Ciba defends antibacterial triclosan in soap

Antibacterial debate

16 June 2008 00:00  [Source: ICB]

Some antibacterial soaps provide lasting protection from a wide range of bacteria. But there are concerns they are unnecessary, and could even harm the environment

Is criticism of antibacterial agents, such as triclosan, fair? Give us your views through ICIS connect

Anna Jagger/London

WASHING WITH soap and water is an extremely effective way of cleaning our hands. So why do we need antibacterial soaps?

Since the development of the antimicrobial agent triclosan by Swiss specialty chemical company Ciba in the 1960s, demand for antibacterial soaps has been growing. Global sales of the biocide component of personal care products are estimated at $350m-400m (€225m-289m)/year, and are rising at a rate of 3-7%/year.

Triclosan, a phenoxyphenol antimicrobial, is now one of the most prevalent biocide ingredients in consumer liquid hand soaps. Ciba manufactures the product, branded Irgasan DP300, in Grenzach, Germany. The company remains the main triclosan manufacturer, although there are also some producers in Asia.

The key benefit of using soap containing triclosan is that the triclosan stays on the skin after washing and provides an additional layer of hygienic protection, says Klaus Nussbaum, head of Ciba's hygiene business. In other words, soaps containing triclosan are not only bactericidal, because they can kill bacteria, but they are also bacteriostatic, because they can inhibit the growth or reproduction of bacteria.

While the alkaline conditions provided by plain soap are bactericidal, he says, they are not bacteriostatic. "Not all bacteria disappear with an alkaline handwash. The big advantage of Ciba Irgasan is its good affinity on human skin at low concentrations, providing a long-lasting effect."

Depending on the triclosan concentration - generally 0.2-0.3% for consumer applications - the product can prevent a strong growth in bacteria on skin for up to 12 hours, he says.

The arguments for adding products such as triclosan and its cousin triclocarban to soap are convincing, but some researchers question the benefits. A review conducted by US scientists from the University of Michigan, Columbia University and Tufts University, suggests that soaps containing added ingredients such as triclosan in liquid soap and triclocarban in bar soap do not show a benefit above and beyond plain soap in the consumer environment.

The review, published last year in the academic journal Clinical Infectious Diseases, assesses studies that have examined the efficacy of products containing triclosan compared with the efficacy of plain soap in the community setting. Much of the research was conducted in the US, although the review includes studies conducted in less developed areas such as Bangladesh and squatter settlements in Pakistan.

"Today, the research does not show that they provide a benefit above and beyond plain soap," says Allison Aiello, assistant professor of epidemiology at the US-based University of Michigan School of Public Health. She notes, however, that triclosan may have some efficacy at higher concentrations, for use in environments where people are elderly or sick, for example.

In defense, Ciba points to research conducted by Dial, a subsidiary of German detergents, toiletries and adhesives producer Henkel. This research, published last year in the Journal of Food Protection, found that there is a greater potential to reduce the transmission and acquisition of disease using soap containing triclosan than plain soap.

Dial's method involved contaminating participants' hands with E. coli and then washing with Dial Complete liquid soap or plain liquid soap. The participants then handled melon balls and the quantity of bacteria transferred from the washed hands to the melon balls was measured. The Dial soap was up to 30 times more effective in reducing the bacterial transfer from the hands to the melon balls, the researchers say.

ENVIRONMENTAL RISKS

Various research projects suggest environmental and health risks associated with the cumulative effects of antibacterial agents.

In the UK, retailer Marks & Spencer promised to remove all products containing triclosan from its shelves in 2005, after scientists at the US's Virginia Tech university found that chlorine added to tap water reacted with triclosan to produce chloroform. Marks & Spencer says it is still "a triclosan-free company."

The Virginia Tech study suggests that the use of antimicrobial soaps and other ­products may expose people to significant quantities of chloroform, which is ­classified as a probable human carcinogen. The study was published in American Chemical Society journal Environmental Science & Technology.

Ciba does not dispute the formation of chloroform in the study, but says the soaps were tested with highly chlorinated water. Also, under the exaggerated conditions, researchers were able to measure chloroform released from both triclosan-free products as well as products containing triclosan, it says.

"The problem is that this reaction occurs with any organic compound in the water once the water is chlorinated," says Nussbaum. "Therefore, the problem is not that triclosan is used. The problem is the high concentration of chlorine in the water."

The Swiss group has identified what it says are flaws in further research into the formation of chloroform through the chlorination of triclosan-containing antibacterial products, published last year in Environmental Science & Technology. The research paper contains miscalculations and resultant incorrect and damaging conclusions, Ciba said in a letter to the journal's editor.

Ciba also refutes claims that the product can cause endocrine disruption in bullfrog tadpoles. Research commissioned by Ciba and conducted by Fort Environmental Laboratories in the US suggests that triclosan does not alter the normal course of thyroid-mediated metamorphosis in bullfrog tadpoles at environmentally relevant concentrations. The study was presented last month at the Society of Environmental Toxicology and Chemistry (SETAC) meeting in Warsaw.

Ciba commissioned the study after scientists from the University of Victoria and the Pacific Environmental Science Centre, both in Canada, found that exposing bullfrog tadpoles to levels of triclosan commonly found in the environment can cause endocrine disruption. Their results were published in the journal Aquatic Toxicology in 2006.

Nussbaum argues that the conditions under which the Canadian research was conducted were exaggerated, and therefore not representative. The key problem with the Canadian research, he says, was that instead of using a naturally metamorphosed tadpole, the scientists induced pre-metamorphic tadpoles by injecting them with the thyroid hormone triiodothyronine. "Just by adding triclosan to the environment, they could not see anything," he claims.

The Canadian study caused a lot of concern about the use of triclosan, says Nussbaum. "Now we have enough data to support the molecule," he adds.

Another concern is that overuse of antibacterial soaps could lead to antibiotic resistance. Until now, this has only been seen in the laboratory, and not in the community setting. But Aiello says more research is needed. "There have only been a handful of studies," she says. "We definitely need further research on this to answer the question of antibiotic resistance."

SUBURBAN MYTH

Brian Sansoni, vice president of the Soap and Detergent Association (SDA) with responsibility for communication and membership, says it is a "suburban myth" that antibacterial soaps are contributing to antibiotic resistance. Such discussions are diverting attention from the real problem, the overuse of antibiotic drugs, he argues. Comparing the overuse of antibiotics with the use of antibacterial soaps "is like comparing Mount Everest to a molehill," he adds.

As the scientific community continues to research the benefits and risks of antibacterial soaps, some firms are developing low-toxicity alternatives. US-based personal care and cosmetics company Elevance Renewable Sciences says it is using olefin metathesis to develop antimicrobials, which combine a broad effectiveness with low toxicity.

"The conundrum of antibacterial agents is that we want them to eliminate or prevent the growth of the bad bugs, but be completely safe for humans and the good bacteria that humans host," says K'Lynne Johnson, Elevance's CEO. "We also don't want them to interfere in the environment."

Elevance expects the biocides components of the personal care market to rise by 3-7%/year over the next three to five years, driven by factors including growth in the global population and the rise of the middle class. The company expects increasing awareness of environmental concerns associated with the cumulative effects of antibacterial agents, such as triclosan, to stimulate demand for low-toxicity antibacterial agents.

The SDA maintains that criticism of antibacterial agents, such as triclosan, is unfair. "The overwhelming evidence has shown that these products are safe and effective," Sansoni says. "But the most important thing is for people to wash with soap and water, no matter what kind of soap it is - antibacterial, non-antibacterial, powder, liquid or gel."

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