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ASBESTOS FIBRE MEASUREMENTS IN THE WORKPLACE E. Gonzalez-Fernandhz,* Paulino D. de la Osa* and Felix R. MartM `Institute Nacional de Seguridad e Higiene en el Tcabajo, Centro National de Nuevas Tecnologias, Torrelaguna, 73, 28027 Madrid, Spain and tFaculty of Biology, Statistic Department, C.U.I. Arcos de Jalon University of Madrid, Spain Abstract--Industrial hygiene evaluation of airborne asbestos dust by the membrane-filter/phasecontrast optical-microscope method has been adopted by most countries, but detailed procedures differ. In the present work sampling results obtained in an asbestos cement factory by the NIOSH Analytical Method P & CAM 239 and the AIA Recommended Technical Method No. 1 (adopted as the European standard) have been compared. The concentrations measured by the AIA method were on average less than those determined by the NIOSH method, the mean ratio AIA/NIOSH being 0.29. Analysis of variance showed the difference to be statistically significant. Investigations into the source of the difference showed that it arose from the different methods of mounting and evaluating the samples rather than from the methods ofsample collection. The fitting ofa cowl to the sampling head in the AIA method had no effect. These findings regarding the source of variation are consistent with previous results by the same team using laboratory-prepared samples. However, it appears that the relationship between the methods may not be the same for all workplaces where asbestos is found. The findings ofthis study have implications not only for comparing fibre concentrations measured by the AIA and NIOSH methods but also for harmonizing environmental standards. INTRODUCTION Airborne asbestos fibre concentrations of all types (principally chrysotile) in working environments are generally sampled on membrane-filters and counted by phasecontrast optical-microscopy. This, despite its many limitations, is accepted by most countries as a routine method. Experience has shown that the method does not always produce comparable results when used by different laboratories and by different counters (Beckett and Attfield, 1974; Gibbs et al,, 1977). It is well known that differences can arise owing to variations in sampling, slide preparation and optical counting (Beckett, 1980; Busch et a/., 1979; Pickford, 1980). Much of the investigation of the inter- and intra-laboratory reliability (Walton, 1982) of the method has focused on the analytical equipment and methodology. However, to characterize the inherent variability of the entire sampling/analytical procedure, factors such as inter-counter variability and sampling error must be added to the intrafilter variation. Most countries today are attempting to develop a well standardized method for counting asbestos fibres at workplaces and new regulations for occupational exposures to asbestos are now under consideration by the Commission of the European Communities (CEC) and Occupational Safety and Health Administration (OSHA) as well as International Organization for Standardization (ISO) and American Society for Testing and Materials (ASTM). Previous studies have investigated the effects of counting rules and aspect ratio on the levels and reproducibility of fibre counts (Cowie and Crawford, 1982; Crawford et al., 1982). A comparison (Gonzalez-Fernandez and Martin, 1986) between the counting HWBUI0001 364 E Gonzalez-Fernandez al. criteria established in the Analytical Method P & CAM 239, published by the National Institute for Occupational Safety and Health (NIOSH, 1977) and the counting rules from the