Document NrzORZBeb6drzoRNgYX61DXR

INTRODUCTION . :, .. c -. .-.,. . ..: ._- .-.. ...-^I. -<. .~ .. . ? .. .. * .. AIR SAMPLING Ptrwmt urnpiing for benzene vapour can p o v t d t a quanrhtive index of. w d t r ' s exposure. Siigbt mwr m a y arise from spatial separation of the sampiing htJdfrom thc nOlt and mouth. ' ut thi5 can be mtnimued by s h d d e r m o u n t h i of the mmpkr. Larger u n c c t u i n b m a y arise when relating this to possibk intake ofkb- LQIC as the individuri's breathing rate and the proportion retained arc usually nn- known. Mthough these factors arc important if the toxicity of bcnanc is t o be defer- mined, thcy aft not involved in assessment of exposure by spplkati0n of thmbdd limit vducs. though it must be rpprrclatcd that the latter arc pncnlly derived from measurcrimuwith a limiud number of fixed posltion mmpkn that may not provide a true measwe of expourre of any individual. In &&e&ration sf u i e thmhoid limits from occupalional studies, it is cOmmr-;l prraicc to calculate m a n values of an appropriate biological paramcur for a group of workm, and to relate thir lo an estimated environmental coaomtration o f the mated in air. ilus technique should be regarded as suspect, as it should only be applied where exposure is shown to bc identical for 311 members of the group. In the Autbor's experience such rirurtmm arc nrc and it is usually necessary to assess each indinduol's exposure scparatdy. An initial pro- facing a hygienist is that air concxntntioncriteria are too many rather b a a too few. Values ofthmhold limits ranging from 100 to 6 ppm have ban reported (INTERWLAAT~~O~rOnRcWE, 1A968L). In the United Stam rionc. v d u a ..from lOOto IOppm h a v i n g d i f f m t applicationsarerrcommcndtdbythmauthonticr (AWEUCA?~NATIOSALSTAHDARW l m 1969; AMUKAN CONFtblENCE OP WFXNUEWN INDvrmAL Hvcimnn 1971; AMERICAN I N ~ I A HL Y G ~ I ! the recently cnactcd Orrupatiorul Health and Safety Act (19711 prescriber t h a i the ANSI standard t a k a precedence. This rpccifier m 8cw)tabk maximum for puks of 50 ppm: a a i l i n g cooncentration of 23 ppm, and (L time mightcd a m p of IO ppm. The interpmntion of air sampling results has bcendiscumscdelsewbm(!hammoo, 1971a; J O m s and BRIEF.1971). and will only be rumrmriztd hew. Results fmrn any series of air sample measurementscan be described by 8 prob sbility dis!tribution, and this is commonly found t o rmroximrtc to thc logarithmic --. , I. . .. i normal (cec Fig. l i . As there w a finite paslbiiity oiexcttding any gvcn conctntraoon up to saturation of vapour 1n tne at, it u not poraib& to apply any obsoiute uppcr limit below that concentration. However if it is accepted that not more t!zm one f@ninutc umpk m y exceed 25 ppm, then (as there arc 48 such sam- in an 8 kr working day), thc probability of e x d i n g 25 ppm should bt limited to about 2 pr cmt. Thus, criteria for safe exposure arc that the a m @ concnMion over the working day ohoulj not c x c d 10 ppm. and that the pmbbility cf excttdin8 25 ppm in any :%-irun period h t t l d not be marc than 2 prmt. Some pcnonal air =mpkr mcasunmntr of e x p u r r to benzene vapour during the buik loading of pctrol, which commonly wntatns Jd pcr cent knztne, arc shown in Tnbk I . AIthough generalhation cannot be made from so few results, they do show chat n o w of the operations studied led to the duly umc wighhted average limt of 10 ppm being exceeded, and that only driven loading road tylkcn cxca&j the r h m tcnn cnteria during the penod ofloading. As dnwn do not m m U y spcnd more th.a about one half-hour per rhtt loading tbtu vehrle, the probrbiiity of the ceding value af critcna m n g cxcrcded was about 0-2 per cent OWT t!x whole shift ;;cn+-d T I Cb l ~ h C X p W J r C 5 mcdwred at w e partmlar rail loadina T A ~h;t\.t k n criiuticd frnm rht3 dara. as the operation i s rxcgional, and has been reported separatciy. ( S I ~ L R W ~ D . 