Organophosphate esters (OPEs) in corals of the South China Sea: Occurrence, distribution, and bioaccumulation

Organophosphate esters (OPEs) have garnered significant attention in recent years. In view of the enormous ecosystem services value and severe degradation of coral reefs in the South China Sea, this study investigated the occurrence, distribution, and bioaccumulation of 11 OPEs in five coral regions: Daya Bay (DY), Weizhou Island (WZ), Sanya Luhuitou (LHT), Xisha (XS) Islands, and Nansha (NS) Islands. Although OPEs were detected at a high rate, their concentration in South China Sea seawater (1.56 ± 0.89 ng L-1) remained relatively low compared to global levels. All OPEs were identified in coral tissues, with Luhuitou (575 ± 242 ng g-1 dw) showing the highest pollution levels, attributed to intense human activities. Coral mucus, acting as a defense against environmental stresses, accumulated higher ∑11OPEs (414 ± 461 ng g-1 dw) than coral tissues (412 ± 197 ng g-1 dw) (nonparametric test, p < 0.05), and their compositional characteristics varied greatly. In the case of harsh aquatic environments, corals increase mucus secretion and then accumulate organic pollutants. Tissue-mucus partitioning varied among coral species. Most OPEs were found to be bioaccumulative (BAFs >5000 L kg-1) in a few coral tissue samples besides Triphenyl phosphate (TPHP). Mucus' role in the bioaccumulation of OPEs in coral shouldn't be ignored.

Distribution patterns and origins of organophosphate esters in soils from different climate systems on the Tibetan Plateau

Organophosphate esters (OPEs) are extensively applied in various materials as flame retardants and plasticizers, and have high biological toxicity. OPEs are detected worldwide, even in distant polar regions and the Tibetan Plateau (TP). However, few studies have been performed to evaluate the distribution patterns and origins of OPEs in different climate systems on the TP. This study investigated the distribution characteristics, possible sources, and ecological risks of OPEs in soils from the different climate systems on the TP and its surroundings. The total concentrations of OPEs in soil varied from 468 to 17,451 pg g-1 dry weight, with greater concentrations in southeast Tibet (monsoon zone), followed by Qinghai (transition zone) and, finally, southern Xingjiang (westerly zone). OPE composition profiles also differed among the three areas with tri-n-butyl phosphate dominant in the westerly zone and tris(2-butoxyethyl) phosphate dominant in the Indian monsoon zone. Correlations between different compounds and altitude, soil organic carbon, or longitude varied in different climate zones, indicating that OPE distribution originates from both long-range atmospheric transport and local emissions. Ecological risk assessment showed that tris(2-chloroethyl) phosphate and tri-phenyl phosphate exhibited medium risks in soil at several sites in southeast Tibet. Considering the sensitivity and vulnerability of TP ecosystems to anthropogenic pollutants, the ecological risks potentially caused by OPEs in this region should be further assessed.

Exposure to organophosphate esters and maternal-child health

Organophosphate esters (OPEs) are a class of chemicals now widely used as flame retardants and plasticizers after the phase-out of polybrominated diphenyl ethers (PBDEs). However, OPEs carry their own risk of developmental toxicity, which poses concern for recent birth cohorts as they have become ubiquitous in the environment. In this review, we summarize the literature evaluating the association between OPE exposure and maternal, perinatal, and child health outcomes. We included original articles investigating associations of OPE exposure with any health outcome on pregnant women, newborns, children, and adolescents. We found 48 articles on this topic. Of these, five addressed maternal health and pregnancy outcomes, 24 evaluated prenatal OPE exposure and child health, 18 evaluated childhood OPE exposure and child/adolescent health, and one article evaluated both prenatal and childhood OPE exposure. These studies suggest that OPE exposure is possibly associated with a wide range of adverse health outcomes, including pregnancy loss, altered gestational duration and smaller birthweight, maternal and neonatal thyroid dysfunction, child metabolic dysregulation and abnormal growth, impaired neurodevelopment, and changes in immune response. Many of the reported outcomes associated with OPE exposure varied by child sex. Findings also varied substantially by OPE metabolite and exposure time. The OPEs most frequently measured, detected, and found to be associated with health outcomes were triphenyl phosphate (TPHP, metabolized to DPHP) and tris(1,3-dichloro-2-propyl) phosphate (TDCIPP, metabolized to BDCIPP). The extensive range of health outcomes associated with OPEs raises concern about their growing use in consumer products; however, these findings should be interpreted considering the limitations of these epidemiological studies, such as possible exposure misclassification, lack of generalizability, insufficient adjustment for covariates, and failure to consider chemical exposures as a mixture.

OPEs-ID: A software for non-targeted screening of organophosphate esters based on liquid chromatography-high-resolution mass spectrometry

Organophosphate esters (OPEs) are widely used as flame retardants and plasticizers, presenting a potential threat to the environment and human health. To date, no automatic software exists for the nontargeted screening of OPEs. In this study, OPEs-ID, a user-friendly software, was developed for the identification of OPEs using liquid chromatography-high-resolution mass spectrometry. The main workflow of OPEs-ID included fragments-dependent precursor ion screening, elemental composition determination, extracted ion chromatograms (EIC) comparison, and molecular structure identification via MetFrag strategy. A mixture of 17 OPE standards was identified with an identification rate of 100% by OPEs-ID. OPEs-ID demonstrated a rate of 94.1% for correctly ranking within the top 1 candidate in a local database (41.2% in PubChem) for the 17 OPE standards, which remarkably improved the identification when compared to conventional in silico fragmentation algorithms. Using a pooled airborne fine particle sample (PM2.5), OPEs-ID could automatically retrieve 22 valid molecules with structure candidates. The detection frequencies of 9 newly identified OPEs were between 13% and 100% in the 32 PM2.5 samples. Their semi-quantification concentrations were comparable to those of some traditional OPEs. Overall, OPEs-ID offers a powerful tool to significantly enrich our understanding of the OPEs present in the environment.

Fate of organophosphate esters from the Northwestern Pacific to the Southern Ocean: Occurrence, distribution, and fugacity model simulation

Eleven organophosphate esters (OPEs) in the air and seawater were investigated from the northwestern Pacific Ocean to the Southern Ocean during the 2018 Chinese 34th Antarctic Scientific Expedition. The concentration of total OPEs ranged from 164.82 to 3501.79 pg/m3 in air and from 4.54 to 70.09 ng/L in seawater. Two halogenated OPEs, tri(chloropropyl) phosphate (TCPP) and tri (2-chloroethyl) phosphate (TCEP), were generally more abundant than the non-halogenated OPEs. A level III fugacity model was developed to simulate the transfer and fate of seven OPEs in the air and seawater regions of the central Ross Sea. The model results indicate that OPEs are transferred from the air to the seawater in the central Ross Sea in summer, during which the Ross Sea acts as a final OPE sink. Dry and wet deposition dominated the processes involving OPE transfer to seawater. The OPE degradation process was also found to be more pervasive in the atmosphere than in the seawater region. These findings highlights the importance of long-range transport of OPEs and their air-seawater interface behavior in the Antarctic.