Recommended Technical Method No. 1, published by Asbestos International Association {AIA, 1979), has been made on a set of artificially prepared samples o' chrysotile, croddolite and amosite, using different mounting media and eyepiece graticules. On average the AIA method gave rather higher counts than the NIOSH method for chrysotile (ratio 1.2) but lower counts for croddolite (ratio 0.5); the data for amosite were more scattered and the difference was not statistically significant. The differences between mountants and graticules were shown to be contributory factors. However, the possible effects of differences in sampling between the AIA and NIOSH methods were not studied and it was recognized that the findings might not necessarily apply to industrial samples. The aim of this paper is to compare the entire sampling/analytical NIOSH P & CAM 239 method with the more recently recommended RTM 1 method by AIA, which has been considered as the European Reference Method. Matched pairs of samples were taken at several workplaces in a chrysotile and croddolite asbestos-cement factory by using both NIOSH and AIA sampling procedures. Furthermore, a second comparison was made- between AIA and NIOSH counting rules with a batch of samples chosen randomly from those taken according to the NIOSH sampling guidelines. In this case, each filter wedge was mounted and counted according to the NIOSH and AIA methods. The airborne asbestos fibre concentrations found by each method were used for a health hazard evaluation against the OSHA standard of 2.00 fibre ml- ` (f ml"l) at 95% confidence level. A possible source of variability is the use ofa cowl, as required by the AIA sampling procedure (Peck ec al., 1985). Few investigations have been undertaken into the differences between the collection characteristics ofcowled and uncowled filter holders. There is also some disparity between the results obtained for asbestos air samples taken with and without a cowl. A brief experiment (Speight and Marsh, 1984) showed a difference by a factor of about four between results obtained with cowled and uncowled filters when sampling airborne amosite insulation fibres. However, an experimental procedure (Knight et al., 1985) in which cowled and uncowled sampling heads were used side by side for personal asbestos chrysotile sampling showed no significant difference between fibre densities measured by cowled and non-cowled filter holders. To elucidate the influence of the cowl in the AIA sampling of asbestos fibres, matched pairs of samples were taken with and without cowl. Two different types of cowls were tested, one metallic and the other of non-conducting polypropylene. MATERIALS AND METHODS Apparatus A Carl Zeiss III phase contrast photomicroscope was used to count all the samples at 500 x magnification with 4 mm objective. The graticules used were: Porton reticle (Edmund Scientific Co. Barrington, New Jersey, Stock No. 30084) with a field area of 0.0016 mm2, and a Walton-Beckett graticule No. G 22 (Graticules Ltd, Tonbridge, Kent, U.K.) with a field area of 0.0085 mm2. A drawing of these graticules is shown in Fig. 1. A Carl Zeiss stage micrometer 5+ 100/100 mm was used to calibrate the eyepiece graticules at the magnification used. The HSE/NPL phase contrast standard test slide Mark II (designed and developed by the U.K. Health and Safety Executive and the National Physical Laboratory, U.K.) was used for the determination of the detection limit. This slide has seven blocks of fine ridged lines producing successively smaller phase changes. Block No. 6 was detectable along the entire length of the lines with our