Traditional and emerging organophosphate esters (OPEs) in indoor dust of Nanjing, eastern China: Occurrence, human exposure, and risk assessment

Adverse Effects of Aryl Organophosphate Esters on Reproduction

Aryl organophosphate esters (AOPEs) have been widely detected in environmental media and human samples, and increasing evidence shows that AOPEs induce adverse effects on reproductive health. This Review summarizes the exposure levels, reproductive toxicity data, and underlying mechanisms of three legacy AOPEs, including triphenyl phosphate (TPHP), 2-ethylhexyl diphenyl phosphate (EHDPP), and tricresyl phosphate (TCrP). Reproduction-related nuclear receptors (RrNRs) were concluded to play important roles in the reproductive toxicity induced by AOPEs, as all three typical AOPEs and their hydroxylated metabolites elicit binding affinity to RrNRs. We further investigated the RrNRs binding ability of the other 55 emerging AOPEs (eAOPEs) through molecular docking and found most eAOPEs (54/55) showed potential binding ability to RrNRs, especially to estrogen receptor α. This Review helped us to comprehensively understand the adverse effects of AOPEs on reproduction and predict the potential health risk of eAOPEs. AOPEs are easily metabolized in organisms, and their hydroxylated metabolites even show more potency to bind RrRNs. This Review also highlights the necessity to take the contribution of hydroxylated metabolites into account in future research.

Estrogenic and anti-estrogenic assessment of the flame retardant, 2-ethylhexyl diphenyl phosphate (EHDPP), and its metabolites: Evidence from in vitro, in silico, and transcriptome studies

2-Ethylhexyl diphenyl phosphate (EHDPP) is a replacement flame-retardant commonly found in several environmental matrices and human biospecimens. Although some adverse effects of EHDPP have been identified, the endocrine-disrupting effects of EHDPP and its key metabolites on the human estrogen receptor (ER) are largely unknown. Herein, we report for the first time that EHDPP, at concentrations found in the environment and humans, significantly promoted estrogenic activity and synergized with 17β-estradiol-induced ER transactivation. However, two major EHDPP metabolites 2-ethyl-3-hydroxyhexyl diphenyl phosphate (3-OH-EHDPP) and 2-ethyl-5-hydroxyhexyl diphenyl phosphate (5-OH-EHDPP), inhibited the ER through a non-competitive binding mechanism. Molecular docking showed that Pi-Pi stacking, hydrogen, and hydrophobic bonds primarily stabilize intermolecular interactions between EHDPP and the binding pockets of human ERα and ERβ. Moreover, transcriptome analysis confirmed the estrogenic effects of EHDPP, revealing notable enrichments in ER-mediated signaling and breast cancer pathways, consistent with the validated estrogenic gene expression profile. Intriguingly, EHDPP markedly promoted the clonogenic growth of two ER+ breast cancer cell lines, corroborating the expression levels of ERα protein. Our findings indicate that the common flame-retardant EHDPP activates the ER and downstream signaling, providing far-reaching implications for environmental and health risks associated with estrogen-related adversities such as the development of ER+ breast cancer.

Legacy and emerging organophosphate flame retardants (OPFRs) in water and sediment from the Pearl River Delta to the adjacent coastal waters of the South China Sea: Spatioseasonal variations, flux estimation and ecological risk

The industrialization and urbanization along the Pearl River Delta (PRD) have exacerbated the issue of pollution in aquatic environments by organophosphate flame retardants (OPFRs). Historical cumulative pollution from legacy OPFRs, combined with newly emerging OPFRs, has increased the severity and complexity of OPFR pollution in this region. We explored the contamination profile, input flux and risk of legacy and emerging OPFRs in surface waters and in sediment samples of the PRD. The results indicated that all OPFRs we targeted were detectable in the water samples; The sum concentration of OPFRs in the water ranged from 17.35 ng/L to 673.30 ng/L, with an average level of 215.11 ng/L; In sediments it ranged from 5.68 ng/g to 802.46 ng/g dry weight (dw). Tris(2-chloroisopropyl) phosphate (TCPP, 99.58 ng/L) and Bisphenol A diphenyl phosphate (BDP, 51.09 ng/g dw) were the most abundant OPFRs in the surface water and sediment, respectively. Notably, although Tetrekis (2-chlorethyl) dichloroisopentyl-diphosphate (V6) has only been used in recent years, its relatively high concentrations and proportions, both in water and sediment samples, demonstrate its now widespread occurrence in the PRD. The estimated annual flux of ΣOPFRs from the eight estuaries to the South China Sea was 45.04 t/y. The four estuaries (Humen, Modaomen, Hengmen and Honqimen) contribute 80% of the mass loading. Triphenyl phosphate (TPHP) and Tris (2-chloroethyl) phosphate (TCEP) in water posed relatively higher ecological risks to algae, daphnia, and fish than other OPFRs. Our results provide scientific support for continuing monitoring and control of OPFR pollution in the PRD.

Affecting factors and health risks of organophosphate esters in urban soil and surface dust in a typical river valley city based on local bivariate Moran's I and Monte-Carlo simulation

A total of 102 urban soil and surface dust samples were collected from Lanzhou of China to clarify the occurrences, sources, affecting factors, and health risks of 13 organophosphate esters (OPEs). The total concentration of 13 OPEs (Ʃ13OPEs) in urban soil and surface dust ranged from 80.1 to 749 and 244 to 4905 ng/g, dominated by chlorinated OPEs (39.9 % and 65.1 %). The Ʃ13OPEs in the two media was higher in the central and eastern of Lanzhou due to local topography and wind direction. OPEs in the two media originated from industrial, traffic and commercial activities (37-53.4 %), atmospheric depositions (24.3-31.3 %), and OPEs-containing material emissions (14.5-31.7 %). Transport station number, residential/commercial area distribution, and road length were positively correlated with Ʃ13OPEs in the two media, suggesting that traffic activities are the main factors influencing the distribution of OPEs. Probabilistic non-cancer (< 1) and cancer (< 1 × 10-6) risks of human exposed to OPEs were low, mainly attributed to OPEs-containing material emissions (47.5-62.0 %) in urban soil and industrial/traffic activities (57.8-92.2 %) in surface dust. Reducing the frequency of human exposed to the two media and controlling the release of OPEs from pollution sources may mitigate population exposure risks.

Organophosphate Esters and Polybrominated Diphenyl Ethers in Vehicle Dust: Concentrations, Sources, and Health Risk Assessment

BACKGROUND

The primary flame retardants in vehicles, organophosphates (OPEs) and polybrominated diphenyl ethers (PBDEs), volatilize and accumulate in the enclosed vehicle environment, posing potential health risks. Amidst the rising number of vehicles, the scrutiny of persistent organic pollutants like OPEs and PBDEs in vehicles is increasing. This study investigates occupational and nonoccupational population exposure to specific OPEs (TnBP, TBOEP, TEHP, TCEP, TCiPP, TDCiPP, TPhP, EHDPP) and PBDEs (BDE-28, BDE-47, BDE-99, BDE-100, BDE-153, BDE-154, BDE-183, BDE-209) in vehicle dust.

METHODS

Data on OPEs and PBDEs in vehicle dust were sourced from PubMed and Web of Science. We applied PCA and PMF to identify pollutant sources and assessed health risks using the hazard index (HI) and carcinogenic risk (CR) methods. Monte Carlo simulations were conducted for uncertainty analysis, evaluating variable contributions to the results.

RESULTS

The predominant OPE in dust samples was TDCiPP (mean value: 4.34 × 104 ng g-1), and the main PBDE was BDE-209 (mean value: 1.52 × 104 ng g-1). Potential sources of OPEs in vehicle dust include polyvinyl chloride (PVC) upholstery, polyurethane foam (PUF) seats, electronics, carpet wear, hydraulic oil, and plastic wear in the brake system. PBDE sources likely include automotive parts, PVC upholstery, seats, carpets, and electronics. The 90th percentile HI and CR values for occupational and nonoccupational populations exposed to OPEs and PBDEs indicate that the noncarcinogenic and carcinogenic risks are relatively low. A sensitivity analysis showed that the pollutant concentration, time in the vehicle, exposure frequency, and duration significantly influence health risks.

CONCLUSIONS

The health risks to both occupational and nonoccupational populations from exposure to OPEs and PBDEs in vehicle dust are relatively low.

