Recent work from the PI's laboratories suggests that concomitant with the decrease of combustion-derived dioxins, there may be an increase in dioxins derived from surprising non-combustion sources: transformations of the antimicrobial triclosan (and its chlorinated derivatives) and hydroxylated polybrominated diphenyl ethers (OH-PBDEs). OH-PBDEs are degradation products of polybrominated diphenyl ether (PBDE) flame retardants, but also arise from natural sources in marine systems. This work will continue their study of the environmental chemistry of triclosan and hydroxylated polybrominated diphenylethers (OH-PBDEs), with the ultimate goal of assessing the environmental significance of the dioxins formed from these compounds. The objective of this proposal is to determine the importance of anthropogenic and natural halohydroxydiphenyl ethers as sources of halogenated dibenzo-p-dioxins using a combination of laboratory experiments and field measurements.
This study will be the first to combine laboratory photolysis experiments, wastewater analyses, and sediment analyses to develop and use a set of chemical markers that will reveal whether OH-PBDEs, and the PBDDs formed via OH-PBDE photolysis, arise from natural or anthropogenic sources in both freshwater and estuarine/marine environments. Laboratory experiments and analysis of wastewater samples will reveal appropriate OH-PBDE and PBDD markers for anthropogenic sources. The studies on triclosan and triclosan-derived dioxin levels and trends will provide another set of anthropogenic markers to which OH-PBDEs and their associated PBDDs will be compared in sediments and sediment cores. The knowledge gained from this research will allow assessment of sources and prediction of concentrations of PBDDs and PCDDs that are derived from halohydroxydiphenyl ethers present in wastewater. The importance of natural and anthropogenic sources will also be determined, for they will identify the "chemical fingerprints" associated with these origins of the targeted compounds. This information is critical if regulation of halohydroxydiphenyl ethers or additional wastewater treatment is deemed necessary. Only with this proposed combination of laboratory and field measurements can it be verified that wastewater treatment facilities serve as a pseudo-continuous source of halogenated dioxins to surface waters via the release and subsequent photolysis of triclosan and OH-PBDEs. Thus, the proposed research will advance our understanding of the threats posed by wastewater derived micro-contaminants. This knowledge is especially important for the targeted chemicals, for both the parent compounds and expected daughter products are known to bioaccumulate, persist in sediments, and have adverse biological effects.
The broad societal benefits of this work will be to provide a complete assessment of the potential threat to aquatic ecosystems posed by halohydroxydiphenyl ethers and the dioxins produced via their photolysis and to determine the role of natural and anthropogenic sources of these compounds. They will broaden participation of underrepresented groups in science and engineering by participating in the University of Minnesota Institute of Technology Exploring Careers program, a one-week non-residential summer program for 9th-11th grade girls and students from underrepresented groups and by supporting undergraduate researchers from a local women?s undergraduate institution (St. Benedict?s College). They will establish research infrastructure and an international partnership through the collaborative, interdisciplinary and multi-institutional nature of the project. Lastly, they will broadly disseminate the results of the proposed research via an interactive activity at the Science Museum of Minnesota, outreach activities of the San Francisco Estuary Institute, and via publications and conference presentations.
