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### Revise d February , 1984 . 

## EPAAJBDOCKg L

TITLB : Teachers ' rating s o f children' s behaviou rinflatio n t o bloo d lea d levels . RUNNIN G HEAD : Children' s behaviou ran d bloo d lea d levels . AUTHORS : Willia m Yule* , Ph.D. , Marie^Ann e Urbanowicz* , M.Sc. , Richar d Lansdown * Ph.D. , an d Ia n B . Millar^ , M.D.

* Departmento f

Psychology , Universit y o f London , Institut e o f Psychiatry . + 

### Departmento f

Psychologica l Medicine , Th e Hospita l fo rSic k Children , Grea

tOrmon d Street , and , / Greenwich Healt h Distric t



# 2 LJ

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- l£fk>L- *- t>M**; 

# /W.

Request s fo r reprint s t o Dr . W . Yule , Institut e o f Psychiatry , D e Crespign

y Park, ' London , SE ^ 8AP , U.K .

•M l i



### NP. 3

ABSTRAC

T

Teacher s rate d th e behaviou ro f 16 6 childre n whos e bloo d lea d level s ha d previousl y bee n determined . Rating s wer e mad e o n th e Conner s Scale , th e Rutte rScal e B(2) , an d Needleman' s Scale . ; 

### Th e result s broadl y replicate d th e finding s o f Needleman : (1979 ) ;

: i n s o fa ra s the y indicat e arelationshi p betwee n difficultie s i n attentio n an

d increase d bloo d lea d level s ove rth e norma l rang e o f bloo d lea d values . "Hyperactivity " o n th e Rutte rand ' l4 

### Conners scale s were found t o b e significantl y relate d to/children' s bloo d lea d levels , independen to f chronologica l age . Socia l • ' factor s remai n uncontrolle d i n thi s pilo tstudy . 2 .P. 4



### 3 .
INTRODUCTIO

N I nrecen t years , ther e ha s bee na growin g concerntha t level s o f lea d absorptio

nmuc hlowe r tha

nthos e leadin

g t o lea d intoxicationma

y b e associated wit ha

nincreas e i nlearnin g difficultie s an

d behaviour problems , (DHSS , 1980) . Som e author s hav

e claimed particularl y tha t increase

d bloo d lea d concentration s ar e associated wit h"hyperactivity " (Balo he t al , 1975 ; Davi d e t al , 1972 , 1976 , 1977 , 1979 ) althoug hthi s ha s no t alway s beenfoun d (Ernhart , Landa an d Schell , 1981 ; Mila r e t al , 1981) . Other s hav e reported association s betweenincreased bod y lea d burdenan

d impairmen t i nattention(D e l a Burd e an

d Choate , 1975 ; Needlemane t al , 1979) . Give ntha t lea

d i s a know

nneurotoxi nan

d tha t i t i s wel l established that hig

hdose s caus e seriou s brai ndamage , the ni t i s plausibl e t o hypothesiz e tha t lowe r level s o f lea d exposur e ma

y caus e lesse r degree s o f damage , wit hmilde r o r mor e subtl e effect s o nneuropsychologica l functioning . Thi s plausibl e hypothesi s ha s provendifficul t t o investigate . Severa l recen t reviews hav e draw nattentiont

o a numbe r o f methodologica l problem s whichhav

e ariseninstudie s i nthi s are a (Rutter , 1980 ; DHSS , 1980 ; Needlemanan

d Landrigan , 1981 ; Yul e an d Rutter , 1984) . Firstly , there wa s th e proble

m o f selectionbia s insamplin g either , fro

m using clini c based sample s or becaus e o f hig hattritionrates . Secondly , ther e ar e associated problem s wit hth

e bod y burdeno f lead . Bloo d lea d level s reflec t onl y

recen t ingestio

no f lea

d an d fai l t

o indicat e pas t exposur e o r th e durationo f exposure . Thus , the y canno t differentiat e betwee n short-ter

m an d long-ter

m lea d intoxication . I ndevelopmenta l terms , th e timin g o f exposur e t

o toxin s ma

y b e a s importan t a s th e leve l o f th

e exposure . Th e quality o f bloo

d measuremen t ca

nb e problematica l (Vahter , 1982 ) an

d repeated testin

g i s highl y

desirable . Estimate s o f th e leve l o f lea d i nteet har e considered bette r indicator s -o f long-ter

m exposur e but , o f course , teethcanonl y b e analysed whe nthe y fal l ou t naturall y a t aroun

d 6 t o 7 years , anunfortunatel y earl y tim e fo r th e measuremen t o f intelligence , attainmen t an d neuropsychologica l attributes . Ther e i s som e evidenc e tha t childrenwh o donat e teethar e no t a rando m sampl e o f th e tota l population(Smithe t al , 1983) .P. 5

