighing filters before and after sample collection. Maintain and calibrate the balance with National Bureau of Standards Class M weights. 14. Take two to four replicate samples for every batch of field sanples for quality assurance on the sampling procedures. The set of replicate sanples should be exposed to the same dust environment, either in a laboratory dust chamber [6] or in the field. , The quality control sanples must be taken with the same equipment, procedures and personnel used in the routine field sanples. The relative standard deviation calculated from these replicates should be recorded on control charts and action taken when the precision is out of control. MEASUREMENT: 15. Weigh each filter, including field blanks. Record this post-sampling weight, W2 (mg), beside its corresponding tare weight. Record anything remarkable about a filter (e.g., overload, leakage, wet, torn, etc.). CALCULATIONS: 16. Calculate the concentration of total nuisance dust, C (mg/m3), in the air volune sampled, V (L): C = B--103. mg/m3 where: W^ = tare weight of filter before sampling (mg) W2 = post-sampling weight of sample-containing filter (mg) B = mean change in field blank filter weights between tare and post-sampling (mg) (+ or -). EVALUATION OF HETHOO: Lab testing with blank filters and generated atmospheres of carbon black was done at 8 to 28 mg/m3 [2,6]. Precision and accuracy data are given on page 0500-1. REFERENCES: [1] TLVs - Threshold Limit Values for 1983-84, Appendix D, ACGIH, Cincinnati, OH (1983). [2] This Manual, Method 5000. [3] Unpublished data from Non-textile Cotton Study, NI0SH/DRDS/EIB. [4] NI0SH Criteria for a Recommended Standard ... Occupational Exposure to Fibrous Glass, U.S. Department of Health. Education, and Welfare, Publ. (NI0SH) 77-152, 119-142 (1977). [5] NI0SH Manual of Analytical Methods, 2nd ed., V. 3, S349, U.S. Department of Health, Education, and Welfare, Publ. (NI0SH) 77-157-C (1977). [6] Documentation of the NI0SH Validation Tests, S262 and S349, U.S. Department of Health, Education, and Welfare, Publ. (NI0SH) 77-185 (1977). METHOO WRITTEN BY: Kathy Horring, Derry Clere, and Frank Hearl, P.E., NIOSH/ORDS. 2/15/84 0500-3 L '" FORMULA: various FIBERS HETHOO: 7400 M.W.: various ISSUED: 2/15/84 _________REVISION #2: 8/15/87 OSHA: 0.2 asbestos fibers (> 5 pm 1ong)/taL [1] PROPERTIES: solid, NIOSH: 0.1 asbestos fNL [1]; 3 glass fibers (>10 ym x <3.5 >an)/mL [3] fibrous ACGIH: 0.2 crocfdolite; 0.5 amosite; 2 chrysotile and other asbestos, f/M. SYNONYMS: actinolite asbestos [CAS #13768-00-8], grunerite asbestos (anoslte) [CAS #12172-73-5], anthophylllte asbestos [CAS #17068-78-9], chrysotile asbestos [CAS #12001-29-5], crocidolite asbestos [CAS #12001-28-4], tremollte asbestos [CAS #14567-73-8]; fibrous glass. SAMPLING________________________________________ MEASUREMENT SAMPLER: FILTER (0.8- to 1.2- um cellulose ester menfcrane, 25-am diameter; conductive cowl on cassette) FLOW RATE**: 0.5 to 16 L/min (see step 4) TECHNIQUE: LIGHT MICROSCOPY, PHASE CONTRAST !ANALYTE: fibers (manual count) SAMPLE PREPARATION: acetone/triacetin "hot block" method [5] VOL-MIN*: 400 L 9 0.1 fiber/mL (see step 4) -MAX*: (see step 4) Adjust for 100 to 1300 fibers/nma (step 4) SHIPMENT: routine (securely packed to reduce shock) SAMPLE STABILITY: Stable COUNTING RULES: Set A (required by OSHA; [1,4]) or Set B (modified CRS [6]) EQUIPMENT: 1. positive phase-contrast microscope 2. Ualton-Beckett graticule (10O~pm field of view): A Rules use Type G-22; B Rules use Type G-24 3. phase-shift test slide (HSE/KPL) FIELD BLANKS: 10% (>2) of sanples CALIBRATION: HSE/NPL test slide ACCURACY RANGE: 100 to 1300 fibers/me2 filter area RANGE STU0IE0: 80 to 100 fibers counted ESTIMATED LOO: 7 fibers/sma filter area BIAS: see EVALUATION OF HETHOO OVERALL PRECISION (sr): 0.115 to 0.13 (A Rules) [3] PRECISION: 0.10 to 0.12 (A Rules) [3] (see Evaluation of Method:B) APPLICABILITY: The method gives an Index of airborne fibers in workplace atmospheres. Phas contrast microscopy will not differentiate between asbestos and other fibers; use this method in conjunction with electron microscopy (e.g.. Method 7402) for positive identification. Fibers < ca. 0.25 tan diameter will not be detected by this method [71. INTERFERENCES: Any other airborne fiber may Interfere since all particles meeting the counting criteria are counted. Chain-like particles may appear fibrous. High levels of non-fibrous dust particles may obscure fibers in the field of view and increase the detection limit. OTHER HETHOOS: This method introduces changes for improved sensitivity and reproducibility. It replaces P&CAH 239 [4.8] and Method 7400. Revision #1 (dated 5/15/85). 8/15/87 7400-1 NIOSH Manual of Analytical Methods : I f r\ r~ , -r -r 1 FIBERS flETHOO: 740ft REAGENTS: EQUIPMENT: 1. Acetone.* 1. Sampler: field monitor, 2S-am, three-piece cassette 2. Triacetin (glycerol triacetate), with ca. SO-nm electrically-conductive extension cowl reagent grade. and cellulose ester filter, 0.8- to 1.2-trt pore size, and backup pad. See SPECIAL PRECAUTIONS. NOTE 1: Analyze representative filters for fiber background before use. Discard the filter lot if mean is > 5 fibers per 100 graticule fields. These are defined as laboratory blanks. NOTE 2: Use an electrically-conductive extension cowl to reduce electrostatic effects. Ground the cowl when possible during sampling. 