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FILE NAME Packings and Gaskets PAG DATE 2000 DOC PAG017 DOCUMENT DESCRIPTION Journal Article - Exposures to Asbestos Arising from Bandsawing Gasket Material Applied Occupational and Environmental Hygiene Volume 15 404-408 2000 Copyright '2000 Applied Industrial Hygiene 1047-322X 12.00 + .00 Exposures to Asbestos Arising from Bandsawing Gasket Material Douglas P. Fowler Fowler Associates Occupational and Environmental Health Services Inc. Redwood City California Applied Occupational and Environmental Hygiene Volume 15 404-408 2000 Copyright ':2000 Applied Industrial Hygiene 1047-322X 12.00 + .00 Exposures to Asbestos Arising from Bandsawing Gasket Material Douglas P. Fowler Fowler Associates Occupational and Environmental Health Services Inc. Redwood City California A simulation of bandsawing sheet asbestos gasket material was performed as part of a retrospective exposure evaluation undertaken to assist in determining causation of a case of mesothelioma The work was performed by bandsawing a chrysotile asbestos 80 neoprene gasket sheet with a con- ventional inch woodworking bandsaw inside a chamber Measurements of airborne asbestos were made using con- ventional area and personal sampling methods with analysis of collected samples by transmission electron microscopy TEM and phase contrast microscopy PCM These were supplemented by qualitative scanning electron microscopy SEM examinations of some of the airborne particles collected on the filters In contrast with findings from studies examining manual handling installation and removal of gaskets airborne asbestos concentrations from this operation were found to be well above current Occupational Safety and Health Administration OSHA permissible exposure limit PEL eight weighted average TWA ] and excur- sion limit minute standards Although some encapsulation effect of the neoprene matrix was seen on the particles in the airborne dust unencapsulated individual fiber bundles were also seen Suggestions for the implications of the work are given In summary the airborne asbestos concentrations arising from this work were quite high and point to the need for careful observation of common sense pre- cautions when manipulation of containing materials even those believed to have limited emissions potential may involve machining operations Keywords Asbestos Gasket Bandsaw Exposure An industrial hygiene evaluation was undertaken of the lifelong asbestos exposure of a plaintiff who had filed a lawsuit against a number of defendants formerly or currently involved in the manufacture or distribution of containing materials The plaintiff had been diagnosed with pleural mesothe- lioma Among other jobs over his lifetime the plaintiff had been assigned to work by one of his employers in the 1960s that involved the bandsawing of large numbers of gaskets from sheets of a impregnated gasket material These gaskets were stacked to form a thick layer of insulation for a specific piece of heating equipment used in the aerospace industry during certain kinds of engine tests No reports of similar work were found in the industrial hygiene literature although several reports of exposures during conventional manual handling installation and removal of single gaskets from piping and ancillary fittings were identified 1-4 In some of these there were some discussions of the impact of machining work with a few measurements but with no specific testing of bandsawing Accordingly a simulation ofthis specific task was undertaken to fill this gap because the same gasket used by the plaintiff was found to still be available commercially The primary issue in question was the probable asbestos ex- posure of the plaintiff during this specific job A secondary issue was the condition of the airborne particles because some experts retained by one side or the other in the asbestos litigation have opined that matrices such as the neoprene in this gasket will encapsulate fibers and fiber bundles thus preventing biologically harmful exposure Other experts of course have different opinions METHODS AND MATERIALS The material examined was a impregnated sheet gasket 0.3175 cm 1/8 inch thick The asbestos content of the gasket as stated by the manufacturer was 80 percent chrysolile The gasket was delivered from the manufacturer as a tightly rolled 101.6 ^ 365.76 cm 40 ^ 144 inches sheet in corrugated paper wrapping The outer wrapping bore a warning label as shown in Figure 1. Note that the label warnings specifically proscribe sawing as performed here Cutting of the sheet to convenient size for bandsawing 101.6 ^ 60.96 cm 40 ^ 24 inches was performed with a Sears Craftsman saber saw with a conven- tional wood sawing blade ~ teeth 10 teeth per inc-h- tpi The bandsawing was done with a Reliant Model EE 166 16 inch 40.64 cm cutting bandsaw with the original blade 404 ASBESTOS EXPOSURE FROM BANDSAWING GASKET MATERIAL 405 r a| WARNING NAME COMPRESSED ASBESTOS GASKET MATERIAL This product contains asbestos and has been defined by the EPA as Category | NONFRIABLE asbestos containing material In order to effect a clean cut smooth edge on the gasket and to minimize dust created in cutting we recommend that