1、Designation: D 7200 06Standard Practice forSampling and Counting Airborne Fibers, Including AsbestosFibers, in Mines and Quarries, by Phase ContrastMicroscopy and Transmission Electron Microscopy1This standard is issued under the fixed designation D 7200; the number immediately following the designa
2、tion indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice2describes the dete
3、rmination of the con-centration of fibers, expressed as the number of such fibers permillilitre of air, using phase contrast microscopy and optionallytransmission electron microscopy to evaluate particulate mate-rial collected on a membrane filter in the breathing zone of anindividual or by area sam
4、pling in a specific location. Thispractice is based on the core procedures provided in theInternational Organization for Standardization (ISO) StandardISO 8672(1)3, the National Institute for Occupational andHealth (NIOSH) Manual of Analytical Methods, NIOSH 7400(2), and the Occupational Safety and
5、Health Administration(OSHA) Method ID 160 (3). This practice indicates the impor-tant points where these methods differ, and provides informa-tion regarding the differences. However, selecting portions ofprocedures from different published methods generally re-quires a user to report that they have
6、used a modification to amethod rather than claim they have used the method as written.This practice further gives guidance on how differential count-ing techniques may be used to indicate where a population offibers may be asbestos.1.2 The practice is used for routine determination of anindex of occ
7、upational exposure to airborne fibers in mines,quarries, or other locations where ore may be processed orhandled. The method gives an index of airborne fiber concen-tration. The method provides an estimate of the fraction ofcounted fibers that may be asbestos. This practice should beused in conjunct
8、ion with electron microscopy (See AppendixX1) for assistance in identification of fibers.1.3 This practice specifies the equipment and procedures forsampling the atmosphere in the breathing zone of an individualand for determining the number of fibers accumulated on afilter membrane during the cours
9、e of an appropriately-selectedsampling period. The method may also be used to sample theatmosphere in a specific location in a mine or in a room of abuilding (area sampling).1.4 The ideal working range of this practice extends from100 fibers/mm2to 1300 fibers/mm2of filter area. For a 1000-Lair sampl
10、e, this corresponds to a concentration range fromapproximately 0.04 to 0.5 fiber/mL (or fiber/cm3). Lower andhigher ranges of fiber concentration can be measured byreducing or increasing the volume of air collected. However,when this practice is applied to personal sampling in mines andquarries, the
11、 level of total suspended particulate may impose anupper limit to the volume of air that can be sampled if the filtersproduced are to be of appropriate particulate loading for fibercounting.1.5 Users should determine their own limit of detectionusing the procedure in Practice D 6620. For reference,
12、theNIOSH 7400 method gives the limit of detection as 7 fibers/mm2of filter area. For a 1000-L air sample, this corresponds toa limit of detection of 0.0027 fiber/mL (or fiber/cm3). ForOSHA ID 160 the limit of detection is given as 5.5 fibers/mm2of filter area. For a 1000-L air sample, this correspon
13、ds to alimit of detection of 0.0022 fiber/mL (or fiber/cm3).1.6 If this practice yields a fiber concentration that does notexceed one-half the permissible exposure limit or thresholdlimit value for the particular regulated fiber variety, no furtheraction may be necessary. If the fiber concentration
14、exceedsone-half of the regulated permissible exposure limit or thresh-old limit value for the particular regulated fiber variety,examine the data to determine if more than 50 % of the countedfibers may be bundles, fibers longer than 10 m, or fibersthinner than 1.0 m. If these counts exceed 50 % of t
15、he totalcount, then there is an increased possibility that asbestos ispresent in the sample. Use the optional method specified inAppendix X1 to measure the concentration or proportion of thefibers counted that is of the regulated variety. If asbestos fibers1This practice is under the jurisdiction of
16、ASTM Committee D22 onAir Qualityand is the direct responsibility of Subcommittee D22.04 onWorkplaceAtmospheres.Current edition approved June 1, 2006. Published July 2006.2This test method is based on NIOSH 7400, OSHA Method ID 60, andISO 8672. Users of this ASTM standard are cautioned that if they w
17、ish to complywith one of these specific procedures exactly they should follow that procedure,otherwise they should document the modification.3Boldface numbers in parentheses refer to the list of references appended to thismethod.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West
