How America became obsessed with BPA
The route of the controversy: Eat or inject? (cont'd)
If oral exposure is the key to determining whether BPA is a risk, we need to know how much of it we’re actually exposed to. In the most comprehensive study of oral ingestion that used the latest biomonitoring techniques, two German researchers concluded that our daily exposure to BPA works out at less than one-tenth of a microgram per kilogram of body weight (Dekant, W. and W. Volkel 2008. Human exposure to bisphenol A by biomonitoring: Methods, results and assessment of environmental exposures, Toxicology and Applied Pharmacology Volume 228, pages 114-134):
“The average daily doses of bisphenol A in adults delineated by biomonitoring and supported by the exposure assessment based on concentrations of bisphenol A in the diet are more than 500-fold below the TDI set by EFSA and the US EPA reference dose (both 50 μg/kg bw/ day) suggesting that the exposure to bisphenol A does not result in a health risk to the general population. In addition, the bisphenol A exposures of the general population are also well below the daily doses of bisphenol A that sometimes have been reported to cause responses of unknown toxicological relevance in highly sensitive animal systems (20 μg/kg bw/day) (Timms et al., 2005) giving Margins-of-Exposure of 200 or more. For a comparison with human intake of other weakly estrogenic compounds, bisphenol A intake is at least 30 fold lower than that of phytoestrogens, which are more potent estrogens as compared to bisphenol A (Moors et al., 2007, Safe, 2004, Valentin-Blasini et al., 2005).”
This means that there is “a 500,000 fold difference between the lowest oral exposures in animals associated with any adverse effects and the oral human exposure,” says Willhite. By any measure, this does not constitute a health risk. We get vastly more estrogenic chemicals from eating nuts, cereals and bread.
But what about babies? Environmental activists in the U.S. have focused largely on the risk to infants and not adults from exposure to BPA given that they do not have a fully developed adult metabolism and that even tiny, almost insignificant amounts of “free” BPA (unconjugated BPA) could be damaging – as if it was being injected into their blood. STATS put the question to Wolfgang Dekant., professor of toxicology at the University of Würzburg and one of the lead authors of the European Food Safety Authority risk assessment (as well as a co-author of the BPA biomonitoring study).
“The exposure of babies to BPA is well below the tolerable levels based on the most sensitive toxicity endpoint seen in reliable animal studies [with the] inclusion of an additional safety factor of 100. Moreover, babies are exposed to a variety of other compounds with weak estrogenicity such as isoflavones from diet (higher exposures and more potent hormones compared to BPA) without effects. Actually, isoflavone exposures are orders of magnitude above those to BPA in babies given soy formula and this is considered ‘healthy.’ Should we not worry about soy ingredients and the transfer of such compounds to babies much more then about BPA?”
This question appears not to have occurred to journalists covering BPA. (Similarly, the very latest research by the EPA – A.M. Calafat et al. (2009) Exposure to bisphenol A and other phensols in neonatal intensive care unit premature infants. Environmental Health Perspectives Volume 117, pages 639-644 – which demonstrates that even premature babies are capable of metabolizing BPA in the same way as adults has generated no coverage).
In two years of media reporting and editorializing, and activist lobbying of politicians and the public, the difference between the outcomes produced by different routes of exposure has been almost entirely ignored. Despite every regulatory agency in the world’s decision to accord greater relevance to studies based on the ingestion of BPA, the media has overwhelmingly focused on studies using injections of BPA. This, of course, has turned BPA from being innocuous – a non issue in Europe and the rest of the world – into a major public health scare in the U.S. and Canada.