A chemical ingredient of cosmetics, soaps, detergents, shampoos and toothpaste has been found to trigger liver cancer in laboratory mice, raising concerns about how safe it is for humans, scientists said. 
 
 Triclosan, a commonly used anti-bacterial agent added to bathroom and kitchen products, promotes the growth of liver tumours in mice fed relatively large quantities of the substance, a study has found. 
 
 The research is the latest to link triclosan with cancer and liver disease, but other scientists have urged caution over the findings suggesting that they do not prove a direct causal link between the chemical and the ill health of people exposed to it. 
 
 The study found that mice fed 3 grams of food containing 0.08 per cent triclosan daily for six months suffered liver damage and were more susceptible to liver tumours induced by other carcinogenic chemicals. 
 
 By comparison, one gram of toothpaste contains about 0.03 per cent triclosan, and six months in mice is equivalent to about 18 years in humans, the researchers pointed out. 
 
 However, the scientists who carried out the latest study, published in the journal Proceedings of the National Academy of Sciences, said that the link between triclosan and liver cancer in laboratory mice is relevant to human health because the chemical may cause similar changes in people. 
 
 “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, particularly when combined with other compounds with similar action,” said Professor Robert Tukey of the University of California, San Diego. 
 
 The study suggested that triclosan is damaging to the liver by interfering with a protein called constitutive androstane receptor, which helps to detoxify the blood. To compensate for this interference, the liver overproduces cells, causing fibrosis and cancer, the scientists said. 
 
 Traces of triclosan, a synthetic compound not found in nature, have been found in the breast milk of up to 97 per cent of lactating women and the urine of three quarters of people tested, the researchers said. 
 
 Concerns about its possible health effects of triclosan have resulted in an investigation by the US Food and Drug Administration, which regulates its use in America. The FDA said that it does not have enough safety evidence to recommend any change to its use in consumer products. 
 
 However, Professor Bruce Hammock of the University of California, Davis and a co-author of the study, suggested that the latest findings could lead to changes in the advice to consumers. 
 
 “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,” Professor Hammock said. 
 
 “Yet we could also for now retain uses shown to have health value – as in toothpaste, where the amount used is small,” he said. Triclosan has been shown for instance to help the treatment of gum disease. 
 
 However, other scientists were not convinced of the risk to human health. 
 
 “Firstly, the mice used in the study were primed with a tumour-promoting chemical before being exposed to triclosan, which humans would not be. And the concentrations of triclosan used were much higher than those found in the environment,” said Oliver Jones of the University of Melbourne in Australia. 
 
 Professor Alan Boobis, a pharmacologist at Imperial College, London, said: “Studies in primates showed no hepatic [liver] damage at doses greater than those used in the present study, when administered for 12 months. Whilst it is possible that the carcinogenic effect in mice is relevant to humans, it should be noted that mouse liver tumours are induced by many chemicals, and often they are not relevant to humans.” 
 
 Triclosan is a widely-found pollutant 
 
 Triclosan was first developed in the early 1970s for use in surgical hospital scrubs and since then it has become the most ubiquitous anti-bacterial component of a wide range of consumer products ranging from shower gel to floor wax. 
 
 Its use has increased significantly in recent years with the result that it is a widely-found pollutant. About 1,500 tons of triclosan are produced worldwide each year and much of it ends up in rivers and streams – it is among the seven most commonly-detected compounds in waterways in the United States. 
 
 Concerns about its possible health effects led to the US Food and Drug Administration (FDA) ordering an inquiry. So far, however, the evidence does not warrant a change in advice to consumers, it said. 
 
 Some studies have linked it with cancer, others with hormone regulation – triclosan may mimic female hormones and so act as a “gender bender” chemical. Other research involving bacteria has even suggested that it could play a role in promoting resistance to antibiotics. 
 
 However, other studies have shown that triclosan is beneficial to human health. A 1997 study by the FDA of evidence presented by Colgate showed that triclosan is effective in preventing gingivitis – bacterial gum disease. 

 Still a study in August from the University of California, San Francisco, found that about three-fourths of doctors and nurses had triclosan in their urine, and another study earlier this year found triclosan in the urine of 100 percent of pregnant women tested in Brooklyn. Because triclosan-infused products have been so widely used for many years, exposure to the chemical entirely is unavoidable. It is among the most common chemicals to be detected in streams. 
 
 "The result that it led to liver fibrosis was startling to us," Tukey said. The researchers also noted a similar effect in kidneys. Their findings suggest that triclosan does not cause liver tumors by itself, in that it does not mutate DNA. But it does promote tumor formation once a mutation has occurred. Liver cancer (hepatocellular carcinoma, specifically) is the world's number-three cause of cancer death. 
 