4 . Thirdly , th

e measure s o f psychologica l impairmen t i nman y studie s ar e weak , ofteninvolvin g inadequatel y

validated tests . To o often , large batterie s o f test s hav e bee nuse

d wit hinsufficien t car e take nin interpretin

g a fe w 'significant ' difference s whic hcoul d wel l b e attributed t

o chance . Fa r to

o fe w attempt s hav

e beenmad e t

o replicat e published studies . Fourthly , an d mos t importantly , fe w o f th e earl y studie s undertook adequat e statistica l analyse s t o contro l for th

e effect s o f possibl e confoundin g variables . Lea

d i s no t distributed randoml y

inth e population . Rather , there i s a substantia l overlap betweensocia l disadvantag e an d hig hleve l lea

d exposure . Independently , socia l disadvantag e ha s anadvers e influenc e o nchildren' s psychologica l developmen t (Rutter , 1983) . Thus , i f th e effect s o f lea

d ar e t

o b e assessed , i t i s essentia l t o tak e accoun t o f th

e non-lead effect s o f th e socia l disadvantag e wit hwhichlea d tends t

o b e associated . Fifthly , becaus e th e effect s o f lea

d ar e likel y

t o b e smal l an

d becaus e o f th e need t

o contro l fo

r confoundin

g variables , i t i s eviden t tha t quit e large sample s ar e essentia l i f statisticall y significan t difference s ar e t o b e identified . Sixthly , i f th e mai ninteres t i s i nth e effect s o f lea d exposur e i nth

e genera l population , i t i s vita l t o focu s o

nth e consequence s o f bloo d lea d level s belo

w 3 5 ug/lOOml , a s very fe w childre ninth

e U Knowaday s have level s abov e 3 5 inth

e absenc e o f exposur e t

o specia l hazards , mos t usuall y lea d inol d paint . Mos t o f th

e studie s o f lea

d an d children' s developmen t hav e beencross sectioned i ndesign , an d suffe r fro

m th e proble

m o f inferrin

g causation fro m correlation . Plac e o f living , income , race , materna l I Q an d th e quality o f th e care-givin

g environmen t have al l bee nfoun d t o relat e t o bloo d lea d level s - bu t the y als o relat e t

o children' s intelligenc e an d attainment . Multivariat e analyse s ar e required t o examine whethe r som e or al l o f th

e correlationbetweenlea d an d I Q i s due t

o th e fac t tha t bot hlea

d an d I Q themselve s ar e associated wit hothe r variables . Th e conceptua l an

d statistica l problem s involve

d indisentanglin

g thi s proble m ar e discussed mor e full y elsewher e (Yul e an d Rutter , 1984) . For th e presen t purposes , i t i s sufficien t t o not e tha t becaus e th eP. 6



### 5
. confoundin g variable s ar e themselve s interrelated , th e us e p f asingl e co-variat e ma

y substantiall y under-correc t fo r confoundin g effects ; wherea s th e us e o f

man y covariate s ru n th e ris k o f over-correctio n (Reichardt , 1979)
. Differen t statistica l technique s mak e differen t assumption s abou t

th e psychometri c natur e o f th e variable s bein g investigated , an dassumption s abou t th e natur e o f

share dvarianc e (Yul e e t al , 1981 ) wil l determin e th e orde r o f entr y int o step-wis e regressio n analysis
. Ther e i s n o 'right ' answe r a s t o whic htechniqu e i s bes t i n an y particula r

circumstance , bu t

eac hinvestigato r

need s t o b e awar e o f

th e consequence s tha t follo w fro mth e choic e o f statistica l procedure
.
O f all - 

### t h e reporte dstudies , tha t b y Needlema n e t

a l (1979 ) i s th e mos t impressive
. 2,14 6 firs t an dsecon dgrad e childre n wer e divide dint o s i x group s accordin g t o th e estimate dleve l o f lea di n on e discarde d tooth
. Teachers , blin dt o th e toot hlea dlevels , rate dth e children' s behaviou r

o n eleve n forced—choice s scales
. Althoug hn o dat aar e give n
o n th e psychometri c propertie s o f th e scale , teachers ' ratings , wer e

i 

### foun dt o relat e closel y t o toot hlea dlevels
. Nea r linea r relation s betwee n increasin g lea dan dincreasin g proportio n o f teachers ' negativ e rating s wer e reporte do n eigh t ou t o f th e eleve n items
. Socia l factor s
wer e no t

controlle di n th e mai n analyses
. Thes e wer e surprisin g an dchallengin g findings
. Th e dat aindicate da dose—respons e relationshi p betwee n toot hlea dlevel s an dbehaviou r a t
ver y lo w level s o f

toot hlead
. Suc hfindings , i f replicated , hav e
enormou s implication s fo r ou r understandin g o f

th e effect s o f

lo w leve l lea dexposur e o n children' s development
.P. 7

Sinc e it s publication , Needlemane t al' s (1979 ) stud y ha s beenth

e subjec t
o f considerabl e interes t an d controversy . Initially , concerncentred
aroun d th e selectio

