Occurrence and Prioritization of Human Androgen Receptor Disruptors in Sewage Sludges Across China.

The global practice of reusing sewage sludge in agriculture and its landfill disposal reintroduces environmental contaminants, posing risks to human and ecological health. This study screened sewage sludge from 30 Chinese cities for androgen receptor (AR) disruptors, utilizing a disruptor list from the Toxicology in the 21st Century program (Tox21), and identified 25 agonists and 33 antagonists across diverse use categories. Predominantly, natural products 5α-dihydrotestosterone and thymidine emerged as agonists, whereas the industrial intermediate caprolactam was the principal antagonist. In-house bioassays for identified disruptors displayed good alignment with Tox21 potency data, validating employing Tox21 toxicity data for theoretical toxicity estimations. Potency calculations revealed 5α-dihydrotestosterone and two pharmaceuticals (17ß-trenbolone and testosterone isocaproate) as the most potent AR agonists and three dyes (rhodamine 6G, Victoria blue BO, and gentian violet) as antagonists. Theoretical effect contribution evaluations prioritized 5α-dihydrotestosterone and testosterone isocaproate as high-risk AR agonists and caprolactam, rhodamine 6G, and 8-hydroxyquinoline (as a biocide and a preservative) as key antagonists. Notably, 16 agonists and 20 antagonists were newly reported in the sludge, many exhibiting significant detection frequencies, concentrations, and/or toxicities, demanding future scrutiny. Our study presents an efficient strategy for estimating environmental sample toxicity and identifying key toxicants, thereby supporting the development of appropriate sludge management strategies.

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.

Occurrence, Fate, Human Exposure, and Toxicity of Commercial Photoinitiators.

Photoinitiators (PIs) are a family of anthropogenic chemicals used in polymerization systems that generate active substances to initiate polymerization reactions under certain radiations. Although polymerization is considered a green method, its wide application in various commercial products, such as UV-curable inks, paints, and varnishes, has led to ubiquitous environmental issues caused by PIs. In this study, we present an overview of the current knowledge on the environmental occurrence, human exposure, and toxicity of PIs and provide suggestions for future research based on numerous available studies. The residual concentrations of PIs in commercial products, such as food packaging materials, are at microgram per gram levels. The migration of PIs from food packaging materials to foodstuffs has been confirmed by more than 100 reports of food contamination caused by PIs. Furthermore, more than 20 PIs have been detected in water, sediment, sewage sludge, and indoor dust collected from Asia, the United States, and Europe. Human internal exposure was also confirmed by the detection of PIs in serum. In addition, PIs were present in human breast milk, indicating that breastfeeding is an exposure pathway for infants. Among the most available studies, benzophenone is the dominant congener detected in the environment and humans. Toxicity studies of PIs reveal multiple toxic end points, such as carcinogenicity and endocrine-disrupting effects. Future investigations should focus on synergistic/antagonistic toxicity effects caused by PIs coexposure and metabolism/transformation pathways of newly identified PIs. Furthermore, future research should aim to develop "greener" PIs with high efficiency, low migration, and low toxicity.

Anaerobic Microbial Dechlorination of 6:2 Chlorinated Polyfluorooctane Ether Sulfonate and the Underlying Mechanisms.

The microbial transformation potential of 6:2 chlorinated polyfluorooctane ether sulfonate (6:2 Cl-PFESA) was explored in anaerobic microbial systems. Microbial communities from anaerobic wastewater sludge, an anaerobic digester, and anaerobic dechlorinating cultures enriched from aquifer materials reductively dechlorinated 6:2 Cl-PFESA to 6:2 hydrogen-substituted polyfluorooctane ether sulfonate (6:2 H-PFESA), which was identified as the sole metabolite by non-target analysis. Rapid and complete reductive dechlorination of 6:2 Cl-PFESA was achieved by the anaerobic dechlorinating cultures. The microbial community of the anaerobic dechlorinating cultures was impacted by 6:2 Cl-PFESA exposure. Organohalide-respiring bacteria originally present in the anaerobic dechlorinating cultures, including Geobacter, Dehalobacter, and Dehalococcoides, decreased in relative abundance over time. As the relative abundance of organohalide-respiring bacteria decreased, the rates of 6:2 Cl-PFESA dechlorination decreased, suggesting that the most likely mechanism for reductive dechlorination of 6:2 Cl-PFESA was co-metabolism rather than organohalide respiration. Reductive defluorination of 6:2 Cl-PFESA was not observed. Furthermore, 6:2 H-PFESA exhibited 5.5 times lower sorption affinity to the suspended biosolids than 6:2 Cl-PFESA, with the prospect of increased mobility in the environment. These results show the susceptibility of 6:2 Cl-PFESA to microbially mediated reductive dechlorination and the likely persistence of the product, 6:2 H-PFESA, in anaerobic environments.

