Using the current Brazilian value for the
biological exposure limit applied to blood lead
level as a lead poisoning diagnostic criterion
A utilizaç ão d o atual limite b rasile iro d e to le rânc ia
b io ló g ic a d a p lumb e mia c o mo e le me nto
d iag nó stic o no saturnismo
1 Departam en to de Saú de Pú blica, Facu ld ad e d e Med icin a d e Botu catu , Un iversid ad e Estad u al Pau lista.
C.P. 543, Botu catu , SP 18618-970, Braz il. cord eiro@fm b.u n esp.br
Abst ract In gen eral, biological ex p osu re lim its are on ly u sed for th e p rom otion an d p reserva-tion of w ork ers’ h ealth an d are n ot ap p lied for d iagn ostic p u rp oses. How ever, th e issu e is con tro-versial for certain typ es of occu p ation al p oison in g. Th is p ap er p rop oses th e u tilization of biolog-ical exp osu re lim its cu rren tly ap p lied to blood lead levels in Braz il as an im p ortan t criterion for d iagn osin g occu p ation al lead p oison in g. Th e au th or argu es th at con trary to th e trad ition al clin -ical criterion , on e sh ou ld d eal w ith th e d iagn ostic p roblem of lead p oison in g from an ep id em io-logical p ersp ective, u sin g th e cu rren t Brazilian valu e for th e bioio-logical exp osu re lim it ap p lied to blood lead level as an in d icator of h igh relative risk .
Key words Lead ; Lead Poison in g; Risk ; Biological Exp osu re Lim it; Occu p ation al Health
Resumo Tra d icion a lm en t e, os lim it es d e t olerâ n cia biológica sã o u t iliz a d os ex clu siv a m en t e p ara a p rom oção e a p reservação d a saú d e d os trabalh ad ores, n ão sen d o ap licad os com fin s d iag-n óst icos. Eiag-n t ret aiag-n t o, com relação a algu m as iiag-n t ox icações p rofissioiag-n ais, o assu iag-n t o é p olêm ico. N est e a rt igo, d efen d e- se a u t iliz a çã o d o lim it e d e t olerâ n cia a p lica d o a t u a lm en t e n o Bra sil à p lu m bem ia com o u m critério im p ortan te p ara a realiz ação d o d iagn óstico d a in toxicação p ro-fission al p elo ch u m bo. Argu m en ta-se qu e, em op osição ao trad icion al critério clín ico, d ev e-se abord ar o p roblem a d o d iagn óstico d a in toxicação p elo ch u m bo sob u m p on to d e vista ep id em i-ológico, u t iliz an d o-se o at u al v alor d o lim it e d e t olerân cia p ara a p lu m bem ia com o u m m ar-cad or d e risco relativo sign ificativam en te au m en tad o.
Palavras-chave Ch u m b o; Sa t u rn ism o; Risco; Lim it e d e Tolerâ n cia Biológica ; Sa ú d e Ocu p a -cion al
Introduction
Sin ce th e con solid ation of In tern al Med icin e as th e m ed ica l p ra ctice d evo ted to cu rin g in d i-vid u als, estab lish in g d iagn ostic criteria h as al-ways b een a con troversial issu e. Pu b lic Health – an d p articu larly Ep id em iology – by takin g th e clin ica l d efin itio n o f a ca se a n d exten d in g it to th e collective level, h ave in trod u ced greater com p lexity in to th e issu e. In th e field of Occu -p ation al Health , th is d ifficu lty is fu rth er aggrava ted b y th e fa ct th a t th e d iscu ssio n o f rela -tio n sh ip s b etween wo rk a n d h ea lth a re m o re p erm eab le to econ om ic in terests an d th e p olit-ical gam e.
Th ere is a cu rren t d eb a te over th e co n ve -n ie-n ce o f u si-n g th e b io lo gica l exp o su re lim it (BEL) a s a n im p o r ta n t d ia gn o stic elem en t fo r som e typ es of occu p ation al p oison in g, in clu d -in g occu p ation al lead p oison -in g or p lu m b ism . Th is d iscu ssion is p articu larly relevan t in view o f th e m a gn itu d e in th e d istr ib u tio n o f su ch d isea ses in Bra zil a n d th e im p lica tio n s o f in -corp oratin g BEL in to th e d iagn osis of occu p a-tion al p oison in g for p reven tive an d even cu ra-tive m easu res.