microscope. Detection of block No. 5 is considered to be an acceptable performance, which should allow chrysotile fibres 0.15 nm dia. to be seen (Le Glten et al., 1984). > HWBUI0001156 ASBESTOS INTERNATIONAL ASSOCIATION The asbestos industries' world wide organisation for environmental and occupational health protection 68 GLOUCESTER PLACE, LONDON W1H3HL TEL: 01-486 3528/9 TELEX: 298618INTA G Dust Advisory Panel (DAP) Herewith copy of "Comparison of AIA and NIOSH Methods cm Asbestos Fibre Measurements in the Workplace", E. Gonzalez-Femandez et al. - Ann.Qccup.Hyg., Vol 31 No. 3, pp 363-373, 1987. AIA/20/2/7/EAS 19 November 1987 With Compliments HWBUI0001157 366 E. Gonzalez-Feknandez ec at. Filter holders These were three-piece styrene plastic cassettes of 37 mm dia. (Millipore, Ref. M000Q37AQ) and 25 mm dia. (Millipore, Ref. MQ00025AO). The 25 mm cassette was fitted with a protective metallic cowl (Fig. 2) not commercially available or with a polypropylene 50-mm non-conducting extension cowl (Millipore, Ref. M0GQ025R0). Chemicals Dimethyl phthalate, diethyl oxalate, triacetin and acetone, analytical reagent grades from Merck, were used. Membrane AAWP04700 filters (Millipore Iberica, S.A. Spain) were added to the ester mixtures. Sampling and analytical procedures A brief description of both AIA and NIOSH methods is reported here. The details ofthe AIA method have been reported by the Asbestos International Association (AIA, 1979) and the NIOSH method by U.S. Department ofHealth, Education and Welfare (NIOSH, 1977). The main differences between the two methods can be summarized as follows: NIOSH Method Filter type (diameter, pore size) Foil-wrapped cassette Flow rate (1. min'1) Filter mountant Reticle type Field area at the specimen plane (mm1) Phase-shift detection limit {pm) 37 mm, 0.8 pm No 1--2.5 esters mixture Porton or Patterson 0.003-0.006 Not specified AIA Method 25 mm, 1.2 pm Yes 1.0 acetone-triacetin Walton-Beckett 0.Q07S5 0.44 Experimental samples were obtained for different durations of time according to the sampling flow rates mentioned using calibrated Model Fix-Flow MSA portable pumps (Mine Safety Appliances Co. Pittsburgh). The entire filter was used to determine fibre concentrations for samples taken by the AIA method. The filter was cleared by acetone vapour plus one drop of triacetin. A wedge-section of the filter was used to count fibres for samples taken by the NIOSH method. In this case, a mixture of dimethyl phthalate and diethyl oxalate (1:1) with 0.05 g membrane filter type AA added per ml of solution was used as an embedding medium. According to the AIA criteria for counting asbestos fibres a fibre is any particle having the following geometric dimensions--length greater than 5 pm, diameter less than 3 pm and length to diameter ratio (aspect) greater than 3:1; specific situations are considered in the case of complex configurations of fibres or aggregates (single fibres, split fibres, grouped fibres, and fibres with other particles); a Walton-Beckett eyepiece graticule is recommended. By the NIOSH counting criteria, any particle which has a physical dimension longer than 5 pm and wi th an aspect ratio of 3:1 or greater is deemed to be an asbestos fibre. There is no specification for the maximum diameter of the fibre, and bundles of fibres are counted as one fibre unless both ends of the fibre can be clearly resolved. For fibre counting, a recommendation is made to use a Porton reticle, although others such as the Patterson Globe and Circle can be substituted. Comparison of AIA and NIOSH methods on asbestos 367 Sampling survey and experimental design A field study was conducted