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

Prevalence of synthetic phenolic antioxidants in food contact materials from China and their implications for human dietary exposure through take-away food

The application of disposable tableware has increased substantially in recent times due to the rapidly growing food delivery business in China. Synthetic phenolic antioxidants (SPAs) are widely used in food contact materials (FCMs) to delay the process of oxidation; however, their compositions, concentrations, and potential health hazards remain unclear. Therefore, FCMs comprised of five materials obtained from 19 categories (n = 118) in China were analyzed for SPAs concentrations. FCMs have been found to contain a variety of SPAs, with ∑SPAs concentrations ranging from 44.18 to 69,485.12 μg/kg (median: 2615.63 μg/kg). The predominant congeners identified in the sample include 2,4-di-tert-butylphenol (2,4-DTBP), 2,6-di-tert-butylphenol (2,6-DTBP), and 2,6-di-tert-butyl-p-benzoquinone (BHT-Q) with a median concentration of 885.75, 555.45 and of 217.44 μg/kg, respectively. Milky tea paper cups, instant noodle buckets, milky teacups, and disposable cups showed high levels of SPAs. 2,2'-methylenebis(4-methyl-6-tert-butylphenol) (AO 2246) was predominantly detected in polyethylene and polyethylene terephthalate-based products. The migration test identified disposable plastic cups and bowls as the predominant FCMs and 2,4-DTBP as the dominant SPA. The exposure risk of SPAs decreased with age. In children, the estimated daily intake of ∑SPAs from FCMs was determined to be 17.56 ng/kg body weight/day, which was 8.3 times higher than that of phthalic acid esters. The current findings indicate the potential ingestion risk of SPAs during the daily life application of multiple FCM categories.

A study on the performance, structure, composition, and release behavior changes of polybutylene adipate terephthalic acid (PBAT) film during food contact

Polybutylene adipate terephthalic acid (PBAT) is an emerging biodegradable material in food packaging. However, concerns have been raised regarding the potential hazards it could pose to food safety. In this study, the changes of PBAT films during food contact and the release of small molecules were inestigated by a multiscale approach. On a macro-scale, the surface roughness of the films increased with the reduction in the concentration of food simulants and the increase in contact temperatures, especially after immersion in acidic food environments. On a micro-scale, the crystallinity (Xc) and degradation indexes (DI) of the films increased by 5.7-61.2% and 7.8-48.6%, respectively, which led to a decrease in thermal stability. On a scale approaching the molecular level, 2,4-di-tert-butylphenol (2,4-DTBP) was detected by gas chromatography-mass spectrometry (GC-MS/MS) with the highest migration content, and the release behavior of 2,4-DTBP was further investigated by migration kinetics. In addition, terephthalic acid (TPA), a hydrolysis product of PBAT, was detected in acidic food environments by liquid chromatography-mass spectrometry (LC-MS/MS). The results of this study could provide practical guidance and assistance to promote sustainable development in the field of food packaging.

An in-situ versatile screening method for identifying SVOC sources in indoor environments

Indoor semivolatile organic compounds (SVOCs) pose a substantial threat to human health. However, identifying the sources of these emissions has been challenging owing to the scarcity of convenient and practical on-site methodologies. Herein, a novel method for source screening was proposed using aluminum silicate sampling strips to adsorb SVOCs from the surface air of indoor materials. The adsorbed SVOC levels indicate the emission intensity of these materials into indoor environments. Additionally, compact sampling strips can be readily fixed to any vertical surface using a static sticker, facilitating the characterization of various materials in practical settings. Laboratory-simulated experiments demonstrated the capability of the proposed method to differentiate between source and non-source materials within a 10-cm distance in the same space. In practical scenarios, the primary emission sources identified via this method exhibited a consistent correlation with the contents of the corresponding materials obtained from the traditional solvent-extraction method. As the adsorbed SVOCs were directly transferred to a GC-MS through thermal desorption instead of the solvent-extraction procedure, the proposed method demonstrated several-fold improvements in analytical sensitivity and efficiency. Using this versatile screening technique, some emerging and important SVOC species were identified within specific indoor materials. Eliminating these sources has been demonstrated as an effective approach to mitigate SVOC pollution. Overall, the proposed method offers a powerful tool for managing indoor pollutants and safeguarding human health.

The presence and physico-chemical properties of microplastics in seawater, sediment, and several organs of the spotted scat fish (Scatophagus argus, Linnaeus, 1766) collected from different locations along the East Java coast in Indonesia

A comprehensive study was undertaken to examine the contamination of spotted scat fish (Scatophagus argus) with microplastics (MP) in various locations along the East Java coast of Indonesia. The purpose of this study was to collect detailed information regarding the abundance, color, shape, size, type of polymer, and chemical components of the MP. The findings of this study indicated that MP exhibiting distinct attributes-including a specific fiber type, black coloration, and a size range of 1000- <5000 μm-was most abundant in the gill, stomach, and intestines of spotted scat fish of varying lengths. And MP with a size range of 100-<500 μm was prevalent in the sediment. MP with black fragments measuring less than 100 μm in diameter were found primarily in seawater. A positive correlation was identified between fish length and MP abundance in the intestines, as indicated by the Spearman correlation coefficient. Conversely, a negative correlation was detected between fish length and MP abundance in the gills. The findings of the Fourier transform infrared spectroscopy and Gas chromatography-mass spectrometry analyses, which indicate the presence of various polymers and chemical substances including plasticizers (e.g., diethyl phthalate, decane, and eicosane), stabilizers (2-piperidinone, hexadecanoic acid, mesitylene, and 2,4-Di-tert-butylphenol), and flame retardant (cyclododecene), in fish, are of the utmost importance. These substances have the potential to endanger the health of both animals and humans if they are ingested through the food chain.

Ubiquity of Synthetic Phenolic Antioxidants in Children's Cerebrospinal Fluid from South China: First Evidence for Their Penetration across the Blood-Cerebrospinal Fluid Barrier

Synthetic phenolic antioxidants (SPAs) and relevant transformation products (TPs) are potentially neurotoxic pollutants to which humans are widely exposed. However, their penetration behavior across the brain barrier and associated exposure to the central nervous system (CNS) remain unknown. This study is the first to investigate a wide range of 30 SPAs and TPs, including emerging SPAs, in matched serum and cerebrospinal fluid (CSF) samples from children in Guangzhou, China. Sixty-two children of either sex aged <14 years with nonbloody CSF and complete clinical information were included. The findings demonstrated the ubiquitous occurrence of many SPAs and TPs, particularly BHT, 2,4-di-tert-butylphenol (DBP), AO 1010, AO 1076, BHT-Q, and BHT-quinol, not only in serum but also in the CSF. Median total concentrations of SPAs and TPs were up to 22.0 and 2.63 ng/mL in serum and 14.5 and 2.11 ng/mL in CSF, respectively. On calculating the penetration efficiencies across the blood-CSF barrier (BCSFB) (RCSF/serum, CCSF/Cserum) for selected SPAs and TPs, their RCSF/serum values (median 0.52-1.41) were highly related to their physicochemical properties, indicating that passive diffusion may be the potential mechanism of BCSFB penetration. In addition, the RCSF/serum values were positively correlated with the barrier permeability index RAlb (AlbuminCSF/Albuminserum), indicating that barrier integrity is an important determinant of BCSFB penetration. Overall, these results will improve our perception of human internal exposure to SPAs and lay a solid foundation for assessing the risk of CNS exposure to various SPAs.