2. Personal sampling pump, 0.5 to 16 L/min (see step 4 for flow rate), with flexible connecting tubing. 3. Microscope, positive phase contrast, with green or blue filter, 8 to 10X eyepiece, and 40 to 45X phase objective (total magnification ca. 400X); numerical aperture = 0.65 to 0.75. 4. Slides, glass, frosted-end, pre-cleaned, 25 x 75 im. 5. Cover slips, 22 x 22 mn, No. 1-1/2, unless otherwise specified by microscope manufacturer. 6. Lacquer or nail polish. 7. Knife, #10 surgical steel, curved blade. 8. Tweezers. 9. Heated aluninun block for clearing filters on glass slides (see ref. [5] for instructions on manufacture). 10. Micropipets, 5-pL and 100- to 500-pL. 11. Graticule, Walton-8eckett type with 100-tan diameter circular field (area * 0.00785 mn^Iat the specimen plane (Type G-22 for A Rules; Type G-24 for 8 Rules). Available from PTR Optics Ltd., 145 Newton Street, Waltham, MA 02154 [phone (617) 891-6000] and HcCrone Accessories and Components, 850 Pasquinelli Drive, Westmont, IL 60559 [phone (312) 887-7100]. NOTE: The graticule is custam-iude for each microscope. Specify disc diameter needed to fit exactly the ocular of the microscope and the diameter (mn) of the circular counting area (see APPENOIX A). 12. HSE/NPL phase contrast test slide, Mark II. Available from PTR Optics Ltd. (address above). 13. Telescope, ocular phase-ring centering. 14. Stage micrometer (0.01-mn divisions). 15. Wire, multi-stranded, 22-gauge. SPECIAL PRECAUTIONS: Acetone is extremely flamnable. Take precautions not to ignite it. Heating of acetone in volisnes greater than 1 mL must be done in a ventilated laboratory fune hood using a flameless, spark-free heat source. SAMPLING: 1.Calibrate each personal sampling pimp with a representative sampler in line. 8/15/87 7400-2 uf-!i I' f r l Mi N10SH Manual of Analytical Methods FIBERS METHOO: 74 REAGENTS: EQUIPMENT: 1. Acetone,* 1. Sampler: field monitor, 2S-mm, three-piece cassette 2. Triacetin (glycerol triacetate), with ca. 50-mm electrically-conductive extension cowl reagent grade. and cellulose ester filter, 0.8- to 1.2-tia pore size, and backup pad. See SPECIAL PRECAUTIONS. NOTE 1: Analyze representative filters for fiber background before use. Discard the filter lot if mean is > 5 fibers per 100 graticule fields. These are defined as laboratory blank: NOTE 2: Use an electrically-conductlve extension cowl to reduce electrostatic effects. Ground the cowl when possible during sanpling. 2. Personal sampling pimp, 0.5 to 16 L/min (see step 4 f r flow rate), with flexible connecting tubing. 3. Microscope, positive phase contrast, with green or blue filter, 8 to 10X eyepiece, and 40 to 45X phase objective (total magnification ca. 400X); minerical aperture = 0.65 to 0.75. 4. Slides, glass, frosted-end, pre-cleaned, 2S x 75 im. 5. Cover slips, 22 x 22 mn, No. 1-1/2, unless therwise specified by microscope nunufacturer. 6. Lacquer or nail polish. 7. knife, #10 surgical steel, curved blade. 8. Tweezers. 9. Heated a 1 uni mm block for clearing filters on glass slides (see ref. [5] for instructions on manufacture). 10. Micropipets, 5-pL and 100- to 500-pL. 11. Graticule, Walton-Beckett type with 100-vxn diameter circular field (area = 0.00785 mna)at the specimen plane (Type G-22 for A Rules; Type G-24 for 8 Rules). Available from PTR Optics Ltd., 145 Newton Street, Waltham, MA 02154 [phone (617) 891-6000] and McCrone Accessories and Components, 850 Pasquinelli Drive, Westmont, IL 60559 [phone (312) 887-7100]. NOTE: The graticule is custom-nude for each microscope. Specify disc diameter needed to fit exactly the ocular of the microscope and the diameter (nm) of the circular counting area (see APPENDIX A). 12. HSE/NPL phase contrast test slide, Mark II. Available from PTR Optics Ltd. (address above). 13. Telescope, ocular phase-ring centering. 14. Stage micrometer (0.01-mm divisions). 15. Wire, nulti-stranded, 22-gauge. SPECIAL PRECAUTIONS: Acetone is extremely flanmable. Take precautions not to ignite it. Heating of acetone in volunes greater than 1 mL irust be done in a ventilated laboratory ftm hood using a flameless, spark-free heat source. SAMPLING: 1. Calibrate each personal sampling pump with a representative sampler in line. 8/15/87 7400-2 NIOSH Manual of Analytical Methods METHOO: 7400 FIBERS 2. For personal sampling, fasten sampler to the worker's lapel near the worker's mouth. Remove top cover from cowl extension (open face) and orient face down. Wrap joint between cowl and monitor body with shrink tape to prevent air leaks. NOTE: If possible, ground the cassette to remove any surface charge, using a wire held In contact (e.g., with a hose clamp) with the conductive cowl and a non-electrical metal fixture, or a cold-water pipe. 3. Submit at least two field blanks (or 10% of the total sanples, whichever Is greater) for each set of samples. Remove top covers fran the field blank cassettes and store top covers and cassettes in a clean area (bag or box) with the top covers from the sampling cassettes during the sampling period. Replace the top covers In the cassettes after sampling. 