Presence of organophosphate flame retardants(OPEs)in different functional areas in residential homes in Beijing,China

The production and application of organophosphate esters(OPEs)have dramatically increased in recent years due to their use as a replacement for brominated flame retardants.In this study,13 OPEs(∑_(13)OPEs)were analyzed in indoor air samples from kitchens and living rooms in 14 residential homes in Beijing,China.The concentrations of ∑_(13)OPEs in kitchen air samples(mean:13 ng/m^(3))were significantly(p<0.05)higher than in living room air samples(5.0 ng/m^(3)).In addition,paired window surface organic film samples were collected and analyzed to investigate film-air partitioning,exhibiting a mean concentration of ∑_(13)OPEs of 4100 ng/m^(2).The congener profiles showed that tris(2-chloroisopropyl)phosphate(TCPP)was the predominant compound in both window film samples(48%)and the corresponding indoor air sample(56%).The estimated daily intakes(EDI)of OPEs via indoor air inhalation were 2.8 and 1.4 ng/kg/day for infants and adults,respectively,both of which are below the reference dose values(RfDs).Overall,these findings indicate that OPEs in the indoor air environment of residential homes in Beijing are not likely to pose a health risk to the general population.

Sorption of aromatic organophosphate flame thermally and hydrothermally produced retardants on biochars

Aromatic organophosphate flame retardant(OPFR)pollutants and biochars are commonly present and continually released into soils due to their increasingly wide applications.In this study,for the first time,the sorption of OPFRs on biochars was investigated.Although triphenyl phosphate(TPhP)and triphenylphosphine oxide(TPPO)have similar molecular structures and sizes,TPhP exhibited much faster and higher sorption than TPPO due to its stronger hydrophobicity,suggesting the dominant role of hydrophobic interactions in TPhP sorption.Theπ-πelectron donor-acceptor(EDA)interactions also contributed to the sorption process,as suggested by the negative correlation between the sorption capacity of the aromatic OPFRs and the aromatic index(H/C atomic ratios)of biochar.Density functional theory calculations further showed that one benzene ring of aromatic OPFRs has no electrons,which may interact with biochar viaπ-πEDA interactions.The electrostatic attraction between the protonated P=O in OPFRs and the negatively charged biochar was found to occur at pH below 7.This work provides insights into the sorption behaviors and mechanisms of aromatic OPFRs by biochars.

Effects of long-term exposure to TDCPP in zebrafish( Danio rerio )–Alternations of hormone balance and gene transcriptions along hypothalamus-pituitary axes

Background : TDCPP is one of the major chemical of organophosphate flame retardants(OPFRs) that has been detected ubiquitously in both the environment and biota. Previously we observed that it influenced the concentrations of sex and thyroid hormones in a sex-dependent pattern, leading to reproductive impairments after short-term exposure in zebrafish. Here we investigate the consequences of longerterm exposure to TDCPP on the hypothalamic-pituitary-gonad(HPG), hypothalamicpituitary-i nterrenal(HPI), and hypothalamic-pituitary-thyroid(HPT) axes of zebrafish( Danio rerio).Methods : A 120-day exposure test to 0.005, 0.05 and 0.5 mg/L TDCPP was initiated with fertilized eggs. Sex steroid hormones in the treated fishes were measured and transcriptional changes were analyzed.Results : In female fish, exposure to TDCPP resulted in increases in plasma cortisol,follicle stimulating hormone(FSH), luteinizing hormone(LH), 17β-estradiol(E2), cortisol, thyroxine(T4), and triiodothyronine(T3). Transcription of most target genes along HPG, HPI and HPT axes were increased by the exposure. While in male fish the exposure led to decreases in cortisol, FSH, LH, T4, T3, testosterone(T), and 11-ketotestosterone(11-KT). Transcription of genes along HPG, HPI and HPT axes,especially steroidogenic genes, were inhibited in male zebrafish. While, E2/T or E2/11-KT ratio was increased in both female and females. The sex-dependent changes in hormones might be due to differential responses to TDCPP induced stresses. An increase in cortisol level coincided with increases in E2 and THs in female fish, while in males decreases in cortisol as well as T, 11-KT and THs were observed. Long-term exposure to TDCPP at very low(μg/L) concentrations could disrupt hormone balances in a sex dependent way.Conclusion : This study revealed that TDCPP could affect endocrine axes – HPG, HPI and HPT – in zebrafish, and impair zebrafish development.

Biodegradation pathway and mechanism of tri (2-chloropropyl) phosphate by Providencia rettgeri

Tri(2-chloropropyl)phosphate(TCPP)was an emerging contaminant of global concern because of its frequent occurrence,potential toxic effects,and persistence in the environment.Microbial degradation might be an efficient and safe removal method,but limited information was available.In this study,Providencia rettgeri was isolated from contaminated sediment and showed it could use TCPP as unique phosphorus source to promote growth,and decompose 34.7%of TCPP(1 mg/L)within 5 days.The microbial inoculation and the initial concentration of TCPP could affect the biodegradation efficient.Further study results indicated that TCPP decomposition by Providencia rettgeri was mainly via phosphoester bond hydrolysis,evidenced by the production of bis(2-chloropropyl)phosphate(C_(6)H_(13)Cl_(2)PO_(4))and mono-chloropropyl phosphate(C_(3)H_(8)ClPO_(4)).Both intracellular and extracellular enzymes could degrade TCPP,but intracellular degradation was dominant in the later reaction stage,and the presence of Cu^(2+) ions had a promoting effect.These findings developed novel insights into the potential mechanism of TCPP microbial degradation.