A comprehensive evaluation of the endocrine-disrupting effects of emerging organophosphate esters

The ubiquitous presence of organophosphate esters (OPEs) in the environment has prompted growing concerns about their potential health risks, particularly their endocrine-disrupting effects. This study comprehensively evaluated the endocrine-disrupting properties of six emerging OPEs: five aryl-OPEs (2-ethylhexyl diphenyl phosphate (EHDPP), tris (2-biphenylyl) phosphate (TBPP), resorcinol bis (diphenyl phosphate) (RDP), 4-hydroxyphenyl diphenyl phosphate (para-OH-TPHP), and 3-hydroxyphenyl diphenyl phosphate (meta-OH-TPHP) and one alkyl-OPE, triallyl phosphate (TAP). Our findings revealed that all tested aryl-OPEs exhibited antagonistic effects on one or more hormone receptors. Importantly, para-OH-TPHP demonstrated the most potent antagonistic activity, inhibiting estrogen receptor α (ERα), thyroid hormone receptor β (TRβ), glucocorticoid receptor (GR), and mineralocorticoid receptor (MR) with the concentration of test compounds showing 20 % relative inhibitory concentration (RIC20) value below 10-6 mol/L (M). RDP antagonized ERα and cortical receptors (GR and MR), TBPP affected TRβ and GR, while EHDPP and meta-OH-TPHP targeted MR. Regarding steroidogenesis, para-OH-TPHP significantly inhibited genes for estrogen (cyp19) and cortisol synthesis (cyp11b2), and along with meta-OH-TPHP, EHDPP, TAP, and RDP downregulated cyp11a1, a rate-limiting enzyme in hormone synthesis. All compounds caused malformations and swimming abnormalities in zebrafish embryos/larvae at concentrations of 10-7 M or higher, with para-OH-TPHP showing nearly 50 % peak induction. Furthermore, the six compounds tested influenced genes associated with the hypothalamic-pituitary-gonadal (HPG) axis in both zebrafish larvae and adult female zebrafish, in addition to affecting the reproductive behavior of zebrafish. A weighted scoring system was employed to rank the endocrine-disrupting potency of the OPEs, with para-OH-TPHP exhibiting the highest risk, followed by EHDPP, RDP, TBPP, meta-OH-TPHP, and TAP. Collectively, our results highlight the significant endocrine-disrupting effects of emerging OPEs, underscoring the urgent need for further research to assess their potential health implications.

A comparative study on contamination profiles of liquid crystal monomers (LCMs) between outdoor and indoor dusts, and the assessment of health risk of human exposure

Liquid crystal monomers (LCMs) are ubiquitous in various environmental samples, which has led to increasing concerns regarding their potential health risks to humans and wildlife. However, the comparison of the contamination patterns of LCMs between indoor and outdoor environments has rarely been studied. In this study, 35 LCMs were investigated in n = 55 dust samples collected from indoor (n = 20) and outdoor (n = 35) spaces in Yulin, Northwest China. The LCMs were widely detected in indoor and outdoor dusts; the total concentrations of LCMs ranged from 48.6 to 396 ng/g (median: 153 ng/g), and from not detectable to 388 ng/g (median: 56.4 ng/g) in indoor and outdoor dusts, respectively. The concentration levels of ΣLCMs in indoor dusts were significantly higher than those in outdoor dusts (p < 0.05). For each microenvironment, the ranking order of LCM concentrations was dormitory (mean: 202 ng/g) > teaching building (182 ng/g) > campus road (150 ng/g) > urban road (107 ng/g) > laboratory building (91.0 ng/g) > pedestrian street (20.1 ng/g). The mean estimated daily intake values of Σ35LCMs for adults were 2.48 × 10-2 and 1.37 × 10-3 ng/g BW/day in indoor and outdoor dusts, respectively. The hazard quotients of individual LCMs and hazard indices of all analytes were considerably less than one, indicating little health risk for humans via dust ingestion.

Mechanistic insights into cadmium exacerbating 2-Ethylhexyl diphenyl phosphate-induced human keratinocyte toxicity: Oxidative damage, cell apoptosis, and tight junction disruption

Organophosphate flame retardants 2-ethylhexyldiphenyl phosphate (EHDPP) and cadmium (Cd) are ubiquitous in environmental matrices, and dermal absorption is a major human exposure pathway. However, their detrimental effects on the human epidermis remain largely unknown. In this study, human keratinocytes (HaCaT cells) were employed to examine the toxicity and underlying mechanisms of co-exposure to EHDPP and Cd. Their influence on cell morphology and viability, oxidative damage, apoptosis, and tight junction were determined. The results showed that co-exposure decreased cell viability by >40 %, induced a higher level of oxidative damage by increasing the generation of reactive oxygen species (1.3 folds) and inhibited CAT (79 %) and GPX (90 %) activities. Moreover, Cd exacerbated EHDPP-induced mitochondrial disorder and cellular apoptosis, which was evidenced by a reduction in mitochondrial membrane potential and an elevation of cyt-c and Caspase-3 mRNA expression. In addition, greater loss of ZO-1 immunoreactivity at cellular boundaries was observed after co-exposure, indicating skin epithelial barrier function disruption, which may increase the human bioavailability of contaminants via the dermal absorption pathway. Taken together, oxidative damage, cell apoptosis, and tight junction disruption played a crucial role in EHDPP + Cd triggered cytotoxicity in HaCaT cells. The detrimental effects of EHDPP + Cd co-exposure were greater than individual exposure, suggesting the current health risk assessment or adverse effects evaluation of individual exposure may underestimate their perniciousness. Our data imply the importance of considering the combined exposure to accurately assess their health implication.

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.

Effects of organophosphorus flame retardant EHDPP on mouse retinal photoreceptor cells: Oxidative stress, apoptosis, and proinflammatory response

2-Ethylhexyl diphenyl phosphate (EHDPP) is a frequently utilized organophosphorus flame retardant (OPFR) and has been extensively detected in environmental media. Prolonged daily exposure to EHDPP has been linked to potential retinal damage, yet the adverse impacts on the retina are still generally underexplored. In this research, we explored oxidative stress, inflammation, and the activating mechanisms initiated by EHDPP in mouse retinal photoreceptor (661 W) cells following a 24 h exposure period. Our research demonstrated that EHDPP led to a decline in cell viability that was directly proportional to its concentration, with the median lethal concentration (LC50) being 88 µM. Furthermore, EHDPP was found to elevate intracellular and mitochondrial levels of reactive oxygen species (ROS), trigger apoptosis, induce cell cycle arrest at the G1 phase, and modulate the expression of both antioxidant enzymes (Nrf2, HO-1, and CAT) and pro-inflammatory mediators (TNF-α, IL-1β, and IL-6) within 661 W cells. These findings indicate that retinal damage triggered by EHDPP exposure could be mediated via the Nrf2/HO-1 signaling pathway in these cells. Collectively, our investigation revealed that oxidative stress induced by EHDPP is likely a critical factor in the cytotoxic response of 661 W cells, potentially leading to damage in retinal photoreceptor cells.

Organophosphate esters in human serum: a relatively simple and efficient liquid chromatography-mass spectrometry method

Organophosphate esters (OPEs) are widely used as flame retardants and plasticizers, which are of growing concern due to their endocrine-disrupting effects, developmental toxicity, and potential carcinogenicity. However, data on human exposure to OPEs is still scarce. In this study, a relatively simple and efficient method with less serum consumption for the detection of OPEs in human serum was developed and validated. Nine OPEs in 200 μL of human serum were extracted by an acetonitrile-formic acid system and analyzed using ultra-high-performance liquid chromatography-quadrupole tandem time-of-flight high-resolution mass spectrometry. Several experiments were conducted to optimize the chromatographic and mass spectrometric conditions as well as sample preparation to obtain a more sensitive and efficient analytical protocol. The proposed method was examined in terms of its linearity, accuracy, precision, detection limit, and matrix effect. The matrix-spiked recoveries of the target OPEs ranged from 83.3% to 111.1%, with relative standard deviations between 2.7% and 16.6%. The detection limits were within (0.002 to 0.029) ng mL-1, while the quantification limits were within (0.007 to 0.098) ng mL-1. The internal standard-corrected matrix effects varied from 82.7% to 113.9%. Finally, the method was applied to detect OPEs in actual human serum samples. All nine OPEs were detected in 269 serum samples to varying degrees, with the average concentrations ranging from (0.08 to 1.77) ng mL-1. After validation, the method was found to be simple in pretreatment, high in sensitivity, good in practicality, and suitable for exposure evaluation of OPEs in populations.

