Document 91QDv360Qmx91EndMjQ9eXomR

AIA Health and Safety S Recommended Technical Method Nq PLAINTIFF'S EXHIBIT DUP-2491 REFERENCE ME^ttctdfor the determination of Airborne Asbestos Fibre Concentrations at workplaces by light microscopy (Membrane Filter Method) DUP 0821078 X)U 011503 ASBESTOS INTERNATIONAL ASSOCIATION The prime object ot this Association is to encourage and facilitate the endeavours of its members to eliminate risks to health, occupational and environmental, arising from the use of asbestos. Many countries have official regulations and guide lines which producers, manufacturers and consumers are required to observe in order to prevent such risks occurnng, and progressively the standards stipulated are being achieved. In the course of applying these requirements fnuch practical experience has been acquired, and the interchange of such knowledge and the maximising of control techniques is seen as the pnnciple means by which our members can attain our prime objective. There are still areas where official guidance has not been provided, and others where the problems of applying statutory requirements are new and may appear formidable The Asbestos International Association be*>eves that it has an opportunity and a responsibility to provide what help it can to those concerned with this problem from the wide experience of its members, and has decided therefore to produce a senes of advisory publications for this purpose We wish to remind readers of two important points First, in considering any recommendations in the AIA publications these should be related to the specific legal requirements m the country concerned. It is dearly not possible m such publications to relate the recommendations in every respect to the specific detailed regulations in each state. Nevertheless, the greater part of existing laws on the subject calls for similar forms of control and where no official regulation exists we advise that action should be based on the recommendation of the ILO meeting of experts on the safe use of asbestos. December 1973 Secondly, the development of techniques of control is a continuous process, and we hope that the efforts we are undertaking will help to accelerate the process. Techniques which are recommended have reached their present stage as avesuit of interchange of ideas and practical experience between international experts in the asbestos industry, plant manufacturers, government agencies and many others. It will certainly be necessary regularly to up-date and amend these publications in the light of new ideas and criticisms. All such will be welcomed and v/ill be given full consideration during revision stages. DUP 0821079 Asbestos International Association 68 Gloucester Place, London W1H 3HL. England. Telephone: 01-486 3528 Telex: 298618 INTAG DU 011504 7 September 1979 AIA Health and Safety Publication Recommended Technical Method No.l (RTM1) SUPPLEMENT It is intended that this Supplement will give guidance on the availability of the various items of equipment necessary to implement the At/ asbestos Aist measurement procedures. This Supplement will be reprinted at certain intervals so that information on the equipment can be updated. FILTER -- Membrane filter (mixed ester cellulose) -- 25 mm diameter -- pore width 1.2 pm -- with grid Suppliers: Gelman Instrument Company, Laboratory Products Division, 600 South Wagner Road, Ann Arbour, Michigan 48106. U SA Product-no. 46000 Millipore Corporation, Bedford, Massachusetts 01730. U.S.A. Order-no. RAWG 02500 FILTER HOLDER AND COWL -- Filter holder -- 25 mm diameter Supplier Gelman Instrument Company, Laboratory Products Division, 600 South Wagner Road. Ann Arbour, Michigan 48106, U.S.A. Product-no. 1107 For measurement procedure apply cowi. Cowl for above filter holder is not available. Manufacture is possible according to following sketches: Sketch 1 PUMPS Due to pulsation-free operation and easy portability, preference is given to -- Personal Air Sampler Type C 2000 Supplier Rotheroe 4 Mitchell Ltd., 14 Aintree Road, Perivale. Middlesex, UB6 7U, England Further acceptable pumps are: -- Super Sampler BOX 44 as well as ' BDX30 Supplier Bendix Corporation, Lewtsburg Plant Drawer 831, Lewisburg, West Virginia, U.S.A. 1 Asbestos International Association 68 Gloucester Place, London W1H 3HL, England. Telephone: 01-486 3528 Telex: 298618INTA G or Sketch 2 Filter holder (monitor) -- 25 mm diameter Supplier: Millipore Corporation, Bedford, Massachusetts 01730, U.SA Order-no. M 0000 25 AO (without filter) Order-no. MR WG 025 AO (with filter; specification see Section FILTER) Available from 1 January 1980 For measurement procedure apply cowl. Cowi for above litter holder is not available. Manufactureis possible according to following sketch: Sketch 3 -- Personal Dust Sampler T 13051/2 Supplier C. r. Caisetla 4 Co. LtdRegent House, Britannia Walk, London N1 7ND, England -- High Flow Sampler Model P 2500 Supplier E. I. du Pont de Nemours 4 Co. (Inc.), Fabrics and Finishes Department Applied Technology Division, BrandywineBuilding4300, Wilmington. Delaware 19896, U.S.A. -- MSA-Pump Type G Supplier: Mine Safety Appliances Company, 400 Perm Center Boulevard, Pittsburgh. Pennsylvania, U.SA Catalogue-no. 456058 3r 22 October 1979 DU 011505 DUP 0821080 -- ERRATA Section Contents; Appendix G should read: "Microscope Adjustment Procedure" 4.2.2: Last two lines of 1st Paragraph should read: "cautions presented in sections 4.2.3 and 4.2.4." 4.3.5: 2nd paragraph, 2nd sentence should read: "If the difference is greater than 10 per cent from the initial flowrate, the sample must be rejected." 5.4.1: 12th line (a): "see Appendix G" should be "see Appendix E" 5.4.2: -- 6th line: CjW not GjW -- 13th line should read: "If the Single Sample Durations (tj)..." 5.4.3: Before Example 1 should be inserted (indent from margin): "where Orw (full shift) is the time weighted average concentration for the full working shift. This is equal to the calculated Ctw. provided that representative conditions apply as described in Section 4.2.2." 5.4.3.2, TYPE E. 3.: -- 1st and 2nd lines should read: "Calculate the empirical logarithmic standard deviation (si) ofthe.:." -- both formulas should read: Appendix B: -- Insert at the end of Step 9: "/Vote. Theoretically, the water vapour content in the soap film flow meter air should be taken into consideration in determining the True' flowrate. However, for practical purposes acceptable accuracy is maintained without this correction." -- Change formula in last paragraph as follows: Qc v T 1000 63-4/60 946 ml/min. Acknowledgements: -- CANADA. 3rd address should read: Mr. Jean Marc Lalancette Bureau de L'Amiante 845 ouest. Bout. St. Cyrille, Quebec -- UNITED KINGDOM, 6th address should read: Mr. A. L. Rickards* Turner & Newall Ltd. Asbestos Fibre Laboratory P.O. Box 22 Trafford Park Manchester Ml7 1RU or 5.4.3.2, TYPE E. 4: Formula should read: Ctw - Exp ly + j S.4.3.3: 6.5: TYPE F on next column belongs in its contents to this section First paragraph, 4th line "theoretically" should be changed to "theoretical" DU 011506 DUP 0821081 r-aniMliifa..E; t.Bi- lligai Jj.idi.af WBirgi liiiiiiijilttliiiii - --------- i ii in -- -------------- iiflf'------ - ~ wnwr AIA Health and Safety Publication Recommended Technical Method No.l (RTM1) REFERENCE METHOD for the determination of Airborne Asbestos Fibre Concentrations at workplaces by light microscopy (Membrane Filter Method) CONTENTS 1. PREFACE 2. SCOPE 3. GENERAL METHOD DESCRIPTION 4. SAMPLING 4.1 Terminology 4.1.1 Occupational Sampling 4.1.2 Operator Breathing Zone 4.1.3 Personal Samples 4.1.4 Static Samples 4.1.5 Single Sample Duration 4.1.6 Total Sample Duration 4.1.7 Reference Period 4.1.8 Short Term Samples 4.2 Strategy 4.2.1 General Principles 4.2.2 Sampling Schemes 4.2.3 Total Sampling Duration and , , Number of Samples 4.2.4 Reliability of Sampling Schemes 4.3 Technique 4.3.1 Filter 4.3.2 Filter Holder 4.3.3 Storage and Transport 4.3.4 Sampling Pump 4.3.5 Flow Rate 4.3.6 Acceptable Fibre Loadings on Filters 4.3.7 Blanks 4.3.8 Recommended Single Sample Duration 4.3.9 Sampling Record 5. EVALUATION 5.1 Sample Preparation 5.1.1 Cleaning Slides and Equipment 5.1.2 Filter Sample Cutting 5.1.3 Mounting the Sample 5.2 Optical Requirements 5.2.1 Microscope Equipment 5.2.2 Microscope Adjustment Principles 5.2.3 Eyepiece Graticule Calibration 5.2.4 Microscope/Observer Performance Assessment 5.3 Counting and Sizing Fibres 5.3.1 General 5.3.2 Low Power Scanning 5.3.3 Graticule Field Selection 5.3.4 Laboratory Working Conditions 5.3.5 Counting Criteria 5.4 Calculation of Dust Concentrations and Worker Exposure 5.4.1 Single Values 5.4.2 Time Weighted Average Values 5.4.3 Equivalent eight-hour Exposure Value 6. SAMPLING AND ANALYTICAL ERRORS 6.1 General 6.2 Systematic Errors 6.2.1 Sampling 6.2.2 Analytical 6.3 Random Errors 6.3.1 Sampling 6.3.2 Analytical 6.4 Overall Accuracy 6.5 Limitations of the Membrane Fitter Method and Presentation of Results Appendix A Acetone-TriacetinMounting Procedure Appendix B Flow Rate Calibration nd Corrections Appendix C Measurement of Effective Fitter Areas Appendix D Example of Dust Sampling Record Appendix E Specification of Eyepiece Graticule Ordering Information and Calibration Appendix T- Detection Limit Test Slide Appendix G Microscope Setting Up Details Appendix H Drawings of Various Asbestos Fibres Appendix I Example of Dual Counting Record BIBLIOGRAPHY ACKNOWLEDGEMENTS Prepared by the Dust Measurement Advisory Panel of the Asbestos International Association 1. PREFACE Airborne asbestos fibre concentrations of all types* in the working environment are generally determined by the Membrane Filter Method but experience has shown that this method does not always produce comparable results when used by different laboratories and by different workers. Differences can arise due to variations in sampling, preparation of the slide, optical counting, the calculation of the results and other influential factors. International comparisons of dust measurements for epidemiological studies are only feasible if agreement can be reached concerning all details of the method. The "Reference Method for the Determination of Exposure to Airborne Asbestos Rbre Concentration at Workplaces by Light Microscopy" set out in the following pages is an attempt by the Asbestos Industry to reach international agreement. It is hoped that the new technical information presented in this document will motivate a review of the various national methods so that results from different countries become more comparable. `As defined in the United States Department of the Interior's Bureau oI Mines information circular 1977 tC 8751 `Selected SiScate Miner* and Their Asbestiform Varieties--MfoeratogicM Definltlone and IdertilLeucfvcharacieriaalions'. 