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 ß-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.

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.

Cadmium-binding proteins in human blood plasma.

Blood is the transmission medium for metal contaminants to and from bodily organs; as such, it can provide useful and reliable information about their bio-kinetics as they're distributed throughout the body. Metals can interact with endogenous proteins present in the blood, and these metal-protein complexes often dictate the fates of the introduced metals. The aim of this study was to investigate cadmium-binding protein characteristics in normal human plasma. Cadmium-binding plasma proteins in two different groups: normal human plasma (n = 29), and normal paired maternal and fetal umbilical cord plasmas (n = 3), were analyzed. In order to detect cadmium-binding plasma proteins present in low concentrations, blood plasma samples were first depleted of their two most abundant proteins - albumin and immunoglobulin G. Both the crude and depleted plasma samples were analyzed using column gel electrophoresis in conjunction with Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). One cadmium-binding protein was detected in 11 of 29 normal plasma samples and all three paired maternal and cord plasma samples. This protein was further identified as apolipoprotein A-I by high-resolution mass spectrometry. To the best of our knowledge, this is the first study to reveal cadmium-binding proteins in real human blood plasma, which is extremely critical to our understanding of cadmium transportation and accumulation in human blood.

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.

Identification of Photoinitiators, Including Novel Phosphine Oxides, and Their Transformation Products in Food Packaging Materials and Indoor Dust in Canada.

Although photopolymerization is generally considered a green technology, the contamination of foodstuffs by photoinitiators (PIs), an essential component of photopolymerization systems, has recently attracted notice. Despite this interest, little attention has been paid to PI contamination in the environment. To date, only one study, performed in China, has reported the occurrence of PIs in the environment. In the present study, the occurrence of 25 PI additives with discrete molecular structures was investigated in food packaging materials and indoor dust. The PIs studied here include benzophenones (BZPs), thioxanthones (TXs), amine co-initiators (ACIs), and novel phosphine oxides (POs). Twenty-four PIs were detected in food packaging materials. Total concentrations of PIs (∑PIs) ranged between 122 and 44 113 ng/g, with a geometric mean (GM) of 3375 ng/g. The photodegradation of PIs in food packaging materials was investigated for the first time, and the half-lives of PIs in these materials were found to range from 32 to 289 h. These 24 PIs were also detected in indoor dust samples (GM of ∑PIs = 1483 ng/g). The relative abundances of different PIs were found to vary between the packaging materials and the indoor dust, which is attributed in part to the different stabilities of different PIs under simulated sunlight. Using standards synthesized in our lab, four TX transformation products (GM: 34.8 ng/g) were also detected in indoor dust. The concentrations of the transformation products were higher than the concentrations of the parent chemicals in indoor dust. Thus, further studies exploring human exposure to TXs should include these transformation products to avoid underestimation. This is the first report of PIs and relevant transformation products in the indoor environment in North America.

Organophosphite Antioxidants in Indoor Dust Represent an Indirect Source of Organophosphate Esters.

