Determination of 2,6-di-tert-butyl-hydroxytoluene and its transformation products in indoor dust and sediment by gas chromatography-mass spectrometry coupled with precolumn derivatization

Contaminants of emerging concern in water and sediment of the Venice Lagoon, Italy

This study investigates for the first time the contamination of water and sediment of the Venice Lagoon by twenty Contaminants of Emerging Concern (CECs): three hormones, six pharmaceutical compounds (diclofenac and five antibiotics, three of which are macrolides), nine pesticides (methiocarb, oxadiazon, metaflumizone, triallate, and five neonicotinoids), one antioxidant (BHT), and one UV filter (EHMC). Water and sediment samples were collected in seven sites in four seasons, with the aim of investigating the occurrence, distribution, and possible emission sources of the selected CECs in the studied transitional environment. The most frequently detected contaminants in water were neonicotinoid insecticides (with a frequency of quantification of single contaminants ranging from 73% to 92%), and EHMC (detected in the 77% of samples), followed by BHT (42%), diclofenac (39%), and clarithromycin (35%). In sediment the highest quantification frequencies were those of BHT (54%), estrogens (ranging from 35% to 65%), and azithromycin (46%). Although this baseline study does not highlight seasonal or spatial trends, results suggested that two of the major emission sources of CECs in the Venice Lagoon could be tributary rivers from its drainage basin and treated wastewater, due to the limited removal rates of some CECs in WWTPs. These preliminary results call for further investigations to better map priority emission sources and improve the understanding of CECs environmental behavior, with the final aim of drawing up a site-specific Watch List of CECs for the Venice Lagoon and support the design of more comprehensive monitoring plans in the future.

Establishment of compound database of emerging antioxidants and high-resolution mass spectrometry screening in lake sediment from Taihu Lake Basin, China

Antioxidants are ubiquitous in various environmental samples, leading to increasing concern regarding their potential risk to environments or humans. However, there is dearth of information regarding the environmental fate of antioxidants and unknown/unexpected antioxidants in the environment. Here, we established a compound database (CDB) containing 320 current-used antioxidants by collecting the chemicals from EPA's functional use database and published documents. Physical-chemical characteristics of these antioxidants were estimated, and 19 ones were considered as persistent and bioaccumulative (P&B) substances. This CDB was further coupled with high resolution mass spectrometry (HRMS) technique, which was employed for suspect screening of antioxidants in extracts of sediments (n = 88) collected from Taihu Lake basin. We screened 119 HRMS features that can match 135 chemical formulas in the CDB, and 20 out of them exhibited the detection frequencies ≥ 90%. The total concentrations of suspect antioxidants in sediments ranged from 6.41 to 830 ng/g dw. Statistical analysis demonstrated that concentrations of suspect antioxidants in Taihu Lake were statistically significantly lower than those in Shihu and Jiulihu Lake, but greater than those from other small lakes. Collectively, this study provided a CDB that could be helpful for further monitoring studies of antioxidant in the environments, and also provided the first evidence regarding the ubiquity of antioxidants in aquatic environment of Taihu Lake basin.

Degradation of Butylated Hydroxyanisole by the Combined Use of Peroxymonosulfate and Ferrate(VI): Reaction Kinetics, Mechanism and Toxicity Evaluation

Butylated hydroxyanisole (BHA), a synthetic phenolic antioxidant (SPA), is now widely present in natural waters. To improve the degradation efficiency of BHA and reduce product toxicity, a combination of peroxymonosulfate (PMS) and Ferrate(VI) (Fe(VI)) was used in this study. We systematically investigated the reaction kinetics, mechanism and product toxicity in the degradation of BHA through the combined use of PMS and Fe(VI). The results showed that PMS and Fe(VI) have synergistic effects on the degradation of BHA. The effects of operational factors, including PMS dosage, pH and coexisting ions (Cl-, SO42-, HCO3-, K+, NH4+ and Mg2+), and different water matrices were investigated through a series of kinetic experiments. When T = 25 °C, the initial pH was 8.0, the initial BHA concentration was 100 μM, the initial concentration ratio of [PMS]0:[Fe(VI)]0:[BHA]0 was 100:1:1 and the degradation rate could reach 92.4% within 30 min. Through liquid chromatography time-of-flight mass spectrometry (LC-TOF-MS) identification, it was determined that the oxidation pathway of BHA caused by PMS/Fe(VI) mainly includes hydroxylation, ring-opening and coupling reactions. Density functional theory (DFT) calculations indicated that •OH was most likely to attack BHA and generate hydroxylated products. The comprehensive comparison of product toxicity results showed that the PMS/Fe(VI) system can effectively reduce the environmental risk of a reaction. This study contributes to the development of PMS/Fe(VI) for water treatment applications.