2. SCOPE This method describes the equipment and procedures required for sampling and sample evaluation, necessary to assess personal exposure and ttye control of occupational environments to airborne fibres which are known to be predominantly asbestos, tt should be emphasised that in mixed dust situations the presence of otherfibres and fibre-like particles may interfere with the accuracy of counting. It must also be recognised that the use of this method has limitations when applied to samples containing acicular particles (e.g. talc, gypsum) and consequently should not be implemented without a full qualitative understanding of the sample. There are a variety of analytical methods which can be used to develop a full understanding of complex samples, e.g. polarizing light microscopy, electron microscopy, etc. DU 011507 DUP 0821082 AJI particles complying with the defined 4.1.6 Jotal Sample Duration exposure over a working lifetime. Since geometric conditions (see 5.3.5) are. in Total Sample Duration is the sum of sampling must often serve both the absence of other convincing SingleTSample Durations taken during purposes, the sampling schemes information, to be considered as one day (see 4.2.3). presented in this method emphasize asbestos fibres and counted as such, thus ensuring that underestimates of asbestos exposure are minimized. 4.1.7 Reference Period For the purpose of this method, estimates of exposure will be reported on the basis the single day estimate. It must also be recognised that variations in individual working practices result It is also intended that the procedures described in this document should be used for epidemiology. However, for epidemiological purposes additional methods such as gravimetric, electron microscopic procedures, etc. are required to achieve a complete understanding of occupational exposure. 3. GENERAL METHOD DESCRIPTION A sample is collected by drawing a measured quantity of air through a membrane filter by means of a battery powered sampling pump. The filter is later transformed from an opaque membrane into a transparent optically homogeneous specimen. The fibres are then sized and counted using a phase contrast microscope. The result is expressed as fibres per millilitre of air, calculated from the number of fibres on the filter and the measured volume of air sampled. 4. SAMPLING 4.1 Terminology 4.1.1 Occupational Sampling All sampling must be so conducted that the results are representative of the worker exposure to asbestos fibres under typical working conditions for a full shift. Sampling procedures must not interfere with the activities of the worker. 4.1.2 Worker Breathing Zone In order to estimate worker exposure, samples must be taken in the workers' breathing zone. The workers' breathing zone consists of a hemisphere of300 mm radius extending in front of the face, and measured from a line bisecting the ears. 4.1.3 Personal Samples of an eight hour reference period. It is intended that exposure should be calculated as if it had taken place over eight hours. If a worker is exposed to airborne asbestos dust for more than or less than eight hours, the measured concentration during his working periodmust be scaled to relate to an eight hour exposure (see 5.4.3), in order to arrive at an estimate of the workers' equivalent eight hour exposure. 4.1.8 Short Term Samples The Single Sample Duration for a short term sample is less than one hour (see 4.3.8). The short term sample has been defined because it is necessary to reler to that special case. Unless specified as short term, the samples are assumed to be of at least one hour duration. 4.2 Strategy 4.2.1 General Principles Occupational exposure measurements are carried out to meet one or both of two major objectives: 1. To assess exposure relative to an occupational hygiene standard and to enable better control measures to be implemented. 2. To provide estimates of exposure for morbidity and mortality epidemiological investigations. It is well known that dust concentrations vary widely both within a single day and from day to day. Most regulations and hygiene standards require a reliable estimate of exposure on a particular day. It is more useful for epidemiology to spread the sampling effort overa number of days, i.e. less will be known about a single day, but more about the average in a distribution of exposure values within any job group. Consequently.data from one person cannot be assumed to be representative of the total job group. Any transfer of data must, therefore, be validated by appropriate relative measurements. 4.2.2 Sampling Schemes There are a number of different sampling possibilities, some of which are listed for guidance in the following table. As they vary in the degree of usefulness and precision in estimating exposure, the table must be interpreted in association with the qualifying conditions and cautions presented in sections 4.2.3, 4,2.4, and 4.2.5. In planning a sampling scheme, it is important to determine: the Estimation Period during which the exposure is estimated, the total Sample Duration, the number of samples. To assess a worker's full shift exposure every effort must be made for the samples to relate to a whole working day. Care must be taken to ensure that the sampling period is not biased by abnormal conditions. Short term samples shouldbe taken atrandom (statistically) throughout the whole working day. If samples cannot be selected from the entire working day, the measurement results are valid only for the duration of the period from which Ore measurements were selected. However, relative measurements and reliable professionaljudgement can sometimes be usedto make inferences about concentrations during other portions of the day. Reliable knowledge concerning the operation is essential to make such extrapolations. Personal samples are taken within the workers' breathing zone. Usually the filter is fastened to the jacket lapel of the worker with the cowf (see Supplement) pointing downwards. The worker carries Sampling Scheme No. of Samples per shift Total Sampling [Duration the pump in a belt or a pocket. LONG TERM 4.1.4 Static Samples 1 Static samples are samples taken at Full-shift consecutive samples) fixed locations. They are not recommended for the measurement of Type A Type B 2 ormore 1 approximately full shift approximately full shift. personal occupational exposure to asbestos dust. Point sources create considerable concentration gradients thus causing the Partial-shift consecutive sample(s) Type C 2 ormore Type D 1 2 hours or greater 1 hour or greater results of static samples to vary considerably overshortdistances. However, static sampling SHORTTERM can be useful if the dust is proven to be uniformly (Sstributed over large areas. 4.1.5 Single Sample Duration Single Sample Duration is the actual time Random Samples Type E 5 or more taken randomly throughout 1 hour or greater the working day during which a single sample is Systematic Samples collected. Type F 1 or more plus continuous relative 1 hour or greater This duration is usually dependent upon measurement, or 2 or more taken analytical requirements (see 4.3.8). during each separate phase of a cyclical operation DUP 0821083 DU 011508 UKi 4.2.3 Total Sampling Duration and Number of Samples Sample duration is influenced primarily by the reason for sampling, the level of fibre concentration to be measured, the concentration of non-fibrous dust and the requirements of the analytical method. This may result in more than one single sample being required. The total sample ... approach should not be used indiscriminately, particularly by persons not completely familiar with the process. Nor should it be used to estimate time-weighted-average exposure unless the results are verified by continuous relative measurements or other methods (see 4.2.2). duration should never be less than one hour. 4.3 Technique Sections 4.3 6 and 4 3.8 detail acceptable -4.3.1 Filter minimum and maximum loadings ot fibres on Membrane filters (mixed esters of the filter, which dictate the range of possible ~~ cellulose or cellulose nitrate) of 1.2 sampling times for different airborne fibre micrometre pore size with printed grids concentrations. . and a diameter of 25 mm should be used. Samples of short duration maybe necessary if -- See Supplement for specifications of high background levels of particulate matter suitable filters. or fibres are present which woukj prevent accurate analysis. 