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.

Organophosphate esters (OPEs) in plastic food packaging: non-target recognition, and migration behavior assessment

Organophosphate esters (OPEs) are widely used as plasticizers in plastic food packaging; however, the migration of OPEs from plastic to food is largely unstudied. We do not even know the specific number of OPEs that exist in the plastic food packaging. Herein, an integrated target, suspect, and nontarget strategy for screening OPEs was optimized using ultrahigh-performance liquid chromatography-high-resolution mass spectrometry (UHPLC-HRMS). The strategy was used to analyze 106 samples of plastic food packaging collected in Nanjing city, China, in 2020. HRMS allowed full or tentative identification of 42 OPEs, of which seven were reported for the first time. Further, oxidation products of bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite (AO626) in plastics were identified, implying that the oxidation of organophosphite antioxidants (OPAs) could be an important indirect source of OPEs in plastics. The migration of OPEs was examined with four simulated foods. Twenty-six out of 42 OPEs were detected in at least one of the four simulants, particularly isooctane, in which diverse OPEs were detected at elevated concentrations. Overall, the study supplements the list of OPEs that humans could ingest as well as provides essential information regarding the migration of OPEs from plastic food packaging to food.

The aomogeneous and heterogeneous oxidation of organophosphate esters (OPEs) in the atmosphere: Take diphenyl phosphate (DPhP) as an example

Organophosphate esters (OPEs) are widely detected in the atmosphere. However, the atmospheric oxidative degradation mechanism of OPEs has not been closely examined. This work took density functional theory (DFT) to investigate the tropospheric ozonolysis of organophosphates, represented by diphenyl phosphate (DPhP), including adsorption mechanisms on the surface of titanium dioxide (TiO₂) mineral aerosols and oxidation reaction of hydroxyl groups (·OH) after photolysis. Besides, the reaction mechanism, reaction kinetics, adsorption mechanism, and ecotoxicity evaluation of the transformation products were also studied. At 298 K, the total reaction rate constants k_O3, k_OH, k_TiO2-O3, and k_TiO2-OH are 5.72 × 10^-15 cm³ molecule^-1 s^-1, 1.68 × 10^-13 cm³ molecule^-1 s^-1, 1.91 × 10^-23 cm³ molecule^-1 s^-1, and 2.30 × 10^-10 cm³ molecule^-1 s^-1. The atmospheric lifetime of DPhP ozonolysis in the near-surface troposphere is 4 min, much lower than that of hydroxyl radicals (·OH). Besides, the lower the altitude is, the stronger the oxidation is. The TiO₂ clusters carry DPhP promoting ·OH oxidation but inhibiting ozonolysis of DPhP. Finally, the main transformation products of this process are glyoxal, malealdehyde, aromatic aldehydes, etc., which are still ecotoxic. The findings shed new light on the atmospheric governance of OPEs.

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.

Organophosphate ester exposure among Chinese waste incinerator workers: Urinary levels, risk assessment and associations with oxidative stress

Organophosphate esters (OPEs), which are frequently used as flame retardants and plasticizers in versatile products, are readily released to the external environment. Although workers at municipal waste incineration plants may be extensively exposed to OPEs, only scarce health monitoring and risk assessments have been conducted in this population. In this study, we investigated the levels of eight metabolites of organophosphate esters (mOPEs) and the oxidative stress marker 8-hydroxy-2-deoxyguanosine (8-OHdG) in urine samples from 73 waste incinerator workers and 97 general residents from Shenzhen, China between September 2016 and June 2017. The overall detection rate of mOPEs was 82.2 %-100 %, and higher concentrations of di-p-cresyl phosphate and chlorinated mOPEs [bis(2-chloroethyl) phosphate (BCEP), bis(1-chloro-2propyl) phosphate (BCIPP), bis(1,3-dichloro-2-propyl) phosphate) (BDCIPP)] were found among incinerator workers than among general residents. The incinerator workers also showed significantly higher levels of 8-OHdG than general residents, but the measured levels of most mOPEs were not significantly correlated with the level of 8-OHdG; this may be because co-exposure to multiple toxic compounds can lead to oxidative stress. Risk assessment using Monte Carlo simulations revealed that 95 % of the incinerator workers were free from non-carcinogenic effects due to OPEs exposure (hazard index = 0.27, 95 % CI: 0.09, 0.77). However, the carcinogenic risk of tris(2-chloroethyl) phosphate (TCEP) for incinerator workers was between 10-6 and 10-4. These results indicate that incinerator workers are extensively exposed to OPEs, and better protective measures need to be implemented.

Potential adverse outcome pathways with hazard identification of organophosphate esters

Data-driven analysis and pathway-based approaches contribute to reasonable arrangements of limited resources and laboratory tests for continuously emerging commercial chemicals, which provides opportunities to save time and effort for toxicity research. With the widespread usage of organophosphate esters (OPEs) on a global scale, the concentrations generally reached up to micromolar range in environmental media and even in organisms. However, potential adverse effects and toxicity pathways of OPEs have not been systematically assessed. Therefore, it is necessary to review the current situation, formulate the future research priorities, and characterize toxicity mechanisms via data-driven analysis. Results showed that the early toxicity studies focused on neurotoxicity, cytotoxicity, and metabolic disorders. Then the main focus shifted to the mechanisms of cardiotoxicity, endocrine disruption, hepatocytes, reproductive and developmental toxicity to vulnerable sub-populations, such as infants and embryos, affected by OPEs. In addition, several novel OPEs have been emerging, such as bis(2-ethylhexyl)-phenyl phosphate (HDEHP) and oxidation derivatives (OPAsO) generated from organophosphite antioxidants (OPAs), leading to multiple potential ecological and human health risks (neurotoxicity, hepatotoxicity, developmental toxicity, etc.). Notably, in-depth statistical analysis was promising in encapsulating toxicological information to develop adverse outcome pathways (AOPs) frameworks. Subsequently, network-centric analysis and quantitative weight-of-evidence (QWOE) approaches were utilized to construct and evaluate the putative AOPs frameworks of OPEs, showing the moderate confidences of the developed AOPs. In addition, frameworks demonstrated that several events, such as nuclear receptor activation, reactive oxygen species (ROS) production, oxidative stress, and DNA damage, were involved in multiple different adverse outcome (AO), and these AOs had certain degree of connectivity. This study brought new insights into facilitating the complement of AOP efficiently, as well as establishing toxicity pathways framework to inform risk assessment of emerging OPEs.

