Organophosphate di- and tri-esters in indoor and outdoor dust from China and its implications for human exposure

Effect of nitrogen oxides and sulfur oxides to triphenyl phosphate degradation and cytotoxicity on surface of different transition metal salts

Nitrogen oxides and sulfur oxides, as the dominant toxic gases in the atmosphere, can induce severe human health problems under the composite pollutant conditions. Currently the effect of nitrogen or sulfur oxides in atmospheric environment to the degradation and cytotoxicity of triphenyl phosphate (TPhP) on atmospheric particle surfaces still remain poorly understood. Hence, laboratory simulation methods were used in this study to investigate the effect and related mechanism. First, particle samples were prepared with the TPhP coated on MnSO4, CuSO4, FeSO4 and Fe2(SO4)3 surface. The results showed that, when nitrogen or sulfur oxides were present, more significant TPhP degradation on all samples can be observed under both light and dark conditions. The results proved nitrogen oxides and sulfur oxides were the vital influence factors to the degradation of TPhP, which mainly promoted the OH generation in the polluted atmosphere. The mechanism study indicated that diphenyl hydrogen phosphate (DPhP) and OH-DPhP were two main stable degradation products. These degradation products originated from the phenoxy bond cleavage and hydroxylation of TPhP caused by hydroxyl radicals. In addition, no TPhP related organosulfates (OSs) or organic nitrates (ON) formation were observed. Regarding the cytotoxicity, all the particles can induce more significant cellular injury and apoptosis of A549 cells, which may be relevant to the adsorbed nitrogen oxides or sulfur oxides on particles surfaces. The superfluous reactive oxygen species (ROS) generation was the possible reason of cytotoxicity. This research can supply a comprehensive understanding of the promoting effect of nitrogen and sulfur oxides to TPhP degradation and the composite cytotoxicity of atmospheric particles.

A randomized controlled trial of a housing intervention to reduce endocrine disrupting chemical exposures in children

Few studies have considered household interventions for reducing endocrine disrupting chemical (EDC) exposures. We conducted a secondary analysis of a randomized controlled trial, originally designed to reduce lead exposure, to evaluate if the intervention lowered EDC exposures in young children. Study participants were children from the Cincinnati, Ohio area (n = 250, HOME Study). Prenatally, families received a housing intervention that included paint stabilization and dust mitigation, or as a control, injury prevention measures. At 24-months, we measured organophosphate esters (OPEs) and phthalates or their metabolites in dust and urine. We measured perfluoroalkyl substances (PFAS) in dust and serum at 24- and 36-months, respectively. We assessed associations between dust and biomarker EDCs using Spearman correlations, characterized EDC mixtures via principal components analysis, and investigated treatment effects using linear regression. To mitigate selection bias, we fit statistical models using inverse probability of retention weights. Correlations between dust EDCs and analogous biomarkers were weak-to-moderate (ρ's ≤ 0.3). The intervention was associated with 23 % (95 % CI: -38, -3) lower urinary DEHP metabolites and, in a per-protocol analysis, 34 % lower (95 % CI: -55, -2) urinary MBZP. Additionally, among Black or African American children, the intervention was associated with lower serum concentrations of several PFAS (e.g., -42 %; 95 % CI: -63, -8 for PFNA). Household interventions that include paint stabilization and dust mitigation may reduce childhood exposures to some phthalates and PFAS in Blacks/African Americans. These findings highlight the need for larger studies with tailored and sustained housing interventions.

Organophosphate Esters in Raw Cow Milk and Cow's Drinking Water and Feed from China: Occurrence, Regional Distribution, and Dietary Exposure Assessment

Organophosphate esters (OPEs) have been widely produced and used, while little is known about their occurrence in the food chain and potential sources. In this study, raw cow milk, cow drinking water, and feed were collected from pastures across China, and OPEs were tested to explore the occurrence and transmission of OPEs in the food chain and to further assess daily OPE intakes for cows and humans via certain food consumption. The median level of ∑OPEs (sum of 15 OPEs) in raw milk was 2140 pg/mL, and tris(1-chloro-2-propyl) phosphate (TCIPP) was the most abundant OPE. Levels of OPEs in water were lower than those in raw milk except for triethyl phosphate (TEP), while levels of most OPEs in feed were significantly higher than those in raw milk (adjusted by dry weight). The estimated dietary intake of OPEs via feed for cows was 2530 ng/kg bw/day, which was much higher than that via water (742 ng/kg bw/day), indicating that feed was a more critical exposure source. For liquid milk consumers, the high-exposure (95th) estimated daily intakes (EDIs) of ∑15OPE were 20 and 7.11 ng/kg bw/day for 3-17 years and adults, respectively, and it is obvious that cows had much heavier OPE intake. Finally, the calculated hazard indexes (HIs) suggested that the intake of OPEs via cow milk consumption would not pose significant health risks to the Chinese population.

Seasonal variations of organophosphate esters (OPEs) in atmospheric deposition, and their contribution to soil loading

Organophosphate esters (OPEs) are ubiquitous in surface soil, and atmospheric deposition is considered to be the major pollution source. However, the research on the environmental transport behaviors of OPEs between atmospheric deposition and soil is very limited. In this study, we investigated the contamination levels and seasonal variations of OPEs in atmospheric deposition samples (n = 33) collected from an area of South China every month between February 2021 and January 2022, and evaluated the contribution of OPEs in atmospheric deposition to soil. The concentrations of ∑21target-OPEs ranged from 3670 to 18,600 ng/g dry weight (dw), with a mean of 8200 ng/g dw (median: 7600 ng/g dw). ∑21target-OPEs concentrations in all atmospheric deposition samples exhibited significant seasonal differences (p < 0.05) with higher concentrations observed in winter and lower concentrations in summer. Tris(2,4-di-tert-butylphenyl) phosphate (TDTBPP) was the most dominant target OPE in atmospheric deposition (4870 ng/g dw), and its seasonal variation trend was consistent with ∑21OPEs (p < 0.05). Simultaneously, in order to further explore the effect of atmospheric deposition on the levels of OPEs in soil of the study region, input fluxes and accumulation increments were estimated. Ten OPEs (including seven target OPEs and three suspect OPEs) exhibited high input flux means and accumulation increments, indicating that these compounds are prone to accumulate in soil via atmospheric deposition. It is noteworthy that the non-target phosphonate analyte bis(2,4-di-tert-butylphenyl) dibutyl ethane-1,2-diylbis(phosphonate) (BDTBPDEDBP) was detected at highest median concentration (8960 ng/g dw) in atmospheric deposition. Correspondingly, the average input flux and accumulation increment of BDTBPDEDBP were higher than those of all target and suspect OPEs. Collectively, this study quantifies the environmental transport behavior of OPEs between atmospheric deposition and soil, and provides new evidences for the fact that atmospheric deposition is the important pollution source of OPEs in soil.

Photocatalytic degradation of organophosphorus flame retardants in aqueous solutions: a review and future prospects

The widespread use of organophosphorus flame retardants (OPFRs) in industrial and household products increases the risk of their environmental exposure, posing a serious threat to ecosystems and human health. Photocatalytic technology has been widely used in wastewater treatment due to its high efficiency, mild reaction conditions, and robustness. This review summarizes the current status of research on photocatalytic degradation of OPFRs, focusing on the effect of different types of catalysts on the degradation efficiency, the effects of pH, and co-existing inorganic and organic ions. And pH and co-existing inorganic mainly affect the active oxygen and the active surface sites of the catalyst. In addition, toxicological calculations of the intermediates of the degradation pathway using T.E.S.T. and ECOSAR showed that photocatalysis could effectively reduce the toxicity of OPFRs. Development of new photocatalytic materials, in-depth study of the degradation mechanism of different catalysts and flame retardants, and attention to practical applications and toxicity issues can be the development direction of future research.

Nephrotoxicity of organophosphate flame retardants in patients with chronic kidney disease: A 2-year longitudinal study

Humans are extensively exposed to organophosphate flame retardants (OPFRs), an emerging group of organic contaminants with potential nephrotoxicity. Nevertheless, the estimated daily intake (EDI) and prognostic impacts of OPFRs have not been assessed in individuals with chronic kidney disease (CKD). In this 2-year longitudinal study of 169 patients with CKD, we calculated the EDIs of five OPFR triesters from urinary biomonitoring data of their degradation products and analyzed the effects of OPFR exposure on adverse renal outcomes and renal function deterioration. Our analysis demonstrated universal OPFR exposure in the CKD population, with a median EDIΣOPFR of 360.45 ng/kg body weight/day (interquartile range, 198.35-775.94). Additionally, our study revealed that high tris(2-chloroethyl) phosphate (TCEP) exposure independently correlated with composite adverse events and composite renal events (hazard ratio [95 % confidence interval; CI]: 4.616 [1.060-20.096], p = 0.042; 3.053 [1.075-8.674], p = 0.036) and served as an independent predictor for renal function deterioration throughout the study period, with a decline in estimated glomerular filtration rate of 4.127 mL/min/1.73 m2 (95 % CI, -8.127--0.126; p = 0.043) per log ng/kg body weight/day of EDITCEP. Furthermore, the EDITCEP and EDIΣOPFR were positively associated with elevations in urinary 8-hydroxy-2'-deoxyguanosine and kidney injury molecule-1 during the study period, indicating the roles of oxidative damage and renal tubular injury in the nephrotoxicity of OPFR exposure. To conclude, our findings highlight the widespread OPFR exposure and its possible nephrotoxicity in the CKD population.

