Document nk2yo2Q47rKXdOM5NmG77bJE2

Applied Oocupctioiut aad Emrtrocimen?*} Hytirne Womcl7(l >.35-62.2002 Copyright 2002 Applied Industrial Hycienc IW7-322X/Q2 3)1.00 4.00 Fiber Release During the Removal of Asbestos-Containing Gaskets: A Work Practice Simulation William .-William B. Egdand, Richard L. Hatfield, andLarry R. Newton Materials Analytical Services, lnc,f Suwantt, Georgia Work practice studies wet conducted involving the These from mam 'ti^CeirmEne potential exposure ImU to Individuals who hare worked with these types;ofmaterials In the pest end may still woHc with these. prodacts today, the work practices wot conducted inside tn exposure diaractfrfaatjoa laboratory (ECL) and were performed by iagrdirysotile-cf^^ to85^) sheet f^kttslnmi a number of used steam flanges. Ahhonw asbestos levels were measured by phase contrast ndcroscopy (PCM) and transmission electron mtereecppy (TEM) for the person nel and area air samples collected during the study. These workplace simulations showed substantial asbestos fiber re lease using scraping, baud wire brushing, and power wire brushingtechniques during thegasket removal process.The S micrometers when measured by fC&L These results cootratted with tiit few reported remits in pie published filerature where lower airborne asbestos levels were reported. In these studies the airborne asbestos liber levels measured la many of the samples exceeded all current and histori cal Occupational Safely and Health Administration (OSKA) excursion limits (15-30 minutes) and some previous per missible exposure Emits (PEL) based on eight-hour timeweighted average (TWA) standards. Abo, Individuals who performed this type ofwork in the past may bare had expo sures higher than previously tuspectod. The results demon strated that employees who remove dry asbestos-containing gaskets with no localized ventilation should wear a fuH foce work am should be designate* a regulated area. Keywords AsbestOt, Gasket. Removal, Explore the ability to prevent leakage between different types of cou plings,particularlytelevated temperature and pressure.^5 These types of gaskets normally contained 70 percent to 60 percent chrysoliteasbestos by weight, to somecases crocidotiteasbestos was wied for special applications, that is. sealing flanges to add lines. The remaining non-asbestos component ofthe gasket was usually constructed of synthetic rubber suueris! that consisted ofeither neoprene, styrene butadiene rubber (SBR), or a nitrile polymer.**"4* f . : . ucts ^4tit other twnmineal fibers in 1996s. This coincided with the Environmental Protection Agency's (ERA) ([989ban on the manufacture, importation, pro cessing, and distribution ofthese types ofproducts.** However, the United Stales Fifth QreuH Court of Appeals vacated most offoe asbestos bw and Phase Out Rule and remandedIt back to EPAfn October |99l. Although foe courtvacated andremanded most of the rule,1It left intact the ponton that regulated asbestos products that were not being manufactured, produced, or im ported when foe rule was published in December 1989. Since sbestbsfcontaining sheet gaskets were still bring imported into this country, they were exemjtf^ can still be manufactured, purchased,andused in theUnited States. product* whenbedenionstmcd that foe application ofasbestoscontaining gujeets bad foe potential to release respirable asbestos fibers ^cll above ctirrcnt^SHA sum^aids| Fowlerrec ommended foat these products should not be used in today's Industry and that only non-asbestos gaskets should be used in their place.** An issue that faces many former industrial workers is foe past use of these types of gaskets. Workers were not informed in most cases foal foe products they were using had foe poten tial to release rievnted levels of respirable asbestos fibers. Legal issues concerning past exposures pose this basic question; Did Asbestos-containing sheet gaskets have been used In almost contribute to foeir asbestos exposure history? Industrial hygien every type of industry for the last fid yean. These puttee, had ists iriust rely on a retrospective exposure assessment to make 56 W.E.LONGOETAL. this determination.^ In this approach the individual's work his tory is compared to the results of retrospective exposure assess ment studies that replicate their work activities. A review of the peer-reviewed literature found very few pub lished studies involving exposure assessments during the dry removal of asbestos sheet gaskets from flanges.