4.3.2 Filter Holder It is necessary to use an open faced 4.2.4 Reliability of Sampling Schemes filter holder fitted with a protective cowl The main strengths and limitations of the - (see Supplement). various sampling schemes, types A to F listed before, are as follows: The cowl helps to protect the filter from accidental contamination. A metallic cowl is Type A Sampling Scheme (two or preferred to a plastic one because of the more samples covering the full possible risk ol fibre loss due to electrostatic working shift) permits the most reliable charge. Filter holders must be thoroughly estimate of exposure to be made. washed between use. When several samples are taken, the Due to the design of the filter support average of the errors is usually less than the single (percentage) error in utilized in some filter holders a secondary supporting membrane should be used. a single full shift sample. Sporadic The purpose of this secondary membrane is gross errors such as miscalculations, to ensure an even distribution of air passing contamination, incorrect sample through the primary membrane. timing, etc. are more likely to be detected by type A than type B. 4.3.3 Storage and Transport Fixatives must not be used. NOTE: Systematic errors must still be Experience has shown that fixing fibres to the taken into account in the normal filter surface with cytological or other types ol manner -- e.g. flowrate inaccuracy, fixatives is unnecessary and should not be etc. done. Type B Sampling Scheme (one full shift sample) is not as reliable as type A because gross errors can escape detection unless evidence Filters should be transported in closed holders which should only be opened immediately before use and sealed immediately after. from previous sampling is available on which to base a judgement. Type C Sampling Scheme (two or more samples covering part of the full shift, i.e. two or more hours but less than full shift) can be satisfactory if the partial shift is representative of the full shift Type D Sampling Scheme (one sample, one or more hours but less than full shift) similar to type C except that gross errors may escape detection. Type E Sampling Scheme (5 or more short term samples, taken randomly throughout the fun shift) may give an acceptable indication of exposure but is generally more wasteful of resources and is the least precise of the above schemes. Note that an even poorer estimate results when the "average* dust concentration An alternative is to transfer the filter to a petri dish in the following way: In a dust-free area, using forceps, carefully remove each used filter from its holder taking care to grasp it on its unexposed edge. Place the filter, dust side up, in a plastic petri dish or similar container. Fasten the filter to the bottom of the dish with one or two pieces ol adhesive tape attached to the unexposed edge. After transporation, the filter can be removed easily from the dish with a surgical scalpel. Pack the filter holders or petri dishes into a rigid container with sufficient soft packing material to prevent both crushing and vibration of the filter. Samples should be unambiguously labelled and caution is necessary to ensure that filters cannot be accidentally reused. The filters should not be marked for this purpose because of the risk of damaging the filter. increases or decreases markedly throughout the day. This scheme should be applied with caution. Type F Sampling Scheme (several short term systematic samples taken during each separate phase of an operation) can be used by experienced industrial hygienists to characterise a workplace. This 4.3.4 Sampling Pump A portable battery operated pump must be used for personal sampling. The capacity of the battery must be sufficient to operate continuously over the chosen sampling time. The flow must be free from pulsation. As a minimum and tentative cntena there must be no visible vibration of a rotameter float when this flowmeter is connected to the filter holder. Although some pumps are equipped with puls Mon dampers, an external damper may have to be installed between the pump and the filter. Never run the pump without inter. Connecting tubing must be constrictionproof and the connections leakproof. 4.3.5 Flow Rate The flowrate should be adjusted to one litre/minute, i.e. approximately 4 cm/s face velocity. The flowrate should be checked at least before and after sampling. If the difference is greater than 10 per cent, the sample must be rejected. If an external flowmeter is used to determine the flowrate of the pump, care must be taken to ensure that the flowmeter does not cause unknown changes to the flowrate. Measurement of the "sampling train" flowrate using a soap-film flowmeter, with and without the external flowmeter, is one satisfactory method of determining any change in flowrate. The flowmeter used should be able to measure flowrate to an accuracy within five per cent of the true flow (95 per cent confidence limits). See Appendix 8 lor flowrate calibration. 4.3.6 Acceptable Fibre Loadings on Filters Minimum Loading The minimum filter loading should exceed 50 fibres/mm2 (i.e. approximately 40 fibres/100 WaltonBeckett graticule areas). In special circumstances (e.g. when an indication of concentration with low precision is acceptable) it is permissible to lower the acceptable fibre loading to 20 fibres/mm* (i.e. approximately 15 fibres/100 Walton-Beckett graticule are- The lowering oftheacceptablefibreloading gives, atbest, barely acceptablecoefficients of variation. The limitations as described in section 6.5 should also be considered when measuring very lew fibre concentrations. Maximum Loading Experience showsthatthe filterloading should not exceed a maximum of five fibres/graticule area (average value for all counted fields) for the majority of sampling situations. This may needto be reducedtoan average of aboA one fibre per graticule area when mixed ckrsts or agglomerates am present, and can sometimes be doubled when only Fibres are present. Average filter loadings exceeding 10 fibres/graticule area should be rejected. DU 011509 DUP 0821084 4.3.7 Blanks Fof each batch of fitters used for sampling, and for every 25 filters in the batch, select one unused filter which has been subjected to the same treatment as for norrrtal samples, but without having had air drawn through it, or been attached to the worker. If this "blank" yields fibre counts greater than three fibres/100 graticule areas, the entire sampling and analytical procedure should be examined carefully to find the cause of the contamination. When the blank count exceeds three fibres/100 graticule areas, and also exceeds 10 per cent of the actual sample fibre count/100 graticule areas, the samples represented by the olank are not considered acceptable for assessment of worker exposure. However, the determination may still be useful for indicating compliance with the hygiene standard (e.g. if the estimated exposure is less than that permitted by regulations even with the contamination then this is a conservative estimate of compliance). For example -- the fibre count of a blank filter was 15 fibresflOO graticule areas (i.e, 0.15 fibres!area) while the sample yielded 108 fibres in 90 graticule areas (i.e. 1.20 fibres/area). Blank count % _ _J5 x 1QQ 12.5% Sample count 120 As this percentage exceeds 10 per cent, the sample is rejected. Furthermore, because the blank count exceeded three fibres/ graticule area the cause of contamination must be found and corrected. 4.3.8 Recommended Single Sample Duration Taking into account the filter loading considerations as detailed in section 4.3.6, the sampling duration for each sample may be determined by application of the following simple formula: a Cexp. r t = Single Sample Duration L = required filter loading in fibres/ graticule area A = effective filter area mm1 a = graticule area mm* r = flow rate ml/min. Cexp. * average ftore concentration expected to occur during the Single Sample Duration (fibre/ml) To provide guidance in the selection of Single Sample Duration, the following table lists recommended durations based on two fibres/graticule area. If it is not possible to use these values, the minimum and maximum durations allow a choice to be made whilst still remaining within the constraints of 4.3.6. Cexpected fibres/ml 0.5 1 2 5 10 20 Single Sample Duralkm Irecommended(') !maximum(3) 3 hours 1.5 hours 45 minutes 20 minutes 10 minutes 4 minutes' 8 hours 4 hours 2 hours 1 hour 30 minutes 10 minutes tmimmumH 40 minutes 20 minutes 10 minutes 4 minutes* 2 minutes' 1 minute' Wore.- (1) 2 fibresfgraticule area (2) 5 fibresfgraticule area (3) 0 4 fibresfgraticule area equivalent to 50 tibreslmm3 `A measured concentration of less than 20 fibresiml should be discarded because it has little significance if the sampling time is less than 10 minutes. Sampling time should be measured accurately. The timers or counters installed in some pumps are no( always reliable. 4.3.9 Sampling Record All data necessary for the determination of the fibre concentration must be recorded, along with the sampling details. Furthermore, as much data as is available, which can be of value for epidemiological studies, should be included (see Appendix D). 5. EVALUATION 5.1 Sample Preparation 5.1.1 Cleaning Slides and Equipment Clean conditions should be maintained at all times. A dirty preparation area may result in sample contamination and erroneous results. Clean slides with lens tissue or industrial paper tissue and lay them on a clean surface, e.g. lens tissue sheet. It is good practice to clean each coverslip with lens tissue immediately before use to ensure that the surfaces are tree from contamination. Wipe scalpel and forceps with lens tissue andplace them on a clean surface, e.g. lens tissue. When mounting a series of filters, the mounting tools must be wiped clean before dealing with each sample. 5.1.2 Filter Sample Cutting Mounting of the total filter is preferred. If it is necessary to cut the filter, all cutting should be done with a scalpel using a rolling action. Donot use scissors. Itis recommended that the smallest piece mounted be wedge-shaped, approximating to one quarter or one third of the filter. 5.1.3 Mounting the Sample For mounting use the acetone-triacetin method only as described in Appendix A. WARNING Acoton* mounting should be carried out only In a fum* hood or fuma cupboard. On no occasion should it bo used in the vicinity of sn open ftamo. 