no f th e 'high ' an

d 'low ' toot

hlea d groups , th

e natur e o f th

e psychologica l measures , an d th e handlin

g o f confounding variable s (Rutter , 1980 ; DHSS , 1980 ; Yul e an d Rutter , 1984) . Mor e recently , th

e America

nEnvironmenta l Protectio nAgency

examined th

e stud y wit hgrea t car e an d concluded that certai npreviousl y unrecognised methodologica l error s wer e evident , Marchal l (1983) . A re-analysi s
o f Needleman' s dat a wil l b e o f grea t interest . Meanwhile , there hav e bee nthree othe r genera l populatio nstudie s o f denta l lea d published . Th

e firs t tw

o wer e undertakenb y Winnek e an

d hi s colleague s inDuisber g (Winneke , Hrdin a an d Broekhaus , 1982 ) an d inStollber g (Winneke e t al , 1983) . Inth e earlie r pilo t study , 2 6 childre nwit h toothlea

d concentrationbelo w 3 part s per million(ppm ) wer e compared wit h2 6 wit hlevel s abov e 7 ppm . The

y wer e assessed o

na batter

y o f neuropsychologica l tests , an d teacher s rate

d thei r behaviour . Childre n wit hth

e highe r toot

hlea d level s tende

d t o perfor

m les s wel l o

nth e tests , bu t n

o difference s wer e foun d o nbehaviour ratings . The stud y ha d smal l number s an d weak contro l o f potentiall y confoundin

g socia l variables . Inth

e second , majo r study , carefull y selected group s o f lo w (belo w 4. 2 ppm) , middl e (5. 8 - 7. 2 ppm ) an d hig h(abov e 9. 8 ppm ) toothleads , amountin g t o 11 5 childreninall , wer e tested . Thi s time , test s o f reactiontim e wer e adde

d t o th e batter

y an d parent s provided dat a o n5 0 possibl e confoundin g variables . Again , th e highes t lea

d grou p ha d lowes t IQ , bu t th e effec t wa s reduced t o non-significan t level s whe nconfoundin g variable s wer e controlled . The finding s hav e t o b e treate

d wit hcautio

nbecaus e o f th

e smal l sampl e size , th e lo w proportiono f childrenrecruited int o th e study , an

d th e us e o f neuropsychologica l test s intranslation .P. 8

7 . Mos t recently , Smithe t a l (1983 ) hav e reported o

na large scal e stud y
o f 6 t o 7 yea r old s livin g inLondon . Screenin g dat a wer e gathered o na tota l populatio

no f 687 5 children , 6 0 pe r cen t o f who m donated a t leas t
on e tooth . Th e lo

w lea d grou p ( N ° 145 ) comprised thos e wit ha tooth lea d leve l o f 2. 5 pp

m or less,th

e mediu m lea d grou p ( N • 103 ) ha

d level s inth e rang e 5 t

o 5. 5 ppm , an

d th e hig hlea d grou p ( N - 155 ) wer e thos e abov e 8 ppm . Childrenwer e givenWISC-R , test s o f attainmen t an d reactio ntime ; teacher s completed behaviour ratin g scales ; mother s
wer e teste

d o ntw o subtest s o f WAIS , an d gav e detailed informationon th e child' s developmen t a s wel l a s curren t socia l condition s inth e •home . The thre e lea d group s differed significantl y i nFul l Scal e I Q (Hig h- 103.7 ; Mediu

m - 104.9 ; an

d Lo w - 108.7 ) an

d inreading . The hig hlea d grou p showe d mor e hyperactivit y o nth e Conners- ' scal e tha n th e others . Th

e I Q difference s remained , bu t wer e n o longe r statisticall y significant , followin g correctionfo

r confoundin

g variables . Ingeneral , thi s
wa s a ver

y wel l conducted stud y whichha s added considerabl y t o ou r understandin

g o f toot

hlea d measure s an

d thei r relationshi p t o children' s development . However , th e childrenwer e rathe r youn g an d overal l wer e relativel y

sociall y

advantaged . Mor e importantly , ther e ar e tw o majo r
concern s ove r thei r multivariat e analyse s (Yul e an d Rutter , 1984) . Firstly , covariate s wer e selected i f the y correlated wit hth e dependen t variable , irrespectiv e o f whethe r the

y correlated wit hlea d (an d man y di d not) , whennormall y covariate s ar e selected i f the y hav e significan t correlation s wit hbot hth e independen t an

d dependen t measures . Secondly , wit h5 t

o 7 covariates , there i s a dange r o f over-correcting an d therefor e overlookin

g a neffec t o f lead .P. 9



### 8 .

Overall , al l fou

r toothlea

d studie s sho

w a remarkabl e consistency in findin g a smal l differenc e inI Q betweenhig han d lo w lea d groups , even afte r controllin

g for socia l factors . Ther e i s greate r doub t regardin g th e behavioura l effect s i ntha t th e association s wit hlea d level s wer e
wea k an d inconsisten t inbot hth e Germanan