*2-91 The stud ies of Cheng, Millette, and McKineiy were somewhat limited in the information reported. Millette used only a small num ber of flanges, Cheng's work did not verify that all the gaskets contained asbestos. Additionally, there was only limited infor mation provided in all three studies concerning the size and the history of the flanges used or the length of time required for the gasket removal process. . The mostcomprehensive studyto date was by Spence etal/101 However, the authors used wettingto control the airbornerelease of asbestos fibers. This limited the study's value for any retro spective exposure assessment since dust control methods were not used in the workplace historically. In contrast to the previous studies, the goal of these new work practice studies was to estimate a worker's asbestos fiber exposure during the removal of asbestos-containing sheet gas kets using common removal techniques such as scraping, hand wire brushing, and power wire brushing. The studies were con ducted on a large population of steam line flanges and valve assemblies. The compilation of several studies discussed in this articleallows a more accurate retrospective exposure assessment for individuals who worked with these products in the past and the assessment of potential exposure to workers who may be removing asbestos-containing gaskets today using these same work practices. High-intensity lighting and videotaping techniques were used inside an exposure characterization laboratory (ECL) during the work practice studies to visually document the pathway of ex posure during the gasket removal process and to help determine what activities produce the airborne asbestos dust. The methods and procedures described in this report can be applied to assessing past and present industrial hygiene expo sures to other dusts, fumes, and fibers besides asbestos. The videotaping of dust, fume, and fiber exposures under high- intensity light can be used as a training tool in visualizing the importance and effectiveness of engineering and administrative controls and respiratory protection. MATERIALS AND METHODS A number of valve and flange assemblies were collected in 1994 from a paper mill powerhouse in Oregon and stored under ambient conditions in a protective environment until their use in these studies. A sampling of these flange and valve assemblies was partially opened to confirm the presence of asbestos in the sheet gaskets using polarized light microscopy (PLM) prior to the work practice study/1-1) Any opened flanges were reassem bled and the outside surfaces ofall the flanges were cleaned, sand blasted, and repainted. Interviews with former machinists and pipefitters determined that the most common techniques for re moving gasketmaterial tightly adhered to the flange surface were hand scraping, band wire brushing, and/orelectric wire brushing. The work practice simulations were conducted inside an ex posure characterization laboratory (ECL) that was constructed as a containment area to prevent the release of asbestos to the outside environment. The dimensions of this containment area were 6,0 m (length) x45m (width) x 2.4 m (height). The ECL also contained two viewing ports for videotaping purposes and had a decontamination area for contaminated clothing disposal, an air lock for sample removal, and showers to further control fugitive emissions. Fresh air was produced by a high efficiency particulate ab solute (HEPA) filtered negative air machine manufactured by Aramsco (model #55011) and pulled through the ECL at a venti lation rate of5.7 cubic meters per minute. This unit was operated at an air exchange rate of five times per hour (ACH) during the work practice studies. The air in the chamber was flushed be tween studies by increasing tire fresh air ventilation to 28.3 cubic meters per minute for a minimum of 24 hours. At the end of the first scraping and hand wire brushing study (Study 1), the ECL was completely decontaminated by HEPA vacuuming all dust and debris and then wet wiping. Also, all inside surfaces were repainted after the decontamination procedure. High-intensity lighting (700-1000 watts) was used inside the chamber during videotaping of the work practice to document dust generated by various tasks and to observe pathways of ex posure to respirable dust In previous studies the use of highintensity lighting was found to be an effective tool to display respirable airborne dustreleased from asbestos-containing prod ucts during work activities/12'131 The authors performed these studies wearing normal work clothes over disposable protective suits and were equipped with supplied air respiratory protection with HEPA escape filters. Personal and area air samples were collected during the studies using nonconductive three-piece cassettes. The cas settes contained mixed cellulose ester (MCE) filters that were 25 millimeters in diameter and had