Since the 1960s bisphenol A, or BPA, has been used to manufacture hard plastics ranging from an infant’s milk bottle and a child’s first sippy cup to every college student’s favorite Nalgene. Studies have suggested that over 90 percent of people have BPA — which can leach out of plastic into foods — in their bodies, but it wasn’t until the fall 2008 that the Food and Drug Administration, at the prodding of a separate governmental review, began to question its long-standing determination that BPA was safe. While the FDA is to be applauded for its 2010 update that recommends limiting exposure to the chemical, particularly for children, the agency’s failure to identify the potential risk of BPA earlier is an example of why the current approach to chemical regulation in the United States is fundamentally flawed.

The January update is a thoughtful appraisal of the conflicting evidence on BPA and the new research that needs to be done to reconcile the scientific discrepancies. For instance, toxicology experiments in the 1980s concluded BPA was safe because the lowest level for which they observed toxic effects (50 milligrams per kilogram of body weight daily) was well above what an individual would ever expect to ingest. But more recent work evaluating BPA at doses over a thousand-fold lower — a far more realistic amount — has repeatedly found a correlation between BPA exposure and detrimental effects on the reproductive, cardiovascular and nervous systems. The plastics industry, which produces a staggering 4 billion pounds of the chemical annually, has been predictably critical of many of these “low-dose” studies, claiming that the results are invalid because they use rodents, which are less capable than humans in processing BPA.

Because the BPA literature is a patchwork of experimental systems with varying routes and times of exposure, doses and measured endpoints, direct comparison of the research is impossible. Nevertheless, I find it increasingly difficult to dismiss the dangers of BPA outright, as the plastics industry would like me to do. Just last Wednesday, researchers at Yale published reported that BPA exposure to mice in the womb makes them more sensitive to estrogen. BPA alters the body’s hormonal signaling by mimicking estrogen and binding to its receptors, which is a possible explanation for the links found between BPA and obesity, breast cancer, prostate cancer and early-onset puberty. The Yale authors wondered how a single exposure to BPA in the womb was able to have such a long-lasting effect. They found that BPA may also operate epigenetically, meaning BPA can change how genes, like those controlling the development of the uterus, are expressed. These changes can persist for long periods of time, and can even be passed on from generation to generation. This is enough to give anyone pause.

While the FDA is correct to request more research on BPA — and happily, the government is backing up its demand with $30 million — it has left most Americans unsure of whether they need to protect themselves from the chemical and if so, how. Even if the FDA is critical of its own regulatory structure and says its oversight is limited, for example, there is still no requirement for companies to notify the FDA if they make changes to BPA-containing can linings after they are first approved to use the chemical. But the FDA’s awareness of its lack of regulatory power is not comforting if they have inadvertently exposed millions of Americans to a dangerous chemical.

The good news is that BPA isn’t absurdly toxic. If it were, that would have been identified earlier. But more subtle effects are a still a serious concern if magnified in a population over time. If BPA functions epigenetically in humans, then the FDA’s focus on protecting babies is admirable, but perhaps shortsighted. Additionally, there are surely many more chemicals that have potentially harmful effects. We must learn from the BPA case and restructure our regulatory system to allow the agency to protect the public to the best of its ability. In the meantime, I for one am checking my plastic ware before microwaving my leftovers.