1972) A programme d measurc--m: continues and more &hnttlbe infurmatton w d be availshle in time. T h i o form of analysis has also been applied io ihc data collected in a survey on car filling sponsored by thc lnstitute of Petroleum (PARKINSON, 1971). At typtcai retad filling stations it was found that the probaabliity of 25 pprn being excetderi was much less t h m 0.01 per T n t . while mean concentrations vaned from 0-3 to 2.4 ppm. Proposed new critcrinn +hi$ t j p cf c\.aluation is laborious and can oniy be undertaken as a spemai investigation. However. routine monitoring of all benzene workcn should k o n x economically feasible. as it has been shown (Swtucrm. 1971bl that in praciiic rhc proposca criteria a n tx met by settin8 a limited dally c x p u r c dose of XXX, ppm-mrn (that is. the multipk of concentration in pprn tnd exposure time in minutes s h o d not exceed %, X),I idepcndccltof time from a few minutes to an U-hr workingday. The application of such a criterion avoids the complications that arise in interpreting mutts against a 25 ppm ceiling vdw. and the Ilccd to m t n c t duration of each sample to 10min. Further, it would permit the construction of a simpk personal air sampling imtmnmt requiring only r sin& sampk for each shift worked by each man. Large numbers ofrncn couM be monitored in this way and. if sampies arc analysed at a central kboratory, rutomatk gas chromatographic quipment would prow economic. Thmhald limit values arc generally the only legislated o r rccommndcd numerical criteria ovaihbk. W k criteria have bcen proposed for benzene in breathand phenol ia urine. t k y 8rc not d erUblitbed. It is. therefore, essential that international S m t be reached on 8II 8cceptabk value. and a daily exposure dose of4@Xlppmmin (which cornsponds to 8 time weighted average slightly over 8 ppm lor on 8 hi b y ) is proposed by the Author. limit would not carry much greater biological risk than the USSR limit t t X H . \ L t 9 O R t .\T H S A M PI. 1 NCi 5:z$i;g ~ f t ~ F ~ k!rrc';dlt:i G-Cci cxp-#wiieLO krricnr tdpour inciicatri tile rate ut duch knzcne 1s k i n : d ~ r ~ r ci !y:~:n3trz!from :he bod?. from which i: may be pi?;sthlc ! o d d ~ ~ tche qu;tntity a k v W . J l ~ ~ ~ ~ i . .ixltic~<rit py v l u r t . i k t c c n v c n i q t i o 9 i n exhaird 3 ~ c a : i :drops rapidi);, 'nul ri,c rate oichanne irssens iarcr i i i i i s ~ ~ iu%.b.ilkt. i t 15 rrslicwablc lo s u m m e that the prxess can tx reprcxnted by storage in a sene of compartments within the body, climrndaon :ion each k i n g adequareij Jw-rikd by a n exponential lunction. Thus, at fiw h e n 7 r ~ 4ir npidiy Iort frofn the r.!rcz!;tting b!oori. nexr, tbc pnnciplc ccntribui i i > t l m i l k L o m e F r ~ mntuu.uiar tiswe. and finally, the siow component comes from iat. I! tt)ctC.xm.wr.: p x i L M 1 :5 E - I ~ rci x~n. iirtk kun:trt ~ a c h tms u x k or fat. and ctirmnation wiii 'be cnaractcnlcd by a single rapid period of rtkase. If thc exposure period 1% img. i?iena $rea!ttr propcmon or tk- total wiit bc rrieascd only sfowly. In practice, indusrrml cxpsure i, commonly not constant with ume. and absorption and elirnmation processes are in continuous dynamic change. If eihakd breath measurement iq to k applicd as a routine method ofmonitoring men exposed to benzene, only two o p p o n u n i t b for sampling exist-immcdioteiy dfter each shift and i m d i a . ; l y before the next. End of shift sampling provides t k most sensitive method of assessing exposure as the raze of elimination i o likely to be high. However. unless the exact time 3nd duration ofexposure arc know.1, the m u l t s arc bareiy quantitative, as exposurn towards tbe end of the shift is dctectcd with a much greater sensitivity than that .xar the beginning. Pre-shift ,ampling s u k c~onsidcnbfy lower rcnutiviry. but is far more quantiLatire ;is the c f i m ~ ~ t i oranie changes only slowly at that time. It provides a measure or 1iK iongcr rtuincd components ana may t m t o r c hc a g o a l index of' the nit of chronic disease. Dtsadvantagn arc the greater skill required for analpis at the low concentration3 to k rnmsurtd. and the risk of intcrfercncc from non-occupatiorul cxpsurc to Dcnzene. The two field methods dcvelcped for sampling exhakd breath arc breath sampling tubm and the breath sampling respintor. The former have advantageofinstantaruow collection. compietc absence of chemical prctrcaunent before gat chromatography, and ~ d toly1ez:nn c.f d.;pika:t ~ n p k 5 ..