The key constituents underlying the combined toxicity of eight cosmetic contaminants towards Vibrio qinghaiensis

Cosmetic additives (ADDs) and packaging plasticizers (PLAs) probably present potential risks and dangers to the environment and human body as emerging pollutants. To investigate their potential risks and dangers, five ADDs including methyl paraben (MET), ethyl paraben (ETH), propyl paraben (PRO), butyl-hydroxy anisole (BHA), and salicylic acid (SAL), as well as three PLAs including bisphenol A (BPA), bisphenol S (BPS) and tris(2-butoxyethyl) phosphate (TBEP) were selected as research objects, and ten mixture rays (R1-R10) composed of the eight components were designed by the uniform design ray (UD-Ray) method. The toxicities of the eight cosmetic pollutants and their eight-component mixture system towards Vibrio qinghaiensis sp.-Q67 (Q67) were systematically determined by the time-dependent microplate toxicity analysis (t-MTA) method. The three-dimensional (3D) surface of deviation from the concentration addition model (dCA) was utilized to qualitatively and quantitatively analyse the toxicity interaction of the mixtures and the correlation between toxicity interaction and the components' concentration ratios. Finally, eight individual pollutants and representative rays with significant inhibitory and interactive effects were selected to analyse DNA and soluble proteolysis as well as the microstructure and morphology of Q67 after treatment with single chemicals and their mixtures. The results showed that the eight cosmetic pollutants had conspicuous concentration-dependent toxicity and acute toxicity, and none of them, except BPS, BPA and ETH, had time-dependent toxicity. All rays had time/concentration-dependent toxicity and acute toxicity. At the same time, the toxicity interaction of these mixture rays was predominantly antagonism and the strongest antagonism appeared at high concentrations at 12 h. Nevertheless, the components' concentration ratio (pi) was the decisive factor for the type of mixture interaction. The correlation analysis revealed a significant positive linear correlation between mixture toxicity and pETH and pBPA, which indicated that ETH and BPA were the key components of the toxic effects. However, there was a significant negative linear correlation between the antagonism intensity and pBPA and pTBEP, which demonstrated that BPA and TBEP were the key components of the antagonism intensity. Pollutants and their mixtures can also damage cellular structures, and mixtures can exacerbate the dissolution of DNA and soluble proteins.

Potential thyroid hormone disorder risks of tire antioxidants to aquatic food chain organisms after absorbing free radicals in marine and freshwater environments

Tire antioxidants are essential functional chemical additives in tire rubber production. Because of the characteristic easy precipitation in the water environment, the environmental pollution problem caused by tire antioxidants is concerning. To reveal the mechanism by which tire antioxidants reduce common oxidative factors (free radicals) in the environment and to control the potential biological thyroid hormone disorder risk of tire antioxidant derivatives, eight commonly used antioxidants in tire production were selected for analysis. Firstly, the ability of tire antioxidants to reduce three different free radicals was quantitatively characterized based on Gaussian calculation method and inferring the radical reduction mechanism of tire antioxidants. Moreover, using the PaDEL-Descriptor software and random forest algorithm found that the N-octanol/water partition coefficient, a structure descriptor of tire antioxidant molecules, significantly correlated with their reducing ability. Second, molecular docking and molecular dynamics methods were used to assess the thyroid hormone disorder risk to aquatic organisms of eight antioxidants after reducing three free radicals. And this is the first study to construct an assessment score list of potential thyroid hormone disorder risk of the derivatives of tire antioxidants after reducing free radicals to marine and freshwater aquatic organisms based on the risk entropy method. Through the screening of this list, it was found that the derivative of the antioxidant 2,2,4-trimethyl-1,2-dihydroquinoline oxidized by free radicals had the highest risk of thyroid hormone disorder. In addition, the top organism in the aquatic food chain was the most affected. This study also revealed that van der Waals interactions and hydrogen bonding were the main influencing factors of thyroid hormone disorder risk to aquatic organisms of the derivatives of tire antioxidants that reduce free radicals based on amino acid residue analysis. Overall, the results provide theoretical support for the selection of antioxidants and the avoidance and control of environmental risks in the tire rubber production process.

A fully green sample preparation method for synthetic antioxidants determination in edible oils based on natural feather fiber-supported liquid extraction

The current study proposed a novel feather fiber-supported liquid extraction (FF-SLE) method for extracting analytes from oil samples. The natural feather fibers were used as the oil support material and directly loaded in the plastic tube of a disposable syringe to construct the low-cost extraction device (∼0.5 CNY). The edible oil without any pretreatment including dilution was added directly to the extraction device, followed by the addition of the green extraction solvent of ethanol. As an example, the proposed method was applied to extract nine synthetic antioxidants from edible oils. The optimized extraction conditions for processing 0.5 g of oil were obtained when the syringe dimension was 5 mL, the extraction solvent was 0.5 mL of ethanol, the amount of feather fibers was 200 mg of duck feather fibers and the static extraction time was 10 min. The applications to seven kinds of feathers and seven kinds of edible oils all indicated the excellent oil removal efficiencies (>98.0%). Combined with high-performance liquid chromatography-ultraviolet, a quantification method was validated with satisfied linearity (R²≥0.994), accuracy (95.8-114.6%) and precision (≤8.3%) with the limits of detection ranging from 50 to 100 ng/g. The proposed FF-SLE method was simple, effective, convenient, low-cost, green and environmental-friendly for the extraction of analytes from oil samples prior to instrument analysis.