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.

Non-target screening and risk assessment of organophosphate esters (OPEs) in drinking water resource water, surface water, groundwater, and seawater

By use of an integrated target, suspect, and non-target screening strategy, we investigated occurrence and spatial distribution of organophosphate esters (OPEs) in four types of water (drinking water resource water, surface water, groundwater, and seawater) collected from Jiangsu Province (China) in 2021 (n = 111). Eighteen out of 23 target OPEs were detectable at least once in these analyzed samples, and the total concentrations (Σ18OPEs) of OPEs in various water samples exhibited a descending order following as: groundwater (67026 ng/L) > surface water (35803 ng/L) > drinking water resource water (21055 ng/L) > seawater (17820 ng/L). The highest concentration detected in groundwater may be ascribed to pollution from surrounding factories. Among the target OPEs, triethyl phosphate (TEP), tris(chloroethyl) phosphate (TCEP), and tris (1-chloro-2-propyl) phosphate (TCIPP) were the most abundant congeners with the average concentrations of 407 ng/L, 143 ng/L, and 475 ng/L, respectively. Besides of 18 target OPEs, we further identified 17 suspect OPEs (3 of them were fully identified by authentic standards) on the basis of in-house suspect screening OPE database, and 2 non-target organophosphates (OPs) on the basis of feature fragments. One of these 2 non-target OPs was fully identified as bis(2-chloroethyl) 2-chloroethylphosphonate (B2CE2CEPP) by matching the retention time and MS/MS data with authentic standard, and the other one was preliminarily identified as 2,4,8,10-tetra-tert-butyl-6-methoxydibenzo[d,f][1,3,2]dioxaphosphepin-6-one (TTBMDBDOPPO). We also observed that B2CE2CEPP shared a similar structure with TCEP, suggesting that they may have similar toxicological characteristics and commercial sources. The ecological and human health risk assessments indicated that all OPEs posed a low or negligible ecological risk to aquatic organisms (algae, crustacean, and fish), and negligible risk to human health except for trimethyl phosphate (TMP) in drinking water resource water.

Infants' diminished response to DTaP vaccine is associated with exposure to organophosphate esters

Organophosphate esters (OPEs) are commonly applied as flame retardants and plasticizers. Toxicological studies suggest exposure effects on immune endpoints, raising concerns as infants' OPE exposures are elevated compared to older children and adults due to hand-to-mouth behavior and breastfeeding. Here, we sought to evaluate the immune responsiveness of infants to a neoantigen (e.g., a newly encountered antigen) in the presence of OPE exposures. As a proxy for immune responsiveness, children were given three doses of the Diphtheria, Tetanus, and Pertussis (DTaP) vaccine as recommended, and diphtheria and tetanus antibodies were evaluated in serum samples collected when children were 12 months old (n = 84). Titers were compared, based on maximum sample overlap, to measurements of OPE metabolites in spot urine samples collected before vaccination (age 2 months, n = 73) and at the time of antibody assessment (12 months of age, n = 46). Metabolites of two chlorinated OPEs were significantly associated with diminished antibodies for diphtheria and tetanus. A metabolite of tris (1,3-dichloroisopropyl)phosphate (TDCIPP) measured at 2 months was associated with decreased diphtheria antibodies (-0.07 IU/mL per log₁₀ increase in metabolite). One metabolite of tris(2-chloroisopropyl)phosphate (TCIPP) measured at 12 months was associated with decreased tetanus antibodies (-0.57 IU/mL per log₁₀ increase in metabolite). These results provide some preliminary insights for OPE exposure impacts on vaccine responses in early life and may have important implications for immune health through childhood and adulthood.

Industrial Production of Organophosphate Flame Retardants (OPFRs): Big Knowledge Gaps Need to Be Filled?

Since the phase-out of traditional halogenated flame retardants (HFRs), interests of research are gradually being shifted to organophosphate flame retardants (OPFRs), and this can be reflected by the increasing number of publications on OPFRs year by year. Here, an extensive survey is conducted in an attempt to generate a list of OPFRs that are being produced in factories, and to investigate the annual production volume (APV). This survey suggests that at least n = 56 OPFR monomers and n = 62 OPFR mixtures are being currently produced in 367 factories around the world, and 201 out of them are in Mainland China. APV of OPFRs was estimated as 598,422 metric tons, and this number could be underestimated due to the limitation of available information. We also notice that current researches are confined to a limited number of OPFRs, especially for OP esters (OPEs), and other OPFRs with different structures from OPEs has been rarely studied. Based on all the collected datasets, we provide five recommendations for how to proceed with future research to more comprehensively understand the currently-produced OPFRs in the environment.

Semi-volatile organic compounds in fine particulate matter on a tropical island in the South China Sea

Measurements of hazardous semi-volatile organic compounds (SVOCs) in remote tropical regions are rare. In this study, polycyclic aromatic compounds (PACs) [including polycyclic aromatic hydrocarbons (PAHs), nitrated PAHs (NPAHs), and oxygenated PAHs (OPAHs)], organophosphate esters (OPEs), and phthalic acid esters (PAEs) were measured in fine particulate matter (PM_2.5) at Yongxing Island in the South China Sea (SCS). The concentrations of PACs (median = 53.5 pg/m³) were substantially low compared with previous measurements. The concentration weighted trajectory (CWT) model showed that the eastern and southern China was the main source region of PAC, occurring largely during the northeast (NE) monsoon. The PM_2.5 showed remarkably high concentrations of OPEs (median = 3231 pg/m³) and moderate concentrations of PAEs (13,013 pg/m³). Some Southeast Asian countries were largely responsible for their higher concentrations, driven by the tropical SCS monsoons. We found significant atmospheric loss of the SVOCs, which is an explanation for the low concentrations of PACs. Enhanced formation of N/OPAHs originated from tropical regions was also observed. The positive matrix factorization model was applied to apportion the SVOC sources. The results, as well as correlation analyses of the SVOC concentrations, further indicate insignificant local sources and enhanced atmospheric reactions on this island.