4. Sample at 0.5 L/min or greater C9]. Adjust sampling flow rate, Q (L/tain), and time, t (min), to produce a fiber density, E, of 100 to 1300 fibers/im* (3.85*104 to 5*10* fibers per 25-em filter with effective collection area A,.* 385 na) for optimal) accuracy. These variables are related to the action level (one-half the current standard), L (fibers/mL), of the fibrous aerosol being sampled by: t . {Ac)(E) (Q)(L)10 NOTE 1: The purpose of adjusting sampling times is to obtain optiman fiber loading on the filter. A sanpling rate of 1 to 4 L/min for 8 hrs Is appropriate In non-dusty atmospheres containing ca. 0.1 fiber/mL. Dusty atmospheres require snaller sample volianes (<400 L) to obtain countable samples. In such cases take short, consecutive sanples and average the results over the total collection time. For docixnenting episodic exposures, use high flow rates (7 to 16 L/min) over shorter sampling times. In relatively clean atmospheres, where targeted fiber concentrations are much less than 0.1 fiber/mL, use larger sample volumes (3000 to 10000 L) to achieve quantifiable loadings. Take care, however, not to overload the filter with background dust. If > SOX of the filter surfer is covered with particles, the filter may be too overloaded to count and will bias the measured fiber concentration. NOTE 2: 0SHA regulations specify a maxibud sanpling rate of 2.S L/min [1]. 5. At the end of sanpling, replace top cover and small end caps. 6. Ship sanples with conductive cowl attached in a rigid container with packing nwterial to prevent jostling or damage. NOTE: Oo not use untreated polystyrene foam in shipping container because electrostatic forces may cause fiber loss from sanple filter. SAMPLE PREPARATION: NOTE: The object is to produce sanples with a smooth (non-grainy) background in a median with refractive index < 1.46. This method collapses the filter for easier focusing and produces permanent mounts which are useful for quality control and Interlaboratory comparison. The altminun "hot block* technique may be used outside the laboratory [5], Other mounting techniques meeting the above criteria may also be used (e.g., the laboratory fane hood procedure for generating acetone vapor as described in Method 7400 revision of 5/15/85, or the non-permanent field mounting technique used in p&CAM 239 [2,4,8,22]). A videotape of the mounting procedure is available from the NIOSH Publication Office [20]. 7. Ensure that the glasi slides and cover slips are free of dust and fibers. 8. Adjust the rheostat to heat the "hot block* to ca. 70 *C [51. NOTE: If the "hot block* is not used in a fume hood, it must rest on a ceranic plate and be isolated fran any surface susceptible to heat damage. 8/15/87 7400-3 NIOSH Manual of Analytical Methods FIBERS METHOO: 7400 9. Mount a wedge cut Fran the sarrple filter on a clean glass slide. a. Cut wedges of ca. 25* of the filter area with a curved-blade steel surgical knife using a rocking notion to prevent tearing. Place wedge, dust side up, on slide. NOTE: Static electricity will usually keep the wedge on the slide. b. Insert slide with wedge Into the receiving slot at base of "hot block*. Place tip of a micropipet containing ca. 250 pL acetone into the inlet port of the PTFE cap on top of the "hot block*. Inject the acetone into the vaporization chamber with a slow, steady pressure on the plunger button while holding plpet firmly In place. After waiting 3 to 5 sec for the filter to clear, remove plpet and slide fron their ports. CAUTION: Although the volune of acetone used is small, use safety precautions. Wbrfc In a well-ventilated area (e.g., laboratory fane hood). Take care not to Ignite the acetone. Continuous, frequent use of this device In an unventilated space may produce explosive acetone vapor concentrations. c. Using the S-pL micropipet, immediately place 3.0 to 3.5 pL trlacetin on the wedge. Gently lower a clean cover slip onto the wedge at a slight angle to reduce bubble formation. NOTE; If too many bubbles form or the amount of triacetin is insufficient, the cover slip may become detached within a few hours. If excessive triacetin remains at the edge of the filter under the cover slip, fiber migration may occur. d. Glue the edges of the cover slip to the slide using lacquer or nail polish [10] Counting may proceed immediately after clearing and mounting are conpleted. NOTE: If clearing is slow, warm the slide on a hotplate (surface tenperature 50 *C) for up to 15 min to hasten clearing. Heat carefully to prevent gas bubble formation. CALIBRATION AND QUALITY CONTROL: 10. Microscope adjustments. Follow the manufacturers instructions. At least once daily use the telescope ocular supplied by the manufacturer to ensure that the phase rings (annular diaphragm and phase-shifting elements) are concentric. With each microscope, keep a logbook in which to record the dates of microscope cleanings, adjustments, and calibrations. a. Each time a sample is examined, do the following: (1) Adjust the light source for even illumination across the field of view at the condenser iris. With sane microscopes, the illumination may have to be set up with bright field optics rather than phase contract optics. NOTE: Use Kohler illunination if available. (2) Focus on the particulate material to be examined. (3) Make sure that the field iris is in focus, centered on the sample, and open only enough to fully