Occurrence, phase distribution, and bioaccumulation of organophosphate esters (OPEs) in mariculture farms of the Beibu Gulf, China: A health risk assessment through seafood consumption

Transcriptomics-based analysis of neurotoxic and reproductive effects in turbot (Scophthalmus maximus) after exposure to tris (2-chloroethyl) phosphate (TCEP)

BACKGROUND

Tris (2-chloroethyl) phosphate (TCEP), a widely used flame retardant, is widespread in the environment and potentially harmful to organisms. However, the specific mechanisms of TCEP-induced neurological and reproductive toxicity in fish are largely unknown. Turbot (Scophthalmus maximus) is cultivated on a large scale, and the emergence of pollutants with endocrine disrupting effects seriously affects its economic benefits. This study aimed to investigate the toxic effects of TCEP on turbot by integrating physio-biochemical and transcriptomic analyses.

RESULTS

TCEP exposure induced severe neuroendocrine disrupting effects in turbot. Firstly, the hormone levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH), estradiol (E2), and 11-ketotestosterone (11-KT) were significantly decreased under prolonged TCEP stress, which may have a negative impact on normal reproductive function. We identified and summarized representative differentially expressed genes (DEGs) and their functions, such as endocrine system and oxidative stress. Pathway enrichment showed that the toxicological characteristics of TCEP on turbot were neuroendocrine regulation disorders, including oxidative phosphorylation, apoptosis, steroid biosynthesis, GnRH signaling pathway and so on. Weighted gene co-expression network analysis (WGCNA) also revealed key genes involved in these pathways. Among these genes, those encoding the components of the electron transport chain presented an initial increase in expression followed by a decrease, indicating that TCEP stress might affect mitochondrial function and lead to cell damage. This finding was also supported by the upregulation of apoptosis-related gene expression. Moreover, acute exposure to TCEP regulated MAPK-mediated transduction and regulation of GnRH signaling, thereby altering the expression of hypothalamic-pituitary-gonadal (HPG) axis-related genes.

CONCLUSIONS

These findings revealed the endocrine disrupting effects of TCEP on turbot and identified biomarkers related to reproductive toxicity, providing early warning for the monitoring of healthy aquaculture.

Degradation of organophosphate flame retardants by white-rot fungi: Degradation pathways and associated toxicity

The environmental persistence of organophosphate flame retardants (OPFRs) in water is becoming and environmental concern. White Rot Fungi (WRF) have proven its capability to degrade certain OPFRs such as tributyl phosphate (TBP), tris(2-butoxyethyl) phosphate (TBEP), tris(2-chloroethyl) phosphate (TCEP) and tris(2-chloroisopropyl) phosphate (TCPP). Despite this capability, there is limited knowledge about the specific pathways involved in the degradation. In this study, three different WRF were paired with individual OPFRs, and potential transformation products (TPs) were identified by UHPLC-HRMS. Some compounds structures were further validated by NMR. From these data degradation pathways were proposed. TBP was degraded by successive hydroxylation and hydrolysis reactions, with a novel dehydrogenation step suggested. Both TCEP and TCPP underwent oxidative dechlorination, with TCEP experiencing subsequent hydrolysis. Uncommon reductive dehalogenation was also observed. TCPP further underwent hydroxylation and environmentally relevant methylation. TBEP generated numerous TPs, mainly by successive dealkylations, along with hydroxylation. Notably, demethylation in TBEP degradation was proposed for the first time. Additional secondary products were formed through hydroxylation and oxidation of the initial metabolites. Finally, in vivo and in silico toxicity assessments were conducted, identifying certain TPs as potentially toxic.

Pollution characteristics and risk assessment of organophosphate esters in mollusks along the coast of South China

Organophosphate esters (OPEs) are emerging pollutants and used extensively in industrial production as alternative to the traditional flame retardants. This study investigated the contamination characteristics and health risks of OPEs in 104 mollusks from 15 cities along the coastal region of South China. Σ8OPEs ranged from 48.2 to 1937 ng/g dw, with a mean value of 295 ng/g dw. TDCIPP, TCPP, and TCEP were the dominant OPEs. Different spatial distributions were observed, with higher concentrations in Guangdong Province. A statistically positive but non-significant linear correlation was found between the trophic level of mollusk and OPEs concentration. The trophic magnification factors were >1, suggesting that OPEs have the potential to biomagnify in mollusks. OPEs in mollusks pose low non-carcinogenic and carcinogenic risks to consumers. This study provides an important basis for managing the safety risks associated with OPEs in mollusks.

Joint probabilistic risk of organic micropollutants in the aquaculture seawater around Liaodong Peninsula

The limited number of organic micropollutants (OMPs) investigated in aquaculture seawater may underestimate the risk to marine organisms. It is critical to comprehensively investigate the occurrence of diverse OMPs in mariculture area and assess their joint risks to coastal marine organisms. Herein, the joint risks caused by multiple substances were assessed based on the screened results of approximately 1300 non-polar to polar OMPs in the seawater of mariculture ponds and raft culture areas around Liaodong Peninsula. In this study, 48 out of 886 non-polar to low-polar OMPs were detected at least once in 36 seawater samples, including 16 alkanes, 6 phthalate esters, 6 pesticides, 5 polycyclic aromatic hydrocarbons, etc. For 99 detected OMPs from both this study and our previously reported study, their aquatic toxicity data were comprehensively collected to assess the probabilistic risk. For 14 OMPs with sufficient toxicity data, their species sensitivity distribution curves were established. The results show that only three pollutants - ametryn, atrazine and diuron - alone adversely affect >5 % of coastal marine organisms. However, for the joint risks, up to 15.2 % of coastal marine organisms were affected by 14 OMPs under long-term exposure, suggesting that the OMP mixtures could enhance adverse effects. Although the ecological risks for most of compounds were acceptable, the joint risks of co-pollution by various OMPs cannot be ignored. The findings could support risk management of pollutants in aquaculture seawater, thereby contributing to the conservation of coastal marine biodiversity.

Organophosphate esters and their metabolites in eggs from Vietnam

Data on the occurrence of organophosphate tri-esters (tri-OPEs) and their metabolites (di-OPEs) in hen's eggs are scarce. Therefore, 200 egg samples were gathered in 2023 in Hanoi, Vietnam and analysed by UHPLC-Q-Exactive HRMS. The majority of these compounds were detected, with tris(2-ethylhexyl) phosphate (0.10-2.7 ng/g wet weight (ww)) and trihexyl phosphate (0.08-2.3 ng/g ww) being the most prevalent tri-OPEs. Significant differences in tri-OPE profiles were observed in egg samples from battery-cage and free-range farming (p < .05). Despite egg levels ranging from 0.05 to 11.2 ng/g ww, Σdi-OPE accumulation in yolk and egg white was not significantly different in (p > .05). Among di-OPEs, dibutyl phosphate was found at the highest levels in the egg white, while bis(2-ethylhexyl) phosphate had the highest levels in yolk. There was no carcinogenic human health risk associated with OPEs in eggs (HQs <1).

