Abstract
Attention Deficit/Hyperactivity Disorder (ADHD) affects 5%–8% of children in the U.S. (10% of males and 4% of females). The contributions of multiple metal exposures to the childhood behavioral deficits are unclear, although particular metals have been implicated through their neurotoxicity. The objective of this study was to test the hypothesis that the body burden of Mn is positively correlated with ADHD symptoms. We also investigated the putative roles of Ca, Fe, Pb, and Hg. We collected shed molars from 266 children (138 boys and 128 girls) who lost a tooth between 11 and 13 years of age. The molars were analyzed for metals using ICP-OES. The third grade teacher of each child completed the Teacher’s Disruptive Behavior Disorders Rating Scale (DBD) to produce a score for “Total Disruptive Behavior” and subscale scores for “Attention Deficit Hyperactivity Disorder”, Hyperactivity/Impulsivity, Inattention, and Oppositional/Defiant. The mean Mn, Fe, Pb and Ca concentrations found in teeth was 3.1 ± 2.9 µg/g, 11.4 ± 12.1 µg/g, 0.5 ± 0.7 µg/g, and 3.0 × 105 ± 0.8 × 105 µg/g, respectively. Hg was not detected. No significant association was found between Mn and behavioral deficits. Ca was significantly negatively associated, and Pb showed a significant positive association with Hyperactivity/Impulsivity, Inattention, and Oppositional/Defiant Disorders. These findings call into question the putative independent association of manganese exposure and behavioral deficits in children, when the balance of other metallic burden, particularly Ca and Pb burdens play significant roles.
Highlights
Attention-Deficit/Hyperactivity Disorder (ADHD) affects 5%–8% of children in the United States (10% of males and 4% of females) (CDC 2002)
The Disruptive Behavior Disorders Rating Scale (DBD) scale was derived from the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) and produces a Total Disruptive Behavior Score as well as subscale scores for ADHD, Inattention, Hyperactivity/Impulsivity, and Oppositional Defiance [56,57]
Linear regression models indicated no significant association between the behavioral deficit scores and the concentrations of metals in teeth, with the exception of Ca (Table 3)
Summary
Attention-Deficit/Hyperactivity Disorder (ADHD) affects 5%–8% of children in the United States (10% of males and 4% of females) (CDC 2002). A definitive cause of ADHD has yet to be discovered, but some of the most promising research on the etiology of ADHD involves investigating the associations between the disorder and exposure to environmental risk factors. One of the potential risk factors is exposure to environmental manganese [1,2]. Manganese (Mn) is a ubiquitous and naturally occurring element found in certain rocks, making up about 0.1% of the earth’s crust [3]. Pure Mn does not occur naturally, but is a component of more than 100 minerals formed when Mn combines with other substances such as oxygen, sulfur, and chlorine. The National Research Council recommends a safe and adequate daily intake level of 5 mg/day for adults [12]. The Food and Nutritional Board of the National Research Council considers daily intake levels of 0.3 to
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