Effect of low-level lead exposure on neurobehavioral function in preschool children

Jianan LIU; Jin JING; Xiaohong LIANG; Xuebin CHEN

ABSTRACT

BACKGROUND:

Environment pollution due to lead is severe day by day,and the lead-induced developmental toxicity of central nervous system is prominent.

OBJECTIVE:

To observe the effect of lead at low exposure level on neurobehavioral function of preschool children and provide basis for preventing childhood behavior disorders.

DESIGN:

Sampling survey.

SETTING:

Department of Children and Adolescent Health, Public Health College, Sun Yat-sen University.

PARTICIPANTS:

Totally 211 children of 4-6 years (109 boys and 102girls) were enrolled from a kindergarten of a populated area of Zhuhai City by randomized cluster sampling from September to October 2004.

METHODS:

20 mL peripheral blood of finger tip was collected. Blood lead was determined with graphite stove atomic absorption spectrometry.According to the amount of blood lead, the children were divided into high blood lead exposure group (＞100μg/L) and low blood lead exposure group (＜100μg/L). Furthermore, they were also assigned into ＜50 μg/L group, 50μg/L- group, 100μg/L- group, 150 μg/L- group, 250- μg/L group. Achenbach's Child Behavior Checklist (CBCL) and self-designed questionnaire (composed of possibly effective factor on children's neurobehavioral function, such as age, sex, cultivation, family background and so on) were applied, filled by their parents under the instruction of professional staffs. Results and blood lead value were analyzed with first order correlation and multiple factors stepwise regressive analysis.MAIN OUTCOME

MEASURES:

①Blood lead level and each factor scores of CBCL, ②correlation analysis between blood lead value and behavioral factor score.

RESULTS:

A total of 211 questionnaires were sent out, and 211 were retrieved with 211 effective questionnaires. The effective rate was 100%. ①Score on externalizing and behavioral disorder rate in the high blood lead exposure group (13.28±6.26,18.26%) was significantly higher than those in the low blood lead exposure group (9.98±5.46,7.29%)( t=4.067 7,χ2=5.470, P＜0.05). There was insignificant difference in score on internalizing and total score of CBCL between the low and high blood lead exposure groups. ②The behavioral disorder rate of different blood lead level had significance (χ2=13.695,P＜0.01). The behavioral disorder rate in blood lead ≥ 150 μg/L was obviously higher than that of the former 3groups after further pairwise comparison (χ2 were 4.727, 6.261, 5.168;4.503, 5.911, 4.928, P＜0.05), which revealed that the child behavioral disorder rate markedly increased when the blood lead was ≥ 150 μg/L.③Blood lead logarithm value had positive correlation with the scores on hyperactivity, aggression and defiance (r=0.316 4,0.282 8,0.188 6,P ＜0.05), and had no correlation with obesity, desintegration, truculence and sexual questionnaire (r=0.102 4,0.094 2,0.118 3,0.092 6,P ＞ 0.05). ④After the stepwise regression analysis, the scores on hyperactivity, aggression and defiance factors were included in the regression equation. The results suggested that the effect of lead on child externalizing behavior still remained, and kept statistical meaning after confounding factors, such as controlling family and society, etc.

CONCLUSION:

Low-level lead exposure has adverse effects on externalizing behavior in preschool children.