The transformation mechanism and eco-toxicity evaluation of butylated hydroxyanisole in environment

Butylated hydroxyanisole (BHA) is one of important phenolic antioxidants and its fate in the environment has attracted much attention in recent years. In this study, the initial reactions of BHA with OH radicals, including 8 abstraction reactions and 6 addition reactions, were calculated. The lowest energy barrier of 3.20 kcal mol^-1 was found from the abstraction reaction on phenolic hydroxyl group. The reaction barriers of addition paths are in the range of 5.48-9.28 kcal mol^-1, which are lower than those of the abstraction paths. The reaction rate constants were calculated by using transition state theory, and the rate constants are 8.12 × 10⁷ M^-1 s^-1and 4.76 × 10⁷ M^-1 s^-1 for the H-abstraction and OH-addition reactions, respectively. Through the calculation of the subsequent reactions of the abs-H₀-TS₁ and add-C₄-M₁ it was found that BHA would be further transformed into 2-tert-Butyl-1,4-benzoquinone (TBQ), tert-butylhydroquinone (TBHQ) etc. in the aqueous phase, and the eco-toxicities of these transformed products of BHA in the aqueous phase were significantly increased comparing with that of the BHA and they are toxic to aquatic organism.

Trace analysis of multiple synthetic phenolic antioxidants in foods by liquid chromatography-tandem mass spectrometry with complementary use of electrospray ionization and atmospheric pressure chemical ionization

This study presented a universal LC-MS/MS method for trace analysis of multiple synthetic phenolic antioxidants (SPAs) in foods by complementary use of electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI). The analytes included not only the well-known BHT and BHA but also 18 high molecular weight SPAs. The method utilized APCI to achieve sensitive analysis of BHT, Irganox 1010, Irganox 330, and Irganox 3125 based on the finding that APCI significantly improved the sensitivity of these weakly acidic or slightly polar SPAs, and utilized ESI to obtain sensitive analysis of other SPAs. Additionally, the method avoided background contamination by using effective measures including installation of a trapping column in the LC system. Method performance assessment showed satisfactory sensitivity, linearity, accuracy, and precision for analysis of SPAs in vegetable oil, milk powder, and baby fruit puree. Method application revealed widespread contamination of foods with BHT, Irganox 1010, and Irganox 1076.

Rat Metabolism Study Suggests 3-(3,5-Di-tert-butyl-4-hydroxyphenyl)propionic Acid as a Potential Urinary Biomarker of Human Exposure to Representative 3-(3,5-Di-tert-butyl-4-hydroxyphenyl)propionate Antioxidants

3-(3,5-Di-tert-butyl-4-hydroxyphenyl)propionate antioxidants, a family of synthetic phenolic antioxidants (SPAs) widely used in polymers, have recently been identified in indoor and outdoor environments. However, limited information is available concerning human exposure to these novel contaminants. In the present study, seven 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate antioxidants were analyzed in human urine samples of donors from the United States. None of the target SPAs were initially detected in the urine samples either before or after hydrolysis by β-glucuronidase, prompting us to probe the major metabolites of these SPAs. We conducted rat metabolism studies with two representative congeners, tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) (AO1010) and N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine (AO1024). Neither AO1010 nor AO1024 was detected in rat urine, while 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid (fenozan acid) was identified as a urinary biomarker for these 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate antioxidants. Surprisingly, fenozan acid was detected in 88% of the human urine samples before hydrolysis (geometric mean: 0.69 ng/mL) and 98% of the samples after hydrolysis (geometric mean: 10.2 ng/mL), indicating prevalent human exposure to 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate antioxidants. To our knowledge, this is the first study reporting the occurrence of fenozan acid in urine, where it can act as a potential biomarker of human exposure to 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate antioxidants.

Analysis, occurrence, toxicity and environmental health risks of synthetic phenolic antioxidants: A review

The continuous improvement of living standards is related to higher requirements for the freshness and taste of food. For example, synthetic phenolic antioxidants (SPAs) are added to fats and fried foods as food additives to minimize the oxidative rancidity of oils and fats. Hence, the global use of SPAs is increasing year by year. Dibutyl hydroxytoluene is one of the widely used SPAs, often in combination with butyl hydroxyanisole or gallate SPAs. The extensive use of these compounds makes them and their transformation products to be widespread in various environmental matrices, including indoor dust, wastewater, river water, sewage sludge, and sediment, as well as human samples, such as nails and urine, at concentrations varying from nanogram per gram (ng/g) to microgram per gram (μg/g). Animal experiments have shown that high-dose SPA exposure is toxic, which may lead to DNA damage and mismatches and the development of cancerous tumors. Since the biosphere shares the same set of genetic codes, humans and animals have many identical or similar feedback mechanisms and information pathways. Therefore, the damage of SPAs to animals may also threaten human health. This review discusses the properties, occurrence, analysis, and environmental health risks of typical SPAs, including butyl hydroxyanisole, dibutyl hydroxytoluene, tert-butylhydroquinone, propyl gallate, octyl gallate, and lauryl gallate, used as food additives. In addition, AO2246, which is used in food packaging bags, is also considered. Future research directions on SPAs and their transformation products (TPs) are identified and discussed.