Contamination Status of Novel Organophosphate Esters Derived from Organophosphite Antioxidants in Soil and the Effects on Soil Bacterial Communities

The contamination status of novel organophosphate esters (NOPEs) and their precursors organophosphite antioxidants (OPAs) and hydroxylated/diester transformation products (OH-OPEs/di-OPEs) in soils across a large-scale area in China were investigated. The total concentrations of the three test NOPEs in soil were 82.4-716 ng g-1, which were considerably higher than those of traditional OPEs (4.50-430 ng g-1), OPAs (n.d.-30.8 ng g-1), OH-OPEs (n.d.-0.49 ng g-1), and di-OPEs (0.57-21.1 ng g-1). One NOPE compound, i.e., tris(2,4-di-tert-butylphenyl) phosphate (AO168 = O) contributed over 65% of the concentrations of the studied OPE-associated contaminants. A 30-day soil incubation experiment was performed to confirm the influence of AO168 = O on soil bacterial communities. Specific genera belonging to Proteobacteria, such as Lysobacter and Ensifer, were enriched in AO168 = O-contaminated soils. Moreover, the ecological function of methylotrophy was observed to be significantly enhanced (t-test, p < 0.01) in soil treated with AO168 = O, while nitrogen fixation was significantly inhibited (t-test, p < 0.01). These findings comprehensively revealed the contamination status of OPE-associated contaminants in the soil environment and provided the first evidence of the effects of NOPEs on soil microbial communities.

Analysis of 78 trace liquid crystal monomers in air by gas chromatography coupled with triple quadrupole mass spectrometry

Liquid crystal monomers (LCMs) comprise a class of organic pollutants that have garnered considerable attention because of their dioxin-like toxicity (i.e., modulation of genes) and presence in various environments. However, limited information about the identities, occurrence, and distribution of LCMs has highlighted an urgent need for a high-throughput and sensitive analytical method. In this study, we developed and validated a rapid, simple, sensitive method that involves minimal solvent consumption. The method was applied for the simultaneous detection and identification of 78 LCMs in atmospheric total suspended particulate samples (dae < 100 μm) using gas chromatography coupled with triple quadrupole mass spectrometry. The results showed high degrees of linearity with correlation coefficients >0.995 in the concentration range of 5.0-500 ng/mL. The instrumental detection limits ranged from 0.7 to 5.3 pg, and the method detection limits ranged from 0.1 to 0.9 pg/m3. The accuracy of the method was between 70 % and 130 % for most analytes, and the relative standard deviations of six replicates were <15 % at three levels of spiking (10, 50, and 200 ng/mL). The developed analytical method was applied to analyze real air particulate samples from Beijing, China. Overall, 45 LCMs ranged from 65.5 to 145.7 pg/m3, with a mean concentration of 92.5 pg/m3. Among them, (trans,trans)-4-propyl-4'-ethenyl-1,1'-bicyclohexane (PVB) was the most abundant, with an average concentration of 33.6 pg/m3. The total estimated daily intakes of LCMs for adults and children were 15.6 and 46.6 pg/kg bw/day, respectively. Accordingly, the method described herein is suitable for quantifying LCMs in atmospheric particulate samples. This study will be valuable for investigating LCM environmental occurrence, behaviors, and risk assessments.

Molecular insight on the binding of halogenated organic phosphate esters to human serum albumin and its effect on cytotoxicity of halogenated organic phosphate esters

Halogenated Organic Phosphate Esters (OPEs) are commonly found in plasticizers and flame retardants. However, they are one kind of persistent contaminants that can pose a significant threat to human health and ecosystem as new environmental estrogen. In this study, two representative halogenated OPEs, tris(1,3-dichloro-2-propyl) phosphate (TDCP) and tris(2,3-dibromopropyl) phosphate (TDBP), were selected as experimental subjects to investigate their interaction with human serum albumin (HSA). Despite having similar structures, the two ligands exhibited contrasting effects on enzyme activity of HSA, TDCP inhibiting enzyme activity and TDBP activating it. Furthermore, both TDCP and TDBP could bind to HSA at site I, interacted with Arg222 and other residues, and made the conformation of HSA unfolded. Thermodynamic parameters indicated the main driving forces between TDBP and HSA were hydrogen bonding and van der Waals forces, while TDCP was mainly hydrophobic force. Molecular simulations found that more hydrogen bonds of HSA-TDBP formed during the binding process, and the larger charge area of TDBP than TDCP could partially account for the differences observed in their binding abilities to HSA. Notably, the cytotoxicity of TDBP/TDCP was inversely proportional to their binding ability to HSA, implying a new method for determining the cytotoxicity of halogenated OPEs in vitro.

Degradation, transformation and cytotoxicity of triphenyl phosphate on surface of different transition metal salts in atmospheric environment

Triphenyl phosphate (TPhP) and transition metal elements have been ubiquitously detected in the atmosphere, which can participate in atmospheric chemical reactions and induce damage to human health. Currently the understanding of TPhP degradation, transformation and cytotoxicity on atmospheric particles surface are still limited. Therefore, this study used laboratory simulation methods to investigate the influence of irradiation time, transition metal salts, relative humidity (RH) to TPhP degradation, transformation and relative cytotoxicity. TPhP was coated on particle surfaces of four transition metal salts (MnSO4, CuSO4, FeSO4 and Fe2(SO4)3) in the experiment. Within 12 h irradiation, the significant TPhP photodegradation can be observed on all particles surface. Among these influence factors, the irradiation and RH were the crucial aspects to TPhP degradation, which primarily affect the OH concentration in the atmosphere. The transition metal elements only exhibited slightly catalytic effect to TPhP degradation. The mechanism study indicated that the major degradation products of TPhP are diphenyl hydrogen phosphate (DPhP) and OH-DPhP, which originated from the phenoxy bond cleavage and hydroxylation of TPhP induced by OH. As for the cytotoxicity to A549 cells, all the transition metal particles coated with TPhP can cause cellular injury, which was chiefly induced by the transition metal salt. The possible cytotoxicity mechanism of these particles to A549 cells can be attributed to the excessive reactive oxygen species (ROS) production. This study may provide a further understanding of TPhP degradation and related cytotoxicity with the coexistent transition metal salts in the atmosphere.

Investigation of Urinary Metabolites of Organophosphate Esters in Hanoi, Vietnam: Assessment Exposure and Estimated Daily Intake

In recent years, organophosphate esters (OPEs) have become one of the most common additives in various consumer products worldwide, therefore the exposure and impact of OPEs on human health are drawing a lot of attention. In this study, three metabolites of OPEs including bis(1,3-dichloro-2-propyl) phosphate (BDCIPP), diphenyl phosphate (DPhP) and diethyl phosphate (DEP) were investigated in first-morning void urine samples taken from a population (age range: 3-76 years old) in Hanoi, Vietnam. The most dominant urinary OPE metabolite was DEP with the geometric mean of specific gravity adjust (SG-adjusted) concentration were 1960 ng mL-1 and detected frequency (DF) of 98%. Followed by DPhP (8.01 ng mL-1, DF: 100%) and BDCIPP (2.18 ng mL-1, DF: 51%). The results indicated that gender and age might have associations with the OPE metabolites variation in urine samples. The levels of OPE metabolites in urine samples from females were slightly higher than in males. An increase in age seems to have an association with a decrease in DPhP levels in urine. Exposure doses of parent OPEs were evaluated from the unadjusted urinary concentration of corresponding OPE metabolite. The estimated exposure doses of triethyl phosphate (TEP) (mean: 534,000 ng kg-1 d-1) were significantly higher than its corresponding reference dose, suggesting the high potential risk from the current exposure doses of TEP to human health. The results of this work provided the initial information on the occurrence of three OPE metabolites in urine from Hanoi, Vietnam and estimated exposure dose of corresponding parent OPEs.

Organophosphate triesters and their diester degradation products in the atmosphere-A critical review

Organophosphate triesters (tri-OPEs) have found substantial use as plasticizers and flame retardants in commercial and industrial products. Despite upcoming potential restrictions on use of OPEs, widespread environmental contamination is likely for the foreseeable future. Organophosphate diesters (di-OPEs) are known biotic or abiotic degradation products of tri-OPEs. In addition, direct use of di-OPEs as commercial products also contributes to their presence in the atmosphere. We review the available data on contamination with tri-OPEs and di-OPEs in both indoor and outdoor air. Concentrations of tri-OPEs in indoor air exceed those in outdoor air. The widespread discovery of tri-OPE traces in polar regions and oceans is noteworthy and is evidence that they undergo long-range transport. There are only two studies on di-OPEs in outdoor air and no studies on di-OPEs in indoor air until now. Current research on di-OPEs in indoor and outdoor air is urgently needed, especially in countries with potentially high exposure to di-OPEs such as the UK and the US. Di-OPE concentrations are higher at e-waste dismantling areas than at surrounding area. We also summarise the methods employed for sampling and analysis of OPEs in the atmosphere and assess the relative contribution to atmospheric concentrations of di-OPEs made by environmental degradation of triesters, compared to the presence of diesters as by-products in commercial triester products. Finally, we identify shortcomings of current research and provide suggestions for future research.

Aromatic amine antioxidants (AAs) and p-phenylenediamines-quinones (PPD-Qs) in e-waste recycling industry park: Occupational exposure and liver X receptors (LXRs) disruption potential

Recently, evidence of aromatic amine antioxidants (AAs) existence in the dust of the electronic waste (e-waste) dismantling area has been exposed. However, there are limited studies investigating occupational exposure and toxicity associated with AAs and their transformation products (p-phenylenediamines-quinones, i.e., PPD-Qs). In this study, 115 dust and 42 hand wipe samples collected from an e-waste recycling industrial park in central China were analyzed for 19 AAs and 6 PPD-Qs. Notably, the median concentration of ∑6PPD-Qs (1,110 ng/g and 1,970 ng/m2) was significantly higher (p < 0.05, Mann-Whitney U test) than that of ∑6PPDs (147 ng/g and 34.0 ng/m2) in dust and hand wipes. Among the detected analytes, 4-phenylaminodiphenylamine quinone (DPPD-Q) (median: 781 ng/g) and 1,4-Bis(2-naphthylamino) benzene quinone (DNPD-Q) (median: 156 ng/g), were particularly prominent, which were first detected in the e-waste dismantling area. Occupational exposure assessments and nuclear receptor interference ability, conducted through estimated daily intake (EDI) and molecular docking analysis, respectively, indicated significant occupational exposure to PPD-Qs and suggested prioritized Liver X receptors (LXRs) disruption potential of PPDs and PPD-Qs. The study provides the first evidence of considerable levels of AAs and PPD-Qs in the e-waste-related hand wipe samples and underscores the importance of assessing occupational exposure and associated toxicity effects.

