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Antibacterial Products Containing Triclosan Produce Chloroform Under Common Conditions, A New Study Finds.

No longer just for hand soap, the antibacterial agent triclosan is cropping up in an ever-expanding range of consumer products. These days, even socks and toothpaste aim to keep parts of you microbe-free. But research published today on ES&T’s Research ASAP website (DOI: 10.1021/es062227l) by Peter Vikesland and colleagues at the Virginia Polytechnic Institute and State University shows that under normal household conditions, products containing triclosan react with chlorinated water to produce chloroform, a probable carcinogen.

In 2005, a bit of panic ensued after ES&T published Vikesland’s research along with a news story. The study showed that in the laboratory, pure triclosan reacts with free chlorine to produce chloroform. London’s Evening Standard newspaper ran a story reporting that the British chain Marks & Spencer planned to remove all triclosan-containing products from its shelves. Other news stories followed, and soon Vikesland learned that stores in China were removing triclosan-containing toothpaste from their shelves. In response, Vikesland warned that people should not jump to conclusions and pointed out that his work did not examine toothpaste.

The team has now followed up on that study and tested 16 products, including lotions, soaps, and body washes with and without triclosan. They found that all of the household goods with triclosan produced either chloroform or other chlorinated byproducts. From their tests, they estimate that under some conditions the use of triclosan can increase a person’s annual exposure to chloroform by as much as 40% above background levels in tap water.

In some soaps, all of the triclosan degraded within 1 minute of exposure to chlorinated water at 40 °C, a temperature that might be used for household cleaning. Experiments with tap water from different locations yielded mixed results: little chloroform was generated in Atlanta water, but moderate levels formed in Danville, Va., water for some soaps.

“At fairly low levels of chlorine, the triclosan degrades rapidly,” Vikesland says. That speed leads him to ask whether triclosan is broken down quickly enough in chlorinated tap water to render it less effective in killing germs.

“I don’t find the formation of chloroform surprising; I think it will form under many scenarios in our daily lives,” says Shane Snyder, research and development project manager for the Southern Nevada Water Authority. After the City of Palo Alto, Calif., banned triclosan-containing soaps from city facilities, Snyder says he was contacted about enacting a similar ban in the Las Vegas area, but he saw no reason to do so from a wastewater-treatment perspective. Chlorine reacts with various forms of organic matter in municipal water to produce chloroform, he says, and he expects the levels of chloroform from triclosan to be negligible.

Triclosan creates enough chloroform to warrant more study, believes Vikesland, but he maintains that “it’s hard to predict exactly what’s going to happen at an individual’s tap.” Both water temperature and the level of chlorine in local tap water will have significant effects on chloroform production, as will the antimicrobial product used. Two products tested that contained bisulfide and ammonium maintained triclosan levels longer; Vikesland attributes this to the ability of those compounds to scavenge chlorine.

Three scientists, two of whom work for a company that uses triclosan in its products, told ES&T that in their opinion the results of the new study should not be interpreted too broadly; they chose not to be quoted. Two pointed out that the conditions used in the study, although more realistic than those in previous work, do not necessarily reflect the exposure most consumers would get from using antibacterial soaps. The researchers allowed reactions to proceed for 1 minute, but commonly used consumer guidelines call for washing hands for only about 15 seconds.

“I think even though the actual washing conditions may vary among individuals, the findings of this study are still credible and very relevant because of the conservative approach it took,” says Ching-Hua Huang of the Georgia Institute of Technology. She points out that the study used a “modest amount” of soap (0.25 grams per liter of water) and found large differences between chloroform concentrations with triclosan-containing (averaging 60 micrograms per liter [µg/L]) and triclosan-free (2 µg/L) soaps.

Ciba Specialty Chemicals invented triclosan 35 years ago, according to the company’s website. Ciba does not dispute the formation of chloroform in the study but does question whether the researchers used real-world conditions, says company spokesperson Pat Rossman. Ciba points out that some chloroform formed with triclosan-free soaps and that the tap-water studies show decomposition levels much lower than those obtained under lab conditions. The company will review the findings, Rossman says, and conduct further evaluations of the chloroform issue.

Vikesland writes in the paper that “a full risk–benefit analysis of these products should be conducted.” Although he does not advocate that people stop using antibacterial products, he says it would be best for consumers to make purchasing decisions “while considering the potential reactions that can occur.” —ERIKA ENGELHAUPT

Copyright © 2007 American Chemical Society

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