The associations between organophosphate esters and urinary incontinence in the general US population

Organophosphate esters (OPEs) impact health in many ways. Since its relationship with urinary incontinence remains unknown, we aimed to explore their associations in the US general population. We combined the results of urine specimens test and self-reported urinary incontinence conditions from the National Health and Nutrition Examination Survey (NHANES) 2013-2014 among 2666 participants and then conducted linear regression and logistic regression to analyse associations between log2-transformed OPE concentrations and urinary incontinence. We found that 0.92% of men and 15.74% of women complained of mixed urinary incontinence (MUI). The concentrations of diphenyl phosphate (DPHP) were significantly correlated to MUI among women when treated as a continuous variable (adjusted odds ratio (OR) = 1.15; 95% confidence interval (CI), 1.01-1.31; p = 0.0369) and as a categorical variable (adjusted OR = 1.24; 95% CI, 1.03-1.49; p for trend = 0.0245), whereas no positive correlation was found in males. There were no significant associations between the other three OPEs: bis(2-chloroethyl) phosphate (BCEP), bis(1,3-dichloro-2-propyl) phosphate (BDCPP) and dibutyl phosphate (DBUP). The association of DPHP with an increased prevalence OR of MUI in women is a public health concern; future prospective studies are needed to explore its potential mechanism.

Microplastics in freshwater sediments: Analytical methods, temporal trends, and risk of associated organophosphate esters as exemplar plastics additives

It has been estimated that over 28 million tonnes of plastics end up in water bodies annually. These plastics degrade into microplastics (MPs), which along with microbeads and MPs from other sources such as wastewater treatment plants continue to threaten the aquatic system. At such small sizes, and corresponding larger surface areas per unit mass/volume, MPs exhibit enhanced capacity for absorbing and desorbing toxic chemicals/additives. Therefore, MPs can serve as vectors through which additives as well as other persistent, bio-accumulative, and toxic chemicals can enter the food chain. Additives are a significant component of most plastic products with some identified as hazardous to health and the environment. One group of additives that has continued to attract interest is organophosphate esters (OPEs), which are used both as flame retardants and plasticizers. Some of these OPEs are suspected carcinogens and endocrine disruptors and have been reported to exert serious toxic effects on freshwater biota. Separate studies on the presence and fate in the freshwater environment of these additives and MPs have emerged recently. However, no studies exist that examine the extent to which plastics additives such as OPEs in sediments are sorbed to MPs as opposed to the sediment itself. This has potentially important implications for the bioavailability of such additives and studies to examine this are recommended. This paper reviews critically the current state-of-knowledge on MPs in freshwater sediments, methods for their analysis, as well as their occurrence, temporal trends, and risks to the freshwater aquatic environment. Moreover, to facilitate the study of additives associated with MPs that have been extracted from sediments, we consider the possible effect of MP isolation methods on the determination of concentrations of associated additives like OPEs.

Traditional and novel organophosphate esters (OPEs) in PM2.5 of a megacity, southern China: Spatioseasonal variations, sources, and influencing factors

Organophosphate esters (OPEs) are ubiquitous contaminants in the environment, whereas their atmospheric processes and fate are poorly understood. The present study revealed the spatial heterogeneity and seasonal variations of traditional and novel OPEs in PM_2.5 (particulate matter with diameters < 2.5 μm) across a megacity (including residential areas and potential source sites) in South China. Potential influencing factors on the contamination levels of OPEs were addressed. The total concentrations of 11 traditional OPEs ranging from 262 to 42,194 pg/m³ (median = 1872 pg/m³) were substantially higher than those of 10 novel OPEs (33.5-3835 pg/m³, median = 318 pg/m³). Significant spatial and temporal variations in the concentrations of most OPEs were observed. The overall district-specific contamination levels in this city showed dependence on the secondary industry sector for non-predominant OPEs and on the tertiary industry for predominant OPEs. The seasonal variations of the OPE concentrations suggest difference in their sources or influence of meteorological conditions. The correlations between the individual OPEs in PM_2.5 are determined largely by either their applications or physicochemical properties (in particular vapor pressure). The correlations between OPE concentrations and each meteorological factor (temperature, relative humidity, wind speed, and surface solar radiation) were inconsistent (positive and negative). Wind speed had the greatest effect on the OPE levels; While most OPEs bound to PM_2.5 were not efficiently scavenged by below-cloud rainfall. The results suggest that atmospheric half-life and Henry's Law Constant of OPEs are also determining factors for the wind speed and rainfall influence, respectively. However, mechanisms underlying the influence of meteorological conditions on atmospheric OPEs still need further research.

Application of Hi-throat/Hi-volume SPE technique in analyzing occurrence, influencing factors and human health risk of organophosphate esters (OPEs) in drinking water of China

Organophosphate esters (OPEs) are typical industrial additives widely applied in various industrial and household products, but they may pollute drinking water. In the present study, the occurrence of OPEs in drinking water was analyzed. For this purpose, 25 drinking water samples were collected from households in 25 cities in China. The concentrations of OPEs were accurately determined according to a high-throughput organic analysis testing combined with high-volume solid phase extraction (Hi-throat/Hi-volume SPE) technique. Through this technique, nine OPEs were detected, with spiked recoveries from 77% to 101%, and their total concentrations (ΣOPEs) ranging from 46.8 to 251 (average 126) ng L^-1. The detection frequencies of the selected OPEs determined via Hi-throat/Hi-volume SPE were 88.0%-100%, which are much higher than those previously reported. The limit of detections of the OPEs was low at < 0.01 ng L^-1, which could be mainly attributed to the high volume of accumulated drinking water (>20 L). OPEs in drinking water presented a decreasing trend from cities in coastal provinces to inland cities of China. Redundancy analysis showed that the concentrations of OPEs in drinking water were significantly influenced by economic-demographic influencing factors. The non-carcinogenic and lifetime carcinogenic risks (non-CR and CR) of the analyzed OPEs in drinking water were negligible for urban residents in China.

Newly discovered bis-(2-ethylhexyl)-phenyl phosphate (BEHPP) was a ubiquitous contaminant in surface soils from a typical region, South China

The organophosphate ester (OPE), bis-(2-ethylhexyl)-phenyl phosphate (BEHPP), was recently identified as an abundant contaminant in indoor dust samples; however, its pollution status in other matrices remains unknown. Here, n = 95 surface soil samples were collected from a prefecture-level city (hereafter referred to as D city) in South China during 2019, and further analyzed to accurately determine the concentrations of BEHPP and eight other OPEs, including tris(2-chloroethyl) phosphate (TCEP), tris(1,3-dichloro-isopropyl) phosphate (TDCIPP), triphenyl phosphate (TPHP), tris(2-butoxyethyl) phosphatetris (TBOEP), 2-ethylhexyl diphenyl phosphate (EHDPP), tris(2-ethylhexyl) phosphate (TEHP), 4-biphenylol diphenyl phosphate (BPDPP), and tris(2-biphenyl) phosphate (TBPHP). BEHPP was detected in all six functional areas (agricultural, scenic, commercial, industrial, and residential areas) of this region, and exhibited a high detection frequency of 67.4%, with a median concentration of 0.455 ng/g dry weight (DW range: nd-7.05 ng/g dw), regardless of the functional area. Samples from commercial, industrial, and residential areas contained significantly greater BEHPP concentrations than those from agricultural and scenic areas. Furthermore, strong and statistically significant correlations were observed between BEHPP and other OPE congeners, particularly for TEHP (r = 0.764, p < 0.001), TBOEP (r = 0.687, p < 0.001), and TPHP (r = 0.709, p < 0.001), indicating that BEHPP may have similar commercial applications and sources to these compounds in surface soil. Collectively, this study provides the first evidence of the presence of BEHPP in soil samples, and indicates that this emerging contaminant is widely distributed across all five functional areas of a typical region (South China).

