Synthetic Phenolic Antioxidants and Transformation Products in Human Sera from United States Donors

Synthetic phenolic antioxidants (SPAs) make up a group of widely used anthropogenic additives, whose potential for toxicity has received more attention in recent years. Although SPAs can reach humans through many exposure pathways, few data on the concentrations of SPAs in humans are available. In this study, five SPAs were quantified, at significant concentrations, in 50 individual serum samples collected from donors in the United States. The measured total SPA concentrations [0.46–34.7 ng/mL, geometric mean (GM) of 7.77 ng/mL] were dominated by 2,6-di-<i>tert</i>-butyl-4-methylphenol (BHT) and 2,4-di-<i>tert</i>-butylphenol (DBP), which contributed 42 and 57% on average to the total concentrations, respectively. Four putative biotransformation products (TPs) of BHT [2,6-di-<i>tert</i>-butyl-4-(hydroxymethyl)­phenol (BHT-OH), 3,5-di-<i>tert</i>-butyl-4-hydroxybenzaldehyde (BHT-CHO), 2,6-di-<i>tert</i>-butyl-1,4-benzoquinone (BHT-Q), and 2,6-di-<i>tert</i>-butyl-4-hydroxy-4-methyl-2,5-cyclohexadienone (BHT-quinol)] were also detected, with total concentrations ranging from below the method quantification limits to 3.66 ng/mL (GM of 0.77 ng/mL). Five pooled serum samples, each containing sera from at least 1000 donors, were also included in this study. The concentrations of the SPAs (GM of 24.5 ng/mL) and TPs (GM of 10.4 ng/mL) were even higher in pooled sera than in individual samples, indicating the prevalent human burdens of SPAs in a large population. To the best of our knowledge, this is the first analysis of a wide range of SPAs and TPs in human sera

Occurrence of Synthetic Phenolic Antioxidants and Major Metabolites in Municipal Sewage Sludge in China

Synthetic phenolic antioxidants (SPAs) are one group of widely used additive chemicals, which have not yet had focused attention except for a few compounds such as 2,6-di-<i>tert</i>-butyl-4-methylphenol (BHT). In this study, the occurrence and composition profiles of 12 frequently used SPAs and three BHT metabolites were investigated in fifty-six sludge samples collected from individual wastewater treatment plants in China. Eleven SPAs were positively found in the sludge samples, in which, to our knowledge, eight SPA compounds were identified for the first time in the environment. BHT, 4-<i>tert</i>-octylphenol (4-<i>t</i>OP), and 2,4,6-tri-<i>tert</i>-bultylphenol (AO 246) were the most dominant SPAs in the sludge at mean concentrations of 4.14 μg/g, 374 ng/g, and 98.1 ng/g d.w. (dry weight). Meanwhile, three BHT metabolites, including 3,5-di-<i>tert</i>-butyl-4-hydroxybenzaldehyde (BHT-CHO), 2,6-di-<i>tert</i>-butyl-1,4-benzoquinone (BHT-Q), and 2,6-di-<i>tert</i>-butyl-4-hydroxy-4-methyl-2,5-cyclohexadienone (BHT-quinol), were also found in most of the samples (>98.2%) with mean concentrations of 141, 562, and 225 ng/g d.w., respectively. The activated sludge system (anaerobic, anoxic, and oxic tanks) of a wastewater treatment plant was further investigated for the removal efficiencies of the SPAs. High removal efficiencies (80.1–89.2%) were found for the six detected SPAs in the aqueous phase, while generation of large proportions of the three BHT metabolites was also observed

Identification of Novel Polyfluorinated Ether Sulfonates as PFOS Alternatives in Municipal Sewage Sludge in China