Effects of the plastic additive 2,4-di-tert-butylphenol on intestinal microbiota of zebrafish

Plastic additives such as the antioxidant 2,4-di-tert-butylphenol (2,4-DTBP) have been widely detected in aquatic environments, over a wide range of concentrations reaching 300 μg/L in surface water, potentially threatening the health of aquatic organisms and ecosystems. However, knowledge of the specific effects of 2,4-DTBP on aquatic vertebrates is still limited. In this study, adult zebrafish were exposed to different concentrations of 2,4-DTBP (0, 0.01, 0.1 and 1.0 mg/L) for 21 days in the laboratory. The amplicon sequencing results indicated that the diversity and composition of the zebrafish gut microbiota were significantly changed by 2,4-DTBP, with a shift in the dominant flora to more pathogenic genera. Exposure to 2,4-DTBP at 0.1 and 1.0 mg/L significantly increased the body weight and length of zebrafish, suggesting a biological stress response. Structural assembly defects were also observed in the intestinal tissues of zebrafish exposed to 2,4-DTBP, including autolysis of intestinal villi, adhesions and epithelial detachment of intestinal villi, as well as inflammation. The transcriptional expression of some genes showed that 2,4-DTBP adversely affected protein digestion and absorption, glucose metabolism and lipid metabolism. These results are consistent with the PICRUSt2 functional prediction analysis of intestinal microbiota of zebrafish exposed to 2,4-DTBP. This study improves our understanding of the effects of 2,4-DTBP on the health of aquatic vertebrates and ecosystems.

Thermal decomposition characteristics of BHT and its peroxide (BHTOOH)

2,6-Di-tert-butyl-4-methylphenol (BHT) is an excellent antioxidant that is easily oxidized to 2,6-di-tert-butyl-4-hydroperoxyl-4-methyl-2,5-cyclohexadienone (BHTOOH). For the safety of BHT production and usage, it is meaningful to study the thermal stability and decomposition properties of BHT and BHTOOH. In this paper, the thermal decomposition properties of BHT and BHTOOH were compared by the mini closed pressure vessel test (MCPVT) and differential scanning calorimetry (DSC). Their kinetics of thermal decomposition were studied using thermogravimetric analysis (TGA). The thermal decomposition products of BHT and BHTOOH were analyzed by gas chromatography-mass spectrometry (GC-MS). The results show that there was no significant change in temperature pressure when BHT was warmed up under a nitrogen atmosphere, indicating that BHT was stable within 400 K. The thermal decomposition reaction of BHTOOH was rapid with an initial reaction temperature of 375.2 K. The initial exothermic temperature (Ti) and heat release (QDSC) of DSC were 384.9 K and 865.0 J g-1, respectively. The apparent activation energies (Ea) for the thermal decomposition reactions of BHT and BHTOOH calculated by the Kissinger method were 151.8 kJ mol-1 and 66.07 kJ mol-1, respectively. The main decomposition products of BHT were isobutene and 2-tert-butyl-4-methylphenol. The thermal decomposition products of BHTOOH included BHT, 2,6-di-tert-butyl-4-ethylphenol, 3,5-di-tert-butyl-4-hydroxybenzaldehyde, 4,4'-(1,2-ethanediyl) bis [2,6-bis (1,1-dimethylethyl) phenol, etc. Based on the thermal decomposition behavior and products, the reaction pathway has been described. These results indicate that BHT is a potential thermal hazard during production, storage and application. For the safety of the chemical industry, the oxidation of BHT should be avoided.

The hidden diet: Synthetic antioxidants in packaged food and their impact on human exposure and health

Synthetic antioxidants (AOs) are commonly used in everyday items and industrial products to inhibit oxidative deterioration. However, the presence of AOs in food packaging and packaged foods has not been thoroughly documented. Moreover, studies on human exposure to AOs through skin contact with packaging or ingesting packaged foods are limited. In this study, we analyzed twenty-three AOs-including synthetic phenolic antioxidants (SPAs) and organophosphite antioxidants (OPAs)-along with six transformation products in various food samples and their packaging materials. We found AOs in food products at concentrations ranging from 1.30 × 103 to 1.77 × 105 ng/g, which exceeded the levels in both outer packaging (6.05 × 102-3.07 × 104 ng/g) and inner packaging (2.27 × 102-1.09 × 105 ng/g). The most common AOs detected in foodstuffs were tris(2,4-di-tert-butylphenyl) phosphate (AO168O), butylated hydroxytoluene (BHT), and octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (AO1076), together constituting 95.7 % of the total AOs found. Our preliminary exposure assessment revealed that dietary exposure-estimated at a median of 2.55 × 104 ng/kg body weight/day for children and 1.24 × 104 ng/kg body weight/day for adults-is a more significant exposure route than dermal contact with packaging. Notably, four AOs were identified in food for the first time, with BHT making up 76.8 % and 67.6 % of the total BHT intake for children and adults, respectively. These findings suggest that food consumption is a significant source of BHT exposure. The estimated daily intakes of AOs via consumption of foodstuffs were compared with the recommended acceptable daily intake to assess the risks. This systematic investigation into AOs contributes to understanding potential exposure and health risks associated with AOs in packaged foods. It emphasizes the need for further evaluation of human exposure to these substances.

