Document qaX9a3g8x5448NKLnxxBokb4j

ved 5/ 3/00 1 6PM; Page Applicil Occupational uiul Kiivinwwncnuil Volume I.Si.Si: 404-40X. 2000 UipynjilH ' 200(1 Applied tndurtriol Hygiene I'UVV^XAiO S12.00+ .00 Exposures to Asbestos Arising from Bandsawing Gasket Material Douglas P. Fowler Fowler Associates Occupational and Envimnmental Health Services. Inc~ Redwood City. Californio A simulation of bandsawing sheet asbestos gasket mate* rial was performed as pan of a retrospective exposure evalu ation undertaken to assist in determining causation of a case of nu-M.im iioiiia. The work was performed by bandsawing a chrysntilc u.sliestos (#0%)/neoprene gasket sheet with a con ventional 16-inch woodworking bandsaw inside a chamber. Measurements of airborne asbestos were made using con ventional area and personal sampling methods, with analy sis of collected samples by transmission electron microscopy (TEM) ami phase contrast microscopy (PCM). These were supplemented by qualitative scanning electron microscopy (SEM) examinations of some of the airborne particles col lected on the filters. In contrast with findings from studies ex amining manual handling (installation and removal) of gas kets. airborne asbestos concentrations from this operation w ere found to be well above current Occupational Safety and Health vdministratioi\,(OSHA) permissible exposure limit (PEL) (eight-hour time-weighted average [TWA]) and excur sion limit (30-minute) standards. Although some "encapsu lation" effect ofthe neoprene matrix was seeq on the particles in the airborne dust, unencapsulated individual fiber bun dles were also seen. Suggestions for the implications of the work are given. In summary, the airborne asbestos concen trations arising from this work were quite high, and point to the need for careful observation of common sense pre cautions when manipulation of asbestos-containing materi als (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 life long 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 asbestos-containing ma terials. The plaintiff had been diagnosed with pleural mesothe lioma. Among otherjobs over his lifetime, the plaintiff had been assigned to work by one of his employers in the 1*>60s that in volved the bandsawing of large numbers of gaskets from sheets of a neoprene-impregnated gasket material. These gaskets were sucked 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 hy giene literature, although several repons of exposures during conventional manual handling (installation and removal) of sin gle gaskets from piping and ancillary linings were identified.'1 Jl 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. According)), u simulation of this specific task was undertaken to fill this gap. because the same gasket used by the plaintiff was found to still he available commercially. The primary issue in question was the probable asbestos ex posure of the plaintiff during this specific jnh. A secondary issue was the condition ofthe 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'1 fibers and fiber bundles, thus preventing biologi cally harmful exposure. Other experts, of course, have different opinions. METHODS AND MATERIALS The material examined was a neoprene-impregnated sheet gasket. 0.3175 cm (l/R inch) thick. The asbestos content of the gasket as stated by the manufacturer was KO percent chrysolite. The gasket was delivered from the manufacturer as u tightly rolled 101.6 x 365.76 cm (40 x 144 inches) sheet in corrugated paper wrapping. The outer wrapping bore a wanting label as shown in Figure 1. (Note that the label warnings specifically pro scribe sawing as performed here.) Cutting of the sheet to conve nient size for bandsawing ()()] .6 x 60.% cm - 40 x 24 inches) was performed with a Sears Craftsman saber saw, with a conven tional wood sawing blade (--4 teeth/cm = 10 teeth per inchtpi). The bandsawing was done with a Reliant Model EE I fib 16 inch (40.64 cm) wood-cutting bandsaw, with the original blade 404 Received: / *. / > 3 1;i7PM; - 7700663239; Page 3 ASBESTOS EXPOSURE FROM BANDSAWING GASKET MATERIAL r-------- - ! WARNING | (NAME) COMPRESSED ASBESTOS GASKET MATERIAL I Thl product contain* aabeatos and haa been defined by the EPA ! aa Catagoty I NONfHlABLT astteatp* containing material, tn order to ffact a ctaan cut, amooth adga on trie gatket. and to tnMntim dual oaatad In cutting, we recommend that all cutting equipment such aa ttlaa, aheei*. atrippere. anlpa and btadea, ate. be maintained as sharp aa poeeibie. Avoid driMng. grinding, tawing, l sanding, or other duet producing txoceaaes. After uaa. ramove | gaaket* ftom ftangaa wWi an approved gasket removal agent. by drawing air through mixed cellulose ester lilifts hi Hire piece conductive air sampling cassettes (25 millimeter