In a recen t literatu re review, Cord eiro & Lim a Filh o (1995) an alyzed a large n u Lim b er of in -d ep en -d en t in tern a tio n a l stu -d ies p o in tin g to th e occu rren ce of cen tral an d p erip h eral n eu -rological d isord ers in workers exp osed to lead , with b iological exp osu re an d effect in d ices well b elow th e b io lo gica l exp o su re lim its a d o p ted by th e Bra zilia n Min istry o f La b o r. La ter, Co d eiro et a l.(in p ress) d em on stra ted th e occu r-ren ce o f p erip h era l n eu ro lo gica l d iso rd ers in wo rkers a t a b a tter y fa cto r y in Bra zil, wh o se b lood lead levels d u rin g th e two years p rior to th e stu d y h ad con sisten tly b een b elow th e safe lim its esta b lish ed b y th e Min istr y o f La b o r. Su ch stu d ies h a ve reign ited th e co n troversy over d iagn ostic criteria u sed for ch aracterizin g occu p ation al lead p oison in g in Brazil.
Th e p u rp o se o f th is stu d y is to co n tr ib u te to th is d iscu ssio n b y d efen d in g th e va lid ity o f u sin g th e cu rren t BEL ap p lied to occu p ation al lead p oison in g as on e of th e relevan t d iagn os-tic elem en ts for lead p oison in g in Brazil.
The basis for biological exposure limits
Th e Am erica n Co n feren ce o f Govern m en ta l In d u stria l Hygien ists (1959) d efin ed o ccu p a -tion al h ygien e as “th e scien ce an d art d evoted to th e recogn ition , assessm en t, an d con trol of am b ien t risks an d stress origin atin g from or in th e workp lace, wh ich can cau se d isease, d am
-a ge to h e-a lth -a n d well-b ein g, -a n d sign ific-a n t d iscom fort an d in efficien cy am on g workers or m em b ers of a com m u n ity”. Della Rosa & Colacciop p o (1994) u n d erscore th a t th e term occu -p ation al h ygien e, as com -p ared to in d u strial h ygien e or lab or h yygien e, b etter reflects th e con -ten t an d ob jectives of p reven tin g work-related in ju ry a n d is cu rren tly recom m en d ed by va ri-ou s organ ization s in th e Eu rop ean Com m u n ity an d th e World Health Organ ization .
In clu d ed in th e ra n ge o f o ccu p a tio n a l h y-gien e is a m b ien t m o n ito rin g, wh ich wa s d efi-n ed by th e joiefi-n t com m ittee set u p by th e Eu ro-p ean Com m u n ity Com m ission (ECC), Occu ro-p a-tio n a l Sa fety a n d Hea lth Ad m in istra a-tio n (OS-H A), a n d Na tio n a l In stitu te fo r Occu p a tio n a l Sa fety a n d Hea lth (NIOSH ) a s th e “m ea su rem en t an d assessrem en t of agen ts in th e en viron -m en t in o rd er to esti-m a te a -m b ien t exp o su re a n d risk to h ea lth b y co m p a riso n o f resu lts to ap p rop riate referen ces” (Berlin et al., 1982).
In a d d itio n to a m b ien t m o n ito rin g, b io lo -gical m on itorin g is recom m en d ed . Th e latter is d efin ed by th e jo in t CCE/ NIOSH / OSH A co m -m ittee a s “th e -m ea su re-m en t a n d a ssess-m en t of ch em ical agen ts or th eir b iological b yp rod -u cts in tiss-u es, secretion s, excretion s, exh aled a ir, o r so m e co m b in a tio n th ereo f, to estim a te th e exp osu re or h ea lth risk a s com p a red to a n ap p rop riate referen ce” (Berlin et al., 1982). Bo lBo gica l m Bo n itBo rin g a im s tBo estim a te th e b ioavailab le am ou n t of th e ch em ical agen t, com p lem en tin g a m b ien t a ssessm en t a n d p rovid -in g a m ore solid b asis for d evelop -in g allowab le lim its rela ted to en viro n m en ta l p o llu tio n , in ad d ition to estab lish in g n orm al referen ce val-u e in tervals for th e b iological exp osval-u re in d ices (Della Rosa et al., 1991).
Bio lo gica l m o n ito rin g m ea su res a n d a cco m p a n ies b io lo gica l in d ices, d efin ed in Ap -p en d ix II to Regu la to r y Directive No7 o f th e Brazilian Min istry of Lab or as “an y an d all en -d ogen ou s or exogen ou s su b stan ce in th e b o-d y, th e m easu rem en t of wh ich in b od ily flu id s, tis-su es, an d / or exh aled air assesses th e in ten sity of occu p a tion a l exp osu re to ch em ica l a gen ts” (MT, 1988).