Exposure to environmental levels of 2,4-di-tert-butylphenol affects digestive glands and induces inflammation in Asian Clam (Corbicula fluminea)

2,4-Di-tert-butylphenol (2,4-DTBP) is used as an antioxidant added to plastics. Due to its potential toxicity and relatively high concentrations in environments and presence in human tissue, concern has been raised for 2,4-DTBP as a contaminant associated with adverse health outcomes. However, studies on the toxicity of 2,4-DTBP are relatively limited, especially for benthic aquatic organisms. In this study, Asian clams (Corbicula fluminea) were exposed to environmentally relevant concentrations of 2,4-DTBP (0.01-1 μM, corresponding to 2.06-206.32 μg/L) for 21 days. Accumulation of 2,4-DTBP was noted in both gills and digestive glands, with the latter presenting as the primary target tissue. Increased damage rate of digestive tube and cellular DNA damage were observed in the digestive glands of 2,4-DTBP exposed clams. The injury was attributed to the imbalance of the antioxidant system, characterized by elevated oxidative stress and inflammation (upregulation of ROS, MDA, NO, and pro-inflammatory factors). In contrast, upon 2,4-DTBP exposure, antioxidant system in gills was activated, while ROS and NO were not promoted. Moreover, NF-κB and IL-1 were significantly decreased. These results suggested that biochemical mechanisms were activated in gills to maintain homeostasis. Internal exposure in the digestive gland was significantly correlated with the biochemical biomarkers tested, underscoring the potential risk associated with the bioaccumulation of 2,4-DTBP from contaminated environments. These findings provide novel insights into toxicity of 2,4-DTBP in bivalves, contributing valuable knowledge to risk assessment and chemical management.

Occurrence of p-phenylenediamine antioxidants in human urine

General populations are widely exposed to various p-phenylenediamine antioxidants (PPDs). N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), a typical p-phenylenediamine antioxidant, has been detected in human urine samples. However, the occurrence of other widely used PPDs in human urine is still unclear. This study comprehensively characterized the occurrence of 9 PPDs in human urine from 151 Chinese adults. Our results showed that all target PPDs were detected in human urine samples, with the total concentrations of PPDs ranging from 0.41 to 38 ng/mL. PPDs in human urine was dominated by 6PPD (mean 1.2 ng/mL, range < LOD - 3.8 ng/mL), followed by N-phenyl-N'-cyclohexyl-p-phenylenediamine (CPPD; 0.85 ng/mL, Collapse

Key Words

• 6PPD
• Human exposure
• Human urine
• PPDs
• Synthetic antioxidants

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MESH Headings

• Adult
• Humans
• Male
• Female
• Antioxidants
• Phenylenediamines
• Nitro Compounds

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Grants Collapse

Affiliation(s)

Weili Mao Department of Pharmacy, Quzhou Affiliated Hospital of Wenzhou Medical University, Quzhou People's Hospital, Quzhou, Zhejiang 324000, PR China
Hangbiao Jin Key Laboratory of Microbial Technology for Industrial Pollution Control of Zhejiang Province, College of Environment, Zhejiang University of Technology, Hangzhou, Zhejiang 310032, PR China; Innovation Research Center of Advanced Environmental Technology, Eco-Industrial Innovation Institute ZJUT, Quzhou, Zhejiang 324400, PR China
Ruyue Guo Key Laboratory of Microbial Technology for Industrial Pollution Control of Zhejiang Province, College of Environment, Zhejiang University of Technology, Hangzhou, Zhejiang 310032, PR China
Ping Chen Department of Pharmacy, Quzhou Affiliated Hospital of Wenzhou Medical University, Quzhou People's Hospital, Quzhou, Zhejiang 324000, PR China
Songyang Zhong Department of Pharmacy, Quzhou Affiliated Hospital of Wenzhou Medical University, Quzhou People's Hospital, Quzhou, Zhejiang 324000, PR China
Xilin Wu Department of Pharmacy, Quzhou Affiliated Hospital of Wenzhou Medical University, Quzhou People's Hospital, Quzhou, Zhejiang 324000, PR China.

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Disposable Plastic Waste and Associated Antioxidants and Plasticizers Generated by Online Food Delivery Services in China: National Mass Inventories and Environmental Release

China's online food delivery (OFD) services consume enormous amounts of disposable plastics. Here, we investigated and modeled the national mass inventories and environmental release of plastics and chemical additives in the plastic. The extra-tree regression identified six key descriptors in determining OFD sales in Chinese cities. Approximately 847 kt of OFD plastic waste was generated in 2021 (per capita 1.10 kg/yr in the megacities and 0.39 kg/yr in other cities). Various additives were extensively detected, with geomean concentrations of 140.96, 4.76, and 0.25 μg/g for ∑8antioxidants, ∑21phthalates, and bisphenol A (BPA), respectively. The estimated mass inventory of these additives in the OFD plastics was 164.7 t, of which 51.1 t was released into the atmosphere via incineration plants and 51.0 t was landfilled. The incineration also released 8.07 t of polycyclic aromatic hydrocarbons and 39.1 kt of particulate matter into the atmosphere. Takeout food may increase the dietary intake of phthalates and BPA by 30% to 50% and raise concerns about considerable exposure to antioxidant transformation products. This study provides profound environmental implications for plastic waste in the Chinese OFD industry. We call for a sustainable circular economy action plan for waste disposal, but mitigating the hazardous substance content and their emissions is urgent.

The maternal hair metabolome is capable of discriminating intrahepatic cholestasis of pregnancy from uncomplicated pregnancy

Introduction

Intrahepatic cholestasis of pregnancy (ICP) is a pregnancy-specific liver disease associated with elevated bile acids in the blood. Diagnosis typically only occurs after the manifestation of clinical symptoms and the metabolic mechanisms underlying its development remain unclear. The aim of this study was to investigate potential specific metabolites and the underlying metabolic changes occurring during the development of ICP in the maternal plasma and hair metabolomes of women diagnosed with either ICP or having a healthy pregnancy.

Methods

A total of 35 Chinese women with ICP and 42 healthy pregnancies were enrolled in our study. Plasma and hair samples, total bile acid levels (TBA), alanine transaminase levels (ALT), aspartate aminotransferase levels (AST), and additional clinical information were collected during the third trimester. Metabolites from maternal plasma and hair segments collected pre-conception and analyzed using gas chromatography-mass spectrometry (GC-MS).

Results

Three plasma metabolites (p < 0.05, q < 0.38) and 21 hair metabolites (p < 0.05, q < 0.05) were significantly different between ICP and healthy pregnancies. A combination of the eight most significant hair metabolites in a multivariate receiver operating characteristic curve model showed the best area under the curve (AUC) was 0.885, whereas the highest AUC using metabolites from plasma samples was only 0.74. Metabolic pathway analysis revealed 32 pathways were significantly (p and q values < 0.05) affected in the hair samples of patients with ICP. Pathways associated with glutathione metabolism and ABC transporters were affected. No metabolic pathways were significantly affected in plasma.

Discussion

Overall, this study showed that the hair metabolome could be more useful than the plasma metabolome for distinguishing ICP from normal pregnancy.