illuminate the field of view. b. Check the phase-shift detection limit of the microscope periodically for each analyst/microscope confcination: (1) Center the KSE/NPL phase-contrast test slide under the phase objective. (2) Bring the blocks of grooved lines into focus in the graticule area. NOTE: The slide contains seven blocks of grooves (ca. 20 grooves per block) in descending order of visibility. For asbestos counting the microscope optics must completely resolve the grooved lines in block 3 although they may appear somewhat faint, and the grooved lines in blocks 6 and 7 must be invisible when observing them in the center of the graticule area. Blocks 4 and 5 must be at least partially visible but may vary slightly in visibility between microscopes. A microscope which fails to meet these requirmnents has resolution either too low or too high for fiber counting. (3) If image quality deteriorates, clean the microscope optics. If the problm persists, consult the microscope manufacturer. 8/15/87 7400-4 NIOSH Manual of Analytical Methoc METMOO: 7400 FIBERS 11. Oocunent the laboratory's precision for each counter for replicate fiber counts. a. Maintain as part of the laboratory quality assurance program a set of reference slides to be used on a daily basis. These slides should consist of filter preparations including a range of loadings and background dust levels from a variety of sources including both field and PAT samples. The Quality Assurance Officer should maintain custody of the reference slides and should supply each counter with a minimum of one reference slide per workday. Change the labels on the reference slides periodically s that the counter does not become familiar with the sanples. b. Fran blind repeat counts on reference slides, estimate the laboratory intra- and intercounter sr (see step 21). Obtain separate values of relative standard deviation for each sample matrix analyzed in each of the following ranges: 5 to 20 fibers in 100 graticule fields, 21 to SO fibers in 100 graticule fields, SI to 100 fibers in 100 graticule fields, and 100 fibers in less than 100 graticule fields. Maintain control charts for each of these data files. NOTE 1: Since fiber counting is the measurement of randomly placed fibers which may be described by a Poisson distribution, a square root transformation of the fiber count data will result in approximately normally distributed data. NOTE 2: Certain sample tutrices (e.g., asbestos cement) have been shown to give poor precision [6] 12. Prepare and count field blanks along with the field samples. Report counts on each field blank. NOTE 1: The identity of blank filters should be unknown to the counter until all counts have been completed. NOTE 2: If a field blank yields greater than 7 fibers per 100 graticule fields, report possible contamination of the samples. 13. Perform blind recounts by the same counter on 10X of filters counted (slides relabeled by a person other than the counter). Use the following test to determine whether a pair of counts by the same counter on the same filter should be rejected because of possible bias: Discard the sanple if the difference between the two counts exceeds 2.77 (X)sr, where X * average of the two fiber *ounts and sr * intracounter relative standard deviation fran step 11. NOTE: If a pair of counts is rejected by this test, recount the remaining samples in the set and test the new counts against the first counts. Discard all rejected paired counts. It is not necessary to use this statistic on blank counts. 14. Enroll each new counter in a training course which compares perforewnce of counters on a variety of sanples using this procedure. NOTE: All laboratories engaged in asbestos counting should participate in a proficiency testing program such as the AIHA-NIOSH Proficiency Analytical Testing (PAT) Program and routinely exchange field samples with other laboratories to compare performance of counters. MEASUREMENT: 15. Center the slide on the stage of the calibrated microscope under the objective lens. Focus the microscope on the plane of the filter. 16. Adjust the microscope (Step 10) [7]. NOTE: Calibration with the HSE/NPL test slide determines the minimum detectable fiber diameter (ca. 0.25 v*n). 17. Select one of the following sets of counting rules: NOTE: The two sets of rules have produced approximately equivalent mean counts on a variety of asbestos sample types [6]. OSHA regulations require the use of the A rules [1]. In either case, the rules must be strictly followed to obtain valid results. No hybridizing of the two sets of rules is permitted. 8/15/B7 7400-5 NIOSH Manual of Analytical Methods f;i"NT T A FIBERS METHOO: 7*00 a. A Rules (same as P&CAM 239 rules [2,4,8]; see APPENDIX B). 1. Count only fibers longer than 5 pm. Measure length of curved fibers along the curve. 2. Count only fibers with a length-to-width ratio equal to or greater than 3:1. 3. For fibers which cross the boundary of the graticule field: a. Count any fiber longer than 5 pm which lies entirely within the graticule area. b. Count as 1/2 fiber any fiber with only one end lying within the graticule area, provided that the fiber meets the criteria of rules a.l. and a.2. c. Do not count any fiber which crosses the graticule boundary acre than once. d. Reject and do not count all other fibers. 