To ban or not to ban, that is the question now being asked about a chemical named bisphenol A--aka BPA--used in the production of plastic bottles and a wide range of other consumer products.
Polycarbonate plastics like BPA have several advantages over other types of plastics: they're transparent, durable and able to withstand high heat, and have high electrical resistance. Epoxy resins produced with BPA are particularly strong and are used in dental applications as well as industrial uses.
Proponents of a ban on BPA claim that the chemical has all sorts of noxious effects, including hormonal disruption, heart disease, diabetes and worse still, aggressive toddlers. They also contend that BPA poses these dangers even in extremely small quantities, including the amount that might leak out of the dental epoxy used to hold in a crown or the amount that might leach out of a sippy-cup into baby's morning apple juice.
But as Paracelsus, the father of toxicology observed, "All things are poison and nothing is without poison, only the dose permits something not to be poisonous." And claims of BPA's toxicity are all about the dose.
Studies that demonstrate risks from BPA are the usual high-dose animal studies that are prone to various problems when you try to extrapolate from them to human beings. Studies portending to show low-dose effects in animals have been largely irreproducible and are therefore particularly suspect. But there are good reasons to suspect toxicological results from animal testing in the first place.
First, humans are not giant rats: we have millions of significant differences in our genetics, biochemistry, immune systems and so on.
An article in Slate points out that in 1999 the Health and Environmental Sciences Institute, a Washington-based group, began a thorough examination "Working with confidential data provided by 12 pharmaceutical companies on 150 compounds that had produced a variety of toxic effects in people, an institute-hosted workshop found that only 43 percent of the drugs produced similar problems in rodents, and 63 percent did so in non-rodents." Second, human exposures are vastly lower than those used in animal studies. In order to get enough negative health effects in laboratory animals, they must be fed large doses that, by experimental design, will kill many of them.
Animal studies show that a daily dose of 50 milligrams of BPA for each kilogram of body weight has no observable health effect. Assuming that translates directly to human beings, for a 150 pound person, that would be about a daily ingestion of one tenth of an ounce.
Yet the estimated human dietary intake of BPA from polycarbonate plastic and epoxy resin food contact applications is less than 0.000118 milligram for each kilogram of body weight, which would be about one quarter-millionth of an ounce per day for a 150 pound person--far below the safety limits set by regulatory agencies for human consumption of BPA.
The safety of BPA has been affirmed by research undertaken by the U.S. National Toxicology Program, the U.S. Food and Drug Administration, the U.S. Centers for Disease Control, the European Food Safety Authority, Japan's National Institute of Advanced Industrial Science and Technology, Germany's Federal Environmental Agency, The European Commission's Scientific Committee on Toxicity, Ecotoxicity and the Environment, The European Commission's Scientific Committee on Food and the European Food Safety Authority.
BPA is just the latest bogeyman that the environmental movement has latched onto in order to attack something they've hated ever since the phrase "Plastics my boy, Plastics" was uttered in "The Graduate."
When the chem-banners do their thing, it's best to remember the words of H.L. Mencken, who observed, "The whole aim of practical politics is to keep the populace alarmed--and hence clamorous to be led to safety--by menacing it with an endless series of hobgoblins, all of them imaginary."
Kenneth P. Green is a resident scholar at AEI.