Alkylphenols disrupt estrogen homeostasis via diradical cross-coupling reactions: A novel pathway of endocrine disruption

Estrogen, being an essential class of sex hormone, is an important target of endocrine disruption chemicals. It is well known that environmental disruptors could activate or inhibit estrogen receptors, acting as agonists or antagonists, and thus affect the circulating estrogen concentrations. Here, we report enzyme-mediated diradical cross-coupling reactions between alkylphenols (e.g., 2,4-di-tert-butylphenol [DBP], 4-nonylphenol [4-NP], and 4-tert-octylphenol [4-t-OP]) and estrogens (e.g., estradiol [E2]) that generate coupling metabolites and disrupt estrogen homeostasis. Among the phenolic xenobiotics, the screening of metabolic products revealed that alkylphenols had the highest reaction activities and generated coupling metabolites with high abundances (DBP-O-E2, 4-t-OP-O-E2, and 4-NP-O-E2). The coupling reactions were catalyzed by cytochrome P450 3A4 (CYP3A4) and verified by the detection of the coupling products in general populations. In vitro and in vivo exposures together with CYP3A4 inhibition demonstrated that cross-coupling reactions of phenols and E2 significantly reduced the normal levels of E2. We further established a unique spin-trapping-based high-throughput screening method to show the existence of diradicals in the coupling reaction. Density functional theory calculations revealed that spin aromatic delocalization was the fundamental cause of the high rebound barrier and sufficient lifetime of phenoxy radicals that enabled phenolic cross-coupling triggered by cytochrome P450. The identified mechanistic details for diradical cross-coupling reactions provide a novel pathway for phenolic chemicals to disrupt estrogen homeostasis.

Synthetic Antioxidants as Contaminants of Emerging Concern in Indoor Environments: Knowns and Unknowns

Synthetic antioxidants, including synthetic phenolic antioxidants (SPAs), amine antioxidants (AAs), and organophosphite antioxidants (OPAs), are essential additives for preventing oxidative aging in various industrial and consumer products. Increasing attention has been paid to the environmental contamination caused by these chemicals, but our understanding of synthetic antioxidants is generally limited compared to other emerging contaminants such as plasticizers and flame retardants. Many people spend a significant portion (normally greater than 80%) of their time indoors, meaning that they experience widespread and persistent exposure to indoor contaminants. Thus, this Perspective focuses on the problem of synthetic antioxidants as indoor environmental contaminants. The wide application of antioxidants in commercial products and their demonstrated toxicity make them an important family of indoor contaminants of emerging concern. However, significant knowledge gaps still need to be bridged: novel synthetic antioxidants and their related transformation products need to be identified in indoor environments, different dust sampling strategies should be employed to evaluate human exposure to these contaminants, geographic scope and sampling scope of research on indoor contamination should be broadened, and the partition coefficients of synthetic antioxidants among different media need to be investigated.

Migration Studies and Endocrine Disrupting Activities: Chemical Safety of Cosmetic Plastic Packaging

The endocrine activity and endocrine disruptor (ED) chemical profiles of eleven plastic packaging materials covering five major polymer types (3PET, 1HDPE, 4LDPE, 2 PP, and 1SAN) were investigated using in vitro cell-based reporter-gene assays and a non-targeted chemical analysis using gas chromatography coupled to mass spectrometry (GC-MS). To mimic cosmetic contact, six simulants (acidic, alkaline, neutral water, ethanol 30%, glycerin, and paraffin) were used in migration assays performed by filling the packaging with simulant. After 1 month at 50 °C, simulants were concentrated by Solid Phase Extraction (SPE) or Liquid-Liquid Extraction (LLE). The migration profiles of seven major endocrine disrupting chemicals detected from GC-MS in the different materials and simulants were compared with Estrogen Receptor (ER) and Androgen Receptor (AR) activities. With low extraction of ED chemicals in aqueous simulants, no endocrine activities were recorded in the leachates. Paraffin was shown to be the most extracting simulant of antiandrogenic chemicals, while glycerin has estrogenic activities. Overall, ED chemical migration in paraffin was correlated with hormonal activity. The NIAS 2,4-di-tert-butyl phenol and 7,9-di-tert-butyl1-oxaspiro (4,5) deca-6,9-diene-2,8-dione were two major ED chemicals present in all polymers (principally in PP and PE) and in the highest quantity in paraffin simulant. The use of glycerin and liquid paraffin as cosmetic product simulants was demonstrated to be relevant and complementary for the safety assessment of released compounds with endocrine activities in this integrated strategy combining bioassays and analytical chemistry approaches.

A review of the occurrence, metabolites and health risks of butylated hydroxyanisole (BHA)

Butylated hydroxyanisole (BHA) is mainly used as a food additive due to its antioxidant properties, which prevent or delay oxidation reactions and extend the storage life of products. The widespread use of BHA has led to its extensive presence in various environmental matrices and human tissues. Food intake is the main route of human exposure to BHA. Under different conditions, BHA can produce different metabolites, with tert-butyl hydroquinone (TBHQ) being one of the major products. Several studies have shown that BHA could cause thyroid system damage, metabolic and growth disorders, neurotoxicity, and carcinogenesis. Mechanisms such as endocrine disruption, genotoxicity, disturbances of energy metabolism, reactive oxygen species (ROS) production, signaling pathways, and imbalances in calcium homeostasis appear to be associated with the toxic effects of BHA. Avoiding the toxic effects of BHA to the maximum extent possible is a top priority. Finding safe, non-toxic and environmentally friendly alternatives to BHA should be the focus of subsequent research. In all, this review summarized the current situation related to BHA and might make recommendations for future research directions. © 2023 Society of Chemical Industry.

3-tert-Butyl-4-hydroxyanisole Perturbs Differentiation of C3H10T1/2 Mesenchymal Stem Cells into Brown Adipocytes through Regulating Smad Signaling

3-tert-Butyl-4-hydroxyanisole (3-BHA), one of the most commonly used antioxidants in foodstuffs, has been identified as an environmental endocrine disruptor (EED) with obesogenic activity. Given the increasing concern on EED-caused dysfunction in lipid metabolism, whether 3-BHA could influence the development of brown adipocytes is worthy of being explored. In this study, the effect of 3-BHA on the differentiation of C3H10T1/2 mesenchymal stem cells (MSCs) into brown adipocytes was investigated. Exposure to 3-BHA promoted lipogenesis of the differentiated cells, as evidenced by the increased intracellular lipid accumulation and elevated expressions of adipogenic biomarkers, including peroxisome proliferator-activated receptor γ (PPARγ), Perilipin, Adiponectin, and fatty acid binding protein 4 (FABP4). Surprisingly, the thermogenic capacity of the differentiated cells was compromised as a result of 3-BHA exposure, because neither intracellular mitochondrial contents nor expressions of thermogenic biomarkers, including uncoupling protein 1 (UCP1), peroxisome proliferator-activated receptor γ coactivator 1α (PGC1α), cell-death-inducing DNA fragmentation factor α subunit-like effector A (CIDEA), and PR domain containing 16 (PRDM16), were increased by this chemical. The underlying molecular mechanism exploration revealed that, in contrast to p38 MAPK, 3-BHA stimulation induced phosphorylation of Smad1/5/8 in an exposure time-dependent manner, suggesting that this chemical-triggered Smad signaling was responsible for the shift of C3H10T1/2 MSC differentiation from a brown to white-like phenotype. The finding herein, for the first time, revealed the perturbation of 3-BHA in the development of brown adipocytes, uncovering new knowledge about the obesogenic potential of this emerging chemical of concern.

