Women wash hands in white sink with good soapy water
Look around any bathroom or cleaning closet in the US and you’re likely to find a product enriched with an antimicrobial chemical. One of the most common of these, triclosan, is found in about 75 percent of antibacterial hand soaps and is easy to spot in a range of other goods from toys to toothpaste. It has also been found in about 75 percent of Americans’ urine. But despite their ubiquity, these antimicrobials go largely unregulated and scientists don’t know about their health effects.
This is according to an opinion piece published on Thursday in Science, Alyson Yee and Jack Gilbert, microbiologists at the University of Chicago, are calling for that to change. They explain how little data we have on the chemicals – and some of it is even contradictory. Still, it’s clear that our exposure may begin in the womb and that the chemicals have the potential to mess up our microbiomes — the communities of microbes within and on us that greatly affect our health. Such microbial disorders have been linked to a variety of conditions, from neurological disorders to arthritis, allergies, obesity and irritable bowel disease.
As such, scientists should prioritize figuring out whether the chemicals that are already all around us are doing any harm, Yee and Gilbert argue.
To make their case, the pair first explained how easy it is to come into contact with antimicrobials: they’re in wipes, toothpaste, cosmetics, cutting boards, detergents, toys, plastics and hand soaps. And they easily sink into the skin if they don’t get into the mouth via a toothbrush or contaminated hand. Studies have found evidence of exposure in the womb and around birth, particularly in hospitals, which rely heavily on antimicrobials to combat the spread of germs to vulnerable patients. Exposure this early, while the microbiome is still establishing itself, could have lasting but subtle health consequences, the authors note.
As Ars has written before, triclosan and its ilk have the ability to drive the development of drug resistance and help drug-resistant microbes. But Yee and Gilbert mainly focus on the possibly inconspicuous damage, the damage to the microbiome. Studies on zebrafish (which can be used as model organisms for vertebrate development) and flathead minnows have both found triclosan to alter gut microbiomes. Those studies also suggested that the gut microbiomes can recover after triclosan is removed. However, a study of microbes in waterways found that exposure to triclosan caused permanent changes in communities.
In a study from earlier this year, researchers at Stanford and Cornell tried to look at such effects in humans. They divided 13 volunteers into two groups: One group used triclosan-containing products for four months and then switched to non-triclosan-containing products for another four months. The other group did the opposite. In the end, the researchers found no statistically significant differences or changes in their gut or mouth microbiomes. Still, the researchers did not test for antimicrobials other than triclosan. And the volunteers still had triclosan in their urine if they didn’t intentionally use triclosan-containing products.
“It is also possible that exposure to triclosan is so ubiquitous, starting as early as prenatal exposure, that the human microbiota has already adapted,” Gilbert and Yee point out. Researchers need to do much more research, the two conclude.
Meanwhile, some regulators are already starting to worry about the problem. The European Union and the state of Minnesota have issued a partial ban on the chemicals in commercial products. The U.S. Food and Drug Administration is currently reviewing data on the safety and benefits of triclosan in hand soaps. However, one data point seems clear in this issue: studies have clearly shown that under normal hand washing conditions, antibacterial hand soaps are no better at ridding dirty hands of bacteria than regular soap and water.
Science2016. DOI: 10.1126/science.aag2698 (About DOIs).