Precise determination of organophosphate esters (OPEs) in the environment is crucial to estimating their potential toxicity effects on human health. Previous studies have mainly focused on OPEs from direct sources. This study explored a potential indirect source of OPEs: the oxidation of organophosphite antioxidants (OPAs). OPAs are frequently used to retard degradation in polymers through their oxidation to OPEs. In this work, five OPAs [tris(2-chloroethyl) phosphite, triphenyl phosphite, tris(2,4-di- tert-butylphenyl) phosphite, bis(2,4-di- tert-butylphenyl) pentaerythritol diphosphite, and trisnonylphenol phosphite] could be identified, with geometric mean (GM) concentrations from 2.46 to 70.4 ng/g, in indoor dust. Their oxidation products, triisodecyl phosphate (TiDeP), tris(2,4-di- tert-butylphenyl) phosphate (AO168═O), bis(2,4-di- tert-butylphenyl) pentaerythritol diphosphate (AO626═O2), and trisnonylphenol phosphate (TNPP), were found at significantly higher GM concentrations (30.5-3759 ng/g). Surprisingly, two novel oxidation products AO168═O (GM: 3759 ng/g) and TNPP (GM: 2185 ng/g) had higher concentrations than tris(2-chloroethyl) phosphate (GM: 1608 ng/g) and triphenyl phosphate (GM: 1827 ng/g), which are well-known OPEs. These four novel OPEs (TiDeP, TNPP, AO168═O, AO626═O2) contributed 54.1% to the total concentration of the eight OPEs. The present investigation demonstrates that oxidation of OPAs is an important indirect source of novel OPEs in indoor environments. This is the first detection of four OPAs and their newly identified OPE oxidation products in indoor dust.

Emerging aromatic secondary amine contaminants and related derivatives in various dust matrices in China.

Aromatic secondary amines (Ar-SAs), constituted of several analogues with varied substitutions in molecular structure, are among the most frequently used anthropogenic antioxidants. Despite the reported toxicity effects, little information is available on their environmental contamination, except for few particular congeners such as diphenylamine. In this study, the occurrence of two kinds of Ar-SAs, substituted diphenylamines (S-DPAs) and novel substituted p-phenylenediamines (S-PPDs), was investigated in dust samples collected from outdoor rubber playgrounds and residential houses. Seven S-DPAs (GM: 102 ng/g) and two S-PPDs (GM: 20.9 ng/g) were detected in indoor dust. Significantly higher concentrations of S-DPAs (GM: 422 ng/g) and S-PPDs (GM: 31.6 ng/g) were observed in playground dust (p < 0.05). Different dominant Ar-SA congeners were found for indoor dust (low molecular weight Ar-SAs) and playground dust (high molecular weight Ar-SAs), indicating varied sources of Ar-SAs for different dust matrices. Apart from these parent chemicals, three diphenylamine derivatives, including N-nitrosodiphenylamine, 2-nitrodiphenylamine, and 4-nitrodiphenylamine, were also confirmed in indoor dust (GM: 35.7 ng/g) and playground dust (GM: 7.88 ng/g). A preliminary estimated daily intake calculation via dust ingestion indicated no immediate health risk to Chinese population. To our knowledge, this is the first report on the occurrence of a wide range of Ar-SAs and related derivates in dust matrices.

First Detection of Photoinitiators and Metabolites in Human Sera from United States Donors.

Photoinitiators (PIs), including benzophenones (BZPs), thioxanthones (TXs), and amine co-initiators (ACIs), are commonly used in photopolymerization systems, and their contamination in foodstuffs and the environment is attracting attention. Although humans are likely exposed to PIs, no data on human burdens of these chemicals are available. In this study, 18 PIs were detected in 50 individual human serum samples with concentrations of ΣPIs (sum of the detected PIs) from 423 to 2870 pg/mL (geometric mean, GM: 836 pg/mL). ΣBZPs (231-1240 ng/g,; GM: 593 pg/mL) were the dominant components, while ΣTXs (21.0-1431 ng/g; GM: 145 pg/mL) and ΣACIs (11.3-976 ng/g; GM: 48.5 pg/mL) were much lower. Data analysis found significantly higher concentrations of most PIs in the male sera than in the female ( p < 0.05). ΣPIs (2921-4139 ng/g; GM: 3621 pg/mL) were also detected in five pooled serum samples, each from at least 1000 donors, indicating the prevalent human burdens of PIs in a large population. Human liver S9 biodegradations of representative PIs, 2-isopropylthioxanthone (2-ITX) and 2,4-diethylthioxanthone (DETX), were conducted. Hydroxylation, sulfoxide, and sulfone metabolites of DETX and 2-ITX were identified by high resolution mass spectrometry in human liver S9 incubation systems. With synthesized standards, the sulfoxide and sulfone metabolites were successfully detected in the human serum samples, which contributed substantially to total human burdens. The ubiquitous presence of PIs in human sera indicates significant human exposure to PIs, although photopolymerization reaction has been generally considered a green technology.