Exposure to resorcinol bis (diphenyl phosphate) induces colonization of alien microorganisms with potential impacts on the gut microbiota and metabolic disruption in male zebrafish

Organophosphate esters (OPEs) have been demonstrated to induce various forms of toxicity in aquatic organisms. However, a scarcity of evidence impedes the conclusive determination of whether OPEs manifest sex-dependent toxic effects. Here, we investigated the effects of tris (1-chloro-2-propyl) phosphate (TCPP) and resorcinol bis (diphenyl phosphate) (RDP) on the intestines of both female and male zebrafish. The results indicated that, in comparison to TCPP, RDP induced more pronounced intestinal microstructural damage and oxidative stress, particularly in male zebrafish. 16S rRNA sequencing and metabolomics revealed significant alterations in the species richness and oxidative stress-related metabolites in the intestinal microbiota of zebrafish under exposure to both TCPP and RDP, manifesting gender-specific effects. Based on differential species analysis, we defined invasive species and applied invasion theory to analyze the reasons for changes in the male fish intestinal community. Correlation analysis demonstrated that alien species may have potential effects on metabolism. Overall, this study reveals a pronounced gender-dependent impact on both the intestinal microbiota and metabolic disruptions of zebrafish due to OPEs exposure and offers a novel perspective on the influence of pollutants on intestinal microbial communities and metabolism.

A new approach to monitoring typical organophosphorus compounds (OPs) in environmental media: From database building to suspect screening

Organophosphorus compounds (OPs) are widely used as flame retardants (FRs) and plasticizers, yet strategies for comprehensively screening of suspect OPs in environmental samples are still lacking. In this work, a neoteric, robust, and general suspect screening technique was developed to identify novel chemical exposures by use of ultra-high performance liquid chromatography-Q Exactive hybrid quadrupole-Orbitrap high resolution mass spectrometry (UHPLC-Q-Orbitrap HRMS). We firstly established a suspect chemical database which had 7,922 OPs with 4,686 molecular formulas, and then conducted suspect screening in n = 50 indoor dust samples, n = 76 sediment samples, and n = 111 water samples. By use of scoring criteria such as retention time prediction models, we successfully confirmed five compounds by comparison with their authentic standards, and prioritized three OPs candidates including a nitrogen/fluorine-containing compound, that is dimethyl {1H-indol-3-yl[3-(trifluoromethyl)anilino]methyl} phosphonate (DMITFMAMP). Given that the biodegradation half-life values in water (t1/2,w) of DMITFMAMP calculated by EPI Suite is 180 d, it is considered to be potentially persistent. This strategy shows promising potential in environmental pollution assessment, and can be expected to be widely used in future research.

Factors impacting human exposure to legacy and emerging contaminants in residential dust in Beijing, China: Characteristics of indoor microenvironment

Exposure to indoor dust is of concern since dust may be contaminated by various toxic chemicals and people spend considerable time indoors. Factors impacting human exposure risks to contaminants in indoor dust may differ from those affecting the loadings of contaminants, but the dominant factors have not yet been well clarified. In this study, the occurrence, human exposure, and related influencing factors of several classes of legacy and emerging contaminants in residential dust across Beijing were investigated, including per- and polyfluoroalkyl substances (PFASs) and three types of flame retardants (FRs), i.e., organophosphate esters (OPEs), polybrominated diphenyl ethers (PBDEs), and novel halogenated FRs (NHFRs). OPEs (median: 3847 ng/g) were the most abundant group, followed by PBDEs (1046 ng/g) and NHFRs (520 ng/g). PFASs (14.3 ng/g) were one to two orders of magnitude lower than FRs. The estimated daily intakes of these contaminants were relatively higher for toddlers than other age groups, with oral ingestion being the main exposure pathway compared with dermal contact. Higher human exposure risks were found in new buildings or newly finished homes due to the elevated intake of emerging contaminants (such as OPEs). Furthermore, higher risks were also found in homes with wooden floors, which were mainly associated with higher levels of PFASs, chloroalkyl and alkyl OPEs, compared with tile floors. Citizens in the urban area also showed higher exposure risks than those in the suburban area. The quantity of household appliances and finishing styles (simple or luxurious) showed an insignificant impact on overall human exposure risks despite their significant effect on the levels of some of the dust contaminants. Results in this study are of importance in understanding human exposure to the co-existence of multiple contaminants in indoor dust.

Investigation of the Role of Distances from Liquid Crystal Monomer (LCM) Factories on Distribution of LCMs in Surface Soil Samples

Liquid crystal monomers (LCMs), which are commonly used in electronic device screens, have attracted attention as a potential class of emerging organic pollutants with persistent, bioaccumulative, and toxic (PBT) properties. This study involved the collection of 54 surface soil samples around one LC industrial park at increasing spatial distances within 1 km, 1-3 km, and 3-5 km from the center of the LC industrial park. Our observations revealed the presence of LCMs in 46 of 54 surface soil samples examined. Of the 39 target LCMs, 36 were identified, comprising 14 non-fluorinated and 22 fluorinated LCMs. Nine LCMs were detected at frequencies exceeding 50%, with 3bcHdFB exhibiting the highest detection frequency of 59% in the soil samples. The total LCM concentrations across the 46 sampling locations varied from 0.0072 to 17.24 ng/g dw, with the highest total concentrations at sampling sites within 1 km of the liquid crystal plant, suggesting that manufacturing processes may be a potential source for LCM release into the environment. Differences were observed in the LCM contamination patterns among the three sampling areas. Additionally, we observed a decrease in the median LCM concentration with increasing distance from the center of the LC industrial park. However, no statistically significant differences (p > 0.05) in LCM concentrations were observed across the three distances assessed in this study. This may be owing to the limited variety of target compounds analyzed and the limited number of soil samples. Our results emphasize that further studies on the emissions and pollution characteristics of LCMs during production are warranted.

Global Trends and Hotspots in Research on the Health Risks of Organophosphate Flame Retardants: A Bibliometric and Visual Analysis

BACKGROUND

Organophosphate flame retardants (OPFRs) are compounds with a wide range of industrial and commercial applications and are mainly used as flame retardants and plasticizers. The global consumption of OPFRs has risen rapidly in recent decades, and they have been widely detected in environmental media. Unfortunately, OPFRs have been associated with many adverse health outcomes. The issue of the health risks of OPFRs is attracting increasing attention. Therefore, there is a need to review the current state of research and trends in this field to help researchers and policymakers quickly understand the field, identify new research directions, and allocate appropriate resources for further development of the OPFR health risk research field.

METHODS

This study statistically analyzed 1162 relevant publications included in the Web of Science Core Collection from 2003-2023. The internal and external features of the literature, such as publication trends, countries, authors, journals, and keywords, were quantitatively analyzed and visually presented to identify the research hotspots, compositions, and paradigms of the field and to horizontally and vertically analyze the development trends and structural evolution of the field.

RESULTS

The development of the field can be divided into three stages, and the field entered a period of rapid development in 2016. China (649 papers) is the most prolific country, followed by the United States (188 papers). The authors STAPLETON HM and WANG Y have the highest combined impact. International collaboration between countries and researchers still needs to be strengthened. Science of The Total Environment is the most frequently published journal (162 papers), and Environmental Science and Technology is the most frequently cited journal (5285 citations). Endocrine disruption, developmental toxicity, and neurotoxicity are the health effects of greatest interest.

CONCLUSIONS

Future research is expected to be multidisciplinary, and research hotspots may involve a comprehensive assessment of OPFR exposure in the population, exploration of the mechanisms of endocrine-disrupting effects and in vivo metabolic processes, and examination of the health effects of OPFR metabolites.

Distribution and Risk Assessment of Organophosphate Esters in Agricultural Soils and Plants in the Coastal Areas of South China

Organophosphate esters (OPEs) are frequently used as flame retardants and plasticizers in various commercial products. While initially considered as substitutes for brominated flame retardants, they have faced restrictions in some countries due to their toxic effects on organisms. We collected 37 soil and crop samples in 20 cities along the coast of South China, and OPEs were detected in all of them. Meanwhile, we studied the contamination and potential human health risks of OPEs. In soil samples, the combined concentrations of eight OPEs varied between 74.7 and 410 ng/g, averaging at 255 ng/g. Meanwhile, in plant samples, the collective concentrations of eight OPEs ranged from 202 to 751 ng/g, with an average concentration of 381 ng/g. TDCIPP, TCPP, TCEP, and ToCP were the main OPE compounds in both plant and soil samples. Within the study area, the contaminants showed different spatial distributions. Notably, higher OPEs were found in coastal agricultural soils in Guangdong Province and crops in the Guangxi Zhuang Autonomous Region. The results of an ecological risk assessment show that the farmland soil along the southern coast of China is at high or medium ecological risk. The average non-carcinogenic risk and the carcinogenic risk of OPEs in soil through ingestion and dermal exposure routes are within acceptable levels. Meanwhile, this study found that the dietary intake of OPEs through food is relatively low, but twice as high as other studies, requiring serious attention. The research findings suggest that the human risk assessment indicates potential adverse effects on human health due to OPEs in the soil-plant system along the coast of South China. This study provides a crucial foundation for managing safety risks in agricultural operations involving OPEs.

