Very low-level prenatal mercury exposure and behaviors in children: the HOME Study

Nimesh B Patel,Robert L Jones,Joseph Braun,Lawrence C Mccandless,Bruce P Lanphear,Kimberly Yolton,Aimin Chen,Yingying Xu,Kim N Dietrich

doi:10.1186/s12940-018-0443-5

Abstract

BackgroundMercury is toxic to the developing brain, but the lowest concentration associated with the development of behavior problems is unclear. The purpose of this study was to examine the association between very low-level mercury exposure during fetal development and behavior problems in children.MethodsWe used data from 389 mothers and children in a prospective pregnancy and birth cohort study. We defined mean prenatal mercury concentration as the mean of total whole blood mercury concentrations in maternal samples collected at 16- and 26-weeks of gestation, delivery, and neonatal cord blood samples. We assessed parent-reported child behavior up to five times from two to 8 years of age using the Behavioral Assessment System for Children (BASC-2). At 8 years of age, we assessed self-reported child anxiety using the Spence Children’s Anxiety Scale (SCAS). We used multiple linear mixed models and linear regression models to estimate the association between mean prenatal mercury concentrations and child behavior and anxiety, respectively.ResultsThe median prenatal total blood mercury concentrations was 0.67 μg/L. Overall, we did not find statistically significant associations between mean prenatal mercury concentrations and behavior problems scores, but a 2-fold increase in mercury concentrations at 16-weeks gestation was associated with 0.83 point (95% CI: 0.05, 1.62) higher BASC-2 anxiety scores. Maternal and cord blood mercury concentrations at delivery were associated with parent-reported anxiety at 8 years.ConclusionWe found limited evidence of an association between very-low level prenatal mercury exposure and behaviors in children, with an exception of anxiety.

Highlights

Mercury is toxic to the developing brain, but the lowest concentration associated with the development of behavior problems is unclear
We were primarily focused on examining the relationship of prenatal mercury with composite behaviors, but we examined the associations with Attention Deficit Hyperactivity Disorder (ADHD) and anxiety subscales as prior studies found that prenatal mercury was associated with these specific behaviors [8, 12, 16, 18]
This was at higher prenatal mercury levels, it was important for us to examine if such association exists at very low – yet representative – levels of prenatal mercury exposure as we found some evidence of positive association between mean prenatal mercury concentrations and BASC-2 anxiety subscale

Summary

Introduction

Mercury is toxic to the developing brain, but the lowest concentration associated with the development of behavior problems is unclear. The purpose of this study was to examine the association between very lowlevel mercury exposure during fetal development and behavior problems in children. We hypothesized that very low-level prenatal whole blood mercury concentrations (< 4–5 μg/L) would be associated with behavior problems among children from 2 to 8 years of age. The magnitude of adverse outcomes depends on the timing of the exposure [early vs late pregnancy exposure] and these periods of heightened sensitivity are toxicant-specific. This makes it necessary for researchers to study and understand these periods of heightened vulnerability/window of vulnerability [23]. We sought to identify windows of heightened vulnerability during fetal development using serial blood samples collected during pregnancy and at delivery

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