Document LKEmYX54ypOxBBp4B9RdV6GG7

pcrgamon CafArnmjMcC1mIf.MMrItr~xtVuhJ. <0. N >, ffK. yU^ tu:rWn6) hkiitM kjr Brno Soon; Liod.xfyria-mtadtfina CjuruoaJ-nftlxuon 0003--4878(95)00098--* j EXPOSURE to asbestos fibres during gasket REMOVAL S. K. Spcncc*t and P. S. J. RocchiJ aRCO Chemical Lid. Rotterdam. The Netherlands; and !Shell Netherlands Refinery. Hoogvlict. ' The Netherlands (Xecrivnd in finalfarm 24 August 1995) ^kstrect--In the chemical industry, asbestos gaskets have bocn used extensively to prevent leakage between solid surfaces. The purpose of this study wax to assess the potential personal exposure *u ixbestos fibres during gasket icmoval and thus to determine wJut is reasonably required m terms of protective regime and work method. Two groups were studied: group A. whn only removed gaskets if they could be removed easily and without breaking; and group R, who removed gaskets which *ere left by the first group. For both groups, the gasket was first made wet before removal. The jamples were analysed thing phase-contrast microscopy and transmission electron microscopy. The average exposure to fib/cs for group A. averaged over the work period, was 0.04-0.242 fibres ml"' determined by phase-contrast microscopy. On further analysis with transmission electron microscopy it wu found that only four of the 11 samples contained asbestos In very low concentration* and that most of the fibres, which were identified using phase-contrast microscopy, probably originated from the glass fibre lagging around the pipes. For group B the average fibre concentration, averaged over the work period, as determined by phase-contrast microscopy, ranged between below the detection limit and 0.02 fibres ml-1. The subsequent transmission electron nucrosccpy analysis shows that the exposure to asbestos fibres ranged between below the limit of detection to 0.004 fibres tnl"'. This study shows that the exposure to asbestos fibres during gasket removal actvities-wj well within the -h average exposure limit of 0J fibres mi**1. Copyright C 1996 British Occupational Hygiene Society. INTRODUCTION In ihe chemical industry, asbestos gaskets have been used extensively to prevent leakage between solid surfaces. With time, the effectiveness of the seal may become compromised and therefore they are replaced periodically. Normally they arc replaced on an ad hoc basis. However, during a major maintenance overhaul of a chemical facility, called a 'turnaround*, hundreds or thousands of gaskets may have to be replaced over a period of a few days by maintenance teams. Typically, these activities are carried out by maintenance personnel from contracting companies who go from turnaround to turnaround performing similar jobs. Therefore, if there is a potential hazard through exposure to asbestos fibres, then it is these individuals who arr at most risk. . Nowadays, the use of asbestos is limited by restrictions which arc legislated in both European and North American countries. These restrictions arc, naturally, due to the potential of asbestos to cause cancer. Eventually, it is expected that all existing gaskets will be replaced by non-asbestos substitutes. However, at present many chemical plants still use asbestos gaskets in their facilities and it will 'TCurrcm jvJdjcsv 32 Uull.ic Tcrruce. Ancdccn Al *t_Q. U K* k PLAINTIFF'S 2 EXHIBIT 1 554 . S. K. Spence xnd P. S. J. Rocchi j probably be years before all or them have been substituted with non-asbest^ \ alternatives. Additionally, in developing countries, asbestos, is still permitted aU(j continues to be used for many applications, including gaskets. Therefore, it i* important to determine whether there is a health risk associated with the rcraovy of gaskets. . The three major types of gaskets used in the chemical industry arc sheet or plate gaskets, spiral wound gaskets and metal jacketed gaskets. For the metal jacketed .type, the gaskets are completely encapsulated by metal as the name suggests. These were not considered in this study. Spiral wound gasketiconsist of a crysotilc asbestos I | filler material compressed between