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Main: Exposure to PBDEs--Research at Boston University School of Public Health

The PBDE/SVOC Research Group at Boston University School of Public Health, Dept. Environmental Health
Our principal focus is the investigation of human exposure to PBDEs in the indoor environment. We have broadened this work to include other semivolatile organic compounds (SVOCs), including new and alternative flame retardants and perfluoroalkyl chemicals (PFCs).

Polybrominated diphenyl ethers (PBDEs)
PBDEs are a class of compounds commonly used as fire retardants in furniture containing polyurethane foam (PUF) and consumer products such as televisions. As shown by their generic chemical structure below, PBDEs are structurally related to their better known cousins: PCBs, polybrominated biphenyls (PBBs), and polychorinated dioxins/dibenzofurans. These compounds are persistent organic pollutants (POPs) and semivolatile organic compounds (SVOCs). Human body burdens and environmental concentrations of PBDEs have increased for several decades and vary geographically, with the highest values reported in the USA. Major questions include impacts on human health and the environment and major routes of human exposure.

Exposure to PBDEs
PBDEs are persistent and bioaccumulative, suggesting exposure via diet, particularly animal products. Given their use in consumer products, it is very likely that the indoor environment also causes exposure. We found associations between PBDE concentrations in people and i) consumption of dairy products and meat, ii) house dust sampled from participant’s homes (Wu et al 2005, 2007); see the figure below. The latter finding--in first time mothers from the Greater Boston area--is particularly important because of the very large uncertainty in adult exposure to dust. It supports the hypothesis that exposure to PBDEs in dust is an important route of exposure.

People are exposed to PBDEs via dust and diet. See: Wu N, Herrmann T, Paepke O, Tickner J, Hale R, Harvey E, La Guardia M, McClean MD, Webster TF. Human exposure to PBDEs: Associations of PBDE body burdens with food consumption and house dust concentrations. Environ Sci Technol 2007; 41(5): 1584-1589. Web release date: 17 Jan 2007. Abstract and full text (for ES&T subscribers): doi=10.1021/es0620282]. See also the accompanying ES&T news report by Kellyn Betts.



The correlation between concentrations of PBDEs in people and in dust cannot, by itself, distinguish between direct exposure to dust (via incidental ingestion or dermal exposure) and inhalation, if the concentrations in air and dust are correlated. Exposure estimates by ourselves (Webster et al 2005) and others suggest that ingestion/dermal exposure to dust is more important than inhalation of indoor air. However, most such calculations rely on indoor air measurements made in rooms using passive air monitors, a method that should underestimate personal exposure. We therefore carried out a second study comparing personal air measurements with room air measurements, using active air pumps (Allen et al., 2007). We found higher concentrations of PBDEs in 'personal air' (sampled near the breathing zone) than in rooms, particularly for decaBDE which is bound to particulate. This is indicative of a personal dust cloud, also known as the Pigpen effect.

We all have our little dust clouds. Read about it in our article: Allen JG, McClean MD, Stapleton HM, Nelson JW, Webster TF. Personal exposure to polybrominated diphenyl ethers (PBDEs) in residential indoor air. Environ Sci Technol 2007; 41(13): 4574-4579. Abstract and full text (for ES&T subscribers): doi=10.1021/es0703170.

Charles Schulz

Sources of PBDEs in the Indoor Environment
PBDEs in indoor air and dust are thought to originate with consumer products such as foam-containing furniture and electronics. However, most earlier research including our own (Wu et al 2007, Allen et al 2007) finds no association between indoor PBDE concentrations and counts of foam-containing furniture and electronics. This could be caused by non-differential exposure misclassification (e.g. large differences in PBDE content between otherwise similar objects), producing a bias toward the null. To deal with this problem, we have used X-ray fluorescence (XRF), providing an easy and quick surrogate measure of the bromine content of household products. This work was published in Environmental Science and Technology in 2008.

News: Read the news story in Environmental Science &Technology about our work with XRF, as presented at BFR07.

"This handheld X-ray fluorescence analyzer allows Joseph Allen of Boston University to detect in seconds the presence of bromine in household products such as televisions."

photo by M. Kenda

Dust sampling: What is to be done?
Dust appears to be an important source of exposure for PBDEs. But there are several important questions about sampling dust:

If you'd like to know more about these issues, read our recent paper: Allen JG, McClean MD, Stapleton HM, Webster TF. Critical Factors in Assessing Exposure to PBDEs via House Dust. Environ Intern 2008; 34: 1085-1091. [Online 5 May 2008]. Abstract and full text (for EI subscribers): doi: 10.1016/j.envint.2008.03.006.



New and alternative BFRs: Deja vu all over again?

Penta and octa have been banned in the US but is the problem solved? There is still enormous amounts of this stuff in people's homes as well as being thrown out. In addition, we've been finding new and alternative brominated flame retardents in dust. Pictured at left is a recently identified component of Firemaster 550, a brominated form of the phthalate DEHP. For more information on FM550, look here.



DBDPE: Another alternative BFR in house dust

Decabromodiphenyl ethane (DBDPE) is another new flame retardant we found in house dust, in collaboration with Heather Stapleton. This and other work was recently profiled in ES&T by Kellyn Betts.



How do PBDEs get from products into dust? Do they off-gas or is the plastic breaking down into little bits? To find out, read our new paper and the accompanying news story "CSI-style tools offer clues about flame retardants in dust."



TDCPP (chlorinated tris): A replacement for pentaBDE

Wonder what is being used in polyurethane foam as a flame retardant now that production of the Penta form of PBDE has been banned? Firemaster 550 is one alternative (above). Another is TDCPP, also known as chlorinated tris. This compound, along with its more famous cousin (brominated tris), were used for a while in kids' pajamas before being removed about 30 years ago. See our new paper.



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PBDE/SVOC Research Group at Boston University School of Public Health, Department of Environmental Health

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email: Dr. Tom Webster

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