\Ithou& thc latter rtquim I lamia sampling prind for each opcntor. it provides a more consisrent measure of climia. . . ation. as all exhaled breath over rhe period is saampkd, and it rtduccs the risk of intcrtirence from ambient bcnnne vamur. The respirator method is better suited for spcckl investigation of exposure, rad the scnsitivlty can hc Increased consderaMy over the method as publishtd ( S m w o r n and C~ltnr.1970). w h k breath t a m d i n g t u b a could be more s u i U b k Ibr roufine auhsment. For routine mmionng, u m p k arc bcrt taken at the end ofthe shift and andyKd promptly, w that any follow-up s a m e neededcan be taken before the next shift commenctr. ., .. ,1 t-I .-, , ;. .?,. ' - AS :r ,urrenri, iii iT,ojI .3mrnmi\ "ZLIm n n i q u c i v r i c ~ n ; i r f i r r t ginL ~L..III~I:> ofbene tmng mecabdii~din thc wortcr'r M V I t may a i m he t h e best i n d e x o i hazard. but the MRJC a ~ i t o nof hrnrcnc tn the m-jv IS not sutficmrfv cnderstotd i t w tbis to bc c,.tam. T I , . x L + G ~ L > ~ ,I <: : C ~ C .;i ;X rr-dt i,d-, ?.cP.. * t i * Liuk.&iL4 :I\ v'w'iLLiALi5 (19MIfrom aninul eapcnmentition. and diitribution in the b o d b of the dog has k e n txpiored tJj E~:Rc.K i~P:. [ I%%i. ::ikzs ! X C ~~ S ~ I S Z;C,X~ ii uniihr Wtiern GC'CXS IZI hilmn5. That p- * of !hc tvnzrnc w h x h i s tiken into the M y and nut cxluied 15 13rptjv conrertrd in the liler t o phenol. and this IS danxlfied by coniupatron with r d p h d i c t v gIi.rcurtmiJe .if .f excreted in unnc 2c!.ition;htF$ crf t y p o 3 w t and rhenol cxcrewn narc lKen rhorouizhiy n v ~ w e aby ZCHTFRand Zinmrs 1 i9ri7j The cartier biologrcal monironng method of determining the ratio of ethereal to inorganic suiphate is less sensitive. Although i t detects the same mechanism, normal ~ ~ c r r t i n.n>fculphaie i3 far greater than, and mort variable than that of phenol. Citiwtrnetric rnethodo of dnalysing phenol vary in thew spccrficlty, and all suffer vlicricrtncc from one or more CEH)IIC compounds which may ne naturally present. Procedures for hydtoiysing the conjugated phenol have been the subject of COO- rrocersy 8s ti has becn mown that .cry strong acids arc n q u t r d to free phenol from the glucuronide conjugate, but this procus m y destroy free phcnol llrrrdy present. R-MMY good correlation between results using strong and dilute aad methods applied to field samples has suggtlttd that phenoi glucuronide is not commody prewnt. A series of sampies frum cxooxd men was hydrolysed by mort specific methods and the results arc shown in Table 2. The sum of phenyl sulphate and phenyl giucuronide frequently LX&S the total psxsKd by the pctchlortc acid method. Measunmenu of free phenol madeon m p h 3 and 4 only showed 16 and 70 mg4, mpeaivcly, which is insufkirnt to ilmunr for the J~tfere~ccS.lightly rncomplctr hydroiyus by perchloric3ad, or pmal destruction of phenoi are possible causes. The results show chat phenyl ~ulphueis the major mttamirtc cxcn~caby rhc men measured. but the proponion of giucuronldcexcreted may nsc at hgh(>400rng I) total concentnuon. While nydtochlonc aad hydrolysis may bt suitabk for a d g taf it appan nwccssaq 10 use prshlor;.c acrd for quamtativc Wefsment of high values. Close lax, 954 163 362 161 109 69 83 3 1 44 349 3.2_ 2 IO 2 Criteria In the United Kingdom. a biochemical thmhold limit of lo0mgl has bcen proposed (1969 REPORTOF C I ~ IFSSPECTOIL OF F A ~ J O I I ~1E97S01.. This is in the same ranp as the Cntena a l d y proporcd (SHERWOOD. 1971b): .1. Immediately afttr e x p u r e to U ppm in air. . 100 mg 1. ..?. 16 hr after exposure to 100 pprn-hr , 50 mgl. Further experience is necessary before a reliable cnrmon WB be JaJuad ior samples taken at the end of a shin exposure to 1ooo or ,Wx) ppm-mrn with cowentrationr having geometric standard Jevisrions varyang from 1.5 to 4.5. Working grudc lines for the managcmtnt ofa mutineurine monitonng programme hrve been prrpad and arc shown in the Appendix. COMPARISON OF CRITERIA In field sampling for operational invcsugations it hat pmvcd difficult to o h n data to conBrm the relationshrpr of the three s~.stcmnof measuremmta, but romc b t e d infonnauon that has been obtaud 1s shown in Tabk 4. wm Lnmges ocwr. rhry wnuld not stnousiy afkct rhe interpretation of