A new study published in the journal Toxicology and Applied Pharmacology demonstrates that coating the mouth with food containing trace amounts of BPA does not lead to higher levels of the chemical in the bloodstream. In this study, 10 male volunteers ate warm tomato soup that contained a traceable form of BPA. Researchers then took multiple blood and urine samples over a 24-hour period. The study’s author, toxicologist Justin Teeguarden of the Department of Energy’s Pacific Northwest National Laboratory, spoke to Can Science.
What led you to your new study, in which you coated the mouths of human volunteers with food that contains BPA?
A previous study in beagle dogs raised the possibility that ingested BPA could be absorbed in the oral cavity. Absorption in the oral cavity would mean that the BPA does not pass first through the gut and liver, where extensive evidence shows it is almost entirely inactivated. The authors of the dog study opined that higher-than-expected blood concentrations of BPA might result in humans. In fact, the findings of the dog study were used to question regulatory decisions regarding the safety of BPA. So whether or not higher blood concentrations did occur in humans quickly became an important scientific and public health question.
You used warmed tomato soup. Any significance? How did you choose this food and why warm it up?
We wanted a common food item (soup), which is known to have trace amounts of BPA (so it’s a recognized source) that was a liquid so that the BPA in this matrix could coat the entire oral cavity (maximize contact between the BPA and the absorbing tissues of the mouth). With this design, we assured that the study context was 100 percent relevant to normal human food-ingestion behavior and maximized the chance for us to see increases in BPA in the blood. This was not something that was possible in the dog study.
You came to the conclusion that oral exposure does not lead to higher-than-expected levels of BPA in the blood. Does this clear up earlier incorrect assumptions about how much BPA lands in our bloodstream after eating a can of soup?
There are lots of conclusions “out there.” The findings of our study, a collaboration between the Pacific Northwest National Laboratory and experts at the U.S. Food and Drug Administration’s National Center for Toxicological Research and Ohio State University, reaffirm the conclusions of the regulatory agencies: Human exposure to BPA from foods leads to blood levels safely below those that cause effects. It corrects the hypotheses made by the authors of the dog study, morphed by the media into expectations, that higher levels of BPA would appear in blood.
In your previous research there was some criticism that you did not measure the BPA level in the food, even though you measured urinary output. Does this study address that proposed issue?
That particular criticism was later exposed in the published literature as a failure to understand or acknowledge several of the most basic fundamentals of science. Interested people can read and understand this themselves. In the new soup study we gave volunteers precisely measured doses of a form of BPA that is easily traced in the body. This was important because it allowed us to measure lower levels in blood. Since all the BPA came out in the urine, the study also provides additional data — conclusive data (as in the other studies!) — that measuring urine output is the same as measuring what is in the food: 100 percent absorbed, 100 percent eliminated means measuring elimination is the same thing as measuring dose. It confirmed the approach we used for the first study, which as you point out was criticized.
Did you come across anything surprising in this study?
Frankly, no. Even with better detection limits and confirmatory computational modeling, we observed what all the existing human, rodent and monkey data would lead one to predict. We also confirmed that most blood-collection devices have polycarbonate — BPA-containing — parts that can lead to blood contamination.
Is there any number of cans of warmed tomato soup a person might consume at which point those trace BPA levels might become a concern?
Anyone can calculate this number from some information on BPA in canned soups and safe daily exposures established by regulatory agencies that have carefully reviewed all the toxicity data. The European Food Safety Authority recently listed a Tolerable Daily Limit of 4 μg BPA/kg/day. That would be about 320 μg/day for an 80-pound adult. Assuming [data from] a Consumers Union study are representative of BPA in soups, we can use a range of amounts, 6.1-22 μg of BPA per serving in several canned soups for our calculation. A little division and we find that 14-53 servings of soup per day and you have not exceeded what the European Food Safety Authority considers safe: “no health risk to consumers of any age group (including unborn children, infants and adolescents).”
How does your study reinforce recent conclusions made by the FDA and EFSA?
Overall, the work affirms the positions of regulatory agencies. The study reinforces the accuracy of conclusions made by the European Food Safety Authority, the FDA, the World Health Organization and others about the extent and nature of BPA exposure, absorption and metabolism. It follows that these regulatory agency determinations that BPA is safe as used for food-contact applications are not challengeable on the basis of uncertainties in oral exposure.
With the news of your study, the FDA announcement in the fall and the EFSA’s recent study — all of these showing BPA to be safe for human consumption — do you think the controversy over this chemical will start to die down? Why or why not?
Controversies like this don’t end. As greater awareness of the consistency of regulatory agency findings regarding BPA takes hold, and the broader media follow the lead of the regulatory agencies and the funding agencies, which all have moved forward to address the hazards of other materials, the controversy will be limited to an increasingly smaller group of people, scientists and media outlets.
Want to learn more about BPA? Read our BPA facts sheet.