exposure estimation
TRANSCRIPT
M<thod. r", E.u.im>.""1 Risk of Cbemal InJO'}'". /l........ and S."..h........ B,Olll and E«i<,,=.Ed,lOd by v B Vook. G C. Bud",. D. G. Ho<Iand D, B. PWalJC 19l!l SCDPE
Exposure Estimation
B. G. Bennett
ABSTRACT
The estimalion ofexpo$ures ofecoo)'lI.mo and man to .n,'ironmeotalpollutan\1requ,rt1 wide ~nawledge af lhe characterinics af saur=. subitanc.,., en,-iranment and receptors. The genoral procedures far eXpo$ure osumalion arepreKotod. including the ~Onc.pl or uJ'O'ure.•n"ironmeotal traMport andbehaviour. and mc:labolic beha"iou,
Seve",l mod.l. are uoed to d..cribe diol"'rsion or pollutanu in tb. en,ironm.m and Ih.ir behaviour within OC01~OI."" and within lhe human bod)'. Asequonco of mod.lling ol"'ratians ma}' be .mplo)'od. ror ¢"ample. air di'l"'"ionor aqualic lransporl modelf 10 d=ribe init'al mov.m¢nt or th¢ pollutam f,omIhe souftt followed b~ food-<:hain or ocos)'l1.m mooklf to d.lcrmin¢ furlh.rlran,fer to th¢ receplor,
Tht rt1ullS ofmod,llong are used in conjunction Wilh tho rt1ulu ofmoniloringMonitoring programm.o pro"id. !luic data for inpul 10 and validation ormoods. The g,ntral r,atUrt1 of en"ironm,nlal and biolosical moniloring arebri.f1~ di",us..d.
Expo$ur• .,.t"nalion b~ mtano of mod.lling and moniloring makt up lht lintflage or pollulanl aM('1$mtnl. It b n=<ary to comb,n. th= rt1ul13 wilhinformation on loxicil)' and dfocls of tXpo$ure 10 pollutanu, Th' compl.1t,xpo$u"" and 'ffo<:lS tValualion. pro,'ide hazard a......m.nl oftht poilu lam andpoim 10 tho mt3$ures required for prt'"tJItion Or conlrol or damag<: 10 humanheahh and 10 ocos~sl,m,.
1 INTRODUCTION
Th' hazard. or ch,m",a!< r.ltaoed b~ man into lit, elwironm,nl d"J'Ond moslgw.rally on lht $OU":. production and ,..,ka.. ral.f, Iht ¢n.ironmenlaldi,pemon and pe"iSl'l1<t, bioaccumulalion and loxicit~. In thi' paper Ih'mc:thods for "'limaling ""J'O'ure of O<:OS)"I."" and man a,.., di1C\lsstd, includingtn,'irODlntnlal and biolog"'al moniloring.
Evaluation of Clpo1lU,.., of bioloPcal organil",., iocluding man, 10 ch.micabin Ih••n"ironmtot require, und....landing of Ih. tn"ifonmental behaviour of
""
l!ilfeKO\ 1~b1~ thclf lDO',CIllCllU, lDl~rattiatu anI! lfilllformallOllS lD""nous mcd'" Althoulh tho brosic C)dLllI oht;>o;t' substantft III tbe en' IronmentIS rr_bly ....,11 undtnlood. ,be phl'",,!. ~hcmicaL bIolopcal and ,n,~l'KtJon
propcnics of spca/l< cbmuals CO>'CJ JUCh a "'ide ......,. thaI ncb substal1oc: In
ncb ..."roosm<1ltal 0""''''''' ttqU>.... I gn"l""" • en'. Ow 10 'Ilbnmt>-ariabili.... and lDCOrIIpInc dati bun. pattJeUbrly f.... onc~ gnomatll'ics ill ,be nposurr ~"IIIlI'lOIISannot lie .'o.d~.t
1IIf00000000l>Oft rrql11rcd 10 dncnbt ...\~tal bdIa"o'" of chmuo::a1smctg(\es phy-....al.lld ~Iltmlul propcrutJ of tbt SIIbstouooo and cbaracttn$lll:S..hid! dcItnIIIDC "''lrc>rlJOlaltal ...."ftIOm, and f."" Tbn< propnIIft mcludeoolubolity. lQCtI>lly. ,obulu). dqradatioa poIentiaL boc-., ....bdrty .. ",dl ..
......c .nnbut..ofd>SPC""'''' mod.. ouclI ....md <pt«l. .... "''''. pH.Pi-- ofotpaic .....,ter. panlCUJa'" ....Un and booIopcal acu"ty, A oomplnc speafi-a ...... of propt'1'tJe$ IS fl<UU&f) f.... d<\a1lcd thr:maueallDCJdtlh..... bu' ~.....In incomplnc hsutl. nil) md.elle I""ibm 10 tbt lleba"o", of bettn tDo"'"1I...""........
