Long-term exposure to an ingredient found in common soaps, shampoos, and toothpastes has been linked to liver tumors in mice.
The antimicrobial agent triclosan could also impose serious health consequences on humans who use seemingly-innocent consumer products, UC Davis reported. A new study reveals the ingredient causes liver fibrosis and cancer in mice through a molecular mechanism that translates to humans.
"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, particularly when combined with other compounds with similar action," said Robert H. Tukey, a professor in UC San Diego's departments of Chemistry & Biochemistry and Pharmacology.
Researchers exposed mice to triclosan for six months (which is equivalent to about 18 human years), and found they were more susceptible to chemical-induced liver tumors that were also larger than those seen in non-exposed rodents.
The researchers believe triclosan interferes with a protein called the "constitutive androstane receptor," which works to clear invasive chemicals from the body. To compensate for the loss the liver slowly begins to turn fibrotic, eventually promoting tumor formation.
Triclosan is one of the most widely-used consumer antibacterial ingredients, and has been found in 97 percent of breast milk and 75 percent of tested urine. The FDA is currently taking a closer look at the ingredient because of recent reports that it can also impair muscle contractions and interfere with hormones.
"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," said co-leader Professor Bruce D. Hammock, who has a joint appointment in the Department of Entomology and Nematology, and Comprehensive Cancer Center at UC Davis. "Yet we could also, for now, retain uses shown to have health value - as in toothpaste, where the amount used is small."
The findings were published Nov. 17 in the journal Proceedings of the National Academy of Sciences.
