In a sign that California's efforts to reduce health risks from toxic chemicals are having an impact, a type of flame retardant linked to reduced fertility, low IQs in children and thyroid problems has fallen sharply in the blood of pregnant women since the state banned the chemicals 10 years ago.
Concentrations of the chemicals, known as PBDEs, fell by two-thirds in groups of pregnant women tested at San Francisco General Hospital from 2008 to 2012.
"We saw a pretty dramatic decline, indicating the ban appears to work. That's good news," said Tracey Woodruff, director of the UC San Francisco's Program on Reproductive Health.
In past studies, researchers had found that children and pregnant women in California had higher levels of PBDEs in their bodies than in any other state or in Europe.
The reason, researchers say, is a 1975 California law that sets stricter flammability standards for furniture than other states, leading manufacturers to douse their products in flame retardants.
The chemicals had been commonly used in furniture, mattresses, carpets, drapes and other products. But scientists found they were spreading through dust and getting into the food chain, from milk to salmon. The chemicals were also turning up not only in people, but also in animals as far away as the Arctic.
After health concerns began to grow a decade ago, two of the main types of PBDEs were banned in California in 2003 under a law signed by then-Gov. Gray Davis. The only U.S. company that manufactured them, Great Lakes Chemical in Indiana, agreed to a voluntary national phaseout in 2004, and new types of flame retardants have since been used on furniture and other products.
Industry groups downplayed the significance of the new UC San Francisco research.
"The chemicals in this study are a group of PBDEs that were voluntarily phased out by 2004," said Bryan Goodman, a spokesman for the American Chemistry Council, an industry group in Washington, D.C.
"The study only reports the detection of PBDEs and does not associate these levels to potential adverse health effects. We are certainly pleased to see that the researchers have found substantial declines in the levels of PBDEs among the sample of women seen in their clinic. We anticipate that this trend will continue."
This study, published Wednesday in the journal Environmental Science and Technology, comes as California is rewriting its laws for furniture flammability.
Environmental groups and the chemical industry are battling over the new rules, which were ordered by Gov. Jerry Brown last year. Because California is by far the nation's most populous state, the rules could eventually affect all furniture sold in the United States.
Brown ordered the change after a series of stories in the Chicago Tribune showed how the chemical industry had engaged in misleading lobbying over the chemicals, and how the tobacco industry had worked hard to push flame retardant rules so cigarette companies wouldn't be required to develop fire-resistant cigarettes.
The U.S. Consumer Product Safety Commission concluded that PBDEs provide no significant fire protection.
"The old rules were nearly 40 years old. They didn't reflect today's reality," said Russ Heimerich, a spokesman for the California Department of Consumer Affairs.
Under the state's 1975-era rules, polyurethane foam in upholstered furniture and children's products must not burn when exposed to an open flame for 12 seconds. The new draft rules would change that standard to one in which the foam only needs to keep from igniting when exposed to a smoldering cigarette, which is expected to dramatically reduce the amount of chemicals used.
Still in the final drafting stage, the rules are scheduled to take effect Jan. 1, 2015.
The UC San Francisco study was not without its shortcomings. The study tested the blood of 25 pregnant women from around Northern California who came to San Francisco General Hospital in 2008 and 2009 and compared the levels of PBDEs found in them with the levels in 36 pregnant women tested in 2011 and 2012 at the hospital.
The two groups were not the same women. And researchers say they aren't sure why the levels fell so quickly.
Still, they noted, the findings track with other recent studies of dust in homes in California that have shown similar drops in PBDE levels since the ban.
Another type of PBDE used in televisions and other electronics, called deca-BDE, was not banned by California, but will be phased out by the end of 2013 under a voluntary agreement with the two leading companies that produced it and the U.S. Environmental Protection Agency.
Meanwhile this week, a leading medical organization, the American College of Obstetricians and Gynecologists, issued a statement saying that because of growing scientific evidence, more laws are needed to regulate persistent chemicals that are building up in the bodies of children and pregnant women.
"Every pregnant woman in America is exposed to many different chemicals in the environment," said Dr. Jeanne Conry, president of the organization. "Prenatal exposure to certain chemicals is linked to miscarriages, stillbirths and birth defects."
Paul Rogers covers resources and environmental issues. Contact him at 408-920-5045. Follow him at Twitter.com/paulrogerssjmn.