Prenatal exposure to flame retardants linked to reading problems

The study was published in the January 2020 print edition of Environmental International.

An estimated 2 million children have learning disorders; of these, about 80% have a reading disorder. Genetics account for many, but not all, instances of reading disorders.

In the current study, the researchers hypothesized that in utero exposure to polybrominated diphenyl ethers (PBDEs) -- a type of flame retardant that is known to have adverse effects on brain development -- might alter the brain processes involved in reading. (While use of PBDEs has been banned, exposure to the compounds is still widespread because they do not degrade easily in the environment.)

The research team analyzed neuro-imaging data from 33 5-year-old children -- all novice readers -- who were first given a reading assessment to identify reading problems. They also used maternal blood samples, taken during pregnancy, to estimate prenatal exposure to PDBEs.

The researchers found that children with a better-functioning reading network had fewer reading problems. The also showed that children with greater exposure to PDBEs had a less efficient reading network.

However, greater exposure did not appear to affect the function of another brain network involved in social processing that has been associated with psychiatric disorders such as autism spectrum disorder.

"Since social processing problems are not a common aspect of reading disorders, our findings suggest that exposure to PDBEs doesn't affect the whole brain -- just the regions associated with reading," says Amy Margolis, PhD, assistant professor of medical psychology in the Department of Psychiatry at Columbia University Vagelos College of Physicians and Surgeons.

Although exposure to PDBEs affected reading network function in the 5-year-olds, it did not have an impact on word recognition in this group. The finding is consistent with a previous study, in which the effects of exposure to the compounds on reading were seen in older children but not in emergent readers. "Our findings suggest that the effects of exposure are present in the brain before we can detect changes in behavior," says Margolis. "Future studies should examine whether behavioral interventions at early ages can reduce the impact of these exposures on later emerging reading problems."

The paper is titled "Functional Connectivity of the Reading Network is Associated with Prenatal Polybrominated Diphenyl Ether Concentrations in a Community Sample of 5 Year-Old Children: A preliminary study."

Additional authors are Sarah Banker (Columbia University Irving Medical Center, New York, NY), David Pagliaccio (CUIMC), Erik De Water (Icahn School of Medicine at Mount Sinai, New York, NY), Paul Curtin (Icahn School of Medicine), Anny Bonilla (Icahn School of Medicine), Julie B. Herbstman (CUIMC), Robin Whyatt (CUIMC), Ravi Bansal (University of Southern California, Los Angeles, CA), Andreas Sjödin (Center for Disease Control and Prevention, Atlanta, GA), Michael P. Milham (Child Mind Institute, New York, NY), Bradley S. Peterson (USC), Pam Factor-Litvak (CUIMC), Megan K. Horton (Icahn School of Medicine).

This work was supported by funding from the National Institute for Environmental Health Sciences (K23ES026239 to A.E.M., R00 ES020364 to M.K.H; R21 ES016610-01 to R.W.)