Common antibacterial in soap may harm liver

Long-term exposure to triclosan, found in soaps, shampoos, toothpastes and many other household items, may cause liver fibrosis and cancer, an alarming study suggests.

"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, professor at University of California, San Diego School of Medicine.

The risk is particularly high when triclosan is combined with other compounds with similar action, Tukey noted.

The researchers found that triclosan disrupted liver integrity and compromised liver function in mouse models.

Mice exposed to triclosan for six months (roughly equivalent to 18 human years) were more susceptible to chemical-induced liver tumours. Their tumours were also larger and more frequent than in mice not exposed to triclosan.

The study suggests triclosan may do its damage by interfering with the constitutive androstane receptor, a protein responsible for detoxifying (clearing away) foreign chemicals in the body.

To compensate for this stress, liver cells proliferate and turn fibrotic over time. Repeated triclosan exposure and continued liver fibrosis eventually promote tumour formation.

Triclosan is perhaps the most ubiquitous consumer antibacterial. Studies have found traces in 97 percent of breast milk samples from lactating women and in the urine of nearly 75 percent of people tested.

The study appeared in the journal Proceedings of the National Academy of Sciences.