Aquatic Environmental Microbiology and Chemistry

University of Wisconsin Milwaukee, Zilber School of Public Health    



Degradation of phenyl urea pesticides

The environmental fate and toxicity of chemical pollutants is complicated by the large number of potential biological transformations that a chemical may undergo once released into the environment.  In some cases the breakdown products may be more harmful than the parent compounds. This appears to be the case for phenyl urea herbicides such as Linuron, Diuron, Triclocarban and related compounds. Phenyl urea herbicides are chlorinated aromatic compounds added to a wide variety of products used by both industry and society at large. The most common of these are antimicrobial soaps and detergents containing Triclocarban (e.g. hand sanitizers, toothpastes etc). Triclocarban contains two chlorinated phenyl rings linked by a urea bridge. Diuron and Linuron are used as herbicides or pesticides and contain a single chlorinated phenyl ring with a substituted urea moiety. These compounds are high production volume chemicals produced at a rate of > 1 million pounds per year and they are widely distributed in the environment due to their low biodegradability. All of these compounds have estimated half- lives exceeding 100 days in freshwater and have the potential to bioaccumulate in freshwater organisms (Ahtiainen et al. 2003, EPA 2002, Guzella et al. 2006).

Proposed pathway for the bacterial degradation of Triclocarban and related phenyl urea herbicides. Triclocarban is hydrolyzed at the urea bridge resulting in chloroanilines which are degraded by deamination and hydroxylation producing chlorocatechols. Ortho- or meta cleavage pathways oxidize chlorocatechols to 3-chloro-cis,cis-muconate or 5-chloro-2-hydroxymuconic acid semialdehyde, respectively. These products are then degraded by intermediary metabolic pathways resulting in carbon and nitrogen assimilation.

Our research and that of others shows that some wastewater bacteria are able to transform triclocarban to mono- and dichloroanilines; which is also the case for similar phenyl urea pesticides (Di Corcia et al. 1999, Gledhill et al. 1975, Miller et al. 2010). The fate of chloroanilines metabolites is not certain, but they may undergo slow degradation, bioaccumulate or attach to particles. Even if they are degraded, a steady supply of millions of pounds of phenyl urea herbicides to the environment each year precludes biodegradation as a means to prevent human exposure. This is important since chloroanilines have been named probable carcinogens by the U.S. Environmental Protection Agency due to their association with bladder cancer. Are phenyl urea herbicides a source of chloroanilines in the aquatic environment and are humans exposed to these compounds in contaminated groundwater and other drinking water resources?   Our research aims to answer this question.


Ahtiainen, J., M. Aalto, and P. Pessala. 2003. Biodegradation of chemicals in a standardized test and in environmental conditions. Chemosphere 51:529-537.

Di Corcia, A., A. Costantino, C. Crescenzi, and R. Samperi. 1999. Quantification of phenylurea herbicides and their free and humic acid-associated metabolites in natural waters. J. Chromatogr. A 852:465-474.

Environmental Protection Agency, U. S. 2002. TCC Consortium. High production volume (HPV) chemical challenge program data availability and screening level assessment for triclocarban, CAS#: 101-20-2. EPA.

Gledhill, W. E. 1975. Biodegradation of 3,4,4'-Trichlorocarbanilide, TCC, in sewage and activated-sludge. Water Res. 9:649-654.

Guzzella, L., E. Capri, A. Di Corcia, A. Barra Caracciolo, and G. Giuliano. 2006. Fate of diuron and linuron in a field lysimeter experiment. J. Environ. Qual. 35:312-23.

Miller, T. R., D. R. Colquhoun, and R. U. Halden. 2010. Identification of wastewater bacteria involved in the degradation of Triclocarban and its non-chlorinated congener. Submitted to FEMS Microbiology Ecology.

User login