Co-occurrence of organophosphate diesters and organophosphate triesters in daily household products: Potential emission and possible human health risk

Eight paired organophosphate diesters (Di-OPs) and organophosphate triesters (Tri-OPs) were investigated in wipes from analytical instruments and 47 material samples related to household products, including textiles, electrical/electronic devices, building/ decoration materials and children's products. The total concentrations of Di-OPs ranged in 3577-95551 ng/m2 in the wipes and limit of detection-23002 ng/g in the materials. The Tri-OPs concentrations varied significantly in the ranges of 107218-1756892 ng/m2 and 2.13-503149 ng/g, respectively. Four industrial Di-OPs were detected in > 65% of the studied samples suggesting their direct application in the studied materials. Furthermore, we demonstrated for the first time that four non-industrial Di-OPs, e.g., bis(2-chloroethyl) phosphate, bis(1-chloro-2-propyl) phosphate, bis(1,3-dichloro-2-propyl) phosphate, and bis(butoxyethyl) phosphate, identified as degradation products of their respective Tri-OPs were also detected in these studied samples, which might act as important emission sources of Di-OPs in indoor environments. We estimated the burden of Di-OPs and Tri-OPs in a typical residential house and instrumental room, which both exhibited important contributions from furniture, building and decoration materials, and electrical/electronic devices. Limit health risk was posed to local people via air inhalation.

Co-occurrence of organophosphate esters and phosphorus fractions in river sediments: Implications for pollution prediction and environment risk assessment

Organophosphate esters (OPEs) and phosphorus (P) are widespread pollutants in aquatic ecosystems, presenting potential ecological risks. However, there is still a lack of comprehensive understanding of their relationships in sediments. In this study, we investigated the co-occurrence and behaviors of the OPEs and P in urban river sediments. The results indicated serious OPE and P pollution in the study area, with substantial spatial variations in the contents and compositions. The OPE congeners and P fractions exhibited different correlations, particularly more significant linear relationships (R = 0.455 - 0.816, p < 0.05) were observed between the aryl-OPEs and P fractions, potentially due to the influence from sources, physicochemical properties, and total organic carbon. About 56 to 71% of variability in predicting the concentrations of aryl-OPE can be explained by the multiple linear regression model using the Fe/Al- and Ca-bound P contents. The study regions exhibited greater aryl-OPEs ecological risks were consistent with the regions with more serious Total P pollution levels. This study represents the first report demonstrating the potential of Fe/Al-P and Ca-P contents in predicting aryl-OPE contents in heavily polluted sediments, providing a useful reference to comprehensively assess the occurrence and environmental behaviors of aryl-OPEs in anthropogenic polluted sediments.

Characteristics, sources, bio-accessibility, and health risks of organophosphate esters in urban surface dust, soil, and dustfall in the arid city of Urumqi in China

Sixty-eight paired samples of urban surface dust and soil as well as four samples of atmospheric dustfall were collected from the arid city of Urumqi in Northwest China. Thirteen organophosphate esters (OPEs) in these samples were analyzed for the characteristics, sources, bio-accessibility, and health risks of OPEs. The studied OPEs were widely detected in the urban surface dust, soil, and dustfall, with Σ13OPEs (total concentration of 13 OPEs) of 1362, 164.0, and 1367 ng/g, respectively, dominated by tris(2-chloroethyle) phosphate (TCEP), tri(2-chloroisopropyl) phosphate (TCiPP), tri(1, 3-dichloroisopropyl) phosphate (TDCiPP) and tris(2-butoxyethyl) phosphate (TBOEP), TBOEP and tri(2-ethylhexyl) phosphate (TEHP), and TCEP, TCiPP, TBOEP, triphenyl phosphate and TEHP, respectively. The low and high frequency magnetic susceptibility of surface dust and urban soil might indicate the pollution of OPEs in them. Elevated levels of the Σ13OPEs in the surface dust and urban soil were found in the west, south, and northeast of Urumqi city. The total deposition flux of dustfall-bound 13 OPEs ranged from 86.5 to 143 ng/m2/day, with a mean of 105 ng/m2/day. OPEs in the surface dust and urban soil were associated with the emissions of indoor and outdoor products containing OPEs, the dry and wet deposition of atmosphere, and the emissions of traffic. Trimethyl phosphate, triethyl phosphate, tripropyl phosphate, tri-isobutyl phosphate, TCEP, TCiPP, TDCiPP, and TBOEP in surface dust and urban soil had relatively high bio-accessibility. The bio-accessibility of OPEs was mainly affected by the physio-chemical properties of OPEs. The non-cancer and cancer risks of human exposure to OPEs in surface dust and urban soil were relatively low or negligible. The current research results may provide scientific supports for prevention and control of pollution and risks of OPEs.

Physiologically based toxicokinetic modelling of Tri(2-chloroethyl) phosphate (TCEP) in mice accounting for multiple exposure routes

Exposure routes are important for health risk assessment of chemical risks. The application of physiologically based toxicokinetic (PBTK) models to predict concentrations in vivo can determine the effects of harmful substances and tissue accumulation on the premise of saving experimental costs. In this study, Tri(2-chloroethyl) phosphate (TCEP), an organophosphate ester (OPE), was used as an example to study the PBTK model of mice exposed to different exposure doses by multiple routes. Different routes of exposure (gavage and intradermal injection) can cause differences in the concentration of chemicals in the organs. TCEP that enters the body through the mouth is mainly concentrated in the gastrointestinal tract and liver. However, the concentrations of chemicals that enter the skin into the mice are higher in skin, rest of body, and blood. In addition, TCEP was absorbed and accumulated very rapidly in mice, within half an hour after a single exposure. We have successfully established a mouse PBTK model of the TCEP accounting for multiple exposure Routes and obtained a series of kinetic parameters. The model includes blood, liver, kidney, stomach, intestine, skin, and rest of body compartments. Oral and dermal exposure route was considered for PBTK model. The PBTK model established in this study has a good predictive ability. More than 70% of the predicted values deviated from the measured values by less than 5-fold. In addition, we extrapolated the model to humans. A human PBTK model is built. We performed a health risk assessment for world populations based on human PBTK model. The risk of TCEP in dust is greater through mouth than through skin. The risk of TCEP in food of Chinese population is greater than dust.

An overview of current knowledge on organophosphate di-esters in environment: Analytical methods, sources, occurrence, and behavior

Organophosphate di-esters (di-OPEs) are highly related to tri-OPEs. The presence of di-OPEs in the environment has gained global concerns, as some di-OPEs are more toxic than their respective tri-OPE compounds. In this study, current knowledge on the analytical methods, sources, environmental occurrence, and behavior of di-OPEs were symmetrically reviewed by compiling data published till March 2023. The determination of di-OPEs in environmental samples was exclusively achieved with liquid chromatography mass spectrometry operated in negative mode. There are several sources of di-OPEs, including industrial production, biotic and abiotic degradation from tri-OPEs under environmental conditions. A total of 14 di-OPE compounds were determined in various environments, including dust, sediment, sludge, water, and atmosphere. The widespread occurrence of di-OPEs suggested that human and ecology are generally exposed to di-OPEs. Among all environmental matrixes, more data were recorded for dust, with the highest concentration of di-OPEs up to 32,300 ng g-1. Sorption behavior, phase distribution, gas-particle partitioning behavior was investigated for certain di-OPEs. Suggestions on future studies in the perspective of human exposure to and environmental behavior of di-OPEs were proposed.

Organophosphate esters (OPEs) and novel brominated flame retardants (NBFRs) in indoor dust: A systematic review on concentration, spatial distribution, sources, and human exposure

In recent years, the indoor exposure of organophosphate esters (OPEs) and novel brominated flame retardants (NBFRs) has received widespread attention worldwide. Using published data on 6 OPEs in 23 countries (n = 1437) and 2 NBFRs in 18 countries (n = 826) in indoor dust, this study systematically reviewed the concentrations, spatial distribution, sources and exposure risk of 8 flame retardants (FRs) worldwide. Tris(chloroisopropyl)phosphate (TCIPP) is the predominant FR with a median concentration of 1050 ng g-1 ΣCl-OPEs are significantly higher than Σnon-Cl-OPEs (p < 0.05). ΣOPEs in indoor dust from industrially-developed countries are higher than those from the countries lacking industrial development. Household appliances, electronics and plastic products are the main sources of non-Cl-OPEs and NBFRs, while interior decorations and materials contribute abundant Cl-OPEs in indoor dust. The mean hazard index (HI) of TCIPP for children is greater than 1, possibly posing non-cancer risk for children in some countries. The median ILCRs for 3 carcinogenic OPEs are all less than 10-6, suggesting no cancer risk induced by these compounds for both adults and children. This review helps to understand the composition, spatial pattern and human exposure risk of OPEs and NBFRs in indoor dust worldwide.