diam ter. 0.45 micrometer nominal pore si/c. 2-inch cmvlt obtain:, from Safety Environmental Control. Inc. (Keene New Hani| shire) (Catalog 0 203000182. I.ot VMllDKli. The person, samples were taken with SKC battery-operated sampling pump at flow rates of 2.0 anti 2.55 liters per minute The area sample were taken with Dawson 110 volt pumps operated at 11.5 an 10.85 liters per minute. Each sampling train was calibrated be fore and after each sample by determining the total Millimetre 1 (NAME) MANUFACTURING COMPANY flow rate through the train with a rotameter (calibrated less Hut: AddrcH one month prior to the evaluation with a Spectres HIM 4iioi primary volumetric standard). FIGURE 1 The personal breathing zone samples were taken by placiiu 1 in- CCIS Warning label on roll of sheeting--original size and typography. the sampling cassettes in the author's breathing /one 'clippc, to his clothing so that the opening was near his nose and mouth1 The area sampling locations were- at breathing /one heigh: ere Ot tain supplied by the manufacturer (approximately 3 teeth/cm ~ 7 tpi) operated on the middle speed (609.6 cm/sec = 1200 feet/minute) of the three available on the saw. (152-183 cm above floor level) with one placed to the left <v the bandsaw in the pathway between the saw ami the exhaust inlet and the other placed behind the bandsaw in a location nndis. hyini: wn- i. The work was done inside a specially constructed chamber built of 0.0l524-cm-tbick t= 0.006 inch--"6 mil'*) polyethy lene sheeting walls, with a double layer of 0.0254 cm (10 mil) polyethylene for the floor. The chamber was constructed with a turbed by either the sawing or the air flow. Doth were approxi mately 60-90 cm horizontally from the handsaw blade. Three sets of samples were taken. During the saber saw cut ting to reduce the sheet to manageable-size pieces for handsaw. : of ific ific ;cd large work area chamber (363.2 cm L x 188 cm W x 269.2 cm H = 18.38 nr1 = 143" L X 74" W x 106" H a* 649 cubic feet), and an entrance divided into two smaller chambers. The two smaller chambers were a "dean room" leading from the main ing, a single persona) sample t AI w as taken front the right side of the operator's breathing zone. The second set of samples w n taken during the cutting of the two large pieces n> smaller pieces (approximately 12 cm x 15 cm), (samples I) to I;, i Thai cutting laboratory area, which led into a "dirty room" or "equipment was interrupted by a power failure for a lew minutes, as indi room" leading into the work area chamber. Each small en cated on Table I. The third set of samples was taken during the uo trance chamber was approximately 102 cm x 127 cm x 269 cm cutting (for a few minutest of the 12 cm x 15 cm pieces into ns (40" x 50" x 106"). The entire chamber was ventilated during halves, (samples F to J. no G used.) vc all sawing by drawing air into the entry of the clean room with Each filter was analyzed by phase contrast microscopy ill a Nilfisk Mode) GS 80 HEPA-Altered vacuum cleaner placed (PCM).'" Each was also evaluated for ' sunahilin tor further li at the end of the chamber farthest from the entry. The air flow analysis by transmission electron microscopy t n-Mi."" All ex nt rate was approximately 0.99-1.13 cubic meters per minute (35-- cept two samples (D and E) were deemed to be suitable lor such 40 cubic feet per minute), for an air exchange rate of 3.2-3.7 analysis. Samples D and E were too heavily loaded lor direct air chances per hour (ACH). All sawing work was done by the analysis. Rather than prepare the samples for analysis by an author, wearing disposable garments over street clothes, and a indirect preparation method with consequent splitting of fiber properly fitted half-mask respirator with HEPA filter cartridges. bundles and "magnification" of the ashoi..- i".u turc counts, ex It is noted (hat this level of protection does not meet the modem the samples were not further analyzed, in addition, some par \c protective measures required by the Occupational Safety and ticles from the samples were examined by scanning electron if Health Administration (QSHA) for cutting asbestos-containing microscopy (SEM).'7' and photomicrographs were taken to il y d materials. Please refer to the conclusions for recommendations lustrate the condition and character of flic particles collected t see for personal protective measures for this work. Figures 2 and 3 for examples). is Three types of sawing were done. First, the large roll of stiff 1- material was cut with a saber saw to reduce the pieces for test to approximately 61 cm x 102 cm rectangles. Secondly, the large RESULTS ) rectangles were cut on the bandsaw to smaller rectangles, each The results are shown in Tabic I. The personal exposures to about 12cm x 15cm.Thirdly.eachofthesmalierrectangieswas fibers longer than 5 micrometers (/tmi during h.