Science, Through a Policy-Maker's Lens
Allison Aiello, PhD, MS, is an associate professor of epidemiology at the University of Michigan School of Public Health, and an alumna of the Robert Wood Johnson Foundation (RWJF) Health & Society Scholars program. This post is part of a series on the program, running in conjunction with its tenth anniversary. The RWJF Health & Society Scholars program is designed to build the nation’s capacity for research, leadership and policy change to address the multiple determinants of population health.
You’ve seen it, used it, and probably even bought it. Its manufacturer claims it keeps your hands free of bacteria, and that it works better than regular old soap. For a couple decades now, Americans have been encouraged by soap manufacturers to buy anti-bacterial hand and bath soap, and many of us have taken them up on it, judging from its ubiquity on store shelves. It comes in pump bottles as well as traditional hand and bath bars, all relying on a similar active ingredient, a chemical called triclosan in liquid soaps and triclocarban in bar soaps. In fact, you can find triclosan in a range of hygiene products, including deodorants, toothpastes, mouthwashes, and more.
The marketing message behind all of them is the same: By killing bacteria—or more accurately, by stopping it from reproducing—the stuff makes us cleaner and safer.
Alas, I’ve spent years researching triclosan, and I can tell you that it’s not nearly so simple. Triclosan may have its uses, but as a soap additive, the bulk of the evidence is that it offers no particular advantage over using regular soap, while posing some worrisome threats to health and the environment. Given that, it’s a mystery to me why it’s allowed on the market years after the problems with it first came to light.
The research to date has revealed much about triclosan.
First, interventions in the community setting comparing anti-bacterial soaps with regular soaps demonstrate that triclosan works, but no better than regular soap. They both clean your hands and rid you of bacteria in roughly equal quantities.
Second, anti-bacterial soap is not indiscriminate in the bacteria it kills, and some of the bacteria it targets are good for us, performing useful functions on our skin. If we try to live bacteria-free or change the bacterial ecosystem we have on our hands, we can reduce the diversity and ecology of our natural bacteria. This imbalance may make us more vulnerable to infection when we finally are exposed to new microbes, including those types of bacteria that triclosan cannot kill.
Third, by introducing a bacteria-killing chemical into the environment, we invite other harms to ourselves and the environment. When we rinse triclosan-based soaps down the drain, the chemical begins a long journey that ends in wastewater plants, streams and rivers, where it continues its bacteria-inhibiting ways. It’s also an endocrine-disruptor, which means that it can interfere with the body’s hormone-based internal communications system. Researchers have found, for example, that it interferes with thyroid function in bullfrogs and, more recently, heart muscle development in fish, and they worry that it might have a similar effect on humans. Our work has shown that higher levels of triclosan in the urine of children and teens less than 18 years of age was associated with greater reports of allergy and hay fever in a representative sample of this age group in the U.S. population. There’s also laboratory evidence indicating that triclosan contributes to the problem of antibiotic resistance.
Because of its ubiquity in our daily lives, as well as in the environment, triclosan is now commonly found in our bodies. One study, sponsored by a triclosan manufacturer, found the chemical in 97 percent of breast milk samples from mothers tested. Another study, conducted by the Centers for Disease Control and Prevention (CDC), found it in 75 percent of the urine samples it tested in a representative sample of the U.S. population.
So, to sum up, the data tell us that the upside of using triclosan-based soaps is minimal: It makes us no cleaner or safer. Meanwhile, the downside is significant: It is in our bodies and poses a variety of risks to health and the environment.
Still, it continues to be used in consumer soaps, and this is where the mystery sets in for me.
The federal agency charged with regulating such chemicals in soaps, the Food & Drug Administration, has long since been aware of concerns about triclosan. But its efforts to explore and then act on the problems have been conducted at a genuinely glacial pace. In 1974, FDA published what it described as a “tentative, final monograph,” warning of insufficient evidence of triclosan’s safety and effectiveness. Over the years, FDA has returned to the topic several times, without making a final decision on whether to permit its use. As recently as 2010, FDA announced that it was changing the text of its website’s triclosan section, to warn consumers about tests showing harm in animals. But FDA took the view that the animal studies were not a sure indicator that the chemical is harmful to humans, and noted that the chemical is useful in toothpastes, because it helps fight gingivitis—a conclusion that is not universally shared by scientists. Beyond that, FDA has not moved.
My training as a scientist leaves me ill-prepared to understand FDA’s reluctance to act. In my discipline, we place great emphasis on the weight of the evidence. In this case, the evidence is weighty indeed: As a soap, triclosan offers little benefit over regular soap, but it comes with risks. Still, FDA seems unmoved by the weight of the evidence, insisting instead on what amounts to a smoking gun—evidence so clear that even soap manufacturers would concede that the chemical causes harm. In science, such evidence is usually elusive. We can often see the effects of a chemical, without knowing the precise mechanisms by which it acts. In this case, we recognize the mechanisms, and have gathered evidence of its adverse effects in animals, but smoking-gun-style evidence of harm to humans is difficult. So even though the weight of the evidence is clear, we get no action.
For some reason, FDA treats triclosan as if it had some constitutional right to be innocent until proven guilty beyond a reasonable doubt. My own view is that we have the evidence we need to conclude that it offers no benefit in the community setting and may introduce important human health risks, and the burden of proving safety should fall on the companies that want to sell the chemical. That’s one of many ways that policy-makers and scientists see the world through different lenses.