Daily News Archives
From April 19, 2005
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.
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
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.