5J2 Optical Requirements 5.2.1 Microscope Equipment It is recommended that the following specification be used to select a microscope suitable for asbestos dust counting. Because microscopes with identical "specifications'' can give quite different performances, it is necessary that the performance of proposed and existing microscopes be assessed by means of "Detection Limit Test Slides" (see Appendix F). it is also important that newcomers consult with experienced workers before selecting microscopes for asbestos dust determination. - Light Source -- Koehler illumination is required. It is preferable for the illuminator to be built-in but an external tamp with a plain mirror can be satisfactory. A variable light intensity control is necessary lor both methods of illumination. - Substage Assembly -- An Abb6 or achromatic phase-contrast condenser incorporated into a substage unit is required. There must be a means of centring each condenser annulus with respect to the phase plate in me corresponding objective and a means of focussing the condenser. - Stage -- A built-in mechanical specimen stage fitted with slide clamps and x-y-displacement is required. - Objectives -- A rotating nose-piece fitted with I0x and 40x parfocai phase-contrast achromatic objectives is required. The 40k objective must have a numerical aperture (NA) of 0.65, achromatic, ft should have a phase ring of not less than 65 per cent and hot greater than 65 per cent absorption. Either positive or negative phase-contrast is suitable. - Eyepiece -- Binocular eyepieces of the compensating type are recommended. They should be chosen to give a total magnification of between 450x ana 500x, preferably 500x. At least one eyepiece must permit the insertion of a graticule and preferably be of the focussing type. The use of body magnification changers is not recommended. - Graticule -- The graticule recommended for this method is the Walton-Beckett circular eyepiece graticule. tts actual diameter wnen using the 40* phase objective and an appropriate eyepiece should be 100 micrometers phis or minus 2 micrometers. See Appendix E for graticule specification, source ofsupply and ordering information. DUP 0821085 DU 011510 Accessories - CENTRING TELESCOPE or Bertrand Lens is essential tot checking that thephase nngs in Vie condenser are centred with respect to those m the objective. A green fitter is necessary to ensure the best phase contrast conditions because the optics are designed for this wavelength. - STAGE MICROMETER -- Must be subdivided into 10 micrometer htervals and preferably be one millimeter long. Microscope Slides -- Should be of the best Qualify. - COVERSUPS of thickness to which the microscope rs designed (normally 0.17 mm thickness) are essential. Incorrect coverslip thickness will detract from the quality of the final image. 5.2.2 Microscope Adjustment Principles Follow the manufacturer's instructions while observing the following guidelines: - The image of the light source must be in focus and centred on the condenser iris or annular diaphragm for true Koehler illumination. _ The object for examination must be in focus. - The illuminator field jris must be in focus, centred on the sample and opened only to the point where the field of view illuminated. - The phase rings (annular diaphragm and phase shifting elements) must be concentric. - The eyepiece graticule must be in focus. Formore detailedinformation see Appendix G. Microscope adjustments must be a daily routine. 5.2.3 Eyepiece Graticule Calibration Each combination of eyepiece, objective and graticule must be calibrated with a stage micrometer. Should any of the three be changed, the combination must be recalibrated. For some microscopes, calibrations will change for observers with different interpupillary distances (see Appendix E for eyepiece graticule calibration procedures). 5.2.4 Microscope/Observer Performance Assessment Because past experience has shown that significant differences in counts occur due to differences in microscope quality, setting up and cleanliness, it is necessary that laboratories following this method should maintain contact with the AIA. As mentioned in section 5.2.1, sets of detection limit test slides are available which will assist in the regular assessment of microscope and observer performance. A practical detection limit relative tc the test slides. Code-No. 5 or 6 (0.26 rr 0.22 pm spheres) should be achieved. Exchange of microscope slides for comparison with experienced laboratories will help to ensure that valid results are being generated. 5.3 Counting and Sizing Fibre* 5.3.1 General Airborne asbestos dust collected on membrane filters appears in a wide variety of forms ranging from simple single fibres to very complex configurations of fibres or aggregates. When presented with these, the microscopist could experience difficulty in defining and counting the fibre content of a dust sample. The following : notes (and drawings in Appendix H) have been prepared to assist and guide the observer in the assessment and interpretation of asbestos dusts collected on membrane filters. 5.3.2 Low Power Scanning With a total magnification of 100 x to 150x (i.e. lOx objective) scan the entire filter area. The margin normally covered by the filter holder gasket should be free of dust and fibres. All viewing fields should have similar appearances with respect to total dust loading. If the observed fields show marked differences in loading, gross aggregation of fibres or dust, the filter must be rejected. . 5.3.3 Graticule Field Selection After a satisfactory low power scan, change the microscope objective to 40 x - phase and focus on the dust plane. Ensure that the phase rings remain concentric. While most of the fibres and dust will be found on the upper surface of the filter, it will be necessary to focus below (say up to 10 micrometers) and slightly above the surface. When counting and sizing, constant use of the fine focus is necessary because of the small depth of focus of a 40x objective (i.e. two to three micrometers). Counting fields should be chosen at random throughout the entire area of the filter or filter segments. If the grid of a filter obstructs the view, move the stage to another field. Do not count fields that lie within 3 mm of the filter edge and within 2 mm of the cutting line. 5.3.4 Laboratory Working Conditions The working practices and the working "environment in a laboratory may influence systematically the accuracy of the actual counting. Some differences may appear when inter-laboratory comparisons are made which are due merely to different laboratory Fighting conditions, different seating and computing arrangements, etc. Different practices of recording data may also cause some disagreement between the counters, due to the rate of fatigue of the eyes. The detailed writing of data involves the re-focussing of ihe eyes after each field, whereas continuous registering wth electrical or mechanical counters involves only a single p viod of continuous concentration. This problem of ergonomics briefly stated here can only be dealt with when all the other parameters of the method are fixed. 5.3.5 Counting Criteria - Designate all particles having the following geometnc dimensions as fibres: lengthgreaterthanfivemicrometers, and diameter less than three micrometers, and length to diameter ratio greater than 3:1. Accuracy is important, and full use should be made of known dimensional standards. Estimate the length of curved fibres along the curve of the fibre (i.e. true length). - When examined microscopically, asbestos fibres fail into four basic groups as follows: Single fibres can be directly classified according to their geometric dimensions. Split fibres are counted as one fibre, according to their geometric dimensions. The diameter of a split fibre is measured across the compact part of the fibre, not across the split part. Grouped fibtes are counted individually whefe-individual fibres can be distinguished. Where they cannot be distinguished as individual fibres they are counted as equivalent to one fibre if the bundle has a total diameter less than three micrometers. Fibres attached to particulate matter are counted as one fibre if the diameter of the particle is less than three micrometers, otherwise not. Refer to Appendix H for full details. - The counting rules are based on the principle of counting fibre ends visible within the graticule area and dividing by two to obtain the number of fibres observed. Count any fibre that Ties entirety within the counting area. Count as 'hall fibre' any fibre with only one end lying within the counting area. If a single curved fibre has each end inside the counting area having crossed the area twice, each end is stH counted as half a fibre. - If more than one eighth of the counting field contains an agglomerate of fibres and/or dust, reject the field and select another. Always record such occurrences. - Count as many fields as are necessary to give a total fibre count of 100 A minimum of 20 fields must be counted, even if more than 100 fibres have been observed. It is not necessary to count more than 100 fields. However, errors will be large when the minimum fibres or fields are not counted (see 4.3.6 for minimum loading requirements). - All relevant information must be recorded (see Appendix I for an example of a dust counting form). DUP 0821086 DU 011511 5.4 Calculation of Du*t Concentration and Worker Exposure When the following calculations are applied, the limitation imposed upon the data by the sampling and fibre counting methods must not be disregarded. Results should not be interpreted or reported with false precision. 5.4.1 Single Values The fibre concentration for each Single Sample Duration is determined according to the following formula; c -* , N . 1 , ! an r t 0) where: c - concentration (ffores/ml) N - total number of fibres counted n - number of graticule areas observed A effective filter area (mm1) (see Appendix C) a " graticule counting area (mm1) (see Appendix G) r - llowrate of air through filter (mt/min) t = Single Sample Duration (minutes) 5.4.2 Time Weighted Average Values When several samples of different sampling durations are taken calculate the time weighted average values from the single values as follows: c Ci <i citi + C2t2 + ... + cnt,, (2) TW's:ti "ti + t2+ ...+tn Gjw " time weighted average concentration (fibres/mO Cj - single value of concentration (fibres/ml) t] - Single Sample Duration (minutes) 2-tj - TotaJ Sample Duration n - total number of samples If the Single Sample Duration (tj) referred to above are of equal duration, then equation (2) is simplified as follows: Cjy, ~^Cl - C1 + c2 + ... + n nn (3) 5.4.3 Equivalent eight hour Exposure Value If the shift of the worker exposed to airborne asbestos dust is more than or less than eight hours, the average concentration during the full shift must be multiplied by a factor (f) to yield the Equivalent eight hour Exposure Concentration (Ceq), as follows: ( m M shift time (hours) 8 hours Ceq - f.Cjw (Wl shift) (5) Example 1: Daily shift duration 12 hours Time-weightid-average for the Ml shift of 1.2 fibres/ml. Using equation (4): f -- -- -- 1.5 6 Using equation (5): Ceq - 1.5 x 1.2 1.8 fibres/ml Example 2: Daily shift duration of 5 hours" with a corresponding shift average of 12 fibres/ml. Using equation (4): f - - - 0.625 8 Using equation (5): Ceq - 0.625 x 12 - 0.8 fibres/mi "This means that the worker was known to have zero exposure to asbestos outside of h 5-hour shift. 