stainless steel spiral windings. They typically fall ' out as soon as the pressure on the seating surfaces has been released. Plate gaskets ' arc compressed sheeps of crysotilc asbestos bound together with nitryl or neoprene. When plate gaskets have been sitting in an installation for a long period under pressure and exposed to chemical agents, they may become damaged and fixed. In i order to remove them, and leave a clean surface on which to put a new gasket. ; c. scraping may be required. This increases the chance of asbestos fibres becoming airborne and maintenance workers exposed. There arc not many studies in the literature which document the exposure to Jiirbome a$j$gtos during gasket removal McKinnery and Moore (1992) looked at fbolh pf gaskets and packing material. For gaskets, the average monitorinf period during removal for five samples was 31 min. On analysis using phase-contrast microscopy (:PCM), the fibre concentration ranged between-0.049 and 0.44 fibres mlj1. Furth|panalysts was done using transmission electron microscopy (TEM). The concentm^bns found using TEM were higher, (0.86-18.55 structures ml"1), however, for |||is study, the analysis method did not allow a direct comparison between PChJ||bd THEM. Another study done by Millettc and Mount (1993) looked at removal nfilfy packing material for three samples monitored over periods ranging between 25 arp 33 min. They found fibre concentrations between 0.2 and 1.0 fibres inl~ * using P.Mm analysis. On analysing using TEM and converting to the PCM equivalent, fibre concentration was higher, ranging from 1.5 to 2.6 fibres ml-1. These two studies by McKinnery and Moor<pl992) and Millettc and Mount (1993) both used a . (Zheng pnd MctJcrroou (1991) looked at the difference between wet and dry removal of asbestos gaskets in a real work situation. The analysis method used was limited ip PCM. They found that the average fibre concentration of four samples using dry removal was 0.11-0.33 fibres ml"'1. The sampling duration ranged between 19 and 55 min. For wet removal, fibre concentrations for two samples were below 0.06 fibres ml"'1. The sampling duration for the first and second sample was 15 and 30 min. respectively. The purpose of this study was to assess the potential exposure to asbestos fibres during a real work situation and to determine what is reasonably required in terms of protective regime and work method. This second point was important in the light of legislation in The Netherlands covering asbestos activities (Ministry of Social and Work Affairs, 1993) which was valid at the time of the study. In The Netherlands, at the time of this study, all asbestos activities were classified under one general ruic which describes the protective measures to be taken during these activities. Exposure to ubciua durio| psket removal 335 (1) Workers must wear personal protective equipment (HEPA. filter full-race mask respiratory protection, hooded coveralls, gloves and boots). (2) The area must be cordoned off during removal activics. (3) There must be a personal decontamination procedure in place. (4) Individuals employed must be trained in the hazards of asbestos. (5) Area monitoring must take place at the end of the job in order to declare the area asbestos-free. (5)'Asbestos removal activities must be reported beforehand to the authoridcs. For gasket and packing removal, step (5) is hot required and step (6) can be done ,,nce a year to a cover gasket removal for the whole year. This regime, when applied gasket removal, is logistically challenging, conservative and expensive given the [ight time schedule of a `turnaround', and the number of concurrent activities which ^rc canted out in the same location. A compromise position was adopted whereby tv/o work methods were applied for the removal of asbestos gaskets. MF.THOO Group A Group A was the `first pass* group. In the course of the maintenance activity, when a gasket was to be removed, the individual wore a P3 disposable half mask, wet the gasket with a wetting agent, and then an attempt was made to remove it with little effort and with only