A 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFAES) with the trade name F-53B, is an alternative to perfluorooctanesulfonate (PFOS) in electroplating industry that is uniquely used in China. It was developed as a mist suppressant initially in the 1970s, but the environmental behaviors and potential adverse effects of the 6:2 Cl-PFAES have only recently been investigated. In this work, the occurrence and distribution of perfluoroalkyl sulfonate (PFSA), fluorotelomer sulfonate (FTSA), and PFAES analogues were investigated in municipal sewage sludge samples collected around China. Perfluorobutane, perfluorohexane, perfluorooctane, and perfluorodecanesulfonates, 6:2 and 8:2 FTSAs, and the emerging 6:2 Cl-PFAES were detected. Moreover, 8:2 and 10:2 Cl-PFAESs were identified for the first time as new polyfluorinated contaminants using high resolution mass spectrometry. These fluorinated analytes were further quantified with the aid of commercial and laboratory-purified standards. PFOS was the predominant contaminant with a geometric mean (GM) value of 3.19 ng/g dry weight (d.w.), which was subsequently followed by 6:2 Cl-PFAES and 8:2 Cl-PFAES (GM: 2.15 and 0.50 ng/g d.w., respectively). Both 6:2 and 8:2 Cl-PFAES were positively detected as the major components in the F-53B commercial product, and discrete 6:2 Cl-PFAES/8:2 Cl-PFAES ratios in the product and sludge samples might suggest 8:2 Cl-PFAES had enhanced sorption behavior in the sludge due to the increase in hydrophobicity

Distribution and Preliminary Exposure Assessment of Bisphenol AF (BPAF) in Various Environmental Matrices around a Manufacturing Plant in China

Increasing attention has been paid to bisphenol A and bisphenol (BP) analogues due to high production volumes, wide usage and potential adverse effects. Bisphenol AF (BPAF) is considered a new bisphenol analogue which is used as raw material in plastic industry, but little is known about its occurrence in the environment and the potential associated risk. In this work, BPAF levels and environmental distribution were reported in samples collected around a manufacturing plant and a preliminary exposure risk assessment to local residents was conducted. BPAF was detected in most of the samples, with levels in river ranging between 4 ng/L, sediments (0.520–2.00 × 10³ ng/g dry weight, dw), soils

Metabolites of 2,4,4′-Tribrominated Diphenyl Ether (BDE-28) in Pumpkin after <i>In Vivo</i> and <i>In Vitro</i> Exposure

There is currently limited knowledge on PBDE metabolism in plants although they could play an important role in the environmental transformation of these persistent organic pollutants. In this study, pumpkin (<i>Cucurbita maxima × C. moschata)</i> was chosen as the model to understand the fate of BDE-28 in plants. MeO-tri-BDEs, OH-tri-BDEs, and OH-tri-BDEs were found as metabolites in plant samples of both <i>in vivo</i> hydroponic and <i>in vitro</i> tissue culture exposure. Three MeO-tri-BDEs were further identified as para-substituted metabolites. MeO-BDEs and OH-BDEs, respectively, accounted for about 1.6% and 1.5% (recovery corrected) of initial amount of BDE-28 according to the semiquantitative results. Other PBDEs, especially less brominated PBDEs as impurities in the standard of BDE-28, were also detected. The impurities and evaporation of the standard must be considered when trace metabolites are studied in exposure experiments

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

Identification and Composition of Emerging Quaternary Ammonium Compounds in Municipal Sewage Sludge in China

Quaternary ammonium compounds (QACs) have raised considerable attention due to their wide commercial applications and recent discovery of unknown persistent analogues in aqueous environment. In this work, the occurrence and distribution of alkyltrimethylammonium (ATMAC), benzylakyldimethylethylammonium (BAC) and dialkyldimethylammonium (DADMAC) homologues were investigated in fifty-two municipal sewage sludge samples. ATMAC C10–18, BAC C8–18 and paired DADMAC C8:8-C18:18 as well as emerging homologues such as ATMAC-20, 22 and mixed DADMAC-16:18 and 14:16 were present. Furthermore, paired DADMAC-20:20 and mixed DADMAC-14:18, 18:20 were identified for the first time by nontarget qualitative strategies. A triple quadruple mass spectrometer quantification method was also initially verified with the aid of laboratory synthesized standards for the analysis of the mixed DADMACs with no certificated commercial standards currently available. The total concentrations of ATMACs, BACs and DADMACs were in the range of 0.38–293, 0.09–191 and 0.64–344 μg/g dry weight, respectively, and particularly, mixed DADMACs constituted 39 ± 7% of total DADMAC concentrations. The concentrations and profiles of individual homologues further suggested different QAC applications and fate in China. Significant correlations were also found among the concentrations of various QAC homologues as well as wastewater treatment plant (WWTP) characteristics (total organic carbon contents and daily treatment volumes)

Observation of Emerging Photoinitiator Additives in Household Environment and Sewage Sludge in China