Determination of the binding affinities of OPEs to integrin αvβ3 and elucidation of the underlying mechanisms via a competitive binding assay, pharmacophore modeling, molecular docking and QSAR modeling

Organophosphate esters (OPEs) can cause adverse biological effects through binding to integrin αvβ3. However, few studies have focused on the binding activity and mechanism of OPEs to integrin αvβ3. Herein, a comprehensive investigation of the mechanisms by which OPEs bind to integrin αvβ3 and determination of the binding affinity were conducted by in vitro and in silico approaches: competitive binding assay as well as pharmacophore, molecular docking and QSAR modeling. The results showed that all 18 OPEs exhibited binding activities to integrin αvβ3; moreover, hydrogen bonds were identified as crucial intermolecular interactions. In addition, essential factors, including the -P = O structure of OPEs, key amino acid residues and suitable cavity volume of integrin αvβ3, were identified to contribute to the formation of hydrogen bonds. Moreover, aryl-OPEs exhibited a lower binding activity with integrin αvβ3 than halogenated- and alkyl-OPEs. Ultimately, the QSAR model constructed in this study was effectively used to predict the binding affinity of OPEs to integrin αvβ3, and the results suggest that some OPEs might pose potential risks in aquatic environments. The results of this study comprehensively elucidated the binding mechanism of OPEs to integrin αvβ3, and supported the environmental risk management of these emerging pollutants.

Critical review on organophosphate esters in water environment: Occurrence, health hazards and removal technologies

Organophosphate esters (OPEs), which are phosphoric acid ester derivatives, are anthropogenic substances that are widely used in commerce. Nevertheless, there is growing public concern about these ubiquitous contaminants, which are frequently detected in contaminated water sources. OPEs are mostly emitted by industrial operations, and the primary routes of human exposure to OPEs include food intake and dermal absorption. Because of their negative effects on both human health and the environment, it is clear that innovative methods are needed to facilitate their eradication. In this study, we present a comprehensive overview of the existing characteristics and origins of OPEs, their possible impacts on human health, and the merits, drawbacks, and future possibilities of contemporary sophisticated remediation methods. Current advanced remediation approaches for OPEs include adsorption, degradation (advanced oxidation, advanced reduction, and redox technology), membrane filtration, and municipal wastewater treatment plants, degradation and adsorption are the most promising removal technologies. Meanwhile, we proposed potential areas for future research (appropriate management approaches, exploring the combination treatment process, economic factors, and potential for secondary pollution). Collectively, this work gives a comprehensive understanding of OPEs, providing useful insights for future research on OPEs pollution.

Uncovering the distribution patterns and origins of organophosphate esters (OPEs) in the Yellow River Estuary via high-resolution mass spectrometry

Limited information is available regarding the pollution status of organophosphate esters (OPEs) in the environment of the Yellow River estuary. Here, n = 51 sediment samples were collected from the Yellow River estuary in 2021, and further analyzed by using the integrated target, suspect, and feature fragment-dependent nontarget OPE screening strategy developed in our laboratory. Among the 30 target OPEs, 19 were detectable in at least one of the analyzed samples, with total concentrations (Σ19OPEs) ranging from of 41.4 to 1930 ng/g dry weight (dw). On the basis of an in-house suspect compound database, we further tentatively identified 11 suspect OPEs, and they were semi-quantified. Furthermore, four other interesting findings were observed and described as follows: 1) a statistically significant difference existed in the concentrations of OPEs in sediment samples between the lower reaches of the Yellow River (n = 5 samples), and the Yellow River estuary (n = 46 samples) (unpaired t-test, p < 0.001); 2) tris(2,4-di-tert-butylphenyl)phosphate (TDTBPP) exhibited the greatest concentrations (ranging from 30.7 to 1920 ng/g dw) among all OPEs detected in the sediment samples; 3) samples from the north of the Yellow River estuary had higher OPE concentrations than those from the south; and 4) a suspect screening strategy allowed us to identify a novel OPE structure (tert-butyl)phenyl (ethyne-oxidane) bis(2,4-di-tert-butylphenyl) phosphate (TPBDTP) that exhibited a highly positive correlation relationship with TDTBPP (r = 0.749; p < 0.001). Overall, this study provided evidence that OPEs (especially TDTBPP) were ubiquitous in the sediment environment of the Yellow River estuary; thus, we emphasize that continuous monitoring of OPE pollution should be conducted in this region.

Face mask as an indicator and shield of human exposure to traditional and novel organophosphate esters

Herein, the trapping effectiveness of N95, filter KN95, medical surgical masks (MSMs), and disposable medical masks (DMMs) against 19 airborne traditional and novel organophosphate esters (OPEs) was evaluated. Laboratory simulations (n = 24 for each type of mask) showed that time-dependent accumulation of ∑19OPEs on the four types of masks ranged between 30.1 and 86.6 ng in 24 h, with the highest and lowest median amounts trapped by the N95 masks (53.3 ng) and DMMs (43.2 ng), respectively. The trapping efficiency of the four types of masks for ∑19OPEs decreased over time from 84 % to 39 % in 24 h, with N95 masks showing the highest median efficiency (70 %). Further, field investigations were conducted in five types of microenvironments (train, hospital, bus, supermarket, and canteen), and an analysis of 200 samples showed that ∑19OPEs were accumulated in the masks with a variable amount from 3.7 to 117 ng/mask. Consistent with the laboratory simulations, the N95 masks (29.0 ng/mask) exhibited the highest hourly median amount of trapped OPEs, followed by the KN95 masks (24.5 ng/mask), MSMSs (17.4 ng/mask), and DMMs (15.8 ng/mask). Triethyl phosphate (TEP), tris(1-chloro-2-propyl) phosphate (TCIPP), tri-n-butyl phosphate (TNBP), and cresyl diphenyl phosphate (CDP) as well as 4-isopropylphenyl diphenyl phosphate (4IPPDPP) and 2,4-diisopropylphenyl diphenyl phosphate (24DIPPDPP) were the most commonly detected traditional and novel OPEs. Based on the amount of OPEs trapped on the masks, we estimated the concentration of ∑19OPEs in the train microenvironment to be the highest (222 ng/m3), which is approximately 2-5 times higher than that in the other microenvironments. The results of this study prove that masks can effectively protect humans from exposure to OPEs and act as low-cost indicators of indoor contamination.

Occurrence of liquid crystal monomers in indoor and outdoor air particle matters (PM10): Implications for human exposure indoors

Liquid crystal monomers (LCMs) are potentially persistent, bioaccumulating, and toxic substances. However, limited data are available on the occurrence of LCMs in indoor and outdoor air particle matter (PM10) in residential areas. Herein, residential areas near an e-waste dismantling center (Guiyu Town, Shantou City), as well as areas away from the e-waste site (Jiedong District, Jieyang City) were selected as the sampling areas. PM10 was collected from the indoor environments of Guiyu (IGY) and Jieyang (IJY), as well as those from the outdoor environments (OGY and OJY) using the high-volume air samplers (TH-10000C). The levels of 57 LCMs in PM10 were analyzed, and the highest concentrations of LCMs were found in IGY (0.970-1080 pg/m3), followed by IJY (2.853-455 pg/m3), OGY (0.544-116 pg/m3) and OJY (0.258-35.8 pg/m3). No significant difference was observed for LCM levels in indoor PM10 between the two areas (p > 0.05), which were significantly higher than those in outdoors (p < 0.05), indicating that the release of electronic products in general indoor environments is a source of LCMs that cannot be ignored. The compositions of LCMs in outdoors were not consistent with those of indoors. The correlation analysis of individual LCMs suggested potential different sources to the LCMs in indoor and outdoor environments. The median daily intake values of Σ46LCMs via inhalation were estimated as 0.440, 1.46 × 10-2, 0.170 and 1.19 × 10-2 ng/kg BW/day for adults, and as 2.27, 2.60 × 10-2, 0.880 and 2.10 × 10-2 ng/kg BW/day for toddlers, respectively, indicating much higher exposure doses of LCMs indoors compared with the outdoors, and much higher doses for toddlers compared with adults (p < 0.05). These results reveal the potentially adverse effects of LCMs on vulnerable populations, such as toddlers, in indoor environments.

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.

