January 24, 2005 — Many rivers and streams in
the United States are believed to contain a toxic antimicrobial
chemical whose environmental fate was never thoroughly scrutinized
despite large-scale production and usage for almost half a century,
according to an analysis conducted by researchers at the Johns Hopkins
Bloomberg School of Public Health. The chemical, triclocarban, has been
widely used for decades in hand soaps and other cleaning products, but
rarely was monitored for or detected in the environment. The new
findings suggest that triclocarban contamination is greatly
underreported. The study is published in the current online edition of
Environmental Science & Technology, a peer-reviewed journal of the
American Chemical Society.
“We’ve been using triclocarban for almost half a century at rates
approaching 1 million pounds per year, but we have essentially no idea
of what exactly happens to the compound after we flush it down the
drain,” said the study’s lead author, Rolf U. Halden, PhD, PE,
assistant professor in the School’s Department of Environmental Health
Sciences and founding member of its Center for Water and Health.
The nationwide assessment of triclocarban contamination is based in
part on an analysis of water samples collected from rivers in and
around Baltimore, Md., as well as from local water filtration and
wastewater treatment plants. From the samples, Dr. Halden and his
summer research intern, Daniel H. Paull, now a graduate student in the
Chemistry department at Johns Hopkins University, observed the
occurrence of triclocarban in the environment correlated strongly with
that of triclosan, another commonly used antimicrobial chemical that
has been studied in much greater detail because it is more easily
detectable. Using an empirical model and published data on the
environmental occurrence of triclosan, the researchers predicted
triclocarban concentrations for 85 U.S. streams. The study results
suggest that the antimicrobial contaminant is present in 60 percent of
the U.S. water resources investigated, thereby making it the fifth most
frequent contaminant among 96 pharmaceuticals, personal care products
and organic wastewater contaminants evaluated.
To determine the validity of the analysis, the researchers compared
their predicted nationwide levels of contamination to experimentally
measured concentrations in the Greater Baltimore region, and found no
statistically significant differences. The results also show that the
levels of triclocarban in water resources nationwide are much higher
than previously thought.
In surface water from the Baltimore region, the researchers detected
triclocarban at concentrations of up to 6.75 micrograms per liter
(parts-per-billion). This maximum concentration was 28-fold higher than
previously reported levels, which are currently used by the U.S.
Environmental Protection Agency for evaluation of the ecological and
human health risks of triclocarban.
“Along with its chemical cousin triclosan, the antimicrobial
compound triclocarban should be added to the list of polychlorinated
organic compounds that deserve our attention due to unfavorable
environmental characteristics, which include long-term persistence and
potential bioaccumulation. Triclocarban, for example, has an estimated
half-life of 1.5 years in aquatic sediments. Do the potential benefits
of antimicrobial products outweigh their known environmental and human
health risks? This is a scientifically complex question consumers,
knowingly or unknowingly, answer to everyday in the checkout line of
the grocery store,” said Dr. Halden.
“Co-Occurrence of Triclocarban and Triclosan in U.S. Water Resources” was written by Rolf U. Halden and Daniel H. Paull.
The research was supported by the National Institute for
Environmental Health Sciences through the Johns Hopkins Center in Urban
and Environmental Health, the Maryland Cigarette Restitution Program
Research Grant, the Johns Hopkins Bloomberg School of Public Health
Faculty Innovation Award and the Johns Hopkins Center for a Livable