A study in this week’s issue of THE LANCET suggests that both prenatal and postnatal exposure to polychlorinated biphenyls-from maternal blood and breastmilk, respectively-can hinder early childhood cognitive development. The study also concludes that a stimulating home environment can counteract this adverse developmental effect.
There is uncertainty whether environmental levels of exposure to polychlorinated biphenyls (PCBs) adversely affect mental and motor development in early childhood. Gerhard Winneke and colleagues from Heinrich-Heine- University, Düsseldorf, Germany, aimed to establish whether such an effect is of only prenatal or additional postnatal origin, and if a favourable home environment could counteract this effect.
The investigators recruited 171 healthy mother-infant pairs and prospectively measured psychodevelopment in newborn infants at 7, 18, 30, and 42 months of age. Prenatal and perinatal PCB exposure of newborn babies was estimated from umbilical-cord blood and maternal milk; postnatal PCB blood concentration was measured at 42 months. At 18 months the quality of the home environment was assessed using the Home Observation for Measurement of the Environment scale. Mental and psychomotor development of the children were assessed using the Bayley Scales of Infant Development until 30 months of age, and the Kaufman Assessment Battery for Children at 42 months.
High concentrations of milk PCBs were associated with lower mental and motor development scores, which were statistically significant from 30 months of age onwards. Across the age range from 7 to 30 months, the Bayley Scales of Infant Development mental scores were 8.3 points lower for infants in the top 5% of PCB exposure compared with the bottom 5%; similarly, there was a 9.1 point decrease in scores for the Bayley Scales of Infant Development motor scores between the same two infant groups. There was also a negative effect of postnatal PCB exposure from breastfeeding at 42 months. Home environment had a significant positive effect from 30 months onwards (Bayley Scales of Infant Development mental score increase of 9.4 points).
In an accompanying Commentary (p 1568), Joseph Jacobson and Sandra Jacobson from Wayne State University, Detroit, USA, state: “It is impressive that at 30 months of age, the deficit associated with PCBs on Bayley Scale scores for mental development (9.9 points) was not much smaller than that associated with low parental HOME scores (17.7 points). At the older age (42 months), the difference between the effects associated with PCB exposure and HOME scores was even smaller. Thus, these data show that the effects of prenatal PCB exposure persist over the course of the child’s development and are similar in size to the well-known and substantial effects associated with quality of parental intellectual stimulation.”
Contact: Dr Gerhard Winneke, Medical Institute of Environmental Hygiene at Heinrich-Heine-University Düsseldorf, Auf’m Hennekamp 50, D-40225 Düsseldorf, Germany; T) +49-211 338 9291; F) +49 211 338 9311; E) gerhard.winneke@uni-dusseldorf.de
Dr Joseph Jacobson, Psychology Department, Wayne State University, Detroit, MI 48202, USA; T) +1 313 875 8550; F) +1 313 577 7636; E) joseph.jacobson@wayne.edu
Journal
The Lancet