Blood levels of polybrominated diphenyl ethers (PBDEs), tested in patients at the UCSF-affiliated San Francisco General Hospital and Trauma Center fell by two-thirds since they were last tested three years ago and found to be the highest levels reported among pregnant women anywhere in the world.
Researchers said the dramatic decline was most likely the result of the statewide ban, as well as a voluntary national phase out. But they said the levels fell more quickly than expected, given how persistently these chemicals remain in the environment once they have been introduced.
“We were pleasantly surprised by the extent of the decline,” said Ami R. Zota, ScD, an assistant professor of environmental and occupational health at the George Washington University School of Public Health and Health Services, and the study’s lead author. Zota conducted the research while she was a postdoctoral fellow at UCSF’s Program on Reproductive Health. “Regulations can have an impact on people’s everyday lives.”
PBDEs were used in foam furniture starting in the 1970s to meet the state’s fire safety regulations, which are now being reviewed. Experiments in animals and also in human cells have shown that PBDEs damage the brain in utero. Researchers have found a strong relationship between an expectant mother’s exposure to the chemicals – even at low levels – and subsequent learning difficulties in her child, including worsened concentration and attention and lower IQ. The chemicals also can disrupt thyroid hormones in adulthood and during development. While much of the data is correlational, the researchers said there is enough evidence to raise serious concern that the chemicals are harmful to people.
PBDEs get into the body in different ways. They easily wear off foam and degrade into household dust, which gets ingested. The chemicals also find their way in through diets rich in fish, meat and dairy products, as PBDEs in the environment are persistent and can accumulate up the food chain. Nursing mothers also pass them to their babies through breast milk.
Previous research has shown that the PBDEs present in California house dust have fallen since the ban. But this is the first time that researchers have shown a decline in PBDEs in people since the chemicals were phased out.
San Francisco General Hospital, the city’s public hospital, serves vulnerable populations, who may be at higher risk for exposure to PBDEs because they are more likely to own older, cheaper furniture and live in poor housing conditions. The researchers compared a group of 25 women who came to the hospital from 2008 to 2009 to 36 women who came between 2011 and 2012. The first group had the highest reported levels of PBDEs of any group of pregnant women tested worldwide. But in just three years, overall levels fell by two-thirds.
Every woman tested from 2008-2009 had all five of the PBDEs measured by the researchers in her blood. But by 2011-2012, only one of the PBDEs was present in every woman tested. The researchers did not test the same women at both time points, but they did find that overall levels of all five PBDE’s were significantly lower in the second group.
Although PBDEs have been banned, furniture makers have substituted other chemicals, which may also be dangerous, as a way of meeting state fire safety standards. Chlorinated Tris, for example, is a suspected carcinogen listed on Proposition 65. Others, such as Firemaster 550, have not adequately been tested.
The findings were published online on Sept. 25 in Environmental Science & Technology.
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