A crea' '..net) of mockls baH been formulated to dncnlle ,he, 'C1llporal Illdspati1l '"nabollS ofC(lOC"C1ltratJOllJ ofcl><mlcaJ substa....... as ,Iwy mo'~ ,hrOll&!,the en>ironmnll ~mod~l. I"""llll rdlcet C)diDI of subftanors ,n th<Ilobal. rq:ional or loal en' Ironment. or '""b,n ecosystems. Of ,ht} 1l\I)' dncnh<the """"ha""ml Ot ,""hi of 'nt~rac1lonlofrn\"ronmenUlI componentl. Mlldell"rr ,imphficd rrpttSoOntlllonl of plI~slCallodmolollical systrmo, Slmplc modtlsart: an lid '0 bolh und~rltlod'''1 the lnt~rpll~ of ,,'Stem componellts Inddescnb,nll Fnel'llliud \>chlv,our, Morr ad\lt>C«I mod.ll. whICh can be\'alida'cd ,,'ilh .'p<'nm~n'"1 Or field da'a. can Ilraduall~ na"o" ,h~ d.ll.... of"nur,aln,y in Ip<"'ifllna ,nttractioni Ind in pw:hctina fUlurt: chlnaes,
[n addillon '0 kno",eda. of ~n,'ironm.ntalbern...;o", of ch~micals. ,nfOI"ll\l·hon on ,h~ ac,,>ity lod consump"o" habits of 'M orpn,.m or md,"dual 'srequired ,n nposurt: "'alua"OIlIIO Ikt.rmin~ the iOlake amounll. Me,abol"ma/fcc" lhe, distnbullon and rrtrollon of chemICals I.Dd lhe"r byproductl In
Ko.i",'. ti..u.. 01" orpn. "he.. ofTCCli may ultimat.ly (lCCur, Informauon onsource rr~..... pall.rns 11 rrquJfC(\ '0 t111ma", Ihe k>-.Is of chmuClb til tbten,irOlllllCtlt aDd 10 ..lat. to monJlonnl and COfIlroll'fOll'llm.....
2 THE CO'CEPT OF EXPOSLRE
EaPOSUK is tbt q"""I,I, aptnSt "'hid! tbt md effect I.D) t-oIopcal1y.......undtt ~tlOll IS t..trd. Or>Iy ....thCX~ 10 ' CID tbm: lie IDeffect 0CCIIlTUII aba\•• """".._ ,"d, \\',t11 tnernSI!lI cxpoMl'" tbt rlflOCtappc-a1i 10 follo\o. _ hlIId of fl1l\CbOftl.l '~llJ'OstI1'<'-,"""","- rdaUOlllolup, lapnc\JCO......... spoa6< dcfuullOnl of tbt n:posu... qUID"') arc rrqlltrcd
'Er.poMItO-. aDd tbtdoMly rda'edlDdo/'lon lIl\n1;l:wtpbk "'onj·tIoIoc·....., ..riously lIKd tefIIIS '" to>JCOIoc and m,immDmtal ......... a II).
'~'p05ur" may simply mer 10 th~ ~nlluion ofa lubstance or physical agenlto a """plor and 'dOS'" 10 Ih~ amounl admm,SI~rtrl or lak<1l,n VLO inhalation,ingeslion, injeclion or absorption Ihrough the skin. 'no.e' hal been furtherliX'C'ifi<d as Ih~ amounl ttaeh,ng lh~ lM of elf«1 (Nordbtrg. 1976), bUI'~'po$Urt· il also used in Ihil C<lm~" (Bulkr. 1978). Th~ tono' inlah and uptahov~rlap lhese u,,~, inlak~ ref~rring 10 lht <1llry amounl and uplah lh~
absorbed amoum.[n radJat,on sll"h<$ '~'p05Ure' has a reslri<t<d ddinll,on. namely lhe ~leclno:al
chars~ produced by iontzinl rad'atton per unil mas. oh" Th~ 'absorbed dOS'" isIh~ en~rgy absorbed ~r unt! mall of Ih~ irradialed mal~rial. Absorbed dOS" illhe more wid~ly applied l~rm and 'dole-respo~' relalionlhipl are ellah[ilhed10 ",[ale funcbonaUy lh~ ~nergy absorbed by Ih~ irradialed obJecl wilh lheresponle ollotr.·<d.
In lhe cale of chtmical compound•. a useful d~finilion uf ~'p05U'" il difficultbtcaule of lhe vari<d nalu", of inleracl,on. and uncerta,n m«hanisml wh"'hproduce ~[fect., It hal been proposed 10 d~fin~ ~'p05u", a1 lh~ numbtr ofpnmary chemical ~....,nlllcad,ng 101M final dfecl (Ehrenberg ~I al.. 1914). It Il.ho"'~"~r, only in ra", caon Ihallht nalu", ofsuch primary ~"~n" il know" andlhtir quanlilkalion polSibl~
11 hal also been luggest<d lhal Ih~ ~'poou", 10 ch~mi<:al. bt e:<pressed a.radialion equivalence by equalmg lhe end elf«\I. Thil has only an empiricalbalil and d<>e!i nol appear 10 be ~nlirely lalisfaetot')· This C<lncepl and !heVanOuS limllallO\U 10 "l applicauoo ba,·~ rcttnlly been ~i.....<d (Mouslacchiand Lalaljel, 1979).
