New York, Jan 13 (IANS): Researchers have found that prenatal exposure to flame retardants may increase the risk of reading problems.

For the study, published in the journal Environmental International, 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.

"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," said study researcher Amy Margolis from Columbia University Vagelos College of Physicians and Surgeons in the US.

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

According to the study, the research team analysed 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.

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, the researchers said.

"Our findings suggest that the effects of exposure are present in the brain before we can detect changes in behaviour," Margolis said.

"Future studies should examine whether behavioural interventions at early ages can reduce the impact of these exposures on later emerging reading problems," Margolis added.