Background: Evidence of neurological, cognitive, and neuropsychological effects of
manganese (Mn) exposure from drinking water (WMn) in children has generated widespread
public health concern. At elevated exposures, Mn has been associated with increased
levels of externalizing behaviors, including irritability, aggression, and impulsivity.
Little is known about potential effects at lower exposures, especially in children.
Moreover, little is known regarding potential interactions between exposure to Mn
and other metals, especially arsenic (As).
Objectives: We conducted a cross-sectional study of 201 children to investigate associations
of Mn and As in tube well water with classroom behavior among elementary school children,
8–11 years of age, in Araihazar, Bangladesh.
Methods: Data on exposures and behavioral outcomes were collected from the participants
at the baseline of an ongoing longitudinal study of child intelligence. Study children
were rated by their school teachers on externalizing and internalizing items of classroom
behavior using the standardized Child Behavior Checklist-Teacher’s Report Form (CBCL-TRF).
Results: Log-transformed WMn was positively and significantly associated with TRF
internalizing [estimated β = 0.82; 95% confidence interval (CI), 0.08–1.56; p = 0.03], TRF externalizing (estimated β = 2.59; 95% CI, 0.81–4.37; p =0.004), and TRF total scores (estimated β = 3.35; 95% CI, 0.86–5.83; p = 0.008) in models that adjusted for log-transformed water arsenic (WAs) and sociodemographic
covariates. We also observed a positive monotonic dose–response relationship between
WMn and TRF externalizing and TRF total scores among the participants of the study.
We did not find any significant associations between WAs and various scales of TRF
Conclusion: These observations reinforce the growing concern regarding the neurotoxicologic
effects of WMn in children.
Background: Prenatal exposure to methylmercury (MeHg) and polychlorinated biphenyls
(PCBs) has been associated with impaired performance on attention tasks in previous
studies, but the extent to which these cognitive deficits translate into behavioral
problems in the classroom and attention deficit/hyperactivity disorder (ADHD) remains
unknown. By contrast, lead (Pb) exposure in childhood has been associated with ADHD
and disruptive behaviors in several studies.
Objectives: In this study we examined the relation of developmental exposure to MeHg,
PCBs, and Pb to behavioral problems at school age in Inuit children exposed through
their traditional diet.
Methods: In a prospective longitudinal study conducted in the Canadian Arctic, exposure
to contaminants was measured at birth and at school age. An assessment of child behavior
(n = 279; mean age = 11.3 years) was obtained from the child’s classroom teacher on
the Teacher Report Form (TRF) from the Child Behavior Checklist, and the Disruptive
Behavior Disorders Rating Scale (DBD).
Results: Cord blood mercury concentrations were associated with higher TRF symptom
scores for attention problems and DBD scores consistent with ADHD. Current blood Pb
concentrations were associated with higher TRF symptom scores for externalizing problems
and with symptoms of ADHD (hyperactive-impulsive type) based on the DBD.
Conclusions: To our knowledge, this study is the first to identify an association
between prenatal MeHg and ADHD symptomatology in childhood and the first to replicate
previously reported associations between low-level childhood Pb exposure and ADHD
in a population exposed to Pb primarily from dietary sources.