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September 2011

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Highest levels of flame retardant chemicals reported in California pregnant women

By Linh Pham
September 2011

Ami R. Zota, Sc.D.

Zota attributes the high PBDE levels in pregnant women to California's strict flammability regulations that led manufacturers to add flame retardants to a wide variety of products from electronics to furniture, between the 1970s and 2004. She has studied PBDEs since 2008 (see story( and has co-authored a number of studies on the topic. (Photo courtesy of Ami Zota)

Tracey Woodruff, Ph.D.

Woodruff's group found that low-income populations are exposed to higher levels of PBDEs. (Photo courtesy of Tracey Woodruff)

In a new study, funded in part by NIEHS, a team of scientists reported very high levels of polybrominated diphenyl ethers (PBDEs) and their hydroxylated metabolites (OH-PBDEs) among California pregnant women. Median levels of certain PBDEs and OH-PBDEs were the highest reported to date among pregnant women worldwide.

PBDEs are ubiquitous and persistent flame retardant chemicals found in the environment. Exposure to them during pregnancy poses a public health concern because the chemicals have been linked with neurodevelopmental defects and hormone disruption, according to the authors of the study.

The findings( Exit NIEHS appeared online Aug. 10 in Environmental Science and Technology, the result of collaboration among scientists from the University of California, San Francisco (UCSF), the University of Massachusetts Amherst, and the California Department of Toxic Substances Control.

Exposure to PBDE linked with defective thyroid hormone signaling

Quoted in a UCSF press release( Exit NIEHS, senior author Tracey Woodruff, Ph.D., said, “These important results, showing that pregnant women in this California population are exposed to high levels of certain flame retardants, is a key part of our work to understand and address multiple chemical exposures that occur during this sensitive time period.” Woodruff( Exit NIEHS is director of the UCSF Program on Reproductive Health and the Environment, part of the UCSF Department of Obstetrics, Gynecology, and Reproductive Sciences.

According to the authors, exposure to flame retardants is a major concern, because people are continuously exposed due to bioaccumulation in the environment. In an interview(,0,3525222.story) Exit NIEHS with the Los Angeles Times the day the study was published, Ami R. Zota, Sc.D.,( Exit NIEHS a postdoctoral fellow at UCSF and primary author of the paper, stressed, “It's very hard to avoid our exposures to these products because they're so widespread. Ultimately, we need policy measures.”

Health disparities of PBDE exposure

Data from this study also support previous findings that U.S.-born low-income populations are more likely to have higher levels of flame retardant chemicals. Economic disparities like this are likely due to older PDBE-treated furniture and poorer housing quality. 

As furniture, carpeting, and other household items age, flame retardants are released into the air and dust. California homes have some of the highest reported levels of PBDE chemicals in their household dust. “Blood levels of flame retardant chemicals are two times higher for California residents than for people in the rest of the country,” noted Zota, “likely because our state has the most restrictive flammability requirements nationally.”

A cohort of women in their second trimester

The team analyzed serum samples collected between 2008 and 2009 from 25 second trimester pregnant women for concentrations of lower- and higher-brominated PDBEs, OH-PBDEs, thyroid-stimulating hormone, free thyroxine, and total thyroxine. This is one of the first studies to measure the hydroxylated metabolites in pregnant women, and also one of the first to examine associations between OH-PBDEs and thyroid hormone disruption. According to the authors, another of several strengths of the study is its focus on a vulnerable, but understudied, population of ethnically diverse and predominately low-income women.

Although the data are preliminary and the sample size limited, the researchers found that higher levels of PBDE were associated with thyroid hormone disruption in pregnant women. Because thyroid hormone is important for pregnant women's health and child development, studying this connection further will be of great importance. “This pilot study lays the basis for larger studies to examine the inter-relationships between PDBEs and OH-PDBEs, TH [thyroid hormone] signaling during pregnancy, and adverse maternal and child health outcomes,” the scientists concluded.

In addition to a supplement to an NIEHS grant and an NIEHS career development award, this study was also supported by the Passport Foundation Science Innovation Fund and the Learning Disabilities Association of America.

Citation: Zota AR, Park JS, Wang Y, Petreas M, Zoeller T, Woodruff TJ.( Exit NIEHS 2011. Polybrominated diphenyl ethers (PBDEs), hydroxylated PBDEs (OH-PBDEs), and measures of thyroid function in second trimester pregnant women in California. Environ Sci Technol; doi: 10.1021/es200422b [Online 10 August 2011].

(Linh Pham, Ph.D. is on detail to the Program Analysis Branch of the Division of Extramural Research and Training.)

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