Exp05ur~ 10 ch~micall i. besl okfined in l~nn. of concenlnllion. aod thtduralion oflb~ lub.lance'. pr=nce al Ih~ poiol of int~resl. Conceolralion is th~
p.iiramel.... mOll frequ~nl1y a"ailabl~, ~"b~r in the .'tonutl enviroom<;JlI Orml~mally following inlak~ and absorpli"". To giv~ ~'poou", some biologicalmean,nl, th~ concenlrabon should. ifpoll'hk. bt upressed allb~ k".1 oflh.lar~l bJolog;cal ItruclU",.
In addilion 10 concenlralion, il musl be n:colnized lhal duratton of~'posu",i.an 'mportanl faclor ,n lhe manifella1l0n ofdJeclS. Thil ",flec\l~ilherlh~ lime foraccumuIalion of th~ lubslance or of metaboli1Ol 10 luffieJ.,,' lovd. to mducedama~ or Ih~ accumulalion ofdamaged ~lcmenllihal ~"enluall)' inhibil prop"rfunctioninl·Th~ mOll dtrecl combinat,on ofconcenlralion and dur.,ion in a d~finilion of
~'po$u", is lhe lime integral of Ih~ concenl"'t,on.
E - J: «l)dl
lbe COllC<1llral'OO may he in an envltonmcntal mediUm.lUCh auiror waler, 01 ilmay bt in Ih~ orpni"" or al a lpccific point In the b'olop;al .yll~m. This
112 MethodJ/or Ewmati'!{j RiJk o/Cllemkallnjl/f}'
f(lTDlWilU(lO (If ~~lXllur~ il pilrUl;ulilrly u~ful io lI~llOribio~ lht mOHm~nt (Ifchemical substaD<:eS in the environmmt. The transfe, bet"'een .n,'ironmentalre>efVoir.; is do>cribed by Iin.ar. lim-oroer kmetics. The lnlegrat«l coueentratio,," and al50 integrat«l flux.. maintain con"ant ",Iationship, in thi' case,
In t.nn' ofeffect.. this definition ofexpo,ure must be used wIth ""me caution.The various combinations of concentration and time gIving «Iual exposure. forexample high cOII<:<'nlfatioll5 of 'hon duration and low concemrations of longduration, may not be associat«l with «Iual occurrence of ad,"~ .ffects, Thi. isthe case ifthr.-shold le,'elure known to apply. On the Olher hand. ther<: are manychemICal' which are found to be harmful even .tthe low.'t 1.".Is, 11 may th.n bere.son.ble .nd conservative to assume a lin•• r rel.tionship betw""n .xposure.nd .ffect.
Oth.r functional fonn. of e.posu'" relauonsh,p m.y be required in the.,'aluation of spccifk effect. in particular biologic.l 'ystems, Some nf th....form,. invnlving ..ponential or po,,'er function' of time. h.,'e been discussffi byPiotrowskI .nd Buch.nan (1982). 11 ,,'iU be n=.ry for tn.icologisu tn givefurther consider.tion to the eo~mration-tim. relationship. i,e, th. exp"",ionof ..posu.." "hich i' most closely .UOCial«l with the occurrence of .ffects,
3 ENV1RON~IENTAL TRANSPORT Al'iD BEHAVlOUR
Environmental behav'ioUf ofchemical' i' most often described by repr....nt.ti".mod.l,. Mod.lIing begins with th. spcciticauon of the compartmental .rrangement which rellects the system compon.nts, For first "ag. mod.lling of th.regional or global .nvironment. very broad compartment indentification m.y be,ufficient: atmO$phere. l.nd. freshwater.;, oce.n. At a later "ag., more ""'siti'".re., m.y be eonsider«l. for ..ampl....tuan.. 0' .pecific; ecosy,tems, Simplifiedmodels have ad"amag.. in utIlity, lnere.sed complexity is ju"lfi«l only forsubstanti.1 impro"ements in ",Ii.bility or resolution of the resuUs.
Mod.l«an be bro.dly cl."ifi«l as either time-<l.pendent or tim.-ind.pend.ntm their basic fonnul.tion. Time-dcpcnd.nt model, give the dynamic beh.viourof th. chem;,;at substall<:<' in the environm.nt. Fint-order kin.ti", is generallyassumed and a 'y'tem of differential «Iu.tions d=ribe5 th. ch.ng.. incompartmem coments, Solutions may be obt.in«l directly. if pos,ible, or,imulation of the tre~>fen occurring may be carri«l out in .malltime sequences,Thi' may be referred to as a systems anal)'$i' method. It" important th.t thecompartmemal .rrangement be correctly fonnul.t«l .nd the ".r;ou, tran,fe...and tnterch.nges be accur.tely .pccifi«l to 'eflect the proper en,'ironmentalbeh.viour ofth. chern;';.!. A large data base i' r«luired to ..'aluate thi' type ofmodel, but the ..'aluation is most complet. witb amounts and tr.nsfer rat.. givenfor all point' and at all times.
