Document pBQKoLpnajZQqBjm18R01860D

4m Om*. Hyt- Voi. 14, pp. 235-MO. tamo* Ttmt |*?|. hM is Of** Briate A COMPARISON OF MASS AND FIBRE CONCENTRATIONS OF ASBESTOS DUST IN SHIPYARD INSULATION * PROCESSES P. 0. Hamub Motet! RoMtrch Unit, HM Dockyard, Devoopoct (JMrti/manyWI) !Mnil tlwwwH tea boot read* of the mess aad (Km coaomtnidoao of dm proowoB on| <hp)M pnoM> wvoning mmoi JtMtmg meiwjaN. iob^imh a tha mate of ititiuri^ tots! dmt, `isspiiMs* teat aad flbct cowavrwlon ahow that innteottfctwmmtMMtt mo tot wKtblo to amWnnaiaefilI aoatoriee it Novtl Dockyard*. The MbflM (ter Ndtte for otfeMtaf Kbit cawotiiiicw It ncomnoodcd for that pmfom. Tm APftiCAnoN tad removal of insulating materials containing asbestos during shiphufldJng tod refitting are both eeaoriated with potentially hazardous concentretioos of asbestot duet, British Naval Dockyard! now oat a standard method of monitoring aibcotot dust which k bated on the membrane filter technique described byHoumOMS), The membrane filler method enables asbestos fibres between 5-100 pa loot and with length to breadth ratio of at least 3 :1 to be coasted. The sampling technique* involved ia tbk method ate relatively rimpte, aad air may be drawn through the membrane fitters for long periods using mechanical pumps. Short period samples may be taken with a ratable head pomp. The methods offixing the deposit, clearing the opaque membrane, aad counting tha aamplt require die services of skilled technldene aad they are tadloos aad {uue-cunsummg. Methods for measuring dm maae concentration of duet ia air ere simpler aad qukkar and are obvioaely urncdva for uee in roodae monitoring of dust levels. In order to see if mess cooceotradoo measurement would be a suitable method for monitoring tha dost coocentrationa aaaociateif with asbestos processes in Naval Dockyards, k was deddad to compare tha results of such measurements with those obtained from membrane filter sampling as part of a survey of asbestos hazards in Devooport Dockyard (Hajums 1P70). . METHODS Mass cencwstneriM Six Ceeefia type USA MRB samplers fitted with horizontal dutriators were used for the gravimetric estimations. The ehwriaton are designed to afiow only the `respirable' friction of the dust to reach the cohecting fibers. Three of the samplers . ........... ., .... .. ...a*.,........................................................... ;r- wen fitted with a by*pess for the dutriator in order to collect dust of tU sizes (total dust). Hils study does not consider the problems caused by the fibrous nature of asbestos dust when using size selective samplers for gravimetric estimations. For the instruments used in this study the *resptrable' fraction of the dust is that defined by the Medical Research Council (Hamilton and Walton, 1961). The samples were collected on Whatman 5*5 cm CF/A glass fibre filters and weighed to 001 mg. Flbrt comctntration Hunt personal samplers (Hunt and Ellbon, 1963) were used to draw air through 20 mm mflttpore type OA membrane filters, pore size 045 pm held in Cdman timnifiimn --mpHwg h--The method oflbdng the samples, clearing the membrane, and counting the deposit was that described by Holms (1965). The samplers for total dust, `respirable* dust, and the membrane filter samplers were placed side by side during different processes involving asbestos insulating materials, and run for the same periods of time. RESULTS and discussion The dust concentrations associated with the removal of sprayed croddolite aebestoa, the removal of pipe lagging, and the application of pipe lagging ate shown inTables 1,2and3. The relationships between the threedust indices ere not sufficiently good for ay ooe of them to be accurately derived from another. There k seme ooodatioo between total and `respirable* duet in the stripping procedures (Tables 1 end 2% but no such tendency is seen for the application of lagging (Table 3). For toe stripping procedures too degree of correlation between total dust and fibre concentration, and betwwi *respirabio* dust end fibre concentra tion is less than the relationship between total cad `respimbfe' duet The gravimetric indices show very tittie relationship to fibre concentration in the application processes. There ere very huge varietione in aB three estimates of dust concentration for each typs of process. The results from the stripping procedures show that for a given respirable mass there are most fibres during toe removal of sprayed aoddobte asbestos, lest in the brick stowage space and least fibres in toe engine and boiler rooms. These differences ere probably by toe nature and amount of toe asbestos materials, the different methods ofremoving them and the sire ofthe compartments. The dare on toe application of lag^ng show much lower dust concentrations than found in too stripping procedures There appeals to be tittle change In fibre count with mare at