Toxicity assessment of organophosphate flame retardant triphenyl phosphate (TPHP) on intestines in mice

Triphenyl phosphate (TPHP), one widely used organophosphate flame retardant, has attracted accumulating attention due to its high detection rate in human biological samples. Up to date, the effects of TPHP exposure on intestinal health remain unexplored. In this study, BALB/c mice were used as a model and exposed to TPHP at dose of 2, 10, or 50 mg/kg body weight for 28 days. We observed Crohn's disease-like features in ileum and ulcerative colitis disease-like features in colon, such as shorter colon length, ileum/colon structure impairment, intestinal epithelial cell apoptosis, enrichment of proinflammatory cytokines and immune cells, and disruption of tight junction. Furthermore, we found that TPHP induced production of reactive oxygen species and apoptosis in intestinal epithelial Caco-2 cells, accompanied by disruption of tight junction between cells. To understand the molecular mechanism underlying TPHP-induced changes in intestines, we build the adverse outcome pathway (AOP) framework based on Comparative Toxicogenomics and GeneCards database. The AOP framework revealed that PI3K/AKT and FoxO signaling pathway might be associated with cellular apoptosis, an increase in ROS production, and increased inflammation response in mouse ileum and colon tissues challenged with TPHP. These results identified that TPHP induced IBD-like features and provided new perspectives for toxicity evaluation of TPHP.

Organophosphorus flame retardants and their metabolites in paired human blood and urine

Organophosphorus flame retardants (OPFRs) have been shown to be carcinogenic, neurotoxic, and endocrine disruptive, so it is important to understand the levels of OPFRs in human body as well as the modes of external exposure. In this study, we investigated the levels of 13 OPFRs and 7 phosphodiester metabolites in paired human blood and urine, as well as the influencing factors (region, age and gender), and studied the relationship between OPFRs and oxidative stress by urinary metabolites. We found that the concentrations of triphenyl phosphate (TPhP) and tris-(2-ethylhexyl) phosphate (TEHP) in the blood of urban populations were higher than those of rural populations, and that younger populations suffered higher TPhP and 2-ethylhexyl diphenyl phosphate (EHDPP) exposures than older populations. In addition, we found that tris-(2-chloroethyl) phosphate (TCEP), tributyl phosphate (TnBP), TPhP and EHDPP exposure induced oxidative stress. The results of the internal load principal component analysis indicated that dust ingestion, skin exposure, respiration and dietary intake may be the most important sources of TCEP, tris(2-butoxyethyl) phosphate (TBOEP), tri(2-chloroisopropyl) phosphate (TCIPP) and TEHP, respectively, and dust ingestion and skin exposure may be the main sources of TPhP for humans.

Distribution characteristics, source attribution, and health risk assessment of organophosphate esters in indoor and outdoor dust from various microenvironments in Beijing

The occurrence and profiles of organophosphate esters (OPEs) were studied in indoor and outdoor dusts from various microenvironments, including forty-seven outdoor dusts from green belts, roads, parks and residence areas, seventy-seven indoor dusts from private cars, print shops, taxis, furniture shops, offices, dormitories, shopping malls and residences house in different districts in Beijing. The total concentrations (Σ12OPEs) were eighteen times higher in indoor dusts (7.14 ×102 to 2.24 ×104 ng/g) than in outdoor dusts (36.0-1.56 ×103 ng/g). OPEs concentrations in samples from taxi and private cars were obviously higher than other indoor microenvironments. Both indoor and outdoor microenvironments also showed different compositional profiles of OPEs, indicating that polyurethane foam/building materials and hydraulic fluids/plastics were the greatest contributions in different microenvironments, with chlorinated alkyl phosphates (Cl-OPEs) being the predominant compound in both indoor dust (52.1-86.5%) and outdoor dust samples (42.6-81.3%). The uncertainty was reduced by Monte Carlo simulation, and the pollution levels of 50th and 95th percentiles were employed to calculate the average daily dosage, which was then used to calculate hazard quotient (HQ) for assessing the health risks to adults and children. Results showed that OPEs were safe even at extremely consumed concentration percentile (95th) in all groups.

Occurrence, source apportionment, and ecological risk assessment of organophosphate esters in surface sediment from the Ogun and Osun Rivers, Southwest Nigeria

Organophosphate esters (OPEs) are synthetic chemicals widely used as e.g., flame retardants and plasticisers in various consumer products. Due to the toxicity of OPEs in aquatic ecosystems, exposure of fauna and flora to these compounds is of potential concern. In this study, the concentrations, profiles, sources, and ecological risk of eight OPEs were investigated in the sediments from the two major rivers in southwest Nigeria. Concentrations of ∑OPEs in surface sediments were in the range 13.1 - 2110 ng/g dry weight (dw) (median: 378 ng/g dw) in the Ogun River and 24.7-589 ng/g dw (median: 174 ng/g dw) in the Osun River. These concentrations are broadly within the range of those reported in surface sediment in previous studies conducted in other locations around the world. Tris (2-butoxyethyl) phosphate (TBOEP) was the dominant OPE in the sediment samples with a median concentration of 337 and 126 ng/g dw for the Ogun and Osun Rivers respectively, while tri-n-butyl phosphate (TnBP) was not detected in any sample. Excluding TBOEP, the chlorinated organophosphate esters: tris(2-chloroethyl) phosphate (TCEP), tris(2-chloro-propyl) phosphate (TCIPP), and tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) were the dominant OPEs in the Osun River, while the aryl-OPEs: triphenyl phosphate (TPHP), 2-ethylhexyl diphenyl phosphate (EHDPP), and tri-m-tolyl phosphate (TMTP) were dominant in the Ogun River. Under a median exposure scenario, moderate ecological risk was predicted from exposure to TCIPP in the Osun River. In contrast, under a high exposure scenario, concentrations of TDCIPP (risk quotient, RQ = 5.33-5.37) constituted a high ecological risk in both rivers, with moderate risks observed for TBOEP (RQ = 0.022-0.18) and TCIPP (RQ = 0.097 - 0.16). Therefore, the risk to aquatic organisms from concomitant exposure to mixtures of OPEs in freshwater ecosystems requires further investigation.

Review on typical organophosphate diesters (di-OPEs) requiring priority attention: Formation, occurrence, toxicological, and epidemiological studies

The impact of primary metabolites of organophosphate triesters (tri-OPEs), namely, organophosphate diesters (di-OPEs), on the ecology, environment, and humans cannot be ignored. While extensive studies have been conducted on tri-OPEs, research on the environmental occurrence, toxicity, and health risks of di-OPEs is still in the preliminary stage. Understanding the current research status of di-OPEs is crucial for directing future investigations on the production, distribution, and risks associated with environmental organophosphate esters (OPEs). This paper specifically reviews the metabolization process from tri-OPEs to di-OPEs and the occurrence of di-OPEs in environmental media and organisms, proposes typical di-OPEs in different media, and classifies their toxicological and epidemiological findings. Through a comprehensive analysis, six di-OPEs were identified as typical di-OPEs that require prioritized research. These include di-n-butyl phosphate (DNBP), bis(2-butoxyethyl) phosphate (BBOEP), bis(1,3-dichloro-2-propyl) phosphate (BDCIPP), bis(2-chloroethyl) phosphate (BCEP), bis(1-chloro-2-propyl) phosphate (BCIPP), and diphenyl phosphate (DPHP). This review provides new insights for subsequent toxicological studies on these typical di-OPEs, aiming to improve our understanding of their current status and provide guidance and ideas for research on the toxicity and health risks of di-OPEs. Ultimately, this review aims to enhance the risk warning system of environmental OPEs.

Nontarget Identification of Novel Organophosphorus Flame Retardants and Plasticizers in Rainfall Runoffs and Agricultural Soils around a Plastic Recycling Industrial Park

Plastic recycling and reprocessing activities may release organophosphate ester (OPE) flame retardants and plasticizers into the surrounding environment. However, the relevant contamination profiles and impacts remain not well studied. This study investigated the occurrence of 28 OPEs and their metabolites (mOPEs) in rainfall runoffs and agricultural soils around one of the largest plastic recycling industrial parks in North China and identified novel organophosphorus compounds (NOPs) using high-resolution mass spectrometry-based nontarget analysis. Twenty and twenty-seven OPEs were detected in runoff water and soil samples, with total concentrations of 86.0-2491 ng/L and 2.53-199 ng/g dw, respectively. Thirteen NOPs were identified, of which eight were reported in the environment for the first time, including a chlorine-containing OPE, an organophosphorus heterocycle, a phosphite, three novel OPE metabolites, and two oligomers. Triphenylphosphine oxide and diphenylphosphinic acid occurred ubiquitously in runoffs and soils, with concentrations up to 390 ng/L and 40.2 ng/g dw, respectively. The downwind areas of the industrial park showed elevated levels of OPEs and NOPs. The contribution of hydroxylated mOPEs was higher in soils than in runoffs. These findings suggest that plastic recycling and reprocessing activities are significant sources of OPEs and NOPs and that biotransformation may further increase the ecological and human exposure risk.

Organophosphate esters in soils of Beijing urban parks: Occurrence, potential sources, and probabilistic health risks

Organophosphate esters (OPEs) are an emerging contaminant widely distributed in the soil. OPEs have drawn increasing attention for their biological toxicity and possible threat to human health. This research investigated the pollution characteristics of two typical OPEs, organophosphate triesters (tri-OPEs) and organophosphate diesters (di-OPEs), in soils of 104 urban parks in Beijing. The median concentrations of Σ₁₁tri-OPEs and Σ₈di-OPEs were 157 and 17.9 ng/g dw, respectively. Tris(2-chloroisopropyl) phosphate and bis(2-ethylhexyl) phosphate were the dominant tri-OPE and di-OPE, respectively. Consumer materials (such as building insulation and decorative materials), traffic emissions, and reclaimed water irrigation may be critical sources of tri-OPEs in urban park soils. Di-OPEs mainly originated from the degradation of parent compounds and industrial applications. Machine learning models were employed to determine the influencing factors of OPEs and predict changes in their concentrations. The predicted OPEs concentrations in Beijing urban park soils in 2025 and 2030 are three times and five times those in 2018, respectively. According to probabilistic health risk assessment, non-carcinogenic and carcinogenic risks of OPEs can be negligible for children and adults. Our results could inform measures for preventing and controlling OPEs pollution in urban park soils.

