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From April 19, 2005

Antibacterial Agent Reacts With Tap Water to Form Carcinogen
(Beyond Pesticides, April 19, 2005)
Researchers at Virginia Tech have found that the chemical triclosan, the active ingredient in many antimicrobial soaps, reacts with chlorine in tap water to form significant quantities of chloroform. Chloroform is classified by the Environmental Protection Agency (EPA) as a probable human carcinogen. The research also suggests that the reaction of triclosan with chlorine could produce highly chlorinated, and thus dangerous, dioxins in the presence of sunlight.

The study, "Formation of Chloroform and Chlorinated Organics by Free-Chlorine-Mediated Oxidation of triclosan," was published in the beginning of April in Environmental Science and Technology's (ES&T) online journal. Peter Vikesland, PhD, and colleagues at the Virginia Polytechnic Institute and State University looked specifically at triclosan in dishwashing liquid. When the researchers simulated home dishwashing conditions, they found that triclosan reacts with free chlorine in tap water to generate levels of chloroform in dishwater as high or higher than EPA's maximum allowable amount, reports ES&T Science News. In addition to being a possible carcinogen, chloroform has been linked with human bladder cancers and miscarriages.

Previous studies have shown that sunlight readily converts triclosan in river water to produce dioxins. This new research builds on that by showing that triclosan's reaction with free chlorine produces a number of chlorinated triclosan intermediates, including 2,4 dichlorophenol, which could photochemically (with sunlight) generate more highly chlorinated dioxins, which are far more toxic. Dioxins are a class of chemicals that in small doses are highly carcinogenic act as endocrine disruptors.

It is unlikely that such dioxins would be generated during dishwashing even near a window on a sunny day, because the glass would screen out most of the UV light necessary to produce the dioxin. But, researchers suggest that dioxins could be forming near swimming pools in some situations. "There's triclosan in hand soaps and moisturizers. [If] someone who has triclosan-containing moisturizer [on jumps] into the pool … they're a potential source for chloroform [and chlorinated dioxin] formation," Dr. Vikesland said. David Sedlak, PhD, a professor in the civil and environmental engineering department at the University of California, said of the scenario, "You could produce a dioxin on the surface of your skin [that] gets absorbed through the skin."

Triclosan is found in hundreds of common everyday products, including nearly half of all commercial soaps. In addition to soaps, triclosan is found in deodorants, toothpastes, cosmetics, fabrics and plastics. It is used so frequently that triclosan has made its way into the human body; a Swedish study (Daily News, 12/12/01) found triclosan in human breast milk in three out of five women. Considering the ubiquitous nature of triclosan in toiletry products used directly on the skin (and mouth, in the case of toothpastes), this recent study demonstrates the need for more research on this chemical. "There are numerous potential exposure pathways that can be envisioned, such as inhalation and skin exposure, when using antimicrobial soaps to wash dishes or when taking a shower. There is also risk of exposure when using triclosan laden moisturizers as they may also react with chlorine in the water," said Dr. Vikesland to Newswise.

Besides formation of dioxins and chloroform, there are other health and environmental risks associated with triclosan. There is good evidence that with the continued widespread use of triclosan, antibiotic resistance will become increasingly problematic. Numerous studies have found that triclosan promotes the emergence of bacteria that are resistant to antibiotics. It is one of the most frequently detected compounds in rivers, streams, and other bodies of water, often in high concentrations, and has been shown to be highly toxic to algae.

For more information on triclosan, read our ChemWatch factsheet and follow-up article.

TAKE ACTION: When used in hospitals and other health care settings, or for persons with weakened immune systems, triclosan represents an important health care and sanitary tool. Outside of these settings, it is totally unnecessary, and the constant exposure to triclosan becomes a health and environmental hazard. The best solution to preventing infections is good old soap and water. Make sure you read all labels when buying soaps and other toiletry products to ensure that triclosan is not included. Also be on the lookout for Microban and Irgasan, which are other names for triclosan. Consult our triclosan factsheet for a list of products containing triclosan (some, like Teva sandals and kitchen knives, may surprise you) and for more detailed information on alternatives to triclosan.