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

Mitigating the environmental effects of healthcare: the role of the endocrinologist

Human health depends on planetary health, and yet healthcare provision can have unintended consequences for the health of the planet. Emissions from the healthcare sector include greenhouse gases, air pollution and plastic pollution, alongside chemical contamination. Chemical pollution resulting in endocrine disruption has been associated with plastics, which are a source of concerning additives such as phthalates, bisphenols, perfluoroalkyl and polyfluoroalkyl substances, and flame retardants (all routinely found in healthcare products). Many endocrine-disrupting chemicals are persistent and ubiquitous in the environment (including water and food sources), with potential secondary harms for human health, including disrupting reproductive, metabolic and thyroid function. Here we review evidence-based strategies for mitigating environmental effects of healthcare delivery. We focus on what endocrinologists can do, including reducing demand for healthcare services through better preventative health, focusing on high-value care and improving sustainability of medical equipment and pharmaceuticals through adopting circular economy principles (including reduce, reuse and, as a last resort, recycle). The specific issue of endocrine-disrupting chemicals might be mitigated through responsible disposal and processing, alongside advocating for the use of alternative materials and replacing additive chemicals with those that have lower toxicity profiles, as well as tighter regulations. We must work to urgently transition to sustainable models of care provision, minimizing negative effects on human and planetary health.

Degradation mechanisms of isodecyl diphenyl phosphate (IDDP) and bis-(2-ethylhexyl)-phenyl phosphate (BEHPP) using a novel microbially-enriched culture

Organophosphate esters (OPEs) pose significant environmental concerns due to their widespread presence, potential toxicity, and persistence. This study investigated the degradation of the isodecyl diphenyl phosphate (IDDP) and bis-(2-ethylhexyl)-phenyl phosphate (BEHPP) using a novel enrichment culture, which could degrade 85.4 % and 78.2 % of 1 mg/L IDDP and BEHPP after 192 h and 172 h, respectively, under extremely low bacterial dosage (the initial OD600 nm= 0.0075, biomass was approximately 1 mg/L). The identification of intermediate products suggested that the degradation reactions likely included hydrolysis, hydroxylation, methylation, carboxylation, and glycosylation. Metagenomic analysis highlighted the crucial role of enzymes in degrading IDDP and BEHPP, including phosphatase, phosphodiesterase, cytochrome P450, and hydroxylase. Pure strains Burkholderia cepacia ZY1, Sphingopyxis terrae ZY2, and Amycolatopsis ZY3 were isolated, and their efficient individual degradation abilities were confirmed. These efficiencies were lower compared to the enrichment culture, emphasizing the importance of microbial interactions for effective degradation. The pathways identified for these strains illustrated their involvement in different degradation steps, reinforcing the synergy between different degraders. Molecular dynamics simulations provided insights into the interactions between alkaline phosphatase (ALP), cytochrome P450 (CYP450), and hydroxylase with OPEs. These enzymes demonstrated a strong binding capacity with both BEHPP and IDDP, exhibiting distinct binding site preferences that may contribute to varied metabolic pathways. These findings comprehensively reveal the transformation mechanisms of OPEs.

Organophosphate esters inhibit enzymatic proteolysis through non-covalent interactions

Enzymatic proteolysis is the key process to produce bioavailable nitrogen in natural terrestrial and aquatic ecosystems for microorganisms and plants. However, little is known on how protein degradation is influenced by organic contaminants. As we known, the overuse of organophosphate esters (OPEs) has caused serious pollution in soil, water, and sediment. Thereby we studied the effect of OPEs on the proteolysis of protein GB1 in aqueous system at neutral pH, and explored the underlying molecular mechanism. Colorimetric ninhydrin methods and SDS-PAGE results revealed that OPEs inhibited the enzymatic hydrolysis of protein GB1. Based on fluorescence quenching experiments, the binding constant (LogKA) were found in order: 6.16 (dibutyl phosphate) > 5.11 (diethyl phosphate) > 1.78 (tributyl phosphate) > 0.876 (triethyl phosphate), proving the interactions between OPEs and protein GB1. Further spectroscopic experiments and molecular docking simulations showed that OPEs could entered the pocket structure of GB1 and induced secondary structural changes and protein folding through non-covalent interactions dominated by hydrogen bonding and van der Waals forces. In addition, organophosphate diesters (di-OPEs) and long-chain OPEs had stronger affinity to GB1, due to the more negative and denser electrostatic surface potential distributions. The deformation of proteins hindered the contact between their active sites and enzymes, leading to the inhibition of GB1 hydrolysis. This study deepened our understanding of the effect of OPEs on protein transformation and degradation, which could further influence the ecological functions and nutrient cycling.