-tiulsawing wore cut in half on the bandsaw. All sawing was of single thicknesses between 2.2 and 4.9 libers per milliliter tl'/rnl.) by PCVt where i of the gasket material. the current OSHA eight-hour TWA standard is 0,1 I'/ntl,. and the Air samples were taken during the work as personal breath 30-minuic excursion limit is ).() 17ml.. The ftcrsonul results lw ing /one samples and area samples. The samples were taken TEM xverc higher: 22.2-4V.3 asbestos structures per milliliter Received: 5/ 3/00 1:17PM; -> 7708663250; Paoe A 406 D. P. POWI.KK TABLE I Exposures to airborne asbestos fibers and structures during sawing of I /K-nu.-h asbestos sheet gasket Coiiccntnuiotis Sample # Time Activity Area/ personal Location A 1321-1333 Saber sawing/ Personal R. side BZ flattening sheet B 1540-1519 Bandsawing Personal R. side BZ 1524--1545 C 1510-1519 Bandsawing Personal L. side BZ 1524-1545 D 1511-1515 Bandsawing Area Back of saw 1524-1545 E 1511-1513 Bandsawing Area Side of saw 1524-1545 F 1555-1601 Bandsawing Area Back of saw H 1555-1601 Bandsawing Area Side of saw 1 1555-1602 Bandsawing Personal R. side BZ J 1554-1602 Bandsawing Personal L. side BZ Duration (minutest 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 f/ntl. -.0.11 3.1 2.2 0.75 0.96 1.8 2.3 4.9 3.1 TKM (total) s/inl. 0.62 26.4 Overload Overload 14.3 22.7 49.3 43.5 TKM t -5 //mi vml. 0.21 S.2 9.7 Overload Overload 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. Receivec 5/ 3/00 1 :18PM; -> 7-708663250; Page 5 ASBESTOS EXPOSURE FROM BANDSAWINO GASKET MATERIAL 4> (s/mL) for all asbegro structures and 8.2-17.6 s/mL for those about 10 minutes would be required. With regard to the 3 asbestos structures longer than 5 /am. The area samples showed minute excursion limit of 1.0 f/ml.. 14 and 6 minutes would t results somewhat lower than the personal samples, as would be required to exceed it at 2.2 and 4.9 f/ml.. respectively If it- expected. For the PCM analyses, the area sample results were maximum concentration found for the THM -5 //in person; between 0.75 and 2.3 f/mL. The TEM area results were 14.3 and BZ measurements (17.6 f/mL) was similarly considered, le- ' 22.7 s/mL for total structures, and 5.7 and 7.6 s/mL for those than 3 minutes would be required to exceed both the PHI, an structures longer than 5 /zm in the two samples that could be the excursion limit. analyzed. i The findings here are reasonably consistent with the find ings of others"*1 who have studied asbestos exposures durin; DISCUSSION The concentrations of airborne fibers longer than 5 /zm mea sured (by PCM) in the breathing zone of the operator during bandsawing of this material are well above the ament OSHA Permissible Exposure Limit (PEL) eight-hourTWA standard for occupational exposure to asbestos of 0.1 f/mL. and the OSHA 30-minute excursion limit of 1.0 f/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 die excursion limit as well. (The other two samples, at 0.75 and 0.96 f/mL, were near to the exclusion limit.) The concentrations ofasbestos 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 gasket handling involving machining of gaskets. That is. tha power machining (wire brushing old gaskets with a wire disi 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 ol --0.5-5.0 f/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 lor 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 arc 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 substantial. The concentrations of airborne fibers/structures de not, under any reasonably foreseeable set of circumstances, be termined from the filters with the highest surface loadings of considered respirable. fibers and asbestos structures were lower than for those taken in Even though the hand cutting or other manual handling of the same general locations, but which had lower loadings. This this or similar products cannot be guaranteed free from signif may indicate that there was some obscuration of asbestos parti icant risk of asbestos exposure, the importance of observing cles by overlying panicles in the more heavily loaded samples, label instructions is illustrated here. Any machining operation and that these results may therefore understate the actual con on any asbestos-containing product tnav be accompanied by the centrations. The air flow through the chamber (3.2-3.7 ACH) production of excessive concentrations of airborne asbestos, if ! was higher than is sometimes found in machine shops or other sufficient energy is applied to the product. Another way of ex j similar settings, and thus these results may understate actual pressing this is to state that "friability" is always relative to the I potential exposures