Photoinitiators (PIs) are widely used additives in industrial polymerization process, the contamination of which through migration into foodstuffs has been subjected to increasing public scrutiny. Nevertheless, little attention has been paid to the PI residue levels and potential exposure pathways from other environmental compartments. In the present study, the occurrence of PI additives with discrete molecular structures, that is, nine benzophenones (BZPs), four thioxanthones (TXs), and eight amine co-initiators (ACIs), was investigated in commercial products, indoor dust and sewage sludge samples. Nine PI compounds were positively detected in ultraviolet curable resins with concentrations of ∑PIs (sum of the detected PIs) up to 2.51 × 10⁴ ng/g, and 20 PIs can be found in food contact materials with concentrations of ∑PIs varying from 65.9 to 6.93 × 10³ ng/g. The wide usage of PIs in commercial products led to the occurrence of 19 PIs in indoor dust, with concentrations of ∑PIs in the range of 245–5.68 × 10³ ng/g. Meanwhile, all 21 targeted PIs could be identified in the sewage sludge, with concentrations from 67.6 to 2.03 × 10³ ng/g. Distinct PI composition profiles were observed in different investigated compartments, and BZPs were the dominant homologues in all samples. Most of the target PIs were further identified as class III chemicals by toxic hazard estimation algorithm (Toxtree), which indicates the compounds might be of significant toxicity or have reactive functional groups

Chlorinated Polyfluoroalkyl Ether Sulfonic Acids in Marine Organisms from Bohai Sea, China: Occurrence, Temporal Variations, and Trophic Transfer Behavior

F-53B, the commercial product of chlorinated polyfluoroalkyl ether sulfonic acids (Cl-PFESAs), has been used in Chinese chrome plating industry for 30 years, and was recently identified in the environment, which caused great concerns. So far, limited investigations have been performed on their environmental occurrence, fate and impact. In this study, we demonstrated the wide occurrence of Cl-PFESAs and their trophic transfer behavior in marine organisms from Chinese Bohai Sea. 6:2 Cl-PFESA (<0.016–0.575 ng/g wet weight) was the dominant congener, and 8:2 Cl-PFESA (<0.022–0.040 ng/g) was occasionally detected. Compared to other perfluoroalkyl and polyfluoroalkyl substances (PFASs) of concern, the levels of Cl-PFESAs were relatively lower in marine organisms. Based on the comparative analysis of Cl-PFESA contamination in mollusk samples collected in 2010–2014, both the concentrations and detection frequencies of Cl-PFESAs tended to increase in this region. And this kind of chemicals were more vulnerable to be accumulated in marine organisms at relatively higher trophic levels. Similar to perfluorooctanesulfonate (PFOS) and the long chain perfluorinated carboxylates (PFCAs), 6:2 Cl-PFESA could be magnified along the food chain. Accordingly, the potential threat might be posed to the wildlife and human beings due to unintended exposure to Cl-PFESAs

Aerobic Soil Biotransformation of 6:2 Fluorotelomer Iodide

6:2 FTI [F­(CF₂)₆CH₂CH₂I] is a principal industrial raw material used to manufacture 6:2 FTOH [F­(CF₂)₆CH₂CH₂OH] and 6:2 FTOH-based products and could enter aerobic environments from possible industrial emissions where it is manufactured. This is the first study to assess 6:2 FTI aerobic soil biotransformation, quantify transformation products, and elucidate its biotransformation pathways. 6:2 FTI biotransformation led to 6:2 FTOH as a key intermediate, which was subsequently biotransformed to other significant transformation products, including PFPeA [F­(CF₂)₄COOH, 20 mol % at day 91], 5:3 acid [F­(CF₂)₅CH₂CH₂COOH, 16 mol %], PFHxA [F­(CF₂)₅COOH, 3.8 mol %], and 4:3 acid [F­(CF₂)₄CH₂CH₂COOH, 3.0 mol %]. 6:2 FTI biotransformation also led to a significant level of PFHpA [F­(CF₂)₆COOH, 16 mol % at day 91], perhaps via another putative intermediate, 6:2 FTUI [F­(CF₂)₆CHCHI], whose molecular identity and further biotransformation were not verified because of the lack of an authentic standard. Total recovery of the aforementioned per- and polyfluorocarboxylates accounted for 59 mol % of initially applied 6:2 FTI by day 91, in comparison to 56 mol % when soil was dosed with 6:2 FTOH, which did not lead to PFHpA. Thus, were 6:2 FTI to be released from its manufacture and undergo soil microbial biotransformation, it could form PFPeA, PFHpA, PFHxA, 5:3 acid, and 4:3 acid in the environment