Dissolved PAHs in the Beibu Gulf and adjacent waters of the South China Sea: Physical and biochemical processes-driven distributional variations

Polycyclic aromatic hydrocarbons (PAHs) in semi-enclosed gulfs are influenced by physical and biochemical processes, which haven't been well understood. This study aims to investigate the spatial distribution and vertical profiles of dissolved PAHs in the Beibu Gulf (BG) and adjacent waters of the South China Sea, along with hydrological, meteorological, and biochemical variables. Particularly relevant are the effects of atmospheric pressure, salinity, ammonium, chlorophyll-a, as well as riverine inputs (RI), sea currents, and upwelling. In surface seawater, the total concentrations of eight dissolved PAHs (∑8PAHs) were 7.76 ± 2.16 ng/L, with a distribution pattern of western Guangdong waters (WGWs) > BG > Qiongzhou Strait (QS). ∑8PAHs in the northern BG (9.10 ± 2.00 ng/L) was significantly higher than that in the southern BG (6.65 ± 1.54 ng/L) (p < 0.01), suggesting that local anthropogenic activities and unique environmental characteristics significantly influenced PAHs distribution. In water column, PAHs in BG displayed enrichment in surface and bottom but decreased in medium water, while those in WGWs and QS decreased with increasing depth. Source apportionment concluded that PAHs in QS and WGWs were primarily from petroleum sources, and PAHs in BG were mainly from coal combustion. RI, combined with circulation, coastal current, and intrusion of SCS water influenced the surface PAHs distribution in BG, with eddy impacts observed. Specifically, regarding the surface PAHs distribution, differences in atmospheric pressure may influence the air-sea exchange of PAHs, especially positively affecting 4-ring PAHs. Salinity factors further corroborated the contribution of RI to 3-ring PAHs, followed by the regulation of PAHs through biological pumps (ammonia and chlorophyll-a). Moreover, upwelling-induced biodegradation and resuspension affected the vertical distribution of PAHs. While most PAHs posed a negligible risk, coking-generated fluorene posed a moderate risk to ecosystems due to changes in the energy structure, warranting further investigation into its toxicological impacts.

Characterization of volatile compounds in the water samples from rainbow trout aquaculture ponds eliciting off-odors: understanding locational and seasonal effects

The quality of water used in aquaculture ponds is one of the crucial factors influencing the smell and sensory properties of fish. The water samples were taken from the rainbow trout fish ponds from three different fish farms in three provinces in Türkiye in four different seasons. The samples were analyzed for the volatile components by employing HS-SPME/GC-MS. Seven different volatile groups including aldehydes, ketones, esters, alcohols, volatile phenols, terpenes and other aromatic substances were identified in the samples. Among these, aldehydes were found to be the most dominant. (E)-2-Heptenal, nonanal, acetophenone, and 2-ethyl-1-hexanol are thought to be responsible for the off-odors in the water that have the potential to cause off-odors in fish. It was also determined that the amounts of these compounds increases in winter due to lower water temperature. Fish producers should monitor water quality on a regular basis to prevent off-odor compounds that degrade fish quality.

Community-level risk assessments on organophosphate esters in the sediments from the Bohai Sea of China based on multimodal species sensitivity distributions coupled with the equilibrium partitioning method

Organophosphate esters (OPEs), increasingly used as alternatives to brominated flame retardants, are ubiquitous in the global aquatic environment. Despite their potential toxicological impact on ecosystems, community-level risk assessments for OPEs in sediments remain scarce. This study investigated OPE occurrences and composition characteristics in the Bohai Sea's sediments and appraised both individual and joint ecological risks posed by characteristic OPE homologs using ten commonly used species sensitivity distribution (SSD) models, integrating acute-to-chronic conversion and phase equilibrium partitioning. OPEs were detected across all sediment samples, with total concentrations ranging from 0.213 ng/g dry weight (dw) to 91.1 ng/g dw. The predominant congeners included tri-n-butyl phosphate (TnBP), triisobutyl phosphate (TiBP), tri(2-ethylhexyl) phosphate, tris(2-chloroethyl) phosphate (TCEP), tris(1-chloro-2-propyl) phosphate (TCPP), tris(1, 3-dichloro-2-propyl) phosphate (TDCIPP), and triphenylphosphine oxide. Best-fit SSD models varied among TnBP, TiBP, TCEP, TCPP, and TDCIPP, demonstrating Sigmoid, Burr III, Sigmoid, Burr III, and Burr III, respectively. The same parametric model demonstrated variability in the fitting process for different OPE congeners, which also happened to the fitting results of ten parametric models for the same specific characteristic congener, underscoring the necessity of employing multiple models for precise community-level risk assessments. Hazard concentrations for a 5% cumulative probability were 0.116 mg/L, 2.88 mg/L, 1.30 mg/L, 1.44 mg/L, and 1.85 mg/L for each respective congener. The resulting risk quotients (RQ) and overall hazard index (HI) were selected as criteria to assess the individual and joint ecological risks of OPEs in sediments from the Bohai Sea, respectively. RQ and HI were both below 0.1, indicating a low risk to the local ecosystems. Multi-model SSD analysis could provide refined data for community-level risk evaluation, offering valuable insights for the development of evidence-based environmental standards and pollution control strategies.

Organophosphate esters (OPEs) pollution characteristics, bioaccumulation and human consumption implication in wild marine organisms from the Yellow River Estuary, China

As the substitutes of polybrominated diphenyl ethers, organophosphate esters (OPEs) with high concentrations have accumulated in the estuaries, bays, and harbors. However, limited information is available about the OPEs in the estuary organism categories, especially under the multiple industrial pressure. This study investigated the occurrence, bioaccumulation and human consumption implication in wild marine organisms from the Yellow River Estuary, where located many petroleum and chemical manufacturing industries. This study found that concentrations of Σ13OPEs ranged from 547 ng/L to 1164 ng/L in seawater (median: 802 ng/L), from 384 to 1366 ng/g dw in the sediment (median: 601 ng/g dw), and from 419 to 959 ng/g dw (median: 560 ng/g dw) in the marine organisms. The congener compositions in the organisms were dominated by alkyl-OPEs (80.7 %), followed by halogenated-OPEs (18.8 %) and aryl-OPEs (0.5 %). Based on the principal component analysis, petrochemical pollution, and industrial wastewater discharge were distinguished as the main plausible sources of OPEs to the YRE ecosystem. Most OPEs had potential or strong bioaccumulation capacity on the organisms, with a positive correlation between log BAF (Bioaccumulation Factor) and log Kow of OPEs. The highest estimated daily intake value of OPEs was tri-n-propyl phosphate, exceeding 300 ng/kg·bw/day via consuming fish. The highest hazard quotients from OPEs ranged from 0.001 to 0.1, indicating a low risk to human health by consuming marine organisms in the YRE. As the consumption of OPEs increases year by year, the risks of OPEs still cannot be ignored.

Organophosphate esters and their metabolites in silver pomfret (Pampus argenteus) of the Vietnamese coastal areas: Spatial-temporal distribution and exposure risk

A large number of studies on organophosphate esters (tri-OPEs) in marine organisms have not assessed the simultaneous occurrence of tri-OPEs and their metabolites (di-OPEs) in these species. This research investigated the concentration and geographical distribution of 15 tri-OPEs and 7 di-OPEs in 172 samples of Pampus argenteus that were collected annually from 2021 to 2023 at three distinct locations along the Vietnamese coast. As a result, tri-OPEs and di-OPEs were detected in numerous fish samples, indicating their widespread spatial and temporal occurrence in marine fish and pointing out the importance of monitoring their levels. The tri-OPEs and di-OPEs ranged within 2.1-38.9 ng g-1 dry weight (dw) and 3.2-263.4 ng g-1 dw, respectively. The mean concentrations of tri-OPEs ranged from 0.4 (TIPrP) to 5.4 ng g-1 dw (TBOEP), with TBOEP and TEHP having the highest mean values. In addition, the profiles of tri-OPEs in fish exhibited a descending order: Σalkyl OPEs > ΣCl-alkyl OPEs > Σaryl OPEs. The di-OPEs, namely BEHP and DMP, had the highest mean levels, measuring 33.4 ng g-1 dw and 23.8 ng g-1 dw, respectively. Furthermore, there have been significant findings of strong positive correlations between di-OPEs and tri-OPE pairs (p < 0.05). It is worth noting that there is a noticeable difference in the composition of tri-OPEs between the North and other regions. Despite these findings, the presence of OPE-contaminated fish did not pose any health risks to Vietnam's coastal population.