for this reason as well. However, the fact energy applied. of enclosure will act to restrict dilution, and the concentrations Finally, this material was purchased for this study in October. reponed here may thus be higher than would be expected in a 1996. Accordingly, users of gaskets are warned that asbestos is "real life" setting. not a material of the past, but is available on the open market ; As can be seen in Table I. the saber sawing did nor pro today. Given the concentrations measured here, and the compa duce PCM-measureable airborne asbestos. However, the detec rability of these results with measurements of others, it will be tion limit of the method was relatively high because of the short important to verify that appropriate precautions are taken to pre \ sampling period, and relatively low concentrations were mea- vent exposure to asbestos, if this or similar pri'dnct-. arc viewed i sured by TEM. Based on the ratios of total and >5 /zm TEM as being so essential that a non-asbestos subsinuie cannot be structures to PCM fibers in the other sets of samples, it is es- used in their place. ! timated that the PCM concentration in Sample A would have been in die range of 0.04-0.09 f/mL. if a sufficient air volume ! had been collected. CONCLUSIONS | The periods of exposure at the measured concentrations that Based on this study, it appears likely that similar usage of this would have been required to exceed the OSHA standards us or similar sheet gaskets may have caused significant asbestos ex ing the PCM personal BZ results have been calculated for the posures during its past and current applications. It is unknown extremes of the range of those measurements. If one was ex how frequently such work was done (or is being done now), posed to a concentration of 2.2 f/mL, a period of approximately although it has not been reponed previously. However, if many 22 minutes would suffice to produce an eight-hour TWA expo duplicate gaskets were or are to be produced, the possibility sure of 0.1 f/mL. with no other exposure. For 4.9 f/mL. only of bandsaw usage should be investigated, because the expected r ece ivec: 5/ 3/00 1:1PM; -> 7708863259; Pafl 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 re ported here is expected, it is recommended chat controls similar to those used in this study (negative pressure enclosure, supple mented by respiratory protection and protective clothing) should be the minimum requirements. Where similar kinds of activi ties 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 de signed 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 s/mL for total structures, and up to almost 18 s/mL for those >S umi pressure 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 in-mask concen trations as high as 0.01 f/roL may be used, some form of supplied air system will be required to meet the implicit protection factor requirement of --500. Ofcourse, if it is assumed that the most ap propriate workplace exposure standard for asbestos is the usual ambient concentration, then a protection factor of >5000 will be needed to make the in-mask concentration 0.001 f/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 ol Cialiher. DeRobertis. Nakamura, and Ono of Honolulu. Hawaii, repre senting the plaintiff and his family. The laboratory analyses were performed by Bernard Thomas of the R J. I-ee Group. Inc. in San Leandro, California. REFERENCES 1. Cheng. R.T.: McDermott. H.J.: Exposure to Asbestos from Asbestos Gaskets. Appl Occup Environ Hyp 6(7>:S8K-59I (1991I. 2. McKinnery. W.N.; Moore. R.W.: Evaluation of Airborne Asbestos Fiber Levels During Removal and Installation of Valve Gas kets and Packing. Amer lnd Hyp Assoc .loum 53(81:531-532 (1992). 3. Spence. S.K.: Rocchi. P.S J.; Exposure to Asbestos Fibers During Gasket Removal. Ann Occup Hyp 40(5):5R3-58K (1996). 4. Liukonen. L-R.; Still. K.R.: Beckett. R.R.: Asbestos Exposure front Gasket Operations. Industrial Hygiene Branch. Naval Regional Medical Center. Bremerton. WA (May. 1978). 5. National Institute for Occupational Safety and Health (NK)SH): Asbestos and Other Fibers by PCM--Method 74(10. NIOSII Manual of Analytical Methods--4th Edition. DHHS (NJOSH) 1'ubl. No, 94. 113. NIOSH. Cincinnati. OH (1994). 6. Environmental Protection Agency (EPA); Asbestos-Containing Materials in Schools: Interim Transmission Electron Microscopy Methods.Title 40. Code of Federal Regulations. Part 76). Subpan E. Appendix A (1987). 7. RJ. Lee Group. Inc.: Personal SEM. v. 3.11. R.J. Ixc Group. Mon roeville, PA (1996). 8. Occupational Safety and Health Administration (OSHA I: Asbestos. Construction Standard. Title 29. Code of Federal Regulations, pan 1926.1101: General Industry Standard. Title 29. Code of I ctleral Regulations. Pan 1910.1001 (1999).