OAR Box 1128 

Prepped by Ollie Stewart 

Document Number: 

11) 11-1-255 

Docket Number: 

A-83-22 

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THE RELATIONSHIP OF LOW LEVEL LEAD EXPOSURE AND LANGUAGE DEVELOPMENT IN 

THE PRESCHOOL YEARS 

M. Morrow-Tlucak*, C.B. Ernhart*§ 

ABSTRACT 

It was hypothesized that language development would be adversely 

affected by low level lead exposure in the prenatal and early preschool 

periods. As part of a prospective study of developmental risk factors, 

blood lead (PbB) determinations were made at birth (maternal and cord), 

6 months, 2 years and 3 years of age. These measures were related to 

expressive and receptive language at ages one, two and three and to 

productive speech at age two. 

Due to the large number of non-independent tests, alpha was set at .01. 

Multivariate F tests or multiple regression analyses, incorporating 

appropriate covariate control, revealed that PbB was not related significantly or in a consistent manner to any of che language measures. 

INTRODUCTION AND METHOD 

This report is one of the first relating low level lead exposure to 

language development. Reports of developmental effects of low level 

lead exposure have been inconsistent. However, most previous studies 

have used the Bayley Scales which primarily measure sensorimotor developraent. Possible effects of 1< ad exposure on the development of early 

linguistic skills is an important area of concern. The purpose of this 

report is to describe the relationship of prenatal and early preschool 

age lead exposure to speech/language development in a cohort of 359 

children being followed prospectively in a study of risk factors in 

childhood development. 

The mothers of the children in this study were recruited at their first 

prenatal visit. Recruitment was designed to maximize inclusion of 

children at risk for developmental deficit due to prenatal alcohol 

exposure. Other teratological and sociocultural risk factors were also 

assessed, both to control for confounding and to examine the relationship of these risk factors and child development. Demographic information was obtained and antenatal risk factors assessed during the course 

of prenatal care. Additional maternal measures were obtained postpartum. The sample included in one or more of the lead analyses 

(N=284) did not differ in any respect from the original cohort. The 

sample has been described elsewhere (ref 1). Briefly, almost without 

exception, this cohort was from the lowest two socioeconomic levels 

(Hollingshead 2-factor Index). Mean maternal age and educational level 

at recruitment were 21.9 and 10.7 years respectively. 34.5% of the 

sample was black; 51.8% of the children were male. 

Follow-up examinations were made during home visits by trained examiners blind to all risk factors. In-home testing was used in order to 

minimize attrition and facilitate measurement of the home environment. 

*Department of Psychiatry, Cleveland Metropolitan General Hospital, 

3395 Scranton Road, Cleveland, OH 44109 (Address for correspondence). 

§Departments of Psychiatry and Reproductive Biology, Case Western 

Reserve University, Cleveland, OH, USA. 

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59 

RESULTS AND DISCUSSION 

First order correlations between the lead measures and speech/language 

measures were generally (but not always) in the hypothesized direction. 

Only 4 correlations were significant at the .01 level. Cord PbB was 

negatively related to MLU (£ • -.27 £ = .003); 2 year PbB was negatively related to receptive language at age 2 (r = -.22 £ = .004); and 

3 year PbB was negatively related to 3 year expressive language 

(r • -.20 £ = .011). 2 year PbB was positively related to intelligibility; as lead level increased, partially intelligible utterances 

increased (r * +.20 £ • .014) and unintelligible utterances decreased 

(£ = -.32 £ = .0001). 

With inclusion of the covariates none of the relationships reached 

significance. For the 8 multivariate F tests relating the PbB measures 

to communicative intent and to intelligibility, none reached even the 

.05 level of significance. For the 36 multiple regression analyses 

relating each of the PbB measures to expressive language, receptive 

language, mean length of utterance, vocabulary, and amount of speech, 

none reached significance at the .01 level. Only one, cord PbB and 

mean length of utterance reached the .05 level (_t = -2.2 £ = .03). 

Further, with control of confounding, the direction of the relationships was not consistent, that is, in slightly more than half the 

analyses lead was not related in the hypothesized direction. 

Confirmatory backward elimination regression analyses were conducted 

for all measures. Lead remained in the model, in the hypothesized 

direction, at the .05 level for only 2 analyses: cord lead remained 

in the analysis of mean length of utterance; cord lead remained in the 

model for one of the three communicative intent measures (expanded 

repetitions). Additionally, 2 year lead remained in the model for one 

of the intelligibility measures (unintelligible utterances). However, 

this relationship was not in the hypothesized direction. 

These results do not support the hypothesis of a detrimental effect of 

low level lead exposure in the prenatal or early preschool period on 

language development. Further, the inconsistency in the direction of 

the relationship reflects what would tend to be found if there was no 

effect or if the effect was quite small and therefore very difficult 

to detect. 

REFERENCES 

C B Ernhart, M Morrow-Tlucak, M R Marler, A W Wolf, Neurobehav Tox 

Terat, in press, 1987. 

This research was supported, in part, by the International Lead Zinc 

Research Organization, the March of Dimes Birth Defects Foundation, 

and by the US National Institute of Alcohol Abuse and Alcoholism.