A controversial component of plastic bottles and canned food linings is present in far too small amounts in most people's bodies to cause suspected health effects, according to Pacific Northwest National Laboratory analyses.
"My findings are consistent with FDA's (Food and Drug Administration) and European Food Safety Authority's conclusions that BPA is safe as currently used," said toxicologist Justin Teeguarden, a senior scientist at the Department of Energy's national laboratory in Richland.
BPA, or bisphenol A, has the potential to mimic the sex hormone estrogen if blood and tissue levels are high enough, disrupting that part of the endocrine, or hormone, system.
Because of concerns about the chemical, in 2010 the state of Washington banned its use in baby bottles, children's cups and sports bottles, and recently completed tests to show that few of the banned products continue to be sold in the state.
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The ban was passed after the National Toxicology Program concluded there was come concern about the toxicity of BPA in fetuses, infants and children.
When Teeguarden looked at 150 BPA exposure studies, he concluded that in the general population, people are not exposed to enough BPA for it to effectively mimic estrogen in the human body. The studies covered 30,000 people, including women of child-bearing ages and infants, in 19 countries.
"To date, my research shows that the BPA levels in humans in the general population are expected to be hundreds to thousands of times lower than the concentrations we expect to be estrogenic and hundreds to thousands of times lower than those that cause toxicity in animal toxicity studies," he said.
BPA can bind to the same proteins that estrogen does -- called estrogen receptors -- when estrogen is doing its job in the body.
But, in most cases, BPA does so more weakly than estrogen. To trigger biological effects through receptors and disrupt that part of the body's hormone system, BPA concentrations have to be high enough in the blood to overcome that weakness.
Teeguarden's analysis of data from the 150 studies showed that human blood levels of BPA are expected to be too far below levels required for significant binding to four of the five key estrogen receptors to cause biological effects.
His analysis also confirmed previous findings of academic and government scientists that BPA that binds with estrogen receptors is at such low concentrations in the blood that it is beneath the ability of current technology to detect it. Studies that show otherwise may have been flawed by sample contamination.
There may be cases in which plastics and solvents used to collect and process samples have contaminated the samples, showing artificially high levels of BPA, Teeguarden said.
Two years ago, he conducted a study with 20 volunteers, feeding them a canned-food diet to expose them to BPA, and then collecting blood samples throughout the day. The study, done in conjunction with the Centers for Disease Control and Prevention, found no BPA in the volunteers' blood, he said.
As part of his most recent research, he also analyzed 130 studies that looked at BPA's toxicity in animals and cells in the laboratory. He selected studies that referred to exposure levels as "low dose," implying they were relevant to human exposure.
"We wanted to understand if these 'low-dose' studies were conducted at exposures like those humans are exposed to, or much higher," Teeguarden said.
"Low dose" turned out to span an immense range of concentrations, a difference of 12 orders of magnitude or the difference between 1 and 1 trillion. Just 0.8 percent to 7 percent of the exposures in each study were in the range of human exposures, Teeguarden, with the help of PNNL biologist Sesha Hanson-Drury, concluded.
"Unfortunately, the low-dose moniker has been used by some to promote the importance of selected toxicity studies, for example, in arguments to ban BPA," Teeguarden said. "For BPA and all chemicals, we need more accurate language to present these findings so the public and scientists in other disciplines can understand how human exposures compare to exposures in laboratory studies reporting toxicity."
Teeguarden's analyses of human exposure studies and animal and cell toxicity studies were supported by the U.S. Environmental Protection Agency.
-- Annette Cary: 582-1533; firstname.lastname@example.org; Twitter: @HanfordNews