Traces of flame retardants linked to hormonal and neurological disorders in children have declined sharply but remain higher among pregnant women in California than among their peers elsewhere in the nation, a new study shows.
The report published online Wednesday in Environmental Science & Technology is the second to examine levels of exposure to polybrominated diphenyl ethers, or PBDE, among women in their second trimester of pregnancy who attended a clinic in San Francisco General Hospital. The first, published in 2011, found those levels to be the highest ever reported among pregnant women worldwide.
The new findings from 36 women appear to be consistent with those of other recent studies that suggest exposure to PBDE, once used in polyurethane foam in furniture, has declined since a 2004 nationwide phaseout of the compounds.
"Just in this three-year period we saw a striking decline," said lead author Ami Zota of George Washington University. "The levels of PBDEs declined by an average of 65%."
But Zota cautioned that there is no known safe level of PBDE. Prenatal exposure to PBDE has been linked to deficits in cognitive function, fine motor skills and attention spans in children.
The apparent declines in PBDE also may parallel those of such legacy chemicals as PCBs, which at first were steep, then leveled off to a persistent background exposure. That trend was confirmed in the latest study, which showed no significant change in PCB levels among the pregnant women.
The study of 36 women in their second trimester of pregnancy did not examine exposure to chemicals that replaced PBDE, including a class of organophosphates such as chlorinated Tris, or TDCPP, which has been linked to tumors in rats. A state panel two years ago added TDCPP to its list of carcinogens subject to consumer warnings under Proposition 65.
"It's possible that exposure to those chemicals is increasing in these women," Zota said.
Evidence has been accruing that the California ban on PBDE and the subsequent, negotiated phaseout of its use nationwide have diminished consumer exposure. A study last year showed that PBDE concentrations in dust in 16 California homes decreased between 2006 and 2011, and another showed that only 17% of foam samples from couches purchased in California after 2005 had detectable levels of PBDE.