"Novel" Synthetic Antioxidants in House Dust from Multiple Locations in the Asia-Pacific Region and the United States

Synthetic antioxidants represent a complex group of additive chemicals broadly used in consumer products. While traditional antioxidants such as 2,6-di-tert-butyl-4-methylphenol (BHT) have been well studied, a variety of "novel" antioxidants have emerged with extensive applications but received much less attention. Our study aimed to explore a suite of 34 emerging antioxidants in house dust from four different regions, including Guangzhou (China), Adelaide (Australia), Carbondale (Illinois), and Hanoi (Vietnam). The results revealed broad occurrence of several rarely investigated chemicals in house dust across regions, including triethylene glycol bis(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate (AO245), 2,6-di-tert-butyl-4-(dimethylamino)methylphenol (AO4703), 2,2'-thiene-2,5-diylbis(5-tert-butyl-1,3-benzoxazole) (BBOT), 1,3-diphenylguanidine (DPG), 2,4-bis(1,1-dimethylethyl)phenol (2,4DtBP), and 2,6-bis(1,1-dimethylethyl)phenol (2,6DtBP). In particular, DPG exhibited a median concentration of 5030-11 400 ng/g in house dust from the studied regions except for Hanoi (305 ng/g), generally 1 order of magnitude greater than that of BHT (890-1060 ng/g) and dominating the compositional profiles of antioxidants. Estimated intake of target antioxidants by toddlers via dust ingestion, even under the high exposure scenario, was determined to be 2-4 orders of magnitude lower than the reference doses of selected antioxidants. However, potential risks from long-term exposure to a cocktail of antioxidants under environmentally relevant concentrations merit further investigations due to insufficient knowledge on the sources, fate, and toxicokinetics of these chemicals to date.

Printing ink related chemicals, including synthetic phenolic antioxidants, organophosphite antioxidants, and photoinitiators, in printing paper products and implications for human exposure

Although synthetic antioxidants (AOs) and photoinitiators (PIs) are known to be used in printing inks, there are little data on residual concentrations in printing paper products. In the present study, twenty-five PIs, ten AOs, and six transformation products were analyzed in two types of printing paper products, magazines and paperboard food packaging materials, both of which are unavoidable everyday products in our life. Nine AOs and six transformation products can be detected in food packaging materials with total concentrations (geometric mean, GM) of 1.16 × 10⁴ ng/dm². Twenty-two PIs were detected in food packaging materials with total concentrations (GM) of 1.76 × 10⁴ ng/dm². These chemicals were also detected in magazines, albeit at low concentrations (GM of AOs: 466 ng/dm², GM of PIs: 1.17 × 10³ ng/dm²). Magazine front covers were found to have much higher concentrations of the target compounds than magazine inside pages. Tris(2,4-di-tert-butylphenyl) phosphate (AO168O), 2,6-di-tert-butyl-4-methylphenol (BHT), bisphenol A (BPA), and benzophenone (BP) were among the predominant chemicals in those printing paper products. Preliminary calculations suggest that dermal exposure to AOs (GM: 6.25 ng/day) and PIs (GM: 17.0 ng/day) via contact with printing paper products is a minor exposure pathway compared to food intake/dust ingestion and is exceedingly unlikely to cause adverse health effects.

Identification of In Vitro Metabolites of Synthetic Phenolic Antioxidants BHT, BHA, and TBHQ by LC-HRMS/MS

Butylated hydroxytoluene (BHT) and its analogs, butylated hydroxyanisole (BHA) and tert-butyl-hydroquinone (TBHQ), are widely used synthetic preservatives to inhibit lipid oxidation in the food, cosmetic and pharmaceutical industries. Despite their widespread use, little is known about their human exposure and related biotransformation products. The metabolism of these compounds was investigated using in vitro incubations with human and rat liver fractions. Liquid chromatography coupled to high-resolution tandem mass spectrometry was employed to detect and characterize stable and reactive species formed via oxidative metabolism, as well as phase II conjugates. Several oxidative metabolites have been detected, as well as glutathione, glucuronide, and sulfate conjugates, many of which were not previously reported. A combination of accurate mass measurements, MS/MS fragmentation behavior, and isotope-labeling studies were used to elucidate metabolite structures.