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

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

Synthetic Phenolic Antioxidants and Their Metabolites in Follicular Fluid and Association with Diminished Ovarian Reserve: A Case-Control Study

BACKGROUND

Diminished/decreased ovarian reserve (DOR) is a disorder of ovarian function, which severely affects women's reproductive health. Accumulating evidence has found that adverse environmental factors can affect ovarian function. However, whether synthetic phenolic antioxidants (SPAs) exposure is associated with DOR is still unknown.

OBJECTIVES

We explored whether concentrations of SPAs and their metabolites are associated with DOR.

METHODS

A case-control study was conducted from January 2019 to January 2020 in China. One hundred eighty-one women 20-44 years of age, with (case group, n=63) and without DOR (control group, n=118) were included in our study. The follicular fluid concentrations of typical SPAs and their metabolites were measured, including butylated hydroxyanisole (BHA), tert-butylhydroquinone (TBHQ), butylated hydroxytoluene (BHT), and five BHT metabolites [3,5-di-tert-butyl-4-hydroxy-benzylalcohol (BHT-OH), 3,5-di-tert-butyl-4-hydroxybenzaldehyde (BHT-CHO), 3,5-di-tert-butyl-4-hydroxybenzoic acid (BHT-COOH), 2,6-di-tert-butyl-1,4-benzoquinone (BHT-Q), and 2,6-di-tert-butyl-4-hydroxy-4-methylcyclohexa-2,5-dien-1-one (BHT-quinol)]. Information about serum basal concentrations of follicle-stimulating hormone (FSH), luteinizing hormone (LH), estradiol (E2), and anti-Müllerian hormone (AMH) and the basal antral follicle count (AFC) was collected.

RESULTS

The measured frequencies of BHA, TBHQ, BHT, BHT-OH, BHT-CHO, BHT-COOH, BHT-Q, and BHT-quinol in follicular fluid were 1.7%, 2.2%, 40.3%, 46.4%, 57.5%, 100%, 64.6%, and 49.2%, respectively. The concentrations of BHT-CHO (0.49 ng/mL vs. 0.12 ng/mL, p=0.041), BHT-COOH (0.45 ng/mL vs. 0.28 ng/mL, p<0.001), BHT-Q (0.70 ng/mL vs. 0.13 ng/mL, p<0.001), and the sum of five BHT metabolites (Σ5metabolites; 1.79 ng/mL vs. 1.0 ng/mL, p<0.001) in the case group were significantly higher than those in the control group. The risk of DOR was further analyzed according to the tertiles of chemical concentration. Compared with the low levels of BHT metabolites, the adjusted odds ratios (ORs) for DOR were significantly increased in the high levels of BHT-CHO [OR=3.19, 95% confidence interval (CI): 1.22, 8.31, p=0.018], BHT-COOH [OR=4.73 (95% CI: 1.63, 13.71), p=0.004], and BHT-Q [OR=4.48 (95% CI: 1.69, 11.86), p=0.003] after adjusting for age, body mass index, education, infertility type, triglycerides, and total cholesterol. Moreover, compared with the low level of Σ5metabolites, increased adjusted ORs for DOR were found both in the middle level [OR=4.11 (95% CI: 1.44, 11.75), p=0.008] and high level [OR=5.51 (95% CI: 1.81, 16.77), p=0.003], showing an obvious dose-response relationship (pTrend=0.003).

CONCLUSION

In this study, we report the measured frequency and concentrations of BHA, TBHQ, BHT, and their metabolites in follicular fluid. Moreover, we found the concentrations of BHT metabolites, especially BHT-CHO, BHT-COOH, and BHT-Q, are positively associated with the increased risk of DOR. https://doi.org/10.1289/EHP11309.

3-tert-Butyl-4-hydroxyanisole perturbs renal lipid metabolism in vitro by targeting androgen receptor-regulated de novo lipogenesis

The widespread usage of 3-tert-butyl-4-hydroxyanisole (3-BHA) as an anthropogenic antioxidant has caused considerable environmental contamination and frequent detection in diverse human-derived samples. 3-BHA can promote adipogenesis and impair hepatic lipid metabolism, while its effects on renal lipid homeostasis remain to be uncertain. Herein, using the human kidney 2 (HK-2) cell experiments, 3-BHA was found to cause a significant reduction in lipid accumulation of the HK-2 cells in both exposure concentration- and duration-dependent manners. Exposure to 3-BHA lowered the transcriptional expressions of sterol regulatory element-binding protein 1 (SREBP1) and acetyl-CoA carboxylase (ACC), as well as ACC activity, indicating the inhibition in the process of de novo lipogenesis in HK-2 cells. On this basis, the mechanism study suggested that the reduced glucose absorption and accelerated glycolysis were concomitantly involved. The antagonism of 3-BHA on the transactivation of androgen receptor (AR) contributed to the lowered de novo lipogenesis and the consequent intracellular lipid reduction. The metabolomics data further confirmed the imbalance of lipid homeostasis and dysregulation of de novo lipogenesis. The new findings on the impaired renal lipid metabolism induced by 3-BHA warranted proper care about the usage of this chemical as a food additive.

Prevalence of Novel and Traditional Synthetic Phenolic Antioxidants in Baby Food from China: A Dominant Pathway for Infant Exposure

Synthetic phenolic antioxidants (SPAs) are a group of ubiquitous contaminants with multiple toxicities. However, current knowledge on the occurrence of SPAs in baby food and associated infant exposure is lacking. Herein, we analyzed three categories of baby food from China: infant formula, cereal, and puree, for a broad suite of 11 traditional and 19 novel SPAs. In addition to 11 traditional SPAs, up to 13 novel SPAs were detected in the baby food samples. The median concentrations of novel SPAs for infant formula, cereal, and puree were 604, 218, and 24.1 ng/g, respectively, surpassing those of traditional SPAs (53.4, 62.1, and 10.0 ng/g). The prevalent SPAs in the samples were butylated hydroxytoluene, 2,4-di-tert-butylphenol, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (AO 1010), and octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate (AO 1076). Source analysis indicated that the prevalence of these four SPAs in baby food was associated with contamination of packaging materials, mechanical processing, or raw ingredients. Migration experiments demonstrated that contamination of plastic packaging constituted an important source. Exposure assessment suggested that there may be no appreciable health risk posed by the SPAs in baby food. Even so, baby food consumption was still a dominant pathway for infant exposure to SPAs, with a higher contribution than breast milk consumption, dust ingestion, dermal dust absorption, and air inhalation, which requires special attention.