a 0.8 micrometer pore size. These filters rested on a MCE backing filter (5.0 micrometer pores). The personal and area air sampling pumps were cali brated before and after the completion of each study against a DryCal primary flow meter to air flow rates of two and ten liters perminute, respectively. High-volume air-sampling pumps (Dawson 110 volt) were used for collecting area air samples dur ing the studies. Four area samples were located in four equidis tant quadrants at a distance of 2.1 meters from a work bench placed in the center of the ECL. The area sample cassettes were placed on sampling stands at a height of 1.5 meters. The four calibrated high-volume air sampling pumps were placed outside the chamber and each pump was connected to an area air cassette by Tygon tubing passing through the wall of the ECL. The two investigators performing the studies were each fitted with two calibrated personal GilAir air sampling pumps with the air-sampling cassettes attached to each shoulder and within their FIBER RELEASE DURING REMOVAL OF ASBESTOS 57 breathing zones. Background area samples were collected inside and outside the ECL before each study. The air samples were collected in general accordance with the NIOSH 7400 method entitled, "Asbestos and Other Fibers by PCM"(,4) Two air sam pling cassettes were opened for 30 seconds inside the ECL to serve as personal field blanks at the end of each study. Surface morphology of new and used gasket material was examined using a Hitachi S-800 field emission scanning electron microscope (SEM). Photomicrographs were taken of the gasket surfaces to document the degree of gasket degradation and the relative amount of asbestos fibers present on the surface. Study 1--Scraping and Hand Wire Brushing of Small Flange Assemblies Seven small flange assemblies were used in this study. The gaskets had outside diameters of approximately 69 mm and working widths ofapproximately 19 mm. Gaskets were removed from one flange on the first four valve assemblies and then from two flanges on each side ofthe remaining three valve assemblies for a total often gaskets; The flange assemblies were first opened and then the, gaskets were scraped using a stiff, four-inch-wide putty; IknifelAny residual gasket material that could not be re moved from the flange faces by scraping was removed by hand wire brushipg. Some of the gaskets required repetitive scraping and wire brushing to remove the gasket and to polish the flange face. The sheet gaskets were removed sequentially from each of the 10 flanges. One ofthe investigators in the ECL simulated the worker who did all of the gasket removal while the other acted as a "helper." The helper changed the area and personal air sample cassettes periodically throughout the study. Each gasket was collected and retained for analysis to determine both asbestos content and matrix identification after removal. The investigators werc in the ECL for. 194 minutes. All air sample cassettes in the ECL were exchanged every 15 to 30 minutes. A total of seven sets of air samples were collected. Study 2--Scraping and Hand Wire Brushing of Large Flange Assernblies Four large flange assemblies were used for this study. The outside diameter ofthese gaskets varied from 125 mm to 200 mm and the gaskets were 19 mm to 25 mm wide. The gaskets were removed and collected from the fprir fiinges^s described in Study 1. The investigators were in the ECL for 413 tpinutes. All air.sample cassettes in the ECL were exchanged every 15 to, 30'miriutes. A total of five sets of air samples were taken during" this work practice simulation. Study 3--Power Wire Brushing of Large Flange Assembly * An electric wire brush (Skil electric drill 0.3 Hp with a Columbian 10.2 cm crimped wire wheel) was used during this study to remove gasket residue that could not be removed during the scraping and hand wire brushing of the first flange assembly used in Study 2. The electric wire brush was also used to polish the flange face surfaces. This study was conducted one day after Study 2. The ECL was not decontaminated between the stud ies. The two flange surfaces were electric wire brushed until the gasket residue was visibly removed. As previously described in Study 1, the two investigators were in the ECL performing the study. One person did the removal work while the other assisted as tire helper. Theresidual gasket material was notretained since the bulk of the material was collected in Study 2. The investigators were in the ECL for 42 minutes. The air cassettes in the ECL were exchanged every ?10 riiihutes.; A total of four sets of air samples were taken during the electric wire brushing activity. All air filters collected