Be Aware of Organophosphate Diesters as Direct Sources in Addition to Organophosphate Ester Metabolites in Food Supplies

Single injection by LC-ESI-MS/MS for simultaneous determination of organophosphate tri- and di-esters in plant tissue based on ultrasonic-assisted sequential extraction and single-step purification

A novel methodology based on ultrasonic-assisted sequential extraction, dispersive-SPE purification, and single-injection on liquid chromatography-tandem mass spectrometry (LC-MS/MS) is proposed, for the first time, to simultaneously measure 14 tri-OPEs and 9 di-OPEs in plant tissues. The samples were successively ultrasonicated with a mixture of hexane:dichloromethane (1:1, v/v) and 8% acetic acid in acetonitrile for extracting tri- and di-OPEs purified with graphitized carbon black and quantitated on LC-MS/MS at the same time. The recoveries of targeted tri- and di-OPEs in the matrix spike ranged from 66% to 120% and 71% to 110% respectively. The proposed method was validated by processing eight types of common vegetables including spinach (Spinacia oleracea L.), lettuce (Lactuca sativa), carrot (Daucus carota var. sativa Hoffm.), sweet potato (Solanum tuberosum L.), cucumber (Cucumis sativus L.), tomato (Solanum lycopersicum L.), green beans (Phaseolus vulgaris), and cowpeas (Vigna unguiculata), with the recoveries of surrogates ranging from 84% to 98%.

Unravelling bioaccumulation, depletion and metabolism of organophosphate triesters in laying hens: Insight of in vivo biotransformation assisted by diester metabolites

Organophosphate triesters (tri-OPEs) threaten human health through dietary exposure, but little is known about their feed-to-food transfer and in vivo behavior in farm animals. Herein 135 laying hens were fed with contaminated feed (control group, low-level group and high-level group) to elucidate the bioaccumulation, distribution, and metabolism of the six most commonly reported tri-OPEs. The storage (breast muscle), metabolism and mobilization (liver and blood) and non-invasive (feather) tissues were collected. The exposure-increase (D1∼14) and depuration-decrease (D15∼42) trends indicated that feed exposure caused tri-OPE accumulation in animal tissues. Tissue-specific and moiety-specific behavior was observed for tri-OPEs. The highest transfer factor (TF) and transfer rate (TR) were observed in liver (TF: 14.8%∼82.3%; TR: 4.40%∼24.5%), followed by feather, breast muscle, and blood. Tris(2-chloroisopropyl) phosphate (TCIPP) had the longest half-life in feather (72.2 days), while triphenyl phosphate (TPhP) showed the shortest half-life in liver (0.41 days). Tri-OPEs' major metabolites (organophosphate diesters, di-OPEs) were simultaneously studied, which exhibited dose-dependent and time-dependent variations following administration. In breast muscle, the inclusion of di-OPEs resulted in TF increases of 735%, 1108%, 798%, and 286% than considering TCIPP, tributyl phosphate, tris(2-butoxyethyl) phosphate and tris(2-ethylhexyl) phosphate alone. Feather was more of a proxy of birds' long-term exposure to tri-OPEs, while short-term exposure was better reflected by di-OPEs. Both experimental and in silico modeling methods validated aryl-functional group facilitated the initial accumulation and metabolism of TPhP in the avian liver compared to other moiety-substituted tri-OPEs.

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

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

Occurrence of some legacy and emerging contaminants in feed and food and their ranking priorities for human exposure

The "feed-to-food" pathway is one of the most important routes for human exposure to manmade contaminants. The contaminants could threaten human health through the "feed-to-food" route and have recently become of great public concern. This review selects the representative legacy and emerging contaminants (ECs), such as polybrominated diphenyl ethers (PBDEs), novel brominated flame retardants (NBFRs), organophosphate esters (OPEs), short-chain chlorinated paraffins (SCCPs), and per- and polyfluoroalkyl substances (PFASs), regarding their occurrence in feed and food, as well as their metabolites and transport in farming and livestock ecosystems. Factors that might influence their presence and behavior are discussed. This review raises an approach to rank the priority of ECs using the EC concentrations in feed and food and using the hazard quotient (HQ) method for human health. Although SCCPs have the highest levels in feed and food, their potential risks appear to be the lowest. PFASs have the highest HQs on account of human exposure risk. Future research should pay more attention to the combined effects of multiple ECs.

