Collaborative Research: Parabens as a Tool for Interrogating Halogenation in Environmental Systems: Products and Pathways

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This project, funded by the Environmental Chemical Sciences Program within the Division of Chemistry, supports Professors Daniel McCurry of the University of Southern California (USC) and John Sivey and Keith Reber of Towson University (TU) to study chemical reactions related to water disinfection. When water is disinfected with chlorine, halogenation reactions occur. Such reactions can decrease levels of harmful chemical pollutants in water. Halogenation reactions can also generate toxic chlorinated byproduct from natural or man-made precursors in water. This project seeks to understand the rates and mechanisms of these reactions. The focus is on parabens, which are used as preservatives in shampoos, lotions, and other consumer products. Parabens can be washed down the drains of showers and sinks as components of greywater. When greywater is recycled, parabens can enter drinking water. Parabens resemble molecules that are naturally present in lakes and rivers due to the breakdown of plant matter. Therefore, studying how parabens respond to the chlorination process associated with drinking water treatment can lead to insights into chlorination reactions with other molecules. The research is conducted as a collaboration between a large research university (USC) and a primarily undergraduate institution (TU). The project also includes a teaching internship for a USC graduate student at TU, and a summer research internship for a TU undergraduate at USC.The team studies fundamental aspects of aqueous halogenation important for understanding the fate of parabens and other aromatic nucleophiles. Specific questions addressed by this project include: (1) What is the role of trace, highly reactive, often-overlooked halogenating species (such as Cl2O and BrCl) in the halogenation of parabens? (2) During chloramination, when ammonia-containing water is chlorinated, what is the role of individual chloramine species? Is monochloramine, which dominates chloramine speciation, essentially inert? (3) What fraction of active halogen consumption results in halogenation versus oxidation and formation of inert inorganic halide species? (4) What is the mechanism of haloform formation from substituted phenols (including parabens)? The research tasks address both fundamental environmental chemistry questions and applied concerns about the fate of parabens, particularly during potable water reuse.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.