Young infants' exposure to organophosphate esters: Breast milk as a potential source of exposure

Organophosphate esters (OPEs) are applied as both flame retardants and plasticizers to a variety of consumer items such as home furnishings, construction materials, and children's products. While some assessments have characterized exposure among toddlers and young children, little is known about the OPE exposure among infants, who are a vulnerable population due to their rapid development. Here, we collected spot urine samples from 6-week-old (n = 100) and 12-month-old infants (n = 63), with about half of the infants evaluated at both ages (n = 52), to characterize OPE exposure and determine what factors contributed to higher exposures. Five of six OPE metabolites analyzed were detected frequently (>70%). Diphenyl phosphate was detected in every urine sample, while bis(2-chloro-isopropyl) phosphate (BCIPP) was the most abundant metabolite measured overall. Concentrations of bis(1-chloro-2-propyl) 1-hydroxy-2-propyl phosphate (BCIPHIPP) and BCIPP [i.e., metabolites of tris(2-chloro-isopropyl) phosphate (TCIPP)] were significantly greater among 6-week-old infants compared to 12-month-olds, while levels of other OPE metabolites were not statistically different in the first year of life. OPE metabolites were generally correlated with one another in samples collected at each age (r_s = 0.25-0.75; p < 0.05), and except BCIPHIPP, concentrations of the same metabolite were correlated over time (r_s = 0.41-0.53; p < 0.05). Breastfeeding at 6 weeks of age and owning a larger number of children's products were associated with increased concentrations of urinary BDCIPP. Infants who were currently receiving breast milk had higher levels of TCIPP metabolites; urinary BCIPP concentrations were 6.2 times higher in infants receiving breast milk at 6 weeks of age, and BCIPHIPP levels were 2.2 times higher for 12-month-old infants receiving breast milk (10^β = 7.2; 95% CI: 1.6-32.1 and 10^β = 3.2; 95% CI: 1.2-8.1, respectively). Differences in the predominant TCIPP metabolite associated with breastfeeding may suggest differences in metabolism with age. Cumulatively, our results suggest levels of OPE exposure may be higher for infants than other age groups, including toddlers and older children.

Elevated occupational exposure to chlorinated phosphate esters at a construction materials manufacturing plant

BACKGROUND

Numerous studies have documented that the general population is widely exposed to organophosphate esters (OPEs), yet studies on the emissions of OPEs in the industrial application processes and their occupational exposure are scarce. The aim of this study was to assess the exposure to OPEs for workers engaged in OPE-retarded construction material manufacturing plant in China.

METHOD

Paired dust samples (12 samples each time) from an OPEs retarded building materials manufacturing plant during the plant uptime and downtime have been analyzed for tris(2-chloroethyl)-phosphate (TCEP), tris(2-chloroisopropyl) phosphate (TCPP), and other commonly used OPEs. Moreover, nine OPEs metabolites (mOPEs) in urine samples (n = 42) from fourteen workers who engaged in this plant were also measured. The daily exposure doses to OPEs were estimated from the measured urinary concentrations of corresponding mOPEs.

RESULTS

Thirteen out of fourteen studied OPEs (except for tri-n-propyl phosphate, TnPP) were determined in all dust samples from the manufacturing plant, and TCEP and TCPP were the predominant compounds in dust collected from the plant uptime and downtime. Overall, the occupationally exposed population had significantly higher (p < 0.01) urinary levels of mOPE, especially for bis (2-chloroethyl) phosphate (BCEP), relative to the reference population. Workshop workers who directly involved in the production of OPEs treated products had higher OPEs exposure. Risk assessment revealed that cancer risk (1.5 × 10^-6-8.5 × 10^-4) for all workers was larger than 1 × 10^-6 when levels of mOPEs in urine from workers were used for estimating OPEs exposure, revealing moderate to high potential cancer risk to workers from OPEs exposure.

CONCLUSION

To our knowledge, this is the first study reporting emissions of OPEs in OPE-treated products manufacturing processes and the potential exposure of the occupationally exposed population. OPEs, especially for TCEP and TCPP, present at elevated levels and pose moderate to high potential health risks to the exposed workers, emphasizing the importance of strengthening occupational exposure prevention in similar industries.

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

Here, fifteen OPEs were investigated in n = 50 floor dust samples collected from six types of indoor spaces in Nanjing, eastern China, in the year 2018. Ten OPEs, including tris(2-chloroethyl) phosphate (TCEP), tris(2-chloroisopropyl) phosphate (TCIPP), tris(1,3-dichloro-isopropyl) phosphate (TDCIPP), tris(2-ethylhexyl) phosphate (TEHP), tris(2-butoxyethyl) phosphate (TBOEP), 2-ethylhexyl-diphenyl phosphate (EHDPP), triphenyl phosphate (TPHP), tris(methyl-phenyl) phosphate (TMPP), 4-biphenylyl diphenyl phosphate (4-BPDP) and tris(2-biphenylyl) phosphate (TBPP), were detected in at least one of the analyzed samples (>method limits of quantification). Regardless of indoor spaces, EHDPP (34% of Σ₈OPEs, mean: 1.43 μg/g) and TDCIPP (19%, 0.81 μg/g) were the ascendant OPEs in indoor floor dust. 4-BPDP and TBPP were detectable in indoor floor dust samples, but at relatively low detection frequencies with 2% and 10%, respectively. Various indoor microenvironments exhibited different pollution characteristics of OPEs. Floor dust collected from electronic product maintenance centers contained the richest OPE contaminants with highest mean Σ₈OPEs concentration of 7.92 μg/g. On the basis of measured Σ₁₀OPEs concentrations in dust sample, we estimated daily intake via floor dust ingestion to be 1.37, 0.75 and 1.24 ng/kg BW/day for electronic engineers, undergraduates, and graduate students under mean-exposure scenario, respectively. Overall, our study reported the occurrence of 4-BPDP and TBPP in environmental samples for the first time, and demonstrated that indoor floor dust ingestion exposure does values were far less than reference dosage values of oral toxicity proposed by United States Environmental Protection Agency (USEPA) Integrated Risk Information System.