5.4.3.1 Calculation of "Ceq" for various Sampling Schemes Types A, B, C and D 1. Calculate single value concentration(s) for the sample(s) using equation (1). 2. Calculate time-weighted-average (Cyw) concentration using the above single value(s) and respective Single Sample Duration(s) in equation (2) (or (3) if applicable). 3. Calculate Ceq by using the procedure at 5.4.3. 5.4 3.2 Calculation of "CecC for Sampling Scheme E Type E When 5 or more short term samples are taken randomly throughout a full shift, the time-weighted-average concentration can be estimated as follows: 1. Calculate the natural logarithm of each concentration: yj = In Cj, i.e. yi = In ci, y2 = In C2 and so on. If any concentration is less than 0.1 fibreWml, replace it with 0.1 fibres/ml for the above calculation. 2. Calculate the arithmetic average of the logarithmic concentrations: - T. Yi = yi + Y2 +... + yn 3. Calculate the empiral logarithmic standard deviation (se) of the logarithmic concentrations (sampling/ analytical random errors and environmental fluctuations are included) 4. The estimate of the average airborne concentration is calculated as follows: Cjw Note: The above calculations are used because available evidence shows that random intra-day variations are best described by a log-normal distribution. 5. Using Cyw from above, calculate Ceq as in section 5.4.3. 5.4.3.3 Calculation of "Ceq" for Sampling Scheme F Type F 1. Calculate single value concentrations for the samples using equation (1). 2. Calculate the times (Tj) for each individual working phase ensuring that the sum of these phase times equals a full shift. 3. Calculate the time-weighted-average concentration using the phase times (Tj) instead of the Single Sample Duration (tj) in equation (2). 4. Calculate Ceq as in Section 5.4.3. Note: The above calculations for the different sampling schemes do not imply identical reliability in me estimation of me equivalent 8 hour exposure value (Ceq), (see 423 and 43.4). 6. SAMPUNG AND ANALYTICAL ERRORS 6.1 General Errors introduced into the estimation of airborne asbestos dust comprise sampling and analytical errors, each of which has a systematic and random component. The application of standard procedures and a reproducible routine is the only way of controlling most of the many sources of error inherent in the membrane filter method. The following list describes some of the common sources of error. 6.2 Systematic Errors 6.2.1 Sampling - Flowrate. - Sampling time. - Non-representative or biased sampling. - Contamination -- deliberate or accidental. 6.2.2 Analytical - Effectk/e filter area. - Counting area. - Filter mounting. - Microscope and observers. - Contamination. 6.3 Random Errors 6.3.1 Sampling - Flowrate variability. - Random fluctuations of the airborne dust cloud. 6.3.2 Analytical - Fibre distribution on the filter. Non-random deposition of dust on the filter leads to gross errors, toe magnitude of which cannot be estimated. Twenty or more fields must be counted to ensure that minor divergence from randomness does not bias the result. - Poisson errors. As only sma samples ol the fibres deposited on the filter are counted, errors anse in the estimation of the totalnumber offibres on the entire filter face. Theoroticaty, the Poisson distribution defines thevariation Infibre counts resulting from viewing randomly selected counting fields on the fiher. tie minimum of TOO fibres is counted, and Ifa Poisson distribution were appropriate to the counting results, the relative standard deviation of the fibre counts would be 10 per cent It has been shown experimental? that the actual distribution offibre counts can depart from that of Poisson, In which case the standard deviation may be greater. DUP 0821087 DU 011512 -.... ..........~yjj liifl, iaIiSFiffn" yfiiii 6.4 Overall Accuracy Because of the nature of the membrane filter method, it is not possible to know the "true" airborne fibre concentration of a given dust cloud. For this reason it is not possible to assess the likely accuracy of the method. Even the precision (or repeatability) of the method is difficult to quantify because of systematic errors which tend to arise both intra- and inter-laboratory. Taken as a whole by "randomly" selecting observers and laboratories, these systematic errors take on a random nature such that it may be possible in future to provide estimates of empirical precision (i.e. the closest approach pos ible to a statement of accuracy for a method with no known "true" values). Much <.Jork has been done in an attempt to arrive at these estima'es, and to date onty partial conclusions have been reached. One of these describes the theoretical Pnisson distribution (see section 6.3.2) as contributing a 95 percent confidence interval of.20per centlora totalof iCXI fibres counted, up to about 35 per cent for only 40 fibres counted in 100 graticule areas. Other sources of random and systematic errors add significantly to the uncertainty in estimating the airborne asbestos dust concentration. 6.5 Limitations of the Membrane Fitter Method and Presentation of Results With the parameters specified in this method, i.e. one litre/minute flowrate and a minimum filter loading of 15 fibres per 100 graticule areas, the theoretically lower detection limit for an eight hour sample is 0.02 fibres/ml; however, the practical limit is much higher. It is' generally accepted that blank, unused filters can frequently give a reading of several countable fibres per 100 graticule areas. These "fibres" may be unidentified contaminents on the filter, or artifacts from the clearing process which have the appearance of fibres. It must be recognised that neither counting more fields nor increasing sampling duration overcomes the problem of background dust, when asbestos is a minimum constituent in the overall dust cloud. There is at present insufficient information available to determine at what level the reliability of the method becomes so poor that results have little meaning. It is clear that this will not be a single value, but will be a range depending upon at least the relative and absolute fibre concentration. There appears to be general agreement amongst those experienced in the field, that these limits lie somewhere in the range of 0.1 to 0.5 fibres/ml depending on a variety of conditions. In view of this situation, and the inherent variability of the method, all calculated yalues of less than 0.1 f/ml should be reported only as "less than 0.1 fibre/ml". All higher values should be rounded off to the first decimal place, aid to two significant figures. Appendix A Acetone-Triacetin-Mountlng Procedure WARMING Acetone mounting should be carried out only in a fume hood or fume cupboard. On no occasion should it be used in the vicinity of an open flame. - A hot plate, or waterbatti. or heating mantle, complete with energy regulator, or even an infant's bottle warmer can be used to heat the acetone. An effective method is an infra-red lamp. The lamp can be moved closer to, or further from the flask so fhai the acetone can be boiled gentty. - As illustrated in the diagram below, it is advisable to use a simple condensing column to ensure that a bare minimum of acetone vapour escapes. When not in use, the acetone vapour outlet should be plugged. - Heat the acetone to boiling and wait until a moderate quantity of acetone vapour is emerging from the outlet. - Place Ihe filter dust side up on a clean microscope slide at room temperature -- electrostatic forces usually keep the titter on the slide. - Ensuring that no liquid acetone drops on the litter (by wiping the outlet periodically with a tissue), hold the slide with clean forceps directly in the acetone vapour Stream approximately 15 to 25 mm from the outlet for three to five seconds. At the same time move the filter slowly across Ihe outlet to ensure even coverage until the filter is transparent. Too little vapout will fail to render the filter transparent, while too __ much vapour (especially drops of liquid -- acetone) will destroy the filter by dissolving it or shrinking it beyond use. The slide must ___ not be prewarmed, as the acetone vapour must condense on the slide for correct clearing, - Using a hypodermic syringe with a 22 gauge needle, place one to three drops of glycerol triacetate (Triacetin) on the acetone cleared filter. To avoid the development of a "skin" over the Triacetin, immediately lower at an angle (see diagram below) a clean coverslip onto the Triacetin. The coverslip shoutd not be pressed onto the membrane. - Too much Triacetin (as indicated by excess liauid emerging from the edges ot the c . erslip) can cause the outside edge of the filter eventually to disintegrate to some degree. Insufficient Triacetin will result in uneven clearing of the granularity left from the acetone vapour -.le.-ring. Further, the refractive index ofthe mounted sample wilt not be suitable for optimum visibility of very fine Chrysolite fibres. - Heating the cleared filter to approximaiely 50*C lor fifteen minutes accelerate-- the clearing process and enables analysis to proceed almost immediately thereafter. Otherwise it is necessary to delay counting for up to 24 hours until tne entire litter has - dissolved under the action of the Triacetin. The finished product w;a be stable, will not disintegrate, nor be subject to particle migrt .ion. - It is desirable to pant nail polish, or similar lacquer around the edge ot the coverslip if Ihe slide is to be kept indefinitely. Staple Condensing Column Appendix B Row Rata Calibration and Correction* Internal and external flow meters must be calibrated with a primary calibration device. One suitable calibration procedure makes use of a soap film flow meter. The (low meters described in this section are of the variable area type (i.e. "rotameters"). 1. Choose an accurate burette (or similar) of 300-500 ml capacity. Attach a tube to the bottom of the burette, and then clamp it in an inverted vertical position into a stand. 