Developmental PBDE Exposure and IQ/ADHD in Childhood: A Systematic Review and Meta-analysis
Juleen Lam1, Bruce P Lanphear2, David Bellinger3
1Program on Reproductive Health and the Environment, University of California , San Francisco, San Francisco, California, USA.
Insights
Developmental exposure to polybrominated diphenyl ethers (PBDEs) is linked to reduced intelligence in children. Preventing exposure to these flame-retardant chemicals may help preserve cognitive function.
Area of Science:
- Environmental health
- Neuroscience
- Toxicology
Background:
- Neurodevelopmental disorders affect 1 in 6 US children.
- Polybrominated diphenyl ethers (PBDEs) are common flame retardants found in children.
- PBDEs are ubiquitous environmental contaminants with potential neurotoxic effects.
Purpose of the Study:
- To systematically review evidence on developmental PBDE exposure and its association with intelligence and ADHD.
- To evaluate the quality and strength of evidence linking PBDEs to neurodevelopmental outcomes.
Main Methods:
- Systematic literature search up to September 2016.
- Inclusion of studies quantifying PBDE exposure during sensitive developmental periods.
- Risk of bias assessment and meta-analysis using the DerSimonian-Laird method.
Main Results:
- Sufficient evidence indicates an association between developmental PBDE exposure and reduced IQ.
- Meta-analysis of four studies showed a 3.70-point IQ decrement per 10-fold increase in PBDE exposure.
- Moderate evidence suggests a link between PBDEs and ADHD, though with limitations.
Conclusions:
- Developmental exposure to PBDEs is associated with lower IQ.
- Reducing PBDE exposure could mitigate losses in human intelligence.
- Further research is needed to confirm the association with ADHD.
Background:
In the United States, one in six children are affected by neurodevelopmental disorders, and polybrominated diphenyl ethers (PBDEs) in flame-retardant chemicals are measured ubiquitously in children.
Objective:
We conducted a systematic a systematic review regarding developmental exposure to PBDEs and intelligence or Attention Deficit/Hyperactivity Disorder (ADHD) and attention-related behavioral conditions in humans.
Methods:
We searched articles published up to 26 September 2016, and included original studies that quantified exposures to PBDEs incurred any time in proximity to conception or during in utero, perinatal, or childhood time periods. We evaluated the risk of bias of individual studies and the overall quality and strength of the evidence according to the Navigation Guide systematic review methodology. We established criteria in advance to identify studies that could be combined using random effects meta-analyses (DerSimonian-Laird method).
Results:
Fifteen studies met the inclusion criteria; 10 studies met the criteria for intelligence and nine for attention-related problems. We rated studies generally with "low" to "probably low" risk of bias and rated the overall body of evidence as "moderate" quality with "sufficient" evidence for an association between Intelligence Quotient (IQ) and PBDEs. Our meta-analysis of four studies estimated a 10-fold increase (in other words, times 10) in PBDE exposure associated with a decrement of 3.70 IQ points (95% confidence interval: 0.83, 6.56). We concluded the body of evidence was of "moderate" quality for ADHD with "limited" evidence for an association with PBDEs, based on the heterogeneity of association estimates reported by a small number of studies and the fact that chance, bias, and confounding could not be ruled out with reasonable confidence.
Conclusion:
We concluded there was sufficient evidence supporting an association between developmental PBDE exposure and reduced IQ. Preventing developmental exposure to PBDEs could help prevent loss of human intelligence. https://doi.org/10.1289/EHP1632.
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