Co-occurrence and distribution of organophosphate tri- and di-esters in dust and hand wipes from an e-waste dismantling plant in central China

Electronic waste (e-waste) dismantling facilities are a well-known source of emerging contaminants including organophosphate esters (OPEs). However, little information is available regarding the release characteristics and co-contaminations of tri- and di-esters. This study, therefore, investigated a broad range of tri- and di-OPEs in dust and hand wipe samples collected from an e-waste dismantling plant and homes as comparison. The median ∑tri-OPE and ∑di-OPE levels in dust and hand wipe samples were approximately 7- and 2-fold higher than those in the comparison group, respectively (p < 0.01). Triphenyl phosphate (median: 11,700 ng/g and 4640 ng/m²) and bis(2-ethylhexyl) phosphate (median: 5130 ng/g and 940 ng/m²) were the dominant components of tri- and di-OPEs, respectively. The combination of Spearman rank correlations and the determinations of molar concentration ratios of di-OPEs to tri- OPEs revealed that apart from the degradation of tri-OPEs, di-OPEs could originate from direct commercial application, or as impurities in tri-OPE formulas. Significant positive correlations (p < 0.05) were found for most tri- and di-OPE levels between the dust and hand wipes from dismantling workers, whereas this was not observed in those from the ordinary microenvironment. Our results provide robust evidence that e-waste dismantling activities contribute to OPEs contamination in the surroundings and further human exposure pathways and toxicokinetics are needed to be elucidated.

Serum Organophosphate Flame retardants and plasticizers in Chinese females of childbearing age: Association with serum reproductive and thyroid hormones

Organophosphate flame retardants (OPFRs) are extensively used as flame retardants and plasticizers, but their endocrine disrupting potentials have raised concerns. However, the impacts of OPFR exposures on reproductive and thyroid hormones in females remains unclear. In this study, serum concentrations of OPFRs were investigated, and levels of reproductive and thyroid hormones, including follicle-stimulating hormone (FSH), luteinizing hormone (LH), estradiol, anti-Müllerian hormone, prolactin (PRL), testosterone (T), and thyroid stimulating hormone, were analyzed in childbearing-age females undergoing in-vitro fertilization treatment from Tianjin, a coastal city in China (n = 319). Tris (2-chloroethyl) phosphate (TCEP) was the predominant OPFR, with a median concentration of 0.33 ng/mL and a detection frequency of 96.6%. In the whole population, tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) and tris(2-chloroisopropyl) phosphate (TCIPP) were positively associated with T (p < 0.05), while triethyl phosphate (TEP) was negatively associated with LH (p < 0.05) and LH/FSH (p < 0.01). Particularly, TCIPP was negatively associated with PRL in the younger subgroup (age≤30, p < 0.05). Moreover, TCIPP was negatively associated with diagnostic antral follicle counting (AFC) in the mediation analysis by a dominating direct effect (p < 0.01). In conclusion, serum levels of OPFRs were significantly associated with reproductive and thyroid hormone levels and a risk of decreased ovarian reserve in childbearing-age females, with age and body mass index being significant influencing factors.

A critical review on sources and environmental behavior of organophosphorus flame retardants in the soil: Current knowledge and future perspectives

Organophosphorus flame retardants (OPFRs) have been widely used in industrial and commercial applications. Unfortunately, the chemical constituents of OPFRs, organophosphate esters (OPEs), which have been proven to be carcinogenic and biotoxic, can release into the environment and pose potential risks to human health. This paper reviews the research progress of OPEs in the soil through bibliometric analysis and comprehensively elaborates on their pollution status, potential sources, and environmental behaviors. The OPE pollution is widely distributed in the soil at concentrations ranging from several to tens of thousands of ng/g dw. Some novel OPEs, newly discovered OPEs in the environment in recent years, are also detected. OPE concentrations vary substantially among landuses, and waste processing areas are important point sources of OPE pollution in the soil. Emission source intensity, physicochemical properties of compounds, and soil properties play important roles in the transfer process of OPEs in the soil. Biodegradation, especially microbial degradation, has potential application prospects in the remediation of OPE-contaminated soil. Brevibacillus brevis, Sphingomonas, Sphingopyxis, Rhodococcus, and other microorganisms can degrade some OPEs. This review helps clarify the pollution status of OPEs in the soil and highlights perspectives for future research.

Organophosphate tri- and diesters in source water supply and drinking water treatment systems of a metropolitan city in China

The water contaminations with organophosphate triesters (tri-OPEs) and diesters (di-OPEs) have recently provoked concern. However, the distributions of these compounds in natural water sources and artificial water treatment facilities are poorly characterized. A comprehensive study was therefore performed to measure their concentrations in a water source, a long-distance water pipeline, and a drinking water treatment plant (DWTP). Eight tri-OPEs and 3 di-OPEs were found to be widely distributed, with total concentrations in source water and pipelines ranging from 290.6 to 843.9 ng/L. The most abundant pollutants were tris(1-chloro-2-propyl) phosphate (TCPP), triethyl phosphate, tri-n-butyl phosphate (TnBP), and diphenyl phosphate (DPhP). Di-OPEs appeared to be removed less efficiently in the DWTP than the parent tri-OPEs, and the elimination efficiencies of tri-OPEs were structure-dependent. Long-distance pipeline transportation had no significant effect on the distributions of tri- and di-OPEs. Statistical analysis suggested that the sources of di-OPEs and the corresponding tri-OPEs differed, as did those of DPhP and di-n-butyl phosphate. A risk analysis indicated that tri-OPEs present limited ecological risks that are mainly due to TnBP and TCPP, and that the human health risks of tri-OPEs are negligible. However, di-OPEs (especially DPhP) may increase these risks. Further studies on the risks posed by di-OPEs in aquatic environments are therefore needed.

Regional distribution of the plastic additive tris(butoxyethyl) phosphate in Nanyang Lake estuary, China, and toxic effects on Cyprinus carpio

There is increasing concern regarding the toxicological effects of plastic additives on humans and aquatic organisms. This study investigated effects of the plastic additive tris(butoxyethyl) phosphate (TBEP) on Cyprinus carpio by measuring concentration distribution of TBEP in the Nanyang Lake estuary, as well as toxic effects of varying doses of TBEP exposure on carp liver. This also included measuring responses of superoxide dismutase (SOD), malondialdehyde (MDA), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and cysteinyl aspartate-specific protease (caspase). Concentrations of TBEP in the polluted water environment (water company inlets, urban sewage pipes, etc.) in the survey area were as high as 76.17-3875.29 μg/L, and 3.12 μg/L in the river flowing through the urban area, and 1.18 μg/L in the estuary of the lake. In the subacute toxicity test, SOD activity in liver tissue with an increase in TBEP concentration was reduced significantly, while the MDA content continued to increase with an increase in TBEP concentration. Inflammatory response factors (TNF-α and IL-1β) and apoptotic proteins (caspase-3 and caspase-9) gradually increased with increasing concentrations of TBEP. Additionally, reduced organelles, increased lipid droplets, swelling of mitochondria, and disorder of mitochondrial cristae structure were observed in liver cells of TBEP-treated carp. Generally, TBEP exposure induced severe oxidative stress in carp liver tissue, resulting in release of inflammatory factors and inflammatory response, mitochondrial structure changes, and the expression of apoptotic proteins. These findings benefit our understanding about the toxicological effects of TBEP in aquatic pollution.

Regional Distribution of Atmospheric Organophosphate Tri-/Diesters in the Pearl River Delta: Possible Emission, Photo-degradation, and Atmospheric Transportation

The regional characteristics of atmospheric organophosphate triesters (OPEs) and organophosphate diesters (Di-OPs) in the Pearl River Delta (PRD) were investigated by passive air samplers mounting quartz fiber filters. The analytes were found on a regional scale. Atmospheric OPEs, semi-quantified using sampling rates of particulate-bonded PAHs, were in the range of 537-2852 pg/m³ in spring and in the range of 106-2055 pg/m³ in summer, with tris(2-chloroethyl)phosphate (TCEP) and tris(2-chloroisopropyl)phosphate as the main components. While atmospheric Di-OPs were semi-quantified using sampling rates of SO₄^2-, in the range of 22.5-5576 pg/m³ in spring and in the range of 66.9-1019 pg/m³ in summer, with di-n-butyl phosphate and diphenyl phosphate (DPHP) being the main Di-OPs. Our results indicated that OPEs were mainly distributed in the central part of the region, which might be ascribed to the distribution of industry related to OPE-containing products. In contrast, Di-OPs were scattered in the PRD, suggesting local emission from their direct industrial application. Significantly lower levels of TCEP, triphenyl phosphate (TPHP), and DPHP were detected in summer than in spring, implying that these compounds might be partitioned off particles as the temperature increased and due to possible photo-transformation of TPHP and DPHP. The results also suggested the long-distance atmospheric transportation potential of Di-OPs.