Organophosphite Antioxidants and Novel Organophosphate Esters in Dust from China: Large-Scale Distribution and Heterogeneous Phototransformation

A large-scale survey was conducted by measuring five organophosphite antioxidants (OPAs) and three novel organophosphate esters (NOPEs) in 139 dust samples across China. The median summed concentrations of OPAs and NOPEs in outdoor dust were 33.8 ng/g (range: 0.12-53,400 ng/g) and 7990 ng/g (2390-27,600 ng/g), respectively. The dust concentrations of OPAs associated with the increasing economic development and population density from western to eastern China, whereas the NOPE concentration in Northeast China (median, 11,900 ng/g; range, 4360-16,400 ng/g) was the highest. Geographically, the distribution of NOPEs was significantly associated with annual sunshine duration and precipitation at each sampling site. Results of laboratory experiments further revealed that the simulated sunlight irradiation promoted the heterogeneous phototransformation of OPAs in dust, and this process was accelerated with the existence of reactive oxygen species and enhanced relative humidity. Importantly, during this phototransformation, the hydroxylated, hydrolyzed, dealkylated, and methylated products, e.g., bis(2,4-di-tert-butylphenyl) methyl phosphate, were identified by nontargeted analysis, part of which were estimated to be more toxic than their parent compounds. The heterogeneous phototransformation pathway of OPAs was suggested accordingly. For the first time, the large-scale distribution of OPAs and NOPEs and the phototransformation of these "new chemicals" in dust were revealed.

2,4-di-tert-butylphenol exposure impairs osteogenic differentiation

2,4-di-tert-butylphenol (2,4-DTBP) is a synthetic antioxidant used in polyethylene crosspolymer (PEX) water distribution pipes and food-related plastics. 2,4-DTBP can leach from plastic materials and has been found in breast milk, cord blood, and placental tissue, giving rise to the concern that this compound may interfere with fetal development. The objective of this study is to assess the impacts of 2,4-DTBP on cellular differentiation. Human induced pluripotent stem (HiPS) cells were differentiated into osteoblasts or myoblasts over 40 days, and analyzed for markers of somite, dermomyotome, sclerotome, myoblast, and osteoblast development. When cultured as stem cells, 2,4-DTBP did not alter cell viability and expression of markers (NANOG, OCT4). However, upon differentiation into somite-like cells, 2,4-DTBP had reduced levels of MEOX1 and TBX6 transcripts, while NANOG and OCT4 were in turn upregulated in a dose-dependent manner. At the sclerotome-like stage, PAX9 mRNA decreased by 2-fold in the 0.5 μM and 1.0 μM 2,4-DTBP exposure groups. After 40 days of differentiation into an osteoblast-like lineage, exposure to 2,4-DTBP significantly reduced expression of the osteogenesis transcripts RUNX2 and OSX in a dose-dependent manner. Further, Alizarin Red staining of calcium deposits was decreased in the 0.5 μM and 1.0 μM treatment groups. In contrast, myogenesis was not affected by 2,4-DTBP exposure. Interestingly, KEAP1 expression was significantly increased in the sclerotomal-like cells, but decreased in the dermomytomal-like cells, which may suggest a mechanism of action. Overall, this study shows that 2,4-DTBP can delay key processes during sclerotome and osteoblast development, leading to a potential for bone developmental issues in exposed individuals.

Exploring the interrelationship between the skin microbiome and skin volatiles: A pilot study

Unravelling the interplay between a human’s microbiome and physiology is a relevant task for understanding the principles underlying human health and disease. With regard to human chemical communication, it is of interest to elucidate the role of the microbiome in shaping or generating volatiles emitted from the human body. In this study, we characterized the microbiome and volatile organic compounds (VOCs) sampled from the neck and axilla of ten participants (five male, five female) on two sampling days, by applying different methodological approaches. Volatiles emitted from the respective skin site were collected for 20 min using textile sampling material and analyzed on two analytical columns with varying polarity of the stationary phase. Microbiome samples were analyzed by a culture approach coupled with MALDI-TOF-MS analysis and a 16S ribosomal RNA gene (16S RNA) sequencing approach. Statistical and advanced data analysis methods revealed that classification of body sites was possible by using VOC and microbiome data sets. Higher classification accuracy was achieved by combination of both data pools. Cutibacterium, Staphylococcus, Micrococcus, Streptococcus, Lawsonella, Anaerococcus, and Corynebacterium species were found to contribute to classification of the body sites by the microbiome. Alkanes, esters, ethers, ketones, aldehydes and cyclic structures were used by the classifier when VOC data were considered. The interdisciplinary methodological platform developed here will enable further investigations of skin microbiome and skin VOCs alterations in physiological and pathological conditions.

High levels of synthetic antioxidants and ultraviolet filters in children's car seats

Forty-seven compounds among synthetic phenolic and amino antioxidants and ultraviolet filters, three suites of widely used chemical additives, were measured in eighteen popular children's car seats (fabric, foam, and laminated composites of both layers) marketed in the United States in 2018. Significantly higher levels of target compounds were found in foam and composite samples than in fabric samples. Median total concentrations of phenolic antioxidants and their transformation products ranged from 8.11 μg/g in fabric to 213 μg/g in foam In general, isooctyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate (AO-1135) and 2,4-di-tert-butylphenol (24-DBP) were the most abundant among all target compounds with maximum levels of526 μg/g in composite and 13.7 μg/g, respectively. The total concentrations of amino antioxidants and their transformation products and of ultraviolet filters were at least one order of magnitude lower than those of phenolic antioxidants, with medians of 0.15-37.1 μg/g and 0.29-1.81 μg/g, respectively, in which the predominant congeners were 4-tert-butyl diphenylamine (BDPA), 4,4'-di-tert-butyl diphenylamine (DBDPA), 4-tert-octyl diphenylamine (ODPA), 2,4-dihydroxybenzophenone (BP-1), 2-hydroxy-4-methoxybenzophenone (BP-3), and 2-(2-benzotriazol-2-yl)-4-methylphenol (UV-P). Large variabilities in usage of these chemicals resulted in different compositional patterns among the car seats. These results suggest that these compounds are major polymeric additives in children's car seats as they are present at greater levels than previously measured groups of chemicals like brominated flame retardants and per- and polyfluoroalkyl substances. Given the documented toxic potentials of synthetic antioxidants and ultraviolet filters, their abundances in children products are a cause for concern.