4. Count bundles of fibers as one fiber unless individual fibers can be Identified by observing both ends of a fiber. 5. Count enough graticule fields to yield 100 fibers. Count a minimum of 20 fields. Stop at 100 graticule fields regardless of count. b. B Rules (see APPEN0IX B) 1. Count only ends of fibers. Each fiber must be longer than 5 i*n and less than 3 pm diameter. 2. Countonly ends of fibers with a length-to-width ratio equal to or greater than 5:1. 3. Count each fiber end which falls within the graticule area as one end, provided that the fiber meets rules b.l and b.2. Add split ends to the count as appropriate if the split fiber se^nent also meets the criteria of rules b.l and b.2. 4. Count visibly free ends which meet rules b.l and b.2 when the fiber appears to be attached to another particle, regardless of the size of the other particle. Count the end of a fiber obscured by another particle if the particle covering the fiber end is less than 3 jxn in diameter. 5. Count free ends of fibers emanating from large clixnps and bundles up to a maxinun of 10 ends (5 fibers), provided that each segment meets rules b.l and b.2. 6. Count enough graticule fields to yield 200 ends. Count a mininun of 20 graticule fields. Stop at 100 graticule fields, regardless of count. 7. Divide total end count by 2 to yield fiber count. 18. Start counting from the tip of the filter and progress along a radial line to the outer edge. Shift up or down on the filter, and continue in the reverse direction. Select graticule fields randomly by looking away from the eyepiece briefly while advancing the mechanical stage. Ensure that, as a mininun, each analysis covers one radial line from the filter center to the outer edge of the filter. When an agglomerate covers ca. 1/6 or more of the graticule field, reject the graticule field and select another. Do not report rejected graticule fields in the total nunber counted. NOTE 1: When counting a graticule field, continuously scan a range of focal planes by moving the fine focus knob to detect very fine fibers which have becane embedded in the filter. The small-diameter fibers will be very faint but are an important contribution to the total count. A minimum counting time of 15 seconds per field is appropriate for accurate counting. NOTE 2: This method does not allow for differentiation of fibers based on morphology. Although some experienced counters are capable of selectively counting only fibers which appear to be asbestifona, there is presently no accepted method for ensuring uniformity of judgment between laboratories. It is, therefore, incunbent upon all laboratories using this method to report total fiber counts. If serious contamination from non-asbestos fibers occurs in samples, other techniques such as transmission electron microscopy must be used to identify the asbestos fiber fraction present in the sample (see NI0SH Method 7402). In seme cases (i.e., for fibers with diameters > 1 urn), polarized light microscopy (e.g., NIOSH Method 7403) may be used to identify and eliminate interfering non-crystalline fibers. 8/15/87 7400-6 NIOSH Manual of Analytical Methods HETHOO: 7400 FIBERS CALCULATIONS AND REPORTING OF RESULTS: 19. Calculate and report fiber density on the filter, E (fibers/iwn*), by dividing the total fiber count per graticule field, F/n^, sinus the mean field blank count per graticule field, B/nt), by the graticule field area, Af (0.0078S me* for a properly calibrated Ualton-Beckett graticule): n* rw> E --------- --------' fibers/nn*. *f NOTE: Fiber counts above 1300 fibers/me* and fiber counts fro* sanples with > SOX of filter area covered with particulate should be reported as "uncountable" or "probably biased." 20. Calculate and report the concentration, C (fibers/mL), of fibers In the air volume sanpled, V (L), using the effective collection area of the filter, A,. (38S me* for a 2S-nm filter): r _ (E)(A(.) V10* * NOTE: Periodically check and adjust the value of Ac, If necessary. 21. Report Intralaboratory and Interlaboratory relative standard deviations (from Step 11) with each set of results. NOTE: Precision depends on the total nuNber of fibers counted [4,11]. Relative standard deviation (also called coefficient of variation) is docunented in references [4,11,12,13] for fiber counts up to 100 fibers in 100 graticule fields. Comparability of interlaboratory results is discussed below. As a first approximation, use 213X above and 49X below the count as the upper and lower confidence limits for fiber counts greater than 20 (Fig. 1). EVALUATION OF HETHOO: A. This method is a revision of P&CAM 239 [2,4,8]. A stannary of the revisions Is as follows: 1. Sanpling: The change from a 37-nm to a 2S-twn filter ieproves sensitivity for similar air volumes. The change in flow rates allows for 2-m* full-shift sanples to be taken, providing that the filter is not overloaded with non-flbrous particulates. The collection efficiency of the sampler is not a function of flow rate in the range 0.S to 16 L/min [9]. 2. Sample Preparation Technique: The acetone vapor-triacetin preparation technique is a faster, more permanent mounting technique than the dimethyl phthalate/diethyl oxalate method of p&CAH 239 [2,4,5,8,14], The aluminue "hot block" technique minimizes the amount of acetone needed to prepare each saeple. 