a putty knife. If the gasket came out easily, it was placed in a plastic bag for special disposal. If the gasket proved difficult to remove or broke In the process, it was left for group B. Employees from group A were working in sections of the plant where it was though1 that asbestos gaskets would be encountered. However, it should be noted that there was no way of knowing for sure whether or not asbestos or substitutes would be encountered during the work activities. All the gaskets which were removed were saved for bulk analysis. Group B The gaskets which were left out during the first phase were removed by a team of trained individuals during the evening when there were limited persdnne! pn.site..For this group, the area was Isolated, and a full personnel protective regime of P3 power pack respiratory protection (Protection Factor*200), hooded overalls, boms and gloves was used Full decontamination procedures were followed at the end of the shift. Again, the gaskets were saved for bulk analysis. Personal exposure monitoring was performed for both groups according to NVN 2939 (1987). After sampling, the filters were divided into two. The firs: half was analysed using phase-contrast microscopy (PCM) according to NVN 2939 (1987). The second half of the filter was analysed using transmission electron microscopy (TEM) according to NTOSH 7402 (19H9)..TEM distinguishes between asbestos and non-asbestos fibres whereas PCM docs not. It was felt that the additional analysis using TF.M was necessary because other airborne fibres would likely be present since piping insulation (mainly fibre glass) was also removed in the same operation as gasket removal. 586 S. K_ Spcncc tad P. S- J. Roccfai Owing to the expense associated with the TEM analysis, it was dedd^ y beforehand that those samples which had a concentration of less than 0.015 fibre* ml-1 as determined by PCM, would not be analysed by TEM, (This figure selected since this represents the total exemption value according, to Dutch legislation.) This means that when an area measurement is found to have a concentration of less than 0.015 fibres ml" ', the area is considered free of asbestQ; ! I (Ministry of Social and Work Affairs, 1993), . _ .*. ' I1 RESULTS AND DISCUSSION Tabic 1 shows the results for group A. Group A removed between two and 1} gaskets per shift. All gaskets were spiral wound. The average fibre concentration far work method A was 0.042-0J42 fibres ml-'. When converted to exposure averaged over 8 h, it varied between 0.036 and 0.215 fibres ml-1. On further analysis with TEM only four of the 11 samples contained asbestos in very low concentrations. This is not Surprising since on bulk analysis of the gaskets, only five of the gaskets removed by group A contained asbestos. This is unfortunately the possible outcome when a real life situation is chosen rather than a simulated environment. These results are interesting, however, because of the relatively high concentration offibres found by phase-contrast microscopy. These fibres probably came from the piping insulation' which was removed prior to removal of gaskets, llad the TEM analysis not bccn||arricd out, there would have been erroneous over estimation of the airborne ffbestos fibre concentration. * . Tablel||shows the results for the second exposure group. All the gaskets removed by group | were asbestos plate gaskets. The work was intensive and represented a worse-cas^scenario since all the insulation was removed and the flange, or eqmpmcnfipicce was already open. This meant that full shift was spent only removingfficult to remove gaskets. Each worker removed between three and 13 gaskets. Tgi average fibre concentration, as determined by PCM. ranged between below thejaeiecuon limit and 0.02 fibres ml"l. When this is converted to an 8-h Emit, then the v||uc ranges from below the detection limit to 0.005 fibres ml"1. The TEM analysis sjpws that the.exposure to asbestos fibres even in this worst-case scenario still remaps well below both the limit value and the action limit even when looking at the stafi|tics in terms of real time rather