18、 Conshohocken, PA 19428-2959, United States.are identified by this method, the mine/quarry operator shouldconduct a geological survey of the property to identify thesource of the fibers.1.7 The mounting medium used in this practice has arefractive index of approximately 1.45. Fibers with refractivei
19、ndices in the range of 1.4 to 1.5 will exhibit reduced contrast,and may be difficult to detect.1.8 Fibers less than approximately 0.2 m in diameter maynot be detected by this practice. (4)1.9 This standard may involve hazardous materials, opera-tions, and equipment. This standard does not purport to
20、address all of the safety problems associated with its use. It isthe responsibility of the user of this standard to establishappropriate safety and health practices and determine theapplicability of regulatory limitations prior to use. For specificprecautionary statements, see Section 7.2. Reference
21、d Documents2.1 ASTM Standards:4D 257 Test Methods for DC Resistance or Conductance ofInsulating MaterialsD 1356 Terminology Relating to Sampling and Analysis ofAtmospheresD 1357 Practice for Planning the Sampling of the AmbientAtmosphereD 3670 Guide for Determination of Precision and Bias ofMethods
22、of Committee D22D 5337 Practice for Flow Rate Calibration of PersonalSampling PumpsD 6620 Practice for Asbestos Detection Limit Based onCounts2.2 Other StandardsNIOSH 7400 National Institute of Occupational Health andSafety (Revised 1994).5(RTM 1) Asbestos InternationalAssociation (AIA), Recom-mende
23、d Technical Method No.1.6ID 160 Occupational Safety and Health Administration(OSHA).ISO 8672 International Organization for Standardization.3. Terminology3.1 Description of terms specific to this practice, in additionto those found in Terminology D 1356:3.1.1 asbestosa term applied to six specific s
24、ilicate min-erals belonging to the serpentine and amphibole groups, whichhave crystallized in the asbestiform habit, causing them to beeasily separated into long, thin, flexible, strong fibers whencrushed or processed (5). The Chemical Abstracts ServiceRegistry Numbers of the most common asbestos va
25、rieties are:chrysotile (12001-29-5), riebeckite asbestos (crocidolite)(12001-28-4), grunerite asbestos (Amosite) (12172-73-5), an-thophyllite asbestos (77536-67-5), tremolite asbestos (77536-68-6) and actinolite asbestos (77536-66-4).The precise chemical composition of each species varieswith the lo
26、cation from which it was mined. Other amphiboleminerals which exhibit the characteristics of asbestos have alsobeen observed (6).The nominal compositions of the most common asbestosvarieties are:Chrysotile Mg3Si2O5(OH)4Crocidolite Na2Fe32+Fe23+Si8O22(OH)2Amosite (Mg,Fe)7Si8O22(OH)2Anthophyllite (Mg,
27、Fe)7Si8O22(OH)2Tremolite Ca2(Mg,Fe)5Si8O22(OH)2Mg/(Mg + Fe2+) 0.9 1.0Actinolite Ca2(Mg,Fe)5Si8O22(OH)2Mg/(Mg + Fe2+) 0.5 0.9NOTE 1Actinolite compositions in which Mg/(Mg + Fe2+) is between0 and 0.5 are referred to as ferroactinolite. See Ref. (7) for the full namingconventions specified by the Inter
28、national Mineralogical Association.3.1.2 area samplean air sample collected so as to repre-sent the concentration of airborne dust in a specific minelocation, or area, or room of a workplace.3.1.3 asbestiforma specific type of fibrous mineral growthhabit in which the fibers and fibrils exhibit a pol
29、yfilamentousgrowth habit and possess high tensile strength and flexibility.All materials regulated as asbestos are asbestiform, but not allasbestiform minerals are classified as asbestos. Characteristicssuch as tensile strength and flexibility cannot be ascertainedfrom microscopic evaluation.3.1.4 a
30、sbestos fibera fiber of asbestos that meets thecriteria specified below for “fiber.” Phase Contrast Microscopy(PCM) does not identify fibers unequivocally as asbestos.Under the light microscope, a population of asbestos fibersmay appear as a mixture of fiber agglomerates, fiber bundles(polyfilamento
31、us growth, unique to asbestiform fibers) fiberswith split ends, and single fibers, the relative occurrence andfrequency of each type depending on the situation.3.1.5 aspect ratiothe ratio of the length of a fiber to itswidth.3.1.6 cleavage fragmentsmineral particles, normallyformed by comminution of
32、 minerals, which often are charac-terized by parallel sides and a moderate aspect ratio (usuallyless than 20:1). Non-asbestiform cleavage fragments do notexhibit fibrillar bundling at any level of examination.3.1.7 limit of detectionthe number of fibers necessary tobe 95 % confident that the result
33、is greater than zero.3.1.8 differential countinga term applied to the practice ofexcluding certain kinds of fibers from the fiber count becausethey do not appear to be morphologically consistent with fibersof a specific variety thus modifying the definition of fiber givenbelow.3.1.9 fiberan elongate