3. Measurement: a. The Walton-Beckett graticule standardizes the area observed [14,15]. b. The HSE/NPL test slide standardizes microscope optics for sensitivity to fiber diameter [7,14]. 8/15/87 7400-7 NIOSH Manual of Analytical Methods FIBERS METHOD: 7400 c. An international collaborative study involved 16 laboratories using prepared slides from the asbestos cement, milling, mining, textile, and friction material industries [6]. The modified CRS (NIOSH B) Rules were found to yield equivalent counts but were more precise than the AIA (NIOSH A)* Rules. The relative standard deviations (sr) varied with sanple type and laboratory. The ranges were: Intralaboratorv Inter!aboratory Overall AIA (NIOSH A Rules)* Modified CRS (NIOSH B Rules) 0.12 to 0.40 0.11 "to 0.29 0.27 to 0.8S 0.20 to 0.35 0.46 0.2S Under AIA rules, only fibers having a diameter less than 3 jxti are counted and fibers attached to particles larger than 3 im are not counted. NIOSH A Rules are otherwise similar to the AIA rules. d. The B Rules have also been favorably received by analysts as less anbiguous and simpler to use; these rules also showed the least bias relative to AIA rules in the collaborative study. An independent NIOSH laboratory study using amosite fibers reported a relative standard deviation, including within- and between-sanple variability, of 0.16 for the B Rules [16]. Another NIOSH study was conducted using field samples of asbestos [19]. This study indicated intralaboratory sr in the range 0,17 to 0.25 and an interlaboratory sr of 0.45. This agrees well with other recent studies [6,11,13]. e. Because of past inaccuracies associated with low fiber counts, the minim* recanmended loading has been increased to 100 fibers/nm' filter area (80 fibers total count). This level should yield intracounter sr in the range of 0.13 to 0.17 [4,8,16,19]. B. Interlaboratory Comparability: At this time, there is no independent method for assessing the overall accuracy of this method. One measure of reliability is to estimate how well the count for a single sample agrees with the mean count from a large nwber of laboratories. The following discussion indicates how this estimation can be carried out based on measurements of the interlaboratory variability, as well as showing how the results of this method relate to the theoretically attainable counting precision and to measured intra- and interlaboratory sr. Theoretically, the process of counting randomly (Poisson) distributed fibers on a filter surface will give an sr that depends on the nurber, N, of fibers counted: sr - 1/(N)1/2 (1) Thus sr is 0.1 for 100 fibers and 0.32 for 10 fibers counted. The actual sr found in a nwber of studies is greater than these theoretical nuibers [6,11,12,13]. An additional component of variability comes primarily from subjective laboratory-to-1aboratory differences. In a study of ten counters in a continuing sample exchange program, Ogden [11] found this subjective component of intralaboratory sr to be approximately 0.2 and estimated the overall sr by the term: (N + (0.2 * N)?)1/2 N (2) , ,, ; :r , 8/15/87 7400-8 NIOSH Manual of Analytical Methods HETHOO: 7400 FIBERS Ogden found that the 90% confidence Interval of the Individual intralaboratory counts In relation to the means were 42 sr and - 1.5 sr. In this program, one sample out of ten was a quality control sanple. For laboratories not engaged in an intensive quality assurance program, the subjective caiponent of variability can be higher. In a study of field sanple results in 46 laboratories, the Asbestos Information Association [13] also found that the variability had both a constant component and one that depended on the fiber count. These results gave a subjective interlaboratory caiponent of sr (on the same basis as Ogden's) for field samples of ca. 0.45. A similar value was obtained for 12 laboratories analyzing a set of 24 field samples [19]. This value falls slightly above the range of sr (0.25 to 0.42 for 1984-85) found for 80 reference laboratories in the NIOSH Proficiency Analytical Testing (PAT) program for laboratory-generated sanples [12]. A muter of factors influence sr for a given laboratory, such as that laboratory's actual counting performance and the type of samples being analyzed. In the absence of other information, such as from an interlaboratory quality assurance program using field saeples, the value for the subjective component of variability is chosen as 0.45. Note that, though based on at least two studies, this is a somewhat arbitrary choice. It Is hoped that by the use of this matter in the absence of other information, laboratories will carry out the reconmended Interlaboratory quality assurance programs to Improve their performance and thus reduce the sr. The above relative standard deviations apply when the population mean has been determined. It is more useful, however, for laboratories to estimate the 90% confidence Interval on the mean count from a single sample fiber count (Figure 1). These curves assume similar shapes of the count distribution for interlaboratory and intralaboratory results [11]. For exanple, if a sample yields a count of 24 fibers, Figure 1 indicates that the mean Interlaboratory count