Exposure to Toenail Heavy Metals and Child Behavior Problems in Nine-Year-Old Children: A Cross-Sectional Study

Behavioral problems are multifactorial and includes perinatal, maternal, family, parenting, socio-economic and personal risk factors, but less is known about the association of postnatal heavy metals on children's behavioral problems in Pacific Island children.

A cohort of eligible nine-year-old children within a Pacific Island Families longitudinal study were recruited for a cross-sectional study. Child behavior problems were assessed using the child behavior checklist. Heavy metals (including Ni, Cu, Pb, Al, Cr and Cd) were determined in toenails, after acid digestion and analyzed using inductively coupled plasma mass spectrometry. Other factors such as lifestyle (smoking in pregnancy), health outcomes (obesity, health status), demographics (gender, ethnicity, parents' marital status) and socioeconomic status (household income levels) were also collected. The statistical analysis included t-tests for independent sample and Mann-Whitney U-test, and chi-square or Fisher's exact tests of independence for comparisons of the proportions. Regression models tested the hypothesized risk factors for behavior outcomes.

This observational study enrolled 278 eligible Pacific Island children living in Auckland, New Zealand. The prevalence of behavioral problems in the clinical range was high (22%) but there was no significant association between heavy metals in toenails and adverse behavioral outcomes.

Regular monitoring and assessments of children for environmental risk factors, as well as social and lifestyle factors for behavior problems, continues. Alternative indicators of exposure to heavy metal should be evaluated.