Long-term exposure to triclosan—a popular antimicrobial agent in soaps, detergents, and plastics, still in use in the Philippines—has been found to promote liver cancer in mice. The study was conducted by scientists from the University of California (San Diego and Davis) and the Salk Institute for Biological Studies and was published in the journal Proceedings of the National Academy of Sciences.
In this study, the researchers fed mice with chow consisting of 0.08% triclosan [5-chloro-2-(2, 4-dichlorophenoxy)phenol]. After eight months of exposure (roughly equivalent to 18 human years), the mice showed enlarged livers and liver fibrosis. Previous studies have shown that liver fibrosis, or the formation of excess fibrous connective tissue in the liver, promotes liver cancer.
To analyze how triclosan affects liver tumor formation, the researchers injected mice once with DEN (procarcinogen diethylnitrosamine) followed by exposure to triclosan in their drinking water (200 ppm) for six months. DEN is a weak carcinogen, known to initiate tumor formation.
After six months, more than 80% of the mice exposed to DEN and triclosan developed liver tumors and these tumors were more numerous and larger compared to the ones found in mice exposed to DEN alone. Mice exposed to triclosan also had 450 times more detectable hepatocellular carcinomas (HCCs). HCC is the most common type of liver cancer and is the fourth most common type of cancer in the world.
"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, senior author of the study. Triclosan is absorbed into the human body through the skin and the gastrointestinal tract.
"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 Bruce Hammock, one of the co-authors. "Yet we could also for now retain uses shown to have health value -- as in toothpaste, where the amount used is small."
The American Cleaning Institute (ACI), however, said that the study isn't realistic.
“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 for Environmental Safety. “We’ve known for decades that the mouse is not a good model for human risk assessment of triclosan.”
“Consumers need to know that antibacterial soap ingredients like triclosan have been extensively researched, reviewed and regulated for decades. Antibacterial soaps continue to play an important role in everyday handwashing routines in homes and hospitals alike.”
ACI members include the formulators of soaps, detergents, and general cleaning products used in household, commercial, industrial and institutional settings; companies that supply ingredients and finished packaging for these products; and oleochemical producers.
FDA: On the fence
In a statement dated December 2013, the United States Food and Drug Administration (US FDA) said that [it] "does not have sufficient safety evidence to recommend changing consumer use of products that contain trclosan at this time." Triclosan is currently under review by the US Food and Drug Administration (FDA) due to previous studies linking it to hormone disruption and impaired muscle contraction. However, major manufacturers of consumer products have already started shifting away from triclosan. Procter and Gamble will remove triclosan from all of their products by the end of 2014. Triclosan will be eliminated from Unilever’s skin care and cleansing product lines by the end of 2015, and in oral care products by the end of 2017.
— TJD, GMA News
Macy Añonuevo earned her MS Marine Science degree from the University of the Philippines. She is a published science and travel writer and was a finalist in the 2013 World Responsible Tourism Awards under the Best Photography for Responsible Tourism category. Her writings and photographs may be found at www.theislandergirl.com.