In the 1980s, environmentalists and epidemiologists began to statistically correlate attention problems in children and lower scores on tests with flame retardants used in furniture, chemicals that had become popular because parents and fire departments wanted to prevent "flashover" events during house fires - explosions in closed rooms.

And it worked. But as we have seen with polio and other vaccine preventable diseases, as the threat faded began began to believe it never existed. And activists promoting chemophobia successfully promoted the belief that polybrominated diphenyl ethers (PBDEs) were why kids had behavior problems in school. Though manufacturers used PBDEs as the primary flame retardant chemical in furniture between 1975 and 2004 to comply with fire safety standards, environmentalists successfully promoted the idea that persistence in the environment (being detectable even at trace levels ) was harmful. In response to concern, companies began to stop using pentaBDE in couches, mattresses, carpet padding, and other upholstered products, in 2004. 

Do you want this or exposure to a trace chemical that statisticians try to link to not getting into Harvard?

After PBDEs became a cultural concern, Columbia's Mailman School of Public Health began trying to show environmentalists were right, and they haven't given up. A recent paper in the Journal of Exposure Science and Environmental Epidemiology showed that levels of PBDEs measured in children significantly decreased over a 15-year period between 1998 and 2013. 

So kids no longer have behavioral issues? No, more children are medicated than ever.

To make their claim, they followed 334 mother-child pairs, a specially chosen urban birth cohort study in New York City, from prenatal life through adolescence. Researchers collected umbilical cord blood at birth and blood from the children at ages 2, 3, 5, 7 and 9. Unsurprisingly, after companies stopped using PBDEs, levels of BDE-47, the most frequently detected component of the pentaBDE mixture in humans, decreased by about 5 percent per year from 1998 to 2013. When examining only blood samples collected postnatally, researchers observed a 13 percent decrease per year between 2000 and 2013.

Children that were toddlers (ages 2-3) before the phase-out took effect in 2004-2005, had significantly higher levels of BDE-47 in their blood than children who turned age 2-3 following the phase out. Phase-out aside, 2-3 year olds had the highest concentrations of BDE-47 in their blood than at any other age, possibly because they spend more time on the floor and have more contact with dust at this age.

Though levels of these flame retardants are decreasing over time, they still found PBDEs in every child blood sample. "These findings suggest that while pentaBDE levels have been decreasing since the phase-out, they continue to be detected in the blood of young children nearly 10 years following their removal from U.S. commerce," says first author Dr. Whitney Cowell, pediatric environmental health research fellow at Mt. Sinai and former doctoral student from the Columbia Center for Children's Environmental Health.

"These findings reinforce the decision to phase-out PBDEs from consumer products," says senior author Julie Herbstman, PhD, associate professor of Environmental Health Sciences. "However, it's important to remain vigilant. Since the phase-out of PBDEs, we have begun to detect other flame-retardant chemicals in children, which are likely being used as replacements."