d th e Englis hstudies . Th e reason s fo

r th e discrepancy

wit hth

e Americanstud

y ar e unclear . I t wa s no t jus t a functio no f controllin

g fo r socia l variables , intha t th e association s wer e wea k evenbefor e correction . I t coul d b e a matte r
o f differen t measure s (al l fou r studie s use

d differen t scales,) , i t coul d reflec t variation s i nlea d level s (whichwer e substantiall y highe r inth e Needlema nstudy) , or i t coul d b e a consequenc e o f population differences .
I t i s therefor e stil l pertinen t t o examine th

e relationshi p betwee n bloo d lea d level s an

d th e rating s o f children' s behaviour . The presen t stud y aros e fro

m tw o o f th e authors ' (R . Lansdow nan d W . Yule ) membershi p
o f th e Britis hDepartmen t o f Health' s Working Part y o nth e effect s o f lea d o nchildren' s healt h(DHSS , 1980) . I t begana s anattemp t t o examine th

e us e o f Needleman' s teachers ' ratin g scal e ina smal l sampl e
o f 16 6 childre nfo r who m estimate s o f bloo d lea d level s wer e available . Th e stud

y wa s intended a s a pilo t stud y fo r mor e intensiv

e investigations , I t wa s mounted quickl y inrespons e bot ht o perceived need an d t o an opportunit y

, an d ther e wa s no t tim e t o gathe r dat a o

nsocia l factor s othe r tha

nfather' s occupation . However , individua l measure s o f intelligenc e an

d educationa l attainmen t wer e obtained an d th e result s
o nthes e ar e reported separatel y (Yul e e t al , 1981) . I naddition , teacher s completed othe r standar d rating s o f children' s behaviour .P.1 0

METHO D 9 . A 

### Sample I n one o f

th e autonomous screening s o f bloo d lea d level s i n childre n undertake n b y loca l medica l an d environmenta l healt h authoritie s i n respons e t o th e ES

C directive , i n a

n are asubjec tt o a

n earlie rsomewha

t simila rsurvey , (Millar , 1978 ) 40 0 childre n livin g nea raleadwork s i n oute rLondo

n were studied . Bloo d sample s wer e take n b y venepunctur e an d analyse d i n th e Departmen to f Chemica

l Patholog y an

d Huma n Metabolism , Universit y o f

Southampton , unde rth e directio n o f Professo rBarbar aClayto n an d Dr . Trevo rDelves . Po rth e purpos e o f th e presen tpilo tstudy , i twa s decide d t o tes tal l primary-schoo l ag e childre n i n thi s grou p whos e parent s an

d school s consented . Thi s pape rreport s o

n th e result s o f

th e teache rrating s o f behaviou r fo rchildre n age d 6-1 2 years . Th e respons e rat e wa

s 3% a__ d th e sampl e wa s composed predominantl y o f childre n o f

skille d manua

l workers . On

e chil d wa

s found t o hav e abloo d lea d leve l o f 60jag/100 ml. , relate d t o th e ingestio n o f

paint . She ha

d bee n chelate d befor e testin g bega n and he rresult s hav e bee n omitte d fro m th e study . Otherwise , bloo d lead s range d fro

m 7 t o 32^ig/lO O ml . wit h amea n o f 13.52/ig/10 0 ml . (S D - 4.13) . (Pul l detail s o f th e sampl e ar e give n in.Yul e e tal . 1931. )

O n average , th e childre n were 8 year s 6 month s ol d (S D • 2 2 months) . Thei rreadin g age s o

n th e Neal e tes twere , o n average , withi n on e mont h
o f thei rchronologica l age . Thei rspellin g an d mathematic s standar d
score s were , respectively , 9 4 (S D - 14.8 ) an

d 9 4 (SD - 13.3) , agai n withi n th e norma

l range . Thei raverag e WISC- RIQ s were : Verba l - 96. 8 (S D - 14.2) ; Performanc e - 100. 3 (SD - 13.4) ; an d Pul l Scal e I

Q - 98. 2 (S D - 13.4) . Thus , thi s sampl e i s wel l withi n th e norma l rang e o f

educationa l attainmen t
an d intelligence .P.1 1



### Teachers ' Rating s i o 

### Thes e were complete d i n th e Summe rterm 1930 , appnftimatel y on e yea r afte rth e bloo d sample s were obtained . I n additio n t o completin g th e 1 1 ite m Needlema

n questionnaire , teacher s were aske d t o rat e al l childre n o h th e 26-ite m Teache rRatin g Scal e B(2 ) (Rutte ran d Yule , 1963 ) an

d th e 40-ite m Conners (Conners , 1969 ) scale . Th e B- 2 wa s include d a s i ti s widel y use d i n Britai n a s ascreenin g scal e fo rgenera l behavioura l o r emotiona l difficulties , abou twhic h agrea tdea l i s know n (Rutter , 1967 ; Rutter , Tizar d S. Whitmore, 1970 ; Rutter , Craham , Chadwic