Organophosphite Antioxidants and Novel Organophosphate Esters in Dust from China: Large-Scale Distribution and Heterogeneous Phototransformation

A large-scale survey was conducted by measuring five organophosphite antioxidants (OPAs) and three novel organophosphate esters (NOPEs) in 139 dust samples across China. The median summed concentrations of OPAs and NOPEs in outdoor dust were 33.8 ng/g (range: 0.12-53,400 ng/g) and 7990 ng/g (2390-27,600 ng/g), respectively. The dust concentrations of OPAs associated with the increasing economic development and population density from western to eastern China, whereas the NOPE concentration in Northeast China (median, 11,900 ng/g; range, 4360-16,400 ng/g) was the highest. Geographically, the distribution of NOPEs was significantly associated with annual sunshine duration and precipitation at each sampling site. Results of laboratory experiments further revealed that the simulated sunlight irradiation promoted the heterogeneous phototransformation of OPAs in dust, and this process was accelerated with the existence of reactive oxygen species and enhanced relative humidity. Importantly, during this phototransformation, the hydroxylated, hydrolyzed, dealkylated, and methylated products, e.g., bis(2,4-di-tert-butylphenyl) methyl phosphate, were identified by nontargeted analysis, part of which were estimated to be more toxic than their parent compounds. The heterogeneous phototransformation pathway of OPAs was suggested accordingly. For the first time, the large-scale distribution of OPAs and NOPEs and the phototransformation of these "new chemicals" in dust were revealed.

Insights into the geographical distribution, bioaccumulation characteristics, and ecological risks of organophosphate esters

Organophosphate esters (OPEs), as flame retardants and plasticizers, have been numerously explored regarding the occurrence and ecotoxicology. Given their toxicity, persistency and bio-accumulative potential, however, they may pose negative effects on ecosystems, regarding which is a growing global concern. Accordingly, the present review systematically analyses the recent literature to (1) elucidate their worldwide distribution, bioaccumulation, and biomagnification potential, (2) determine their interim water quality criteria (i.e., effect thresholds), and (3) preliminarily assess the ecological risks for 32 OPEs in aquatic ecosystems. The results showed that the spatiotemporal distribution of OPEs was geographically specific and closely related to human activities (i.e., megacities), especially halogenated-OPEs. We also found that precipitation of airborne particulates could affect the concentrations of OPEs in soil, and there was a positive correlation between the bioaccumulation and hydrophobicity of OPEs. Tris(2-ethylhexyl) phosphate may exhibit high bioaccumulation in aquatic organisms. A substantial difference was found among interim water quality criteria for OPEs, partly attributable to the variation of their available toxicity data. Tris(phenyl) phosphate (TPHP) and tris(1,3-dichloroisopropyl) phosphate with the lowest predicted no-effect concentration showed the strongest toxicity of growth and reproduction. Through the application of the risk quotient and joint probability curve, TPHP and tris(chloroethyl) phosphate tended to pose moderate risks, which should receive more attention for risk management. Future research should focus on knowledge gaps in the mechanism of biomagnification, derivation of water quality criteria, and more precise assessment of ecological risks for OPEs.

Organophosphate esters in Chinese rice: Occurrence, distribution, and human exposure risks

Dietary intake is a crucial pathway of organophosphate esters (OPEs) exposure for human. However, information about the exposure risk of OPEs via rice consumption is still largely unknown. In the present study, a total of 234 rice samples from 25 provinces or city of China were collected and the concentrations of 24 OPEs were determined. Sixteen OPEs were detected in these rice samples and each rice sample was contaminated with at least 5 OPEs, indicating a ubiquitous occurrence of OPEs in Chinese rice. Moreover, the concentrations of Σ16 OPEs ranged from 1.46 to 552.65 μg/kg dry weight (dw), with a mean value of 64.74 μg/kg dw. For the composition profile of OPEs, three Cl-OPEs, including tris(2-chloroethyl) phosphate (TCEP), tri(2-chloroisopropyl) phosphate (TCIPP) and tris(1,3-dichloro-2-propyl) phosphate (TDCIPP), accounted for the highest proportion of Σ16 OPEs. For the spatial distribution of OPEs, although obvious spatial variations were observed among the 25 provinces or city, no obvious variations were found among the six rice-cultivating regions of China. Additionally, estimated dietary intakes (EDI) values of the 16 OPEs for adults and children were 1105.24 and 1399.13 ng/kg bw/day, respectively, under the high intake scenario. The hazard indexes of the 10 OPEs were 0.108 and 0.137 for adults and children, respectively. The risk assessment results indicated that Chinese adults and children did not suffer significant adverse effects from OPEs via rice intake.

Short and medium-chain chlorinated paraffins in indoor dust from a multistory residential building in Beijing, China: Vertical distribution and potential health risks

In this study, we conducted a preliminary investigation of the vertical distribution and potential health risks of short and medium-chain chlorinated paraffins (SCCPs and MCCPs) in indoor dust from a multistory residential building in Beijing, China. Forty-eight SCCP and MCCP congener groups in dust from different floors of the multistory residential building were determined by two-dimensional gas chromatography coupled with electron capture negative ionization mass spectrometry. The concentration ranges for SCCPs and MCCPs in the dust samples were 0.0239-207 μg/g and 0.135-2903 μg/g, respectively. MCCPs were the dominant group, on average accounting for 76.8 % of ∑CPs. Generally, the concentrations of both SCCPs and MCCPs greatly decreased as the floor level increased, which indicated that the CP contamination was attributed to exogenous atmospheric transport and deposition. C₁₃Cl_7-8 and C₁₄Cl_7-8 were the dominant SCCP and MCCP congener groups, possibly indicating the use of industrial CP-52 products was the main source of CPs. In the worst-case scenario using the maximum concentrations of CPs, the daily intake of SCCPs for toddlers was of the same order of magnitude as the reference dose. It should be noted that CPs exposure may be more serious when indoor decorations, furniture, and various plastic products are taken into consideration. Overall, more attention should be paid to CPs exposure and control measures in high-rise buildings.

Occurrence of organophosphorus esters in outdoor air fine particulate matter and comprehensive assessment of human exposure: A global systematic review

Organophosphate esters (OPEs) are widely used in various industrial items, including plastics, textiles, construction materials, electronics, and auto parts. Several studies have investigated the concentration of OPE compounds in the air, where different compounds have been measured. This systematic review aims to investigate and summarize the relationship between exposure concentrations of OPEs in outdoor air and health risk for different OPE compounds, and correlations between OPE compounds in emission sources. PubMed, Scopus, Embase, Web of Science, and Google Scholar were searched from January 2000 to September 2021 to identify relevant research. The quality of the studies was assessed using the OHAT risk of bias tool. Spearman's correlation and principal component analysis (PCA) were used to analyze the results and correlation between OPE compounds. A total of 7669 manuscripts were found from the search in 5 databases. Finally, 46 studies were included in the systematic review. According to the median concentrations in the studies that were included, Tris(1-chloro-2-propyl) phosphate (TCIPP) (25%), trimethylphenyl phosphate(TMPP) (19%), Tri-iso-butyl phosphate (TiBP) (12%), Triphenyl phosphate (TPHP) (9%) and Tris(2-chloroethyl) phosphate (TCEP) (8%) had the greatest concentrations of OPEs overall. The cumulative contribution of the two main factors, F1 and F2, from the principal component analysis (PCA) results is 49.81%. The EDI value for the compounds is TCEP > TCIPP > TiBP > TMPP > 2-Ethylhexyl diphenyl phosphate (EHDPP) > TPHP > Tri(2-Ethylhexyl) phosphate (TEHP) > Tri-m-cresyl phosphate (mTCP) > Tris(1, 3-dichloro-isopropyl) phosphate (TDCPP) > Tri-n-butyl phosphate (TnBP). The total amount of non-carcinogenic risk (HQ) was for children > infants > adults. The highest value of HQ was for TCEP, TCIPP, and TMPP, respectively. The highest carcinogenic risk value was for TCEP and TMPP.

Triphenyl phosphate proved more potent than its metabolite diphenyl phosphate in inducing hepatic insulin resistance through endoplasmic reticulum stress

Triphenyl phosphate (TPHP) is a widely used flame retardant and plasticizer and has been detected extensively in environmental media, wildlife and human bodies. Several epidemiological and animal studies have revealed that TPHP exposure is positively associated with glucose homeostasis disruption and diabetes. However, the effects of TPHP on hepatic glucose homeostasis and the underlying mechanisms remain unclear. The present work aimed to investigate the cytotoxicity and glucose metabolism disruption of TPHP and its metabolite diphenyl phosphate (DPHP) within hepatocytes. The cell viability assay undertaken on human normal liver (L02) cells showed that TPHP exhibited more potent hepatotoxicity than DPHP. RNA sequencing (RNA-seq) data showed that TPHP and DPHP presented different modes of toxic action. Insulin resistance is one of the predominant toxicities for TPHP, but not for DPHP. The insulin-stimulated glucose uptake and glycogen synthesis were impaired by TPHP, while DPHP exhibited no significant impairment on these factors. TPHP exposure induced endoplasmic reticulum (ER) stress, and the ER stress antagonist 4-PBA restored the impairment of insulin-stimulated glucose uptake and glycogen synthesis induced by TPHP. TPHP could also induce liver ER stress and insulin resistance in mice. Taken together, the results suggested that TPHP induces more potent insulin resistance through ER stress than its metabolite DPHP.

Integrating Physiologically Based Pharmacokinetic Modeling-Based Forward Dosimetry and in Vitro Bioassays to Improve the Risk Assessment of Organophosphate Esters on Human Health

The ability to accurately assess the health risks of contaminants is limited by the shortcomings of toxicological standards. Using organophosphate esters (OPEs) as an example, this study attempted to integrate physiologically based pharmacokinetic (PBPK)-based forward dosimetry and in vitro bioassays to assess the likelihood of contaminants inducing biological effects in humans. The total exposure level of OPEs for Chinese residents was 19.5 ± 8.71 ng/kg/day with inhalation being the main exposure pathway. Then, human PBPK models were developed for individual OPEs to predict their steady-state concentrations in human tissues, and the predicted median levels in blood were close to the measurements. The reference doses (RfDs) of OPEs based on in vitro bioassays were comparable to in vivo animal-derived RfDs, demonstrating the reliability of in vitro bioassays. Therefore, the likelihood of OPEs inducing bioactivities in humans (RQ_in-vitro) was calculated using in vitro toxicity data and OPE levels in human tissues. The RQ_in-vitros of tris(2-chloroisopropyl) phosphate, tris(1,3-dichloropropyl) phosphate, and triphenyl phosphate (7.68 × 10^-5-3.18 × 10^-3) were comparable to the risks assessed using traditional RfDs (5.22 × 10^-5-1.94 × 10^-3), indicating the credibility of the method proposed in this study. This study establishes a new framework to improve the health risk assessment of contaminants without sufficient toxicity data and minimize the need for animal experimentation.