all cutting equipment such as dies shears strippers snips and blades etc. be maintained as sharp as possible Avoid drilling grinding sawing sanding or other dust producing processes After use remove gaskets from flanges with an approved gasket removal agent NAME MANUFACTURING COMPANY Address FIGURE 1 Warning label on roll of sheet - oi rigningal size and typography supplied by the manufacturer approximately 3 teeth cm 7 tpi operated on the middle speed 609.6 sec = 120 1200 minute of the three available on the saw The work was done inside a specially constructed chamber built of 0.01524 = 0.006 inch- mil polyethylene sheeting walls with a double layer of 0.0254 cm 10 mil polyethylene for the floor The chamber was constructed with a large work area chamber 363.2 cm L ^ 188 cm W ^ 269.2 cm H = 18.38 m== 143 L ^ 74 W ^ 106 H 649 cubic feet and an entrance divided into two smaller chambers The two smaller chambers were a clean room leading from the main laboratory area which led into a dirty room or equipment room leading into the work area chamber Each small entrance chamber was approximately 102 cm ^ 127 cm ^ 269 cm 40 x 50 x 106 The entire chamber was ventilated during all sawing by drawing air into the entry of the clean room with a Nilfisk Model GS 80 filtered vacuum cleaner placed at the end of the chamber farthest from the entry The air flow rate was approximately 0.99 1.1c3ubic meters per minute 3540 cubic feet per minute for an air exchange rate of 3.2-3.7 air changes per hour ACH All sawing work was done by the author wearing disposable garments over street clothes and a properly fitted mask respirator with HEPA filter cartridges is noted that this level of protection does not meet the modern protective measures required by the Occupational Safety and Health Administration OSHA for cutting containing materials Please refer to the conclusions for recommendations for personal protective measures for this work Three types of sawing were done First the large roll of stiff material was cut with a saber saw to reduce the pieces for test to approximately 61 cm ^ 102 cm rectangles Secondly the large rectangles were cut on the bandsaw to smaller rectangles each about cm x cm Thirdly each ofthe smaller rectangles was cut in half on the bandsaw All sawing was of single thicknesses of the gasket material Air samples were taken during the work as personal breath- ing zone samples and area samples The samples were taken by drawing air through mixed cellulose ester filters in three- piece conductive air sampling cassettes 25 millimeter diame- ter 0.45 micrometer nominal pore size inch cowl obtained from Safety Environmental Control Inc. Keene New Hamp- shire Catalog # 203000182 Lot # 9601081 The personal samples were taken with SKC operated sampling pumps at flow rates of 2.0 and 2.55 liters per minute The area samples were taken with Dawson 110 volt pumps operated at 11.5 and 10.85 liters per minute Each sampling train was calibrated be- fore and after each sample by determining the total volumetric flow rate through the train with a rotameter calibrated less than one month prior to the evaluation with a Spectrex BFM 4000 primary volumetric standard The personal breathing zone samples were taken by placing the sampling cassettes in the author's breathing zone clipped to his clothing so that the opening was near his nose and mouth The area sampling locations were at breathing zone height 152 18c3m above floor level with one placed to the left of the bandsaw in the pathway between the saw and the exhaust inlet and the other placed behind the bandsaw in location undis- turbed by either the sawing or the air flow Both were approxi- mately 60-90 cm horizontally from the bandsaw blade Three sets of samples were taken During the saber saw cut- ting to reduce the sheet to manageable pieces for bandsaw- ing a single personal sample A was taken from the right side of the operator's breathing zone The second set of samples was taken during the cutting of the two large pieces to smaller pieces approximately 12 cm x 15 cm samples B to E. That cutting was interrupted by a power failure for a few minutes as indi- cated on Table I. The third set of samples was taken during the cutting for a few minutes of the 12 cm x 15 cm pieces into halves samples F to J no G used Each filter was analyzed by phase contrast microscopy PCM Each was also evaluated for its suitability for further analysis by transmission electron microscopy TEM All ex- cept two samples D and E were deemed to be suitable for such analysis Samples D and E were too heavily loaded for direct analysis Rather than prepare the samples for analysis by an indirect preparation method with consequent splitting of fiber bundles and magnification of the asbestos structure counts the samples were not further analyzed In addition some par- ticles from the samples were examined by scanning electron microscopy SEM and photomicrographs were taken to il- lustrate the condition and character of the particles collected sec Figures 2 and 3 for examples RESULTS The results are shown in Table 1. The personal exposures to fibers longer than 5 micrometers ...mduring bandsawing were between 2.2 and 4.9 fibers per milliliter mL by