Occurrence, distribution, and sources of organophosphate esters (OPEs) in the air of the Indo-China Peninsula Based on a Passive Air Monitoring Network

Organophosphate esters (OPEs) are a class of emerging and ubiquitous contaminants that are attracting increasing attention, and their large-scale use as flame retardants and plasticizers has led to their pervasive presence in the environment, although their broader impacts remain unknown. In this study, 11 OPEs were measured in the atmosphere of Southeast Asia and Southwest China during 2016. The ∑11OPEs were higher in this region (78.0-1670 pg/m3, mean 458 pg/m3) than in many remote areas, lower than in developed regions, and comparable to levels in many developing country cities. Generally, the ∑11OPEs were higher in urban (105-1670 pg/m3, mean 538 pg/m3) than in suburban (78.0-1350 pg/m3, mean 388 pg/m3). Seasonal variations of OPEs in the air were more pronounced in Cambodia and Laos, especially for Triphenyl Phosphate (TPHP). Seasonal variations of ∑11OPEs in most regions correspond to changes in temperature and rainfall. Biomass burning may be also a factor in facilitating OPE emissions from biomass materials or soil into the atmosphere of Southeast Asia. The random forest analysis showed that among these, rainfall had the greatest effect on the seasonal variation of atmospheric OPE concentrations, followed by biomass burning and temperature. The inter-regional variation of ∑11OPEs in Southeast Asia was related to population and economic development in each region. Airflow trajectories indicated that the OPEs in this region were mainly from local sources. The health risk assessment revealed that the inhalation exposure risks of OPEs to the residents in the study areas were very low during the sampling period, but may be increasing.

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.

Occurrence, bioaccumulation and trophodynamics of organophosphate esters in the marine biota web of Laizhou Bay, Bohai Sea

The trophodynamic of organophosphate esters (OPEs) has not been known well despite their widespread occurrence in the aquatic environments. In this study, ten species of crustacean, seven species of mollusk, and 22 species of fish were collected in the Laizhou Bay (LZB) to examine the occurrence, bioaccumulation, and trophic transfer, and health risk of eight traditional OPEs and three emerging oligomeric OPEs. The results showed that total concentration of OPEs was 2.04 to 28.6 ng g-1 ww in the muscle of crustacean, mollusk, and fish and 2.62 to 60.6 ng g-1 ww in the fish gill. Chlorinated OPEs averagely contributed to over 85% of total OPEs while oligomeric OPEs averagely accounted for approximate 4%. The average log apparent bioaccumulation factor (ABAF) ranged from - 0.4 L kg-1 ww for triethyl phosphate to 2.4 L kg-1 ww for resorcinol-bis (diphenyl) phosphate. Apparent trophic magnification factors (ATMF) of individual OPE were generally less than 1, demonstrating the biodilution effect of the OPEs in the organism web of LZB. Additionally, the log ABAF and ATMF of OPEs were significantly positively correlated to their log Kow but negatively correlated to their biotransformation rate constant (BRC). Therefore, the OPEs with high Kow and low BRC tend to more accumulate in the marine organisms. The health risks associated with OPEs through the consumption of the seafood from the bay were low, even at high exposure scenario.

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.

Organophosphate esters in edible marine fish: Tissue-specific distribution, species-specific bioaccumulation, and human exposure

Although growing evidences have proved the wide presence of organophosphate esters (OPEs) in marine environments, information on the tissue- and species-specific accumulation characteristics of these emerging pollutants in wild marine fish and the associated human exposure risks are currently lacking. Eleven OPEs were comprehensively investigated for their occurrence and tissue accumulation in 15 marine fish species and their living environment matrices (seawater and sediment) from the Beibu Gulf. The OPE concentrations were statistically higher in the liver (17.6-177 ng/g ww, mean 90.9 ± 52.1 ng/g ww) than those of muscle tissues (2.04-22.9 ng/g ww, mean 10.6 ± 5.6 ng/g ww). Tris (phenyl) phosphate (TPHP) was the most predominant OPE congeners in fish liver, and tris(2-chloropropyl) phosphate (TCIPP) and tris(2-chloroethyl) phosphate (TCEP) were dominant OPEs in the muscle. The results suggested different OPE profiles occurred between the tissues. The median logarithmic bioaccumulation factors (BAFs) of TPHP in the muscle and liver, and TCEP in muscle were higher than the regulatory benchmark value (BCF >3.7), indicating very strong bioaccumulation. Carnivorous benthic fish appear to potentially accumulate TPHP, while pelagic and omnivory fish tend to accumulate TCIPP and TCEP. Except for proteins and phospholipids, no significant relationships were found between OPE levels and other biological properties of the studied fish. The results implied that the species-specific accumulation of OPEs mainly attributed to habitat and feeding habit rather than the difference of biochemical composition among species. Metabolism may have a significant effect on the bioaccumulation of OPEs in marine fish. The dietary risks of OPEs for consumers in different age groups ranged from 2.02 × 10-4 to 3.01 × 10-3, indicating relatively low human exposure risks from fish consumption.

Tracing Organophosphate Ester Pollutants in Hadal Trenches─Distribution, Possible Origins, and Transport Mechanisms

Unraveling the mysterious pathways of pollutants to the deepest oceanic realms holds critical importance for assessing the integrity of remote marine ecosystems. This study tracks the transport of pollutants into the depths of the oceans, a key step in protecting the sanctity of these least explored ecosystems. By analyzing hadal trench samples from the Mariana, Mussau, and New Britain trenches, we found the widespread distribution of organophosphate ester (OPE) flame retardants but a complex transport pattern for the OPE in these regions. In the Mariana Trench seawater column, OPE concentrations range between 17.4 and 102 ng L-1, with peaks at depths of 500 and 4000 m, which may be linked to Equatorial Undercurrent and topographic Rossby waves, respectively. Sediments, particularly in Mariana (422 ng g-1 dw), showed high OPE affinity, likely due to organic matter serving as a transport medium, influenced by "solvent switching", "solvent depletion", and "filtering processes". Amphipods in the three trenches had consistent OPE levels (29.1-215 ng g-1 lipid weight), independent of the sediment pollution patterns. The OPEs in these amphipods appeared more linked to surface-dwelling organisms, suggesting the influence of "solvent depletion". This study highlights the need for an improved understanding of deep-sea pollutant sources and transport, urging the establishment of protective measures for these remote marine habitats.

Occurrence, distribution, sources, and risk assessment of organophosphate esters in typical coastal aquaculture waters of China

This study monitored 20 organophosphate esters (OPEs) in water and sediment from three typical mariculture bases (Yunxi Marine Ranching (YX), Hangzhou Bay (HZB), and Zhelin Bay (ZLB)) and Meiliang Bay (MLB) of Taihu Lake in China, focusing on the spatial distribution and sources of OPEs. Moreover, the occurrence and risk of OPEs in fishes from ZLB were evaluated. The ∑OPE concentrations in waters followed the order MLB (591 ng/L) > YX (102 ng/L) > HZB (70.0 ng/L) > ZLB (37.4 ng/L), with tri(1-chloro-2-propyl) phosphate (TCIPP), triethyl phosphate (TEP), and tri(2-chloroethyl) phosphate (TCEP) being the dominant OPEs. Significantly higher ∑OPE concentrations were found in sediment in MLB compared to the other three areas with similar levels. The decreasing concentrations of OPEs from nearshore to offshore areas in HZB and MLB indicated that terrigenous input is the main source of OPEs. The even distribution of OPEs in YX and ZLB combined with PCA analysis suggested ship traffic or aquaculture activities are also potential sources. The ∑OPE concentrations in fishes ranged from 0.551-2.45 ng/g wet weight, with TCIPP, tri-phenyl phosphate (TPHP), and TCEP being the main OPEs. Hydrophobicity was a key factor affecting the sediment-water distribution coefficients and the bioaccumulation factors of OPEs. The human exposure to OPEs through consumption of fishes from ZLB had a low health risk.

