Ask Carl Winter, PhD, Extension food toxicologist at the University of California, Davis, to name the event that brought bisphenol A (BPA) to the forefront of public awareness and he is quick to mention a feature article published in the December 2009 issue of Consumer Reports.
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Said article presented results of a limited monitoring program that detected BPA in several of the 19 name-brand foods tested. “While the findings were predictable, the article drew national headlines with its contention that consumers could be facing serious risks from exposure to BPA in their foods,” Dr. Winter points out.
Synthesized in 1891 by Russian chemist Aleksandr Dianin, BPA is a chemical now used primarily in the production of polycarbonate plastics and epoxy resins. Polycarbonate plastics are used in food and drink packaging, while resins are employed as lacquers to coat metal products such as food cans, bottle tops, and water supply pipes.
According to Dr. Winter, the controversy in 2009 stemmed from the debate over what levels of consumer exposure to BPA should be of concern. “The U.S. Environmental Protection Agency (EPA) and the European Food Safety Authority (EFSA) then considered an acceptable level of BPA exposure to be 50 micrograms (μg) per kilogram (kg) of body weight per day (μg/kg/day),” he notes. “In contrast, the Consumer Reports article argued for an acceptable level of 0.0024 μg/kg/day, which was more than 20,000 times lower than the U.S. and European levels.”
Today much of the ongoing concern regarding BPA exposure to consumers is based upon the scientific process of “hazard identification,” as contrasted with “risk characterization,” Dr. Winter relates.
“Hazard identification expresses what is known about the chemical in question (BPA in this example) and what potentially hazardous properties it may have, such as estrogenic, carcinogenic, or neurotoxic properties that could be revealed from animal toxicology studies or human epidemiology,” he explains. “Hazard identification does not consider the amounts of actual exposure to the chemical in question. In contrast, risk characterization identifies the most significant and relevant toxicological endpoints (results of studies conducted to determine how dangerous substance are), identifies toxicologically-significant levels of concern, and compares predicted levels of exposure with the levels of concern to estimate how risky the chemical is.”
The FDA issued a memo in 2014 concluding that estimated exposures to BPA among a variety of population subgroups were more than 4,000 times lower than the 5 μg/kg/day level of toxicological concern for BPA.
Following that FDA memo, the regulatory limits have dropped from 50 μg/kg/day to 4 or 5 μg/kg/day since June 2014 “primarily because of the use of an additional 10-fold uncertainty factor conservatively applied to risk characterization process,” Dr. Winter says.
“Similar conclusions were reported in 2015 by the EFSA, which uses a slightly lower level of toxicological concern, 4 μg/kg/day, but still concludes that exposures, including dietary and non-dietary, for all population subgroups were below this level,” he adds.
In 2012, the U.S. National Toxicology Program, the National Institute of Environmental Health Sciences, and the FDA developed a research program called Consortium Linking Academic and Regulatory Insights on BPA Toxicity (CLARITY-BPA). “CLARITY-BPA recently concluded a two-year BPA toxicological Core Study and the results, currently being peer reviewed and expected to be published in August 2018, could affect the level of toxicological concern for BPA,” Dr. Winter predicts. “It would take a significant reduction in the level of toxicological concern for authorities such as the EPA, FDA, or the EFSA to change their conclusions regarding the lack of risk posed by BPA to consumers based upon exposure characteristics.”
FDA’s current position on BPA is reflected in a recent statement by Stephen Ostroff, MD, Deputy Commissioner for Foods and Veterinary Medicine, in which he mentions that the CLARITY-BPA Core Study found “minimal effects” for the BPA-dosed groups of rodents when growth, weight, and tumor development were evaluated.
“In the 20 years that FDA has been reviewing and evaluating scientific literature on BPA, we have come to recognize some key points as important in our review of chemical compounds used in food and food packaging,” says Marianna Naum, PhD, a microbiologist who serves as FDA’s team lead for strategic communications.
For starters, analytical methodology matters, Dr. Naum emphasizes. “When evaluating the potential toxicological effects of a chemical compound, awareness of its current uses is important,” she notes. “It is necessary to be aware of and characterize the potential for inadvertent or unavoidable contamination when conducting toxicology studies. Carefully controlled sample collection and analysis methods, as well as use of radiolabeled material, may be necessary to gain a better understanding and characterization of potential contamination. Evaluating this potential for inadvertent exposure permits better characterization of the true internal doses and biological effects in test animals and can be useful in explaining unexpected results or uncertainties in previous reports.”
Continued monitoring of scientific literature is a second critical task relative to BPA, Dr. Naum mentions. “FDA Office of Food Additive Safety staff routinely monitor the scientific literature for new research that helps enhance our understanding of substances added to food or food packaging, and consider new data as we continue to ensure the safe use of these substances,” she relates, noting that a summary of FDA’s work relative to BPA is available on its BPA web page.