Associations between organophosphate esters and sex hormones among 6-19-year old children and adolescents in NHANES 2013-2014

BACKGROUND

Organophosphate esters (OPEs) are a class of alternative replacements for polybrominated diphenyl ethers. In vitro and in vivo studies suggested that OPEs may disrupt the homeostasis of sex steroid hormones. However, human evidence in children and adolescents is limited.

OBJECTIVES

We conducted a cross-sectional analysis of the associations between OPE biomarkers and sex steroid hormones among children (6-11 years) and adolescents (12-19 years) in the U.S. National Health and Nutrition Examination Survey, 2013-2014.

METHODS

Participants aged 6-19 years who had available data on urinary OPE metabolites, serum sex hormones [total testosterone (TT), estradiol (E₂)] and sex hormone binding globulin (SHBG) were included (n = 544). Free androgen index (FAI) calculated as TT divided by SHBG and a ratio of TT to E₂ (TT/E₂) were generated. Five urinary OPE metabolites were examined. A constructed puberty status was defined as either high steroid hormone levels (TT ≥ 50 ng/dL in males and E₂ ≥ 20 pg/ml in females) or onset of menarche. Multiple linear regression and weighted quantile sum (WQS) regression analyses stratified by sex-age and sex-puberty-status groups were conducted to examine the associations of OPE metabolites and its mixture with sex hormone levels.

RESULTS

After adjusting for covariates, dibutyl phosphate (DBUP) and dibutyl phosphate (DPHP) were significantly inversely associated with TT (or FAI) and E₂; DBUP was negatively associated with SHBG; and DPHP was positively associated with SHBG and TT/E₂ in female adolescents. In male adolescents, we observed monotonic negative associations of bis(1,3-dichloro-2-propyl) phosphate (BDCPP), DBUP or DPHP with TT (or FAI) and E₂, and positive associations of BDCPP and DPHP with SHBG. Among adolescents, the OPEs index was negatively associated with TT [WQS beta = -0.29 (95% confidence interval: -0.51, -0.07) in males and -0.15 (-0.28, -0.01) in females ], FAI [-0.46 (-0.71, -0.2) in males and -0.23 (-0.41, -0.05) in females] and E₂ [-0.25 (-0.41, -0.1) in males and -0.33 (-0.59, -0.08) in females], with stronger associations with TT and FAI in males and a slightly stronger association with E₂ in females. In addition, the OPEs index presented a comparable positive association with SHBG in both sexes of adolescents. In contrast, significant associations of individual OPE metabolites or OPEs index with sex hormones were sparse in children. Results by sex-puberty status in single pollutant and WQS regression analyses presented a similar pattern, where most of the significant associations were limited to the pubertal individuals. Of note, stronger inverse associations of the OPEs index with TT and FAI remained in pubertal boys. But the association between the OPEs index and E₂ was non-significant in pubertal girls, and only in pubertal boys did the OPEs index show a significant and stronger inverse association with E₂.

CONCLUSIONS

Exposure to OPEs, either individually or as a mixture, was associated with decreased levels of certain sex steroid hormones (TT, FAI, and E₂) and increased levels of SHBG in adolescents or pubertal individuals, with the associations presenting somewhat sex-dependent pattern. However, there is little evidence of the significant associations in children or prepubescent ones. Given the cross-sectional nature of the analysis, our findings need further confirmation.

Organophosphate ester flame retardants and plasticizers in a Chinese population: Significance of hydroxylated metabolites and implication for human exposure

Organophosphate esters (OPEs) are widely used as flame retardants, plasticizers and defoamers and their exposure are likely associated with a number of adverse effects in humans. In this study, tris(chloroethyl) phosphate and thirteen OPE metabolites including six hydroxylated OPEs (HO-OPEs) were analyzed in 46 urine samples, collected from 8 provinces located across different regions in China. 1-Hydroxy-2-propyl bis(1-chloro-2-propyl) phosphate (BCIPHIPP) and 2-hydroxyethyl bis(2-butoxyethyl) phosphate (BBOEHEP) were major metabolites of their parent compounds with detection frequencies of 54.3%-89.1%, which were all higher than their corresponding OPE diesters (2.2%-6.5%). The urine-based estimated daily intake (EDI) of OPEs ranged from 0.06 ng/kg·bw for tris(2-butoxyethyl) phosphate (TBOEP) to 273 ng/kg·bw for 2-ethylhexyl phenyl phosphate. Analyzed with concentrations in paired dust samples, dust exposure to OPEs and their diesters may explain 0.28%-23.8% of the urine-based EDI of OPEs and the contribution of dust TBOEP was the highest. Although direct exposure to OPE diesters in dust showed a minor contribution, their intake via food and drinking water may account for a larger portion of urinary OPE metabolites. Overall, the hazard quotients of four OPEs indicated no immediate exposure risk for the investigated Chinese residents but the cumulative and long-term chronic effects involving exposure to other OPEs and OPE diesters are worth further concerns.

The environment behavior of organophosphate esters (OPEs) and di-esters in wheat (Triticum aestivum L.): Uptake mechanism, in vivo hydrolysis and subcellular distribution

To reveal the metabolic characteristic of organophosphate esters (OPEs) in plants, uptake efficiency, subcellular distribution and hydrolysis of OPEs and their hydrolysis metabolites in wheat (Triticum aestivum L.) were investigated by hydroponic experiments. Tris(2-chloroethyl) phosphate (TCEP) and bis(2-chloroethyl) phosphate (BCEP) were prone to transporting to shoots by transpiration stream, with the translocation factors of 6.2 and 21 for TCEP and BCEP, respectively, as greater than 40% of TCEP and BECP were distributed in the cell sap due to their hydrophilicity. Hydrophobic OPEs (i.e. tri-n-butyl phosphate [TnBP] and triphenyl phosphate [TPhP]), and their hydrolysis metabolites (di-n-butyl phosphate [DnBP] and diphenyl phosphate [DPhP]) were stored in roots, resulting in low translocation capacity in wheat. As organophosphate diesters with relatively high proportions in cell walls (70-84% of DnBP and 41-43% of DPhP) are difficult to being transmembrane transported due to electrical repulsion of the cytomembrane, it is supposed that cell walls could be a main location for in vivo hydrolysis of OPEs. For DnBP, absorption by roots after in vitro hydrolysis of TnBP in hydroponic media was also an important source in wheat. Inhibition experiments showed that it is usually a non-energy-consuming process for root uptake of OPEs and their hydrolysis metabolites. The uptake of OPEs (i.e. TCEP, TnBP, and TPhP) and DPhP were facilitated diffusion mediated by aquaporins or anion channels, while uptake of BCEP and DnBP were simple diffusion processes. This study illustrated the distribution characteristics and translocation capacity of OPEs and their diester metabolites at the subcellular level.