three low concentrations but some very low moss measurements in the engine room samples give a very wide range of fibre count The consequence oftitis was to give an apparent negative condition between mass end number, which is refer retiAriaLTte oonoirekre toaa mBt.fan.drewn la that where fen la tittfe carnage to mireaimg mreenaw comiremg reremaiy snmn ureueres or arereme, reew toe * .a concentrations remain low. The strippingprocesses are much more vigorous, and the material! contain more asbestos, so that toe fibre concentrations during there proceeree are very high. A coinpvtioi! of mm sad tibri coocontmtoa of asbeoai duu 257 The speed and simplicity of mast concentration measurement of dust in air, compared with the slow and .tedious method of measuring fibre concentration, are two advantages which should be considered when deciding on the appropriate method of monitoring dust exposure of men working with asbestos. Roach <1965) suggests that weighing `respirable* dust is, in some instances, the best method of monitoring asbestos dust level*. litis k probably true for manufacturing processes in which the asbestos content ofthe product is known and remains constant, and where the process is either continuous or repetitive. The processes involving asbestos in Navmi Dock yards are varied, and the amount of tsbertos in the insulating materials also varies, so that gravimetric estimation of dust levels are unlikely to be of much value unless it can be shown that for specified processes there are dose correlations between mam and fibre concentrations. The present study shows that there is some correlation between man and fibre concentrations in those stripping processes with high dust levels, but that there is no correlation between the dust indices at low concentrations. Tam!. Oustcdncsnt*ationidukjnokxmovalorvAra>caoaoounaskvtus Oisriawric tanpfas ma/a* Total dun Rewritable dust FHxt* pcrcn/7 17* 1-2 22-1 274 101 2*9 27*7 174 21*7 1*7 23*9 2*0 9*7 1*0 1*2 125 374 09 13*5 24*1 23*0 lOl 434 13*3 49*7 Maan coafl--trartoa 17*3 SUMM deviation 15*9 00 7*2 OS 02 20*2 2* 1*7 13-2 90 3*3 OS 3*3 14 3* 03 05 5*1 184 4*3 OS 104 13*7 3*7 23*9 10* 20! 7*90 098 192 ia 23 213 495 117 93 371 4S4 38 43 61 $4 210 177 57 120 311 296 412 375 384 110 343 360 m 22027 140*0 rfiririrtna oMAdnts; Total vs. ttbtm/m* r--OS?. KaninMe v*. Bbmfcm* r--477*. Total n. fphiblir--0*73. Tails 2. Oust concentrations during removal os pipe lagging Location Boiler rooms M SB concentration Standard deviation Easbas rooms Mean concentration Standard deviatioa Brick itowaga rone* Mean Standard oAm____aooa mm concentration Standard 0A9--V---M--O- O-O_ Gnvkaetrk samples nn/zn) Total dust Respirable dust Fibres per cm) 760 6-19 13-54 761 SOU/ 24-66 4-14 11-73 9-80 17-32 5-06 4-45 3*21 3-26 3 13 2-14 16-21 9-72 1-35 1-38 3-61 3-95 2*17 1-71 24-7 56-9 68-0 41-9 152-2 123-0 66-5 50-7 186-4 135-0 61*5 26-3 13-23 11-62 *61 21-00 9-5S 2-90 1-96 4-36 82-76 414 5064 0-35 25-0 2-40 115-0 0*1 70 067 27-0 1*37 84-0 723 7-54 31-59 35-49 35-66 233-30 264-30 1-12 0-72 25-57 15-03 14-34 85-50 toooo 516 409 3090 2256 337*1 8936 331-0 121-5 104-4 48-1 36-97 All compartments 36-47 13-36 61-53 25-93 419-7 241-3 152-25 190-26 Correlation cosfldsnts; Total va. tbnfcm* r=0-789. lagiraHa vs. ttna/cm* r Total vs. mpMMt / 09*1. 240 p. G. Haim For practical purposes the processes associated with high dust concentrations are known, the workers are protected, and others are excluded from the work area, so that dust monitoring in Naval Dockyards is now concentrated on evaluating the safety of places adjoining the asbestos work area, or in places where little dust is thought to be produced. Gravimetric sampling is not a suitable method for this, and the measurement of choice remains the more difficult membrane filter method of estimating fibre concentration. trrwudMrwsw* This work forms pert of the Wady ofasbestos hazards in Nsrel Dockyards uadsrtahm by the Madfcal Rasaarch Uait, HM Dockyard, Devooport, whkh is sopported jotady by the iakkuft ofNaval Msdfcfaa. Atwntok* Gosport, Hals, and tht Medical Research Couocfl Tiiiishiii isdraii ITrft rmartti 1 am Indebted to tht Directors ef both InarttaHom, and their staff ^--*iiT|r ~------ `r1--i-- thfcraport Mr. D. twanr of Dwoapott Dockyard was fpoaribis for tbs svaiuatioo of Um duM "TS-a la this papsr art part of thesis approval by tht Uaivsnky of London for tht deans of Doctor of Medfciat. REFERENCES Hamltok. R. J. andWalton, W. H. (1941) MafafAarrfcfcs md Vqppmj (Edited by Davm, C N.L pp. 445-475. Pergwnon Pjm, London. Hamm, P. G. (1970) Tht effects mi control of dhsMea areocieled wkh exposure to aabcRos ia a Naval Dockyard. A Thesis accepted by tht tMvenky of London for the degree of Doctor of Midictaik Houm, S. (1965) Am. NYAt*. Set. 18,20. Hunt, R. and Bumon, M. (190) Id Freer. 12,14$. Roach. S. A. (190) Am. NYAe*. Sri. 132,304.