were analyzed by PGM in general ac cordance with the NIOSH 7400 method using the "A" counting rules. Additionally, all air samples were prepared for ex amination using the indirect preparation method/15* The indirect TEM preparation method was chosen because filter overloading rendered the samples unsuitable for direct preparation despite frequent changing of the air sample cassettes. Also, the indirect TEM preparation method enabled data comparisons to other published and unpublished studies previously performed that also used the indirect TEM method/16-18* The TEM air sam ples were then analyzed by a modified EPA Level II protocol/19* Cloth swatches from the work clothing worn by the investiga tors during the studies were analyzed by the recommended EPA method.020* Surface dust samples were collected from the work table after each gasket removal study and analyzed according to the ASTM protocol/13* Background samples from the clothing and the work table surface were also collected before each study was started. The removed gaskets were analyzed for asbestos type and content by the standard PLM method/11* RESULTS . It was determined by PLM that the gaskets removed in these studies contained 65 percent to 85 percent chiysotile asbestos (Ihble I). Thble II and Tfcble HI, respectively, illustrate the PCM and TEM results for Study 1. The worker in Study 1 had a peak exposure level of 10.4 fibers per cubic centimeter (f/cc) and an 8-hour TWA exposure of 1.5 free. The area air samples were voided after the completion of Study 1 when it was determined that the air-sampling lines into the ECL were obstructed. The Studies Study 1 Study 2 Study 3 TABLE I PLM analysis of removed gaskets Number of gaskets analyzed 10 4 1 Asbestos type Chrysotile Chrysotile Chrysotile Concentration of asbestos in volume percent 65-80% 75-85% 85% 58 W. E LONGO ET AL. . TABLE II . Study 1--Scraping and hand wire brushing: small flanges. PCM airborne exposure levels (fibers greater than 5 micrometers) Sample type No. of air Sample time weighed 8-hrTWA samples analyzed Range (ffcc) average (ffcc) (f/cc) Background Worker Assistant Area samplesA 4 14 14 36 0.0 1.5-10.1 1.2-4.2 -- 0.0 3.7 2.4 --. N/A 1.5 1.0 -- Total air-sampling time = 194 minutes. *Tbc air-sampling lines into the ECL were obstructed, voiding the area air samples in this study. results for S.tudy 2 are shown in Tables E^fihd^'pie worker in this study had a peak exposure level of'24,0 free and an S^ur-EWA^fa# ffcc. IhbieVVl and ^Table V3I:list results for Shidy S. tThe peak exposure level found While power wire brushing was ffcc and the calculated 8-hour TWA was 23 fydc.-^The results for the surface dust samples taken from the work table and the fabric samples are shown in Tkble VHL All PCM and TEM data in the tables are expressed for compar ison purposes as fibers per cubic centimeter (f/cc) greater than 5.0 micrometers in length. DISCUSSION The asbestos concentrations measured in these studies were higher on average than other previously published studies for similar work practices.*7-91 It is believed that the higher concen trations found in these studies were due largely to the gaskets adhering more tightly to the flanges. Tightly adhered gaskets require higher,energy for removal. As described bv Fowler, the friability oftheproductis always relative totheenergv applied,*61 Only two of the fourteen gaskets removed could have been de scribed as easily detached. The other twelve required extensive effort on one or both of the flange faces. Machinists, pipefit ters, steamfitters, and others commonly described sheet gaskets as tightly adhering to flange surfaces and requiring substantial work to remove the gasket material. Unfortunately, the various conditions and the amount of adhesion of the gaskets in the pre viously published studies were not reported.*7-91 The adhesion of gasket materials generally has been related to its lengthen TABLEm Study 1--Scraping and hand wire brushing: small flanges. TEM airborne exposure levels (asbestos fibers greater than 5 micrometers) Sample type Background Worker Assistant No. of air samples analyzed 4 . 14 14 Total air-sampling time = 194 minutes. Range (fibers/cc) 0.0 29.9-144.2 2.2-29.5 service and the conditions of service such as temperature and pressure. The high temperature steam flanges used in this study were from a operated for a number of years. The last freamfitter Who'maintained the steam system in dicated that gasket replacement was rare due to infrequent plant downtime and few leaks. Gaskets that could be easily removed would not be expected to produce airborne levels comparable to what was found in these studies. None of the previous studies df^rrihftd the level Of difficulty of femovine the gaskets from the flange surfaces. ` The air samples collected were analyzed by both PCM and TEM during the gasket removal activities in these studies. The two basic types of sample preparation for TEM air analysis are the direct and indirect methods.