All of us want to avoid the adverse effects of exposures to naturally occurring and synthetic chemicals but we must also recognize that many of these materials are beneficial and they make our lives safer and more enjoyable. The most logical approach therefore is not to eliminate such exposures but to control them so that we preserve the beneficial effects and avoid the adverse effects. Governmental agencies such as the Food and Drug Administration, the Environmental Protection Agency and other agencies seeking to improve public health have traditionally used this approach to regulate our exposure to drugs and other chemicals. In those rare situations where banning rather than control was used such as the passage of the Delaney proviso in 1958, strict enforcement of this zero exposure regulation would have eliminated many of our drugs, foods and essential chemicals. Banning bisphenol A repeats this 1958 mistake and ignores our proven ability to use science, experience and judgment to establish appropriate regulations for all chemicals including bisphenol A.
To control exposure we need to know what kind of effects (good and bad) that the chemical can produce in humans and the dose response for each effect. We look first for data in humans and we complement that with data in other species using protocols that have been developed over many years and shown to be capable of reliably predicting human effects. We have human data on bisphenol A effects from workers who are involved in its manufacture and we have carefully controlled clinical studies on its uptake, metabolism and elimination from the body after it is ingested. The American Council of Governmental Industrial Hygienists established an occupational exposure level for compounds like bisphenol A and this level has protected workers for several decades. Similar levels have been established by agencies in Germany, Netherlands and the UK. Studies in rodents have demonstrated that bisphenol A has a low acute oral toxicity but repeated high doses in pregnant rats decreased the number of litters, litter size and the growth and development of the pups. The EPA and other regulatory bodies used this information to set the minimal daily dose required to produce adverse effects and they used the three generation rat study to set the daily safe dose for bisphenol A. This information has been used by NSF International to recommend a safe level for bisphenol A in drinking water and that level is reassuringly consistent with the previously established occupational exposure level.
Chemically bisphenol A is similar to the synthetic estrogen diethylstilbestrol and it has been known for years to produce similar estrogenic effects. However, it was not until EPA established their endocrine disrupter program in 1996 that reports began to appear suggesting that bisphenol A could produce such effects at very low dosage levels. We now have a large number of such studies but their interpretation is controversial and their dose response information is inadequate for the traditional regulatory approach. These studies could stimulate the development and validation of new protocols for evaluating and regulating exposure to endocrine disruptors. If this were to occur, we could base our approach to bisphenol A as an endocrine disrupter on tested science rather than on some arbitrarily defined level of concern.
It is clear from the extensive scientific data on bisphenol A that an outright ban cannot be justified from a public health point of view. Our time-tested methods for human health risk assessment permit our regulatory agencies to establish rigorous limits on exposure that provide a wide margin of safety. Both the scientific and regulatory communities have recognized since the ill-conceived Delaney proviso in 1958 that banning any chemical, in contrast to a careful regulatory oversight, is a legislative straight jacket that not only devalues science but provides no real improvement to public health.
John Doull, MD, PhD, is Emeritus Professor of Toxicology, University of Kansas Medical Center, past president of the Society of Toxicology, consultant to FDA and EPA, and an ACSH Advisor.