Tissue distribution, excretion, and metabolism of 2,6-di-tert-butyl-hydroxytoluene in mice

As one typical synthetic phenolic antioxidant, 2,6-di-tert-butyl-hydroxytoluene (BHT) has been widely adopted in food and other human products, and considered as an emerging contaminant due to its toxic effects. Understanding bioaccumulation and metabolism of BHT is crucial to evaluate its environmental fate and toxicity. In this study, the tissue distribution, excretion, and metabolism of BHT in mice were investigated. It was shown that BHT was prone to be accumulated in metabolism-related organs (i.e., liver and kidney) with AUC_{0-120 h} (area under the concentration-time curve from 0 to 120 h) values of 206 h·μg/g in liver and 162 h·μg/g in kidney. For metabolites, 2,6-di-tert-butyl-4-hydroxy-4-methyl-2,5-cyclohexadione (BHT-quinol) was preferentially accumulated in liver, while 3,5-di-tert-butyl-4-hydroxybenzoic acid (BHT-COOH) was the major metabolite in excreta. The major excretion of BHT and metabolites was through feces with a value of 25.1 ± 0.16% of the initial dose compared with urine of 1.27 ± 0.05%. The possible metabolic pathways of BHT were elucidated as the oxidation of the para-methyl, tert-butyl groups, and aromatic ring based on the known and identified unknown metabolites by HPLC-Q-TOF-MS/MS. The preferred accumulation of BHT and metabolites in liver implies their potential hepatotoxicity. Results here also suggested that considering the distribution and excretion of metabolites can better assess BHT's fate and risk in mammals.

Synthetic Phenolic Antioxidants: A Review of Environmental Occurrence, Fate, Human Exposure, and Toxicity

Synthetic phenolic antioxidants (SPAs) are widely used in various industrial and commercial products to retard oxidative reactions and lengthen product shelf life. In recent years, numerous studies have been conducted on the environmental occurrence, human exposure, and toxicity of SPAs. Here, we summarize the current understanding of these issues and provide recommendations for future research directions. SPAs have been detected in various environmental matrices including indoor dust, outdoor air particulates, sea sediment, and river water. Recent studies have also observed the occurrence of SPAs, such as 2,6-di-tert-butyl-4-methylphenol (BHT) and 2,4-di-tert-butyl-phenol (DBP), in humans (fat tissues, serum, urine, breast milk, and fingernails). In addition to these parent compounds, some transformation products have also been detected both in the environment and in humans. Human exposure pathways include food intake, dust ingestion, and use of personal care products. For breastfeeding infants, breast milk may be an important exposure pathway. Toxicity studies suggest some SPAs may cause hepatic toxicity, have endocrine disrupting effects, or even be carcinogenic. The toxicity effects of some transformation products are likely worse than those of the parent compound. For example, 2,6-di-tert-butyl-p-benzoquinone (BHT-Q) can cause DNA damage at low concentrations. Future studies should investigate the contamination and environmental behaviors of novel high molecular weight SPAs, toxicity effects of coexposure to several SPAs, and toxicity effects on infants. Future studies should also develop novel SPAs with low toxicity and low migration ability, decreasing the potential for environmental pollution.

Broad Exposure of the North American Environment to Phenolic and Amino Antioxidants and to Ultraviolet Filters

The present study provides a comprehensive investigation of three suites of commonly used synthetic additives: phenolic and amino antioxidants and ultraviolet filters. The concentrations of 47 such compounds and their transformation products were measured in 20 atmospheric particle samples collected in Chicago, in 21 Canadian e-waste dust samples, in 32 Canadian and United States' residential dust samples, and in 10 sediment samples collected from the Chicago Sanitary and Ship Canal. Despite their large production volumes in the United States, environmental data on antioxidants and UV filters in North America is limited. These compounds were detected in all the samples, indicating their ubiquitous distribution in the North American environment. The most prevalent compounds were 2,6-di-t-butyl-p-benzoquinone, diphenylamine, 4,4'-di-t-octyl diphenylamine, 2,4-dihydroxybenzophenone, and 2-hydroxy-4-methoxybenzophenone. The e-waste dust contained significantly greater total concentrations of these compounds than the Canadian residential dust, while intermediate levels were detected in the United States residential dust. The sediment samples showed relatively high levels of N,N'-diphenylbenzidine, the source of which is unclear, and some benzotriazole UV filters. Daily intake rates by dust ingestion for these compounds ranged from 1-10 ng/(kg·day) for adults to 10-100 ng/(kg·day) for toddlers. Due to the wide distribution of these compounds in both the ambient and built environments, future research on their potential toxic effects on people and ecosystems is important.

Determination of the Contents of Antioxidants and Their Degradation Products in Sodium Chloride Injection for Blood Transfusion