Influence of watershed characteristics and human activities on the occurrence of organophosphate esters related to dissolved organic matter in estuarine surface water

Organophosphate esters (OPEs) are widespread in aquatic environments and pose potential threats to ecosystem and human health. Here, we profiled OPEs in surface water samples of heavily urbanized estuaries in eastern China and investigated the influence of watershed characteristics and human activities on the spatial distribution of OPEs related to dissolved organic matter (DOM). The total OPE concentration ranged from 22.3 to 1201 ng/L, with a mean of 162.6 ± 179.8 ng/L. Chlorinated OPEs were the predominant contaminant group, accounting for 27.4-99.6 % of the total OPE concentration. Tris(2-chloroisopropyl) phosphate, tris(1,3-dichloro-2-propyl) phosphate, and tributyl phosphate were the dominant compounds, with mean concentrations of 111.2 ± 176.0 ng/L, 22.6 ± 21.5 ng/L, and 14.8 ± 14.9 ng/L, respectively. Variable OPE levels were observed in various functional areas, with significantly higher concentrations in industrial areas than in other areas. Potential source analysis revealed that sewage treatment plant effluents and industrial activities were the primary OPE sources. The total OPE concentrations were negatively correlated to the mean slope, plan curvature, and elevation, indicating that watershed characteristics play a role in the occurrence of OPEs. Individual OPEs (triisobutyl phosphate, tris(2-butoxyethyl) phosphate, tris(2-chloroethyl) phosphate, and tricresyl phosphate) and Σalkyl-OPEs were positively correlated to the night light index or population density, suggesting a significant contribution of human activity to OPE pollution. The co-occurrence of OPEs and DOM was also observed, and the fluorescence indices of DOM were found to be possible indicators for tracing OPEs. These findings can elucidate the potential OPE dynamics in response to DOM in urbanized estuarine water environments with intensive human activities.

Determinants of organophosphate esters exposure in pregnant women from East China

Organophosphate esters (OPEs) have been broadly used in various industrial and consumer products, resulting in global distribution and human exposure. Gestational exposure to OPEs may adversely affect the health of both pregnant women and their offspring. To better understand OPE exposure in pregnant women, our study determined eight urinary metabolites of major OPEs in pregnant women (n = 733) recruited at 12-16 weeks of gestation from Shanghai, China, and explored the determinants of OPE exposure among various sociodemographic characteristics, lifestyles, and dietary factors. Urinary metabolites of OPEs, including bis (1,3-dichloro-2-propyl) phosphate (BDCPP), bis (2-chloroethyl) phosphate (BCEP), bis (1-chloro-2-propyl) phosphate (BCIPP), dicresyl phosphate (DCP), diphenyl phosphate (DPP), dibutyl phosphate (DBP), bis (2-ethylhexyl) phosphate (BEHP), and bis (2-butoxyethyl) phosphate (BBOEP), exhibited a detection rate ranging from 69.30% to 99.32%. Multivariate linear regression models indicated that pregnant women who were multiparous, had a higher family income per capita, worked in white-collar jobs, and took nutritional supplements such as milk powder and fish oil tended to have higher urinary OPE metabolite concentrations. Besides, independent of sociodemographic characteristics and lifestyle factors, consumption of more aquatic products, soy products, pork, and puffed food, as well as drinking of purified tap water versus tap water, were associated with increased urinary OPEs metabolite concentrations. Our study demonstrated that OPE exposure was ubiquitous in pregnant women from Shanghai, and provided new insights into the potential factors influencing OPE exposure during pregnancy.

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.

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

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

Life-cycle exposure to tris (2-chloroethyl) phosphate (TCEP) causes alterations in antioxidative status, ion regulation and histology of zebrafish gills

Tris (2-chloroethyl) phosphate (TCEP) has been receiving great concerns owing to its ubiquitous occurrence in various environmental compartments and potential risks to wildlife and humans. Gill is structural basis for ion regulation and homeostasis in fish and susceptible to xenobiotics. However, current knowledge on the impacts of long-term exposure to TCEP on the structure and physiological function of fish gills are insufficient. In this work, zebrafish were exposed to environmental realistic concentrations (0.8, 4, 20 and 100 μg/L) of TCEP from 3 h post ferterlization (hpf) till 120 days post ferterlization (dpf). Our results demonstrated that life-cycle exposure to TCEP significantly decreased the activity of glutathione S-transferase (GST), but elevated the activities of antioxidative enzymes including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and increased malondialdehyde (MDA) content in zebrafish gills. Gene transcription analysis implied that the mRNA expressions of antioxidant-related genes (nrf2, cat and nqo1) were induced, while the transcription of gstα1, hmox1, keap1 were down-regulated, indicating that Nrf2-Keap1 pathway might be activated to defend the oxidative stress induced by TCEP. Additionally, the ion homeostasis was disrupted by TCEP exposure, evidenced by reduced activities of Na+/K+-ATPase (NKA), Ca2+-ATPase and Mg2+-ATPase and downregulated transcription levels of ncc, nkcc, cftr and clc-3. Besides, whole-life exposure to TCEP resulted in a series of structural damages to gills, including epithelial lifting, epithelial rupture, telangiectasis, vacuolation, edema and shortened gill lamellae. Overall, our results demonstrated that long-term TCEP exposure could induce oxidative stress, affect ion regulation and cause histological changes in zebrafish gills.

Effects of nitrogen stress on uptake and translocation of organophosphate esters by watermifoil (Myriophyllum aquaticum L.) in an aquatic ecosystem

Although organophosphate esters (OPEs) and nitrogen (N) are normally present in aquatic environments, the effects of the plant uptake, accumulation, and translocation of OPEs in different levels of N remain ambiguous. To better understand these processes, watermifoil (Myriophyllum aquaticum L.) as tested plant was chosen to investigate the effects of different N levels on the uptake and translocation of OPEs by plants in matched water-sediment-plant samples. After two months, we found the root-water concentration factors, root-sediment concentration factors, and translocation factors (TFs) were significantly changed with the levels of N (p < 0.05), implying that the presence of N could alter uptake, accumulation, and translocation of OPEs in M. aquaticum, particularly the process of root absorption. Low concentrations of N could remarkably promote the uptake of OPEs by M. aquaticum. However, when the concentrations of N in water were higher than 200 mg/L, the plants' growth and OPE accumulation by M. aquaticum were obviously inhibited with the elevated N contents. Moreover, the enrichment and environmental transport of OPEs in M. aquaticum seemed to be closely associated with physicochemical parameters; the octanol-water partition coefficient had significant relationships with measured organic carbon-normalized sediment-water partition coefficients and TFs in the present study. Additionally, the substituents and structures of OPEs could also affect the accumulation and translocation of OPEs in M. aquaticum, including the chlorination degree and alkyl chain length. This study could improve our understanding of uptake and translocation of OPEs in aquatic plants under different levels of N.

