WSU scientist recalls breakthrough
Ten years ago, Patricia Hunt and her colleagues were studying eggs from mice, part of ongoing research into pregnancy failure.
“All of a sudden our data went completely bonkers,” she said.
Hunt began seeing sudden, unexplained changes in the behavior of chromosomes in eggs of healthy mice. What caused it? Weeks of investigation led Hunt to a rather mundane explanation.
“We finally realized what had happened was the cages and water bottles had been inadvertently damaged,” she said.
A harsh cleanser used on the polycarbonate products had left them looking somewhat melted – and allowed a chemical known as bisphenol A, or BPA, to leach out of the plastic. That discovery prompted a new line of research for Hunt, then working at Case Western Reserve University but now at Washington State University.
Her ensuing investigation of BPA is one reason concerns over the chemical have taken center stage as a public health problem.
“It was totally inadvertent,” she said of her entry into the world of BPA research. “It was total serendipity.”
Calls to ban BPA have been intensifying, and they gained traction earlier this month with news Canada intends to prohibit its use in baby bottles. A recent federal report concluded BPA should be considered a possible human health risk while it’s studied further.
All this from a product – polycarbonate plastic – so deeply ingrained in modern life that it could be hard to even begin to extract it. It’s in baby bottles and sippy cups, hard-sided water bottles and eyeglass lenses, dental fillings and the lining of food and beverage containers.
The chemical has been used in the production of light plastics since the 1950s, and in 2004 about 2.3 billion pounds of BPA was produced, according to a draft report prepared by the National Toxicology Program. One study showed that 93 percent of people over age 6 who were tested had BPA in their urine, the report said.
Babies and young children are believed to be at the greatest risk, in part because many baby products are made with polycarbonate and some baby food packaging comes lined with a resin that has BPA. “It’s everywhere,” Mike Shelby, director of the Center for the Evaluation of Risks to Human Reproduction, told the Washington Post. “It’s not clear that we know what all the sources of BPA exposure are. The vast majority of exposure is through food and drink – cans and bottles. But there could be trace amounts in water, dust. Your cell phone is probably made out of it.”
Chemical companies have resisted calls for a ban, arguing that research has not conclusively shown a serious or high-level health risk to humans. Proponents of a ban say scores of studies have shown dramatic and long-term effects in mice, and that while the human link remains to be fully studied, there is reason for caution.
“We just don’t know a lot about how we’re currently being exposed to it and what the levels of exposure are,” Hunt said.
Wal-Mart said last week it plans to begin phasing out the products containing BPA in its U.S. stores, and Nalgene – maker of the ubiquitous hard-plastic, wide-mouth water bottles – said it would stop using the product and recall bottles already in stores.
Hunt’s research has focused on egg development in mammals and the development of chromosomal problems. Once she and her team figured out the problem with the cleanser and cages, back in 1998, she began researching the effects of BPA on the mice.
She said she proceeded with caution, given the widespread impact the findings could have. By 2003, though, she was ready to publish research showing that the chemical appeared to cause chromosomal abnormalities in the eggs of adult female mice.
Such abnormalities typically lead to miscarriage or conditions such as Down syndrome in humans.
Hunt then studied the effects of the chemical on more than one generation of mice, discovering that when pregnant mice were exposed to low levels of BPA, 40 percent of the developing eggs in the fetus – the future grandchildren of the mother – showed chromosomal abnormalities. The normal rate of such abnormalities is 1 percent to 2 percent.
“We’ve essentially exposed three generations with one exposure,” she said.
That multigenerational effect echoes research on the long-term effects of environmental pollution being done by another WSU scientist, Michael Skinner. Skinner’s work has shown a variety of “epigenetic” effects from exposure to toxins – meaning that the exposure changes the DNA of the exposed mammal and its descendants for several generations. His latest work was named one of the top 100 science stories of 2007 by Discover magazine.
Hunt was similarly honored last year by Scientific American, being named one of the country’s top 50 researchers of the year for her most recent work on BPA.
The honors are nice, she says, and the spotlight on BPA in recent months has put Hunt in the unfamiliar role of media subject. But the work has left her concerned – not just about BPA, but about similar chemicals throughout the environment. Such “endocrine disruptors” mimic the behavior of hormones or interrupt hormonal functions, and they can exert a lifelong influence on developing cells, she said.
Other endocrine disruptors are used in plastics, as well as pesticides and herbicides.
Hunt says she’s gotten rid of most plastic in her kitchen, and uses glass as much as possible. The plastics she does use never see the inside of a microwave or dishwasher – as heat is one way to release chemicals in plastic.
“This chemical scares me,” she said. “I want it out of my life because I don’t want it leaching into my food.”