*15,16,21-231 Some scientists have suggested that the indirect sample preparation method, particu larly the souication step, causes large complex asbestos struc tures such as fiber bundles and . clusters to break up and bias fiberfcouhts io higherconcentrations.*24,231 However, studies per formed by the EPA and others .have shown that this criticism is not.Yaiid and thatflic indirect technique is an acceptable method to analyze overloaded air samples.*26-281 The overloading of other particulates on an air filter will ob scure fibers that are collected. This .condition can lead to the .undefcounting of asbestos fibers if a direct preparation method is used. Controlling the particulate loading on a filter can be dif ficult when the disturbance ofmaterials generates large amounts of both fibrous and nonfibrous airborne particulates. The gen eral approach to reduce or eliminate overloading conditions is to alter flow rates and sampling times. However, particulate load ing can be controlled by using the indirect preparation method without compromising sampling times. The overloading prob lem can also affect the direct examination of air filter Samples by PCM (NIOSH7400 method). This was noted in Study 1. The asbestos air concentrations measured by PCM in Study 1 decreased as the study progressed. This would not be consistent with the continued activities that took place inside the ECL dur ing the study. This effect was due to particulate overloading on the However, according to the TEM data from Study 1, the asbestos fiber concentrations tended to increase as the work progressed. The sampling times forStudies 2 and 3 were reduced in an effort to minimize overloading on the PCM air samples. FIBER RELEASE DURING REMOVAL OF ASBESTOS 59 TABLE IV Study 2--Scraping and hand wire brushing: large flanges. PCM airborne exposure levels (fibers greater than 5 micrometers) Sample type No. of air samples analyzed Range (free) Sample time-weighted 8-hrTWA average (f/cc) (f/cc) Background Worker Assistant Area samples'* 4 10 10 24 0.0 9.3-24.0 5.2-15.7 2.1-8.4 Tbtal air-sampling time =113 minutes. ATWA not calculated for area or "bystander" samples. 0.0 15.3 8.8 -- N/A 3.6 2.0 -- However, any further reduction in the sampling time would have had an impacton the work actiyities. Therefore, the air-sampling times were not decreased any further. The current OSHA asbestos exposure standards are based on the NIOSH 7400 method. This method measures only fibers longer than 5 micrometers in length and greater than 0.25 micrometers in width. However, these fiber dimensions were not implemented by OSHA with regard to health issues, The minimum'dimensions were implemented solely due to the fiber resolution limitations of the PCM technique.*29* OSHA meters.*32* This average diameter is approximately five times below the resolution of a phase contrast microscope. Therefore, single chrysotile fibers cannot be seen orcounted using die PCM method, irrespective of their lengths. Because of flic inherent errors in PCM analysis, it was suggested by the director of the HealthEffects Institute forAsbestos Research that OSHA should consider changing to TEM air sample analyses for occupational workplace compliance to adequately protectworkers' health,*33* An SEM examination of the sheet gaskets was performed to better tmderstand the relationship between the physical activity has long recognized that PCM is not fiber-specific or able to resolve fibers that are less than 0.25 micrometers in width. The TEM analysis performed in these studies augmented the PCM of removal and the measured asbestos air levels found in this study. Generally, sheet gaskets are comprised of approximately 70 percent chrysotile asbestos bundles in a synthetic rubber raa- measurements by obtaining more complete and accurate mcasurements of flic airborne asbestos concentrations. A comparison of the air data collected from the PCM and trix. The SEM micrograph (Figure 1) shows large bundles of asbestos protfudihg from the matrix of new sheet gasket material. Any minimal disturbance or abrasion of these bundles TEM analyses showed fiber concentrations approximately 30 times greater in the TEM analysis. The differences between TEM and PCM measurements have been recognized by others can release asbestos fibers into the air. Another problem with asbestos gaskets is that the synthetic rubber matrix begins to dctenorate after installation. In most cases installed sheet gaskets and are primarily due to the resolution limitations of the opti- are subjected to high temperature and pressure that will increase cal microscope.