A time-lndependem description of the behaviour of a chemic.1 can be m.deusing a more limited data base, In tbis c.se. th. objectiv.. are to det.nntne the
parotiomaa of lK..........,U ofcbmuc:alt m path"'-ay lDO'emmu and tOQUmatelK amouGU ",'hdl u111m1.1cl) rndl lK rcaptor, 1'bc rdatioDstupl bmto"Ml~lal a_u an .,.prcsocd u lK f"llIOI at "cady Olate. caUN lKccncmtnltaoa fanon.·1'bc tImC·iado:pU....tll appcC*h IS on"" rd"..-red to UlKCIDDOCIItnlUOQ fanor mnhod- A _-.don" applAUOQ ""ohml cumulau,. traIdf...per WIlt ..,,,,,t IS ealkd the "'poau... <:ommItmmt mnhod-
Eumpla of IIw two basic: lI.ppmacIx:I to IIIOddIutc .... Ii'.." by Roberu~l•.(19111)....,tb a IlmplL6cd tmeti< IIIOdd of tilt aqua"" ...,rronmcol. and byIlemKtI (1981) 1IIlll' tilt 1........U>depmdenl v.poaure tommltmeol ....thod to
",-.I""e ,.."...<nal and aq"'I'" patb...a), of,ransf... , Such examples may be tiltball' fo' ..n....hud. 'y".II1l1I1C .umll\O."on of the f.l. of chemICal. ,n lhe",,',ronmml. Particularly for "'......."'1 Ia.... number1 of chemICal•• II ISnecessary 10 dt't.rm,ne broad a,peets ofbcha'iour. """h a, lite litely scqu..t...·,ng compa'lmen" and hence: Ibe Iit.ly t'CCqlIOr1 of highe, e.posu,... 'he"",,in.nce palt.,n of chemical. in each compartment. and the lOam e,j>O$urcpalh"'.y,, 11 i. Ilten nCtt$Ury '0 con"du otlter ..peeu of Ibe chemlOtry.lo,i<:oloJ)' and «01"1)' of lite cltemical and 1M en\'lTonment-the po,.n"al fordt'VadallOll. 'M ,oa",,,y of Prunllry and doclradauon prod""ts. ,nl.ractlonfanoff. lolcnna: of -'P"cin to ••poau.... S«Ondary r=ptOr1. CI<:
A ""'llWtXl: of mode!!,,', opcraUOl1S ....y be «>ftdueted 10 compk1c an"'POSU'" ......menl for a cllCmical. for eumpk.•" dlSpcniou or aq... llCtnI11>POfl moddI may be .ppbcd '0 the ,,,,t>al mo.e_nl of the cbcmocal f"""tilt 10'"'''' to lK pornl of IIIlCfaL food..::lwn models ma~ tbcll be -.l todncnIuDc lK flIltbn- tnnsfn- of lK.bmucal 10 the ra:cptOtS. Tb ....,..:JapprC*h has bcm pafUC1llarl) doc\dopal and applxd to ....... the ...' ......mmlal bcba.'......, of ra.rbn0011d>ckl1ll the ...,lfQft11lm! fL"};SCEAR.. 1971; CEC,1979). n.. tDf'lbod.an~' .pplAb/It It IS "'" IWIlhie b<-tT to _to.comp.-.bmll'llllSt of modds. bul. bnd"~-....of tilt mam I)l'"' _) be
""'"'.3.1 Air DI.ptnlH '1*11
AlrtlOIplteric lran.port mod.l. mlc<:t the Impact of mcICOfoloJical fac,on on"""""nlrallon of trace ,ubllallCCS 10 a" (Turner. 1979). lnpu," 10 Ih. mndel.includ. m.t«l,n)o""al data and .miu;Oll ..tlmal.. , Most commonly. ai,dis"",,ion mod.l. arc b.oed on tb. G~u..i.n ""lulion of Ih. almOlph.ricdiffu5ion cq\lolI;On, Utlllly ofth. mod.1 WlIs.nhanccd b)' ,h. Puquil1 Giffordmelbods of ..lecliol paramete' 'al_ (GIfford. 1961; Paoqu,lI. 1961).Di~"'OD .."mal.. ClIn be made for ...ode ,.rxty of melwrolop:aJcondJuono. u ...',nd spm:laDd dutttOOf\ aDd .'mOfPhttlC ltObtbly, Est,ma .... forparticular a"eraIiD, pcnods are obtairICd by ...."'''''I tilt ruulu oaon!'''1 torla/1IClIl;) or oct1lmnc:e or pan,;ular coadlllOm (Tumtr. 19i(1).
n..Ga_pl_ rnodd _ for.w."...1nd lruopon at1d d"P"f'AI of
114 Mellwd. for Ewmali"" Risk of Oemi~al fnj~'J
sub$taru;c:s due 10 normal atmospheric turbulenct. A partICular result Mpend~on constant wind and stability conditions and. therefore. there are limit. on timeand di'taDCe "aMity ~neTally.prediction' are con.id.red reliabl. only withIn afew tens of ~ilom.tres from th. ",urce
E"im.t•• of the di,persion of .ubstances to gr••ter distances may be made byanaly,i, of the trajectones of the air masses which pass over th. r.lease point. An.xampl. i. the trajectory model of H.m.r and Ta}'lor f 1975). Trajectory model,are referred to as Lagrangum 'lr mOVlngcdl me'hod$. An altemati,," approach i.th. fi~ed coord in at. method. r.ferred to a, Eulerian or grid models. TheseprovIde a numencal ",Iullon to lhe three-dimen,ional adv'ection-diffusionequation. The panicle-in-eell technique pro"idinll multipl. trajectory estImatesmay be used in conjunction with grid model' (Lange, 1978). Th.$<' mod.l, canbecomequit.compl.. r<,<!uiring large computer capacity and must be backed bydetailed wlOd data. However, account can be tahn ofa wide ,'ariety ofchangingconditions and of compl.x t.rrain.