Uptake, accumulation and translocation of traditional and novel organophosphate esters by rice seedlings in the presence of micro(nano)-polystyrene plastics: Effects of concentration and size of particles

Micro(nano)plastics (MNPs) and organophosphate esters (OPEs) are becoming ubiquitous as emerging pollutants. To data, the effects of MNPs on the uptake, accumulation and translocation of OPEs by rice plant are still unclear, especially for novel OPE species. In this study, the impacts of polystyrene MNPs of different sizes and concentrations on the uptake of eight OPEs (six traditional organophosphate triesters and two novel discovered aryl organophosphate triesters) by rice seedlings were investigated in hydroponic exposure experiments. The results showed that OPEs accumulated in a concentration-dependent manner in both the roots and shoots of rice seedlings. The impacts of MNPs on uptake by rice seedlings were concentration- and size-dependent by influencing the transpiration rate or activities of antioxidant enzymes. Especially, significant effects were usually found in exposure group of medium-size and high-concentration MNPs. MNPs had more obvious effects on OPE species with lower logKow in roots, whereas, more obvious effects on OPE species with higher logKow in shoots were observed. There was a significantly positive linear relationship between logTF and logKow (p < 0.001), and a significantly negative linear relationship between logRCF and logKow (p < 0.001), indicating that OPEs with higher hydrophobicity seemed to be more liable to be absorbed from solutions to roots, but difficult to further translocate to shoots. Without novel OPEs (bis-(2-ethylhexyl)-phenyl phosphate and tris(2,4-di-tert-butylphenyl)phosphate), better fits for a linear model for logKow and logRCF (or logTF) were exhibited, indicating differences between novel and traditional OPEs. This work highlights that the presence of MNPs could altered the characteristics of uptake, translocation and accumulation of OPEs in rice seedlings, and provides an important evidence for comprehensive control strategy of new pollutants.

Associations between exposure to organophosphate esters and overactive bladder in U.S. adults: a cross-sectional study

Background

The relationship between exposure to organophosphate esters (OPEs) and the risk of developing overactive bladder (OAB) is uncertain. The purpose of this study is to examine the potential link between urinary metabolites of organophosphate esters and OAB.

Method

Data from the National Health and Nutrition Examination Survey (NHANES) database of the 2011-2016 cycles were utilized. Four urinary metabolites of organophosphate esters: diphenyl phosphate (DPHP), bis (1,3-dichloro-2-propyl) phosphate (BDCPP), bis (2-chloroethyl) phosphate (BCEP), and dibutyl phosphate (DBUP) were included in the study. Multivariate logistic regression and restricted cubic spline (RCS) were used to evaluate the relationship between urinary OPEs metabolites and OAB. Interaction analysis was conducted on subgroups to confirm the findings.

Results

A total of 3,443 United States (US) adults aged 20 years or older were included in the study, of whom 597 participants were considered to have OAB. After adjusting for potential confounding factors, we found a positive association between DPHP and the risk of overactive bladder. The risk of overactive bladder increased with increasing DPHP concentrations compared with quartile 1 (quartile 2, OR = 1.19, 95% CI, 0.82-1.73, P = 0.34; quartile 3, OR = 1.67, 95% CI, 1.10-2.53, P = 0.02; Q4, OR = 1.75, 95% CI, 1.26-2.43, P = 0.002). However, after dividing the participants by gender, only the female group retained consistent results. Additionally, restricted cubic spline analysis revealed a nonlinear dose-response correlation between DPHP and OAB in female participants. In the subgroup analysis based on age, race, body mass index (BMI), recreational activity, smoking status, drinking status, hypertension, diabetes, and stroke, the interaction analysis revealed that the findings were uniform.

Conclusion

Our findings indicate that exposure to DPHP could elevate the risk of OAB in US adult females. Further experimental studies are needed to explore the underlying mechanism in the future.

Gas-particle partitioning of organophosphate esters in indoor and outdoor air and its implications for individual exposure

The extensive utilization of organophosphate esters (OPEs) has resulted in their widespread presence in the environment, raising concerns about potential human health risks. In this study, 13 OPEs were analyzed in both gas and particle phases as well as in indoor and outdoor atmospheric environments. Moreover, human exposure to OPEs were investigated within a university environment, focusing on forehead contact and individual PM2.5 inhalation. The results showed similar distribution patterns of OPEs indoors and outdoors, although higher concentrations were found indoors. The average atmospheric concentration of ∑OPEs (combining particle and gaseous OPEs) was 1575 pg/m3 in the outdoor environment and 6574 pg/m3 ∑OPEs in the indoor microenvironments. The overwhelming majority of OPEs exhibit a pronounced propensity to adsorb onto PM2.5 particles. Notably, the concentration of OPEs on the forehead differed significantly from that in the atmospheric environment, whereas individual PM2.5 exposure was consistent with the concentration of indoor PM2.5. Intriguingly, some OPEs with high octanol-water partition coefficient (log Kow) were not detected in the environment but found on human foreheads. Gas-particle partitioning was predicted using the Harner-Bidleman and Li-Ma-Yang models and the results were in agreement with the monitoring data for approximately half of the OPE monomers. Correlations between OPEs exposure and gas-particle partitioning were found to be more significant for novel OPEs. No non-cancer risk to humans through individual exposure to OPEs was identified via forehead exposure or inhalation. The previously unreported relationship between individual exposure and the environmental occurrence of traditional and novel OPEs demonstrated in this study highlights the importance of evaluating the potential health risks associated with actual OPE exposure.

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.

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.

Distribution and exposure risk assessment of chlorinated paraffins and novel brominated flame retardants in toys

Chlorinated paraffins (CPs) and novel brominated flame retardants (NBFRs) were examined in children's toys collected from 13 families in China. The concentrations of short-chain CPs (SCCPs), medium-chain CPs (MCCPs) and NBFRs in toys were 32.8-1,220,954 ng/g, not detected-2,688,656 ng/g and 0.08-103,461 ng/g, respectively. Median concentrations of SCCPs and MCCPs in toys were 1355 and 1984 ng/g, respectively, while except for pentabromobenzene (median:0.04 ng/g), the median concentrations of the other 8 NBFRs were below method detection limits. Rubber and foam toys contained higher amounts of CPs and NBFRs. Among the SCCPs and MCCPs monitored, Cl_6-8-SCCPs/MCCPs and C₁₄-MCCPs were the most abundant congener groups. On the other hand, decabromodiphenyl ethane was the predominant NBFR in toys. Moreover, to understand the role of toys in children's daily exposure to CPs and NBFRs, hand-to-mouth contact, mouthing, and dermal exposure were assessed for children aged 3 months to 6 years. Hand-to-mouth contact is the primary exposure route for children's exposure to CPs (25.4-536 ng/kg/day) and NBFRs (1.24-26.2 ng/kg/day) through toys. A low deleterious risk associated with children's toys concerning CPs and NBFRs was investigated based on the margin of exposure and hazard quotient values.

Characterizing the obesogenic and fatty liver-inducing effects of Acetyl tributyl citrate (ATBC) plasticizer using both in vivo and in vitro models

The global incidence of obesity and non-alcoholic fatty liver disease (NAFLD) is rising rapidly in recent years. Environmental factors including usage of plastics and exposure to chemicals have been proposed as important contributors to the obesity pandemic. Acetyl tributyl citrate (ATBC) is a non-phthalate plasticizer widely used in food packaging, personal care products, medical devices and children's toys etc. Due to its high leakage rate from plastics, exposure risk of ATBC keeps increasing. Although there are some studies investigating the safety of ATBC on human health, these studies mainly focused on high dosages and information regarding ATBC safety at environmental-relevant low levels is still limited. In this study, we aimed to evaluate the safety of subchronic exposure to environmentally-relevant concentrations of ATBC. C57BL/6J mice were orally exposed to ATBC for 6 or 14 weeks. Results indicated that ATBC exposure increased the body weight gain, the body fat content and the size of adipocytes, induced liver steatosis in mice. Consistent with in vivo effects, ATBC treatment increased the intracellular lipid accumulation in vitro hepatocytes. Transcriptome sequencing, qRT-PCR analysis and western blotting revealed that ATBC exposure affected the expression of genes involved in de novo lipogenesis and lipid uptake. Therefore, based on our subchronic and in vitro results, it suggested that ATBC might be a potential environmental obesogen with metabolism-disturbing and fatty liver-inducing risk, and its application in many consumer products should be carefully re-evaluated.

