Toxicity Evaluation Of Tri-(1,3-dichloroisopropyl) Phosphate And The Degradation Mechanism By UV-activated Persulfate

Organophosphate flame retardants were frequently detected in different environment and even in organism,and it has been raising concern as a class of emerging organic contaminants?EOCs?due to persistence,bioaccumulation and bio-toxicity.Chlorinated OPFRs is an important part of organophosphorus flame retardants among them.Due to the difference of-Cl substitution position,its toxicity and ecological risk may also be different.Currently,only limited researches regarding potential human health risk evaluation by chlorinated OPFRs,and the researches on the degradation of chlorinated OPFRs was limited for the lack of efficient methods.In this study,tris?1,3-dichloro-2-propyl?phosphate?TDCPP?,tris?2-choroethyl?phosphate?TCEP?and tris-?2-chloroisopropyl?phosphate?TCPP?were selected as the target contaminants and Caco-2 cell was used as the common model cell lines.The aim of this work were to evaluate the cytotoxicity and toxicity effects of these three OPFRs,in addition,compared with TCEP and TCPP,TDCPP with relative high toxicity was further studied to assess the effect on human intestinal microflora in vitro simulation.In addition,the degradation mechanism of ultraviolet activated persulfate?UV/PS?technology on TDCPP and the conversion mechanism of intermediate products were explored.The major results in our study were as follows:Different inhibitory effects on viability of Caco-2 cell were induced by TDCPP,TCEP and TCPP in dose-dependent manner,moreover,TDCPP exhibited the powerful inhibition.High dosage chlorinated OPFRs significantly induced the increase of the reactive oxygen species?ROS?,decreasing the mitochondrial membrane potential?MMP?to cause the MMP dysfunction,elevating the intracellular free Ca²⁺levels and accelerating the progress of cell death.The relative abundance and consortium structure of human intestinal microflora were obviously changed under TDCPP stress.The relative abundance of Proteobacteriaincreased continuously with the improve of TDCPP concentration,while Firmicutesrelative abundance decreased gradually.Enterococcus,Lactobacillus and Escherichiawere the core genera inhuman intestinal microflora and their relative abundance were altered after TDCPP was added.The functional prediction results further revealed that the overexpression of glutathione S-transferase,lactose permease and multidrug resistance protein indicated a protective strategy for human intestinal microflora to counter the TDCPP stress.The results showed that the degradation reaction of TDCPP followed a pseudo-first order kinetics model with an optimal rate constant(k_obs)at 0.1222 min^-1.The TDCPP degradation efficiency reached to 97.9%after 30 minutes photocatalytic reaction by using 50 mg/L PS at the initial p H 7.0.The removal of TDCPP was inhibited by anions(HA?CO₃^2-?HCO₃^-?NO₃^-?Cl^-)in the solution,and the inhibitory effect was HA>CO₃^2->HCO₃^->NO₃^->Cl^-,however the degradation of TDCPP by UV/PS is basically not affected by SO₄^2-.Radical scavenging assay revealed that·SO₄^-was the predominant reactive oxygen species for TDCPP degradation.Moreover,two stable degradation intermediates were firstly detected using Liquid phase tandem high resolution mass spectrometry?LC-QTOF-MS?.The results in current study revealed the cytotoxicity of TDCPP,TCEP TCPP and the toxicity mechanism.The effect of human intestinal microflora by TDCPP with relative high toxicity and the functional genes were deeply revealed.Additionally,the reaction mechanisms of TDCPP using UV/PSwas clarified.This study could provided reliable datum for evaluation of threaten caused by TDCPP and efficient elimination of TDCPP from environment.