Based on kn owled ge of th e relation sh ip b e-tween exp osu re, in tern al d ose, an d effect, b io-logical exp osu re lim its (BEL) are p rop osed , th e con cep t of wh ich wa s in trod u ced in to Bra zil’s Con solid ated Lab or Legislation (Con solid ação d as Leis d e Trabalh o – CLT ), Articles 189 a n d 192 (Brasil, 1978), an d wh ich ap p ears in d etail in Ap p en d ix II to Regu la to ry Directive No7 a s
Th u s, keep in g th e lead -sen sitive b iological in d ices b elow th e esta b lish ed BEL wo u ld en -su re p reservation of th e h ealth of th e exp osed in d ivid u al (Siqu eira, 1992).
In Brazil, th e estab lish ed BEL for variou s in -ju ries, in clu d in g exp o su re to lea d , h a ve co n s-titu ted a legal n orm sin ce 1983 (MT, 1988), re-cen tly exten d ed (in 1994) u n d er Directive 24/ 94, a lso p erta in in g to th e Min istr y o f La b o r (MT, 1994).
The controversy
Utilization of b iological exp osu re as a d iagn os-tic elem en t fo r lea d p o iso n in g is a co n trover-sial issu e in th e literatu re. Som e au th ors stress th at su ch lim its can n ot b e taken as figu res th at clearly d em arcate b etween safe an d u n safe ex-p osu re; rath er, th ey sh ou ld b e seen as warn in g levels p rop osed on th e b asis of cu rren t kn owl-ed ge con cern in g th e relation sh ip b etween exp osu re an d resexp on se (Della Rosa &amexp; Colaccioexp -p o, 1994; Siqu eira, 1992; Della Rosa et al., 1991; Della Ro sa & Siq u eira , 1989). To a grea ter o r lesser d egree, su ch au th ors p lay d own th e im -p o rta n ce o f BEL a s a d ia gn o stic a id fo r lea d p o iso n in g, wh ich in th eir o p in io n sh o u ld b e estab lish ed strictly on th e b asis of clin ical p a-ram eters, i.e., b ased on ob servation s of sign s of th e d isease. Neverth eless, som e au th ors (Bu s-ch in elli, 1987; Colom b i et al., 1989; Bu ss-ch in elli & Kato, 1989; Rigotto, 1989, 1994) h igh ligh t th e u tiliza tio n o f BEL a s a d ia gn o stic reso u rce, a m o n gst o th er u ses. Co lo m b i et a l. (1989) stress th e u se of BEL as a tool to d etect early b i-o li-o gica l effects. Rigi-o tti-o (1989, 1994) rep i-o rts th at am on g th e d iagn ostic criteria for lead p oi-so n in g is th e p resen ce o f a d o se a n d / o r effect in d ex a b ove th e BEL, stressin g th a t clin ical sign s an d sym ptom s ch aracteristic of plu m bism m ay or m ay n ot be p resen t.Bu sch in elli (1987) an d Bu sch in elli & Kato (1989) state th at b lood lea d levels a n d / or ALAU for a worker exp osed to lea d a n d h igh er th a n th e cu rren tly esta b -lish ed BEL in d icate th at th e worker is sick an d th a t m ea su res sh o u ld b e ta ken to rem ove h im / h er from exp osu re, in ad d ition to p rovid in g trea tm en t a n d a ssessm en t o f p o ssib le se -qu elae. In p ractice, th is is th e con d u ct officially reco m m en d ed b y govern m en t-ru n wo rkers’ h ealth services (INAMPS, 1986; INSS, 1993).
Discussion
I a gree with th e first gro u p o f a u th o rs, wh o m ain tain th at th e BEL d o n ot h ave th e p ower to d ich o to m o u sly cla ssify exp o su re a s sa fe o r u n safe. I also agree wh en th ey h igh ligh t th at a b iological in d ex ju st b elow or ab ove th e resp ec-tive BEL d o es n o t, p er se, ru le o u t a d ia gn o sis o f lea d p o iso n in g, b eca u se th e kid n eys, b o n e m arrow, an d n eu rological circu its are u n aware of th e valu es estab lish ed for th em . From a clin ical p oin t of view, i.e., ap p roach in g an in d ivid -u a l ca se, th e d isea se sh o -u ld b e d ia gn o sed o n th e b asis of clearly estab lish ed sign s an d sym p -tom s. Hu m an b od ies are n ot stan d ard ized m ach in es resp on d in g in stan d ard fash ion to stan -d ar-d exp osu res.