Higher ecological risks and lower bioremediation potentials identified for emerging OPEs than legacy PCBs in the Beibu Gulf, China

The production and use of organophosphate esters (OPEs) as substitutes for traditional halogenated flame retardants is increasing, resulting in greater global concern related to their ecological risks to marine environments. In this study, polychlorinated biphenyls (PCBs) and OPEs, representing traditional halogenated and emerging flame retardants, respectively, were studied in multiple environmental matrices in the Beibu Gulf, a typical semi-closed bay in the South China Sea. We investigated the differences in PCB and OPE distributions, sources, risks, and bioremediation potentials. Overall, the concentrations of emerging OPEs were much higher than those of PCBs in both seawater and sediment samples. Sediment samples from the inner bay and bay mouth areas (L sites) accumulated more PCBs, with penta- and hexa-CBs as major homologs. Chlorinated OPEs were prevalent in both seawater and sediment samples from the L sites, whereas tri-phenyl phosphate (TPHP) and tri-n-butyl phosphate (TNBP) were predominant at the outer bay (B sites) sediment samples. Source identification via principal component analysis, land use regression statistics, and δ13C analysis indicate that PCBs were mainly sourced from the atmospheric deposition of sugarcane and waste incineration, whereas sewage inputs, aquaculture, and shipping activity were identified as sources of OPE pollution in the Beibu Gulf. A half-year sediment anaerobic culturing experiment was performed for PCBs and OPEs, and the results only exhibited satisfactory dechlorination for PCBs. However, compared with the low ecological risks of PCBs to marine organisms, OPEs (particularly trichloroethyl phosphate (TCEP) and TPHP) exhibited low to medium threats to algae and crustaceans at most sites. Given their increasing usage, high ecological risks, and low bioremediation potential in enrichment cultures, pollution by emerging OPEs warrants close attention.

Health Risk Assessment of Organophosphate Flame Retardants in Soil Across China Based on Monte Carlo Simulation

Health risks from exposure to contaminants are generally estimated by evaluating concentrations of the contaminants in environmental matrixes. However, accurate health risk assessment is difficult because of uncertainties regarding exposures. This study aims to utilize data on the concentrations of organophosphate flame retardants (OPFRs) in surface soil across China coupled with Monte Carlo simulations to compensate for uncertainties in exposure to evaluate the health risks associated with contamination of soil with this class of flame retardants. Results revealed that concentrations of ∑OPFRs were 0.793-406 ng/g dry weight (dw) with an average of 23.2 ng/g dw. In terms of spatial distribution, higher OPFRs concentrations were found in economically developed regions. Although the values of health risk of OPFRs in soil across China were below the threshold, the high concentrations of OPFRs in soil in some regions should attract more attentions in future. Sensitivity analysis revealed that concentrations of OPFRs in soil, skin adherence factor, and exposure duration were the most sensitive parameters in health risk assessment. In summary, the study indicated that the national scale soil measurement could provide unique information on OPFRs exposure and health risk assessment, which was useful for the management of soil in China and for better understanding of the environmental fate of OPFRs in the global perspective.

Organophosphate esters (OPEs) in the marine environment: Spatial distribution and profiles in French coastal bivalves

Organophosphate esters (OPEs), chemicals widely used in industrial production, electronics and domestic products, have become ubiquitous environmental contaminants. In this study, the levels and spatial distribution of 11 OPEs (aryl, alkyl and halogenated) were investigated in over 100 samples of filter-feeding bivalves collected yearly between 2014 and 2021 at sites of contrasted pressure along the French coasts. OPEs were found in virtually all samples, indicating their widespread spatial and temporal occurrence in coastal bivalves and the relevance of their biomonitoring. The median concentrations were between 0.4 (TMPP) and 4.9 ng g-1 dry weight (TCIPP), with TCIPP, TNBP and EHDPP found at the highest median values. TCEP and TBOEP were not frequently detected overall, but each year, the same sites showed repeatedly high concentrations. Structurally-related OPEs generally correlated, but the geographical distributions were not predictable from known anthropogenic pressures (population in the catchment area, industry), with little comparability with other hydrophobic contaminants. If the relation between sources of OPEs and bioaccumulated levels remains uncertain, local hotspots, rather than riverine/atmospheric transportation, could account for their geographical distribution. A systematic review of the levels of OPEs found in filter-feeding bivalves worldwide revealed comparable levels in our study with those reported elsewhere; however, the levels across and within (when available) studies generally spanned several orders of magnitude, indicating high spatial and temporal heterogeneity. In view of the growing concerns regarding OPEs, this study provides essential reference data for future studies of their occurrence on European coasts and supports the need for a more systematic (bio)monitoring of this class of contaminant.

Occurrence and risk assessment of organophosphate esters in global aquatic products

Organophosphate esters (OPEs), as an important class of new pollutants, have been pervasively detected in global aquatic products, arousing widespread public concern due to their potential bioaccumulative behavior and consequent risks. With the continuous improvement of living standards of citizens, there have been constant increment of the proportion of aquatic products in diets of people. The levels of OPEs exposed to residents may also be rising due to the augmented consumption of aquatic products, posing potential hazards on human health, especially for people in coastal areas. The present study integrated the concentrations, profiles, bioaccumulation, and trophic transfer of OPEs in global aquatic products, including Mollusca, Crustacea, and fish, evaluated health risks of OPEs through aquatic products in daily diets by Mont Carol Simulation (MCS), and found Asia has been the most polluted area in terms of the concentration of OPEs in aquatic products, and would have been increasingly polluted. Among all studied OPEs, chlorinated OPEs generally showed accumulation predominance. It is worth noting that some OPEs were found bioaccumulated and/or biomagnified in aquatic ecosystems. Though MCS revealed relative low exposure risks of residents, sensitive and special groups such as children, adolescents, and fishermen may face more serious health risks than the average residents. Finally, knowledge gaps and recommendations for future research are discussed encouraging more long-term and systematic global monitoring, comprehensive studies of novel OPEs and OPEs metabolites, and more toxicological studies to completely evaluate the potential risks of OPEs.

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

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

Disinfection byproducts in indoor swimming pool water: Detection and human lifetime health risk assessment

Quantification of regulated and emerging disinfection byproducts (DBPs) in swimming pool water, as well as the assessment of their lifetime health risk are limited in China. In this study, the occurrence of regulated DBPs (e.g., trihalomethanes, haloacetic acids) and emerging DBPs (e.g., haloacetonitriles, haloacetaldehydes) in indoor swimming pool water and the corresponding source water at a city in Eastern China were determined. The concentrations of DBPs in swimming pool water were 1-2 orders of magnitude higher than that in source water. Lifetime cancer and non-cancer risks of DBPs stemming from swimming pool water were also estimated. Inhalation and dermal exposure were the most significant exposure routes related to swimming pool DBP cancer and non-cancer risks. For the first time, buccal and aural exposure were considered, and were proven to be important routes of DBP exposure (accounting for 17.9%-38.9% of total risk). The cancer risks of DBPs for all swimmers were higher than 10^-6 of lifetime exposure risk recommended by United States Environmental Protection Agency, and the competitive adult swimmers experienced the highest cancer risk (7.82 × 10^-5). These findings provide important information and perspectives for future efforts to lower the health risks associated with exposure to DBPs in swimming pool water.

Emissions and fate of organophosphate esters in outdoor urban environments

Cities are drivers of the global economy, containing products and industries that emit many chemicals. Here, we use the Multimedia Urban Model (MUM) to estimate atmospheric emissions and fate of organophosphate esters (OPEs) from 19 global mega or major cities, finding that they collectively emitted ~81,000 kg yr^-1 of ∑₁₀OPEs in 2018. Typically, polar "mobile" compounds tend to partition to and be advected by water, while non-polar "bioaccumulative" chemicals do not. Depending on the built environment and climate of the city considered, the same compound behaves like either a mobile or a bioaccumulative chemical. Cities with large impervious surface areas, such as Kolkata, mobilize even bioaccumulative contaminants to aquatic ecosystems. By contrast, cities with large areas of vegetation fix and transform contaminants, reducing loadings to aquatic ecosystems. Our results therefore suggest that urban design choices could support policies aimed at reducing chemical releases to the broader environment without increasing exposure for urban residents.