over 4 months, viz. in January, March and April 1982 and in January 1983 in an asbestos-cement factory in four different workplaces. In total 176 samples were taken, 88 on 37 mm dia. membrane filters and 88 on 25 mm dia. membrane filters, using sampling flow rates of 1.5 and 1.01. min 71 for NIOSH and AIA methods, respectively. The cassettes were randomly placed membrane-face down on the Left and right lapels of the workers, one on each lapel. A measured quantity of air between 100 and 3001. was drawn through each membrane filter, depending on local work and environmental conditions, so that the fibre densities on the filter would lie between the recommended limits of NIOSH and AIA methods. Each pair of samples was run for the same length of time. A second comparison was made between the NIOSH and AIA mounting and counting procedures in 54 samples chosen from those taken with the NIOSH procedure. From the samples that had previously been mounted and counted with the NIOSH package counting rules, another wedge-shaped piece, about 30, of each membrane filter was cleared by acetone vapour plus triacetin and counted with the AIA counting rules. The combination procedures of these two methods is abbreviated to NIOSH-AIA method. Counts were made by two different counters over two different wedges of each sample mounted according to the NIOSH and AIA analytical methods. Emphatic instructions were given not to interchange counting rules between methods. The experiment to examine the influence of using cowled and uncowled 25 mm sampling heads was made as follows. Personal air samples were taken concurrently in the same workplaces as mentioned before. The samples were collected for the same periods and flow rates to give fibre densities of around 50-300 fibres mm " 2. The filters were cleared, mounted and counted according to the AIA RTM 1 method and some counts were repeated to reduce errors. RESULTS AND DISCUSSION Table A1 in the Appendix shows the raw count data obtained in the survey of an asbestos-cement factory over the 4 months. Table 1 shows the fibre densities on the filters and fibre concentrations for the samples evaluated with the full AIA and NIOSH sampling/analytical methods, sub divided by workplace. An overall AIA/NIOSH mean ratio of0.29 0.04 was obtained; thus, fibre concentrations found by the AIA RTM 1 method were71% (range 67-75%) less than the concentrations found by the NIOSH P '& CAM 239 method. The fibre densities on the filters were well within the recommended limits of 0.5-5.0 fibres per Porton reticle (NIOSH method) or 0.4--10.0 fibres per Walton-Beckett graticule (AIA method). It is known that when the fibre densities on the filter are lower than 10 f mm-2, counts are highly prone to error (Teighert, 1980). Pooled coefficients of variation of 14.4% for all AIA countings and 17.8% for all NIOSH countings were obtained with no significant differences found at a <0.05. Table 2 shows the results obtained when the AIA and NIOSH mounting and counting procedures were applied to 54 samples, ail taken according to the NIOSH sampling scheme. The overall AIA/NIOSH mean ratio was 0.350.05; thus the AIA method counts 65% (range 60-70%) fewer fibres than the NIOSH method. i . i 363 E. Gonzalez-Fernandez et at. Table l. Comparison of fibre measurements bv complete NIOSH and AIA methods. Geometric MEAN VALUES FOR DIFFERENT WORKPLACES CALCULATED FROM DETAILED DATA IN TABLE 1A Workplace No. of pairs ol samples Fibre density AIA NIOSH (f ram ~ *) (f mm"2) Fibre concentration AIA NIOSH (fm!