Neverth eless, th e clin ical ap p roach to b oth lead p oison in g an d d iseases as a wh ole is in su f-ficien t to co n tro l th em . Occu p a tio n a l d isea se on ly rarely occu rs as an isolated case.
On e m u st seek a d ia gn o stic cr iterio n th a t in stru m en ta lizes p u b lic h ea lth m ea su res to con trol occu p ation al p oison in g. In th is sen se, I fin d th e p oin t of view d efen d ed b y th e secon d grou p of au th ors q u ite ap p ealin g, valu in g BEL a s o n e o f th e d ia gn o stic cr iteria fo r lea d p o i-son in g.
By p resu p p o sin g th e va lid ity o f gen era liz-in g th e an alysis by Cord eiro et al. (liz-in p ress) for Brazilian workers as a wh ole, th e p red ictive val-u e o f a b lo o d lea d level eq val-u a l to 60 µ g/ d l is so m e 37% in Bra zil. Th a t is, given th a t a n e x-p osed worker h as a b lood lead level equ al to 60 µ g/ d l, th e p ro b a b ility th a t h e o r sh e is sick is so m e 0.37, wit h t h e clin ica l d ia gn o sis b a sed o n ly o n th e p erip h era l n eu ro lo gica l d a m a ge cau sed by lead . Kn owin g th at d am age to h igh er n eu ro lo gica l fu n ctio n s b egin s a t a n exp o su re th resh old well b elow th at at wh ich th e first p e-rip h era l m a n ifesta tio n s b egin to b e d etected (Baker et al., 1984; Baker et al., 1985), it wou ld b e co n sisten t to su p p o se th a t th is p red ict ive valu e is u n d erestim ated .
Th is u n d erestim ation is fu rth er aggravated b y th e fa ct th a t th e p red ictive va lu e h a s b een calcu lated on th e b asis of an exp osed grou p of workers lim ited to th ose wh o d o n ot con su m e (an d h ave n ever con su m ed ) alcoh ol, h ave n ev-er b een exp o sed to o rga n ic so lven ts o r p esti-cid es, an d h ave n o clin ical h istory of n eu rolog-ica l d isea se o r rep ercu ssio n s, a ll o f wh ich a re kn own to b e syn ergistic factors with lead in af-fectin g th e n ervou s system .
wh ich can b e term ed statistical, ep id em iologi-ca l, a n d clin iiologi-ca l. Th e first, essen tia lly sta tistical, is b ased on th e d istrib u tion of th e frequ en cy o f a rteria l p ressu re in a given stu d y p o p u la tio n , esta b lish in g a s h yp er ten sive th o se in -d ivi-d u a ls with a rteria l p ressu re h igh er th a n som eth in g close to th e m ean p lu s two stan d ard d eviation s. Th e secon d ap p roxim ation , valu in g ep id em io lo gica l a sp ects, is b a sed o n th e co n -cep t of relative risk to d efin e th e lim its of arter-ial h yp erten sion . Accord in g to th is ap p roxim a-tio n , o n e ca n d efin e a s th e cu to ff in a given p op u lation th e p ressu re valu es wh ere th ere b e-gin s to b e a sign ifica n t in crea se in th e risk o f a p p ea rin g sign s a n d sym p to m s o f th e d isea se (Co rd eiro, 1991; Co rd eiro et a l., 1993), i.e., wh en th e relative risk for th e d isease b egin s. Fi-n ally, th e th ird way of coFi-n cep tu aliziFi-n g arterial h yp erten sio n em p h a sizes clin ica l a sp ects b y va lu in g th e co st/ b en efit weigh t o f p h a rm a co logical treatm en t for th e h yp erten sive in d ivid -u al. Th at is, it attem p ts to estab lish as lim its for h yp erten sion th e p ressu re valu es at wh ich th e b en efit to th e h yp erten sive in d ivid u al p rovid ed by trea tm en t ou tweigh s th e sid e effects of th e d ru gs u sed . Followin g su ch reason in g, Evan s & Rose (1971) d efin ed system ic arterial h yp erten -sion as “a level of arterial p ressu re ab ove wh ich th e d iagn osis an d treatm en t are m ore favorab le th an d an gerou s”.