*30,3 ** The deficiencies' bf CM'&ieasureraents the rate ofthermal decomposition ofthe rubber matrix. This pro- are especially acute when products such as sheet gasket materials that contain high percentages of chrysotile fibers are the source of the airborne fibers. It has been shown that free res- duces cross-linking ofthe polymer molecules. The cross-linking process increases the gasket material's friability by causing the rubber matrix to degrade and become brittle.*34* pirable chrysotile fibers are released wfien asbestos-containing A comparison of the surface of a new gasket (Figure 1) to products are abraded in some manner*6* that of a used gasket removed from one of the flanges in Study 2 Work by the EPA demonstrated that single chrysotile fibers (Figure 2) demonstrates how the rubber matrix material is dehavc an average diameter of between 0.03 and 0.07 inicro- '. graded. This degradation provides more opportunity for the re TABLE V Scraping and hand brushing: large flanges. TEM airborne exposure levels (asbestos fibers greater than 5 micrometers) Sample type No. of air samples analyzed Range (fibers/cc) Background Worker Assistant Area samples 4 14 14 ' 24 0.0 199.6-842.7 13.6-101.0 3.3-108.8 lease of asbestos fibers during the removal process. The fiber concentrations measured in Study 2 were higberthaii those mea sured in Study 1 even tiiough'mbre gaskets were removed in the first study. Factors believed to lead to these results were as follows: (1) Tie total gasket surface area removed in Study 2 was much larger than in Study 1, (2) The gaskets in Study 2 were observed to be more friable and more deteriorated, and (3) All'the gaskets in Study 2 tore apart and remained adhered or attached to both of the flange faces when the flanges were opened. An electricpowered drill equipped with a wirebrush was used to remove some residual gasket material from two flange feces Total air-sampling time =113 minutes. in Study 3. The resulting exposures during the work activities 60 W.E. LONGO ET AL TABLE VI Study 3--Power wire brushing. PCM airborne exposure levels (fibers greater than 5 micrometers) Sample type No. of air samples analyzed Range (f/cc) Sample time-weighted average (f/cc) Background Worker Assistant . Area samples* 4 0.09-0.12 7 14.9-31.0 8 12.8-21.2 16 7.6-15.7 0.11 21.8 15.9 -- Tbtal air-sampling time -- 42 minutes. ATWA not calculated for area or ``bystander" samples. 8-hrTWA (f/cc) N/A 2.3 2.0 -- were higher even though Jthe ^idual;Wket;jrnaterial was far less than the gasket materials removed$ti Study 1 tad Study 2. It was observed in Study 3 thdt the mechanical action gener ated from the power wire brush torc loose more asbestos fibers and propelled them greater distances into the air. This observa tion supported the higher asbestos air concentrations of the area samples measured in Study 3 compared to those measured in Study Z The results from the surface dust and fabric samples (Table VBI) showed that the surface asbestos levels measured can be classified as "highly contaminated"<ahd pose additional exposure problems to the woriair throughout the workday. Addi tional asbestos exposure can occur to both the worker and other family members if the clothes are worn away from the job dr taken home.?55 CONCLUSIONS AND RECOMMENDATIONS These studies, as well as the other studies previously dis cussed, demonstrate that there can be widevariability in airborne asbestos fiber levels generated during the removal of asbestoscontaining gaskets from flanges. The variability of fiber levels . released is mostlikely dependent on the condition-offhc asbestos gasket, the sizfe?df;tHd'g^ket surface area ^^ the ciethod of re- tnoVm. The condition to which a gasket is subjected determines the degree of adhesion of the gasket to the flange surface and the friability of the gasket This impacts the amount of energy required to remove the gasket and release asbestos fibers. The determiningfactors that seem to affect the condition ofthe gasket TABLE VII Study 3--Power wire brushing. TEM airborne exposure levels (asbestos fibers greater than 5 micrometers) Sample type No. of air samples analyzed Range-fibers/cc are: length of service, temperature and pressure conditions, and composition of the gasket matrix. Our data show that dry removal methods typically used by machinists and pipefitters (past and present) result in significant airborne asbestos fiber exposures. For retrospective asbestos ex posure assessments, the exposures