Organophosphate esters (OPEs) in a coral reef food web of the Xisha Islands, South China Sea: Occurrence, trophodynamic, and exposure risk

Despite organophosphate esters (OPEs) are widely prevalent in the environment, however, limited information is available regarding their occurrence, trophodynamics, and exposure risks in coral reef ecosystems. In this study, 11 OPEs were investigated in a tropical marine food web (7 fish species and 9 benthos species) from the Xisha (XS) Islands, South China Sea (SCS). The ∑₁₁OPEs were 1.52 ± 0.33 ng/L, 2227 ± 2062 ng/g lipid weight (lw), 1024 ± 606 ng/g lw, and 1800 ± 1344 ng/g lw in seawater, fish, molluscs, and corals, respectively. Tris (2-chloroisopropyl) phosphate (TCIPPs) were the dominant OPEs in seawater, fish, and molluscs, while tris (2-butoxyethyl) phosphate (TBOEP) predominated in coral tissues. Abiotic and biotic factors jointly affect the OPEs enrichment in marine organisms. Trophic magnification factors (TMFs) (range: 1.31-39.2) indicated the biomagnification potency of OPEs. A dietary exposure risk assessment indicated that OPEs at current levels in coral reef fish posed a low risk to human health but were not negligible. Overall, this study contributes to a further understanding of the environmental behaviors of OPEs in coral reef ecosystems.

Bioaccumulation of organophosphorus flame retardants in marine organisms in Liaodong Bay and their potential ecological risks based on species sensitivity distribution

Although organophosphorus flame retardants (OPFRs) in aquatic environments have received increasing concern, little information is available on their bioaccumulation and trophic transfer in marine food webs. Consequently, the risks of OPFRs to marine ecosystems are unknown. In this study, seven OPFR compounds in marine biological samples collected from Liaodong Bay, Bohai Sea, were analyzed to evaluate their level and biological amplification effect in the marine food web. The total OPFRs of marine organisms in Liaodong Bay ranged from 2.60 to 776 ng/g ww, and lipids were critical factors affecting the concentration of OPFRs in marine species. Tris (2-ethylhexyl) phosphate (TEHP) and tris(1-chloro-2-propyl) phosphate (TCIPP) were the OPFRs most frequently detected in marine species. Still, tris(2-chloroethyl) phosphate (TCEP) was dominant in most marine species (16/24), and the content of chlorinated OPFRs was highest. At the same time, alkyl OPFRs and aryl OPFRs accounted for the same proportion. No correlation between OPFR concentration and the trophic level was observed in marine organisms from Liaodong Bay. It was shown in the results of the species sensitivity distribution that TCIPP in Chinese seawater does not pose a potential ecological risk to marine species. However, much work remains to be done on accumulating information and the ecological risks of OPFRs in different marine food webs.

Organophosphate esters in UK diet; exposure and risk assessment

Food ingestion has been established as an important human exposure route to many environmental contaminants (brominated flame retardants, dioxins, organochlorine pesticides etc). However, information regarding dietary exposure to organophosphate esters (OPEs) in the UK remains limited. This study provides the first comprehensive dataset on OPEs in the UK diet by measuring concentrations of eight OPEs in 393 food samples, divided into 15 food groups, collected from Birmingham, UK. All target OPEs were measured above the limit of quantification in at least one of the food groups analysed. Concentrations were highest (mean ∑₈OPEs = 18.4 ng/g wet weight (ww)) in milk and milk products, followed by those in cereal and cereal products (mean ∑₈OPEs = 15.9 ng/g ww), with concentrations lowest in chickens' eggs (mean ∑₈OPEs = 1.61 ng/g ww). Interestingly, concentrations in animal-derived foods (mean ∑₈OPEs = 44.2 ng/g ww) were statistically indistinguishable (p˃0.05) from plant-derived foods (mean ∑₈OPEs = 36.8 ng/g ww). Estimated daily dietary intakes (EDIs) of ∑₈OPEs under mean and high-end exposure scenarios for the four age groups considered were: toddlers (420 and 1547 ng/kg bw/day) ˃ children (155 and 836) ˃ elderly (74.3 and 377) ˃ adults (62.3 and 278) ng/kg bw/day, respectively. Baby food contributed 39 % of ∑₈OPEs exposure for toddlers, with non-alcoholic beverages contributing 27 % of exposure for children, while cereal and cereal products (25 %) and fruits (22 %) were the main contributors for adults and the elderly. The concentrations of OPEs in UK foodstuffs were generally of the same order of magnitude as those reported for other countries and our estimates of dietary exposure were well below the corresponding health-based limit values.

Distribution, sources, and ecological risk of organophosphate esters in the urbanized Jiaozhou Bay, East China

Organophosphate esters (OPEs), substitutes of polybrominated diphenyl ethers, have been found in a variety of marine environmental matrices, whereas little is known about the feature and sources of seawater OPEs from the environments simultaneously affected by multiple anthropogenic activities. Jiaozhou Bay is one typical bay heavily disturbed by human activities, which was semi-enclosed and surrounded by large amounts of discharged rivers and catchments, various types of ports, and aquaculture farms. This study found that concentrations of Σ₁₃OPEs ranged from 23.90 to 366.40 ng/L (median: 37.76 ng/L) in the seawater and from 90.15 to 1183.14 ng/L (median: 940.61 ng/L) in the inflowing river water. Tris (2-chloroisopropyl) phosphate, triethyl phosphate, and tris (2-chloroethyl) phosphate were the predominant congener, with the percentage of 43.76%, 22.80%, and 14.01%, respectively, in the bay water and 52.47%, 11.31%, and 23.66% in the river water. The overall spatial distribution was characterized by a higher concentration of Σ₁₃OPEs and halogenated-OPEs in the nearshore sites and in the inflowing rivers, which were surrounded by urbanized areas with dense anthropogenic activities, especially along the eastern coast. Effluent discharge and vehicular and marine traffic emissions were distinguished as two main plausible sources of OPEs to Jiaozhou Bay, based on the principal component analysis and Spearman correlations. Ecological risk analysis indicated that Σ₁₃OPEs posed a low risk to aquatic organisms in the bay and low-to-medium risks in the inflowing rivers.

Simulation modelling the structure related bioaccumulation and biomagnification of per- and polyfluoroalkyl substances in aquatic food web

Until now, there is no bioaccumulation model to predict bioaccumulation of polyfluoroalkyl substances (PFASs) in aquatic organisms due to their unique amphiphilic properties. For the first time, protein contents instead of lipid contents of organisms were used in bioaccumulation models to predict the concentrations and reveal the accumulation mechanisms of PFASs in various aquatic organisms, based on the available data. Comparison between the modeled and measured results indicated the models were promising to predict the PFAS concentrations in the fishes at different trophic levels very well, as well as their bioaccumulation factors (BAF) and trophic magnification factors (TMF) of PFASs in fish. Both water and sediment are important exposure sources of PFASs in aquatic organisms. As the two main uptake pathways, the contribution of gill respiratory decreases while that of dietary intake increases with the chain length of PFASs increasing. Fecal excretion and gill respiration are the main pathways for fish to eliminate PFASs, and their relative contributions increase and decrease respectively with chain length. The short-chain (C6-C8) perfluoroalkyl acids (PFAAs) are greatly eliminated via gill respiratory quickly, leading to their very low BAFs. As the carbon chain length increases, dietary intake becomes dominant in the uptake, while elimination is mainly through fecal excretion with relatively low rates, especially in the fishes with high protein contents. For the very long chain (C12-C16) PFASs, they are very difficult to excrete with a low total elimination rate constant (k_e = 0.463-0.743 d^-1), thus leading to their high BAFs and TMFs. The high intake rate but low elimination rate, as well as the high water and sediment concentrations together contribute to the highest accumulated concentration perfluorooctane sulfonic acid in the fish of Taihu Lake.

