- 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).
- Author: Kathy Keatley Garvey
Triclosan researcher Bruce Hammock, distinguished professor of entomology at the University of California, Davis, is featured in the Sept. 4 edition of Newsweek in a piece titled "Is Cancer Lurking in Your Toothpaste? (And Your Soap? And Your Lipstick?)"
Writer Alexander Nazaryan led with: "Since cancer seems to be an ever-present enemy, we greet the appearance of its lethal emissaries in prosaic objects with a morbid lack of surprise: carcinogens lurks in coffee, hamburgers, rugs, dry-cleaned clothes, even peanut butter. And it may apparently reside in one of the most popular toothpastes on the market, a toothpaste you've probably thrown into your own shopping cart with nary a second thought."
Of Hammock, he wrote:
"But for others, the chemicals aren't dangerous if used with moderation. Dr. Bruce D. Hammock, for example, runs the Laboratory of Pesticide and Biotechnology at UC Davis and was one of the investigators involved in the study on triclosan and triclocarban. 'There are real risks to triclosan,' Hammock says. 'And there are real benefits.' He welcomes more research into its effects on the human body.
Hammock called triclosan “quite a good antimicrobial” that belongs in the hospital, not on the kitchen counter, Nazaryan wrote. He quoted Hammock: “There's no reason for it to be there" (in hand and dish soaps).
See the full story in Newsweek.
In addition to his duties in the UC Davis Department of Entomology and Nematology (see his lab research website), Hammock holds a joint appointment with the UC Davis Comprehensive Cancer Center and directs the campuswide Superfund Research Program, National Institutes of Health Biotechnology Training Program, and the National Institute of Environmental Health Sciences (NIEHS) Combined Analytical Laboratory.
The UC Davis provost named him a distinguished professor in 2003. Hammock is a fellow of the Entomological Society of America, a member of the prestigious National Academy of Sciences, and the recipient of the 2001 UC Davis Faculty Research Lecture Award and the 2008 Distinguished Teaching Award for Graduate and Professional Teaching.
Related News:
See the Aug. 13, 2012 UC Davis news release expanding on triclosan: "Triclosan, an antibacterial chemical widely used in hand soaps and other personal-care products, hinders muscle contractions at a cellular level, slows swimming in fish and reduces muscular strength in mice, according to researchers at the University of California, Davis, and the university of Colorado. The findings appear online in the Proceedings of the National Academy of Sciences of the United States of America."
- Author: Kathy Keatley Garvey
The controversial antibacterial chemical is grabbing nationwide attention with the recent cover story of “Triclosan Under the Microsope” in Chemical Engineering News. The article quotes Bruce Hammock, a UC Davis distinguished professor who holds a joint appointment in the Department of Entomology and Nematology and the UC Davis Comprehensive Cancer Center.
“I'm getting love notes and hate mail,” he said, adding "“My colleagues and I are continuing to look at the positive and negative aspects of triclosan. It clearly has some negative effects on mammalian biology, but it is a very potent microbial and quite inexpensive, and relatively safe.”
Triclosan, first used in healthcare settings in the 1960s, is now found in products throughout the home—in everything from hand sanitizers, toothpastes, mouthwashes, deodorants and cosmetics to beddings, clothes, toys, carpets and trash bags.
Last month Minnesota became the first state to ban the ingredient in soaps and cleaning products. Other states concerned about the chemical's effects on human and environmental health may follow.
Hammock said that he and UC Davis colleagues molecular biologist David Mills and chemist Bruce German are now looking at the effects on gut bacteria.
“And, with Bob Tukey at UC San Diego, we are looking at enzyme induction in mammals and possible health risks,” Hammock said. Tukey, professor of pharmacology and chemistry and biochemistry, directs the UCSD Superfund Basic Research Program, while Hammock directs the UC Davis Superfund Program.
The U.S. Environmental Protection Agency in 1998 estimated that the U.S. produces more than 1 million pounds of triclosan annually, and that scientists can detect the chemical in waterways, aquatic organisms, and in human urine, blood and breast milk.
Concern over the controversial compound is swirling with the June 23rd publication of “Triclosan Under the Microscope.”
Hammock told author Jyllian Kemsley that when medical providers first started using triclosan as a surgical scrub, “it replaced some really scary compounds.”
He said that “Triclosan is much less toxic, more effective, and more biodegradable” than hexachlorophene and other common biocides of the time.
Wrote Kemsley: “But then triclosan made its way out of the operating room and into mass consumer products. In that context, its toxicity profile and environmental lifetime make the cost-benefit analysis murkier.”
“To me that doesn't say rush out and ban it,” Hammock told her, advocating careful consideration for mass use. He said washing hands with plain soap and water will likely fit most needs. Triclosan is a very effective anti-microbial but probably it is overused in many cases.
Kemsley wrote that some people may be more susceptible to harm, “such as those with genetic variations that reduce their ability to metabolize triclosan, leaving them with higher blood concentrations.” Some scientists worry if the toxicity level is worth it to reduce disease and also whether it promotes drug resistance.
Kemsley drew attention to the 2012 UC Davis study that shows that triclosan hinders cardiac and skeletal muscle contraction in mice and fish. The study, published in the Proceedings of the National Academy of Sciences (PNAS) and authored by a 13-member research team headed by Isaac Pessah and Nipavan Chiamvimonvat of the School of Veterinary Medicine and Hammock, found that triclosan hinders muscle contractions at a cellular level, slows swimming in fish and reduces muscular strength in mice.
“The effects of triclosan on cardiac function were really dramatic,” Chiamvimonvat, professor of cardiovascular medicine, related following the PNAS publication. “Although triclosan is not regulated as a drug, this compound acts like a potent cardiac depressant when administered at high doses in our models.”