Environmental concentrations of 2, 4-DTBP cause immunotoxicity in zebrafish (Danio rerio) and may elicit ecological risk to wildlife

Synthetic phenolic antioxidant 2,4-di-tert-butylphenol (2,4-DTBP) has gained growing concerns due to relatively high concentrations in aquatic ecosystems. There are, however, significant knowledge gaps regarding its potential toxicity to aquatic organisms. In this study, zebrafish (Danio rerio) larvae were exposed to 0.01, 0.1, or 1 μM 2,4-DTBP for 6 d. Transcriptomic analysis of larvae revealed that biological processes related to anti-inflammatory function of macrophage M2 lineage were inhibited by 0.01 μM 2,4-DTBP. Decreases of transcripts related to the IL1B-MYD88-NF-κB pathway (i.e., il1b, il1rl1, myd88, irak4, irak1, traf6, ikbkg, nfkbia, nfkb) and protein levels of NF-κB in larvae intestine confirmed anti-inflammatory effects of 2,4-DTBP. Subsequently, larvae exposed to 2,4-DTBP were challenged with E. coli and showed higher survival rate, suggesting sustained activation of inflammation via LPS can be attenuated by 2,4-DTBP. Moreover, histological examination revealed that intestine barrier was compromised and there was an imbalance of intestine macrophage homeostasis. Food intake was also reduced following exposure to 0.1 and 1 μM 2,4-DTBP. In addition, a risk assessment revealed that 2,4-DTBP in surface water pose low to high ecological risks to aquatic organisms. Taken together, exposure to environmentally relevant concentrations of 2,4-DTBP could negatively affect immune response in zebrafish and may elicit ecological risk in fish population.

Vertical Alignment of Liquid Crystal on Sustainable 2,4-Di-tert-butylphenoxymethyl-Substituted Polystyrene Films

We synthesized sustainable 2,4-di-tert-butylphenoxymethyl-substituted polystyrenes (PDtBP#, # = 88, 68, 35, and 19, where # is molar percent contents of 2,4-di-tert-butylphenoxymethyl moiety), using post-polymerization modification reactions in order to study their liquid crystal (LC) alignment behaviors. In general, LC cells fabricated using polymer film with higher molar content of 2,4-di-tert-butylphenoxymethyl side groups showed vertical LC alignment behavior. LC alignment behavior in LC cell was related to the surface energy of the polymer alignment layer. For example, when the total surface energy value of the polymer layer was smaller than about 29.4 mJ/m², vertical alignment behaviors were observed, generated by the nonpolar 2,4-di-tert-butylphenoxymethyl moiety with long and bulky carbon groups. Orientation stability was observed at 200 °C in the LC cells fabricated using PDtBP88 as the LC alignment layer. Therefore, as a natural compound modified polymer, PDtBP# can be used as a candidate LC alignment layer for environmentally friendly applications.

Release of phthalate esters from a local landfill in the Tibetan Plateau: Importance of soil particle-size specific association

High loads of phthalate esters (PAEs) in background regions can be directly attributed to the local sources, and their association with soil particles may determine the environment behaviors. However, little is known about the particle-size specific distributions of PAEs in soils from point source to the surroundings. In this study, 12 PAE congeners were measured in clay (< 2 μm), silt (2-63 μm) and sand fractions (63-250 μm) from surficial soils and soil profiles (0-200 cm) around the Lhasa landfill. The total concentrations of PAEs in bulk soils varied from 0.44 to 22.3 μg/g, with a dominance of bis(2-ethylhexyl) phthalate (DEHP). The clay-sorbed PAEs exhibited a decreasing trend with the increasing distance from landfill. This distribution pattern was well described by the Gaussian air pollution model, suggesting the airborne particles/gaseous transport of clay-sorbed PAEs. The Boltzmann equation explained the spatial variation of silt-sorbed PAEs, reflecting the atmospheric dispersion of silt-sorbed PAEs. In comparison, the sand-sorbed PAEs in surrounding soils showed downslope accumulation possibly due to the aeolian transport of sand particles. Half-life of the most abundant PAE congener DEHP was assumed based on the soil inventories from observed concentration and the Level III fugacity model simulations, and the results indicated significant longer half-life of DEHP in deeper soils (~24,000 h) than in surficial soils (5500 h). This study elucidates that the distribution and fate of soil PAEs would depend on their association with particles in the source area, and the relative stability of DEHP in deeper soils would further increase PAE inventory in soil compartment.

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.

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.

Organophosphite Antioxidants in Mulch Films Are Important Sources of Organophosphate Pollutants in Farmlands

Organophosphite antioxidants (OPAs) are important auxiliary antioxidants used in plastic polymers and can be oxidized to organophosphate esters (OPEs) during production and processing. In this work, the occurrence of OPAs and OPEs in farmlands with or without mulch film applications was investigated. Six OPAs and five OPEs were detected, with the median concentrations of 2.66 ng/g (∑₆OPAs) and 100 ng/g (∑₅OPEs) in the film-mulching soil and 1.16 ng/g (∑₆OPAs) and 47.9 ng/g (∑₅OPEs) in the nonfilm-mulching soil, respectively. The oxidative derivative of AO168 (tris (2,4-di-tert-butylphenyl) phosphite), a typical OPA, AO168═O (tris (2,4-di-tert-butylphenyl) phosphate) was frequently detected in farmlands at the concentrations of 0-731 ng/g, which is much higher than that of the commercial OPEs (0-12.1 ng/g). This suggests that the oxidation derivatives of OPAs (OPAs═O) might be important OPE contaminants in soils. Mulch films could be their important source. According to the simulation migration experiment, the emission risk ranges of AO168 and AO168═O from mulch films to soils in China were estimated to be 3.96-87.6 and 10.5-95.3 tons/year, respectively, which were much higher than those of OPEs from sewage sludge applications. Simulation experiments also demonstrated that oxidation was the major pathway for OPAs in soils. OPAs with small substituent groups could be potential sources for organophosphate diesters. For the first time, the serious pollution of OPAs and OPAs═O in soils has been reported, and mulch films have been identified as their potential source.

Overview of intentionally used food contact chemicals and their hazards

Food contact materials (FCMs) are used to make food contact articles (FCAs) that come into contact with food and beverages during, e.g., processing, storing, packaging, or consumption. FCMs/FCAs can cause chemical contamination of food when migration of their chemical constituents (known as food contact chemicals, FCCs) occurs. Some FCCs are known to be hazardous. However, the total extent of exposure to FCCs, as well as their health and environmental effects, remain unknown, because information on chemical structures, use patterns, migration potential, and health effects of FCCs is often absent or scattered across multiple sources. Therefore, we initiated a research project to systematically collect, analyze, and publicly share information on FCCs. As a first step, we compiled a database of intentionally added food contact chemicals (FCCdb), presented here. The FCCdb lists 12'285 substances that could possibly be used worldwide to make FCMs/FCAs, identified based on 67 FCC lists from publicly available sources, such as regulatory lists and industry inventories. We further explored FCCdb chemicals' hazards using several authoritative sources of hazard information, including (i) classifications for health and environmental hazards under the globally harmonized system for classification and labeling of chemicals (GHS), (ii) the identification of chemicals of concern due to endocrine disruption or persistence related hazards, and (iii) the inclusion on selected EU- or US-relevant regulatory lists of hazardous chemicals. This analysis prioritized 608 hazardous FCCs for further assessment and substitution in FCMs/FCAs. Evaluation based on non-authoritative, predictive hazard data (e.g., by in silico modeling or literature analysis) highlighted an additional 1411 FCCdb substances that could thus present similar levels of concern, but have not been officially classified so far. Lastly, for over a quarter of all FCCdb chemicals no hazard information could be found in the sources consulted, revealing a significant data gap and research need.

