Does Danger Lurk in Your Carpet and Cell Phone?
New Faculty Member Heather Stapleton Studies the Risks Posed by Flame-Retardant Chemicals in the Environment
by Tim Lucas
They’re in your carpet. And your mattress. And the cushions of that sofa you love to lounge on.
You come into contact with them each time you use your cell phone. Or send an e-mail. Or take a drive in your car.
For more than 30 years, polybrominated diphenyl ethers— or PBDEs, for short—have been among the most common flame-retardant chemicals used in North America and Europe. When exposed to high heat or flame, they release bromines that rob the air of the oxygen needed to start or feed a fire.
Manufacturers add the quick-acting coatings to toys, electronics, mattresses, seat cushions, carpet padding and a long list of other plastic, foam or fabric products found in our homes, cars and offices.
The beauty of PBDEs is that they’re designed to last the lifetime of these products.
The problem is, they persist in the environment much longer.
“When people throw away computers, cell phones or electronic games, the PBDEs they contain end up in the dump,” says Heather Stapleton, assistant professor of environmental chemistry at the Nicholas School. The bromines, which are similar in structure to PCBs and dioxins, aren’t chemically bound to the products, but merely dissolved onto them. They evaporate or leach out into surrounding ecosystems and can be carried hundreds, or even thousands, of miles away by tides, currents and winds, she says. They are also released, through normal wear and tear, from products still in use in our homes and cars.
Studies show PBDEs are rapidly accumulating in aquatic food webs and human environments across much of the northern hemisphere.
The question is: What dangers do they pose? Is the risk the same for people who inhale PBDEs primarily through dust as it is for species in the wild that ingest them chiefly through diet? Stapleton is working to find answers.
A soft-spoken, quietly competitive native of upstate New York whose interest in environmental chemistry was sparked by a childhood fascination with marine science, she’s in the vanguard of international research efforts to learn more about PBDEs’ toxicity and long-term fate in the environment.
Her research focuses on identifying the underlying factors that influence exposure and accumulation of PBDEs in aquatic organisms, and, increasingly, on human exposures as well.
“Do bromines pose risks for people? It’s hard to say, because the toxicology is still being investigated,” Stapleton says, choosing her words with obvious care. “But close scrutiny is warranted, because from studies on fish and other model organisms, we know these are very persistent and bioaccumulative chemicals that can be converted into more toxic compounds as they move up the food web.”
Despite her youth—she received her doctoral degree from the University of Maryland in 2003—her words carry weight.
In papers published in 2004 and 2005 while she was a postdoctoral researcher at the National Institute of Standards and Technology, Stapleton became the first scientist to document that fish possess enzymes capable of metabolizing the most commonly used flame-retardant, known as deca-BDE, into compounds found in two of its more toxic and persistent cousins, penta- and octa-BDE.
“That was novel,” she recalls with pride. “Now, we’re working on the next questions: Which enzymes, specifically, are causing the change? And can it also occur in humans?”
To answer these, Stapleton, who joined the Nicholas School faculty in September 2005, is conducting studies on human cell fractions as well as fish.
Preliminary results are promising. “It may be thyroid hormone enzymes,” she says. “If so, that has implications for endocrine activity and other important functions. But there’s still a lot of work to do before we know for sure.”