- Author: Kathy Keatley Garvey
Triclosan and trilocarban are widely used antibacterial chemicals found in cosmetics, soaps, shampoos, toothpastes, body washes and many other household products.
Hammock initiated the work on triclosan through the NIEHS/UC Davis Superfund Program that he directs, pulling together researchers from multiple colleges on campus, including the College of Agricultural and Environmental Sciences, School of Veterinary Medicine and the School of Medicine.
"The researchers under the direction of Tom Young were alarmed over the amount of triclosan in particularly the aquatic environment and its resistance to degradation during sewage treatment," said Hammock, a toxicologist and entomologist who holds a joint appointment in the UC Davis Department of Entomology and Nematology and the UC Davis Comprehensive Cancer Center.
Other work with the Superfund Program at UC San Diego, directed by Robert Tukey, showed triclosan caused tumor promotion in a unique way. The early and continued work by the Davis group on analytical methods for these materials, their biology, and running government-industry-academic workshops stimulated other researchers to link high doses of triclosan to disrupted metabolism, liver fibrosis and cancerous tumors and are reported to disrupt hormones. Although the doses used in these studies were very high they raised concerns about the long term safety of these chemicals in humans and also in the environment.
“With chemicals in the environment, we seem to treat them as all evil or perfectly safe," Hammock said. “We quickly forget that triclosan replaced some materials that were really scary--and I am not easily scared by chemicals. I hope there is no replacement in over the counter soaps - since we really do not need replacements. Scrubbing your hands is a good way to kill bacteria and soap is pretty toxic itself.”
“I think the reputation of triclosan and trilocarban are bad enough with environmental groups that whether they are banned or not --they will continue to diminish in use throughout the world except where there is a true benefit—a good thing,” Hammock said.
The FDA declared Sept. 5 that it was “issuing this final rule establishing that certain active ingredients used in over-the-counter (OTC) consumer antiseptic products intended for use with water (referred to throughout this document as consumer antiseptic washes) are not generally recognized as safe and effective (GRAS/GRAE) and are misbranded. FDA is issuing this final rule after considering the recommendations of the Nonprescription Drugs Advisory Committee (NDAC); public comments on the Agency's notices of proposed rulemaking; and all data and information on OTC consumer antiseptic wash products that have come to the Agency's attention.”
“No drug is all good or all bad; everything is a benefit/risk equation," Hammock told reporter Monique Brouillete in an article published in the Sept. 2 edition of Scientific American. Brouillette added: “Still, Hammock says, because triclosan and other chemicals in antibacterial soaps show no benefit over plain soap they should not be used by the general public.”
Earlier this year NIEHS selected a paper from the UC San Diego and UC Davis Superfund Programs linking the long-term use of antibacterial agent triclosan with liver fibrosis and cancer as one of the top papers of 2015. The groundbreaking study, published in the PNAS, was led by Tukey and Hammock.
In its January newsletter, NIEHS ranked the triclosan study No. 2 in grant-funded research published in 2015. Some 2514 NIEHS-funded research papers were published in 2015.
The paper, “The Commonly Used Antimicrobial Additive Triclosan is a Liver Tumor Promoter,” drew widespread attention from news media, scientists and consumers. The triclosan research team exposed mice to triclosan for six months, which equates to approximately 18 human years. Triclosan-treated mice exhibited cell proliferation, liver fibrosis, and proinflammatory responses. This is the type of environment within which live cancer in humans can form, the researchers said.
The team also chemically induced liver tumors in the mice and found that the mice exposed to triclosan showed a large increase in tumor multiplicity, size, and incidence compared to unexposed mice at high doses. Tukey said the findings suggest that triclosan's negative effects on the liver may result from interference with the constitutive androstane receptor, which plays a role in clearing foreign chemicals from the body.
Hammock was featured in the January 2015 edition of Chemical Research in Toxicology and in the Sept. 4, 2014 edition of Newsweek. In the Newsweek piece, "Is Cancer Lurking in Your Toothpaste? (And Your Soap? And Your Lipstick?" Hammock called triclosan “quite a good antimicrobial” that belongs in the hospital, not on the kitchen counter. “There's no reason for it to be there (in hand and dish soaps)" he told reporter Alexander Nazaryan.
Today Hammock considers the triclosan story, "a story with a good ending."
"All chemicals produced in high volume with exposure to humans and to the environment are of concern, when high volume uses are associated with little or no benefit the uses need to be eliminated," he said. "This is the case with triclosan and triclocarban in soap. They were used in hand soap as ‘value added products' with little or no benefit. Public outcry driven by good science resulted in consumer pressure to eliminate them and this was occurring rapidly even without regulation. The government then offered producers the chance to show safety and benefit, and all of them decided the negative science, size of the market and consumer preference was not worth the effort so they are now legally gone from these products."
- Author: Kathy Keatley Garvey
The ground-breaking study, published in the Proceedings of the National Academy of Sciences, was led by NIEHS-funded scientists Robert Tukey, director of the Superfund Research Program at UC San Diego and Bruce Hammock, director of the UC Davis Superfund Research Program.
In its January newsletter, NIEHS ranked the triclosan study No. 2 in grant-funded research published in 2015. Some 2514 NIEHS-funded research papers were published in 2015. The institute, part of the National Institutes of Health, also singled out 27 other papers for special recognition.