Organophosphate esters in the mariculture ecosystem: Environmental occurrence and risk assessments

Most investigations on organophosphate esters (OPEs) are conducted predominantly in a separate biological or abiotic medium, and few joint analyses have been performed in the mariculture ecosystem based on yearly sampling. Herein, we investigated the occurrence, load estimation, phase distribution, source diagnostics, and risks of 20 OPEs in seawater, sediment, and aquaculture organisms from a typical mariculture area in China. The total of these OPEs (∑_OPEs) ranged within 3.97-1068 ng/L, 0.39-65.5 ng/g (dw), and 4.09-16.3 ng/g (ww) in seawater, sediment and organisms, respectively. Chlorinated OPEs were the predominant congeners detected in seawater, whereas alkyl-OPEs were the leading contributors in sediment and biological samples. Seasonal variations of ∑_OPEs in seawater were more distinct than those in sedimentary environments. Load estimation indicated that approximately 70% of the OPEs in the study area existed in the water bodies. Source identification performed using the U.S. EPA positive matrix factorization indicated that polyurethane foam/plastics and hydraulic oil made the greatest contributions in seawater, whereas chemical production was the predominant source in sediment. Indices of ecological and health risks of OPEs were lower than their risk threshold, indicating that the OPEs detected in this study posed a low risk to the aquatic environment and human health.

Suspect and nontarget screening of known and unknown organophosphate esters (OPEs) in soil samples

Ninety-five soil samples (n = 95) were analyzed using an integrated suspect and non-target organophosphate ester (OPE) screening strategy. This suspect and non-target screening strategy allowed us to fully or tentatively identify 26 OPEs or OPE-like substances. Among these 26 newly identified contaminants, bisphenol A bis(diphenylphosphate) (BPABDP) exhibited the highest detection frequency of 83.2 %, with a concentration range of ND - 385 ng/g dry weight (dw). We also observed that BPABDP was significantly correlated with all other OPEs (p < 0.001 in all pairs), suggesting that BPABDP is widely used as a plasticizer and flame retardant in various commercial products. Another interesting finding was the discovery of four novel OPE structures with tentatively proposed chemical structures. Among these four non-target OPEs, (tert-butyl) phenyl bis(2,4-di-tert-butylphenyl) phosphate (TBPBDTBPP) shared a backbone structure very similar to that of the well-known OPE, tris(2,4-di-tert-butylphenyl) phosphate (TDTBPP). Detection frequency of this newly discovered OPE was high, up to 69.5 %, and it was significantly correlated with isodecyl diphenyl phosphate (IDDP), BPABDP, diphenyl 2-isopropylphenyl phosphate (2IPPDPP), and tricresyl phosphate (TCrP, p < 0.05 in all pairs), respectively. This study reported the most comprehensive suite of OPEs in soil samples, and 16 out of them were recognized in soil for the first time.

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.

Inter-annual variation and comprehensive evaluation of organophosphate esters (OPEs) in the Yellow Sea, China

Considering the extensive production and continuous usage of organophosphate esters (OPEs) around the urbanized coasts in recent years, the inter-annual variation and the ecological risks of OPEs in the Yellow Sea (YS), China were systematically evaluated in summer 2015 and 2019. The major component of OPEs, halogenated-OPEs in 78 surface and bottom seawater samples collected from 39 locations in the YS in 2019 were compared with 62 samples at 31 sites conducted in the same periods and similar stations in 2015. The average concentration of halogenated-OPEs increased 1.57, 2.50 folds in the surface and bottom seawater, respectively, in recent 5 years. The proportion of TCPP to halogenated-OPEs exhibited an increasing trend from 56.49% in 2015 to 79.95% in 2019. The peak values of halogenated-OPEs changed from the nearshore regions (33°N-38°N) in 2015 to the nearshore and offshore regions (33°N-35°N) in 2019, implying the growing terrigenous emission sources, especially some large OPEs producers nearby the coastal zones in the northern area of Jiangsu province. The targeted halogenated-OPEs posed no significant or low ecological risks to the aquatic organisms in 2015 and 2019, however, the values of RQ showed an elevated trend in 2019. Therefore, the ecological risks of OPEs in this region still need continuous concern due to the gradually increasing OPEs usage and production.

Spatial-temporal evolution of agricultural ecological risks in China in recent 40 years

Excessive use of agricultural chemicals and unreasonable utilization of agricultural wastes have led to severe agricultural non-point source pollution (ANPSP) problems in China. Based on the agricultural pollution loads and pollution control strength, the ecological risk index (ERI) was constructed and was used to explore the spatial-temporal pattern of agricultural ecological risks in China during 1978-2017. The findings indicated that Chinese agricultural ERI was gradually increased from 0.031 to 0.348 in 1978-2017, which has the same phased change characteristics as the succession of agricultural policies. At present, the ecological risk grade of ANPSP was present in the stair-step distribution characteristics of "high in the east and south and low in the west and north" as a whole. Southern China, as the main producing area of aquatic products, had the higher ecological risks. Northeastern China, the Huang-Huai-Hai Area, and the middle and lower reaches of the Yangtze River, as the grain-producing bases, had moderate ecological risks, but Southwestern China and Northwestern China with the poor agricultural production conditions had the lower ecological risks. It evidently showed that the ecological risk problems faced by the high-quality development of Chinese agricultural industrialization are increasingly severe.

Determination of multiple organic flame retardants in maricultural water using High-volume/High-throughput Solid-phase extraction followed by liquid/gas chromatography tandem mass spectrometry

A rapid and efficient analytical method is proposed and optimized for the enrichment, extraction and instrument analysis of four typical organic flame retardants (OFRs), including organophosphate esters (OPEs), polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCDs) and dechlorane compounds (Dechloranes) in maricultural waters using High-volume/High-throughput Solid-phase extraction with in-situ ultrasonic technique followed by high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) and gas chromatography tandem mass spectrometry (GC-MS) instrumental detection. The optimized pretreatment conditions were that the analytes were enriched by XAD-2 resins and eluted repeatedly with 50 mL hexane/acetone (1:1, v:v) for 5 min. The results of method validation exhibited that the developed method can be used for quantitative detection of 11 OPEs, 13 PBDEs, 3 HBCDs and 5 Dechloranes in water samples. The method detection limits (MDLs) and limits of quantification (LOQs) are 0.4-26.2 pg/L and 1.5-87.4 pg/L for OPEs, 23.3-35.4 pg/L and 77.5-117.9 pg/L for HBCDs, 0.8-97.4 pg/L and 2.6-324.7 pg/L for PBDEs and 9.3-78.5 pg/L and 31.0-261.8 pg/L for Dechloranes, respectively. The method was successfully applied in lagoon maricultural areas in Hainan province, and the results showed that 4 OFRs were detected in almost all water samples. Total concentrations of 18 water samples were 1.89-39.97 ng/L for OPEs, 0.18-5.40 ng/L for PBDEs, ND-0.24 ng/L for HBCDs and 0.01-1.77 ng/L for Dechloranes, respectively. The optimized analytical method is highly sensitive and efficient with expectation to play an essential role in monitoring the ultra-trace organic pollutants and providing an effective risk assessment in ecological environment.

Heavy metal accumulation and health risk assessment of crayfish in the middle and lower reaches of Yangtze River during 2015-2017

This study performed statistical analysis and risk assessment of five heavy metals (As, Cd, Cr, Hg, Pb) in crayfish samples collected from six provinces in the middle and lower reaches of Yangtze River during 2015-2017. The Spearman correlation test and the results of hierarchical cluster analysis (HCA) indicated that As, Pb, and Cd in crayfish were significantly correlated, and the results of HCA showed that Jiangxi, Jiangsu, and Zhejiang were clustered into one group; Hubei, Hunan, and Anhui were clustered into another group; and provinces in the same group had spatial similarities in heavy metals. The pollution index (PI) values of five heavy metals in all provinces were below 1, implying that crayfish samples in this area were not highly contaminated. The target hazard quotient (THQ) values of five heavy metals were mainly below 1 except Hg in Anhui (2.9709), which was far beyond 1, indicating that the health risk posed by Hg exposure should not be ignored in Anhui.