will fall within the range of 227% above and 52% below that value 90% of the time. He can apply these percentages directly to the air concentrations as well. If, for instance, this sample (24 fibers counted) represented a 500-L volune, then the measured concentration is 0.02 fibers/ml (assuring 100 fields counted, 2S-om filter, 0.0078S m? counting field area). If this same sanple were counted by a group of laboratories, there is a 90% probability that the mean wuld fall between 0.01 and 0.08 fiber/mL. These limits should be reported in any caiparison of results between laboratories. Note that the sr of 0.45 used to derive Figure 1 is used as an estimate for a random group of laboratories. If several laboratories belonging to a quality assurance group can show that their interlaboratory sr is smaller, then it is more correct to use that smaller sr. However, the estimated sr of 0.45 is to be used in the absence of such information. Note also that it has been found that sr can be higher for certain types of samples, such as asbestos cement. Quite often the estimated airborne concentration from an asbestos analysis Is used to co*re to a regulatory standard. For Instance, If one is trying to show caipliance with an 0.5 fiber/mL standard using a single sanple on which 100 fibers have been counted, then Figure 1 indicates that the 0.5 fiber/mL standard must be 213% higher than the measured air concentration. This indicates that if one measures a fiber concentration of 0.16 fiber^eL (100 fibers counted), then the mean fiber count by a group of laboratories (of which the compliance laboratory might be one) has a 95% chance of being less than 0.5 fibers/mL; i.e., 0.16 4 2.13 x 0.16 * 0.5. I U-:' 8/15/87 7400-9 NIOSH Hanual of Analytical Nethods METHOO: 7400 FIBERS It can be seen frai Figure 1 that the Poisson component of the variability Is not very Important unless the matter of fibers counted Is small. Therefore, a further approximation Is to simply use +2131 and -49% as the upper and lower confidence values of the mean for a 100-fiber count. 90% CONFIDENCE NTERVAL ON MEAN COUNT (SUBJECTIVE COMPONENT (0.45) + POISSON COMPONENT) o -100 I 9 --' I I..... . I H I -M <0 20 30 40 SO 60 70 80 90 100 9SKPR0BABUTY MEAN COUNT B ABO/E 1HSLEVB. NUMB0) Of RBER3 COUNTED M A SNOLE SAMPLE Figure 1. Interlaboratory Precision of Fiber Counts REFERENCES: [1] Occupational Safety and Health Adetnlstratlon, U.S. Department of Labor, Occupational Exposure to Asbestos, Tremolite, Anthophylllte, and Actlnolite Asbestos; Final Rules, 29 CFR Part 1910.1001 Amended June 20, 1986. [2] Revised Reca--ended Asbestos Standard, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 77-169 (1976). [3] Criteria for a Recamnended Standard...Occupational Exposure to Fibrous Glass, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 77-1S2 (1977). [4] Leldel. N. A., S. G. Bayer, R. D. Zimwalde, and K. A. Busch. USPKS/NIOSH Mobrane Filter Method for Evaluating Airborne Asbestos Fibers, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 79-127 (1979). [5] Baron, P. A. and G. C. Pickford. *An Asbestos Sample Filter Clearing Procedure," Aool. M- a*. 1:169-171. 199 (1986). [6] Crawford, N. P., H. L. Thorpe, and W. Alexander. "A CornerIson of the Effects of Different Counting Rules and Aspect Ratios on the Level and Reproducibility of Asbestos Fiber Counts," Part I: Effects on Level (Report No. W82/23), Part II: Effects on Reproducibility (Report No. TM/82/24), Institute of Occupational Medicine, Edinburgh, Scotland (Decenber, 1982). 8/15/87 7400-10 NIOSH Manual of Analytical Methods METHOO: 7400 FIBERS [7] Rooker, S. J., N. P. Vaughn, and J. M. LeGuen. "On the Visibility of Fibers by Phase Contrast Microscopy," Acer. Ind. Hyg. Assoc. J., A3, 505-S15 (1982). [8] NIOSH Manual of Analytical Methods, 2nd id., Vol. 1., PtCAM 239, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 77-157-A (1977). [9] Johnston, A. H., A. 0. Jones, and J. H. Vincent. "The Influence of External Aerodynamic Factors on the Measurement of the Airborne Concentration of Asbestos Fibers by the Membrane Filter Method," Ann. Occup. Hyg.. 25, 309-316 (1982). [10 Asbestos International Association, AIA Health and Safety Rccc--ended Technical Method #1 (RTMI). "Airborne Asbestos Fiber Concentrations at Workplaces by Light Microscopy" (Meefcrane Filter Method), London (1979). [113 Ogden, T. L. "The Reproducibility of Fiber Counts," Health and Safety Executive Research Paper 18 (1982). [12] Schlecht, P. C. and S. A. Schulaan. "Performance of Asbestos Fiber Counting Laboratories In the NIOSH Proficiency Analytical Testing (PAT) Program," Am. Ind. Hyp. Assoc. J., 47. 