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Updated: Aug 17, 2026
Long-term Behavioral and Reproductive Consequences of Embryonic Exposure to Low-dose Toxicants
Published on: March 6, 2018
In utero exposure to background levels of polychlorinated biphenyls and cognitive functioning among school-age
Kimberly A Gray1, Mark A Klebanoff, John W Brock
1Division of Extramural Research and Training, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC 27709, USA.
Insights
Prenatal exposure to Polychlorinated biphenyls (PCBs) was not linked to lower intelligence quotient (IQ) scores in children at age 7. This study found no association between background PCB levels and childhood cognitive development.
Area of Science:
- Environmental Health
- Neuroscience
- Pediatrics
Background:
- Polychlorinated biphenyls (PCBs) are widespread environmental pollutants.
- Previous research suggests a link between in utero PCB exposure and impaired cognitive function in children.
- However, this association has not been consistently observed across all studies.
Purpose of the Study:
- To investigate the relationship between prenatal exposure to background levels of PCBs and children's intelligence quotient (IQ) scores.
- To assess cognitive development at age 7 years in relation to maternal PCB levels during pregnancy.
Main Methods:
- Utilized data from the Collaborative Perinatal Project (1959-1965).
- Analyzed third-trimester maternal serum for PCB levels in 732 randomly selected women and 162 with extreme IQ scores in their children.
- Examined the association between PCB levels and IQ scores using multivariate models.
Main Results:
- The mean IQ score for the lowest PCB exposure group (<1.25 microg/liter) was 93.6.
- The mean IQ score for the highest PCB exposure group (>=5 microg/liter) was 97.6.
- No statistically significant association was found between in utero PCB exposure and IQ at age 7 (increase of 0.22 IQ points per microg/liter increase in PCB, 95% CI: -0.28, 0.71).
Conclusions:
- In utero exposure to background levels of PCBs was not associated with lower IQ scores at age 7 in this cohort.
- These findings suggest that typical environmental PCB exposures may not negatively impact childhood cognitive development.
- Further research may be needed to explore potential thresholds or specific PCB congener effects.
Abstract:
Polychlorinated biphenyls (PCBs) are ubiquitous environmental contaminants. In utero exposure to background levels of PCBs has been associated with intellectual impairment among children in most, but not all, studies. The authors evaluated prenatal PCB exposure in relation to cognitive test (intelligence quotient (IQ)) scores on the Wechsler Intelligence Scale for Children at age 7 years. Pregnant women were recruited from 12 US study centers from 1959 to 1965, and their children were followed until age 7 years (the Collaborative Perinatal Project). Third trimester serum was analyzed for PCBs in 1997-1999 for 732 women selected at random and for an additional 162 women whose children had either a low or a high IQ score. The PCB-IQ association was examined in multivariate models. Among those in the lowest exposure category (<1.25 microg of PCB/liter of serum), the fully adjusted mean IQ score was 93.6 (standard error: 1.8); among those in the highest category (> or =5 microg of PCB/liter), the mean IQ was 97.6 (standard error: 1.2); and overall the increase in IQ per unit increase in PCB level (microg/liter) was 0.22 (95% confidence interval: -0.28, 0.71). In these data, in utero exposure to background levels of PCBs was not associated with lower IQ at age 7 years.
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