ECJ EUROPEAN Cleaning Journal

Researchers at the University of California, San Diego School of Medicine have reported potentially serious consequences of long-term exposure to the antimicrobial triclosan in a study published by Proceedings of the National Academy of Sciences.

The study suggests that triclosan causes liver fibrosis and cancer in laboratory mice through molecular mechanisms that are also relevant in 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 Tukey, professor in the departments of Chemistry and Biochemistry and Pharmacology.

Tukey led the study, together with Bruce Hammock, professor at University of California, Davis. The findings of the team suggest 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 tumor formation.

The American Cleaning Institute (ACI), however, argued that summaries of the study grossly misrepresent what the research actually found. Independent scientists at the UK-based Science Media Centre also took issue with some of the conclusions.

"The fact is that overdosing mice with triclosan at levels they would never likely come in contact with does not represent a realistic circumstance for humans," said Dr Paul DeLeo, ACI associate vice president, environmental safety. "We've known for decades that the mouse is not a good model for human risk assessment of triclosan."

Independent reviews of the research from the Science Media Centre comment that: "The paper does not prove the claim that triclosan use promotes tumour growth in humans."

Dr Nick Plant, Reader in Molecular Toxicology at the University of Surrey said: "The authors study only mice, and draw conclusion only on mice. Their comments on human health are very circumspect. As the authors state, it is difficult to assess if the dose they use in mice is relevant to human exposure levels, but at a simple examination it appears to be much higher than I would expect to see in a human. This further complicates extrapolation to the human situation as we are not comparing equivalent exposures.

"It is not valid to state that the effect of triclosan in mice will occur in humans as well."