measured by PCM in Studies 1,2, arid 3 exceed allhistorical OSHAexcursion limits and soriie previous permissible Exposure limits (PEL) based on an eighthour TWA. The exposures also far exceed current OSHA levels. Therefore, former machinists and pipefitters that performed this type ofwork as part oftheirjob activities would have had signifi cant airborne asbestos exposures when removing tightly adhered gaskets on flange surfaces. Under normal lighting, airborne dust is invisible eventhough the asbestos levels measured axe above OSHA excursion limits. Therefore, an individual removing asbestos-containing gaskets will be unaware of any airborne exposure problems under nnrmal working conditions. High-intensity lighting (Tyndall Effect) was used by the investigators in these studies to observe expo sure mechanisms for workers performing normal work activities. The Tyndall Effect documented fiber release mechanisms and the pathways of exposure to the individuals removing the gas kets. Tyndall lighting is an alternative technique that industrial hygienists can use to check potential airborne dust emissions in the workplace. The Tyndall lighting technique can visually demonstrate to workers and employers if there is a need for air sampling, additional ventilation, respiratory protection, and/or special work practices. There are still significant numbers of asbestos gaskets cur rently being used in the United States. OSHA classifies the . TABLE Vm TEM fabric and surface dust contamination levels Studies Fabric-fibcrs/cm2 Surface dust-fibers/cm2 Background Worker Assistant Area samples 4 7 8 16 Total air-sampling time = 42 minutes. 0.0-0.2 877.1-1636.1 60.4-364.4 56.9-801.9 Study 1 Study 2 Study 3 981 thousand 3.2 million 193 million 83 million 27.8 million 57.4 million All background control samples and field blanks analyzed were be low the analytical detection limit FIBER RELEASE DURING REMOVAL OF ASBESTOS 61 FIGURE 1 Scanning electron micrograph of the surface of a new asbestos-containing gasket Both the chrysotfle fibers and polymer matrix are visible. Magnification lOOOx. FIGURE 2 Scanning electron micrograph of the surface of a used asbestos-containing gasket The majority of the material present is only chrysotile asbestos. Magnification lOOOx. removal ofasbestos-containing gaskets as Class II work of short duration.*36* This specification by OSHA only addresses a sin gle gasket removal project However, interviews with pipefljters and machinists indicate that only removing one gasket at a time Was not a typical Occurrence. Under current OSHA reg ulations. the removal of asbestos-containing gaskets requires the use of a glove bag and Wetting methods to contain the re lease of asbestos fibers into the workplace. Unfortunately, the glove bag and wetting methods are not always practical in an actual workplace due to production and maintenance sched ule pressures and the difficulty, in wetting a rubber based gasket Theresults ofthese studies indicate thatemployers need to de termine ifasbestos-containing gaskets are present in their equip ment The employer must immediately comply with OSHA's Class II provisions by implementing a safe operating proce dure that includes employee training, assessment/monitoring, containment, and good work practices. The following actions are recommended if asbestos-containing gaskets are removed without a glove bag and wetting: (DA negative pressure ;pnclosure should be used. (2) The enclosure should have a HEFA' filtering/air blower system. O') A HEPA vacuum cleaner and Wfetting agents should be used, and (4) The worker should wear arespirator appropriate for the airborne asbestos concentrations generated by the activities. The data presented here demonstrate that the work surfaces in these studies as well as the clothing worn by the investigators were highly contaminated with'asbestos fibers. An asbestoscontaminated workplace can lead to additional asbestos expo sures. The disturbance of the dust around the work area by other work activities and housekeeping activities will re-entrain as bestos fibers into the air.^ The wearing, changing, and washing ofthe contaminated clothing can also lead to asbestos exposures for both a worker and family members. REFERENCES 1. Bowler, WJ.: Hows and Whys ofPacking of Gaskets, Paper Trade Journal. Oct (1965). 2. Oarlock Industrial Products Catalog. (1969). 3. Klinger Compressed Gasket Materials Catalog. (1983). 4. Crane Packing Company, Catalog 60-R-2. (1954). 5. Environmental Protection Agency (EPA): 40 CFR Part 763, As bestos: Manufacture, Importation, Processing and Distribution in Commerce Prohibitions; Final Rule. 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