Novel Brominated Flame Retardants in Dust from E-Waste-Dismantling Workplace in Central China: Contamination Status and Human Exposure Assessment

Novel brominated flame retardants (NBFRs) have been widely used as alternatives to legacy BFRs. However, information on the contamination status and human exposure risks of electronic waste (e-waste)-derived NBFRs in the e-waste workplace is limited. In this study, six NBFRs and the legacy BFRs, hexabromocyclododecanes (HBCDs), were analyzed in 50 dust samples from an e-waste-dismantling workplace in Central China. The dust concentration of NBFRs in e-waste-dismantling workshops (median, 157−169 ng/g) was found to be significantly higher than those in an outdoor environment (17.3 ng/g) (p < 0.01). Differently, the highest median concentration of HBCDs was found in dust from the dismantling workshop for cellphones and computers (367 ng/g) among studied areas. The bis(2-ethylhexyl)-3,4,5,6-tetrabromo-phthalate (BEHTBP) was the predominant compound, which contributed 66.0−88.0% of measured NBFR concentrations. NBFRs might originate from plastic and rubber materials in wastes based on the correlation and principal component analysis. Moreover, the total estimated daily intakes (average scenario) of NBFRs were calculated at 2.64 × 10−2 ng/kg bw/d and 2.91× 10−2 ng/kg bw/d for the male and female dismantling workers, respectively, via dust ingestion, inhalation, and dermal contact pathways, which were lower than the reference dose values, and thus indicated a limited human exposure risk for NBFRs at the current level. Although the dust concentrations and daily intakes of NBFRs were still lower than those of other emerging pollutants (e.g., organophosphate and nitrogenous flame retardants) measured in the same sampling set, the elevated levels of NBFRs suggested the progressive BFR replacement process in China, which deserves more attention regarding their adverse effects on both the environment and human health.

Occurrence, correlation, and partitioning of organophosphate esters in soil and tree bark from a megacity, Western China

Concern over the influences of constant addition of emerging anthropogenic chemicals to the environment has become a public issue during the rapid urbanization. Here, we investigated the occurrence of organophosphate esters (OPEs) in soil and corresponding tree bark in a megacity, Western China. Our results showed levels of OPEs in tree bark (1250 ± 573 ng/g dry weight (dw)) were 1-2 orders of magnitude higher than those in soil (40.4 ± 30.8 ng/g dw). Rooster Mountain is a background mountain area, exhibiting significantly lower concentrations of OPEs in soil and tree bark than those in other sites with relatively high population density. This result highlights the effect of human activities on the distribution of OPEs in environmental matrices. Alkyl-OPEs were predominant compounds in soil, whereas halogenated- (Cl-) OPEs were characterized in tree bark. Furthermore, tris(2-chloroethyl) phosphate (TCEP) positively correlated with tris(2-chloroisopropyl) phosphate (TCIPP) in soil (r² = 0.43, P < 0.05) while negatively correlated with TCIPP in tree bark (r² = 0.31, P < 0.05). The ratios of logarithm concentrations of OPEs in tree bark to those in soil correlated well with logK_OA values of OPEs from 6 to 10, indicating the equilibrium status was achieved between OPE partitioning in soil and in tree bark. Nevertheless, tris (2-butoxyethyl) phosphate (TBEP) and tris(2-ethylhexyl) phosphate (TEHP) with high values of logK_OA deviated from this linear tendency, which was possibly due to the fact that they were subjected to the particle-bound deposition process, leading to partition into the soil.

A review on organophosphate esters: Physiochemical properties, applications, and toxicities as well as occurrence and human exposure in dust environment

Organophosphate esters (OPEs) are widely used as flame retardants and plasticizers in the world. The use of OPEs has increased rapidly due to the prohibition of polybrominated diphenyl ethers. However, OPEs are mainly added to various materials by physical mixing, they are therefore easy to be released into the environment through volatilization, leaching, and abrasion during their production, use, transportation, and after disposal. Dust, as an important medium for human exposure to OPEs, has attracted extensive attention. Here, this article reviewed the current knowledge on the physiochemical properties, consumptions and applications, and ecotoxicities of OPEs, also synthesized the available data on the occurrence of 13 OPEs in outdoor and indoor dust environments around the world over the past decade. The results showed that the sum of OPEs (ΣOPEs) was the highest in outdoor dust from an e-waste disposal area in Tianjin of China (range: 1390-42700 ng/g dw; mean: 11500 ng/g dw). The highest ΣOPEs was found in Japan for home dust (range: 9300-11000000 ng/g dw; mean: 266543 ng/g dw), Sweden for office dust (range: 14000-1600000 ng/g dw; mean: 360100 ng/g dw) and daycare center dust (range: 40000-4600000 ng/g dw; mean: 1990800 ng/g dw), and Brazil for car dust (range: 108000-2050000 ng/g dw; mean: 541000 ng/g dw). The use pattern of OPEs differed in different regions and countries. The exposure and risk assessment based on the data of OPEs in home dust indicated that the average daily intakes of OPEs via dust ingestion for children and adults were lower than the corresponding reference doses; and that the current human exposure to OPEs through indoor dust ingestion were not likely to pose risks to human health. Finally, the review pointed out the gaps of current research and provided the directions for further study on OPEs in dust environment.

A scalable field study using leaves as a novel passive air sampler to evaluate the potential source of organophosphate esters in street dust

Organophosphate esters (OPEs) are widely used as flame retardants and plasticizers in industrial and commercial products. It is generally believed that OPEs in street dust mainly originate from road traffic and anthropogenic activities. The influence of atmospheric deposition is still unknown. In this study, leaves were employed as a novel passive air sampler to collect particle matters (PM) in 12 cities in the central province of Henan, China. Similar compositional profiles of OPEs were found in street dust and PM samples. The concentrations of individual OPEs in PM were 1-4 times higher than in street dust. Chlorinated OPEs concentration in PM shows a moderate correlation (r² = 0.538, p < 0.01) with that in street dust. The concentration of alkyl OPEs in PM has a high correlation (r² = 0.843, p < 0.01) with that in street dust. No significant correlation (r² = 0.133, p = 0.132) was found on the aryl OPEs concentrations between street dust and PM. Spearman correlation reveals that the emission sources of tricresyl phosphate (TCrP) and triethyl phosphate (TEP) may be different from other OPEs in dust and PM samples. Principle component analysis (PCA) provides an appropriate explanation that tris (2-chloroethyl) phosphate (TCEP), triphenyl phosphate (TPhP), tris (chloropropyl) phosphate (TCPP), tributyl phosphate (TnBP), and TEP in street dust and PM may be emitted from the same sources, suggesting that PM has a significant influence on the occurrence of OPEs in street dust. The estimated dry deposition fluxes of particle-bound OPEs show a significant correlation (R² = 0.969, p < 0.01) with OPEs concentrations in street dust, revealing that the input of atmospheric deposition could be a major source of OPEs in street dust.

Occurrence, spatial variation, seasonal difference, and ecological risk assessment of organophosphate esters in the Yangtze River, China: From the upper to lower reaches

A comprehensive contamination profile of organophosphate esters (OPEs) in the Yangtze River in China has not yet been characterized. In this study, we investigated the occurrence, spatial variation, and seasonal difference of 18 selected OPEs in surface water samples of the Yangtze River mainstream. To characterize the contamination profile of the OPEs, we collected 144 Yangtze River water samples from 72 sampling sites in December 2020 and June 2021. Four alkyl-OPEs [trimethyl phosphate, triethyl phosphate (TEP), tributyl phosphate, and tris(2-butoxyethyl) phosphate (TBOEP)] and three halogenated OPEs [tris(2-chloroethyl) phosphate (TCEP), tris(1-chloro-2-propyl) phosphate (TCIPP), and tris(1,3-dichloro-2-propyl) phosphate] were the most frequently detected target compounds (>95%). TCIPP (median: 34.6 ng/L), TEP (median: 26.2 ng/L), and TCEP (median: 17.9 ng/L) were the most abundant compounds, while the median values of the others were below 10 ng/L. Additionally, the concentrations of most OPEs gradually/dramatically increased from upstream to downstream Yangtze River. Notably, the median concentration of summed OPEs in Shanghai (415 ng/L; downstream) was approximately ten times higher than that in Qinghai (45.7 ng/L; upstream). Urban sampling sites had significantly or slightly higher concentrations of most OPEs than rural sampling sites. Moreover, the OPE concentrations in the river water differed between the winter and summer. The concentrations of summed OPEs (median: 117 vs. 106 ng/L), summed alkyl-OPEs (67.0 vs. 45.8 ng/L; p < 0.05), and summed aryl-OPEs (0.48 vs. 0.17 ng/L; p < 0.05) were slightly or significantly higher in December than those in June; nevertheless, summed halogenated OPEs were slightly higher in June (62.2 vs. 50.2 ng/L) than that in December. Compared with previously reported data for OPEs in other major rivers worldwide, the Yangtze River water had relatively lower concentrations of the OPEs than those in the rivers of developed countries and regions. Ecological risk assessment suggested that tris(2-ethylhexyl) phosphate and TCEP posed relatively high risks (RQ: 1.01 and 0.98, respectively) at the maximum concentration, and TBOEP posed a moderate risk (RQ: 0.25). This is the first study to comprehensively characterize the contamination profile of the Yangtze River by the OPEs.

