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Low blood lead levels and behavioral/emotional problems in preschool children


Low Blood Lead Levels and Behavioral/Emotional Problems in Preschool Children

Jianghong Liu, Linda McCauley, Jennifer Pinto-Martin, Walter Rogan, Yingjie Wang, and Xianchen Liu

BACKGROUND

•It is well established that high lead exposure (>10 µg/dL) can predispose children to a range of deleterious behavioral outcomes (Needleman 2009). •It has become increasingly apparent that lower lead levels (e.g. <10 µg/dL) may also have negative effects on cognitive ability, though the effects of low blood lead levels on behavioral outcomes are not well studied.

Aims: To answer the following questions:

•Are clinically elevated BLCs (≥10µg/dL) related to young children’s internalizing, externalizing, and pervasive developmental problems? •Are subclinical BLCs (<10µg/dL) related to the aforementioned behavioral problems? •At what subclinical BLC (if any) are behavioral problems observed?  

METHODOLOGY

Participants

•1,419 preschool children (632 girls and 787 boys) from the larger population-based Jintan Child Cohort Study of 1,656 Chinese Children (Liu et al, 2010).

Measures

Blood lead concentrations (BLC)

•BLC were measured for 1344 children (aged 4-6 years) using a graphite furnace atomic absorption spectrophotometer •Three groups of lead exposure levels: control group (<8.0 µg/dL), subclinical BLC group (8.0-10.0 µg/dL), and clinical BLC group (≥10.0 µg/dL).

Behavioral problems

•Parents and teachers were asked to assess the children with the Chinese version of the Child Behavior Checklist (CBCL) and Caregiver-Teacher Report Form (C-TRF)  during the children’s last year of preschool (5-6 years of age). (Achenbach & Rescorla, 2000).

Cognitive performance

•Children’s cognitive performance was assessed during their last year of preschool by the Chinese version and norms of the Wechsler Preschool and Primary Scale of Intelligence-Revised.

Sociodemographic variables

•Parents completed a questionnaire on sociodemographic data, including child’s siblings and residence along with parental education, occupation, and marital status.

Statistical analysis

•Characteristics of the study sample were summarized by descriptive statistics •General Linear Models were used to examine the association between BLC and behavior T-scores while controlling for sociodemographic factors.  

RESULTS

Chi-square tests (Table 1) showed that the prevalence of clinical-level emotional problems, anxious/depressed, internalizing problems, and DSM-oriented anxiety and pervasive developmental problems (assessed using CBCL/C-TRF) were significantly different across the BLC groups (Figure 1).

For almost all clinical-level teacher-reported behavioral problems, the subclinical blood lead concentration (BLC) group was at increased risk and the clinical BLC group was at the highest risk compared to the control group (Table 2, Figure 2 and Figure 3).

CONCLUSIONS

•Blood lead concentrations in preschool children were associated with increased behavioral problems, especially internalizing problems •Compared to children with BLCs <8 µg/dL, children with BLCs ≥8 µg/dL were at significantly greater risk for pervasive developmental problems

Implications:

•Policy implications: BLCs considered “safe” by current standards (e.g. 8-10 µg/dL) may still have lasting and harmful effects, suggesting the potential need for improved guidelines and prevention programs to address lead exposure. •Intervention implications: Children with BLC e.g. >8 µg/dL may benefit from efforts such as cognitive behavioral therapy to reduce the risk of behavioral disorders and problems.  

Limitations:

•Because blood lead level was measured once from 3-5 years of age, the source of the deficits seen at 6 years of age is unclear. •BLCs were measured at different ages within the sample.

REFERENCES

Achenbach T, Rescorla L. 2000. Manual for the ASEBA preschool forms & profiles. In: Youth, & Families (University of Vermont RCfC, ed). Burlington, VT.

 

Liu J, McCauley LA, Zhao Y, Zhang H, Pinto-Martin J. 2010. Cohort Profile: The China Jintan Child Cohort Study. Int J Epidemiol 39(3): 668-74.

 

Needleman H. 2009. Low level lead exposure: history and discovery. Ann Epidemiol 19(4): 235-238.

 

Support for this research was provided by funding from the National Institute of Environment Health Sciences  NIH/NIEHS

R01-ES018858 and

K02-ES019878-01

For more information, contact Dr. Jianghong Liu (jhliu@nursing.upenn.edu)

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