PCM where the current OSHA eight TWA standard is 0.1 niL and the minute excursion limit is 1.0 mL The personal results by TEM were higher 22.2 49.a3sbestos structures per milliliter 406 D. P. FOWLER TABLE I Exposures to airborne asbestos fibers and structures during sawing of inch asbestos sheet gasket Concentrations Sample # A B C D E F H I J Time Activity 1321-1333 Saber sawing flattening sheet 1510-1519 1524-1545 Bandsawing 1510-1519 1524-1545 Bandsawing 1511-1515 | Bandsawing 1524-1545 1511-1515 1524-1545 Bandsawing 1555-1601 1555-1601 1555-1602 1554-1602 Bandsawing Bandsawing Bandsawing Bandsawing Area personal Personal Location R. side BZ Personal _ R. side BZ Personal _ L. side BZ Area Back of saw Area Side of saw Area Back of saw Area Side of saw Personal R. side BZ Personal _ L. side BZ Duration minutes 12 30 30 25 25 6 6 7 8 Volume liters 24 60 76.5 287.5 271.3 69 65.1 14 20.4 PCM ml 0.11 TEM total ml 0.62 TEM > ...m mL 0.21 3.1 22.2 8.2 2.2 26.4 9.7 0.75 Overload Overload 0.96 Overload Overload 1.8 14.3 2.3 22.7 4.9 49.3 3.1 43.5 5.7 7.6 17.6 9.7 FIGURE 2 Scanning electron micrograph @ 500x showing mostly unencapsulated fibers FIGURE 3 Scanning electron micrograph @ 450x showing many encapsulated fibers ASBESTOS EXPOSURE FROM BANDSAWING GASKET MATERIAL 407 mL for all asbestos structures and 8.2-17.6 mL for those asbestos structures longer than 5 ...mThe area samples showed results somewhat lower than the personal samples as would be expected For the PCM analyses the area sample results were between 0.75 and 2.3 mL The TEM area results were 14.3 and 22.7 ml for total structures and 5.7 and 7.6 mL for those structures longer than 5 ...min the two samples that could be analyzed DISCUSSION The concentrations of airborne fibers longer than 5 ...mmeasured by PCM in the breathing zone of the operator during bandsawing of this material are well above the current OSHA Permissible Exposure Limit PEL eight TWA standard for occupational exposure to asbestos of 0.1 mL and the OSHA minute excursion limit of 1.0 mL For the area samples taken close to the bandsaw the concentrations were all well above the TWA PEL and two of four were above the excursion limit as well The other two samples at 0.75 and 0.96 mL were near to the excursion limit The concentrations of asbestos structures measured by TEM both total and those larger than 5 micrometers in their longest dimension were well above the fiber concentrations measured by PCM and were significant and substantial The concentrations of airborne structures de- termined from the filters with the highest surface loadings of fibers and asbestos structures were lower than for those taken in the same general locations but which had lower loadings This may indicate that there was some obscuration of asbestos particles by overlying particles in the more heavily loaded samples and that these results may therefore understate the actual con- centrations The air flow through the chamber 3.2-3.7 ACH was higher than is sometimes found in machine shops or other similar settings and thus these results may understate actual potential exposures for this reason as well However the fact of enclosure will act to restrict dilution and the concentrations reported here may thus be higher than would be expected in a real life setting As can be seen in Table , the saber sawing did not produce measureable airborne asbestos However the detection limit of the method was relatively high because of the short sampling period and relatively low concentrations were measured by TEM Based on the ratios of total and > ...mTEM structures to PCM fibers in the other sets of samples it is estimated that the PCM concentration in Sample A would have been in the range of 0.04-0.09 mL if a sufficient air volume had been collected The periods of exposure at the measured concentrations that would have been required to exceed the OSHA standards using the PCM personal BZ results have been calculated for the extremes of the range of those measurements If one was ex- posed to a concentration of 2.2 mL a period of approximately 22 minutes would suffice to produce an eight TWA exposure of 0.1 mL with no other exposure For 4.9 mL only about 10 minutes would be required With regard to the 30minute excursion limit of 1.0 mL 14 and 6 minutes would be required to exceed it at 2.2 and 4.9 mL respectively If the maximum concentration found for the TEM > ...mpersonal BZ measurements 17.6 mL was similarly considered less than 3 minutes would be required to exceed both the PEL and the excursion limit The findings here are reasonably consistent with the findings of others who have studied asbestos exposures during gasket handling involving machining of gaskets That is that power machining wire brushing old gaskets with a wire disc grinder to remove adherent material from the gasketed surface is the most common machining operation may generate appre- ciable concentrations of airborne asbestos fibers in the range of 0.5-5.0 mL by PCM although normal hand cutting does not usually cause such high concentrations As can be seen in Figures 2 and 3 there is support for both sides in the fiber encapsulation dispute Some of the fibers and fiber bundles do appear to be