2. Set up the sampling pump complete with connecting tube, filler holder and filter as that used in the field. 3. Connect the soap film flow meter. Ensure that the system is leakproof. It is advisable to rinse the burette thoroughly in water immediately prior lo the test--this removes accumulated detergent and also assists in wetting the inside of the burette. 4. Switch on tiie ptxnp and adjust the flowrate to 1 l/min. according to the internal flow meter (if fitted). 5. Partly fill a beaker or petri dish with water plus the minimum amount of detergent necessaty to permit bubbles to be formed. 6. Pv momentarily placing the beaker against the bottom of the soap film flow meter create a bubble such that it w travel the. entire length of the burette without bursting. DU 011513 DUP 0821088 7. With a stop watch, measure accurately the time that the bubble requires to traverse the tube between its extreme graduated _ ends. 8. Repeat steps 6 and 7 at least twice, or more, until good repeatability o< the times is achieved. 9. Average the times, and calculate the true flow (Qc) as follows: Qc - V X Where Qc - True volumetnc flowrate (ml/min.) at calibration conditions. V - Volume ol burette (ml), X Average time required tor bubble to traverse the tube (minutes). 10. If the external or Internal rotameter is used under different temperature conditions than those during calibration, it is generalty rat possible to calculate the different flowrate that will inevitably result As all air sampling measurements are concerned only with volumetric flowrate (i.e. flowrate measured and expressed at the prevailing temperature and pressure) and not mass flowrate (i.e. flowrate corrected to standard temperature and pressure conditions), recalibration of the pimp flowrate is essential if it is operated under conditions substantially different to those of calibration. Substantial implies a difference in altitude or temperature by more than 500 m or 15*C respectively compared to the calibration conditions. For field calibration, whilst a 1 litre soap film flow meter is preferred, a 500 ml unit is more convenient and has been found satisfactory. Example: During the calibration of a pump with an internal flow meter a soap film flow metor of 1000 ml volume gave an average of 63.4 seconds for the bubble to traverse its length. What is the flowrate under these conditions? Using the equation in this Appendix: c "4" 6OT 946mWWn- The flowrate, under the temperature and pressure conditions as stated above was 946 ml/min. Appendix C Measurement of Effective Filter Area Oiie convenient way in which to determine the area of the dust deposit (i.e. the effective filter area) is as follows: 1. Place a small quantity of darit coloured dust (e.g. carbon, cement or road dust) into a 2 to 5-litre container with a Kd. 2. Shake the container, remove the lid and draw air through a membrane filter and its holder until the airborne dust in the container forms ar. obvious deposit on the filter. 3. Remove the filter from the holder, and mount onto a microscope slide in the rormal manner as described in the Reference Method. 4. Measure at least tour different diameters of the resultant dust spot to within 02 mm. Amongst other methods, mictoprojection measurement, or the use of microscope object stage verniers have been found satisfactory. 5. Provided that the measured diameters differ by no more than 1 mm, a simple arithmetic average is sufficient to provide a good estimate of the effective litter diameter. 6. At least three individual filters must be prepared and measured as desenbed above to give assurance that Tie finally calculated area is sufficiently accurate. 7. Provided that the three litter diameters diffei no more than 1 mm, an arithmetic average should be taken and th6 area cak. r*ed in the usual manner. This area is then the Effective Fitter Area to be used for calculations in this method. 8. If steps 5 or 7 produce differences greater than 1 mm, close attention should be paid to the sampling of the dust or to the filter clearing technique. 9. It is necessary to repeal the measurement of the effective filter area if the type of titter or holder, or if any aspect relating to filter clearing is changed. 10. It is advisable to repeat the entire measurement procedure every 12 months to ensure that the correct effective filler area is known. Appendix D Dust Sampling Record All data necessary for the determination of the fibre concentration must be recorded in a sampling record. Furthermore as much data as available which can be of value for epidemiological studies should be included. Sampling Details Instrument Type and No. Flowrate, initial, intermediate and final Duration Sampling scheme used Date, Hour Sampled by Sampling Place Details Designation Harmful substances -- types of asbestos, quartz, etc. Brief description of working process Variable parameters which can exercise an influence on dust formation Work practices ee Working conditions: normal abnormal Material: type, size, condition, etc. ee Airflow: worker in dust airflow yes/no obvious influence on adjoining working places e Methods of dust control Exhaust ventilation ee Other methods Visual impression e Number of employees for which the measuring value is representative Persona) protection yes/no Type: Hours per shift e Days per waek See opposite for Dust Sampling Record Appendix E PARTI Specifications of Eyepiece Graticule, Ordering Information and Calibration The Walton/Beckett" graticule described in this method is available from Graticules Limited, Sovereign Way, Botany Trading Estate, Tonbridge. Kent England. TN9 1RN. The desired diameter (D) of the circle (100 2 micrometers)and the overall diameler of the glass disc should both be specified in m.llimetres when ordering. The graticule can be referred to by the Graticules Ltd. Reference No. G22. The following procedure is one of several methods for determining the diameter (d) ol the circular counting area. 1. Insert any available graticule into the eyepiece and focus so that the graticule grid is sharply in focus. 2. Set the appropriate interpupiflary distance, and if applicable reset the binocular head adjusfrnent so that the "tube" length (and thus magnification) remains constant. 3. Ensure that the 40 x phase objective is in place, and that the magnification changer position (if used) is known and recorded. 4. Place a stage micrometer on the microscope object stage and focus the microscope onto the graduated lines. 5. Measure the overall object length (Iq) of the graticule grid using the stage micrometer. 6. Remove the graticule from the microscope and measure its actual overal grid length (la). This can be dene by using a stage fitted with verniers. 7. Use the following equation: --la . ,,D - d - diameter to be specified b It is also necessary to measure the overall diameter of the glass disc. Example: Step 5 produced an object length of a Porton graticule of 108 micrometers. Step 6 produced an actual length of 4.50 mm Step? 4J0mmx01- 0.108 mm 4,17 trim For this example the graticule diameter was found to be 17 mm. Thus a 17 mm diameter. Type G22 "Walton/Beckett" grabcuta of circle diameter 4.17 mm should be specified tor the above example. To expedite manufacture of `made to order" graticules so as to avoid delay and keep down prices, graticules should be ordered in bulk if at alt possible. Graticules Limited have stated that a number of graticules requested on a single order can be invoiced separately to individual companies, and delivered separately to the same or any other set of addressee. PART 2 Calibration of Eyepiece Graticules 1. Obtain a stage micrometer, preferably with a scale having two or 10 micrometer divisions and place on the object stage of the microscope. 2. Make sure interpupiftary distance of eyepieces is set correcdy. 3. Note the objective magnification and any intermediate magnification used. 4. Focus the microscope onto the graduated marks of the stage micrometer. DUP 0821089 DU 011514  ~ I< S.; 1 i:lIiiisS5:W,>, ,La;u.; M^rtr^tuUm iaamiaiU^i^liiiry I" 1 ^mim^ DUP 0821090 DU 011515 5 Line up the eyepiece graticule with the graduated divisions on the micrometer so that the number of whole micrometer divisions can be counted from one side of the eyepiece graticule graduations to the other 6. If less than a whole division remains, estimate this fractionJo the nearest micrometer and add to the number of whole divisions of the stage micromete. after converting to micrometers This totalled result the protected or obtect dimension of the eyepiece graticule Example' 1. A stage micrometer with 10 micrometer divisions was placed on the stage of a microscope, 2. Tlie tofiowmg diagram depicts the view of the superimposed eyepiece graticule and stage micrometer Note that 10 whole divisions span across the graticule; i.e, 10 x 10 micrometers. 