-1) (fmr>) Ratio of concentrations AIA/NIOSH Mill, loading and mixing Big pipe turning ScnaU pipe turning Pipe cutting 42 22 10 14 66 169 0.27 1.15 0.23 81 147 0.42 1.41 0.30 85 179 0.31 1.03 0.30 109 236 0.60 1.94 0.31 Overall mean + S.D. 0.29+0.04 Table 2. Comparison of fibre counts using both NIOSH and AIA methods on SAMPLES TAKEN BY THE NIOSH P & CAM 239 PROCEDURE ONLY Workplace No. of samples Concentration AIA NIOSH (fml~`) (fml'1) Ratio AIA/NIOSH Mill, loading and mixing 21 0.43 1.15 0.37 Big pipe turning 14 0.45 1.41 0.32 Small pipe turning 10 0.42 1.03 0.41 Pipe cutting 9 0.58 1.94 0.30 Overall mean S.D. 0.35 + 0.05 Table 3. Analysis of variance for methods (NIOSH, AIA, NIOSH-AIA) and WORKPLACES Source of variation Degrees of freedom Sum of squares Mean square F Between methods Between workplace Interaction Residual 2 153.09 76.54 102.611* 3 31.80 10.60 14.209* 6 1.89 0.32 0.423 N.S. 427 318.52 0.75 Terras marked * are significant at better than the 0.1% level. N.S. = Not significant. Establishing whether the changes in counting are ofstatistical significance is readily done'by analysis of variance (ANOVA). For this the statistical computing package BMDP (Dixon, 1983) was employed. A natural logarithmic transformation was used to normalize the distribution (Box and Cox, 1964) and all statistical analyses were made with transformed data. If any factor or interaction of statistical significance was found, we used the Student-Newman-Keuls test (SNK-test) to determine whether mean values of each level factor showed any significant difference (Sokal and Rohlf, 1969). V- HWBUI0001160 Table 5. Fibre concentrations from personal air sampling using cowled and UNCOWLED FILTER HOLDERS Workplace sampled Metallic cowl (fmr1) Plastic cowl (f ml "1) Without cowl (fml'1) Mill loading and mixing Big pipe turning Small pipe turning Pipe cutting 0.0/0.0 0.4/Q.4 0.4 0.8 0.2/0.2 0.2/0.2 0.1 0.1 0.4 0.4 0.3 0.1 0.1 1.5 1.8 0.1 0.2 0.2 0.0/0.1 0.3 0.3 0.6 0.2 0.1 0.1 0.0 0.4 0.3 0.2 0.1 0.1 1.1 1.3 0.1/0.1 0.1/0.2 0.4 0.1/0.1 0.6/1.0 0.5 0.8 0.1/0.2 0.1/0.2 0.1 0.1 0.3 0.3 0.1 0.1 0.1 1.2 1.5 0.1 0.2 0.2 Table 6. Analysis of variance for AIA sampling methods, tested with and without COWLS, AND WORKPLACES SAMPLED Source of variation Degrees of freedom Sum of squares Mean square F Between sampling methods Between workplaces Interaction Residual 2 0.34 0.17 0.227 N.S. 3 6.92 2.31 3.049 N.S. 6 2.10 0.35 0.462 N.S. 49 37.10 0.76 N.S. = Not significant. HWBUI0001161 370 E. Gonzaljez-Fernandez et al. Table 3 shows the ANOVA results for all counts of all the samples taken (Table A1); geometric mean.values ofthese counts were given in Tables 1 and 2. It can be observed that there is statistically significant difference, at tetter than the 0.1 % level, between the methods used. As expected, difference between workplaces is a significant source of variation, owing to the intrinsic variationin fibre loadings depending on the workplace studied. The differences between the three methods have been evaluated by the SNK-test. This showed that mean fibre concentrations obtained by the entire NIOSH method were significantly higher than those obtained by the entire AIA method and also significantly higher than those obtained when samples taken by the NIOSH method were mounted and counted by AIA procedures (NIOSH-AIA method); moreover, there was no significant difference between the entire AIA and NIOSH-AIA methods. Thus it is apparent that the statistically significant difference between the results obtained by the NIOSH P & CAM and the AIA RTM-1 methods arises from differences in mounting methods and package counting rules rather than from differences in sampling methods. This is consistent with the findings from our