Does background postnatal methyl mercury exposure in toddlers affect cognition and behavior?

Area of Science:

• Environmental Health
• Neuroscience
• Pediatrics

Background:

• Mercury (Hg) poses significant toxicological risks to the developing central nervous system in children.
• Concerns are rising regarding prenatal and early childhood exposure to mercury.

Purpose of the Study:

• To examine the association between postnatal methylmercury (MeHg) exposure and cognitive and behavioral outcomes in children.
• To assess the impact of MeHg exposure in the context of lead (Pb) exposure.

Main Methods:

• Analyzed blood samples for MeHg concentrations in 780 children from the Treatment of Lead-exposed Children (TLC) trial.
• Assessed children's IQ and neurobehavioral performance at ages 2, 5, and 7 years.
• Utilized stratified, spline regression, and generalized linear models, adjusting for blood lead (PbB) levels.

Main Results:

• No significant adverse effects of MeHg on IQ or behavior were detected at current U.S. background exposure levels.
• Weak, non-significant positive associations were observed between MeHg and IQ scores.
• Blood lead (PbB) levels were strongly associated with lower IQ and behavioral problems.
• MeHg effects on neurodevelopment were not substantially different across varying PbB levels.

Conclusions:

• Current background postnatal MeHg exposure levels in U.S. children do not show detectable adverse effects on IQ and behavior.
• Lead exposure remains a significant concern for neurodevelopmental outcomes in children.
• Further research may be warranted to understand long-term or higher exposure effects.