3. The remainder of the 11th division is estimated as being one third of a whole division, i.e. three micrometers Adding these together yields 103 micrometers which is the object dimension of the eyepiece graticule. Note that if the interpupillary distance, objective, intermediate magnification, or even in some microscopes the eyepiece is changed then this usualfy changes the object dimension of the eyepiece graticule -- thus necessitating recalibraton. Appendix F Test Slides for the Determination of the Detection Limit during Phase Contrast Microscopy Source of Supply (until commercial marketing has started): Asbestos Institute for Occupational and Environmental Safety and Health GOrlitzer Str. 1 4040 Neuss Germany Mounting of Test Slides A membranefilter, positionedon a microscopic slide, was treated with acetone vapour in order to produce a transparent film. Spherical Latex Particles, with a refractive index ofl .56 (similar to that of chrysolite) were diluted with alcohol. Agglomeration of the particles was minimised by ultrasonic agitation. After evaporation of the liquid, a drop of triacetine was added to the film containing the latex Particles and a coversJip was added to produce a normal microscope specimen slide. This process was carried out in the same manner as would be applied to a dust slide membrane filter; consequently the slide has the same optical characteristics under phase contrast microscopy as a normal Oirysotile slide. Only panicles of one size were deposited on slides I ana 2 Due to difficulty of delecting the smaller particles conta'ned on slides 3 to 8. particles ol 0 6 pm were also added to tnese slides, representing approximately 10 per cent of the particulates The larger particles are intended to assist in locating the correct specimen plane. The slides available are as follows CodeTNb 1 2- _ 3 4 5 6 7 8 Particle sizes 0,6 um 0 48 um 0 36 pm + 10 per cent 0 6 pm 0 31 pm + 10 per cent 0 6 pm 0 26 pm + 10 per cent 0 6 pm 0 22 pm + 10 per cent 0 6 pm 0 18 pm + 10 per cent 0 6 pm 0 11 pm + 10 per cent 0 6 pm The area most suitable for use has been delineated by a mask outline This area only Application Test observation should commence by observing slide No. 1 (0.6 pm diameter). The slide is positioned on the microscope in the the normal way and positioned (or observation ot the marked area. When the sample is correctly placed a dense distribution of Latex Particles (points of light) will be observed similar to the following picture: Only the particles which are densely distributed and of the appropriate size are the test particles. It is not mtenoad thal the particles should be counted but a dense distribution should be detected. The same procedure is applied to each of the sJides in numerical order. To assist in locating the correct specimen planes in slides 3 to 8. the microscope is first focussed on to the 0.6 pm diarrioter parfictea A danse distribution of the test particles should be observed once the correct focus has been achieved. The process is repeated with each slide until the slide where the test particles are no longer visible. The working detection limit is defined by the slide value on which the particles are just detectable. NOTE: The particle loading of the slide is high If only a small number ol particles is detected in a field of view, the particles being observed are not the test particles. Appendix Q Microscope Adjustment Procedure Good quality phase contrast microscope equipment should be used as detailed in Section 5.2.1 The equipment should be maintained in first-class condition and most manufacturers operate a routine maintenance service which includes the stnppmg down and cleaning of all optical components and the replacement of worn traverse mechanisms. Such services should be used unless skiliod maintenance s ' -.ices can be provided by counting-laboratory stall, in general the foltowinc setting-up procedure should be adopted to ibtain Koehler illumination and good phase contrast conditions but the detail may vary according to manufacturer's instructions and the type of equipment. 1 Race membrane filter specimen slide on microscope stage, 2 Open both the illuminator diaphragm (often referred to as the field ins) and the substage condenser diaphragm. (Note -- at this stage the phase annuli should not be inserted. These are usually based in a rotating drum fitted into the substage condenser unit.) 3. Raise condenser to its upper limit, usually within 1 mm of lower face of specimen slide. 4. Using a convenient level of illumination and lOx objective focus ths specimen. 5. Close down the illuminator diafkiragm and focus this in the field ol view by lowering and raising the condenser Centre the diaphragm and re-open to fill the field of view. 6. Observe the back focal plane of the objective, using either a Bertrand tens fitted to the body of the microscooe or by removing ,.ie eyepiece and using an auxiliary telescope. 7 Observe image of bulb (removing the diffusing disc if one is fitted) and centre the bulb filament -- focussing the bulb it possible with the adjustment provided. The image ot the bulb filament should lid the back focal plane of the objective. Re-insert the diffusing disc it appropriate. (Note -- if the bulb cannot be focussed adjust to give uniform bright illumination.) 8. Insert the correct phase annulus into the condenser system and centre this using the appropriate adjusting screws so that the phase plate in the objective and the image of the annulus coincide exactly. Adjust slightly the condenser focussing if this is necessary. Ensure that the bright annulus image does not extend beyond the phase nng. 9. Revert to normal viewing and change to 40 x objective with no phase annuli in the condenser system. Close down the field diaphragm and refocus this by appropriate adjustment ol the condenser. Re-centre H necessary and re-open to IHI field of view. 10. Repeat stages 6 and 8 after inserting the phase annulus appropriate to the 40 x objective. 11. Revert to normal viewing. DUP 0821091 DU 011516 Appendix H Drawings of Various Asbestos Fibres NOTE: AS drawings are the same scale i.e. one micrometer 1 mm. The number m the right bottom comer of each drawing indicates the number of fixes (as defined) counted. (a) Single fibres These are the simplest of the fibres to identify and count. They are the most common of measurable fibres as seen on the membrane filter. Amosite and croctddtte fibres generally assume a straight needlelike form. Chrysotile fibres, while sometimes straight, often assume a curved or curty outline. Fixes which appear irregular and perhaps"unfibre-like" are counted rf they conform to the basic requirement of libre definition. AB EF '1 `5 V 11 ii 1 1 GH i `1. K L ni1 i1i 0p < J, 1 0R I 1 \>Y 1i 1 1 s 'V V wX a1 I O V (b) Split fibres These appear generally as a fibre or floras splitting away from a single stem. Provided that the fixe conforms to the definition at its longest length and greatest thickness, any particu'ar fibre configuration should be counted as one tibre only. (c) Grouped fibres These are formed when fibres overlap, intertwine or pack together. The simplest form is when two fibres overlap and cross each other. In this case each fibre in the group appears as a discrete entity. In more complex form fibres lie nearly parade! and appear to originate from the same bundle. The latter should be counted as one fibre only, provided the bundle has a total width not greater than three micrometers and conforms to the other criteria. Occasionally groups of fibres are seen`as an indeterminate number of fibre entanglements which appear to originate from the same fibrous bundle. These should not be counted as fibres. Seal*: 0 0 0 10 5pm x 1 A r `/ r, Y.r, Y Y f 1i i i K 'J ii "I '{"l Tt /k Q ii R y *, (t i <, \, 0 O Scott: i__ l 5pm A 81 c 0 * 1 2 4 342 0H / i 'I KL 1 00 00 0 Seolt i__ i 5 pm DUP 0821092 DU 011517 (d) Fibres with otter Particles This Stroup consists of fibres attached to, or embedded in particulate matter. This latter material could be parent asbestos rock, or resins, cement, silicates, etc. as used in manufactured products. Under the microscope some fibre, especially chrysotile. appears to project from the participate matter with only part of the fibre seen. Other fibres (often amosite) are seen as embedded in the particulate matter. If the particulate matter is not more than thioe micrometers wide, all ftores which conform to the definition should be counted. NOTE Once a particle appears with a fibre, the particle is considered to be attached to it General Note: Even after meticulous application of the above criteria and guides, there wit stilt be times when it is difficult to make a decision. At these times it is important to ensure that the best conditions of microscopy have been achieved because the fine details of the image are often the determining factors. Appendix I 1 "1 VA B c kl E V- 11 11i1 K y6 1 J 4i - L i i l 22 2 i sM N 0 p QR it4 1 1 00 00 VS u V W X r0 \L 0 0 00 0 Sco/e: 5pm Counted by Date Microscope No.: Graticule Type : 0-bundles X-background not okay Dust C unting Record (Example only) -=--------- ---- Area: mmJ number of fibres ) fields c - Enf . ! . F Ehcf V _ fibres ml In special circumstances it is of value to record the number ol fibres contained in individual fields of counting. Example: Of Sample No.: DUP 0821093 rncf A a V number of fief* counted effective filter area (mm1) area of the counting field (mm) total flow (ml) - (constant factor) Du 011518 BIBLIOGRAPHY 1. Edwards, G. H. and J. R. Lynch The Method used by the U.S. Public Health Service for Enumeration of Asbestos Dust on Membrane Fitters. Ann. Occ. Hyg.. Vol. 11. t-6 (1968) 2. Asbestosis Research Council (a) Technical Note 1 ("971) The Measurement of Airborne Asbestos Dust by the Membrane Filter Method (Rev.). (b) Technical Note 2 (1971) Dust Sampling Procedures for use with the Asbestos Regulations 1969. Rochdale, Lancs. 3. U.S. Dept, of Health, Education and Welfare, Public Health Service. National Institute of Occupational Safety and Health. Criteria for a Recommended Standard -- Occupational Exposure to Asbestos. HSM-72-10267 (1972) 4. Leidei, NA. S. G. Bayer and R. D. 7umwaldo USPHS/NIOSH Membrane Fitter Method for Evaluating Airborne Asbestos Fibres. NIOSH Unpublished In-House Report TR-84 (1973) 5. Beckett, S. T. and M. D. Attfieid Inter-Laboratory Comparison of the Counting of Asbestos Fibres sampled on Membrane Filters. Ann. Occ. Hyg., Vol. 17,85-96 (1974) 6. AIHA-ACGIH Aerosol Hazards Evaluation Committee Recommended Procedures forSampling and Counting Asbestos Fibres. Am. Ind. Hyg. Asa. J,, Vol. 36.83-90 (1975) 7. AIHA-ACGIH Aerosol Hazards Evaluation Committee Background Documentation on Evaluation of Occupational Exposure to Airborne Asbestos. Am. Ind. Hyg. Ass. J,, Vol. 36,91-103 (1975) 8. Gabriel, J. M. and D. Bouige Prelevement et Numeration des Fibres D'Amiante Cahiers de Notes Documentakes, No. 79,2e Trimestre, 207-211 (1975) 9. Australian Department of Health Membrane Filter Method for Estimating Airborne Asbestos Dust Canberra (1976) 10. Beckett, S. T., R. K. Hey, R. Hirst, R. D. Hunt. J. L. Jarvis and A. L. Rickards A Comparison of Airborne Asbestos Fibre Counting With and Without Eyepiece Graticule. Ann. Occ. Hyg., Vol. 19, 69-76 (1976) 11. Walton. W. H,, M. D. Attfield and S. T. Beckett An International Comparison of Counts of Airborne Asbestos Fibres Sampled on Membrane Filters. Ann. Occ. Hyg., Vol. 19, 215-224 (1976) 12. Gibbs, G. W., P. Baron, S. T. Beckett, R. Dillan, R. S. J. du Toit, M. Koponen and K. Robock A Summary of Asbestos Fibre Counting Experience in Seven Countries. Ann. Occ. Hyg., Vol. 20. 