Dynamic processes in conjunction with microbial response to unveil the attenuation mechanisms of tris (2-chloroethyl) phosphate (TCEP) in non-sanitary landfill soils

Although the environmental and health risks of chlorinated organophosphate esters (OPEs-Cl) have drawn much attention, its environmental behaviors have been insufficiently characterized. As a notable sink of this emerging contaminant, non-sanitary landfills, which may decompose/accumulate OPEs-Cl, is of particular concern. In the present study, the dynamic processes of the typical OPEs-Cl, tris(2-chloroethyl) phosphate (TCEP), in non-sanitary landfill soils were analyzed under anaerobic condition, and the microbial taxa involved in these processes were explored. Our results showed that TCEP could be simultaneously reduced by abiotic and biotic processes, as it was reduced by 73.9% and 65.5% over the 120-day experiment in landfill humus and subsoil, respectively. Notably, the degradation of TCEP was significantly (p < 0.05) enhanced under the stress of a high TCEP concentration (10 μg g^-1), while its ecological consequences were found insignificant regarding the microbial diversity and community structure and the typical soil redox processes, including Fe(III)/SO₄^2- reduction and methanogenesis, in both soils. The microbial diversity of subsoil was significantly lower, and acetate was an important factor in changing microbial communities in landfill soils. The microbes in the family Nocardioidaceae and genus Pseudomonas might contribute to in the degradation of TCEP in landfill humus and subsoil, respectively. The metabolism related to sulfur and sulfate respiration were significantly (p < 0.05) correlated with TCEP reduction, and Desulfosporosinus were found as a potentially functional microbial taxon in TCEP degradation in both soils. The results could advance our understanding of the environmental behavior of OPEs-Cl in landfill-like complex environments.

Dietary intake assessment of known and unknown organophosphate esters (OPEs) in foodstuffs via high-resolution mass spectrometry

We applied an integrated target, suspect, and non-target screening strategy to analyze known and unknown organophosphate esters (OPEs) in 107 foodstuffs collected from Nanjing City, China, in 2020. Twelve out of 19 target OPEs were detectable in at least one of the analyzed samples. Among the nine food categories, meat samples were contaminated the most severely with a mean ΣOPEs concentration of 68.5 ng/g wet weight (ww). In most food categories, tris(2,4-di-tert-butylphenyl) phosphate was the predominant OPE with a mean concentrations of 2.26 ng/g ww. In the food extract samples, suspect and non-target analysis identified other 6 suspect OPEs and 1 non-target OPE, of which two were fully identified as tri-m-cresyl phosphate, and trihexyl phosphate. Based on the measured OPE concentrations, we estimated the daily per capita dietary intakes of ΣOPEs for Nanjing residents to be 423 ng/kg bw/day, which is less than the reference dosage value of each OPE. Collectively, this study provides new information regarding the comprehensive identification of OPEs in foodstuffs, and revealed the importance of dietary risk assessment of this emerging class of contaminants.

Target and suspect analysis of liquid crystal monomers in soil from different urban functional zones

Recent studies have reported the occurrence of liquid crystal monomers (LCMs) in sediment, indoor dust, hand wipes, and human serum samples; however, information regarding their contamination status in soil is currently unavailable. The concentrations of 39 target LCMs were determined in n = 96 surface soil samples collected from five different urban functional zones including agricultural, scenic, industrial, commercial, and residential zones. We observed that 76 of 96 surface soil samples contained at least 19, 13, 16, 19, and 14 of the 39 target LCMs that were detectable in samples from agricultural, scenic, industrial, commercial, and residential zones, respectively. The LCMs in the samples from the agricultural zone exhibited the highest mean concentrations of 12.9 ng/g dry weight (dw), followed by those from commercial (5.23 ng/g dw), residential (3.30 ng/g dw), industrial (2.48 ng/g dw), and scenic zones (0.774 ng/g dw). Furthermore, strong and statistically significant (p < 0.05) correlations were observed for several pairs of LCMs (3cH2B vs. 5bcHdFB in the agricultural zone; 5bcHdFB vs. 2bcHdFB, 5bcHdFB vs. 3cH2B in the commercial zone; 5bcHdFB vs. 2bcHdFB in the industrial zone), indicating that they might have similar commercial applications and sources. Based on a newly established database containing 1173 LCMs, suspect screening was applied to discover other LCMs in these 96 soil samples using gas chromatograph coupled with quadrupole-time-of-flight mass spectrometry (GC-QTOF/MS). We tentatively identified 51 LCM formulas with 69 chemical structures. Collectively, this study provides the first evidence for the occurrence of LCMs in soil samples, and suggests that LCMs could be widely distributed across all five urban functional zones.

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.

Percutaneous absorption and exposure risk assessment of organophosphate esters in children's toys

The percutaneous penetration and exposure risk of organophosphate esters (OPEs) from children's toys remains largely unknown. Percutaneous penetration of OPEs was evaluated by EPISkin™ model. Chlorinated OPEs (Cl-OPEs) and alkyl OPEs, except tris(2-ethylhexyl) phosphate, exhibited a fast absorption rate and good dermal penetration ability with cumulative absorptions of 57.6-127 % of dosed OPEs. Cumulative absorptions of OPEs through skin cells were inversely associated with their molecular weight and log octanol-water partition coefficient. Additionally, a quantitative structure-activity relationship model indicated that topological charge and steric features of OPEs were closely related to the transdermal permeability of these chemicals. With the clarification of the factors affecting the transdermal penetration of OPEs, the level and exposure risk of OPEs in actual toys were studied. The summation of 18 OPE concentrations in 199 toy samples collected from China ranged from 6.82 to 228,254 ng/g, of which Cl-OPEs presented the highest concentration. Concentrations of OPEs in toys exhibited clear type differences. Daily exposure to OPEs via dermal, hand-to-mouth contact, and mouthing was evaluated, and dermal contact was a significant route for children's exposure to OPEs. Hazard quotients for noncarcinogenic risk assessment were below 1, indicating that the health risk of OPEs via toys was relatively low.

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.

Comparative study of neonicotinoid insecticides (NNIs) and NNI-Related substances (r-NNIs) in foodstuffs and indoor dust

Comparative studies of neonicotinoid insecticides (NNIs) and NNI-related substances (r-NNIs) in foodstuffs and indoor dust are rare. Herein, we investigated the feature fragmentations of nine NNIs in high-energy collision dissociation cells via high-resolution orbitrap mass spectrometry and observed that NNIs can consistently generate several feature fragments (e.g., C6H5NCl+, C4H3NSCl+, and C6H5NF3+). Consequently, NNIs and r-NNIs were comprehensively (targeted, suspect, and feature fragment-dependent) detected in 107 foodstuff and 49 indoor dust samples collected from Nanjing City (eastern China). We fully or tentatively identified 9 target NNIs and 5 r-NNIs in these samples. NNIs and r-NNIs were detected in 93.5% of the analyzed foodstuff samples, and high concentrations were detected in vegetables (mean: 409 ng/g wet weight [ww]) and fruits (127 ng/g ww). Regarding indoor dust, imidacloprid and acetamiprid exhibited extremely high detection frequencies and contamination levels, and the highest mean concentrations of NNIs and r-NNIs were detected in dormitory samples. Based on the NNI and r-NNI concentrations in the analyzed samples, the mean estimated daily intake values for Chinese adults and children via dietary intake and dust ingestion were 2080-8190 ng/kg bw/day and 378-2680 pg/kg bw/day, respectively.

Characterization of organophosphate esters (OPEs) and polyfluoralkyl substances (PFASs) in settled dust in specific workplaces

An analytical method for detecting flame retardants was slightly modified and optimized for the simultaneous determination of 11 organophosphate esters (OPEs) and 26 polyfluoralkyl substances (PFASs) contained in dust. All the analytes were determined in HPLC/MS-MS, and OPEs were also analyzed in GC/MS, and the results were compared. The study was conducted through the investigation of the Standard Reference Material SRM 2585 of the National Institute of Standard and Technology (NIST). The results were compared with the available reference mass fraction reported in the NIST certificate. The mass fraction obtained for the other OPEs and PFASs was compared to available data in the literature. After verifying the reliability of the results, the method was applied to environmental samples of settled dust, collected in four workplaces, where OPE and PFAS content is expected to be higher than in house dust: a mechanical workshop, an electronic repair center, a disassembly site, and a shredding site of two electronic waste recycling plants. By analyzing both PFASs and OPEs in the same samples, the present work demonstrated that the selected working places were more polluted in OPEs than houses; on the contrary, PFAS content in house dust proved to be more than ten times higher than that in workplaces. Additional research is necessary to confirm these data. Nevertheless, because this preliminary study showed not negligible concentrations of OPEs in some workplaces and of PFASs in houses, their monitoring should be extended to other domestic and selected working sites.