Distribution of flame retardants in smartphones and identification of current-use organic chemicals including three novel aryl organophosphate esters

Smartphones have become an integral tool of society; in the year 2017, approximately 30% of the global population used smartphones. After their life cycle of use, most smartphones are not recycled and are instead discarded as e-waste, which increases the probability that chemicals they contain will eventually be released into the natural environment. In this study, the concentration and distribution of 52 major flame retardant (FR) chemicals were measured in eight components of seven models of largely produced smartphones. The results demonstrated that organophosphate esters (OPEs) were the principal FRs in these smartphone devices, while a suite of halogenated flame retardants (HFRs), including 25 polybrominated diphenyl ethers (PBDEs), were not detected. Triphenyl phosphate (TPHP) was the primary FR in the smartphones, followed by tris(2-butoxyethyl) phosphate (TBOEP), 2-ethylhexyl diphenyl phosphate (EHDPP), triethyl phosphate (TEP), tris(2-chloroethyl) phosphate (TCEP), and tris(2-chloroisopropyl) phosphate (TCIPP), respectively. The average smartphone contained 3.37 × 10⁷ ng TPHP/unit, which was concentrated in the phone screen. We estimated the annual amount of ΣOPEs and TPHP in smartphones used globally to be 53.5 and 51.8 tons, respectively. Extracts of phone screens were further analyzed by use of an untargeted screening strategy, and other 10 organic chemicals were identified. Interestingly, 3 out of them shared similar backbone structure of TPHP, and these 3 chemicals were tri(2,4-di-t-butylphenyl) phosphate (TDTBPP; CAS No. 95906-11-9), 2-biphenylol diphenyl phosphate (BPDPP; 132-29-6), and tris (2-biphenyl) phosphate (TBPHP; 132-28-5). Collectively, this study provided the first information on distribution of major FRs in different components of smartphones, and also identified other 10 current-use organic chemicals including three novel aryl OPEs which should be considered in further environmental studies including in toxicological and monitoring programs.

Enhanced degradation of triphenyl phosphate (TPHP) in bioelectrochemical systems: Kinetics, pathway and degradation mechanisms

Triphenyl phosphate (TPHP) is one of the major organophosphate esters (OPEs) with increasing consumption. Considering its largely distribution and high toxicity in aquatic environment, it is important to explore an efficient treatment for TPHP. This study aimed to investigate the accelerated degradation of TPHP in a three-electrode single chamber bioelectrochemical system (BES). Significant increase of degradation efficiency of TPHP in the BES was observed compared with open circuit and abiotic controls. The one-order degradation rates of TPHP (1.5 mg L^-1) were increased with elevating sodium acetate concentrations and showed the highest value (0.054 ± 0.010 h^-1) in 1.0 g L^-1 of sodium acetate. This result indicated bacterial metabolism of TPHP was enhanced by the application of micro-electrical field and addition acetate as co-substrates. TPHP could be degraded into diphenyl phosphate (DPHP), hydroxyl triphenyl phosphate (OH-TPHP) and three byproducts. DPHP was the most accumulated degradation product in BES, which accounted more than 35.5% of the initial TPHP. The composition of bacterial community in BES electrode was affected by the acclimation by TPHP, with the most dominant bacteria of Azospirillum, Petrimonas, Pseudomonas and Geobacter at the genera level. Moreover, it was found that the acute toxic effect of TPHP to Vibrio fischeri was largely removed after the treatment, which revealed that BES is a promising technology to remove TPHP threaten in aquatic environment.

Differential exposure to organophosphate flame retardants in mother-child pairs

BACKGROUND

Humans are ubiquitously exposed to flame retardants, including organophosphate esters (OPEs), through direct contact with consumer products or exposure through household dust. Children are at increased risk because of their proximity to dust, hand-to-mouth activity, and the importance of childhood as a critical period in neurodevelopment.

OBJECTIVES

To quantify differences in exposure levels between mothers and children (three to six years of age), we analyzed urinary metabolites of OPEs. We additionally assessed the ability of silicone wristbands (measuring ambient exposure) to predict urinary metabolite concentrations.

METHODS

We selected 32 mother and child dyads from an existing cohort. Participants provided baseline urine samples and wore wristbands for one week. After the first week, they returned their wristbands and provided a second urine sample. During the second week, participants wore a second wristband that they returned at the end of week two with a third and final urine sample.

RESULTS

We found significantly higher levels of bis(1,3-dichloro-2-propyl) phosphate (BDCIPP) (p < 0.001) and lower levels of bis(1-chloro-2-isopropyl) 1-hydroxy-2-propyl phosphate (BCIPHIPP) (p < 0.001) in children's urine samples compared to mothers' samples at baseline. We found that triphenylphosphate (TPHP), tris(1,3-dichloroisopropyl) phosphate (TDCIPP), and tris(1-chloro-2-propyl) phosphate (TCIPP) measured in wristbands predicted their respective metabolite levels in urine.

CONCLUSION

Children had higher levels than mothers for two of six flame retardant metabolites measured in urine. Generally, wristband measurements positively predicted internal dose. As little is known about the health effects of OPEs on child development, future research is needed to determine the impact of differential exposure.

Occurrence, distribution and risk of organophosphate esters in urban road dust in Beijing, China

As a major group of plasticizers and flame-retardants, organophosphate esters (OPEs) have attracted particular attention due to their wide occurrence and potential impacts on human health and ecosystems. In the present study, the occurrence and distribution of 14 OPEs, including seven Alkyl-OPEs, three Cl-OPEs, and four Aryl-OPEs, were investigated in 65 road dust samples collected from November to December 2014 in Beijing, China. Cl-OPEs were the predominant compounds in the road dust samples, with the median concentration of 646 μg/kg, followed by the Alkyl-OPEs (median 135 μg/kg) and Aryl-OPEs (median 129 μg/kg). Tris(2-chloro-1-methylethyl) phosphate (TCPP) was the most abundant OPE with the median concentration of 384 μg/kg. In addition, OPEs levels showed significant difference (p < 0.05) in the spatial distribution. Markedly higher levels of OPEs were observed in 2nd and 3rd ring road with heavy traffic and high population density, indicating that the traffic and population were important factors for this distribution pattern. It was further supported by the analysis of OPEs in roadside soil and indoor dust in the vicinity of road dust sample sites. Finally, the average daily dose (ADD) for OPEs via inhalation, dermal absorption, and ingestion was calculated to evaluate the carcinogenic and non-carcinogenic risks to residents exposed to OPEs in the road dust. Risk assessment revealed that the risk originating from exposure to OPEs of road dust is currently low in Beijing, China.

