Mind The (Risk Perception) Gap On BPA
BY STEVEN HENTGES, PH.D JULY 13TH 2016 09:43 AM
Summary
It is commonly perceived that natural chemicals are safe while manmade
substances may be harmful. These perceptions, however, if not supported byscientific evidence, can result in risk perception gaps that can cause us to worry
more than warranted by the evidence.
A current example of a risk perception gap is the common belief that naturally
occurring chemicals known as isoflavones, which are present at significant levels insome foods, are safe or even beneficial to health. In contrast, the manmadechemical bisphenol A (BPA), which may be present at lower levels in some foods, iscommonly believed to be harmful.
Recent pharmacokinetic studies from the U.S. Food and Drug Administrationsuggest that these beliefs are inverted. The pharmacokinetic data on BPA indicatethat it is not likely to be harmful due to efficient metabolism and rapid eliminationfrom the body. In contrast, data from a recent study suggests that isoflavones
could pose a higher potential health risk compared to BPA. Understanding thedifference between real risk and perceived risk is important for consumers to makesound choices based on facts rather than fears.
BackgroundThe chemical bisphenol A (BPA) has been a popular topic for discussion in recent
years in both consumer and scientific publications. In many, probably even most,of these discussions, the term risk is used in close proximity to BPA.
In scientific publications, risk is a technical term that refers to the likelihood of ahealth effect occurring due to exposure, in this case to BPA. Risk is generally
understood to be a quantifiable measure that is based on an objective analysis ofscientific facts. Of perhaps more importance for consumers is the concept of risk
perception. In sharp contrast, risk perception is a subjective measure in whichscientific facts are interpreted through an emotional and instinctive psychologicallens that considers both facts and fears.

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The distinction between risk and perception often leads to a risk perception gap, aterm that has been studied and popularized by the risk
perception consultant and scholar David Ropeik, affiliated with Harvard. The gapbetween facts and fears can cause us to worry about something more, or less, thanwarranted by the evidence.
A number of emotional factors have been identified that help explain why somerisks are feared more than others. One factor is that we tend to be more afraid ofmanmade risks compared to natural risks. A good example of a risk perception
gap based on this factor was highlighted in a recent study of natural chemicals
known as isoflavones that occur at significant levels in a wide range of foods, inparticular soy-based food products.
New Study on Isoflavones
Isoflavones are well known to be estrogenic, which raises the potential forinterference with the body’s endocrine system and resulting health effects. Soy
infant formula is of particular interest since it may be the sole source of nutrition
for some infants, leading to relatively high exposure to isoflavones at a sensitive
age of development.
The new study, conducted by the U.S. Food and Drug Administration (FDA),
examined the pharmacokinetic properties of two prototypical isoflavones (genisteinand daidzein) in neonatal and adult rhesus monkeys, which are a goodexperimental model for humans. Pharmacokinetic studies do not test toxicity
directly, but provide information on the potential for toxicity by monitoring what
happens to a chemical once it enters the body. For example, pharmacokinetic
studies measure how much of a chemical is absorbed, where it goes in the bodyand in what form, how long it lasts in the body, and how it is eliminated.
For comparison, FDA previously conducted a similar pharmacokinetic study on
BPA. Similar to isoflavones, it is well known that BPA is weakly estrogenic. In
contrast to natural isoflavones, which are widely believed to be safe or evenbeneficial to health, BPA is a manmade chemical that is believed by many to beunsafe. In this context of risk perception, the comparison of pharmacokinetic
properties between isoflavones and BPA is particularly informative.

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Implications for Real Risk vs. Risk Perception
The two studies found that both isoflavones and BPA are metabolized andeliminated from the body after oral exposure. Beyond general similarities though,there are several important pharmacokinetic differences between isoflavones andBPA, in particular when studied in neonatal monkeys.
An important pharmacokinetic parameter is how much of a substance enters thebloodstream in its parent form (i.e., unmetabolized), which is the biologically activeform. This is referred to as the internal exposure or dose of the substance. In
neonatal monkeys, the internal dose of the isoflavones was found to be about 5,000times higher than the internal dose of BPA, as measured by maximum bloodconcentration of the parent substances. This suggests significant differences in thephysiological systems for metabolism and clearance of isoflavones compared toBPA.
A similar difference was found in the length of time the substances remain in thebody before elimination, with isoflavones staying in the body longer. Thisdifference suggests immaturity in the physiological systems for elimination of
isoflavones compared to BPA. Overall, the pharmacokinetic profile of BPA suggeststhat it is unlikely to cause health effects at typical human exposure levels, which
are very low. As stated by the FDA researchers:“Despite repeated determinations of safety by major food regulatory bodies,including the U.S. Food and Drug Administration and European Food Safety
Authority, a high degree of risk perception is often associated with children's
ingestion of BPA … Such an exposure produces low internal exposures in newbornmonkeys (0.01-0.02 nM peak serum concentration per mg/kg bw ingested) … This

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contrasts with the perceived safety of soy formula … despite the much larger dosesof soy isoflavones consumed … that produce substantially higher internal exposures(50-100 nM peak serum concentration per mg/kg bw ingested) … This dichotomy
likely reflects the roles that natural vs. synthetic chemicals and individual vs.
corporate choices predictably play in shaping risk perception and the limited abilityof public institutions to bridge “The Risk Perception Gap” engendered by basic
cognitive processes shared by different groups within scientists and the lay publicalike (Ropeik, 2015).”
As noted above, pharmacokinetic studies do not directly measure toxicity, but thesignificant pharmacokinetic differences suggest that isoflavones have a higher
potential for risk to human health compared to BPA. This is particularly importantsince human exposure to isoflavones (e.g., infant exposure through soy-basedformula) is quite a bit higher than human exposure to BPA.
The perception of risk for isoflavones and BPA is precisely the opposite, withisoflavones perceived to be safe or beneficial while BPA is perceived to be a risk tohuman health. Understanding both risk and risk perception is important to support
sound choices based on facts rather than fears.

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