Mooelling the dISpersion of react,w gases. 'uch as nitrogen o~id•• andhydrocarbons, mjU"" information on the ch.mical kin.tics as well as the OJrfiow behav'iour, Int.raCling a.rosol-ga, system•. notably the SO,-'ulphat..ulphuric acid conv.rsion•. are complex and difficult to rep=ntlO atmospherictran.pon model•. Photoch.mical mod.lIing uses trajectory and grid techniques(Turner. 1979).
It i. nett$sary to a""ount for various remo"al pr<l'Usscs ofchemical. from theplume' and for ch.mteal tran.formation, ,,'hieb rna}' occur during tran,port,Thi. i. don. b; estimating .ffective ",urce strength, or C$timating depl.tion atvarIOuS stages of the tran.port. W.t depo'ition ref.... to r.moval ofsubstanccs byprecipitation fallinllthrougb th. plume (wa,boUt) and to anachment in dropl.tsin the ,ain forming lay... (rainout). Dry d.position occurs by impaction ofaerosol' on the underlying surf=. The deposition ".Iocity. "'hich i' the ratio ofaerosol d,pos,tion per unit ""'" per unit area to the a".rag. concentration of theaerosol in air- has been widely used (McMahon and I).,ni"'n. 1979; Sthmel,1980)
3.2 Aqoatle T,aa.po" M....el.
Aquatic tran'port of ch.mical .ubstance, " goveTned by gencnl watermo"ements and sedImentation proc..... , Models are categorized aocordlDg towh.lh.r r.le..... ar. to rivers. lakes. estuaries or cO<l-stal $<'a'. It rna}' be a..umedthat relali"ely ,apld miXing OCCurs in the recei"inll wat.r ,'olum. or thaIequilibrium is achlC"ed OtherwIse flow cha'acte"$tics can be mod.lled ifhydrological IDformation i' .."ailable.
Ri,".r models are based on a one.d,,,,,,n,,onal .,quation accounting fordiffusion (mixinll) and advection (ma,'.m.nt .",h ",ate, rna..). accounting fo'",urces and sinks including sedim.nt IOt.raetion,. Ah.rnalively. the ri".r may be
£X{JQSUF~ ESIImari(»t 115
con"drred 10 be a series ofdiscrete compamnenl>. or an empirical funcuon maybe found relaung lhe concentralion of the oubslance ""lh do",nmeam distancefrom lhe ",urces (CEC 1979).
Lake modeb employ .imilar hydrographic and se<hmtolauon data, 1\ i$u$ualll' possIble 10 define lhe lumo'", I,me of ",ater in lhe lake and lhe effecti"eresOdence lime of Ihe di>soh'ed ch.m;caL Dttpec lakes mal requ"e su,alifiedmodel. "'lh seasonal mixing of Ihe la)'ers.
EIIUa"•• h"e a number of un,que fealUres. notably lhe cbange in .... linilyfrom lhe river 10 Ihe sea and Ihe lidal inft ...nces. uluanes are >edimrnl·richa..... Companmem modelhng rna)' be pos>ibk foe "'a,er """on., balanc,nginput and OUlftO'" fTom .pec,fi<; areu.
The ,impl.., model. for coastal ..a. are again compa"ment model•. "'he.. avolume of a>sume<! unifonn m",ng i$ defined, The >ed,menlat'On and lIdalinftu""""," are 'ariable and the local and large·"",le "'at'" mo",memo are oile.p«iftc
The deg= of interaclion ofchemlCaloubslances wilh >ed'men.. i'lndicated byIhe ,'.lue of the ..d,menl-waler distnbnlion coefficienL K-.. defined as lhe ralioof lhe concentralion of lbe chem"'al in the >edimen.. 10 lhal in lhe "'alerChem;cal. are ad"',bed to ou,pended >ed,menl1 and to bed >edunenlS, The.. a..man)' r.ctors "hich afT.., the rale of attachment 10. Or relus<: f'om. >edimen!>'uch a, lhe pH of lhe "'aler and ..hnily,
An importanl inpul of chemicals 10 aqualic 'ystem, io ourface run·off from",rI. 10 lakes and Slream. and do,.-n,,'aro penelration lhrough ""I. 10 grou-..d,.-ater, Do,.-n,,'aro mlgrallon ofchem",alo in >Oilo i. due 10 kachmg "'Ih ra,nfallor 'mga"on ",aler mpUI. faCIO" afTee-hng the movemenl include",lubihly. ",ilpropertl.. including polentlal for ad"''l'lion 10 "'il minerab or organic malerial.and ,.-aler Inftux, ChemICalo ",Iuble ,n ",aler and pontll' adsorbed by ooilcomponen15 a.. lhe m"'l mobile Do...-n"'ard mn"emenl in "'aler OCCUrs Inpreference 10 .urface run_ofT unhllhe ourface layer is .... Iurale<!.