Organophosphate esters in agro-foods: Occurrence, sources and emerging challenges

Safety and sustainable agro-food production is important for food and nutrition security. Agro-foods safety is challenged by various emerging environmental contaminants. Organophosphate esters (OPEs) have been reported to occur in various agro-food items worldwide, which has resulted in increasing concerns for effects on health of humans and wildlife, including through agriculture. However, information on presence, sources and transfer routes of OPEs in agro-foods, and consequent health risks remains scant. This review critically evaluates available information on concentrations of OPEs in various agro-foods, and discusses potential sources of OPEs in agro-foods, which are closely related to the ambient agri-environment, agricultural inputs, and agro-foods processing. Some directions for future research are suggested. First, since food is an important exposure pathway to OPEs, systematic monitoring of concentrations of OPEs in various categories of agro-foods is recommended. Second, surveillance of concentrations and characteristics of OPEs in agro-foods and ambient agri-environments, agricultural inputs or processing in the agro-food chain is needed to obtain a more complete description of exposure and transmission behavior of OPEs in agro-foods. Third, future comprehensive studies of transmission, metabolism and accumulation of OPEs in animals or plants, are required. Finally, measures to control emissions of OPEs as sources to agriculture should be taken.

Elevated concentration and high Diversity of organophosphate esters (OPEs) were Discovered in Sediment from Industrial, and E-Waste Recycling Areas

Aquatic environments in industrial, and e-waste recycling areas might undergo severe contamination; however, there are few studies comprehensively assessing the pollution status of organophosphate esters (OPEs) in these two areas. Here, we applied both atmospheric pressure chemical ionization (APCI) and electron spray ionization (ESI) sources in our target, suspect, and functional group-dependent screening strategy, which enhanced the confidence for confirmation on precursor ions of OPEs. Then, n=53 sediment samples (30 from the industrial area, and 23 from the e-waste recycling area) were analyzed. Twenty-three out of 30 target OPEs were quantifiable in these analyzed samples. Total OPE concentrations (Σ₃₀OPEs) in samples from e-waste recycling area range from 12.8 to 9250 ng/g dry weight (dw), that are statistically significantly greater (t-test, p < 0.001) than those from industrial area (25.1-5520 ng/g dw). Σ₃₀OPEs in the sediments from industrial, or e-waste recycling area are statistically significantly greater (one-way ANOVA, p < 0.001) as compared to those (32.0-369 ng/g dw) from Taihu Lake in our previous study. In sediment from three areas, suspect and non-target analysis fully or tentatively identified other 20 OPEs. Four of them have not been recorded or registered in any of online chemical databases, and they are tentatively named as ((methoxy(phenoxy)phosphoryl)oxy)phenyl diphenyl phosphate (mPPODP), (tert-butyl)phenyl (ethyne-oxidane) bis(2,4-di-tert-butylphenyl) phosphate (TPBDTP), bis(dichlorophenyl) propane-1,3-diyl bis(hexylated phosphate) (BDCBHP), and bis(2-hexadecoxyethyl) ethyl phosphate (BHEPP). Overall, this study provided new insights regarding both analytical methodology and pollution status of OPEs, and highlights that elevated concentrations and high diversity of OPEs exist in sediments from industrial, and e-waste recycling areas.

Organophosphate esters in children and adolescents in Liuzhou city, China: concentrations, exposure assessment, and predictors

Dermal contact with dust is commonly considered an important pathway of exposure to organophosphate esters (OPEs), but the importance of OPE uptake from diet is unclear. Herein, we used hand wipes to estimate OPE exposure from indoor dust and examined whether urinary OPE metabolite concentrations were influenced by sociodemographic characteristics, OPE amount in hand wipes, and dietary factors. OPEs were measured in urine and hand wipes from 6 to 18-year-old children and adolescents (n=929) in Liuzhou, China. Sociodemographic and dietary factors were obtained from questionnaire. Six OPE metabolites were detected in >70% of the urine samples, and seven OPEs were detected in >50% of the hand wipes. Estimated daily intakes (EDIs) were calculated using urinary OPE metabolites to investigate the total daily intake of OPEs, in which 0.36-10.1% of the total intake was attributed to the exposure from dermal absorption. In multivariate linear regression models, sex, age, and maternal education were significant predictors of urinary OPE metabolite concentrations. Urinary diphenyl phosphate (DPHP) is positively associated with its parent compounds 2-ethylhexyl-diphenyl phosphate (EHDPP) and triphenyl phosphate (TPHP) in hand wipes. High versus low vegetable intake was associated with a 23.7% higher DPHP (95% confidence interval (CI): 0.51%, 52.1%). Barreled water drinking was associated with a 30.4% (95% CI: 11.8%, 52.0%) increase in bis(1-chloro-2-propyl) 1-hydroxy-2-propyl phosphate (BCIPHIPP) compared to tap water drinking. Our results suggested the widespread exposure to OPEs in children and adolescents. In addition to dermal absorption, dietary intake may be an important exposure source of certain OPEs.

Occurrence, Distribution, and Human Exposure of Emerging Liquid Crystal Monomers (LCMs) in Indoor and Outdoor Dust: A Nationwide Study

Liquid crystal monomers (LCMs) are a class of emerging, persistent, bioaccumulative, and toxic organic pollutants. They are detected in various environmental matrixes that are associated with electronic waste (e-waste) dismantling. However, their occurrence and distribution in indoor and outdoor dust on a national scale remain unknown. In this study, a dedicated target analysis quantified a broad range of 60 LCMs in dust samples collected across China. The LCMs were frequently detected in indoor (n = 48) and outdoor dust (n = 97; 37 sampled concomitantly with indoors dust) from dwellings, and indoor dust from cybercafés (n = 34) and phone repair stores (n = 22), with median concentrations of 41.6, 94.7, 106, and 171 ng/g, respectively. No significant spatial difference was observed for the concentrations of the total LCMs among distinct geographical regions (p > 0.05). The median daily intake values of the total LCMs via dust ingestion, dermal contact, and inhalation were estimated at 1.50 × 10^-2, 2.90 × 10^-2, and 8.57 × 10^-6 ng/kg BW/day for adults and 1.47 × 10^-1, 1.22 × 10^-1, and 2.18 × 10^-5 ng/kg BW/day for children, respectively. These estimates suggested higher exposure risks for children and indicated that dust ingestion and dermal contact significantly contribute to the human intake of LCMs. The microenvironmental pollution levels of LCMs together with the potential exposure risks associated with some of these chemicals are of concern for human health.

Characteristics of iron-containing magnetic particles in household dust from an urban area: A case study in the megacity of Shanghai

In order to characterize the magnetic properties and trace sources of household dust particles, magnetic measurements, geochemical and SEM/TEM analyses were performed on vacuum dust from 40 homes in Shanghai, China. Iron-containing magnetic particles (IMPs) in the household dust were dominated by magnetite, while maghemite, hematite and metallic iron were also present. The IMPs were mainly composed of coarse-grained particles (e.g., >0.1 µm). Ultrafine superparamagnetic (SP) grains (<30 nm) increased proportionately with the abundance of the total IMPs. Household dust had more and coarser IMPs than background soil, but less and finer IMPs than street dust and industrial emissions (coal combustion and metallurgy). Metallic Fe and spherical IMPs, originating from brake wear abrasion and coal combustion, respectively, have been observed using the SEM/TEM. Contents of magnetic particles were positively correlated to Mo, Ni and Sb, while HIRM was associated with As, Mo, Pb and Sb. The multiple lines of evidence including magnetic measurements, geochemical and SEM/TEM analyses suggested that industrial and traffic emissions and street dust were dominant contributors to the IMPs. Such an approach can help to establish more precisely the sources of household dust particles and could be applied to other indoor contexts and further urban environments.

High-Resolution Mass Spectrometry Screening of Emerging Organophosphate Esters (OPEs) in Wild Fish: Occurrence, Species-Specific Difference, and Tissue-Specific Distribution

There is a dearth of information regarding the pollution status of emerging organophosphate esters (OPEs) in wild fish. Here, we optimized and validated a quick, easy, cheap, effective, rugged, and safe (QuEChERS) pretreatment method, which was further applied for target, suspect, and nontarget screening of OPEs in n = 48 samples of wild fishes from Taihu Lake (eastern China). This integrated technique allows us to fully identify 20 OPEs, and 9 out of them are emerging OPEs detected in wild fish for the first time. Importantly, some of the emerging OPEs, i.e., tris(2,4-di-tert-butylphenyl) phosphate (TDtBPP), 4-tert-butylphenyl diphenyl phosphate (BPDP), and 2-isopropylphenyl diphenyl phosphate (IPDP), exhibited greater or at least comparable contamination levels as compared to traditional ones. There were no statistically significant interspecies (n = 6) differences regarding OPE concentrations. However, we observed significant differences on OPE concentrations among different tissues of silver carp (Hypophthalmichthys molitrix), for which the intestine has the highest OPE mean concentration (46.5 ng/g wet weight (ww)), followed by the liver (20.1 ng/g ww) ≈ brain (20.0 ng/g ww) > gill (14.8 ng/g ww) > muscle (11.4 ng/g ww). An interesting exception is IPDP, which presents an unexpectedly high concentration in the brain (0.510 ng/g ww). Collectively, this study expands our understanding of OPE contamination in wild fish and clearly shows that emerging TDtBPP, IPDP, and BPDP could play an equally important role as traditional OPEs in contribution of OPE pollution in wild fish samples.