K4 Yule , 1976 ; Rutter , Cox, Tupling , Berge rk Yule , 1975) . Th e Conners Scal e was ' " include d a s i tha s bee n widel y use d i n th e stud y o f hyperactivity , particularl y i n relatio n t o treatmen tb y drug s (Conners , 1969 ; Sandberg , Rutte rand Taylor , 1978) . Psychologica l Testin g Thi s wa s undertake n b y traine d psychologists . Childre n were individuall y assesse d on th e Wechsle rIntelligenc e Scal e fo rChildren-Revise d (Wechsler , 1974 ) an

d th e Neal e Analysi s o f Readin g Ability , For m A (Neale , 1958) . The

y were teste d i n smal l group s on th e Vernon Grade d Wor d Spellin g Tes t(Vernon , 1977 ) an d th e Vernon Grade

d Arithmetic-Mathematic s Tes t (Verno n an

d Miller , 1976) .
RESULT S

a ) : Th e Needlema nQuestionnair e i 

### The l sampl e wa

s spli tint o quartile s accordin g t o bloo d lea d leve l i n orde r t o perform statistica l analyse s analogou s t o thos e performe d b y Needlema n e ta l (1979) .P.1 2 

### 11 .

_ 

### Tabl e 1 shows th e percentag e o f childre n i n eac h bloo d lea d quartil e wh o receive d negativ e rating s fro m thei rteacher s o

n eac h ite m o

n th e Needlema n scale . O

n 2 item s ther e were discernabl e trend s fo rchildre n wit h highe rbloo d lea d level s t o receiv e mor e negativ e ratings . Th e overal l association , assesse d b y chi-square , wa s significan ti n 5 o f

th e 1 1 items . I n fou rother s - distractible , no tpersistent , dependent , an d disorganise d - i tseems tha tchildre n wit h bloo d lea d level s o f 12^ig/l0 0 ml . an

d belo w receiv e fewe rnegativ e rating s -tha n thos e abov e thi s level . A s i n th e Needlema n sample , hyperactivit y wa s note d i n ver y fe w childre n an

d wa s no tassociate d wit h bloo d lea d level . Th e result s ar e show n graphicall y i n Pigur e 1 .

(Figur e 1 nea rhere )

Th e tota l score s on th e Neeldema n questionnaire s diffe racros s th e fou rbloo d lea d grouping s a taleve l which i s no tstatisticall y significan t( P• 2.15 , P• 0.096) . There is , however , atren d fo r th e tota l score s t o increas e wit h increasin g bloo d i«a d level s with , again , th e greates tdifferenc e occurrin g a tth e 1 2 ng/10 0 ml . cu tof f point •
b ) Th e Rutte rB(2 ) Questionnair e Tabl e 2 shows th e percentag e o f childre n abov e an

d belo w th e median lea d leve l bein g rate d a s "deviant " - i.e . scorin g 1 (Applie s somewhat )
o r2 (Definitel y applies ) - on th e B(2 ) scal e b y thei rclas s teacher . I tca n b e see n tha ti n 2 0 ou to f 2 6 items , childre n i n th e uppe r50 $
o f lea d level s were rate d mor e devian ttha n thos e i n th e lowe r5C$ . Th e difference s wer

e statisticall y significan t(p^0.05 ) i n two item s

- "Squirmy " and "Fights " - an d marginall y significan t(0.05>P>.10 ) i nP.1 3



### A furthe rfiv e - "Sucks Thumb" , "Bite s Nails" , "Inert" , "Disobedient" , "Truants" . I n th e eas e o f "Truants" , thi s wa

s commone

ri n childre n wit h lowe rbloo d lea d levels ! Th e increas e i n thum

b suckin g an

d bitin g nail s i n th e highe rlea d grou p i s obviousl y o f interes ti n s o fa ra s i t indicate s on e behavioura l mechanis m whereb y increase d lea d ca n ge tint o th e body . Overall , however , th e association s wit h individua l item s ar e small . Thi s probabl y indicate s tha tonl y asmal l proportio n o f th e Varianc e o f

behavioura l devianc e an d bloo d lea d level s i s share d and tha t large rnumber

s wil l b e neede d t o understan d th e natur e o f th e association . Recently , afacto ranalysi s o f th e B(2 ) scal e (Schachar , Rutte ran d Sfaiith , 1981 ) foun d aseparat e "overactivity " factor , define d b y addin g th e score s on th e followin g items: - RESTLES S + SQUIRM

! + CAN' T SETTLE

. Childre n ar e classifie d a s "overactive " i f thei rscor e i s 3 o rmor e on.thes e items . A s ca n b e see n i n Tabl e 3rsignificantl y mor e o f th e childre n i n th e highe rlea d group s ar e classifie d a s "overactive" . Indeed , 4.9 $ o f thos e belo w th e median lea d leve l compare d wit h 19.0 $ abov e ar e classifie d a s "overactive" .