previous work in which the effect of mounting and counting procedures on fibre counts was pointed out (Gonzalez-Fernandez and Martin, 1986). However, the results from these studies taken together suggest that the relationship between the AIA and NIOSH methods is not constant but varies with asbestos type and source of sample. Table 4 shows the health hazard evaluation according to the asbestos fibre concentrations obtained by the NIOSH method in each workplace, using a statistical approach on a long-term sampling scheme. The time-weighted average concentrations were calculated and used to determine `compliance', `non-compliance' or `no decision' at 95% confidence in comparison with the OSHA standard of2 f ml-1. There were five situations of risk, three with no risk and in two cases there was no decision. If these same statistical criteria for health hazard evaluation were applied to the asbestos fibre concentrations obtained by the AIA sampling/analytical method, all the workplaces would be judged to be in compliance (`no risk'). This different result is due to the count differences pointed out in Table 1. Table 5 summarizes the results obtained when personal air samples were taken at several workplaces by the AIA RTM 1 method using cowled and uncowled 25 mm filter heads. An ANOVA was.carried out, as shown in Table 6, and an F-test performed. The F-test indicates that neither the difference between sampling methods nor the difference between workplaces is a significant source of variation. CONCLUSIONS In this study we found that there was a significant difference between the entire AIA and NIOSH sampiing/analytical procedures for measuring airborne asbestos fibres. The AIA RTM 1 method gives, on average, 71% less fibre concentration than the NIOSH P & CAM 239 method and therefore very different conclusions can be drawn in a risk evaluation of the workplaces sampled. This discrepancy appears to be due to differences in mounting and counting criteria between the two methods rather than to sampling differences. The attachment of a cowl to the filter holder, as required in the AIA method, had no significant effect on the sampling result. The relationship between the methods may not be the same for all workplaces where asbestos is found. HWBUI0001162 Comparison of AIA and NIOSH methods on asbestos 371 The findings of this study have implications not only for the comparison of fibre concentrations measured by the AIA and NIOSH methods but also for the harmonization of environmental standards. REFERENCES Asbestos International Association (1979) Recommended Technical Method No. I (RTM 1). Health and Safety Publication, AIA, 68 Gloucester Place, London, U.K. Beckett, S. T. and Attfield, M. D. (1974) Ann. accup. Hyg. 17,85-96. Beckett, S. T. (1980) Aim. occup. Hyg. 23, 259-272. Box, G. E. P. and Cox, D. R. (1964) Jl R. statist. Soe. B26, 211-252. Busch, K. A., Hornung, R. W., Smith, R. J. and Lhdel, N. A. (1979) Dusts and Disease, Occupational and Environmental Exposures to Selected Fibrous and Particulate Dusts, pp. 185-197. Parthotex Publishing, New York. Cowie, A. J. and Crawford, N. P. (1982) Technical Report No. TM/82/83. Institute of Occupational Medicine, Edinburgh, Scotland, U.K. Crawford, N. P., Thorpe, H. L. and Alexander, W. (1982) Ttschnical Report No. TM/82/84, Institute of Occupational Medicine, Edinburgh, Scotland, U.K. Dixon, W. J. (Ed.) (1983) BMDP. Statistical Software. Printing with Additions. University of California Press, Berkeley, U.S.A. Gibbs, G. W., Baron, P., Beckett, S. T., Dillen, R., Du Toit, R. S. J., Koponen, M. and Robock, K. (1977) Ann. occup. Hyg. 20, 