Identification of Fluorescent Brighteners as Another Emerging Class of Abundant, Ubiquitous Pollutants in the Indoor Environment

β-Cyclodextrin/calix[4]arene hybrid porous organic polymer membrane for synergistic extraction of fluorescent whitening agents migrating from food contact materials

Acurate and sensitive determination of hazards from food contact materials is important to monitor food safety. It is necessary to excavate efficient adsorbent for simultaneous recognition and adsorption of food hazards of trace level for sample preparation. In this work, β-cyclodextrin and calix[4]arene were employed as hybrid functional monomers to prepare macrocyclic porous organic polymer (β-CD-CX4 POP). It was proved that the supramolecular cavities of β-CD-CX4 POP could form inclusion complexes with fluorescent whitening agents (FWAs) through host-guest recognition, which greatly improved the adsorption performance. The hydrophobic cavities of β-cyclodextrin and calix[4]arene of β-CD-CX4 POP exhibited synergistic effect for simultaneous recognition of FWAs. The high-throughput enrichment of FWAs was realized by β-CD-CX4 POP membranes coupled with a multiple-channel syringe pump. Based on membrane-based solid-phase extraction combined with UHPLC-MS/MS, a sensitive analytical method was established to determine six FWAs. The LODs was in range of 3-50 ng/L with the linear range of 0.02-100 μg/L. The developed method was used to quantify FWAs in bread wrapper and bread, and the spiked recoveries ranged from 78.1%-119% with RSD of 2.3%-9.7%. This work indicated that β-CD-CX4 POP was promising for the simultaneous recognition and adsorption of FWAs migrating from food contact materials.

Occurrence, migration and health risks of fluorescent whitening agents and phthalates in bottled water

The occurrence and health risks of fluorescent whitening agents (FWAs) in bottled water were reported for the first time. FWA184 and FWA393 were the most frequently detected FWAs, with mean concentrations of 3.99-17.00 ng L-1. Phthalates (PAEs) such as dibutyl phthalate (DBP), di-iso-butyl phthalate (DiBP), and diethylhexyl phthalate (DEHP) were prevalent in bottled water, with mean levels of 40.89-716.66 ng L-1, and their concentrations in bottled water were much higher than those of FWAs. FWAs and PAEs in bottles and caps were extracted using organic solvent, and the correlation analysis showed that FWA393 and DEHP most likely originated from bottles, while bottle caps were the main sources of DBP and DiBP. The calculated risk quotients (RQs) of target substances and all age groups were considerably lower than the threshold of 0.1, indicating that consuming bottled water containing these plastic additives was unlikely to pose health risks for people of all ages. However, RQ values for underage people were several times higher than those for adults and hence cannot be neglected; therefore, special attention should be paid to understand the potential risks posed by the exposure to these plastic additives during early life stages, especially the infant stage.

Identification of Hydrocarbon Sulfonates as Previously Overlooked Transthyretin Ligands in the Environment

Incidences of thyroid disease, which has long been hypothesized to be partially caused by exposure to thyroid hormone disrupting chemicals (TDCs), have rapidly increased in recent years. However, known TDCs can only explain a small portion (∼1%) of in vitro human transthyretin (hTTR) binding activities in environmental samples, indicating the existence of unknown hTTR ligands. In this study, we aimed to identify the major environmental hTTR ligands by employing protein Affinity Purification with Nontargeted Analysis (APNA). hTTR binding activities were detected in all 11 indoor dust and 9 out of 10 sewage sludge samples by the FITC-T4 displacement assay. By using APNA, 31 putative hTTR ligands were detected including perfluorooctanesulfonate (PFOS). Two of the most abundant ligands were identified as hydrocarbon surfactants (e.g., dodecyl benzenesulfonate). Moreover, another abundant ligand was surprisingly identified as a disulfonate fluorescent brightener, 4,4'-bis(2-sulfostyryl)biphenyl sodium (CBS). CBS was validated as a nM-affinity hTTR ligand with an IC50 of 345 nM. In total, hydrocarbon surfactants and fluorescent brighteners explain 1.92-17.0 and 5.74-54.3% of hTTR binding activities in dust and sludge samples, respectively, whereas PFOS only contributed <0.0001%. Our study revealed for the first time that hydrocarbon sulfonates are previously overlooked hTTR ligands in the environment.