Triclosan is a widely used antibacterial chemical found in cosmetics, soaps, shampoos, toothpastes and many other household products, said Hammock, who holds a joint appointment with the UC Davis Department of Entomology and Nematology and the UC Davis Comprehensive Cancer Center. “This study, using laboratory mice, raises concerns about the safety of triclosan in humans,” he said. These findings add to earlier reports triclosan can disrupt hormones and impair muscle contraction.
The paper, “The Commonly Used Antimicrobial Additive Triclosan is a Liver Tumor Promoter,” drew widespread attention from news media, scientists and consumers.
The team also chemically induced liver tumors in the mice and found that the mice exposed to triclosan showed a large increase in tumor multiplicity, size, and incidence compared to unexposed mice.
Hammock said the findings suggest that triclosan's negative effects on the liver may result from interference with the constitutive androstane receptor, which plays a role in clearing foreign chemicals from the body.
Other co-authors of the paper are Mei-Fei Yueh, Koji Taniguchi, Shujuan Chen, R. M. Evans and Michael Karin, all of UC San Diego; and Ronald M. Evans, Salk Institute for Biological Studies.
Hammock was featured in the January 2015 edition of Chemical Research in Toxicology, and in the Sept. 4, 2014 edition of Newsweek in a piece titled "Is Cancer Lurking in Your Toothpaste? (And Your Soap? And Your Lipstick? Hammock called triclosan “quite a good antimicrobial” that belongs in the hospital, not on the kitchen counter, and told reporter Alexander Nazaryan, “There's no reason for it to be there" (in hand and dish soaps).
The research was funded, in part, by U.S. Public Health Service grants ES010337, GM086713, GM100481, A1043477, ES002710 and ES004699.
Related Links:
NIEHS newsletter
PNAS paper
- Author: Kathy Keatley Garvey
The article, “Triclosan Promotes Liver Tumor Development,” highlights the team's discovery that triclosan, an antimicrobial commonly found in soaps, shampoos, toothpastes and many other household products, causes liver fibrosis and cancer in laboratory mice through molecular mechanisms that are also relevant in humans.
Robert Tukey, a UC San Diego professor in the departments of Chemistry and Biochemistry and Pharmacology, led the study with Hammock, who has a joint appointment in the Department of Entomology and Nematology, and Comprehensive Cancer Center at UC Davis. Tukey and Hammock are directors of National Institute of Environmental Health Sciences Superfund Programs at their respective campuses.
The team, including San Diego-based scientist Mei-Fei Yueh, investigated long-term exposure to triclosan in mice by treating them with triclosan for 6 months, which is roughly equivalent to 18 human years. They then compared the livers of exposed mice with those of mice not exposed to triclosan. Researchers found that chronic exposure to triclosan in mice caused liver damage and liver cell death. They also discovered that triclosan exposure in mice increased susceptibility to tumor formation through enhanced cell growth, liver fibrosis (excessive accumulation of proteins in the liver), and proinflammatory responses, which are circumstances within which human cancer forms.
The scientists found that triclosan interferes with a nuclear receptor, known as the constitutive androstane receptor, that plays a role in detoxifying the blood. To compensate for this interference, the liver overproduces cells, which can lead to fibrosis and cancer.
PNAS co-authors included Koji Taniguchi, Shujuan Chen and Michael Karin, UC San Diego; and Ronald M. Evans, Salk Institute for Biological Studies.
Related Links
The Dirty Side of Soap
PNAS Paper, "The Commonly Used Antimicrobial Additive Triclosan Is a Liver Tumor Promoter"
Long-term exposure to triclosan, an antimicrobial commonly found in soaps, shampoos, toothpastes and many other household items, may potentially have serious health consequences, according to a team of University of California researchers, including Bruce Hammock, distinguished professor, UC Davis Department of Entomology and Nematology.
Their research, published Nov. 17 in the Proceedings of the National Academy of Sciences, shows 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 H. Tukey, professor in the departments of Chemistry & Biochemistry and Pharmacology, UC San Diego School of Medicine
Tukey led the study with Hammock, who holds a joint appointment with the UC Davis Comprehensive Cancer Research Center. They direct the National Institute of Environmental Health Sciences (NIEHS) Superfund Programs at their respective campuses.
The team, including Mei-Fei Yueh, 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 tumors. Their tumors 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 tumor 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. Triclosan is also common in the environment: It is one of the seven most frequently detected compounds in streams across the United States.
“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,” Hammock said. “Yet we could also for now retain uses shown to have health value — as in toothpaste, where the amount used is small.”
Triclosan is already under scrutiny by the FDA, due to its widespread use and recent reports that it can disrupt hormones and impair muscle contraction.
Co-authors include Koji Taniguchi, Shujuan Chen and Michael Karin, UC San Diego; and Ronald M. Evans, Salk Institute for Biological Studies. (See PNAS paper)
This research was funded, in part, by U.S. Public Health Service grants ES010337, GM086713, GM100481, A1043477, ES002710 and ES004699.
Author: Heather Buschman
UC San Diego Health Sciences
hbuschman@ucsd.edu
Phone: (619) 543-6163
(Editor's Note: Hammock was featured in the Sept. 4 edition of Newsweek in a piece titled "Is Cancer Lurking in Your Toothpaste? (And Your Soap? And Your Lipstick? Hammock called triclosan “quite a good antimicrobial” that belongs in the hospital, not on the kitchen counter, wrote reporter Alexander Nazaryan, who quoted Hammock as saying: “There's no reason for it to be there" (in hand and dish soaps).