Bisphenol-A, better known as BPA, is the building block of polycarbonates and epoxy resins, plastics that have facilitated modern life. (They're in microwave containers, baby bottles, laptops, and even canned foods.) Tiny amounts circulate in the bodies of more than 90 percent of Americans. And now a team of Chinese and U.S. scientists says it has linked the stuff to sexual dysfunction in men. Even before today's news, plenty of people were getting the willies about BPA. Should this news make you feel less virile? Let's take a closer look.
Six years ago, De-Kun Li, a senior scientist at Kaiser Permanente's research arm, and his colleagues were already alarmed about BPA because of a steady stream of studies showing that BPA alters tissues in the reproductive organs and offspring of rats and mice. But there's a heated debate among statisticians, toxicologists, and endocrinologists about which animal models are relevant to human disease and about the paradoxical way BPA seems to work. Unlike typical poisons or carcinogens, more is not always worse and less is not always better. In many of the studies, BPA changes animal tissues only at specific low concentrations and only at particular stages of the life cycle.
"BPA is not a toxin. It's not going to kill you," Li told me in an interview. It's a form of artificial estrogen that could disrupt the endocrine system, where hormone signals like estrogen and testosterone subtly influence the behavior of cells throughout our bodies. Extra estrogen in females isn't good (it's known to increase breast cancer risk, for example), and it can interfere with testosterone in men.
But there's precious little demonstration that this is happening in people and not just in lab animals. "The argument ultimately comes down to: 'Where is the human evidence?' " says Li. That poses a dilemma. Li believes animal evidence alone won't overcome industry's vigorous defenses or satisfy government regulators—but he knows no university oversight panel will ever approve human BPA experiments.
Li did the next best thing, finding four factories in China where large quantities of BPA are generated (directly or in producing other materials) and studying the men who worked there. If BPA isn't dangerous in such places, he figured, we don't need to worry. He split up the exposed workers into three levels based on personal air sample monitors, job roles, and length of employment, and confirmed with air and urine sampling that they were exposed to much higher levels of BPA than similar men in the same city who didn't work at the factories.
The research identified a pattern: Higher exposures led to more sexual frustration. The men in the factories had four times the rate of erectile dysfunction of the men who didn't work there. They complained about ejaculation problems seven times as much. And overall, they were four times as likely to be disappointed with their sex life.
This study deserves cautious attention. If the factory workers inhaled BPA particles in the air, the substance went directly into their bloodstream. For most of the rest of us, BPA is a contaminant in the food we eat and goes through "first-pass metabolism" in the digestive tract. Why does the delivery route matter? Because a key question in the BPA debate is which experiments best model the constant, low-dose turnover modern humans experience in daily life. Toxicologists who defend BPA say it's quickly processed by the liver, which changes BPA into an inactive compound, and excreted. That's mostly but not entirely true—"raw" BPA can still be found in your bloodstream. To achieve levels common in humans, many scientists inject BPA directly into animals. Oral-only purists dismiss those efforts, and for the same reason. I'll be unsurprised if the same vocal challengers of hundreds of animal research studies dismiss Li's work as well.
It struck me that one part of Li's study should be of great interest to American men, in our offices and automated factories. We're more akin to the men who were used as controls in the study: the men who live in the same city but who don't work in the BPA factories. They were still exposed, of course, but in the same way we are here, by BPA in plastics infiltrating the food we eat. The urine BPA concentrations in Li's control groups are also similar to those seen in Americans. Their reported sexual dysfunction is similar to that seen in surveyed American men.
I shared my hypothesis with Li. He was way ahead of me. The next paper he's publishing will break down the control population to see if different levels of BPA correlate with the sexual complaints. That study will mean much more to American men.
My take is that BPA is still among our least likely excuses for sexual misfires. Simply being between 40 and 70 years old gives you a fifty-fifty chance of having a minor malfunction the next time you're with your partner. ED is so common that stress (or even a pessimistic attitude) generates odds similar to those Li reported in the BPA-bathed factory workers. Combine psychology and relationship variables with the better understood "organic" mechanisms (diabetes, heart disease, drinking, smoking, drug side effects), and avoiding BPA would have to rank pretty low on your personal to-do health list. After you've controlled your cholesterol, blood pressure, resting heart rate, blood sugar, etc., by all means attempt to limit your BPA exposure.
But good luck with that. While baby bottles are going BPA free, not even Kaiser Permanente, which cross-examines its vendors about a whole list of suspect chemicals in the products it buys, can find out much about the BPA in anything else. Fully informing consumers about the chemicals in their homes may take an act of Congress, and that could give the willies to a whole new set of people.