 “If non-triclosan-containing soaps are available, use the alternative," said Paul Blanc, a professor of medicine at UCSF, earlier this year in a press statement. "This is based on the precautionary principle–that is, if you don’t know for certain that something is unsafe, it’s better to err on the side of caution.” 
 
 Pair that with findings from the FDA last December that "there is currently no evidence that [antibacterial soaps] are any more effective at preventing illness than washing with plain soap and water," and the case against them is pretty clear. 
 
 So is the point that this sort of chemical should be tested for safety before it's introduced so widely? 
 
 "Well," Tukey said, "that would be a good scenario." 
 
 To know the effects in humans would require clinical trials, he noted, which have not happened. "We aren't saying that triclosan causes cancer," Tukey said. "We're just saying that with constant exposure, this environmental agent, which is extremely ubiquitous, can promote development of tumors." Because, you know, in the right amount, everything is toxic. "If one can avoid it," he said. "I would avoid it." 
 
 So once again, in attempt to become extremely healthy by ridding ourselves of bacteria, we may have actually become less so. 

 Triclosan [5-chloro-2-(2,4-dichlorophenoxy)phenol; TCS] is a broad-spectrum antimicrobial agent that has become one of the most common additives used in consumer products. As a result, TCS has significantly affected the environment and has been frequently detected in human body fluids. Through a long-term feeding study, we found that TCS enhances hepatocyte proliferation, fibrogenesis, and oxidative stress, which, we believe, can be the driving force for developing advanced liver disease in mice. Indeed, TCS strongly enhances hepatocarcinogenesis after diethylnitrosamine initiation, accelerating hepatocellular carcinoma (HCC) development. Although animal studies require higher chemical concentrations than predicted for human exposure, this study demonstrates that TCS acts as a HCC tumor promoter and that the mechanism of TCS-induced mouse liver pathology may be relevant to humans. 
 
 Abstract 
 
 Triclosan [5-chloro-2-(2,4-dichlorophenoxy)phenol; TCS] is a synthetic, broad-spectrum antibacterial chemical used in a wide range of consumer products including soaps, cosmetics, therapeutics, and plastics. The general population is exposed to TCS because of its prevalence in a variety of daily care products as well as through waterborne contamination. TCS is linked to a multitude of health and environmental effects, ranging from endocrine disruption and impaired muscle contraction to effects on aquatic ecosystems. We discovered that TCS was capable of stimulating liver cell proliferation and fibrotic responses, accompanied by signs of oxidative stress. Through a reporter screening assay with an array of nuclear xenobiotic receptors (XenoRs), we found that TCS activates the nuclear receptor constitutive androstane receptor (CAR) and, contrary to previous reports, has no significant effect on mouse peroxisome proliferation activating receptor α (PPARα). Using the procarcinogen diethylnitrosamine (DEN) to initiate tumorigenesis in mice, we discovered that TCS substantially accelerates hepatocellular carcinoma (HCC) development, acting as a liver tumor promoter. TCS-treated mice exhibited a large increase in tumor multiplicity, size, and incidence compared with control mice. TCS-mediated liver regeneration and fibrosis preceded HCC development and may constitute the primary tumor-promoting mechanism through which TCS acts. These findings strongly suggest there are adverse health effects in mice with long-term TCS exposure, especially on enhancing liver fibrogenesis and tumorigenesis, and the relevance of TCS liver toxicity to humans should be evaluated.
– A chemical found in most antibacterial soaps may be fighting off germs at the cost of causing liver damage. There have been question marks around triclosan for some time—the FDA warned last year that antibacterial soap could be harmful, and Minnesota banned the ingredient this year—but new research finds it could be a lot more dangerous than thought, the Atlantic reports. The study linked the chemical to liver damage and tumors in mice, the Independent reports, and though it wasn't found to actually cause cancer, the changes observed in the mice's bodies "resemble the environment within which human liver cancer forms," the researchers say. Triclosan is found in around 75% of germ-killing soaps, as well as in products like floor waxes, toothpaste, and cosmetics. The study, published in the Proceedings of the National Academy of Sciences journal, says triclosan—which some manufacturers have already started to phase out—appeared to make the mice more susceptible to liver disease, and promoted the growth of tumors once they appeared. Researchers say the chemical is of concern because it is so prevalent and suggest many of its uses should be eliminated. Exposure could be limited by removing triclosan from uses of "high volume, but of low benefit," like hand soap, a study co-author says, while retaining "uses shown to have health value—as in toothpaste, where the amount used is small." (The FDA took 40 years to consider the use of triclosan, leading to calls to completely change how we regulate chemicals.)