largely encapsulated by the amorphous neoprene matrix However some others are not and one can easily see asbestos fiber bundles that are free of the neoprene Those figures also however show that at least some of the fibers are agglomerated into large particles that could not under any reasonably foresceable set of circumstances be considered respirable Even though the hand cutting or other manual handling of this or similar products cannot be guaranteed free from significant risk of asbestos exposure the importance of observing label instructions is illustrated here Any machining operation on any containing product may be accompanied by the production of excessive concentrations of airborne asbestos if sufficient energy is applied to the product Another way of expressing this is to state that friability is always relative to the energy applied Finally this material was purchased for this study in October 1996. Accordingly users of gaskets are warned that asbestos is not a material of the past but is available on the open market today Given the concentrations measured here and the comparability of these results with measurements of others it will be important to verify that appropriate precautions are taken to prevent exposure to asbestos if this or similar products are viewed as being so essential that a asbestos substitute cannot be used in their place CONCLUSIONS Based on this study it appears likely that similar usage of this or similar sheet gaskets may have caused significant asbestos exposures during its past and current applications It is unknown how frequently such work was done or is being done now although it has not been reported previously However if many duplicate gaskets were or are to be produced the possibility of bandsaw usage should be investigated because the expected 408 D. P. FOWLER asbestos concentrations from such usage will be orders of mag- nitude above those generated by hand work The most desirable control will be to disallow the use of this or any similar asbestos gasketing material in the workplace Where it must be used the label restrictions given in Figure 1 should be observed at a minimum If machining such as that reported here is expected it is recommended that controls similar to those used in this study negative pressure enclosure supplemented by respiratory protection and protective clothing should be the minimum requirements Where similar kinds of activities are carried out in a workplace setting the requirements of the OSHA asbestos regulations should be carefully followed Conventional local exhaust ventilation and enclosure will almost certainly be the most effective control measure if properly designed and implemented Because of the concentrations found here the relevant OSHA personnel should be consulted to ap- prove the measures to be taken Based on the TEM concentrations reported here up to almost 50 mL for total structures and up to almost 18 mL for those > ...mpressure demand supplied air systems would appear to be the only appropriate respiratory protection Even if the PCM results are accepted as an appropriate index of risk and it is assumed that respiratory protection allowing mask concen- trations as high as 0.01 mL may be used some formof supplied air system will be required to meet the implicit protection factor requirement of 500 Of course if is assumed that the most appropriate workplace exposure standard for asbestos is the usual ambient concentration then a protection factor of > 5000 will be needed to make the mask concentration 0.001 mL or below to meet today's ambient concentrations Clearly substitution is the most desirable control and prohibition of power machining would be next most desirable ACKNOWLEDGMENTS The original work was funded by the law firm of Galiher DeRobertis Nakamura and Ono of Honolulu Hawaii representing the plaintiff and his family The laboratory analyses were performed by Bernard Thomas of the R.J. Lee Group Inc. in San Leandro California REFERENCES 1. Cheng R. McDermott H.J Exposure to Asbestos from Asbestos Gaskets Appl Occup Environ Hyg 588 5911991 2. McKinnery W.N Moore R.W Evaluation of Airborne Asbesios Fiber Levels During Removal and Installation of Valve Gas- kets and Packing Amer Ind Hyg Assoc Journ 531-532 1992 3. Spence S.K Rocchi P.S.J Exposure to Asbestos Fibers During Gasket Removal Ann Occup Hyg 583 5818996 4. Liukonen L.R Still K.R Beckett R.R Asbestos Exposure from Gasket Operations Industrial Hygiene Branch Naval Regional Medical Center Bremerton WA May 1978 5. National Institute for Occupational Safety and Health NIOSH Asbestos and Other Fibers by PCM - Method 7400. NIOSH Manual ofAnalytical Methods- 4th Edition DHHS NIOSH Publ No. 94- 113. NIOSH Cincinnati OH 1994 6. Environmental Protection Agency EPA Containing Materials in Schools Interim Transmission Electron Microscopy Methods Title 40 Code of Federal Regulations Part 763 Subpart E. Appendix A 1987 7. R.J. Lee Group Inc Personal SEM v 3.11 R.J. Lee Group Mon- roeville PA 1996 8. Occupational Safety and Health Administration OSHA Asbestos Construction Standard Title 29 Code of Federal Regulations Part 1926.1101 General Industry Standard Title 29 Code of Federal Regulations Part 1910.1001 1999