Impact of Inaccurate Information
“Essentially, I think we’ve learned that it’s hard to reverse public opinion with scientific facts after consumers have been given so much inaccurate information,” says Kay Cooksey, PhD, the Cryovac Endowed Chair in the Packaging Science Program at Clemson University. “Although we have always known this fact, with today’s social media and Internet sources sounding so convincing, the BPA situation became harder to overcome than almost any other packaging issue in the last 25 years, in my opinion. Given that we know the public will not always understand what is ‘safe,’ we learned that we should examine the materials we use in contact with food with the level of proof and explanation that goes beyond saying that the FDA or other government agencies allow us to use them.”
Dr. Cooksey says it’s necessary for food industry stakeholders to constantly examine if there is an alternative product for food packaging that won’t have as much concern as BPA from a safety point of view. “If we do, we should plan to scale the alternate up and pay for the cost difference before an issue arises,” she relates. “I know the industry has done this for years, but the BPA issue has just made the idea of having safer and possibly more expensive and less practical alternatives as an option, whereas in the past, we wouldn’t have considered looking at materials and processes that don’t have good machinability or reduce shelf life as an alternative.”
Of concern to Dr. Cooksey is that research proved epoxy-based can liners are safe at the consumption rates that fall well within the allowable limits, but any volume of data or history on the can liners that may be used as alternatives does not yet exist. “There are some materials we do know a lot about, such as polyester as a can liner, and we’re using materials from our distant past, namely oleoresins, but those are not compatible for all foods and processes, so in order to have a can liner that has all the functionality of the epoxy liners, we might be switching to a material that has different issues, some of which could be safety related,” she notes. “Regardless of this situation, the food packaging industry is making the change and doing it quickly. The industry will not do anything that is not safe for consumers, so they are doing it knowing other factors such as machinability or overall shelf life may be affected negatively.”
An important issue is how the safety of packaging and how it contributes to food safety is communicated to consumers, Dr. Cooksey points out. “We continue to compete with voices that oversimplify and blow things out of proportion to get attention, and our responses are not as swift or attention grabbing as their ‘inaccurate’ voices,” she says. “We need to continue to work on this.”
For Jonathan (Josh) Bloom, PhD, director of chemical and pharmaceutical sciences for the American Council on Science and Health, a lesson learned is that BPA is the quintessential example of scare tactics used by groups and individuals with agendas that exaggerate or even fabricate harm when none exists. “That includes an ignorant, lazy press, that can’t be bothered to challenge anything that is spoon fed to them,” he believes.
Dr. Bloom suggests the hysteria over BPA perhaps reached its apex when Nicolas Kristof, a columnist for The New York Times, wrote on February 23, 2018 that he won’t touch cash register receipts because they contain a tiny amount of the chemical.
“BPA is ubiquitous,” Dr. Bloom relates. “It is used to make polycarbonate plastics which line the inside of metal cans of food, preventing air from getting in and promoting the growth of nasty things like botulism. Some BPA leaches into the food. It always has.”
The knock on BPA, Dr. Bloom says, is that its chemical structure allegedly resembles that of the structures of the sex hormones and therefore will have some kind of effect on fertility. “The phony term that is used to describe chemicals that may interact with hormone receptors is ‘endocrine disruptor,’” he points out. “This term is used ad nauseam in the junk science literature. But it’s a bunch of nonsense.”
Not only does BPA not chemically resemble the structures of the sex hormones, when it binds to estrogen receptors it does so very weakly compared to estrogen, Dr. Bloom elaborates. “Also, there is very little BPA in the blood, anyhow, because one of the jobs of our livers is detoxifying chemicals,” he notes. “BPA studies almost always measure its concentration in urine because that’s where the chemical is found, just like it should be. There are well-known mechanisms for eliminating chemicals, both natural and synthetic, and the usual route is: 1.) metabolism of the chemical to form a water-soluble metabolite and 2.) elimination in the urine. This is why BPA is found in minuscule amounts in almost everyone’s urine. It’s supposed to be there.”
Dr. Bloom says the primary reason that people are making a stink about BPA has nothing to do with the chemical. “It is because analytical techniques have become so powerful that unbelievably small amounts of almost any chemical can be detected almost anywhere,” he explains. “The BPA has been there all along. But now it’s possible to ‘see’ it.”
The “effects” of BPA on sex hormone receptors have been determined by feeding huge quantities of it to rats and looking for any difference between BPA and control groups, Dr. Bloom mentions. “What this has to do with the human situation is unclear,” he emphasizes. “People generally do not eat spoonfuls of BPA. And even if they did, it probably wouldn’t matter. The literature is littered with papers about this. And they’re just nonsense.
“There are careers, egos, and a whole lot of money that depend on BPA being ‘bad,’” Dr. Bloom says. “Yet, there are some scientists that maintain that it hasn’t been studied ‘enough.’ It is convenient and foolproof to make this argument since nothing can ever be proven to be safe.”