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Cognitive development in preschool children prenatally exposed to PCBs and MeHg
Paul W Stewart1, Jacqueline Reihman, Edward I Lonky
1Department of Psychology, State University of New York at Oswego, Oswego, NY 13126, USA. pstewar1@oswego.edu
Insights
Prenatal exposure to polychlorinated biphenyls (PCBs) was linked to temporary cognitive deficits in toddlers. However, children showed catch-up development by preschool age, suggesting potential functional recovery from PCB and mercury exposure.
Area of Science:
- Environmental Health
- Developmental Psychology
- Neurotoxicology
Background:
- Epidemiological studies suggest prenatal exposure to polychlorinated biphenyls (PCBs) may impact cognitive development.
- Conflicting findings exist, necessitating further research to clarify the relationship between prenatal PCB exposure and cognitive deficits.
Purpose of the Study:
- To investigate the association between prenatal polychlorinated biphenyl (PCB) exposure and cognitive development in children.
- To examine potential interactions between prenatal PCB and mercury (MeHg) exposure on cognitive outcomes.
- To assess cognitive development at multiple time points to identify potential recovery trajectories.
Main Methods:
- Assessed 212 children using the McCarthy Scales of Children's Abilities at 38 and 54 months of age.
- Measured prenatal PCB exposure via cord blood and maternal hair mercury (MeHg).
- Controlled for numerous confounding factors including SES, maternal IQ, and education.
Main Results:
- Prenatal PCB exposure predicted minor cognitive deficits at 38 months.
- A significant interaction indicated negative effects of MeHg on cognition were more pronounced with higher PCB exposure.
- No significant associations between PCBs/MeHg and cognitive performance were found at 54 months, with children showing catch-up development.
Conclusions:
- Prenatal PCB exposure may lead to transient cognitive deficits in early childhood.
- Evidence suggests potential functional recovery or catch-up development by preschool age.
- The interaction between PCB and MeHg requires further investigation and replication.
Abstract:
A number of epidemiological studies have shown predictive relationships between prenatal exposure to polychlorinated biphenyls (PCBs) and subtle deficits in cognitive development in infancy through the preschool years [Child Dev. 56 (1985) 853; J. Pediatr. 116 (1990) 38; J. Pediatr. 134 (1999) 33; Toxicol. Lett. 102-103 (1998) 423; Neurotox. 21 (6) (2000) 1029-1038]. However, since not all studies have demonstrated these relationships (J. Pediatr. 119 (1991) 58-63), debate regarding the role of prenatal PCB exposure in cognitive development continues. The current study was designed to provide additional data to assist in resolving this question. Two hundred twelve children enrolled in the Oswego Newborn and Infant Development Project were assessed using the McCarthy Scales of Children's Abilities at 38 months of age, followed by a reassessment at 54 months of age. The relationship between prenatal exposure to PCBs (cord blood PCBs) and McCarthy performance was assessed at both ages after first controlling for a wide range of important predictors of cognitive development, including socioeconomic status (SES), maternal IQ, maternal education, home environment, cigarette smoking, and many others. Cord blood PCBs were statistically significant predictors of small but measurable deficits in McCarthy performance at 38 months of age. Moreover, a significant interaction between cord blood PCBs and maternal hair mercury (MeHg) was found, such that negative associations between prenatal MeHg exposure and McCarthy performance were found in subjects with higher levels of prenatal PCB exposure. No relationship between PCBs and/or MeHg and McCarthy performance was observed when the children were reassessed almost 1.5 years later (54 months of age). Inspection of the age-related trajectory of McCarthy performance revealed that the more highly exposed children caught up with the least exposed children by 54 months. Although the current data partially replicate the findings of Jacobson et al., Patandin et al., and Walkowiak et al. [J. Pediatr. 116 (1990) 38; J. Pediatr. 134 (1999) 33; Lancet 358 (2001) 1602], results reported here suggest that functional recovery may occur. Moreover, the interaction between PCB and MeHg cannot be considered conclusive until it has been replicated in subsequent investigations.