c ) Th e Conners Questionnair e As o n th e B(2 ) scale , ther e were fe w individua l item s o n th e Conners scal e vhic h relate d significantl y t o bloo d lea d levels . However , th e scal e ha s bee n show

n b y factor-analysi s t o yiel d anumbe ro f sub-scale s vhic h hav e bee n replicate d i n avariet y o f studie s (Conners , 1969) . Tabl e 4 sunnnarise s th e result s o f fiv e one-way analyse s o f varianc e i n which th e childre n hav e bee n divide d a tth e media n scor e int o lo w an

d hig h bloo d lea d groups . As ca n b e seen , o n ever y sub-scale , th e childre n vit h highe rbloo d lea d value s ar e rate d a s mor e deviant , an

d thi s reache s statistica l significanc e i n relatio n t o Conduc tProbleas , Inattentive-Passiv e an d Hyperactivity .P. J 4


### 13
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tw o scales ^ i s heavil y develepseatall y loaded
. Younger ehild_?e atherefor © ar e giv© a highe r seo?©s! o Yeuage ? ehildre aals e hav© highe r bloo dlea dlevels
. averag e @g

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. o aiadividua ! itea s shoul db © treat s wit heaatio afo r tw o yeaaoas . firstly, ; th e shorte r th e ®ea_-@ s 

### th e les s reliabl e i t is
. _k___3ate dscore s o r

facto r score s §__

© alway s ©er e reliabl e tha aindividua l items
. Secondly, , wit hs e aaa y individua l itea s beia g ©sasiaed, , som e difference s ar e bcua dt e aris e b y e__aace0 

### Over al l thre e teache r

ratin g sc&le& y 7 7 iadividua l itea s wer © rated , l y ehaae © ales © 4 ea s b e expecte dt e b e "significant 5 3 

### a t th e % level , l afact 9 

### oal y 7 ites s wer © foun dt o b e relate dt e lea dleve l a . P o 0.05
. Thi s ©i^a t b e regarde da s iadicstia g oal y chaac © level s bu t fe ? tw o faet©?ss ~ firstly, , 4 e f th e 7 itea s wer o e ath e _me h shorte r

Beedlesm aScale j gieeoadly, , th © r©@alt s e ath e ^©©Ideaa aSeal ® a s a©t©d©asflier,- , b y sa dlarg e ?©plieat © hi ® ©arlieg ? gstedy 0 

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9 

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t al c 

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© hav© shew atha t

seer© ® e ath © -jQS&lesaaScale s ar e highl y relate dt e score s o ath © Butte r Scale
. KorQover, ; iadividua l Ueedle@aaSeal © ites s she w a e ag e leadings, , oal y ea g se x differeac e aa doal y tw o ©igaifieaa t relationship s wit hsocia lP.1 5



### class . However , 9 o f th e 1 1 item s showe d significan t relationship s vit hWISC- RPul l Scal e IQ . I t voul d see m tha t th e Needlema nScal e i s tappin g broadl y

simila r area s t o th e Rutte r and th e Conner s scales . However , i t appear a t o b e mor e sensitiv e t o bod y lea d level s an

d thi s
ma y b e becaus e i t tap s behaviou r relate d t o focussin g attentio nrathe r tha a wide r categories .

DISCUSSIO N Thes e result s broadl y replicat e th e finding s o f Needlema net a l (1979 ) i a respec t o f teachers ' rating s o f behaviour . O nth e sam e items , ther e ar e indication s o f a dose—respons e relationshi p betvee nincreasin g lea d level s an d a nincrease d likelihoo d tha t teacher s recor d devian t behaviour . A numbe r o f difference s betvee nNeedleman' s stud y an d th e presen t on e
mus t b e noted . Firstly , hi s scal e va s use d vit hAmerican.'teacher s and i t ha s no t previousl y bee nuse d i nBritain . Hovever , i t doe s appea r tha t i t i s bein g use d i na simila r way . Secondl y th e presen t study

ha s smalle r number s and a wide r ag e rang e o f children . Thirdly , th e estimat e o f bod y

lea d burde ncame fro m a singl e determinatio no f bloo d lea d leve l take nsom e nin e month s prio r t o th e teachers ' rating s o f behaviour . Wit hthes e difference s i nmind , th e similarit y t o Needleman' s finding s i s al l th e mor e impressive .