Unexpectedly High Concentrations of a Newly Identified Organophosphate Ester, Tris(2,4-di- tert-butylphenyl) Phosphate, in Indoor Dust from Canada.

Organophosphate esters (OPEs) represent a group of additives with significant levels of production and significant application to various household and industrial products. Given their potential adverse effects on human health, accurate analysis of novel OPEs in indoor dust is crucial. In this study, the novel tris(2,4-di- tert-butylphenyl) phosphate (AO168═O) and six well-known OPEs were investigated. The seven target OPEs were detected in 100% of the office and home dust samples, with ∑OPEs (sum of the OPE concentrations) ranging from 2.92 to 124 µg/g [geometric mean (GM) of 12.3 µg/g]. Surprisingly, the novel AO168═O (0.10-11.1 µg/g, GM of 1.97 µg/g) was among the highest-concentration congeners, contributing 1.36-65.5% to ∑OPEs (mean of 20.7%). AO168═O was the dominant congener in the home dust samples, indicating it is an important OPE congener overlooked previously. AO168═O was also detected in Standard Reference Material 2585 (indoor dust) at an elevated concentration of 10.9 µg/g, which was significantly higher than the concentrations of the other target OPEs (0.38-2.17 µg/g). Despite the high concentrations measured in this study, no industrial production or application could be identified for AO168═O. The precursor of AO168═O, tris(2,4-di- tert-butylphenyl) phosphite, was detected in 50% of the dust samples, with a GM concentration of 1.48 ng/g. This study demonstrates that human OPE exposure in indoor environments is greater than was previously reported. This is the first report of the occurrence of AO168═O, its precursor, and its hydrolysis products in the environment.

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.

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 × 10(4) ng/g, and 20 PIs can be found in food contact materials with concentrations of ∑PIs varying from 65.9 to 6.93 × 10(3) 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 × 10(3) ng/g. Meanwhile, all 21 targeted PIs could be identified in the sewage sludge, with concentrations from 67.6 to 2.03 × 10(3) 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.

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.

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-tert-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-tert-octylphenol (4-tOP), and 2,4,6-tri-tert-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-tert-butyl-4-hydroxybenzaldehyde (BHT-CHO), 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 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 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).

Nail salon dust reveals alarmingly high photoinitiator levels: Assessing occupational risks.

Photoinitiators (PIs) are chemical additives that generate active substances, such as free radicals to initiate photopolymerization. Traditionally, polymerization has been considered a green technique that seldomly generates contaminants. However, many researches have confirmed toxicity effects of PIs, such as carcinogenicity, cytotoxicity, endocrine disrupting effects. Surprisingly, we found high levels of PIs in indoor dust. Our analysis revealed comparable levels of PIs in dust from printing shops (geometric mean, GM: 1.33 ×103 ng/g) and control environments (GM: 874 ng/g), underscoring the widespread presence of PIs across various settings. Alarmingly, in dust samples from nail salons, PIs were detected at total concentrations ranging from 610 to 1.04 × 107 ng/g (GM: 1.87 ×105 ng/g), significantly exceeding those in the control environments (GM: 1.43 ×103 ng/g). Nail salon workers' occupational exposure to PIs through dust ingestion was estimated at 4.86 ng/kg body weight/day. Additionally, an in vitro simulated digestion test suggested that between 10 % and 42 % of PIs present in ingested dust could become bioaccessible to humans. This is the first study to report on PIs in the specific environments of nail salons and printing shops. This study highlights the urgent need for public awareness regarding the potential health risks posed by PIs to occupational workers, marking an important step towards our understanding of environmental pollution caused by PIs.