Organophosphate esters in East Greenland polar bears and ringed seals: Adipose tissue concentrations and in vitro depletion and metabolite formation

East Greenland is a contamination "hot spot" for long-range transported anthropogenic chemicals, including organophosphate esters (OPEs). High concentrations of OPEs have been reported in arctic air while very little is known for wildlife where OPE tissue residues levels appear to be strongly influenced by biotransformation. In the present study, the hepatic in vitro metabolism of six environmentally relevant organophosphate (OP) triesters and corresponding OP diester formation were investigated in East Greenland polar bears (PBs) and ringed seals (RSs). The in vitro metabolism assay results were compared to adipose levels in field samples from the same individuals. In vitro OP triester metabolism was generally rapid and structure-dependent, where PBs metabolized OPEs more rapidly than RSs. Exceptions were the lack of triethyl phosphate (TEP) metabolism and slow metabolism of tris(2-ethylhexyl) phosphate (TEHP) in both species. OP diester metabolites were also formed with the exception of TEP which was not metabolized at all. Tris(1,3-dichloro-2-propyl) phosphate was completely converted to its corresponding diester. However, the mass balances showed that OP diester formation corresponding to TEHP, tri(n-butyl) phosphate, and tris(2-butyoxyethyl) phosphate did not account for 100% of the OP triester depletion, which indicated alternate pathways of OP triester metabolism had occurred. Triphenyl phosphate was completely converted to its OP diester metabolite in PBs but not in RSs suggesting species-specific differences. The results demonstrated that OP triester bioaccumulation and fate in PBs versus their RS prey is substantially influenced by biotransformation.

Organophosphate esters flame retardants in the indoor environment

Concentrations of 13 organophosphate ester flame retardants (OPEs) were measured in air, dust and window wipes from 63 homes in Canada, the Czech Republic and the United States in the spring and summer of 2013 to look for abundances, differences among regions, and partitioning behavior. In general, we observed the highest concentrations for halogenated OPEs, particularly TCEP, TCIPP and TDCIPP, and also non-halogenated TPHP. Differences between regions strongly depended on the matrix. The concentrations of OPEs in dust were significantly higher in the US than in Canada (CAN) and Czech Republic (CZ). CZ had the highest concentrations in window film and CAN in air. ΣOPE concentrations were 2-3 and 1-2 orders of magnitude greater than ΣBFRs in air, and dust and window films, respectively. We found a significant relationship between the concentrations in dust and air, and between the concentrations in window film and air for OPEs with log K_OA values <12, suggesting that equilibrium was reached for these compounds but not for those with log K_OA>12. This hypothesis was confirmed by a large discrepancy between values predicted using a partitioning model and the measured values for OPEs with log K_OA values >12.

Organophosphate ester flame retardants and plasticizers in human placenta in Eastern China

Organophosphate esters (OPEs) have been widely used in various products as alternatives to brominated flame retardants. Although widespread OPE exposure is expected in humans, the accumulation of OPEs has seldom been studied in the human body. In this study, 12 OPE analogs were analyzed in 50 human placentas collected in Eastern China. The concentrations of the 9 most frequently detected OPEs (Σ9OPEs) ranged from 34.4 to 862ng/g lipid weight (lw), with a median of 301ng/g lw. Tri(2-chloroethyl) phosphate (TCEP) was identified as the most abundant analog, with a median concentration of 142ng/g lw, followed by tributoxyethyl phosphate (TBEP) and triphenyl phosphate (TPhP). Statistical analysis showed no analog of OPEs or Σ9OPEs was positively correlated with the lipid content of the placentas. There were no correlations observed between the OPE concentrations and maternal characteristics. Food consumption habits exhibited weak effects on OPE levels in the placentas. Further investigation is required to determine the effects of OPEs on fetuses due to the expected increase in maternal exposure to these esters.

Tris(pentafluoroethyl)trifluorophosphate-basd ionic liquids as advantageous solid-phase micro-extraction coatings for the extraction of organophosphate esters in environmental waters

Ionic liquids (ILs) containing the tris(pentafluoroethyl)trifluorophosphate [FAP] anion and various cations have great potential in sample preparation because of their excellent hydrophobicity, thermostability and low hydrolysity. In the present study, a [FAP]-based IL, 1-hexyl-3-methylimidazolium tris (pentafluoroethyl) trifluoro phosphate ([HMIM][FAP]), was used as coatings of solid-phase microextraction (SPME) for extracting organophosphate esters (OPEs) from environmental water samples. This SPME fiber was fabricated by coating a stainless steel wire substrate with [HMIM][FAP] via a simple direct dip-coating approach, and the extraction was conducted by the direct immersion solid phase microextraction. Coupling to gas chromatography mass spectrometry (GC-MS), the developed SPME method exhibited excellent selectivity and sensitivity towards the extraction of 11 OPEs from aqueous samples. Satisfactory linearity (R(2)≥0.99) of the calibration curves was obtained over the range of 0.05-50.0ngmL(-1) with the limits of detection (LODs, S/N=3) and limits of quantification (LOQs, S/N=10) ranged from 0.13-7.40ngL(-1) and 0.50-24.0ngL(-1), respectively. The proposed SPME method showed excellent extraction efficiency to OPEs with enrichment factors in the range of 168-2603, and acceptable reproducibility with relative standard deviations (RSDs) ≤15% for single fiber (n=7) and ≤16% for fiber-to-fiber (n=3×3) at a concentration level of 0.5ngmL(-1), respectively. The prepared IL-based fiber was successfully applied to determine eleven common used OPEs in tap water, influent and effluent of sewage treatment plant, with results are comparable to those determined by the reference (UPLC-MS/MS), and spiked recoveries in the range of 84.0-108%, 82.1-123% and 82.8-100%, respectively.

Occurrence, distribution and seasonal variation of organophosphate flame retardants and plasticizers in urban surface water in Beijing, China

The occurrence, spatial distribution and seasonal variation of 14 organophosphate esters (OPEs) were investigated in urban surface water (river and lake water) from July 2013 to June 2014 in Beijing, China. Sewage influent and effluent samples, as well as rainwater and road runoff samples were also analyzed as the potential sources of OPEs in surface water. Tris(2-chloro-1-methylethyl) phosphate (TCPP) and tris(2-chloroethyl) phosphate (TCEP) were the most abundant OPEs with the average concentrations of 291 ng L(-1) and 219 ng L(-1), respectively. Relatively high concentrations of OPEs were detected in rivers located at southern and eastern urban of Beijing, which was probably attributed to the treated and untreated sewage discharge. Besides, higher levels of OPEs were observed in urban surface water in the summer, and the wet deposition (rainfall) was confirmed to be an important factor for this observation. Risk assessment showed low or medium risk of OPEs for the organisms (algae, crustacean and fish).