321-332 (1977) 13. Leidei, N. A., K. A. Busch and J. R. Lynch Occupational Exposure Sampling Strategy Manual. NIOSH Technical Information Report, 77-173 (Jan. 1977) 14. Robock, K. and U. Teichert Techniques. Strategies and Results of Dust Measurements in the Asbestos Industries. Vth International Conference on Pneumoconiosis/ILO, Caracas, Venezuela (1978) 15. Advisory Committee on Asbestos Asbestos measurements and monitoring of asbestos in air (2nd Report). Health and Safety Commission (UK), 3-28 (1978) 16. Rickards, A. L. The Routine Monitoring of Airborne Asbestos in an Occupational Environment. Ann. Occ. Hyg., Vof. 21,315-322(1978) 17. Cooper, D. W., H. A Feldman and G. R. Chase Fibre Counting: A Source of Error Corrected. Am. Ind. Hyg. Ass. J., Vol. 39,362-367 (1978) 18. Leidei, N. A, S. G. Bayer. R. D. ZumwakJe and K. A Busch USPHS/NIOSH Membrane Filter Method for Evaluating Airborne Asbestos Fibres. NIOSH Technical Report, 1-89 (Feb. 1979) ACKNOWLEDGEMENTS The Dust Measurement Advisory Panel (DMAP) has been greatly assisted in its work by contributions from the following Institutions and their representatives who took part in the International Colloquia on Dust Measuring Technique and Strategy organised by the Asbestos International Association (Warmensteinach, August 1977; Washington, October 1978). * member of DMAP AUSTRALIA Mr. G. Major School of Public Health and Tropical Medicine The University of Sydney Building A 27 New South Wales 2006 Mr. G. Pickford* James Hardie & Co. P/L Ltd. R & E Centre Grand Avenue Camellia New South Wales 2142 Mr. J. W. Winters James Hardie & Coy. Pty. Ltd. 65 York Street Sydney AUSTRIA Mr. Bigga Osterreichische Staub (Silikose) -- Bekdmpfungsstelle Technische Abteilung Postfach 72 a-8700 Leoben Mr. Schmiedinger Etemlt-Werke Ludwig Hatschek A-4840 Vdcklabruck BELGIUM Mr. Roger Meunier REDCO Kuiermansstraat B-2920 Kapelle op den Bos Mr. Vanherie EEC Advisory Council of the A1A WTC 1 - P.O. Box 37 Boulevard E. Jacqmain 162 B-1000 Bruxelles CANAOA Mr. G. Gibbs, M.Sc., Ph.D. Occupational Health and Safety Unit Institute for Mineral Industry Research, Gault Estate McGill University Mount SL Hilaire Montreal, Qua. J3G 4S6 Mr. Marc Trudeau* Technical Advisor Quebec Asbestos Mining Association Thetford Mines P.O. Box 624 Quebec G6G 1J4 Mr. Jean Marc Lalancetts Bureau de Lauinaie 845 ouest, Boul. SL Cyville, Quebec DUP 0821094 DU 011519 DENMARK Mr. Thomas Schneider ArbejdstiJsynet Statens Institut for Arbejdshygiejne Institute for Working Environment Baunegaardsvej 73 Du DK-2900 Hellerup Mr. K. Thiele Dansk Etemit Fabrik A/S DK-9100 Aalborg P.O. Box 763 FINLAND Mr. N. Arppe Paraisten Kalkki Oy SF-08580 Muijala Mr. M. Koponen Outokumpu Oy Paakonttori Tootonkatu 4 SF-00100 Helsinki 10 Mr. A. Pafomdki Paraisten Kalkki Oy SF-08680 Muijala FRANCE Mr. Daniel Bouige* LHCF Laboratoire d'Hygiene et de Contrite des Fibres Minerales 10 Rue de la Pipintere F-75008 Paris Mr. Bernard Carton 1NRS Institut National De Recherche et de Security Avenue de Bourgogne F-54500 Vandoeuvre Mr. Clousier FerodoSA B.P. 20 F-14.110 Conde/NOI Reau Mr. Patrick Sebastien Laboratoire delude des Particules Inhatees 37 Bd. Saint-Marcel F-75013 Paris Mr. Turpin Etemit Industries 8 Rue de la Fontaine F-59121 Prouvy GERMANY Dr. G. Riediger Staubforschungsinstitut des Hauptverbandes der gewerblichen Berufsgenossenschaften Postfach 50 40 5300 Bonn 5 Dr. Klaus Robock* (Chairman DMAP) Asbest-lnstitut fur Arbeits- und Umweltschutz e.V Gdriitzer Str. 1 4040 Neuss 1 Mr. Ullrich Tefehert* (Secretary DMAP) Asbest-lnstitut for Arbeits- und Umweltschutz e.V GdriitzerStr. 1 4040 Neuss 1 Mr. D. Wettte Institut for Arbeits- und Sozialmedizin Schillerstr. 29 8520 Eriagen IRELAND Mr. E. J. Fenelon Tegral Building Prods. Ltd. Athy, Co. Kildare ITALY Prof. A. D. Bonsignore Universita' di Genova lstituto Medicina del Lavoro 10 Viale Benedetto XV 1-16132 Genova Prof. G. Cecchetti Universita' Cattolica del Sacro Cuore lstituto Medicina del Lavoro Centro di lgiene Industrials Via della Pineta Sacchetti 644 1-00136 Roma Dr. A. Marconi lstituto Superiors di Sanita' Laboratorio di lgiene del Lavoro Viale Regina Elena 299 1-00136 Roma NETHERLANDS Mr. H. J. van't Haaff Etemit B.V. Goor, Haven 12 Postrekening 10237 Mr. R. W. Lanting Instituut voor Miliquhygiene en Gezondheidstechniek T.N.O. Schoemakerstraat 97 Delft Mr. Meppelder Directorate General Labour P.O. Box Voorburg Mr. P. B. Meyer TNO-lnstitute for Envior Hygiene P.O. Box 214 Delft NORWAY Mr. L. Knutsen A/S Norcem 3470 Slemmestad Mr. J. Jahr Yrkeshygienisk Institutt P.O. Box 8149 Dep. Oslo 1 REPUBLIC OF SOUTH AFRICA Dr. R. S. J. Du Toit P.O. Box 1132 Johannesburg 2000 SWEDEN Mr. Folke Danstrand C.A. Class AB RuskvSdersgatan 8 417 Goteborg Mr. N. Hallin Organisation for Industrial Safety and Health in the Construction Industry BurgghSIsam Fack 10041 Stockholm Dr. Staffan Krantz Nat. Board Occ. Safety and Health Fack 100-26 Stockholm Dr. S. Skyllberg Swedish National Board of Industrial Safety Fack 10026 Stockholm 39 UNITED KINGDOM Dr. Steve Beckett Institute of Occupational Medicine 8 Roxburgh Place Edinburgh Mr. A. A. Cross Asbestos International Association 68 Gloucester Race London W1H3HL Mr. John L Jarvis Cape Industries Ltd. Environmental Services Lab. Iver Lane. Cowley Uxbridge. Middx. Dr. G. Leguen Research & Service Laboratory Division Health & Safety Executive 403/405 Edgware Road Cricklewood London N.W.2 Dr. Trevor L Ogden Health & Safety Executive 403 Edgware Road London N.W.2 Mr. A, L Rickards* Turner & NewaJI Ud. P.O. Box 22 Trafford Park 77 Fountain Street Manchester M2 2EA Mr. Reginald Sykes* Asbestos Research Council P.O. Box 40 Rochdale OL12 7EQ Dr. Chris Taylor Dept. Medical Biophysics Stopford Building University of Manchester Oxford Ftoad Manchester Ml 9PT Mr. R. M. Wagg Health & Safety Executive 403/405 Edgware Road Cricklewood London N.W.2 Dr. W. H. Walton Institute of Occupational Medicine Roxburgh Place Edinburgh EH89SU DU 011520 DUP 0821095 U.SJL Dr. Paul A. Baron N.I.O.S.H. Robert Taft Laboratory 4676 Columbia POWY Cincinnati, Ohio 45226 Dr. G. Chase* Johns-Manville Corporation Health, Safety and Environment Greenwood Plaza Ken-Caryf-Ranch Denver, Colorado 80217 Mr. Ching Bien Mr. Stephen Mallinger Department of Labor OSHA 200 Constitution Avenue, NW i Washington, D.C. 20210 Dr. Samuel H. Goldberg Dust Branch MSHA 4800 Forbes Avenue Pittsburg Pa 15213 Dr. Y. Hammad Tulane University School of Medicine Pulmonary Disease Section New Orleans, La. 70112 Mr. James G. Heil Certain Teed Corporation Technical Center P.O. Box 1100 1400 Union Meeting Road Blue Belt, Pa. 19422 Mr. Jimmie Hodgeson NationsI Bureau of Standards Chemistry Building Room A 345 Washington, D.C. 20234 Mr. F. A. Madsen OSHA Occupational Safety and Health Administration 390 Wakara Way Salt Lake City, Utah 84108 Dr. Harrison B. Rhodes* Union Carbide Corporation P.O. Box 579 Niagara Falls, N.Y. 14302 Mr. Glen Sutton Mine Safety and Health Administration Denver Technical Support Center P.O. Box 25 367 Denver, Colorado 80225 The DMAP acknowledges its special indebtedness to work already done in this field by: Asbestosis Research Council P.O. Box 40 Rochdale OL12 7EQ U.K. N.I.O.SK Robert Taft Laboratory 4676 Columbia PDWY Cincinnati, Ohio 45226 U.SA National Health and Medical Research Council P.O. Box 100 Woden Canberra, A.C.T. 2606 Australia & msm DU 011521 ' DUP 0821096 aMiiaiife-ir.Mitiiiiii.gy Asbestos International Association Member Associations AUSTRALIA" South Pachc 4sDestos Assoca" on C'O L W Farrar & Assoc Pty Ltd 129 vork Street Sydney 2000. NSW Telephone 297946 AUSTRIA Vere.n Der Oesterreichischen Asbestzementfabrikanten Pnnz Eugen Strasse 8. 1041 Wien Telephone 65 58 77 SENELUX (Belgium-Netherlands-Luxembourg) Cornite d Information de ! Amianie Bene*ux W T C Bote 37 So'.i'evard E Jacqmairi 162 B tOOC 3-uxe:ies Telephone 102)218-6329 Telex 2' 696 CANADA .nsHu'e ct Occupational & E". "zr."'erta. Health (Association) AMAQ 5-.4e 320 560 est Grande Ailed One bee. Que GIR2K2 Te'epnc-ne (418.529-8163 DENMARK Damsh Asbestos Information Group c. o Dansk Eternit Fabrik A/S FO 8o 763. DK-9100 Aalborg FINLAND Finnish Asbestos Information Group c/o Paraisten Kalkki Oy. SF-21600 Parainen Telex 62220 Pkparsf FRANCE Chambre Syndicate de I'Amiante 10 Rue de la Pepimere. 75008 Paris. Telephone: 522 12-34 GERMANY Wirtschaftsverband Asbestzement e.V. Goertitzer Strasse i D 4040 Neuss Telephone. (0) 2101 13051 Telex: 851 7402 AUD Wirtschaftsverband Asbest e.V Oberscnelcler Weg 2-4 6000 Frankfurl/Main 50 Telephone (0611)58 20 77 IRELAND Irish Asbestos Counc-i 5JSouth Leinster Sheet Dubim 2 Telephone O'-63974 Telex 428! ITALY Aslsociazone Nazionaie Industrial! Amianlieri Unjone induslnaie Via Fanli 17 "0J28 Tor.no Telnnnone ~7i n?3 Teiex 23064". UNiNDUTO Assocemento via di S Teresa 23 0CH98 Roma Telephone 864 3147865 068 JAPAN AIA Committee Japan Asbestos Association 8 !0-7Gmza C'uo-nu Tokyo NORWAY Norv.egian Asbestos information G'oup Norcem AB =3470 Slemmestad REPUBLIC OF SOUTH AFRICA South African Asbestos Producers Adv.sory Committee P O Box 10505 Johannesburg 2000 Telephone 395458 Telex 87582 SPAIN Asociacion Espanola de Fabricates de Productos de Amianto Me Diaz de Haro 38 Aoartado 558 Bilbao (10) Teieohone 437 37 05 -Telex. 32125 Monsa E Asociacion de Fabricantes de Productos de Amianto-Cemento Ratael Calvo 18. Madrid (10) SWEDEN Swedish Asbestos Information Group C.A Clase A.B. Ruskvadersgatan 8. 41734 Gothenburg SWITZERLAND Arpeask-e s Asbest c c Si.Her a Naler Dufon- Strasse '01 S02 ' Zwrich . UNITED KINGDOM Asoesfos Information Centre SacKviile House 40 Piccadilly London W1 V 9PA Telephone 01-439 9231/2/3 Telex 21120 ret 2526 US.A. Asbestos Information Association/NA 1745 Jefferson Davis Highway C-ystai Square. Suite 509 Arung-.en Virginia 22202 Telephone (703)979 1150 Telex Addit'O^dl Members since 31 May 78 GREECE Hel'enic Asbestos & Asbestos Cement Association 8 Cmirou Street Athens 1133) Telephone 32 31 244 Telex 215871 now includes Indonesia. Malaysia. New Zealand and Singapore Asbestos International Association 68 Gloucester Placa, London W1H 3HL, England. Telephone: 01-486 3528 Telex: 298618 INTA G Amended 7 September 1979 DU 011522 DUP 0821097