“My position,” he said, “is simply that we should use the massive body of human exposure data to inform our toxicology studies.”
The animal studies, he said, were based on “exposure levels much higher than has been measured in most human blood samples and is therefore not sufficient evidence on which to make claims that humans are at risk at current exposure levels.” He also said in an interview that there is a history of claims that have been made about BPA that subsequent studies have disproved or not replicated.
While his current research is not funded by industry, Teenguarden in the past has received some funding from the chemical manufacturing and plastics industries, according to journal articles he authored.
Scientists on the other side include University of Chicago at Illinois professor of physiology Gail Prins who is studying BPA’s effects on the prostate gland; Washington State University professor of biomolecular science, Patricia Hunt who is investigating the effect of prenatal BPA exposure on rhesus monkeys; University of Massachusetts Amherst biology professor R. Thomas Zoeller, whose research focuses on endocrine disrupting chemical’s effects on the thyroid; Tufts University postdoctoral associate Laura Vanderberg, whose most recent published study found that prenatal BPA exposure can alter male mouse mammary glands; and University of Missouri-Columbia biology professor Frederick vom Saal, who has studied BPA for decades.
There is "not sufficient evidence on which to make claims that humans are at risk at current exposure levels.” -Justin Teeguarden, Pacific Northwest National Laboratory These scientists maintain that many adverse effects have been found at BPA levels comparable to those Teeguarden and colleagues say are being found in human blood. Contrary to what Teeguarden and colleagues’ models suggest, they say that what’s been measured in people is within the range of amounts that harm lab animals. They also argue that the modeling analyses Doerge, Teeguarden and colleagues have conducted do not accurately represent what scores of published, peer-reviewed observational biological studies have reported.
These biologists are concerned that these models may be used by the FDA to tell the public that BPA is safe.
“There’s a significant amount of data on human exposure to BPA that is beginning to follow a pattern that is following what we’re seeing in animal data,” Zoeller said.
NIEHS director Linda Birnbaum concurred. “We’re seeing effects in animals at very, very low concentrations and also seeing associations in a large number of epidemiological studies,” she said. “We know we’re seeing activity at the picogram level.”
Vom Saal said “at incredibly low doses, BPA can alter pituitary, breast and prostate cells.” Such effects have been seen in animal studies, including those with primates.
Presenting "guesses" to the public
Teeguarden’s conclusions, Vom Saal said, are “based on assumptions and math models that are being treated as fact and presenting guesses to the public as if they were based on real world data instead of clinical measurements.”
Prins said it’s important to understand that Doerge’s and Teeguarden’s models are designed to measure how much of a chemical may be present – not to investigate biological activity.
Or as Birnbaum explained, “the modeling may be okay but it tells you nothing about how the compound might interact or at what level.”
“We’re seeing effects in animals at very, very low concentrations and also seeing associations in a large number of epidemiological studies. We know we’re seeing activity at the picogram level.” -Linda Birnbaum, NIEHS Zoeller also notes that the toxicological modeling is not designed to examine effects of chronic, low-dose exposure to an endocrine-disrupting chemical like BPA. Historically, these models have looked at specific cancers or fully manifested diseases. In contrast, BPA appears to produce health effects that set the stage for diseases often diagnosed many years after exposure.