- 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."