Manish Arora, Ph.D.
Icahn School of Medicine at Mount Sinai
R00ES020364, R01ES019597, DP2ES025453, R01ES026033, P30ES023515
NIEHS grantees reported that early-life metal exposures, as measured in baby teeth, were associated with behavioral problems in children, and the associations were dependent upon developmental timing of exposure. According to the authors, these findings suggest that the developing brain is uniquely vulnerable to metal exposures at different timepoints.
The researchers estimated prenatal and postnatal manganese, zinc, and lead levels in naturally shed baby teeth from 133 subjects enrolled in a longitudinal birth cohort study in Mexico City. Using an innovative laser ablation method, they reconstructed exposures to manganese, zinc, and lead from teeth histories, to a scale of 1-2 weeks, and identified markers of exposure at discrete developmental periods. They also measured behavior at 8-11 years of age.
They found that early postnatal exposure to manganese, lead, or zinc was associated with increased anxiety symptoms. When examined as a metal mixture, the researchers observed two potential windows of susceptibility to increased anxiety symptoms. Exposures during 0-8 months of age appeared to be driven by manganese. The second window, exposures at 8-12 months of age, was driven by metal mixture and dominated by lead.
Higher prenatal manganese in teeth was linked to a decrease in childhood behavioral problems, specifically hyperactivity and attention. In contrast, postnatal dentine manganese was associated with higher anxiety. According to the authors, these results suggest that prenatal dentine manganese may be protective, whereas excessive early postnatal manganese may increase risk of adverse behaviors, which emphasized the importance of exposure timing.
Citation: Horton MK, Hsu L, Claus Henn B, Margolis A, Austin C, Svensson K, Schnaas L, Gennings C, Hu H, Wright R, Rojo MMT, Arora M. 2018. Dentine biomarkers of prenatal and early childhood exposure to manganese, zinc and lead and childhood behavior. Environ Int 121(Pt 1):148-158.