A comprehensive and quantitative comparison of organophosphate esters: Characteristics, applications, environmental occurrence, toxicity, and health risks

Organophosphate esters (OPEs) are substitutes for bromine flame retardants and are used in various consumer products. While OPEs have been extensively studied, the lack of systematic comparison among major OPEs contributes to ambiguity regarding their risks. Classified by substituents of Cl-OPEs, alkyl-OPEs, and aryl-OPEs, this review conducted a retrospective comparison and comprehensive analysis of physicochemical properties, use and regulation, environmental occurrence proportion, toxic effect thresholds, and degree of health risk, thus identifying typical high-risk OEPs that warrant greater scrutiny. Generally, Cl-OPEs and alkyl-OPEs exhibit higher concentration proportion than aryl-OPEs in various environmental media. Moreover, the toxic effects of Cl-OPEs and aryl-OPEs surpass those of alkyl-OPEs, notably tris(2-chloro-1(chloromethyl)ethyl) phosphate (TDCPP) and triphenyl phosphate (TPHP), alongside TDCPP, TPHP, tris(2-chloroisopropyl) phosphate (TCPP), tris(2-choroethyl) phosphate (TCEP), tris(2-butoxyethyl) phosphate (TBOEP), and tributyl phosphate (TNBP) as the most typical OPEs. Although OPEs at environment concentrations pose limited threats to human health, further assessment of the health risks posed by typical high-risk OPEs in sensitive populations is remain necessary. Overall, this review offers a more comprehensive perspective on the differences between typical OPEs and provides valuable insights into their future use and regulation.