Th e result s o nth e facto r score s derive d fro m bot hth e Rutte r B(2 ) scal e and th e Conner' s Scal e provid e harde r evidenc e fo r a nassociatio n betvee nincreasin g bloo d lea d level s and increasin g rating s o f hyperactivit y b y teachers . I t mus t b e remembere d tha t thi s i s a nassociatio nvithi n
a nessentiall y

norma l sampl e o f children . The y ar e no t see nb y

thei r teacher s a s bein g i naay va y undul y devian t i nthei r behaviour . Thes e result s ca nb e viewe d a s th e firs t rea l confirmatio no f th e existenc e
o f thi s relationship .P.1 6



### 15 .

However , th

e result s o f th

e presen t pilo t stud y canno t investigat e full y th e natur e o f th

e demonstrated associations . Becaus e father' s occupation i s th e sol e datu

m availabl e o

nsocia l factors , w e hav e no t attempte

d in thi s stud

y t o partia l ou t th

e contributio

no f socia l factor s t o th e presen t findings . Man

y aspect s o f famil y lif e or chil d rearin g practice s coul d b e related t

o children' s behaviour , intelligenc e an d exposur e t

o lea d in th e environment . Goo d measure s o f relevan t socia l an d famil y

factor s
ar e required withlarger number s o f childrenbefor e th e natur e o f th

e relationshi p betweenbod y lea d burdenan

d adjustmen t ca

nb e bette r understood . A

secon d suc hstud y i s no w in progres s an

d w e awai t th

e result s o f tha t stud y befor e explorin

g th e natur e o f th

e relationshi p further .
A s noted inth

e introduction , i t i s unfortunat e that th e Englis h(Smit h
e t al , 1983 ) an

d German(Winneke e t al , 1982 ; 1983 ) studie s di d no t include identica l measure s a s thos e use d b y Needlemane t a l (1979) . I t remain s unclea r a s t

o th e reason s fo

r th e largel y

negativ

e finding s wit hrespec t t o behaviour ratings . I npart , invie w o f th e presen t findings , som e o f th e differenc e mus t hav e t o d o wit hth

e propertie s o f th e scale s used ; i npart , differen t characteristic s o f th e sample s ma

y li e behin

d differen t findings . Smit he t a l (1983 ) looke d a t th

e younges t group . Evenyounge r childrenwer e observe d durin g testin

g inth

e recen t Birmingha m stud y (Harve y e t al , 1983) , wher e direc t observationwa s no t related t o th e bloo d lea d levels . Thus , ag e o f sampl e ma y b e animportan t factor . Similarly , Smit he t a l (1983 ) ha d a mor e sociall y

advantaged grou

p tha n eithe r ou

r Londo nsampl e or th

e Germansample . I nbothth e German studie s an

d ou r own , I Q effect s wer e foun d t o b e stronge r inth

e sociall y disadvantaged subgroups . Clearly , thi s ha s t o b e investigated mor e full y i nrespec t o f behavioura l ratings .P.1 7



### 16 .
Despit e th

e similarity

betwee nth

e presen t finding s an d thos e o f Needleman
e t a l (1979) , th

e finding s fro

m othe r investigation s ar e contradictory . I t i s prematur e t

o rul e ou t th

e possibilit y

o f aneffect , but , equally , there ar e n

o stron g ground s a t presen t fo r inferrin

g one . The fac t tha t th e stron g effect s o

nbehaviour ste

m fro m studie s tha t wer e unabl e t o contro l fo

r confoundin

g variable s mus t rais e rea l doubt s abou t th e reality o f th e effect . O

nth e othe r hand , th

e behavioura l measure s hav e beenles s adequat e tha nth e cognitiv

e assessment s an

d i t ma y b e tha t th e inconclusiv

e finding s simpl y

reflec t th

e weaknesse s o f th e tool s
use d t o evaluat e behaviour (Yul e an d Rutter , 1984) . Davi d e t al' s (1983 ) findin

g regardin

g th e apparen t behavioura l benefit s o f chelation
mean s tha t th

e possibilit y

o f lea d effect s o

nbehaviour canno t b e dismissed . Wha t ar e needed ar e wel l planned longitudina l studie s whichtak

e repeated measure s o f neuropsychologica l functioning , academi c attainmen t an

d behaviour . Togethe r wit hmor e refined measure s o f socia l factors , suc

ha longitudina l stud y woul d g

o a lon g wa y toward s unravelling
causa l relationships , whos e natur e canonl y b e imperfectl y

inferred fro

m saml l cross-sectiona l studies .

ACKNOWLEDGEMENT S Thi s stud

y wa s supported b

y a gran t fro

m th e Medica l Researc hCounci l (SPG/979/1160) . W e ar e gratefu l t o officer s o f th

e Inne r Londonan

d Bexle y EducationAuthoritie s an d t o th e headteacher s an

d teacher s fo

r thei r co-operation . We wis ht o acknowledg e th

e generosit y

o f Drs . Taylo r an

d Sandberg i nmakin g thei r unpublished dat a availabl e t o us . Mis s J . Hunte r assisted i nth e dat a analysis .REFERENCE S

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g scal e fo

r us e indru

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### ti. 