259-266 (1986). [13] "A Study of the Empirical Precision of Airborne Asbestos Concentration Measurmmnts in the Workplace by the M*W>rane Filter Method," Asbestos Information Association, Air Monitoring Conmittee Report, Arlington, VA (June, 1983). [14] Chatfleld, E. J. Measurement of Asbestos Fiber Concentrations In Workplace Atmospheres, Royal Comission on Matters of Health and Safety Arising from the Use of Asbestos In Ontario, Study No. 9, 180 Dundas Street West, 22nd Floor, Toronto, Ontario, CANADA MSG 1Z8. [15] Walton, W. H. "The Nature, Hazards, and Assessment of Occupational Exposure to Airborne Asbestos Dust: A Review," Ann. Occup. Hyp.. 25, US-247 (1982). [16] Taylor, D. G., P. A. Baron, S. A. Shulman and J. W. Carter. "Identification and Counting of Asbestos Fibers," Am. Ind. Hyg. Assoc. J. 45(2), 84-88 (1984). [17] Busch, k. A. and D. G. Taylor. "Statistical Protocol for the NIOSH Validation Tests," Chemical Hazards in the Workplace, Measurmaent and Control, ACS Symposium Series 149, American Chemical Society, Washington, DC (1981). [18] Groff, Jensen. NIOSH PAT Coordinator, Private coamunication. [19] Baron, P. A. and S. Shulman. "Evaluation of the Magiscan Image Analyzer for Asbestos Fiber Counting." m, Ind. Hyg. Assoc. J., (in press). [20] Sinclair, R. C. "Filter Mounting Procedure," NIOSH Publication Videotape No. 194 (1984 [updated 1986]). [21] Keith, L. H., W. Cnamnett, J. Oeegan, Jr., R. A. Libby, J. K. Taylor, and G. Wentler. "Principles of Environmental Analysis," Anal, them., 55:2210-2218 (1983). [22] Jankovic, J. T., W. Jones, and J. Clere. "Field Techniques for Clearing Cellulose Ester Filters Used in Asbestos Sailing," Aool. Ind. Hyg.. 1:145-147 (1986). HETHOO REVISED BY: James W. Carter, David G. Taylor, Ph.D., CIH, and Paul A. Baron, Ph.D., NIOSH/DPSE; based on the revised Method P6CAM 239 [2,4,8]. APPENDIX A: CALIBRATION OF THE WALT0W-8ECKETT GRATICULE: Before ordering the Walton-Beckett graticule, the following calibration mist be done to obtain a counting area (0) 100 tm in diameter at the Image plane. The diameter, dc (am), of the circular counting area and the disc diameter mist be specified when ordering the graticule. 1. Insert any available graticule into the eyepiece and focus so that the graticule lines are sharp and clear. 2. Set the appropriate interpupillary distance and, if applicable, reset the binocular head adjustment so that the magnification remains constant. V15/87 7400-11 NIOSH Manual of Analytical Methods FIBERS HETHOO: 7400 3. Install the 40 to 45X phase objective. 4. Place a stage micrometer on the microscope object stage and focus the microscope on the graduated lines. 5. neasure the magnified grid length of the graticule, Lq (ten), using the stage micrometer. 6. Remove the graticule from the microscope and measure Its actual grid length, la (nm). This can best be acconplished by using a stage fitted with verniers. 7. Calculate the circle diameter, dc (nm), for the Walton-Beckett graticule: Example: If L,, 112 \M, L, 4.5 me and 0 * 100 i*n, then dc * 4.02 nm. 8. Check the field diameter, 0 (acceptable range 100 m 2 pm) with a stage micrometer upon receipt of the graticule from the manufacturer. Determine field area (acceptable range 0.00785 nm* 0.00032 mm*). APPENOIX B: COMPARISON OF COUNTING RULES: Figure 2 shows a Ualton-Beckett graticule as seen through the microscope. Although the graticule Incorporates the 3:1 aspect ratio, both the "A" and "B" rules will be discussed as they apply to the labeled fibers in the figure. 5 5 x 5/3 3 8/15/87 Figure 2. Ualton-Beckett graticule with fibers. 7400-12 M10SH Manual of Analytical Methods WETHOO: 7400 FIBER COUNT Fiber A Rules B Rules 1 1 fiber 3 ends 2 1 fiber 2 ends 3 1 fiber 2 ends 4 1 fiber 5 ends 5 1 fiber Do not count 6 1 fiber 1 end 7 1/2 fiber 1 end 8 Do not count Do not count FIBERS DISCUSSION (A)"A" roles do not allow for split ends; therefore, count one fiber. (B) Under 'B* rules, first detemine whether the fiber meets dimensional criteria, (i.e,, >5 v**, >5:1 aspect ratio, <3 in diameter). Next determine and count which two ends are the main trunk of the fiber. Finally, count all split ends >5 in as one end. Fiber #1 is counted as 3 ends. (A) Single fiber with small particle attached. The particle is treated as if it does not exist by the VA" rules. (B) The particle is <3 in diameter and therefore ignored under "B* rules. (A) As with Fiber 1, count one fiber under "A* rules because it meets the >3:1 aspect ratio, >5 in criteria. (B) The split end is <5 in long so it is not counted under aBa rules. (A) Fiber ends all attached to a central large fiber or bundle; therefore, count one fiber under "A* rules. (B) Count two ends as belonging to the main fiber. Three of the remaining four split ends are >5 in, giving a total of 5 ends. (A) No diameter limit under "A" rules; therefore count this thick fiber because it meets the >3:1, >5 in counting criteria. (B) The fiber is >3 in diameter; therefore not counted under "B* rules. (A) Ignore non-fibrous particulate matter under the "A* rules; count this as a whole fiber. (B) The short end of the fiber is <5 in long and obscured by a particle >3 in in diameter; therefore, not counted under aBa rules. (A) Fibers which meet rules a.1. and a.2. and cross the graticule boundary are counted as 1/2 fiber under aAa rules unless the fiber crosses the graticule boundary more than once, in which case the fiber is not counted no matter how many ends lie within the graticule area. (6) Fiber ends lying inside the graticule boundary are counted as one end provided that the entire fiber meets rules b.l. and b.2. and each end is >5 im. The portion of the fiber lying outside the graticule boundary must be considered in order to make this determination. Under "B" rules, it does not matter how often the fiber crosses the graticule boundary. The fiber is <$ pm long. 8/15/87 7400-13 NIOSH Manual of Analytical Methods