A global survey of organophosphate esters and their metabolites in milk: Occurrence and dietary intake via milk consumption

The first global survey of organophosphate esters (OPEs) and their metabolites (mOPEs) in milk was carried out in this study. Concentrations of 21 OPEs and 9 mOPEs were measured in 178 milk samples collected from 30 countries located on 5 continents, and the ubiquity of both OPEs and mOPEs was observed in milk. Concentrations of ∑₂₁OPEs ranged from 53.3 pg/mL to 4270 pg/mL, with a median level of 367 pg/mL. The median level of ∑₉mOPEs was 153 pg/mL, with a range of 15-7440 pg/mL. No difference was observed among the levels of both ∑₂₁OPEs and ∑₉mOPEs in milk from the five continents. For the relationship between mOPEs and their parent OPEs, some pairs presented significant and positive correlations, which indicated that they shared similar sources. Estimated daily intakes (EDIs) of OPEs/mOPEs via milk consumption were calculated. Asian countries presented relatively low EDIs, and European and American countries, especially Denmark, the Netherlands, Finland and Argentina, presented high EDIs. Current daily OPE intake via milk consumption for global adult populations was far lower than the corresponding reference dose; however, considering that human intake of OPEs occurs via multiple sources, it is too early to conclude that the intake of OPEs were unable to cause health concerns.

Organophosphate esters and their diester metabolites in infant formulas and baby supplementary foods collected in Beijing, China: Occurrence and the implications for infant exposure

Organophosphate esters (OPEs) have been extensively used as flame retardants and/or plasticizers and they found to be ubiquitous in various environmental matrices along with the gradual phase-out of brominated flame retardants (BFRs). Moreover, their main metabolites, organophosphate di-esters (di-OPEs), were also frequently detected. However, few studies focused on the occurrence of OPEs and di-OPEs in foods. In this study, fourteen OPEs and five di-OPEs were measured in infant formula and baby supplementary food (BSF) collected in Beijing, China. Most OPEs and di-OPEs presented high detection frequencies, which indicated their ubiquity in baby foods. The concentrations of ∑₁₄OPEs in the 75 infant formula samples ranged from 0.79 to 159 ng/g, with a median of 23.2 ng/g, and in which triphenyl phosphate (TPhP) was the most abundant compound. The concentrations of ∑₁₄OPEs in the 32 BSF samples were 4.42-115 ng/g (median: 19.5 ng/g), and tri(3-chloropropyl) phosphate (TCIPP) was predominant. Moreover, no significant difference was observed between OPE levels in infant formula and BSF. The median concentrations of Σ₅di-OPEs in infant formula and BSF were 3.39 and 5.43 ng/g, respectively. However, no significantly correlation was observed between concentrations of di-OPEs and their parent compounds, which indicated they have different sources. The median estimated dietary intakes (EDIs) of the ∑₁₄OPEs were from 165 to 383 ng/kg bodyweight (bw)/day for infants via infant formula feeding, and were from 429 to 470 ng/kg bw/day via BSF feeding. A comparison to corresponding reference dose (RfD) suggested that dietary intakes of OPEs to Beijing infants via formula/BSF consumption were still unable to cause significant health concerns. However, EDIs of OPEs for infants were found to be significantly higher than that for Chinese adults, and dietary intake might be the predominant OPE intake pathway for infants. To our knowledge, this is the first study to investigate OPEs and their metabolites in baby foods.

A simple method for simultaneous determination of organophosphate esters and their diester metabolites in dairy products and human milk by using solid-phase extraction coupled to liquid chromatography-tandem mass spectrometry

Organophosphate esters (OPEs) and their diester metabolites have been frequently found in various environmental matrices and regarded as emerging environmental pollutants, whereas data on their occurrence in foods and human matrices are still limited. In this study, a novel and simple procedure was developed to simultaneously determine 14 OPEs and 6 diester metabolites in dairy products and human milk. After enzymatic hydrolysis by β-glucuronidase/arylsulfatase, a freeze-dried milk sample was extracted with acetonitrile and purified by solid-phase extraction. Subsequently, all target compounds were determined by HPLC-ESI-MS/MS. Linearity, limits of detection (LODs), recovery, precision, and matrix effects of the proposed methodology were validated, and the parameters of HPLC-ESI-MS/MS were optimized. LODs for OPEs and their diester metabolites were from 0.001 to 0.02 ng/mL, and limits of quantification (LOQs) were 0.01-0.3 ng/mL. Average recoveries at two spiked levels ranged between 67.3 and 121%, with relative standard deviation lower than 20.7%. A test for matrix effects showed that most analytes presented signal suppression, and isotopically labeled ISs were essential for compensating for the matrix effects. Finally, OPEs and their metabolites both showed high detecting frequencies in real samples, which indicated that these emerging pollutants were ubiquitous in foods and the human body, and the impact of the diester metabolites on population exposure must be included in exposure assessment.

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

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