## MARSHA L CWS ) tf

o Tki tOki!>i

. ' ^ 1:^^«'W^ . iWv X

MILLAR , I.B . (1978 ) Monitorin g lea d i nth

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>ediat „ P«vrhoi. . ft as-o sP.1 9

NEALE , M.D . (1958 ) Neal e Analysi s o f Readin g Abilit y

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d levels . Ne

w Eng.J . Med. . 300 . 679-695 . NEEDLEMAN , H.L . an d LANDRIGAN , P.J . (1981 ) The healt heffect s o f lo w leve l exposur e t

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n b y teachers : preliminar y findings . J . Chil d Psychol. , Psychiat. , 

## ! » 

## i-n
. RUTTER , M . (1980 ) Raised lea d level s an

d impaire

d cognitive/behavioura l functioning : A

revie w o f th e evidence . Devel.Med.Chil d Neurol . 22 , Supplemen t No : 42 . RUTTER , M . (1983 ) Famil y an d schoo l influences : meanings , mechanisms an d implications . InA.R . Nico l (Ed ) Practica l lesson s fro m Longitudina l Studies . Chichester : Wiley(i n press ) RUTTER , M. , COX , A. , TUPLING , C , BERGER , M. , an d YULE , W . (1975 ) Attainmen t an

d adjustmen t intw o geographica l areas . I . The prevalenc e o f psychiatri c disorders . Brit . J . Psychiat. , 126 , 493-509 . RUTTER , M. , GRAHAM , P. , CHADWICK , 0. , an d YULE , W . (1976 ) Adolescen t turmoil : Fac t or fiction . J . Chil d Psychol. . Psychiat. , 17 . 35-36 . RUTTER , M. , TIZARD , J. , an d WHITMORE , K . (Eds ) (1970 ) Education . Healt h an d Behaviour . London : Longmans . RUTTER , M. , an

d YULE , W . (1968 ) Teache r Rating Scal e B(2) . London : Institut e o f Psychiatry . SANDBERG , S. , RUTTER , M . an d TAYLOR , E . (1978 ) Hyperkineti c disorder s inpsychiatri c clini c attenders . Devel.Med.Chil d Neurol. . 20 , 279-299 . SCHACHAR , R. , RUTTER , M. , an d SMITH , A . (1981 ) Th e characteristic s o f situationall y

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nurbanchildren . Develop.Med . Chil d Neurol. . 25 , Supplemen t No :P.2 0

VAHTER , M . (Ed ) (1982 ) Assessmen t o f HumanExposur e t o Lea d an d Cadmiu

m Throug hBiologica l Monitoring . Stockholm : Nationa l Swedis h Institut e o f Environmenta l Medicin e an d Departmen t o f Environmenta l Hygiene , Karolinska Institute . VERNON , P.E . (1977 ) VernonGraded Word Spellin g Test . London : Hodde r an d Stoughton . VERNON , P.E . an

d MILLER , K . (1976 ) VernonGraded Arithmetic-Mathematic s Test . London : Hodde r an d Stoughton . WECHSLER , D . (1974 ) Manua l o f th e Wechsle r Intelligenc e Scal e fo r Children-Revised . Ne w York : Psychologica l Corporation . WINNEKE , G. , KRAMER , U. , BROCKHAUS , A. , EWERS , U. , KUJANEK , G. , LECHNER , H .

an d JANKE , W . (1983 ) Neuropsychologica l studie s inchildrenwit h elevated tooth-lead-concentrations . II . Extended study . Internat . Arch . Occup . Envir . Health . 52 , WINNEKE , G. , HRDINA , K-G , an d BROCKHAUS , A . (1982 ) Neuropsychologica l studie s inchildre nwit helevated tooth-lead-concentrations . I . Pilo t study . Internat . Arch . Occup . Envir . Heatlh . 51 , 169-183 . YULE , W. , LANSDOWN , R. , MILLAR , I.B . an d URBANOWICZ , M-A . (1981 ) Th e relationshi p betweenbloo d lea d concentrations , intelligenc e an d attainmen t i na schoo l population : A pilo t study . Devel . Med . Chil d Neurol. . 2Z_ t 567-576 . YULE , W . an

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critica l review : I nK.R . Mahaffey (Ed ) Healt hImplication s o f Typica l Level s o f Lea d Exposure : Dietar y an d Environmenta l Sources . Amsterdam : Elsevier .

.P.2 1



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0.5 2 0.4 7

5.8 8 0.0 2

4.9 7 0.0 5

## PERCENTAG E O F NEGATIV E RATING S O N NEEDLEMAN SCALE S B Y LEAD LEVEL

S Pilo t lea d study-16 6 childre n age d 6-1 2 year s 

# 7 lo


## 5 0 h

4 0

3 0 h

2 0

1 0 

# (l i

123 4 123 4 Distracte d Persis

t
LEA D LEVELS 1 7-1 0 fig/d l 2 1 1 -1 2 " 3 13-1 6 " A 17-3 2 

# n 4 12 3 Wor k Indept . 

# n

123 4 Disorg anize d 

## 123 4 123 4 12 3 12 3 

# n 123 4 123 4 

# 1 IU I 123 4 Hyper - Impulsive Frustrate d Day - Simpl e Sequenc e Genera l activ e drea m direction s direction s Functioni n