than' averaging over 8 h. The only value obtained above the detection limit was 0.0037 asbestos'fibres ml""'. conclusions The results of this study show that personal exposures to asbestos are kept well below the current limit values in Tnc Netherlands. Using a suitable wetting agent provides adequate protection of the employee while limiting the cost and delay posed by unnecessary control measures. Secondly, phase-contrast microscopy, which has traditionally been used for this type of exposure monitoring situation, may not be applicable where there arc mixed fibres present. This method overestimated the asbestos fibre concentration m this study. It is interesting to note the legislative developments regarding asbestos in The Netherlands following the outcome of thi* study. The I.*hour Inspectorate ha* Simple Kc i i j 4 t 7 ( ID II Number ul Illicit 4 1 4 42 15 4 7 Tim* (mini 4)] 427 400 421 410 400 4JO 416 425 4JS 400 TbU I. EipMUfc I# litbonw ibni lot poop A Tout Ibc* cenctMcnfion MMCfCVI V"*-') oca 0 242 0.M1 0 042 0JM2 O.OTJ 0X151 A CM CJ352 OJJJI 0.141 Ajbcnoi llbc* cooczit!!< Mil TEW (Iml-'j Other - uMirjutk Ibid mU|TEM (fM!-*) Nit dtwcuble 012 Km 4<tcubU Knt dctnlnUc Km UiccuUU Km detetuU* C0.0M00\41 J007 Not Ucwcliblc Net dekeubk OjWJ ' 0.050 0 0202 00074 0 0251 0.02J 0.0157 0.0144 0.0151 O.OJ2 0.02M ComKent! On* uWUM, inc aowotUttni, both ipual wound Two isbotoi U|bHy tui|cd nUtlfil, pkl wound Non-ncbwk*. iplcil Wound Nou-mIkcioi. tflrnl wound Nua-(b<(!t>, 14X1*1 wound ' Non-ubntu, tfuril W**d Nou-etboUi, pic*l would Two kib<44M, ihm lon-itu|loi, *1 spied wound Kon-utxilM, i(iii*I wnwud On ubuto*, Uhm Woi-urbcrtoi, l H>l<*l wound NoaOibndat, tplcil would 588 . S. K_ Spence and P. S. J. Rocchi Table 2. Exposure to airborne fibres for group B Sample No. Number of gaskets ToUl fibre concentration Time \mng PCM (min)'. (f tnl" ') Asbestos fibre Other concentration inorganic fibres using TEM using TEM (fml-'j (f mi"') 1 2 3 -4 5 C 7 8 9 10 2 Ml 0.018 Not detectable 0.0144 2 Ml 0.02 3 71 Not detectable 3 71 0.02S 3 156 0.005 9 156 Not detectable 5 69 0.014 5 69 Not detectable 3 M7 Noe detecsbie 6 Ml 0.005 Comments All asbestos, plate typj AH asbestos, plate type All asbestos, plate type All asbestos, plate type Ail asbestos, plate type All asbestos, plate type All asbestos, plate type AU asbestos, pbte type All asbestos, plate type Alt asbestos, plate type Blade area indicates that the sample wax not analysed by TEM. recently published new draft guidelines which apply to removing asbestos gaskets. These allow, under certain conditions, Tor `Woric Method A' to be used for gasket removal activities (Ministry of Social and Work Affairs, 1994). For the employee, adequate protection and case of compliance is assured while for the employer, the cost and complicated logistics associated with `Work Method B* are avoided. This study shows another example of how it is possible*for industry and legislative bodies to pull together on health and safety issues to study situations for mutual benefit. REFERENCES Cheng. R. T. and McDermott, H. J. (1991) Exposure to asbestos from asbestos gaskets. Ajtpl Occup Environ. Hyg. 6, 518-591. McKinnery. W N. and Moore, R. W. (1992) Evaluation of airborne asbestos fiber levels during removii and inSUUalioR ofValve gixkcU and packing. Am. mJ. JJy^. Ass. J. 53, 511-532. MiUcue, J. R. and Mount, M. D (l J9J) A study determining asbestos fiber release during the removal of valve pocking. AppL Occup. Environ. Hyg I, 790-793. Ministry of Social and Work Affairs (1993) p-bUd Asbestos, draft 6. General Director of Labour. The Netherlands. . 1 . Ministry of SooaJ and Work Affairs (1994) P-bltd Asbestos, draft 7. General Director of Labour The Netherlands. ' NIOSH (1989) Method 7402--asbestos fibres. In Manual c/ Analytical Methods Prd Edn). National Institute of Occupational Safety and Health. Cincinnati, Ohio. U.S.A. NVN 2939 (1987) Air quality-work envirooracnt-daerminaiion ofthe concentration of asbestos fibres by light microscopy after active air membrane sampling Netherlands Standards Institute. Delft, The Netherlands. `'