The chemicals were turning up in womens' breast milk and blood (among other places). Since the chemicals can interfere with thyroid function – critical to fetal brain development – scientists worried they were affecting babies' health.
With the ban in place, researchers now wanted to know: How long would it take for PBDEs to stop showing up in womens' bodies?
Scientists began with blood samples collected in 2008-09 from pregnant women being cared for at San Francisco General Hospital. These women had shown some of the highest blood levels of PBDEs ever detected.
In 2011-12, researchers came back to SF General for samples from another group of pregnant women. This time, they found levels less than half of what they’d seen four years earlier.
"What we're seeing is that ban worked," said study co-author Tracey Woodruff, who teaches medicine at UCSF. “We were anticipating we might not see such a dramatic decline, because the chemicals tend to be persistent and accumulate in the environment. They tend to hang around for a while."
Furniture makers currently use other kinds of chemicals to make furniture fire resistant, and thus meet state requirements. Scientists have raised concerns about the safety of these chemicals as well.