Soap may have a dirty secret, according to a new study.
Findings of an experiment published Nov. 17 in the journal Proceedings of the National Academy of Sciences have linked triclosan, an anti-bacterial additive used in soap and toothpaste, to an increased risk of liver cancer in mice.
“Triclosan’s increasing detection in environmental samples and its increasingly broad use in consumer products may overcome its moderate benefit and present a very real risk of liver toxicity for people, as it does in mice,” said Robert Tukey, a professor at the University of California, San Diego School of Medicine, where the research was performed.
In the experiment, mice were exposed to high levels of triclosan in food and drinking water for six months. The mice who received the triclosan were much more susceptible to liver tumors than a control group who received no triclosan, according to researchers.
The type of cancer the mice in the study developed is called hepatocellular carcinoma, and is the third most common cause of worldwide cancer deaths.
However, there is disagreement as to the extent of the risk the germicide poses. The exposure levels used in the experiment were much higher than those humans generally experience, and effects on mice do not necessarily reflect effects on humans.
The current statement from the Food and Drug Administration website reads that “Triclosan is not currently known to be hazardous to humans. But several scientific studies have come out … that merit further review.”
The researchers themselves admit that triclosan is “not a direct carcinogen,” because it does not mutate DNA. However, Tukey called it a “tumor promoter” that encourages tumor growth after mutation has occurred due to some other factor.
Concerns about triclosan are not new, and most center on the risk-reward ratio of the additive.
The FDA announced last year that anti-bacterial soaps with triclosan may work no better than regular soap and water, and could even be causing harm by supporting antibiotic resistance.
There is some evidence, however, that toothpaste that contains triclosan prevents gingivitis better than toothpaste that does not contain the germicide.
“We could reduce most human and environmental exposures by eliminating uses of triclosan that are high volume, but of low benefit, such as inclusion in liquid hand soaps,” Bruce D. Hammock, a professor at University of California, Davis, suggested in a statement. “Yet we could also for now retain uses shown to have health value — as in toothpaste, where the amount used is small.”
Even if they disagree on whether triclosan should be permitted in products in the meantime, most researchers seem to agree that further study is necessary to determine its positive or negative effects.