321-332. Gonzalez-Fernandez, E. and Martin, F. R. (1986) Ann. occup. Hyg. 30, 397-410. Knight, K. L., Bloor, D. M. and Miller, F. (1985) Ann. occup. Hyg. 29, 289-291. Le Guen, J. M. M., Ogden, T. L., Shenton-Taylor, T. and Verrill, J. F. (1984) Ann. occup. Hyg. 28, 237-247. National Institute for Occupational Safety and Health (1977) Manual ofAnalytical Methods (2nd Edn), Vol. 1, pp. 239-1-239-2. U.S. Dept of Health. Education, and Welfare, Public Health Service, Center for Disease Control. Cincinnati, Ohio, U.S.A. Peck, A., Serocki. J. S. and Dicker, L. C. (1985) Am. ind. Hyg. Ass. J. 46, B-14-B-16. Pickford, G. (1980) Proceedings of the Third International Colloquium on Dust Measuring Technique and Strategy, pp. 71-76. Association Francaise de L'Amiante, London, U.K. Sokal. R. R. and Rohlf, F. J. (1969) In: Biometry, pp. 265-273. W. H. Freeman and Co., San Francisco, California, U.S.A. Speight, R. G. and Marsh, A. H. (1984) Ann. occup. Hyg. 28, 353-359. Teickert, U. (1980) Proceedings of the Third International Colloquium on Dust Measuring Technique and Strategy, pp. 29-37. Association Francaise de L'Amiante, London, U.K. Walton, W. H. (1982) Ann. occup. Hyg. 25, 205-208. APPENDIX Table AI. Number of fields observed and number of fibres calculated for the samples taken in THE SURVEY OF WORKPLACES SAMPLED IN AN ASBESTOS-CEMENT FACTORY OVER 4 MONTHS NIOSH method No. of fields f mm"* fml"1 No. of fields AIA method f mm'J f ml"1 NIOSH-AIA method No. of fields f mm"* fml Workplace sampled: mill loading and mixing 25/50 1706/1269 16.2/12.0 100/100 m/m 291/269 2.S/2.6 100/100 100/100 394/400 3.7/3.8 50/50 100/100 166/178 1.6/1.7 100/100 [00/100 119/147 1.4/I.7 100/100 100/100 69/119 0.9/1.5 100/100 100/100 263/300 3.0/3.5 100/100 100/100 175/225 2.0/2.6 100/100 100/100 100/84 0.4/0.4 100/100 100/100 663/406 3.1/2.0 75/75 44/14 82/68 473/244 36/38 9/8 28/26 26/8 17/12 51/40 164/144 0.3/0.1 0.5/0.4 2.8/1.5 0.2/0.3 0.1/0.1 0.3/0.2 0.2/0.1 0.1/0.1 0.2/0.1 0.3/0.3 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- _ -- -- -- -- -- -- -- -- -- (continued) 372 E. Gonzalez-Fernandez et al. Table Al.--(continued) NIOSH method No. of fields f mm"2 fml_1 No. of fields AIA method fmm"! fml~' 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100 69/69 213/297 78/94 631/331 19/38 175/191 63/50 97/106 81/44 200/172 69/47 125/147 244/413 137/131 138/78 125/166 175/109 166/169 200/353 97/153 144/131 81/131 259/197 50/47 I53/I84 219/303 247/413 338/278 319/288 284/244 216/313 219/406 0.4/0.4 1J/I.9 0.5/0.6 4.0/2.1 0.1/0.2 1.1/1.2 0.4/0.3 0.7/0.7 0.4/0.2 1.0/0.8 0.4/0.3 0.8/0.9 1.2/2.0 0.7/0.6 0.7/0.4 0.7/0.8 0.8/0.5 0.8/018 1.1/1.9 0.5/Q.8 0.7/0.6 0.4/0.6 1.2/0.9 0.2/0.2 0.7/0.9 1.1/1.5 1.2/2.0 1.9/1.6 0.9/0.8 0.8/0.7 0.6/0.9 0.6/1.1 100/100 '94/83 100/100 106/106 100/100 89/88 25/40 440/333 100/100 20/22 50/50 321/335 100/100 41/119 100/100 80/108 100 36 100 162 100 29 100 120 100/100 85/87 100/100 50/51 100/100 64/44 100/100 94/83 100/100 138/171 100/100 119/129 100/100 119/111 100/100 35/49 10C/100 21/18 100/100 13/17 100/100 32/25 100/100 36/63 100/100 109/111 100/100 148/184 75/50 272/326 100/100 11/12 50/50 155/402 100/100 145/138 100/100 135/140 100/100 102/74 Workplace sampled: big pipe turning 100/100 306/291 5.9/5.5 100/100 117/81 100/100 194/188 . 4.8Z4.6 100/100 189/118 100/100 138/141 2.S/2.9 100/100 61/68 100/100 163/181 100/100 266/463 3.8/4.I 4.7/8.8 75/100 220/169 -- . __ 10Q/100 75/113 0.5/0.7 100/100 79/87 100/100 219/266 1.6/1.9 100/100 68/81 100/100 141/184 1.2/1.7 75/75 187/191 100/100 125/175. 