83. Prenatal exposure to polybrominated diphenyl ethers (PBDEs) and cognitive ability in early childhood (lay summary)

Azar N, Booij L, Muckle G, Arbuckle TE, Séguin JR, Asztalos E, Fraser WD, Lanphear BP, Bouchard MF. Environment International 2021 Jan;146:106296. doi: 10.1016/j.envint.2020.106296

Polybrominated diphenyl ethers (PBDEs) are a class of chemicals used as flame retardants in electronics, appliances, and furniture. Health Canada has put regulations in place in recent years to limit the use of these chemicals.  People may still be exposed to these chemicals because they do not break down easily in the natural environment and trace amounts are found in foods such as meat and dairy.

Scientists have found that high levels of exposure to these chemicals may affect the development of the nervous system and brain in young children.  We don’t know whether exposure to the low levels of exposure found in Canada might affect children’s neurodevelopment.  We also don’t know whether PBDE exposure affects boys and girls differently.

To answer these questions, researchers at the University of Montreal and Concordia University used data from the MIREC study to investigate the potential impact of prenatal PBDE exposure on childhood IQ scores at age 3. Children participated in tests to measure their verbal, performance, and full-scale IQ.    Each of these tests measures a different aspect of children’s knowledge, reasoning, and intellectual abilities.  PBDE concentrations were measured in blood samples collected during women’s first trimester. Nine PBDEs were measured in maternal plasma but this analysis focused on the 4 PBDEs that were detected in more than 20% of samples.  The investigators used statistical models to relate PBDE exposure and IQ score.

Data on PBDEs and IQ were available for 592 mothers and their children.  The average concentration of the sum of the 4 PBDEs was 12.9 ng/g lipid.  The researchers did not observe any associations between PBDE concentrations and IQ in the overall population.  When the researchers looked at these associations in boys and girls separately, they observed that higher PBDE exposure was associated with a lower IQ in boys but not girls.  This was particularly true for the BDE-47, the congener with the highest concentrations in maternal blood.  A tenfold increase in maternal BDE-47 concentrations was associated, on average, with 4.4 lower Full Scale IQ scores in boys.

In conclusion, this study found that boys may be more susceptible to the effects of early life exposure to PBDEs than girls.   This is one of the first studies to examine this association and it will be interesting to see if future studies report similar results.