Animal research at the University of Alabama at Birmingham is resurrecting cancer concerns about a plastic additive commonly used in consumer products, including baby bottles, water bottles and the linings of cans.
Coral A. Lamartiniere, a top toxicologist and senior scientist at UAB's Comprehensive Cancer Center, said low levels of bisphenol-A, BPA, given orally to rodents caused tumors and genetic changes consistent with early stages of cancer growth.
Much of the research, performed over the past six years, is being prepared for review and publication, but a key paper on BPA was published last week in the journal Environmental Health Perspectives.
"The inference here is this compound could predispose humans toward breast cancer," said Lamartiniere, who led the study.
The U.S. National Toxicology Program raised public concern about BPA on April 14, reporting that high dose levels of the compound created health hazards in laboratory animals. The agency said some concern was warranted for human fetuses, children and girls approaching puberty.
But the agency noted that the threat was only possible and not certain. Critical evidence was missing, including good studies showing the impact of low doses of BPA on lab animals and humans, the agency reported.
Shortly thereafter, the Food and Drug Administration reassured the public that products containing BPA were safe, but noted that alternative products without BPA were available.
In testimony before Congress in May, the spokesman for the American Chemistry Council, an industry organization, said only traces of BPA could be found in products, and the compound has been used for decades and widely studied for safety.
"Recent media attention has created public concern and confusion about some of these chemicals," Steven G. Hentges, a scientist with the council, told a Senate subcommittee.
Lamartiniere said there was no doubt about his study results, and animals were tested at concentrations of BPA similar to exposures experienced by people.
"In fact, it's below the concentration that the EPA deems safe," he said. "With BPA we're finding changes that are consistent with oncogenisis, or cancer causation."
In the study published last week, Lamartiniere and colleagues gave female rats with nursing litters oral doses of BPA. The result: The baby rats matured with higher levels of breast cancer.
The issue of plastic additives and health goes far beyond cancer, and into a new scientific frontier created by technology allowing researchers to view genetic changes caused by chemicals.
"It's amazing how every compound has a genetic signature," said Dr. Jose Russo of the Fox Chase Cancer Center in Philadelphia, a close colleague of Lamartiniere and co-author of the paper published last week.
The research is the product of an ongoing, multisite study originally conceived to find causes of breast cancer and funded by the National Institute of Environmental Health Sciences and the National Cancer Institute.
Russo said researchers are looking at two types of plastic additives that have raised red flags in animal studies - phenols and phthalates.
BPA is a phenol, and researchers suspect that girls exposed to these compounds before puberty could become more susceptible to breast cancer. Hormonal activity later in life - during puberty, pregnancy or menopause - may trigger this susceptibility.
Researchers suspect phthalates may cause genetic changes in girls that predispose them to obesity.
The research is far from conclusive.
"We need to be very careful," Russo said. "Don't go crazy."
Russo said human studies are under way in New York, Ohio and California that should produce more definitive results about relative risks.
Data likely in 2 years: In one of those studies, Dr. Frank M. Biro of Cincinnati Children's Hospital said his team of researchers has recruited 378 young girls in the Cincinnati area. The girls have been tested for exposure to phenols and phthalates. Researchers have also tested the girls for exposure to phytoestrogens - natural compounds that occur in plants such as soy and also are believed to cause changes in hormonal cycles.
"We're looking for girls with a particular exposure profile," Biro said.
Using cutting-edge genetic technology, Biro plans to compare girls with little or no exposure to any of these compounds to girls with heavy exposures.
"Our hypothesis is there are certain genes that get turned on earlier, that get turned on harder," he said. "So it's either a time issue or a strength issue."
As Biro's work progresses, Lamartiniere intends to compare the genetic profiles of the girls with the genetic profiles of the exposed lab animals and see whether there is a connection.
Biro believes his team will have meaningful results from the research in two years, although he has examined some early data.
"Give our studies another couple years and there is going to be conviction about some of these chemicals," he said. "We may not have the definitive answers, but we'll be able to ask better questions."
11 January, 2009
The Birmingham News
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