Sucking up data with the Big Shark
ES&T’s first runner-up environmental science paper of 2005 presents new insights gleaned from house dust.
“Polybrominated Diphenyl Ethers in House Dust and Clothes Dryer Lint” by Heather M. Stapleton, Nathan G. Dodder, Michele M. Schantz, and Stephen A. Wise, U.S. National Institute of Standards and Technology; and John H. Offenberg, U.S. Environmental Protection Agency, 2005, 39 (4), 925–931.
In the fall of 2003, Heather M. Stapleton was vacuuming her apartment in a Maryland suburb of Washington, D.C., when it dawned on her that—in addition to her pet rabbit’s fur, her long blond hairs, and the other dust and dirt—her vacuum could be sucking up PBDEs (polybrominated diphenyl ethers). These compounds, which are widely used as flame retardants in household products, are suspected to be endocrine disrupters. As a postdoctoral researcher at the U.S. National Institute of Standards and Technology (NIST) who had been researching PBDEs for 3 years, she was in an ideal position to analyze her own home’s dust. When testing revealed that her home had “really high” concentrations of the compounds, the project that led to this top 2005 ES&T publication was born.
Stapleton’s next step was to purchase a vacuum suitable for the project. She found her ideal tool at a home improvement store: a silver-gray-colored commercial vacuum called the “Big Shark”, which is about the size of an American football. Besides being portable, its main appeal as a collecting tool wais “that it was easy to use, disassemble, and clean between each use, and didn’t have a lot of components that could potentially contaminate the sample,” Stapleton says. Thus equipped, Stapleton began collecting dust samples from friends and colleagues in the Washington, D.C., area.
“The big surprise was that the concentrations, on average, that we found were similar to the concentrations you find in sewage sludge and biosolids,” she recalls. She also found higher-than-expected concentrations of the relatively large PBDE compounds associated with the Deca flame retardant formulation in some of the 17 homes she tested. At the time, Deca was one of three major commercial PBDE formulations, but it is now the only formulation still being sold in the U.S. and the EU.
In 2003, Stapleton “didn’t know anyone who had actually looked [for PBDEs in] house dust.” A literature search revealed that Wilhelm Knoth from Germany’s Federal Environmental Agency in Langen had studied levels in European homes, but—in keeping with the much lower body burdens being found in Europeans—the levels were an order of magnitude lower than those Stapleton was finding. While she and her colleagues were analyzing their data, other reports of PBDEs in U.S. house dust began to come out. But their study was ultimately one of the earliest to be published in the peer-reviewed literature. It was the first to report PBDEs in dryer lint as a means of determining how the compounds were getting into dust.
Stapleton is quick to acknowledge that the timing of the paper’s publication played a big role in its popularity. The paper was published at a time when it was becoming clear that PBDEs were different than most other persistent organic pollutants (POPs) in that exposure from diet alone could not account for the high levels that some people—particularly in North America—were taking up. Indoor air and dust became the most likely suspects.
Stapleton and her colleagues also did some research into how people are exposed to PBDEs from dust. Coauthor Nathan G. Dodder of NIST played a key role in these calculations, which took advantage of his experience in previous studies showing that the routes by which people are exposed to PBDEs vary significantly throughout their lifetimes. Ultimately, the researchers collaboratively determined that because toddlers aged 1–4 generally eat quite a bit more dust than the adult population, they get a much higher dose of PBDEs—120 to 6000 nanograms per day, on average, according to their calculations. In this respect, PBDEs are similar to lead, Stapleton points out.
This research strongly suggests that some toddlers could be taking up sufficiently high levels of PBDEs to warrant public-health concerns, Stapleton points out. “I’m surprised that more studies haven’t been done to examine [PBDE] levels in children. It seems important to me that we determine the body burdens of PBDEs in children and infants, who may be more sensitive to any adverse effects,” she says.
Stapleton is now on staff at Duke University’s Nicholas School of the Environment and Earth Sciences, where she is focusing on another research interest: whether the compounds in dust associated with the Deca formulation are breaking down to create smaller and potentially more toxic compounds, such as the ones associated with PBDE formulations that have been discontinued or banned. In the coming months, she hopes to investigate what happens when dust containing these Deca compounds is exposed to sunlight.
