Parabens (i.e., para-hydroxybenzoate esters) are ubiquitous organic contaminants used as antimicrobial preservative agents in personal care products such as lotions, detergents, and cosmetics. Parabens enter public water supplies through wastewater and have been detected in grey water, surface water, and human tissue. Mono- and di-halogenated parabens can form in the presence of electrophilic chlorine and bromine species endemic to disinfection processes, and have been presumed to be the stable, final product of paraben transformation in engineered waters. However, recently studied pathways propose a mechanism for the generation of trihalomethanes (THMs) from phenolic compounds (a significant reactive portion of natural organic matter) to which the majority of THM formation in natural waters has been attributed via electrophilic aromatic substitution and hydrolysis. In this work, the rates of parent compound loss and halogenated product formation were quantified by monitoring ethylparaben and its mono- and di-chlorinated and brominated products under simulated disinfection conditions with free chlorine or bromine. Solution conditions including pH, chloride concentration, and bromide concentration were varied to determine the extent of chloride catalysis in chlorination and bromination and to identify key free halogen species (including Cl2, Cl2O, BrCl, Br2, and BrOCl) responsible for ethylparaben transformation. Possible effects from bromide impurities in reagents on product distributions in free chlorine systems were also investigated. In addition, proposed structures of paraben transformation products were characterized.

Halogenation of para-hydroxybenzoate esters (parabens) in chlorinated and brominated waters under simulated drinking water disinfection conditions

ACS Fall 2021

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