34、d particle that is longer than 5.0 m,with a minimum aspect ratio of 3:1, and sometimes alsoclassified as having a maximum width of 3.0 m as this latterdimension may equate to the size of fiber of the density ofmany silicate minerals capable of penetrating the lung. Anasbestos fiber should further ex
35、hibit the asbestiform habit,although analysis of airborne fibers by PCM may not besufficient in itself to determine asbestiform habit.4For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume info
36、rmation, refer to the standards Document Summary page onthe ASTM website.5This standard is available from US Department of Health and Human Services,4676 Columbia Parkway, Cincinnati, OH 45226.6Available from Asbestos International Association, 68 Gloucester Place,London, W1H 3HL, EnglandD72000623.1
37、.10 fibrila single fiber of asbestos that cannot befurther separated longitudinally into smaller components with-out losing its fibrous properties or appearances.3.1.11 fibrousa mineral that is composed of parallel,radiating, or interlaced aggregates of fibers, from which thefibers are sometimes sep
38、arable. A crystalline aggregate may bereferred to as fibrous even if it is not composed of separablefibers, but has that distinct appearance. The term “fibrous” inmineralogy is used to describe aggregates of grains thatcrystallize in a needle-like habit and appear to be composed offibers. Asbestos m
39、inerals are fibrous, exhibiting a specific typeof fibrous habit termed asbestiform. However, not all mineralshaving fibrous habit are asbestos.3.1.12 field (of view)the area within the graticule circlethat is superimposed on the microscope image.3.1.13 habitthe characteristic crystal growth form orc
40、ombination of these forms of a mineral, including character-istic irregularities.3.1.14 personal samplea sample taken by a collectionapparatus (membrane filter) positioned in the breathing zone ofthe subject (near the nose and mouth) such that the collectedparticles are representative of airborne du
41、st that is likely toenter the respiratory system of the subject in the absence ofrespiratory protection.3.1.15 seta group of samples that are collected, submittedto the laboratory, and analyzed for a report that is generated.3.1.16 RIB Graticulean eyepiece graticule specificallydesigned for asbestos
42、 fiber counting. It consists of a circle witha nominal projected diameter of 100 m (nominal area of0.00785 mm2) with a cross-hair having dash lines 5-m longand 0.5-m wide in one direction and 5-m long and 1-mwide in the orthogonal direction. There are also examplesaround the periphery of the circle
43、to illustrate specific sizes andshapes of fibers. This design of the graticule is shown in Fig.A1.1. The graticule is placed in one of the microscopeeyepieces so that the design is superimposed on the field ofview.3.1.17 Walton Beckett Graticulean eyepiece graticulespecifically designed for asbestos
44、 fiber counting. It consists ofa circle with a nominal projected diameter of 100 m (nominalarea of 0.00785 mm2) with a cross-hair having tick-marks at 3m intervals in one direction and 5 m intervals in theorthogonal direction. There are also examples around theperiphery of the circle to illustrate s
45、pecific sizes and shapes offibers. This design of the graticule is shown in Fig. A1.2. Thegraticule is placed in one of the microscope eyepieces so thatthe design is superimposed on the field of view.3.1.18 HSE/NPL7test slidea calibration slide designed todetermine the limit of visibility of a PCM a
46、nd an observer.4. Summary of Practice4.1 The sample is collected by drawing air through a 25-mmdiameter, mixed cellulose ester (MCE) membrane filter, housedin a conductive polypropylene cassette. After sampling, asector of the membrane filter is converted to an opticallytransparent homogeneous gel.
47、Fibers longer than 5 m arecounted by observing them with a Phase Contrast Microscope(PCM) at a magnification between 400 and 500.4.2 Divide the total count into three groups: 1) bundles,fibers with splayed ends, or fibers with curvature; 2) fiberslonger than 10 m or fibers thinner than 1.0 m; 3) all
48、 otherfibers longer than 5 m with a minimum aspect ratio of 3:1.4.3 If 50 % or more of the total fiber count falls into Group1 or 2, then there is an indication that asbestos fibers arepresent in the sample. It is recommended that the sample beevaluated using transmission electron microscopy (Append
49、ixX1) to confirm the presence of asbestos and verify the asbestosconcentration.5. Significance and Use5.1 Users of this practice must determine for themselveswhether the practices described meet the requirements of localor national authorities regulating asbestos or other fibroushazards.5.2 Variations of this practice have been described by theAsbestos Research Council in Great Britain (8), the AsbestosInternational Association (AIA) (RTM 1) (9), NIOSH 7400,OSHA (Reference Method ID 160), and ISO 8672. Where thecounting rules of these methods