The infusion bag is mainly made up of polyolefin polymer. Antioxidants are usually added to these polymer materials in the production process to prevent the materials from aging and enhance the stability of the materials. Because of the potential harm of antioxidants to human body, it is necessary to limit the amount of antioxidants migrating to the pharmaceutical solutions. In the present study, we developed and validated the HPLC method for the simultaneous quantification of antioxidants and their degradation products migrating to sodium chloride solution for injection. A total of six antioxidants and six their degradation products were separated and simultaneously determined by using a Waters Symmetry RP18 column (250 × 4.6 mm, 5 μm) and gradient elution of methanol/acetonitrile/acetic acid-water (1 : 99, v/v) at a flow rate of 1.0 mL/min. The detective wavelength was set at 277 nm, and the column temperature was maintained at 35°C. The method was validated in terms of limit of detection (LOD, 0.011-0.151 μg/mL), limit of quantification (LOQ, 0.031-0.393 μg/mL), intraday precision (0.25%-3.17%), interday precision (0.47%-3.48%), linearity (0.1-46.8 μg/mL, r > 0.9994), stability (0.35%-3.29%), and accuracy (80.39%-104.31%). In the extraction experiment, antioxidants, BHT, 1010, 1330, 1076, and 168, and their degradation products, 1310 and DBP, were detected in the packaging materials. Only 1310 was detected in the migration experiment. The maximum daily dosage of sodium chloride for blood transfusion is three bags, and the content of 1310 in long-term testing samples is from 0 to 12 months ranging from 37.44 μg/3 bags to 48.71 μg/3 bags. The daily intake of 1310 did not exceed 48.71 μg, which was much lower than its permitted daily exposure (PDE, 300 μg/day). Therefore, the antioxidants and their degradation products migrating into the drug solution would not cause drug safety risks.

Computational Methods for the Identification of Molecular Targets of Toxic Food Additives. Butylated Hydroxytoluene as a Case Study

Butylated hydroxytoluene (BHT) is one of the most commonly used synthetic antioxidants in food, cosmetic, pharmaceutical and petrochemical products. BHT is considered safe for human health; however, its widespread use together with the potential toxicological effects have increased consumers concern about the use of this synthetic food additive. In addition, the estimated daily intake of BHT has been demonstrated to exceed the recommended acceptable threshold. In the present work, using BHT as a case study, the usefulness of computational techniques, such as reverse screening and molecular docking, in identifying protein-ligand interactions of food additives at the bases of their toxicological effects has been probed. The computational methods here employed have been useful for the identification of several potential unknown targets of BHT, suggesting a possible explanation for its toxic effects. In silico analyses can be employed to identify new macromolecular targets of synthetic food additives and to explore their functional mechanisms or side effects. Noteworthy, this could be important for the cases in which there is an evident lack of experimental studies, as is the case for BHT.

Butylated hydroxytoluene induces hyperactivity and alters dopamine-related gene expression in larval zebrafish (Danio rerio)

Butylated hydroxytoluene (BHT) is one of the most frequently used synthetic phenolic antioxidants added to food and consumer products such as plastics as a preservative. Due to its high production volume, BHT has been detected in aquatic environments, raising concerns about sub-lethal toxicity. However, there are limited toxicological data for BHT, especially in fish. In this study, zebrafish embryos were exposed to BHT at concentrations ranging 0.01-100 μM for up to 6 days post fertilization (dpf). Acute toxicity was assessed, and experiments revealed that BHT had a 96 h LC50 value of 57.61 μM. At sub-lethal doses (0.1-60 μM), BHT markedly decreased heart rates of zebrafish embryos at 48 h and 72 h by ∼25-30%. Basal and maximal respiration of zebrafish embryos at 24 hpf were decreased by 59.3% and 41.4% respectively following exposure to 100 μM BHT. Behavior in zebrafish was measured at 6 dpf following exposures to 0.01-10 μM BHT. Locomotor behaviors (e.g. total distance moved and velocity) were significantly increased in larvae at doses higher than 0.1 μM BHT. In addition, dark-avoidance behavior was decreased following exposure to 0.01 μM BHT, while conversely, it was increased in zebrafish exposed to 0.1 μM BHT. To investigate potential underlying mechanisms that could explain behavioral changes, transcripts involved in dopamine signaling were measured. Relative expression of dat mRNA was increased in larval fish from the 0.01 μM BHT treatment, while there were no effects on dat mRNA levels at higher concentrations. The mRNA levels of drd3 were decreased in zebrafish from the 1 μM BHT treatment. Taken together, BHT can affect the expression of the dopamine system, which is hypothesized to be related to the abnormal anxiety-associated behavior of larval zebrafish.

Prevalence, Biotransformation, and Maternal Transfer of Synthetic Phenolic Antioxidants in Pregnant Women from South China

Synthetic phenolic antioxidants (SPAs) have been identified as an emerging group of contaminants in recent years. However, there are significant gaps in our knowledge of human prenatal exposure to these synthetic chemicals. In this study, a set of eight SPAs and four major transformation products (TPs) were systematically analyzed in matched samples of maternal plasma, cord plasma, and placenta from a population of pregnant women. Five of the eight target SPAs and all four target TPs were frequently detected in the maternal-placental-fetal unit, indicating prenatal exposure to SPAs and the transfer of SPAs across the placenta. In the three matrices, 2,6-di-tert-butyl-hydroxytoluene (BHT), 2,4-di-tert-butylphenol (DBP), and 2,2'-methylenebis(4-methyl-6-tert-butylphenol) (AO 2246) were identified as the most abundant SPAs, while 2,6-di-tert-butyl-1,4-benzoquinone (BHT-Q) and 2,6-di-tert-butyl-4-hydroxy-4-methyl-2,5-cyclohexadienone (BHT-quinol) were identified as the predominant TPs of BHT. In the maternal plasma, concentrations of both BHT-Q and BHT-quinol were significantly correlated with BHT (p < 0.001), suggesting that the two TPs mainly originated from the biotransformation of BHT itself in pregnant women. The transplacental transfer efficiencies (TTEs) of the SPAs and TPs were structure-dependent and generally less than 1. Significantly higher TTEs for four target TPs than their parent BHT were identified. To our knowledge, this study provides the first evidence that SPAs and TPs transfer across the placenta in pregnant women.