Environmental occurrence, fate, human exposure, and human health risks of p-phenylenediamines and their quinones

P-phenylenediamine antioxidants (PPDs) are widely used in the rubber industry and their release and transformation in the environment has become one of the current environmental research hotspots. PPDs are readily oxidized in the environment to form quinone transformation products (PPD-Qs), some of which (e.g. 6PPD-Q) have been shown to be highly toxic and persistent in the environment, posing a potential threat to aquatic organisms and ecosystems. The present study provides an overview of the physicochemical properties, environmental distribution, and potential human exposure and toxicological effects of PPDs and PPD-Qs. PPDs and PPD-Qs are found in water, air, dust and soil around the world, and humans are inevitably exposed to them by inhaling, ingesting and through dermal contact. There is growing evidence indicates that PPDs and PPD-Qs are present in human body fluids and tissues, where they are subject to metabolic and transformational processes in the liver and blood. Furthermore, PPDs and PPD-Qs have the potential to induce adverse health effects, including digestive, respiratory, neurotoxic and reproductive toxicity. Nevertheless, there is a paucity of evidence concerning the direct effects of PPDs and PPD-Qs on human health. Consequently, future research should concentrate on this area in order to provide quantitative support for the assessment of the risk posed by PPDs and PPD-Qs to human health.

Fast determination of organophosphate esters and their metabolites in human matrices by a straightforward cold-induced strategy coupled with HPLC-MS/MS

Organophosphate esters (OPEs) are commonly used chemicals and are also regarded as emerging environmental pollutants. Recently, it has been proved that metabolites of OPEs (mOPEs) could also cause health concerns. However, analytical methods for the concurrent measurement of OPEs and mOPEs in human matrices are still complicated. In this study, a convenient and efficient analytical method combining a cold-induced strategy and HPLC-MS/MS was developed to simultaneously determine 18 OPEs and 10 mOPEs in human serum, urine, and human milk. In brief, after the sample was extracted with acetonitrile, a "one-step" treatment combining purification and enrichment was accomplished by cold-induced liquid-liquid extraction (CI-LLE), and analytes were then quantified by HPLC-ESI-MS/MS. The ratio of acetonitrile/water, and the temperature and time set in the CI-LLE procedure were optimized for achieving the highest enrichment factors. Under the best conditions, linearity, limits of detection (LODs), recovery, precision, and matrix effects of OPEs/mOPEs were verified. LODs of OPEs/mOPEs in serum, urine, and human milk were 0.1-113 pg/mL, 0.1-22 pg/mL, and 0.2-22 pg/mL, respectively. Average recoveries ranged from 80 to 123%, with relative standard deviations lower than 15% for most analytes. The matrix effect test showed slight signal enhancement or inhibition, and the use of isotopically labeled internal standards (ISs) could compensate for the effects. In real sample analysis, both OPEs and mOPEs showed high detecting frequency, which indicated their ubiquity in humans.

Nationwide profiling and source identification of organophosphate esters in Korean surface waters using target, suspect, and non-target HRMS analysis

Organophosphate esters (OPEs) are emerging contaminants that serve as alternatives to regulated substances in aquatic environments. A nationwide large-scale assessment for OPEs, including point sources, remains insufficient. To address this issue, we aimed to investigate OPEs occurrence and novel OPEs via comprehensive target, suspect and non-target analysis. Among the 11 target OPEs, 10 were detected at sampling sites distributed evenly nationwide. The highest mean concentrations were measured for tris-(2-butoxyethyl) phosphate (TBOEP) and tris(2-chloroisopropyl) phosphate (TCIPP). The multivariate statistical analysis revealed that TBOEP and TCIPP are essential components for assessing total OPEs pollution. The systematic risk assessment results evaluated the overall risk contribution of TBOEP and the significant risk impact of 2-ethylhexyl diphenyl phosphate. Promising suspect and non-target analysis enabled frequent detection and identification of 6 antioxidant transformation products (TPs), as well as the tentative identification of 14 OPEs and TPs, including 3 di-OPEs. Based on sampling site classification, we confirmed that major OPEs are significantly discharged near point sources. We believe that this is the first attempt to assess the nationwide risk and potential sources of OPEs in Korean surface waters, providing insights that could support further prioritization and regulation efforts.