M'grauon nf chem,cal. lhrnugh lh. ",il column can b< Tejlr-esenled bylran.f.... bet,.-een companrnenl1 of "",)'ing drplh (CEC. 1979). MClhod' ofmodelling Ihe OC'l'I'on prOCtSSCS <X>::umng ,n ""I> have 'ottn rn,,,,,,ed by Tra"isand Elni'" (1981). Modelo of mo"emenl of cbemical. in run-<lfT requuecon,idera"on of the properll.. of lhe ch.m;cal and soil. th. hj'd'ology and ",,110$$, Modd. describing pe.ticide dynamics to ooil' ba'e been discussed byCra"ford and Donig,an (1973) and Rao and J...~p (1982),
J.J Food--chaift ud Eco.ystem ,'lodel.
T,aMfe" along lerreslrial and aqualic food chaino a.. represenled a, compartmental ""'lU""""'" ,,'ith lranofer fac'or> 0' concenlrauon ra,i", ."p.....ing lhe,elallonsh,ps at >leady >tate These lI.1'e been partic~lifl) d""doped and applied10 radionuclide en"irOnmenlal behaviour (UNSCEAR. 1977; CEC. 1979). for
116 M~11wJs for UmtwMg Ru/l: of O'emical InjuTY
example, soil-pasture gra"-COlli-milk- man. The delails of lhe model dependon Ib~ ~v~;I~bilitl of d~t~. The aqu.lic mod~ls ofi~n proe«d in one $lep from.....1.,. 10 aqU.tlC organlSm ....,lb u$t of lh~ co~nlralion factor, If Ib~
conc~'Illr'lion factors baH not been m~uured. lhert .rt 'U~lion$ for<slimalinl tbem from chemical propenl« ($OlubililY. octllnOI-"'~I~r partitioncodlici~nt) ~nd lhe ph)'.iolon of tb~ oraani$m (Neely. 1979)
linea' .y.t~mmodel. rna)' .1$0 be formul.'«Ilo describe food-<:b~in lran.f~rs.
Th~ int~rlinking lramf~r ral~ con$lanlS mun be ,,·alualed. The $Olu'ion lh~n
,;,.... !he conccnlrallon ,'.nallon.u' fun<lIon oflim~ (Boolh and K~)'~. 1971).Ecosysl~m lb~ory. iO"ol"ing examin.lion of alllh~ aspcct. ohlrtS$. $tabilllY.
~nergy Au'«. nu,rient cycles.•arbon metaboli$m and lrophic $1ru<:tUrt. IS belnlapplied '0 '$$C$$menl of cbem...l pollul.nl behaviour, The $l~p$ in modelformulalion and impl~mentalion ba,'~ been discussed by $t'eral aUlbon (c_l_Goodall. 1972, 1974: Reich!c ., oJ.. 1913: Wood. 1914: S"ranzman. 1979).lnformalion ",'ailabilil) i$ tb~ major Iimitinl faetor in dirtCl .pplicatlon. ofI''le·scale ecm)'<lem mod~I$.
3,4 E.'·lron.....'.1 \!ollilor;nl
E'po$urt of oraan"m. and man 10 cbcm'<:al$ in the en"room~m can be~"alu'led "'lib mOSl c~nalllll' by direcl m~..urm;enl of co"""nlrali"o••ndAu.... pro"ided tbc $On"",,,y of method. ,s adequ.at~. R.th~r ~Xl~nsiv~ andcomprtben,iv~me.,urements ....ould be de"rabl~. but Iimiled reseu.... me.nthat $<1""1,,'e mca$urt=t. mU$' be m.d~ '0 provid~ essenll.l information,Moniloring .nd mod~llinl pro....amm~' .r~ mutu.lIy .upponi,·~. Modelling$Iudi...u~t lb<: more Imponanl I)--pes of me..ur~ment and ~Xlend lhemel$urement resull$. Monitoring prOJ1'lIDIDeS provide ba.ic dal. for input 10.nd ,,,lid.lIon of modelling cffons
E....nti.l fealur~.ofmonilorinl programmco indud~ $it~ $01<C1ion, ...mplinlme,bod•. ba.1C mea.uremenl$ 10 be unden.ken. frt:q".ncy of meUu""""nl andim~rprrting pro«<!ure., Eilher ind~, or r.ndom sampling rna)' be con,id~red
appropn..e (NAS. 1915). In mde. samphng. judgm<nl$ of r~Prr$Cnl.t,,·~n~..• nd ....ilabilil) predon"nal~ in lbe $Ote<tion of rnal~rial._ It 1$ ...umc:d lhalindu mat~rial.m.)' rell"", 'ho ~,,~l. in lb<: broad~r popul.t,on of inl~rcsland theinl~rrelaled I~,'~ls in ..sociated compartm~nl$. An eumple " tbe $01""lion of a"ngk speei.. offi.h '0 reprr$Cn,.1l fish or perh'p$.11 aquatic biolll R.ndomsamphna IS &Cnerall~ .pproprial~ only in more hm,ted monllonng programmes,Exampl.. ar~ .nal)'.i. of "arlouS food. 10 d~t~rmin~ di~tary intake of particular$ub!;lanc.. and .re. sampli"l of $0,1. to d~l~rmine ..'~raa~ co"""nlral;"n.(NAS. 1975)_ Usu.H)·. $Om< form of "ra"fi«l ...mphnl i. undertaken. ,,-hichgives mort atl~nlion 10 lhe more importanl il~rm or r~aion, 10 be In'....ugaled.