the mulu. Jntcrprefationof 3naiytical results for phenol in urine is made difficult by a number r l i I-lrtorc. Phcnal itself is normdly present in urine in small and variabk amounts. hut it is believed that a few indivrduals may n m n d l y excrete concentrations which approach the criterion for exposure controi. C'atain foodstuffs and drugs may also increase phenol excretion. as will exposure to phenol. For exampk, a concentration of 100 mg I was detected about one half-hour after accidental skin contamination by phenol which war raprdiy treated. The concentration fell to W rng4 1 hr later. and w3s dcwn to 23 mg I 3 hr later. This s u p t s a half-life in the body of 1-2 hr, which can he ccmparcrl with that obvrved after exwrimntal and occupational Ocnrenc exposure 01 one subject ( x e Fig. 3). which was of the order of 6 hr. a value which also t f w r i k s the overnight encrcrion from worken employed on btlk loading of A H.4THFMATIC.4L .MODEL FOR B E N Z E N E IN THE BODY The hazards of ingcsung or inhaling radioactive substances ho.-ebetn pnrnarily ssses.~!C:GT :be corisrrtiction rif mmthemattcai m o k i i i 3 r t m u n o w A t C o r r r a s u ~ ~ ON RALWWGICALPXWECT~ON19.59). and such a technique has k e n used to csimatc upc& and eiimination of anacsthe:~:gucs (PAPPERand b T t , 1963f. Expcnmental and wupationai exposure to A y k n e chlondc h u thus botn described swth 1 ccr?.pz-a-tun!d c l by RLS.Y et PI. (I=). &AVCnion OfbtnZElle to p h o t and ILS elimination must k taken into accuunt and thu p r o a u hu been described for a drug comportmental model by SCHN~DE(1R970). As industrial exposure to bmatne v a p u r is typically S a y variabk, estimation of the burden of kazrne in the body, or in such organs as brain or boae marrow, is only possible if computer techniques arc employed. MAPLESON (1963) describes an analogue computer for common amethmc gases, but digital techniquer wouM now be prefcmd. Such calculatiom q u i r e infomation on the uptake and relase of beamc from body organs which is not available for man. However, eslirrmter can he from a knGwMgc ofthe b l w d pcrCusion of the organs. and the partttion coetkients for benzene in blood and the various tiuua. Purrition roeflcienrs As no published information could be traced for thc solubility of bentme in fat, simple range finding experiments for both blood and olive oil (rrprrtcnting fat) how httn made. t'ompufer progrtmwm To pernut better evaluation of criticaf organ burdens, a dignal computer pro- grdmme has b a n prepared (NICE, 1971) and i t is hoped at a later stage to incorpotrte into the proprome the v w n g coeocntrations met in oaup.tioorl expmun. If tk aumcrical results arc in accord with obocrved valuer in the M,thir techoipocrbouki provide useful information on tbc probable burdcar inaitial orgar drtring and a k r occupational exposure and would, for eumpk, permit asscsnmt of the relative biologtul significance of the 10 ppm time wei@cd werage snd tbc 23 ppnr ceiling thmhoid Bmc. t. I' i i m:Iht mwqmuum d m o n l l lC~ yilU If i n J i v i d u h in one g o u p arc cmmatmtrv !ow. drop to monrhIy urnphn& A i exporun may noi tn uerscude a i k r 2.; hr, Airangt programme to c o w mods whca e x p u r e IS IIMJ. i&qmr p a u l urnpies If ra#fcnt I9 ~wpectedor rrmt exp0l.m may luve ocrurrcd (rncfude m,.irrmtnt on spaclat work pcrm&l. R t w t ietdtr if specific p m y a3 W o w 1 010. !f such a u m r f e show tilore than .u!mg I, take dcolEd umpk. Wbca ptoorammc has mtkd, check also men who may haw toutme uporure to p product3 conummg L-!O Fer cent bcnzcoe. Furtkr monttonag for th group depends on results actually obtained. After about 1 year. appIv stdtiLtlcpf methods t o assess nsk o f significant exposum and to coaud fururc pro&ramme. Btntmz 1s a ~hrotlrrpt oison; pay attention to iong-term exposure conditions. One Iugh rad&IS probably not u)ripniSant as two or three results at lower lcvel--tbae show tha! iowgatioo .ad improvement ir required. Penonid air myding and exbakd breatb measurement arc dso important techniques; the first is more seautive. the second more specific, than urine analysis. &reUi.nvc suadrrds g e n e r i y refer only to wr sampttng. .,..,. .... '. . .. . .'. .4. *. ;* .