Distribution of flame retardants among indoor dust, airborne particles and vapour phase from Beijing: spatial-temporal variation and human exposure characteristics

The occurrence and distribution of 10 brominated flame retardants (BFRs) and 10 organophosphate flame retardants (OPFRs) were investigated in indoor dust, total suspended particles (TSP), and vapour phase from offices (n = 10), homes (n = 9), and day-care centres (n = 10) in Beijing, China. Three types of samples were collected biweekly from one office and one home over a year to examine temporal trends. BFRs in dust significantly correlated with those in TSP, while OPFRs significantly correlated among all three matrices. In addition, BFRs in dust (ng/g) and TSP (pg/m³) exhibited similar temporal trends with higher levels in the cold season, whereas OPFRs in TSP and vapour phase (pg/m³) showed similar temporal trends with higher levels in the warm season. The geometric mean concentrations of BFRs and OPFRs in the three matrices from the above mentioned three types of indoor microenvironments were used for exposure and health risk estimation, and ∑₇OPFRs showed much higher hazard index (HI) values than ∑₁₀BFRs for all subpopulations, and inhalation of OPFRs was a major risk source. With the volatility of flame retardants (FRs) decreasing, the contribution of dust ingestion and dermal absorption showed an increasing trend, and the contribution of inhalation exhibited a gradual decreasing trend, which implied the dominant exposure pathway to FRs is strongly related to the vapour pressure (25 °C, Pa) of these substances. Using a single type of microenvironment or the collection of samples at a single point in time can lead to overestimation or underestimation of overall exposure and risk for people to some extent. The correlations of FRs in dust, TSP, and vapour phase from indoor microenvironments, as well as their temporal trends were first reported in this study, which will provide a basis for more accurate FR exposure assessments in the future.

The associations between renal disease severity and exposure to organophosphate flame retardants in patients with chronic kidney disease

Organophosphate flame retardants (OPFRs) are emerging and widespread environmental pollutants with potential health hazards, including nephrotoxicity. However, the exposure patterns and nephrotoxic potential of OPFRs are yet to be investigated in patients with chronic kidney disease (CKD). We conducted a cross-sectional study involving 166 patients with CKD stratified by estimated glomerular filtration rate (eGFR) and severity of proteinuria. The urinary concentrations of 10 OPFR compounds were measured to evaluate the exposure patterns. Clinical and urinary OPFR profiles were compared among subgroups to identify whether the OPFR compounds were independently correlated with eGFR and proteinuria. Additionally, lifestyle factors were compared among subgroups stratified by median concentrations of urinary OPFR compounds associated with renal disease severity. This study revealed universal exposure to OPFRs in the CKD population, with an overall urinary detection rate of 98.80 %. Furthermore, after adjusting for covariates, the urinary concentration of bis(2-chloroethyl) phosphate (BCEP) was identified as an independent predictor of lower eGFR (low vs high eGFR, odds ratio (OR) (95 % confidence interval (CI)), 1.761 (1.032-3.005) per log μg/g creatinine, p = 0.038), and the urinary concentration of bis(2-butoxyethyl) phosphate (BBOEP) was independently correlated with overt proteinuria in CKD patients (with vs without overt proteinuria, OR (95 % CI), 1.813 (1.065-3.086) per log μg/g creatinine, p = 0.028). Moreover, frequent seafood consumption was negatively correlated with urinary BCEP concentration (high vs low BCEP, OR (95 % CI), 0.455 (0.228-0.908), p = 0.025), and age was inversely associated with urinary BBOEP concentration (high vs low BBOEP, OR (95 % CI), 0.968 (0.937-0.999) per year, p = 0.048). In conclusion, our investigation highlights the extensive exposure to OPFRs and the independent association between renal disease severity and urinary BCEP/BBOEP concentrations in the CKD population, indicating the nephrotoxic potential of these pollutants.

Organophosphate flame retardants in Hangzhou tap water system: Occurrence, distribution, and exposure risk assessment

The usage of Organophosphorus flame retardants (OPFRs) is gradually increased as the ban on brominated flame retardants (BFRs) worldwide. The frequent accessibility of OPFRs in aquatic environment poses potential risk to human. Previous studies have concerned on surface water, while studies on tap water are limited. In this research, we aim to evaluate the removal efficiency of the tap water treatment process and investigate the exposure risk of OPFRs in tap water. Herein, we collected 14 samples from water source, 10 samples from water treatment plants and 47 from tap to analyze the concentrations and removal efficiency of OPFRs in Hangzhou tap water supply system. The results showed the concentrations of ∑OPFRs ranged from 9.25 to 224.74 ng/L in all samples, with Tris(1-chloro-2-propyl) Phosphate (TCPP), Tris(2-chloroethyl) phosphate (TCEP), Triphenyl phosphate (TPHP), and Tributyl phosphate (TBP) being the predominant compounds. Levels of the OPFRs had a 10.0 % - 50.4 % declination when compared samples after treatment with that before. The maximum exposure doses of ∑OPFRs via tap water for both adults and children were much lower than the reference dose (RfD). As a result, the hazard index (HI) and the carcinogenic risk (CR) pinpointed a negligible non-carcinogenic and carcinogenic risk for the residents. Even so, given the pervasive usage of OPFRs, the residual levels and the potential risk of OPFRs in watershed should be continuously concerned.

An overview of organophosphate esters and their metabolites in humans: Analytical methods, occurrence, and biomonitoring

With the strict regulation of brominated flame retardants, organophosphate esters (OPEs) have been extensively used as replacements. Increasing concerns on OPEs have aroused due to their extensive distribution in the environment and humans, as well as their potential toxicities. Recent studies have demonstrated that some organophosphate di-esters are even more toxic than their respective tri-esters. This review summarized the current state of knowledge on the analytical methodologies (including sample collection and preparation, instrumental analysis, and the feasibility of each potential human matrix), as well as the occurrences of OPEs and/or their metabolites (m-OPEs) in various human matrices. Organophosphate esters are readily metabolized in human thus only limited studies reported their occurrences in blood and breast milk, whereas abundant studies are available regarding the occurrences of m-OPEs rather than OPEs in urine. Since none of the matrix is suitable all the time, appropriate matrix should be selected depending on the aims of biomonitoring studies, e.g., high throughput screening or body burden estimation. Biomonitoring with non-invasive matrices such as hair and/or nail is useful to screen specific populations that might be under high exposure risks while urine is more suitable to provide valuable information on body burden. In terms of urinary monitoring, specific biomarkers have been identified for some OPE compounds, including tri(2-butoxyethyl) phosphate, tri(1,3-dichloro-2-propyl) phosphate, tri(2-chloroethyl) phosphate and tri(1-chloro-2-propyl) phosphate. Further studies are required to identify suitable urinary biomarkers for other OPE compounds, especially the emerging ones.

Organophosphate tri-esters and di-esters in drinking water and surface water from the Pearl River Delta, South China: Implications for human exposure

Some organophosphate di-esters (di-OPEs) have been found to be more toxic than their respective tri-esters. The environmental occurrence of di-OPEs remains largely unclear. A total of 106 water samples, including 56 drinking water (bottled, barreled, and tap water) and 50 surface water (lake and river) samples were collected and analyzed for 10 organophosphate tri-esters (tri-OPEs) and 7 di-OPEs. The concentrations (range (median)) of ∑₇di-OPE were 2.8-22 (9.7), 1.1-5.8 (2.6), 3.7-250 (120), 13-410 (220), and 92-930 (210) ng/L in bottled water, barreled water, tap water, lake water, and river water, respectively. In all types of water samples, tris(1-chloro-2-propyl) phosphate was the dominant tri-OPE compound. Diphenyl phosphate was the predominant di-OPE compound in tap water and surface water, while di-n-butyl phosphate and bis(2-ethylhexyl) phosphate was the dominant compound in bottled water and barreled water, respectively. Source analysis suggested diverse sources of di-OPEs, including industrial applications, effluents of municipal wastewater treatment plants, degradation from tri-OPEs during production/usage and under natural environmental conditions. The non-carcinogenic and carcinogenic risks of OPEs were lower than the theoretical threshold of risk, indicating the human health risks to OPEs via drinking water consumption were negligible. More studies are needed to explore environmental behaviors of di-OPEs in the aquatic environment and to investigate ecological risks.

Spatial distribution and risk assessment of 11 organophosphate flame retardants in soils from different regions of agricultural farmlands in mainland China

The occurrence and distribution of organophosphate flame retardants (OPFRs) in nationwide farmland soils of mainland China are rarely measured. The current study was the first to collect 325 farmland soil samples from 109 cities throughout mainland China. Ten organophosphate esters (OPEs), including alkyl-OPEs, Cl-OPEs, and aryl-OPEs, together with an organophosphate intermediates (TPPO), were determined. The results indicated that ΣOPFRs ranged from 2.41 ng/g to 35.8 ng/g dry weight (dw), and ΣOPFRs in northeastern and southern China were significantly (p < 0.01) higher than those in northwestern and central China. Alkyl-OPEs and Cl-OPEs served as the main components of OPEs, and the novel aryl-OPEs showed the highest detection frequency (> 92 %). Principal component analysis (PCA) was employed to identify the different sources of OPEs, in which atmospheric deposition, irrigation, or direct release of plastic mulch acted as the main input routes in farmland soils. The potential risks of OPFRs were assessed through soil ingestion exposure and ecotoxicological impacts. Our results showed that direct exposure to farmland soils had no high risks to the human body and ecological environments. This study provides new evidence for further understanding the spatial distributions and contamination status of OPFRs in farmland soils throughout mainland China.