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.

Volatile scent chemicals in the urine of the red fox, Vulpes vulpes

The red fox is a highly adaptable mammal that has established itself world-wide in many different environments. Contributing to its success is a social structure based on chemical signalling between individuals. Urine scent marking behaviour has long been known in foxes, but there has not been a recent study of the chemical composition of fox urine. We have used solid-phase microextraction and gas chromatography-mass spectrometry to analyze the urinary volatiles in 15 free-ranging wild foxes (2 female) living in farmlands and bush in Victoria, Australia. Foxes here are routinely culled as feral pests, and the urine was collected by bladder puncture soon after death. Compounds were identified from their mass spectra and Kovats retention indices. There were 53 possible endogenous scent compounds, 10 plant-derived compounds and 5 anthropogenic xenobiotics. Among the plant chemicals were several aromatic apocarotenoids previously found in greater abundance in the fox tail gland. They reflect the dietary consumption of carotenoids, essential for optimal health. One third of all the endogenous volatiles were sulfur compounds, a highly odiferous group which included thiols, methylsulfides and polysulfides. Five of the sulfur compounds (3-isopentenyl thiol, 1- and 2-phenylethyl methyl sulfide, octanethiol and benzyl methyl sulfide) have only been found in foxes, and four others (isopentyl methyl sulfide, 3-isopentenyl methyl sulfide, and 1- and 2-phenylethane thiol) only in some canid, mink and skunk species. This indicates that they are not normal mammalian metabolites and have evolved to serve a specific role. This role is for defence in musteloids and most likely for chemical communication in canids. The total production of sulfur compounds varied greatly between foxes (median 1.2, range 0.4–32.3 μg ‘acetophenone equivalents’/mg creatinine) as did the relative abundance of different chemical types. The urinary scent chemistry may represent a highly evolved system of semiochemicals for communication between foxes.

Novel Organophosphate Esters in Airborne Particulate Matters: Occurrences, Precursors, and Selected Transformation Products

Organophosphate esters (OPEs) represent an important group of industrial additives with broad applications. However, their occurrences and fate in the atmospheric environment have not been sufficiently investigated. Our study focused on four novel OPEs, including tris(2,4-di-tert-butylphenyl) phosphate (AO168 = O), bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphate, triisodecyl phosphate, and trisnonylphenol phosphate, and characterized their organophosphite antioxidant (OPA) precursors and selected transformation products, in airborne fine particles from South China. House dust from South China was also studied for comparison. Among these four OPEs, exceedingly high concentrations were determined for AO168 = O (i.e., median: 25 500 ng/g in PM_2.5, 52 900 ng/g in PM_1.0, and 10 700 ng/g in indoor dust), reaching 1 order of magnitude greater than those of traditional OPEs. Their OPA precursors were not detectable in airborne particles but hypothesized as one of the sources for airborne OPEs. In addition, potential transformation products of AO168 = O, including bis(2,4-di-tert-butylphenyl) phosphate (B2,4DtBPP) and 2,4-di-tert-butylphenol (2,4DtBP), also exhibited broad distributions. The levels of 2,4DtBP even surpassed those of AO168 = O in particles. The links between OPAs, OPEs, and other transformation products indicate the complexity of OPE-related chemicals in atmospheric environments. These links should be taken into consideration for a better characterization of OPEs' environmental and health risks.

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.

Tris(2,4-di-tert-butylphenyl)phosphate: An Unexpected Abundant Toxic Pollutant Found in PM2.5

A novel pollutant, tris(2,4-di-tert-butylphenyl)phosphate (I168O), was identified in urban fine particulate matter (PM_2.5) samples in a nontargeted screening based on mass spectrometry for the first time. I168O was detected in all samples collected from two typical cities far away from each other in China. The concentrations of I168O reached up to 851 (median: 153) ng/m³, indicating that it was a widespread and abundant pollutant in the air. The antioxidant Irgafos 168 [I168, tris(2,4-di-tert-butylphenyl)phosphite] popularly added in plastics was the most suspected source for the detected I168O. Simulation studies indicated that heating, UV radiation, and water contact might significantly (p < 0.05) transform I168 to I168O. In particular, I168O might be magnificently evaporated into the air at high temperatures. The outdoor inhalation exposure of I168O may exert substantial health risks.

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.

Synthetic Phenolic Antioxidants in Personal Care Products in Toronto, Canada: Occurrence, Human Exposure, and Discharge via Greywater

Although synthetic phenolic antioxidants (SPAs) are widely used in various personal care products (PCPs), little is known about their levels, composition profiles, human exposure, or environmental emissions. In this study, the occurrence of SPAs was evaluated in 15 categories of 214 PCPs collected in Toronto, Canada. Nine SPAs were detected in the PCPs, of which only 2,6-di-tert-butyl-4-methylphenol (BHT, < method quantification limit (MQL)-827 900 ng/g, mean: 35 602 ng/g, median: 249 ng/g) was observed with a detection frequency of >50%. When the 214 PCPs were separated into products labeled as containing BHT and those labeled as not containing BHT, the BHT-labeled PCPs (mean: 369 253 ng//g, median: 382 560 ng/g) contained significantly higher concentrations of BHT than the BHT-unlabeled PCPs (mean: 4960 ng/g, median: 199 ng/g) did (p < 0.01). Five transformation products (TPs) of BHT were also detected in the PCPs at low concentrations (∑TPs: < MQL to 19 014 ng/g, mean: 730 ng/g, median: < MQL) and detection frequencies (12.6-37.4%). Preliminary calculations found that dermal absorption via PCP use may be an important exposure pathway for BHT (mean: 565 879 ng/day median: 2988 ng/day), although this is a negligible exposure pathway for other SPAs. In addition, the estimated discharges of BHT (mean: 7852 g/day, median: 88 g/day) via greywater after PCP use were calculated, which represents a nonignorable source of BHT loading into wastewater treatment plants in Toronto (contributing 10%). To our knowledge, this is the first evaluation of human exposure to and discharge of SPAs via PCP use.