Toxicity of Three Optical Brighteners: Potential Pharmacological Targets and Effects on Caenorhabditis elegans

Optical brighteners (OBs) have become an integral part of our daily lives and culture, with a growing number of applications in various fields. Most industrially produced OBs are derived from stilbene, which has been found in environmental matrices. The main objectives for this work are as follows: first, to identify protein targets for DAST, FB-28, and FB-71, and second, to assess their effects in some behaviors physiologic of Caenorhabditis elegans. To achieve the first objective, each OB was tested against a total of 844 human proteins through molecular docking using AutoDock Vina, and affinities were employed as the main criteria to identify potential target proteins for the OB. Molecular dynamics simulations took and validated the best 25 docking results from two protein databases. The highest affinity was obtained for the Hsp70-1/DAST, CD40 ligand/FB-71, and CD40 ligand/FB-28 complexes. The possible toxic effects that OBs could cause were evaluated using the nematode C. elegans. The lethality, body length, locomotion, and reproduction were investigated in larval stage L1 or L4 of the wild-type strain N2. In addition, transgenic green fluorescent protein (GFP) strains were employed to estimate changes in relative gene expression. The effects on the inhibition of growth, locomotion, and reproduction of C. elegans nematodes exposed to DAST, FB-71, and FB-28 OBs were more noticeable with respect to lethality. Moreover, an interesting aspect in OB was increased the expression of gpx-4 and sod-4 genes associated with oxidative stress indicating a toxic response related to the generation of reactive oxygen species (ROS). In all cases, a clear concentration-response relationship was observed. It is of special attention that the use of OBs is increasing, and their different sources, such as detergents, textiles, plastics, and paper products, must also be investigated to characterize the primary emissions of OBs to the environment and to develop an adequate regulatory framework.

Impact of progressively cumulative exposure of AgNPs on earthworms (Eisenia fetida) and implication for eco-toxicological risk assessment

Hazardous pollutants released into the real environment mostly own long-lasting cumulative characteristics and have progressively negative impacts on organisms, which are always neglected in laboratory toxicological tests. Here in this study, the different ecotoxicity of Ag nanoparticles (AgNPs) on earthworm Eisenia fetida was compared via various endpoints and transcriptional sequencing between the 28-day progressively repeated (from 60 to 80, final 100 mg/kg) and one-step (directly to 100 mg/kg) exposure. The results showed that earthworms under progressively repeated exposure showed significantly less biomass loss and reproductive inhibition, as well as lower Ag bioaccumulation (15.6 mg/kg) compared with one-step exposure (17.9 mg/kg). The increases in enzyme activities (superoxide enzyme and catalase) and gene expression (metallothionein) also implied higher antioxidant and genetic toxicity in one-step exposed earthworms compared with those from progressively repeated exposure. Furthermore, the transcriptomic analysis identified 582 and 854 differentially expressed genes in the treatments of one-step and repeated exposure respectively compared with the control group. The results of pathway annotation and classification suggested similar enrichments of damage induction but different in toxic stress responses, whereas earthworms from repeated exposure possessed more detoxification-related pathways like translation and multicellular organismal processes. This study innovatively took into account the impacts of processive exposure occurring in the real environment and elucidated distinctions of toxicity and adaptation caused by different exposure patterns, which provided the theoretical basis for real risk identification under the framework and guidance of traditional toxicology, also the implication for the improvement of eco-toxicological risk assessment.

Nationwide Occurrence and Unexpected Severe Pollution of Fluorescent Brighteners in the Sludge of China: An Emerging Anthropogenic Marker

Fluorescent brighteners (FBs) are a group of mass-produced dyestuff chemicals that have been extensively used for decades. However, knowledge of their occurrence in municipal wastewater treatment plants on a large geographical scale remains unknown. Herein, we implemented the first nationwide survey for wastewater-derived FBs in sludge across major cities in China. All 25 target FBs were detected in the nationwide sludge. Ionic FBs exhibited much higher concentrations than nonionic FBs. The total sludge concentrations of 25 FBs (∑₂₅FBs) ranged from 7300 to 1,520,000 ng/g, with a median of 35,300 ng/g. A clear geographical distribution of significantly higher concentrations of FBs was found in East and Central China than in West China (p < 0.05). The sludge concentrations of ∑₂₅FBs were correlated well with the gross domestic product (GDP) and population size at the provincial level in China (p < 0.05), demonstrating the significance of anthropogenic impacts on FB levels in urban sludge. The nationwide annual emission of total FBs into sludge in China is estimated to be 835 tons/year, of which 134 tons/year is directly released into sludge-applied soils. Our work highlights another new class of chemicals that significantly contribute to the chemical mixtures in urban sludge and thus require immediate attention.