The mea'urtmeon In momtonng programrn., rna", be .ppropria'~ '0 lh~
Exposur~ EsrlMan"" 117
purpo"". rcl\""l spalial and tcmporal "analions. provIde delail. of phy,ical andcl>cmical forms and be reported "'ilh relevanl paramelCr1 for olhcr m<dlapropeni.... An lmeValed approach 10 monllo"nll is required-a,socialed mulli·media and mull i-suMlance analy"s--Io ..'al uale lhe beha''iour ofcl>cm ical' andlheir inletaeuon. in lhe env;ronmenl.
Monllo"nll dala 'hould indlCalc Il>c chanses ,,'ilh lime ofconcenlralions andmedia propcru... 10 "'labh,h "hclhcr eqUlhbnum condlllon, ha"c been rcachedor 10 rdl«ll,-cnd' In a""umulallon or d,m,nulion oflhe amounlSc>f cl>cmical. ordellradalion producu, It i. imporlanl lhal nOI only immediale .."",ur,,, l>cdetcrmmed, but Ihc build-up of chemIcal ,uh<lances,n soil. ..,d,mcn" or olher.inks be monitored and lon,.term potcn'ia] tran.fer 10 organ;'m, and man be....lualed.
4 MITABOLIC BEHAVIOJ..:R
Melaboltc model. arc u..,d 10 de"'''be the rclalion,h,p, belween Intah ofchemICal ,uMlances and theit aMOfJ"ic>n, dillnbUlion. ftlenlion. tran,form'alion and excm;on by blolotical orpni,ms, The model' may be useful inrelaung inlak.. 10 measured concentralions in body fiuids.•uch as blood andurine. Ho"'ew" thei, prima,y u.. IS 10 ..limale lbe e."",ur.. to cmical organ•.lhal i.. tho.. "hlCh aeeumulate lhe hl",",t concenlra"on, or are Ihc me",sen",",'e to damage or dy,funcllon.
As In ,eneral modelling. time-independenl or time-dependent melabolicmodel' may be u<c<J. Al "eady Slatc. Ihe concenuation faclo~ give simpleexp..."ion of Ihe dis"",ilion of inlake amountS. The>< are rali", of IheconcentratIon. of chem.cal .ubsta...... in I..... orpm'm and in lhe intakeamOunlS, h may be unrealistic 10 a..ume 'hat lbe mea'u.........nlS are made alstcady '\ale. particularly iflhere are long-term lran,fe.. or ",de ,·a"abihll"'. The....ul\$ apply 10 lbe part.cular cnvlronm<n,al rondi'iom. but "ider applicabilitycan usuall}' be a..umed for .....onably comparable ci,--cumllancn.
Compartmenl models of more Or Ie.. delail and compl..ity are u<c<J 10descnhc the metabolic proce.ssini of cl>cmical•. The compartments mayrep.....nl the phySIcal structure c>f ,he c>rpnlSm. .such as pnmary organ.s andli..u«. or lhey may represenl lhe ,'aMu. components of relenuon. Retenlionequalion. ""nsistlni c>f a sen« ofexponemiallerm.s are "er)' useful in reflecllng,,,'crall me'aholi.m. The parameters are determined from e.cmion me:asu...•men!> or frc>m analysis of li..ue con,enl al nric>us I1m« aftcr an amount hasbeen admmlSlered, The half-times of retention and the effcc""e mean r..;dell<Xlime. of Ihe chem,oal in the c>rgan;sm can be determined.