Effects of polystyrene and triphenyl phosphate on growth, photosynthesis and oxidative stress of Chaetoceros meülleri

The toxicity of microplastics to marine organisms has attracted much attention; however, studies of their effects on marine microalgae remain limited. Here, the effects of the single and combined toxicity of polystyrene (PS) and triphenyl phosphate (TPhP) on the cell growth, photosynthesis, and oxidative stress of Chaetoceros meülleri were investigated. PS inhibited growth of the algae cells and caused a dose-dependent effect on oxidative stress. The significantly high production of reactive oxygen species (ROS) induced severe cell membrane damage, as confirmed by high fluorescence polarization. However, there was no obvious decrease in chlorophyll a content, and 80 mg/L of PS significantly promoted chlorophyll a synthesis. The TPhP also inhibited cell growth, except at low concentrations (0.2-0.8 mg/L), which stimulated algae growth over 48 h. Moreover, no obvious decrease in chlorophyll a and maximal photochemical efficiency of PSII was found in the TPhP experimental groups except for 3.2 mg/L TPhP, where the rapid light curves showed a significantly reduced photosynthetic capacity of algae. In addition, TPhP caused high ROS levels at 96 h, resulting in cell membrane damage. Using the additive index and independent action methods, the combined toxic effects of PS and TPhP on the algae were evaluated as antagonistic; however, cell membrane damage caused by high ROS levels was still noticeable. This study has shown the potential toxicity of PS and TPhP to marine microalgae, and provided insights into the combined risk assessment of TPhP and microplastics in the marine environment.

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.

A review on organophosphate flame retardants in the environment: Occurrence, accumulation, metabolism and toxicity

Organophosphate flame retardants (OPFRs), as a substitute for brominated flame retardants (BFRs), are widely used in industrial production and life. The presence of OPFRs in the environment has an adverse effect on the ecological environment system. This review provides comprehensive data for the occurrence of OPFRs and their diester metabolites (OP diesters) in wastewater treatment plants, surface water, drinking water, sediment, soil, air and dust in the environment. In particular, the accumulation and metabolism of OPFRs in organisms and the types of metabolites and metabolic pathways are discussed for animals and plants. In addition, the toxicity of OP triesters and OP diesters in organisms is discussed. Although research on OPFRs has gradually increased in recent years, there are still many gaps to be filled, especially for metabolic and toxicity mechanisms that need in-depth study. This review also highlights the shortcomings of current research and provides suggestions for a basis for future research on OPFRs.

Organophosphorus flame retardants (OPFRs) in the seawater and sediments of the Qinzhou Bay, Northern Beibu Gulf: Occurrence, distribution, and ecological risks

The occurrence, distributions, and ecological risks of 11 organophosphate flame retardants (OPFRs) were investigated in the seawater and sediment samples from the Qinzhou Bay. The Σ₁₁OPFRs in the surface seawater and sediments ranged from 150 to 885 ng/L and from <the limit of quantification (LOQ) to 32.2 ng/g dw, respectively, with high levels of OPFRs in the industrialized and port areas. Tris (2-chloro-propyl) phosphate (TCIPP), tris (2-chloroethyl) phosphate (TCEP), and tri-n-butyl phosphate (TNBP) were the dominant OPFRs in the surface seawater and sediments. The Σ₁₁OPFRs concentrations in the sediment core ranged 1.2-18.6 ng/g dw and the vertical trends showed a recent increase of OPFRs emissions, especially for TNBP and triphenyl phosphate (TPHP). Risk assessment revealed that individual OPFR could pose low to medium ecological risks, but the risk from the mixture of OPFRs on aquatic organisms requires more attention.

Human health risk assessment of selected metal(loid)s via crayfish (Faxonius virilis; Procambarus acutus acutus) consumption in Missouri

Farmed crustaceans are an important component in addressing the rising animal protein demand. The present study determined the concentrations of fourteen elements (Ag, As, Be, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Sn, Pb, and Zn) in the edible abdominal muscle of cultured freshwater crayfish species (Faxonius virilis; Procambarus acutus acutus) from Missouri. Also, this paper describes the dietary intake and the human health risks from the consumption of crayfish muscle in the adult population. Overall, 172 animals were captured between February 2017 and January 2018 for assessment. Concentrations of metals (Ag, Be, Cd, Cu, Co, Cr, Fe, Mn, Ni, Pb, Sn, Mo, and Zn) and metalloid (As) in the muscle tissue were determined after microwave-assisted acid digestion by ICP - OES. Health indices (EDI/EWI: estimated daily/weekly intakes; THQ: target hazard quotient; TTHQ: total target hazard quotient; ILCR: incremental lifetime cancer risk; and ∑ILCR: cumulative lifetime cancer risk) were calculated and compared to thresholds. Of all samples, the highest concentrations (mg kg -1 wet weight) of metal(loid)s in muscle were Ag (0.11), As (3.15), Be (0.21), Cd (0.11), Co (0.32), Cr (1.22), Cu (107), Fe (23.0), Mn (8.54), Mo (0.62), Ni (2.65), Pb (1.76), Sn (5.91), and Zn (19.2). In both species, the average As, Cd, and Zn concentrations were below the legal limits. However, the levels of Cu, Pb, and As, in some samples, were in exceedance of the maximum levels. In both species, a significant correlation (p < 0.05) was observed between the carapace length (CL) and animal body weight (BW). In P. acutus, CL, BW, and animal total length were homogenous (p > 0.05) among the sexes. Non-parametric Kruskal-Wallis test results indicated significant differences (p < 0.05) in the levels of As, Be, and Zn in F. virilis, and Be and Cr in P. a. acutus among the genders. Significant inter-species differences (p < 0.05) were observed in the levels of Be, Ni, and Pb and the growth factors. The EDI/EWI values were below the permissible limits. THQ and TTHQ values, being below 1.0, indicated no probabilistic health risk. Regarding carcinogenic risk, only As and Ni indicated cancer risk (ILCR >10-5 and ∑ILCR >10-5) to the adult population. High metals/metalloid exposure from crayfish muscle consumption posed potential health hazards to the adult population.

Establishment of a Target, Suspect, and Functional Group-Dependent Screening Strategy for Organophosphate Esters (OPEs): "Into the Unknown" of OPEs in the Sediment of Taihu Lake, China

Current environmental monitoring studies are generally confined to several target organophosphate esters (OPEs), and there is a lack of strategies for comprehensively screening all potential OPEs in environmental samples. Here, an effective and accurate strategy was developed for the target, suspect, and functional group-dependent screening of OPEs by the use of ultrahigh-performance liquid chromatography-Q Exactive hybrid quadrupole-Orbitrap high-resolution mass spectrometry (UHPLC-Q-Orbitrap HRMS), and this strategy was applied for the analysis of n = 74 sediment samples (including 23 surface sediment samples and 51 sediment core samples) collected from Taihu Lake (eastern China) in 2019. In these analyzed samples, we successfully identified n = 35 OPEs, and 23 of them were reported in this region for the first time. In addition, this strategy also presented other interesting findings, i.e., (1) OPE concentrations decreased with increasing distance from the coast of the lake; (2) the newly identified 3-hydroxyphenyl diphenyl phosphate (meta-OH-TPHP) was not statistically significantly correlated with triphenyl phosphate (TPHP; r = 0.02494, p = 0.9101) but with resorcinol bis(diphenyl phosphate) (RDP) (r = 0.9271, p < 0.0001) and three other OPEs; and (3) the summed concentrations of aryl OPEs (∑_arylOPEs) in sediment core samples exhibited significantly increasing trends as the depth decreased. Collectively, this study provided an effective strategy that was successfully applied for comprehensive screening of OPEs in the sediments of Taihu Lake, and this strategy could have promising potential to be extended to other environmental matrices or samples.