Exploring organophosphate ester contamination and distribution in food: A meta-analysis

This study examines the food safety risk of organophosphate esters (OPEs) by analyzing data from 23 studies with 14,915 data points. We found EDP contamination highest in cereals, dairy, and meats, and TEHP most prevalent in vegetables and fruits, with contamination levels reaching 4.54 ng/g and 1.46 ng/g, respectively. Food processing influences OPE contamination through complex and multifaceted, akin to a "double-edged sword.", as meta-analysis and Principal Component Analysis (PCA) revealed. Estimated Dietary Intakes (EDI) identified vegetables and cereals as primary OPE sources, contributing 33.3% and 23.8% of total intake, with EDI values of 44.74 ng/kg bw/day and 32.25 ng/kg bw/day, respectively. Current exposure levels are within U.S. EPA safety thresholds (HQ < < 1), but the heightened risk to infants and children necessitates revising safety standards and ongoing monitoring.

Fugacity- and biotransformation-based mechanistic insights into the trophic transfer of organophosphate flame retardants in a subtropical coastal food web from the Northern Beibu Gulf of China

The bioaccumulation and trophic transfer of organophosphate flame retardants (OPFRs) in marine ecosystems have attracted great attention in recent research, but our understanding of the trophic transfer mechanisms involved is limited. In this study, we investigated the trophodynamics of OPFRs and their metabolites in a subtropical coastal food web collected from the northern Beibu Gulf, China, and characterized their trophodynamics using fugacity- and biotransformation-based approaches. Eleven OPFRs and all seven metabolites were simultaneously quantified in the shellfish, crustacean, pelagic fish, and benthic fish samples, with total concentrations ranging from 164 to 4.11 × 104 and 4.56-4.28 × 103 ng/g lipid weight, respectively. Significant biomagnification was observed only for tris (phenyl) phosphate (TPHP) and tris (2-ethylhexyl) phosphate (TEHP), while other compounds except for tris(2-chloroethyl) phosphate (TCEP) displayed biomagnification trends based on Monte Carlo simulations. Using a fugacity-based approach to normalize the accumulation of OPFRs in biota to their relative biological phase composition, storage lipid is the predominant biological phase for the mass distribution of 2-ethylhexyl diphenyl phosphate (EHDPHP) and TPHP. The water content and structure protein are equally important for TCEP, whereas lipid and structure protein are the two most important phases for other OPFRs. The mass distribution of these OPFRs along with TLs can explain their trophodynamics in the food web. The organophosphate diesters (as OPFR metabolites) also displayed biomagnification trends based on bootstrapped estimation. The correlation analysis and Korganism-water results jointly suggested the metabolites accumulation in high-TL organisms was related to biotransformation processes. The metabolite-backtracked trophic magnification factors for tri-n‑butyl phosphate (TNBP) and TPHP were both greater than the values that accounted for only the parent compounds. This study highlights the incorporation of fugacity and biotransformation analysis to characterize the trophodynamic processes of OPFRs and other emerging pollutants in food webs.

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.

Universal occurrence of organophosphate tri-esters and di-esters in marine sediments: Evidence from the Okinawa Trough in the East China Sea

Despite numerous data on organophosphate tri-esters (tri-OPEs) in the environment, literatures on organophosphate di-esters (di-OPEs) in field environment, especially marine sediments remain scarce. This study addresses this gap by analyzing 35 abyssal sediment samples from the middle Okinawa Trough in the East China Sea. A total of 25 tri-OPEs and 10 di-OPEs were determined, but 13 tri-OPEs and 2 di-OPEs were nondetectable in any of these sediment samples. The concentrations of ∑12tri-OPE and ∑8di-OPE were 0.108-32.2 ng/g (median 1.11 ng/g) and 0.548-15.0 ng/g (median 2.74 ng/g). Chlorinated (Cl) tri-OPEs were the dominant tri-esters, accounting for 47.5 % of total tri-OPEs on average, whereas chlorinated di-OPEs represented only 19.2 % of total di-OPEs. This discrepancy between the relatively higher percentage of Cl-tri-OPEs and lower abundance of Cl-di-OPEs may be ascribed to the stronger environmental persistence of chlorinated tri-OPEs. Source assessment suggested that di-OPEs were primarily originated from the degradation of tri-OPEs rather than industrial production. Long range waterborne transport facilitated by oceanic currents was an important input pathway for OPEs in sediments from the Okinawa Trough. These findings enhance the understanding of the sources and transport of OPEs in marine sediments, particularly in the Okinawa Trough.

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

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