Mooels ha'e ~o dncloped which renee! phj'sloIOilC'l1 Ploces~ followtniintake, lbese Include a lung model and a model fc>r 'he pSlroinlcsunal tract. The
lung model, fonnulated bl' tile Tali:: Group on lung Dynamics (ICRP. 1919).di"ide> the respiratory 'l.t~m inlO nasoplla,)'ng~al, tr;acheobronchial andpulmonary compartments, Depo,ition ofinhalM panicle. in the compartmentsdepends on paf1,d~ "z~. Clearan« from 'he compar'ments is by mocociliarytran.for 10 Ih~ ga"roinleSllnallraCl or ab""rplion in blood. Th~ mod.l g,,'eslhepalhway's and dearanc~ rales for ....eral cia.... of paniele solubililies. Thedas... ofcompound, are designaled D. W. and Y for clearance limes from Ihepulmona')' region of lhe order of day•. "'eeks or )'ears. For the amOuntSab'orbed inlo blood. further assumplion, can be made regarding Ihe di.tribulionof the chemiealsubslance 10 organs or 10 unetion, The ICRP lung model is v~ry
w,dely used.The beha..'iour of ingested malerial. can be dc>enbed by a phy.iological model
.uch a, th~ on~ b}' E"e (1906), "'hieh "'as de"eloped for purpo... ofradll'iond0'5,mel')', The residence time of ,nge.tM material ,n each «ction of thega.tromteshnal "act is spec,liM, For radionuclid... radia'ion do..s are rt«"edduring th~.. period,. For ch~mical 'ubstanee•. Ihe passage limes are I~ss
imponant than lhe fraClional amounl absorbed ,nto ~x,,~llular fluid•.Summaries ofabsorpllon valu~, and olheT metabolic dala for chemical elem~ntsare g,ven b) tCRP (1979),
Mullicompanment models ha." been formuLll~d 10rep~nl Ih~ melaboli.mof .pecific chemical substance•. fot ~umpl. an eight companment metabolicmodel for cadmium (Kjell.,rom and Nordberg. 1978) or a Ii"e compartmentmod~1 for I~ad (lkrnard, 1977). R~v,ew. of ,hi. and olher a.pects of themoddling procedures .re gi"en bl Gehrins ., 01. (1976). WHO (1978). andCamn~r., ai, (1979)
4.2 Biologic.1 MonHorina:
Blolog,cal monltonng IS Ih~ uammallon of organism. to eSlimat~ en"iron"mentall.""ls and or effects of pollutants, Organi,ms accumulat~ or respond 10environmenlal .ullstanee, and are frequ~n'l)' """""~ indicalors of the pre..nceor effeel> of Ihese .ubs'ances.
The biolog,cal sample. ""c1ud~ plan,s and ammals from the region of interesland from b;acksround areas. Mo" oflen a,...<ed aro the 'pec,es d..'~"ity.ahundance. p,oducllwy and b,omass. Funetlonal variable•. ~uch a. carbonfi~ation. may also be monitored, In ""me cases. auenlion i' focused on key orcritical .pecies "ilh the assumplion that assocUlled 'pecios will be affecl.d inp,oponion. Community struc,ural analyses invol"e CounlS of specie. presentand individual> per .pecies. Because of the int~rdependent system of speciesWIthin ecos)'st~ms. ~ffecl$ on one pan rna) ultimately affecl lhe ""hole
Often implied in biolosical monitoring i' Ih~ sampling and anall'~i~ of bodylIuid. and tissues of man. Blood. urine. hair and faeces are mosl easily obtainedThese result, 3'''0 ind"eel indicauon, ofaccumulation of ,ubstances ,n the body
£JCp<JSIlU Esrimmi()ll 119
and point 10 altered fuocl;Onin! or other dfect" Ti..ue loample. may al>o beobtained, primarily at autopsy, for dire<t analY'i. of chemical content or forevidence of damage.
The ....ull5 of blolop:al monilorin! rna}' be u>cd ,,'ith the rntlabolic model,"hich descnbe the proce>"ns of matonal' by orpnism•. l1>e>e includeaMorpuon facIo" for ,p«,ftc Intake mod"" and forms and the d"lrihuuon andretention kinetics of the cbemical. In Ihe body, Either dynamic model. or .teady·>late roncontralion facWf me..urement. may be "'ailable
Sp«ial prIXaution, mu.t be taken tn lbe loamphns and analysis of bloloS",almateflal'. The le"el. ofchemical 'Ubslance5 10 be inv""tis'ted ma}' be qui" low.and care mu51 be taken to ,,'oK! contaminalion from >amplinl equipment.
The dlflicul".. in obtllnlns accur". anolyt;cal ....ul" for biolollCal malerial.ha"e .Iimulated an inle....l in collaborati'-' 51OOi"". Intef1aborawry' comport50n,ha,'e~ und.rtaken. but t"r ....ull< of tl\e$e are orten qUl1e di...ppointlnl.•howins wide difference> e"en for quite common mea>uremenu. fOf eumplelead. cadmium and mercury' in blood. urine and v.-ater m onc particularInte"",mpari50n (Lauwe'Y' no/.. 1975). Tho need for mict anal}'lical qualitycontrol ha. been frequently pointed out (see for eumple WHO. 1979),
An internat;onal pfolramme of biolotical monitorin, has been iniliated byWHO and UNEP'Oa>5eS$ human .XposU.... IO ..leCle<!to.ic polluanl5. In th"project the \eo.-.l, of lead and cadmium in blood. cadmIum In kidne}' cortex andcertam orpnochlorin. compound. ,n brea.1 mIlk are he,nl determIned m..leete<! population .....,.nl' in 10-12 countries in differenl part, of the world(Slorach. 19S2; fribe,. and Vahter. 1'183).
R""ulu from bioloJical monitorin! prozramm.. may' be u>cd directly' inasses,inl exposur.. of receptors to chemIcal .ubsances, Th.se measurements.hov.-e"er. do n01 provide .,5OCiat;on. "'lth the indi"idual 5OU.... of e'posure.,and th.refore ....ult. from .och studies muSt be com:lated "'jth the resull5 ofe",,,onrnental monitoring proll:ramme> and cs-aluation' of the receptor l0cation' and lICli"itl' pattern" further consideration' of b;olo&lCll monitorins ofmelal' and other compound. ha"e been I,,'on by NAS (1975). Berlin.r oJ, (1978)and Calm, (1979).
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