Occurrence and exposure risk assessment of organic micropollutants in indoor dust from Malaysia

Indoor dust is an important source of human exposure to hazardous organic micropollutants (OMPs) because humans spend about 90 % of their time in the indoor environments. This study initially analyzed the concentrations and compositions of OMPs in the dust of different indoor environments from Kuala Lumpur, Malaysia. A total of 57 OMPs were detected and assigned to 7 chemical classes in this study. The total concentration of OMPs ranged from 5980 to 183,000 ng/g, with the median concentration of 46,400 ng/g. Personal care products, organophosphate esters, and pesticides were the dominant groups, with their median concentrations at 12,000, 10,000, and 5940 ng/g, respectively. The concentrations and compositions of influential OMPs varied in different microenvironments, suggesting different sources and usage patterns in the house. Then, the noncarcinogenic and carcinogenic risks of exposure to these substances for diverse age groups were assessed based on the median concentration. Cumulative noncarcinogenic risks of these OMPs via ingestion pathway were estimated to be negligible (1.41 × 10^-4 - 1.87 × 10^-3). The carcinogenic risks of these OMPs were higher than 10^-6 (1.63 × 10^-6 - 6.17 × 10^-6) and should be noted. Theobromine accounted for more than 89 % of the cumulative cancer risk, implying that the carcinogenic risk of theobromine needs further monitoring in the future. Toddler was the most affected group for cancer risk among all the age groups, regardless of the microenvironments. These findings from this study may provide a benchmark for future efforts to ensure the safety of indoor dust for the local residents.

Exposure to organophosphate esters in elderly people: Relationships of OPE body burdens with indoor air and dust concentrations and food consumption

Human exposure to OPEs is pervasive and should be of great concern due to associations with adverse health effects, especially in susceptible populations. In this study, body burdens and exposure pathways of OPEs were investigated for 76 healthy elderly people in Jinan, China based on the measured OPE and metabolite concentrations in human bio-samples (whole blood and urine) and paired environmental matrices (air and dust), as well as food frequency questionnaire. Eight of 16 OPEs and 5 of 11 metabolites were detected in > 50% of whole blood and urine samples, respectively. Tri(1-chloro-2-propyl) phosphate (TCIPP), tris(2-chloroethyl) phosphate (TCEP), tri-phenyl phosphate (TPHP), and 2-ethylhexyl di-phenyl phosphate (EHDPP) were frequently detected and abundant in whole blood, while their corresponding metabolites were detected at low frequencies or levels in urine. The reduced metabolic and/or excretory capacity of elderly people may be an important reason, implying a higher health risk to them. Fourteen OPEs had over 50% detection frequencies in indoor air and dust, while 6 di-esters in indoor dust. Tris(2-ethylhexyl) phosphate (TEHP) in indoor dust and tri-n-butyl phosphate (TnBP) in indoor air were positively correlated with paired levels in blood but not with their metabolites (BEHP and DnBP) in urine. Combined with the direct intakes of BEHP and DBP from dust, blood is indicated as more suitable biomarker for TEHP and TnBP exposure. High consumption frequencies of several foods were associated with higher blood concentrations of three OPEs and urinary levels of four di-OPEs, indicating the importance of dietary exposure pathway. Estimated daily total intakes of OPEs via inhalation, dust ingestion, and dermal absorption ranged from 2.78 to 42.0 ng/kg bw/day, which were far less than the reference dosage values. Further studies were warranted to explore the potential health effects of OPE exposure in the elderly populations.

Occurrence and Dietary Intake of Organophosphate Esters via Animal-Origin Food Consumption in China: Results of a Chinese Total Diet Study

Although diet is regarded as a major exposure source of organophosphate esters (OPEs), the dietary survey of OPEs in China has been limited. Based on the sixth Chinese Total Diet Study (TDS) conducted during 2016-2019 in 24 of 34 provinces in China, 14 OPEs were detected in 96 food composites from four animal-origin food categories. Twelve OPEs were detected in more than 80% of the samples and 2-ethylhexyl diphenyl phosphate (EHDPP) presented the highest median concentration (1.63 ng/g wet weight (ww)). The most contaminated food composite was meat, with a median ∑₁₄OPEs of 13.6 ng/g ww, followed by aquatic food (11.5 ng/g ww), egg (7.63 ng/g ww), and milk (3.51 ng/g ww). The contribution of the meat group was close to or even greater than 50% in the estimated dietary intake (EDI) of OPEs. The average (range) EDI of the ∑₁₄OPEs via animal food consumption for a Chinese "standard man" was 34.4 (6.18-73.3) ng/kg bodyweight (bw)/day. The geographical distribution showed higher EDI in southern coastal provinces compared to the northern inland provinces. Nevertheless, the highest EDI of ∑₁₄OPEs from animal food was still more than 10 times lower than the reference dose. This is the first national survey of OPEs in foods from China.

Organophosphate Esters in China: Fate, Occurrence, and Human Exposure

Organophosphate esters (OPEs) are widely used as flame retardants and plasticizers. OPEs have been released into various environments (e.g., water, sediments, dust and air, and soil). To investigate the occurrence and distribution of OPEs in various environments in China, this review collects and discusses the published scientific studies in this field. Chlorinated OPEs, as flame retardants, are the predominant OPEs found in the environment. The analysis of data revealed large concentration variations among microenvironments, including inflowing river water (range: 0.69-10.62 µgL^-1), sediments (range: 0.0197-0.234 µg/g), dust (range: 8.706-34.872 µg/g), and open recycling sites' soil (range: 0.122-2.1 µg/g). Moreover, OPEs can be detected in the air and biota. We highlight the overall view regarding environmental levels of OPEs in different matrices as a starting point to monitor trends for China. The levels of OPEs in the water, sediment, dust, and air of China are still low. However, dust samples from electronic waste workshop sites were more contaminated. Human activities, pesticides, electronics, furniture, paint, plastics and textiles, and wastewater plants are the dominant sources of OPEs. Human exposure routes to OPEs mainly include dermal contact, dust ingestion, inhalation, and dietary intake. The low level of ecological risk and risk to human health indicated a limited threat from OPEs. Furthermore, current challenges and perspectives for future studies are prospected. A criteria inventory of OPEs reflecting the levels of OPEs contamination association among different microenvironments, emerging OPEs, and potential impact of OPEs on human health, particularly for children are needed in China for better investigation.

Identifying Citric Acid Esters, a Class of Phthalate Substitute Plasticizers, in Indoor Dust via an Integrated Target, Suspect, and Characteristic Fragment-Dependent Screening Strategy

Citrate acid esters (CAEs) have been proposed as a class of phthalate substitute plasticizers; however, information on their occurrence in indoor environments is rare. By using liquid chromatography coupled with a quadrupole-Orbitrap mass spectrometer, we developed an integrated strategy that can be applied for target, suspect, and characteristic fragment-dependent screening of CAEs. In n = 50 indoor dust samples collected from Nanjing City (China), three CAEs, namely, acetyl tributyl citrate (ATBC; mean: 412,000 ng/g), tributyl citrate (TBC, 11,600 ng/g), and triethyl citrate (TEC, 10,900 ng/g), exhibited the greatest contamination levels. Total concentrations of CAEs (∑₈CAEs) were statistically significantly (p < 0.01) greater than those of common organophosphate triesters (OPTEs), a class of ubiquitous contaminants in dust. Suspect and characteristic fragment-dependent screening (m/z 111.0078 ([C₅H₃O₃]⁺) and m/z 129.0181 ([C₅H₅O₄]⁺)) of CAEs were further conducted for the same batch of samples. We tentatively identified six novel CAEs, and the most frequent and abundant CAE was fully identified as tributyl aconitate (TBA). Statistically significant correlation relationships were observed on dust levels between TBA vs ATBC (r = 0.650; p < 0.01) and TBA vs TBC (r = 0.384; p < 0.01), suggesting their similar sources in dust samples.