1.5/2.0 100/100 50/39 100/100 81/100 0.6/0.7 75 159 100/100 56/50 0.4/0.4 100/100 54/144 75/75 1129/825 8.7/6.3 50(50 295/386 100/100 703/631 4.8/4.'4 50/50 337/324 100/100 106/75 0.7/0.5 -- -- 100/100 156/184 1.1/1.2 -- -- 100/100 463/369 3.1/2.5 -- -- 100/100 397/419 1.9/2.0 100/75 187/248 100/100 172/125 0.8/0.6 100/100 96/93 100/100 178/141 0.8/0.7 100/100 79/128 100/100 175/359 0.9/1.9 100/100 45/34 100/100 175/197 0.8/0.9 100/100 22/28 100/100 188/159 0.9/0.8 100/100 32/26 0.3/0.3 0.3/0.3 0.2/0.2 1.2/0.9 0.1/0.1 1.3/0 0. i/0.5 0.3/0.4 0.1 0.5 0.1 0.5 0.3/0.3 02/0.2 02/0.2 0.3/0.3 0.4/0.5 0.4/0.4 0.4/0.4 0.1/0.1 O.t/O.l 0.0/0.1 0.1/0.1 0.1/02 0.3/0.3 0.4/0.6 0.8/0.9 0.0/0.0 02/0.5 0.2/02 0.2/02 0.1/0.1 1.9/1.3 2.5/1.5 0.9/1.0 2.7/2.0 __ Q.4/0.4 0.3/0.4 1.1/1.1 Q.3/0.3 0.8 0.3/0.7 1.4/1.8 1.4/1.5 -- _ -- 0.6/0.8 0.3/0.3 0.3/0.4 0.1/0.1 0.1/0.1 0.1/0.1 NIOSH-AIA method No. of fields fmm"2 fml~ ___ 100 too 100 100 100 100 100 100 _100/100 __ 100/100 ___ 100/100 100/100 ____ _ 100/100 _100/too 100/100 100/100 100/100 100/100 too/100 100/100 100/100 - _ _ 31 138 57 55 51 127 63 97 86/62 __ __ 56/53 __ 82/84 132/102 ___ __ ___ 144/55 7/12 ___ 129/137 160/178 114/125 175/114 87/108 37/44 61/75 ___ -- 02 0.9 0.4 0.4 02 0.6 0.4 0.6 0.4/0.3 __ 0.2/0.3 ___ 0.4/0.4 0.7/0.5 __ __ ___ 0.7/0.3 0.0/0.0 ___ 0.6/0.6 0.8/08 0.6/0.8 0.5/0.3 0.3/0.3 0.1/0.1 02/0.2 -- __ __ __ __ __ __ ___ ___ 100 100 50 50 100 100 50 100/75 ___ 100/100 100/100 ___ 100/100 __ __ __ __ __ __ ___ ___ ___ 67 38 381 375 32 82 264 199/233 -- 65/62 84/95 ___ 39/48 __ __ __ __ __ ___ ___ ___ 0.5 02 2.4 2.6 0.3 0.6 1.8 0.9/1.I ___ 0.3/0.3 0_.4/0.5 02/02 {continued Comparison of AIA and NIOSH methods on asbestos 373 Table At.--(continued) NIOSH method No. of fields fmm"1 fml-1 No. of fields AIA method fmm"! fml-1 100/100 100/100 100/100 100/100 75/56 44/91 153/144 175/109 0.8/0.6 0.2/0.4 0.8/0.7 0.9/0.6 100/100 100/100 100/100 100/100 Workplace sampled: small pipe turning 100/100 225/197 1.7/1.5 75/100 100/100 331/353 2.1/2.3 75/50 100/100 88/169 0.6/1.0 -- 100/100 94/81 0.6/0.5 -- 100/100 297/209 1.4/1.0 100/100 100/100 347/297 1.6/1.4 100/100 100/100 703/759 3.3/3.6 75/100 100/100 212/344 1.1/1.8 100/100 100/100 66/109 0.3/0.6 100/100 100/100 31/47 0.3/0.5 100/100 100/100 137/119 0.7/0.5 100/100 100/100 222/219 1.1/1.1 100/100 Workplace sampled: pipe cutting 100/100 175/159 2A/2.2 100/100 213/181 4.0/3.4 100/100 197/181 3.7/3.5 100/100 119/125 2.5/2.7 100/100 444/328 2.8/1.4 100/100 306/281 2.2/2.Q 100/100 463/450 5.7/S.6 100/100 503/513 4.8/4.9 100/100 350/313 3.1/2.8 100/100 138/125 0.7/0.6 100/100 431/525 2.3/2.S 100/100 366/303 1.7/1.4 100/100 325/303 1.5/1.5 100/100 81/50 0.3/0.2 100/100 113/191 0.6/1.1 100/100 100/100 100/100 100/100 50/50 75/100 75/50 50/25 50/50 -- 75/100 100/100 100/100 100/100 100/100 27/25 39/40 24/38 94/35 155/141 175/268 -- -- 68/63 106/106 254/215 113/160 47/23 22/24 52/54 94/55 29/44 60/42 84/86 35/37 241/357 159/121 228/373 538/562 331/321 -- 146/116 49/49 106/126 80/83 41/61 0.2/0.2 0.1/0.1 0.1/0.1 0.3/0.1 0.7/0.7 0.7/1.1 -- -- 0.2/0.2 0.3/0.3 0.8/0.7 0.4/0.5 0.1/0.1 0.2/0.2 0.1/0.2 0.3/0.2 0.3/0.4 0.7/0.5 1.0/1.0 0.5/0.5 1.0/1.4 0.7/0.6 1.8/3.0 3.3/3.4 1.9/1.9 -- 0.6/0.5 0.1/0.1 0.3/0.3 0.3/0.3 0.1/0.2 NIOSH-AIA method No. of fields fmm-1 fml-1 100/100 -- 100/100 100/100 19/31 -- 59/46 70/58 Q-2/0.4 -- 0.2/0.2 0.4/0.3 75 75 too 100 -- 100/100 50/50 100/100 100/100 -- 100/100 100/100 206 184 11 87 -- 88/68 268/371 122/109 25/39 -- 28/23 75/87 1.5 1.2 0.1 0.5 -- 0.4/0.3 1.3/1.8 0.7/0.5 0.2/02 -- 0.1/0.2 0.4/0.4 -- -- -- -- -- -- 50 50 75 100 100 100/100 100/100 100 100/100 -- -- -- -- -- -- 256 318 157 29 193 73/86 91/87 34 100/73 -- -- -- -- -- -- 3.2 3.0 1.5 0.1 1.1 0.4/0.4 0.4/0.4 0.2 0.5/0.4