Unexpectedly high concentrations of 2,4-di-tert-butylphenol in human urine

Synthetic phenolic antioxidants (SPAs) have received increasing attention due to the reports of toxicity and environmental contamination. Nevertheless, limited information was available on human burdens of these SPAs, with the exception of 2,6-di-tert-butyl-4-methylphenol (BHT). In our study, BHT as well as six other SPAs were analyzed in human urine samples from United States donors. Three SPA congeners were detected in human urine: BHT, 2,4-di-tert-butylphenol (DBP), and 3-tert-butyl-4-hydroxyanisole (BHA). BHT, which is the congener received most concerns, was detected at low concentrations [geometric mean (GM): 0.06 ng/mL], whereas four of its metabolites were detected at relatively high concentrations (GM: 1.68 ng/mL). Surprisingly, DBP was detected at extremely high concentrations (GM: 18.3 ng/mL). The concentrations of DBP (GM: 25.8 ng/mL), BHT (0.853 ng/mL), and metabolites (GM: 10.5 ng/mL) increased significantly after the urine samples were hydrolyzed by β-glucuronidase (p < 0.01), indicating the prevalence of the conjugated forms of SPAs and their metabolites in human urine. DBP, which has previously received little attention, was the predominant congener, contributing 88.2% and 63.6% to total target concentrations in the urine samples before and after β-glucuronidase hydrolysis, respectively. Thus, previous studies have vastly underestimated the burdens of SPAs to humans. To our knowledge, this is the first study revealing the presence of DBP in human urine.

Occurrence of plastic additives in outdoor air particulate matters from two industrial parks of Tarragona, Spain: Human inhalation intake risk assessment

Plastic additives include several kinds of chemicals that are added to the polymer matrix to improve the final product quality and prevent deterioration effects. They are used in a large quantity of materials, so their presence in the environment is expected. This study has developed and validated a method based on gas chromatography-mass spectrometry after pressurised liquid extraction to determine sixteen plastic additives including UV-stabilizers, aromatic and phenolic antioxidants and some of their degradation products in particulate matter (PM₁₀) from outdoor air. Apparent recoveries were above 85% for most of compounds and low detection limits (pg m^-3) were achieved. This is the first study to determine these types of contaminant in the PM₁₀ of outdoor air from two locations surrounded by different industries. Various compounds were found in almost all samples; BHT, BHT-Q, 2,4-DTBP, BHT-CHO, UV320, UV328, Irgafos168 and Iragonx1076, with concentrations ranging from < MQL to 2860 pg m^-3. Estimated daily intakes (EDIs) via ambient inhalation were calculated for each polymer additive and for different subpopulation groups classified by age. Two possible exposure scenarios (low, based on geometric mean, and high, 95th percentile) were simulated, and 0.51 ng kg_bw^-1 day^-1 was the EDI in the worst case scenario for children.

Synthetic phenolic antioxidants and transformation products in dust from different indoor environments in Toronto, Canada

Synthetic phenolic antioxidants (SPAs) are a class of anthropogenic antioxidants that are widely used in a large variety of commercial products. Although several SPAs have been listed as targets for risk assessment by Environment and Climate Change Canada, little data are available on the occurrence of SPAs in the Canadian environment. In this study, eighty-three indoor dust samples were collected from offices and homes in Toronto. Eight SPAs were detected at concentrations ranging from 67.2 to 1.55e4 ng/g, with a geometric mean (GM) concentration of 1.49e3 ng/g, among which 2,6-di-tert-butyl-4-methylphenol (BHT) was the primary congener and had a GM concentration of 658 ng/g. Four BHT transformation products (TPs) were also detected in the indoor dust samples, with concentrations ranging from 40.4 to 1.27e4 ng/g and a GM concentration of 883 ng/g. No significant concentration difference was observed between the office and home dust samples for either the summed target SPA or TP concentrations (p > 0.05). The calculated estimated daily intakes of these chemical contaminants (0.004-10.0 ng/kg BW/day) suggest that they pose no immediate health risk to the Canadian population. To the best of our knowledge, this is the first report of the occurrence of these chemical contaminants and their transformation products in Canadian indoor environments, and furthermore the first detection of 4-tert-butyl-phenol in an environmental sample.

