Polybrominated Diphenyl Ethers
CATEGORY*: IARC probable carcinogen, NTP reasonably anticipated carcinogen, endocrine disruptor
FOUND IN: furniture, electronics
THE GIST: We’re exposed to these chemicals every day. They’re found in furniture, televisions, computers and toasters. They leach out into homes and the environment and bioaccumulate in us. Research indicates that PBDEs disrupt hormones, creating a risk factor for breast cancer. In addition, these chemicals have been linked to neurobehavioral conditions. Firefighters face a particularly high risk for exposure to these chemicals, which are structurally similar to banned PCBs.
State of the Evidence on Polybrominated Diphenyl Ethers
PBDEs are a complex group of chemicals that are structurally similar to the polychlorinated biphenyls (PCBs). They are used extensively as fire retardants in both consumer and industrial products (Costa, 2008). Products containing PBDEs include polyurethane foam in furniture (treated with penta-BDE) and electronic and plastic products (treated with octa- and deca-BDEs) (Zota, 2008).
TIPS FOR PREVENTION
Reduce your exposure to household dust containing PBDEs by washing hands frequently, dusting with a wet cloth and seeking out furniture made without flame retardants.More tips for avoiding PBDEs >
Although both penta- and octa-BDEs have been banned in the European Union and have not been produced in the United States since 2004, products containing them remain throughout the world. PBDEs are found ubiquitously in the environment and are detected in air, dust, soil and food, as well as in many wildlife species. Although home exposures (as measured by dust levels) have decreased over the past decade, levels remain high enough to remain a serious health concern (Dobson, 2012).
There is considerable geographic variability in exposures to the chemicals; people in California, with its particularly stringent furniture flammability standards, have much higher levels of PBDE exposures than do people in Massachusetts. Within the California group, lower socioeconomic status is associated with higher PBDE levels (Petreas, 2011; Zota, 2008). Mexican Americans living in California have significantly higher PBDE levels in blood serum than do Mexicans living in their homeland (Eskenazi, 2011).
Data from young girls (ages 6 to 9) from California and Ohio support these findings. Although PBDEs were found in almost all samples tested, girls in California had significantly higher blood serum PBDE levels than did girls from Ohio, and young African American girls had higher levels than either white or Hispanic girls (Windham, 2010).
These chemicals are endocrine-disrupting compounds, exerting effects on a number of hormonal systems, including the androgens, progestins and estrogens, though the major system affected by PBDEs is the thyroid hormone system (Costa, 2008). Most studies of health outcomes after PBDE exposures have focused on neural development, given the prominent role of thyroid hormones (especially T4) in regulating brain development (Costa, 2007; Talsness, 2008).
Very few data directly address the possible effects of PBDEs on breast cancer risk. One case-control study found no relationship between breast fat PBDE levels and breast cancer risk, but the sample was small and the chemical analysis was done around the time of diagnosis of breast cancer in the women who developed the disease (Hurley, 2011). However, at least some PBDEs have been shown to be as effective as many of the other endocrine-disrupting compounds in promoting estrogenic-like proliferation of human breast cancer cells in vitro (Meerts, 2001). More recent data on human breast tumor cells (MCF-7 cells)indicate that penta-BDE enhances tumor-cell proliferation through estrogen-like effects on cell pathways that interrupt programmed cell death, or apoptosis (Yu, 2009). The cell-proliferative and anti-apoptotic effects of PBDEs are additive with those of natural estradiol (Kwiecinska, 2011) and counteract the anti-cancer effects of Tamoxifen in cultured breast cancer cells (Li, 2012). Given the extensive overlap and interaction of estrogen-mediated and thyroid-mediated responses in the regulation of breast cancer (Davis, 2009), PBDEs will be a class of chemicals of continued concern for scientists interested in understanding environmental links to breast cancer (Birnbaum, 2009).
Even as PBDEs are being used less often as fire retardants in common consumer products, there is now evidence that the chamicals being used as substitutes – including Firemaster 550, a common substitute – are increasingly contaminating our environment (Dobson, 2012; Patisaul 2013). Although the physiological effects of exposures to Firemaster 550 have not yet been studied extensively, one study demonstrated that feeding mother rats low doses during pregnancy and lactation led to changes associated with exposures to other endocrine disrupting compounds. These effects included changes in thyroid hormone levels in the mothers, and changes in behavior, weight gain and earlier puberty in female pups (Patisaul, 2013).
*For chemicals that have been shown to be carcinogens, we provide classifications from two authoritative bodies: the International Agency for Research on Cancer (IARC, an international body) and the National Toxicology Program (NTP, a division of the U.S. Department of Health and Human Services). We have categorized endocrine-disrupting compounds where the body of peer-reviewed research indicates a strong foundation for doing so.