If BEL sign a ls a level o f exp o su re a b ove wh ich th e risk for lead p oison in g in creases, as seen p reviou sly, its u se as a d iagn ostic criterion is essen tially th e sam e as th e secon d d iagn ostic criterion d escrib ed ab ove for arterial h yp erten -sion .
Th e NIOSH itself u n d ersto o d th e n eed fo r su ch a d ia gn o stic a p p ro a ch wh en it recen tly d efin ed lead p oison in g sim p ly as “a con cen tra-tion of lead in wh ole b lood exceed in g 50 µ g/ d l” (Nation al In stitu te for Occu p ation al Safety an d Health , 1992).
In th is sen se, th e d ia gn o stic u se o f BEL in th e con text d escrib ed ab ove is logically d efen -sib le a n d wid ely u sed in o th er a rea s o f m ed icin e; in m y o p in io n , its co n so lid a tio n a s ro u tin e p ra ctice in o ccu p a tio n a l h ea lth is a n im -p ortan t -p olicy issu e. Th rou gh its u se, th e sco-p e o f p reven tive m ea su res fo r o ccu p a tio n a l d is-eases will certain ly b e b road en ed , b ased on an u n d erstan d in g b etween in d u stry an d workers a t a m o re fa vo ra b le th resh o ld fo r p ro m o tin g th e latter’s h ealth .
word s (an d takin g wh at I b elieve is a con serva-tive stan ce), every secon d worker with a b lood lead level equ al to th e b iological exp osu re lim it is sick an d th e first is ab ou t to b ecom e sick.
In a situ ation lik e th is, to req u ire th a t lea d p oison in g b e d iagn osed exclu sively on th e b a-sis o f d o cu m en ted b io lo gica l a ltera tio n s is a kin d o f strictn ess th a t wo u ld b e la u d a b le if it d id n o t ca u se a b ru ta l u n d errep o rtin g o f lea d p o iso n in g, a s u n fo rtu n a tely it d o es in o u r cou n try. After all, wh at Brazilian com p an y n ow a llows its wo rkers a ccess to p erio d ic elec-tro n eu ro gra p h ic a n d n eu ro b eh a vio ra l testin g to ru le ou t th e p ossib ility of p oison in g?
Th u s, I fin d it q u ite a p p ea lin g to u se th e
cu rren tBEL for b lood lead level in an ep id em i-ological ap p roach as an im p ortan t criterion for estab lish in g th e d iagn osis of lead p oison in g. In essen ce, su ch a p roced u re is rou tin e for in n u -m era b le o th er d isea ses. As exa -m p les I wo u ld cite two of th e greatest p u b lic h ealth p rob lem s in th e field o f ch ro n ic/ d egen era tive d isea ses: system ic a r teria l h yp er ten sio n a n d d ia b etes m ellitu s.
Th e Fifth Rep ort of th e Join t Nation al Com -m ittee on th e Detection , Evalu ation , an d Treat-m en t of High Blood Pressu re d efin es systeTreat-m ic a rteria l h yp erten sio n in a d u lts over 18 yea rs of age as d iastolic arterial p ressu re greater th an o r eq u a l to 90m m H g a n d / o r systo lic a r teria l p ressu re grea ter th a n o r eq u a l to 140m m H g (Th e Join t Nation al Com m ittee, 1993), regard -less o f ren a l, retin a l, cereb ra l, ca rd iova scu la r, or an y oth er alteration s in a sp ecific in d ivid u al. Th is d o es n o t m ea n th a t th e la tter sh o u ld n o t b e exh au stively in vestigated an d con trolled in th e clin ical ap p roach to th e case. Wh at m akes clin ica l p ra ctice a fer ven t ch a llen ge is th a t in sp ite of th e ab ove, a d iastolic arterial p ressu re stab ilized at 85m m Hg d oes n ot in itself ru le ou t arterial h yp erten sion . For exam p le, su ch a lev-el m a y b e su fficien t to set o ff va scu la r a n d re-n al alteratiore-n s ire-n are-n ad u lt th at p reviou sly h ad a b aselin e d iastolic p ressu re of 60m m Hg.
Qu a lita tively, th e situ a tio n is th e sa m e fo r d iab etes m ellitu s, th e d iagn osis of wh ich is easily estab lish ed in th e p resen ce of an asym p to -m atic in d ivid u al with p ersisten tly h igh fastin g b lood su gar levels (Foster, 1983).
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