Distribution and fate of synthetic phenolic antioxidants in various wastewater treatment processes in Canada

Synthetic phenolic antioxidants (SPAs) are of emerging concern due to their potential environmental risks. However, the environmental occurrence and fate of SPAs are poorly understood. In this study, 13 SPAs were analyzed in 70 liquid and 21 solid samples from 12 wastewater treatment plants (WWTPs) in 2016 to investigate the distribution and composition of SPAs in different wastewater treatment processes in Canada. Wastewater samples were liquid-liquid extracted and biosolids were treated using ultrasonic assisted solvent extraction. SPAs were analyzed by ultra-performance liquid chromatography-tandem mass spectrometry. The concentrations of total SPAs were in the ranges of 71-3193 ng L^-1 in influent, less than method quantification limits (MQLs)-520 ng L^-1 in effluent, and 479-4794 ng g^-1 in biosolids (dry weight (dw)). SPAs were effectively removed (median >75%) from the liquid stream in most WWTPs. In one aerated lagoon and two primary treatment sites, low removal efficiency (median -26%-43%) was observed for 4-tert-octylphenol (4-tOP). These results indicate that wastewater effluent is a vector for SPAs, including the endocrine disruptor 4-tOP, to aquatic environments. The mass balance approximation found major removal mechanisms are sludge sorption/separation and degradation. A preliminary risk assessment suggested that most SPAs in WWTP effluent were unlikely to pose ecotoxicological risks to aquatic organisms in the receiving waters. Future research should evaluate the environmental risks of SPAs associated with land application of biosolids and investigate the occurrence and fate of the degradation products of these contaminants.

Synthetic phenolic antioxidants and their major metabolites in human fingernail

Synthetic phenolic antioxidants (SPAs) have been widely used in foods, polymers, and cosmetics, but very limited information is available about their occurrence in human tissues. In this study, five SPAs, namely 2,6-di-tert-butyl-4-methylphenol (BHT), 2-tert-butyl-4-hydroxyanisole (BHA), propyl-, octyl-, and dodecyl-gallate (PG, OG, and DG), and four major metabolites of BHT, including 3,5-di-tert-butyl-4 -hydroxybenzaldehyde (BHT-CHO), 2,6-di-tert-butyl-4-(hydroxymethyl) phenol (BHT-OH), 3,5-di-tertbutyl-4-hydroxybenzoic acid (BHT-COOH), and 2,6-di-tert-butyl-1,4-benzoquinone (BHT-Q), were determined in human fingernail samples collected from Nanjing, China. Total concentrations of the nine target analytes (∑₉SPAs) were 523-14,000 ng/g. BHT was the predominant SPA compound and detected in all samples at a range of 309-11,400 ng/g. The ∑₉SPAs was negatively correlated with age of fingernail donors (p < 0.05). In addition, indoor dust samples from the living places of the fingernail providers were collected with aim to better understand the SPA exposure pathways. A positive correlation (p < 0.05) was found only for DG concentrations between paired fingernail and dust samples, while not for other SPAs, suggesting that SPAs accumulated in fingernails may not be mainly from indoor dust. SPAs were measured for the first time in human fingernail, and the elevated concentrations in fingernail suggest that the health risk of SPAs should be paid more attention due to their bioaccumulation potential in human body. Further studies are warranted about exposure pathway, distribution and metabolism of SPAs in human body.

Synthetic Phenolic Antioxidants and Their Metabolites in Mollusks from the Chinese Bohai Sea: Occurrence, Temporal Trend, and Human Exposure

Synthetic phenolic antioxidants (SPAs) are a group of chemicals widely used in various daily necessities and industrial supplies. Little is known about the occurrence and bioaccumulation potential of SPAs in marine biota. In this study, five commonly used SPAs and their four metabolites were detected in mollusk samples ( n = 274) collected from the Chinese Bohai Sea during 2006-2016 and the spatiotemporal distribution and bioaccumulation of SPAs in mollusks were examined. The concentrations of 2,6-di- tert-butyl-4-hydroxytoluene (BHT) ranged from 383 to 501000 ng/g (geometric mean: 3450 ng/g), accounting for 79.4% of the total concentrations of SPAs and their metabolites (∑₉SPAs). The mollusk species, Rapana venosa (RAP), contained higher levels of BHT than other species, suggesting that Rap could be used as a potential bioindicator for monitoring of the BHT pollution in the investigated region. The ∑₉SPAs concentrations in mollusks gradually increased with years and a significant positive correlation ( r = 0.900, p < 0.05) was found between ∑₉SPAs concentration and trophic level of the mollusks. The trophic magnification factor value of ∑₉SPAs was calculated as 16.1, suggesting a high biomagnification potential of SPAs in mollusks in the Chinese Bohai Sea. The estimated daily intake of ∑₉SPAs through dietary ingestion of mollusks was up to 602 and 789 ng/kg bw/day for adults and children and teenagers, respectively. The principal component analysis result suggests that there exists a common source for three gallates (OG, DG, and PG), and BHT metabolites in mollusks were mainly derived from degradation of BHT. This is the first study to report the occurrence and bioaccumulation potentials of SPAs and their metabolites in invertebrate species from coastal marine environments.