Organophosphate esters (OPEs) are commonly used as additives in foams, paints, and other industrial applications where plasticizers or flame-retardants are required. These mostly water soluble compounds have been detected in wastewaters, surface waters, and drinking waters across Europe and North America. The aqueous OH-oxidation rate, k_OH, was empirically determined for four organophosphate esters according to a previously developed UV-H₂O₂-competition-kinetics method, utilizing a bench-scale UV apparatus containing low-pressure-Hg lamps, and nitrobenzene as the reference compound. The efficiency of dehalogenation, with respect to oxidation of a chlorinated OPE in lab-grade water, was assessed for OH formed from UV-H₂O₂ and UV-HOCl. The significance of the observed rates of OPE oxidation and subsequent dehalogenation are discussed. Includes 12 references, figures.