Abstract
The environmental risks and health impacts associated with particulate organophosphate flame retardants (OPFRs), which are ubiquitous in the global atmosphere, have not been adequately assessed due to the lack of data on the reaction kinetics, products, and toxicity associated with their atmospheric transformations. Here, the importance of such transformations for OPFRs are explored by investigating the reaction kinetics, degradation chemical mechanisms, and toxicological evolution of two OPFRs (2-ethylhexyl diphenyl phosphate (EHDP) and diphenyl phosphate (DPhP)) coated on (NH4)2SO4 particles upon heterogeneous OH oxidation. The derived reaction rate constants for the heterogeneous loss of EHDP and DPhP are (1.12 ± 0.22) × 10-12 and (2.33 ± 0.14) × 10-12 cm3 molecules-1 s-1, respectively. Using recently developed real-time particle chemical composition measurements, particulate products from heterogeneous photooxidation and the associated degradation mechanisms for particulate OPFRs are reported for the first time. Subsequent cytotoxicity analysis of the unreacted and oxidized OPFR particles indicated that the overall particle cytotoxicity was reduced by up to 94% with heterogeneous photooxidation, likely due to a significantly lower cytotoxicity associated with the oxidized OPFR products relative to the parent OPFRs. The present work not only provides guidance for future field sampling for the detection of transformation products of OPFRs, but also strongly supports the ongoing risk assessment of these emerging chemicals and most critically, their products.
Highlights
Organophosphate flame retardants (OPFRs) are synthetic chemicals frequently utilized as plasticizers, additives, and antifoaming agents in building materials, electronics, and household products.[1,2]
Such risks are usually associated with OPFR emissions, with minimal consideration for those associated with the potential secondary atmospheric chemistry
The rate constant of heterogeneous oxidation is quantified by measuring the loss of the particulate OPFR, as estimated by a selected marker ion from the HR-TOF-AMS spectrum.[33]
Summary
Organophosphate flame retardants (OPFRs) are synthetic chemicals frequently utilized as plasticizers, additives, and antifoaming agents in building materials, electronics, and household products.[1,2] The estimated global market volume of OPFRs is 620 kilotons in 2013 and is expected to increase into the foreseeable future.[3]. The heterogeneous reactions between OH radicals and OPFRs (EHDP and DPhP) coated onto (NH4)2SO4 particles (denoted OPFR@AS) were studied using a photochemical oxidation flow tube reactor described previously[33] and in the Supporting
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