Occurrence and Distribution of Antibacterial Quaternary Ammonium Compounds in Chinese Estuaries Revealed by Machine Learning-Assisted Mass Spectrometric Analysis.

Antimicrobial resistance (AMR) undermines the United Nations Sustainable Development Goals of good health and well-being. Antibiotics are known to exacerbate AMR, but nonantibiotic antimicrobials, such as quaternary ammonium compounds (QACs), are now emerging as another significant driver of AMR. However, assessing the AMR risks of QACs in complex environmental matrices remains challenging due to the ambiguity in their chemical structures and antibacterial activity. By machine learning prediction and high-resolution mass spectrometric analysis, a list of antibacterial QACs (n = 856) from industrial chemical inventories is compiled, and it leads to the identification of 50 structurally diverse antibacterial QACs in sediments, including traditional hydrocarbon-based compounds and new subclasses that bear additional functional groups, such as choline, ester, betaine, aryl ether, and pyridine. Urban wastewater, aquaculture, and hospital discharges are the main factors influencing QAC distribution patterns in estuarine sediments. Toxic unit calculations and metagenomic analysis revealed that these QACs can influence antibiotic resistance genes (particularly sulfonamide resistance genes) through cross- and coresistances. The potential to influence the AMR is related to their environmental persistence. These results suggest that controlling the source, preventing the co-use of QACs and sulfonamides, and prioritizing control of highly persistent molecules will lead to global stewardship and sustainable use of QACs.

Occurrence and Ecological Risk of Alkylamine Triazines in Chinese Estuarine Sediments: An Emerging Class of Persistent, Mobile, and Toxic Substances.

Identifying persistent, mobile, and toxic (PMT) substances from synthetic chemicals is critical for chemical management and ecological risk assessment. Inspired by the triazine analogues (e.g., atrazine and melamine) in the original European Union's list of PMT substances, the occurrence and compositions of alkylamine triazines (AATs) in the estuarine sediments of main rivers along the eastern coast of China were comprehensively explored by an integrated strategy of target, suspect, and nontarget screening analysis. A total of 44 AATs were identified, of which 23 were confirmed by comparison with authentic standards. Among the remaining tentatively identified analogues, 18 were emerging pollutants not previously reported in the environment. Tri- and di-AATs were the dominant analogues, and varied geographic distributions of AATs were apparent in the investigated regions. Toxic unit calculations indicated that there were acute and chronic risks to algae from AATs on a large geographical scale, with the antifouling biocide cybutryne as a key driver. The assessment of physicochemical properties further revealed that more than half of the AATs could be categorized as potential PMT and very persistent and very mobile substances at the screening level. These results highlight that AATs are a class of PMT substances posing high ecological impacts on the aquatic environment and therefore require more attention.

Molecular characterization of diverse quinone analogs for discrimination of aerosol-bound persistent pyrolytic and photolytic radicals.

Aerosol-bound organic radicals, including environmentally persistent free radicals (EPFRs), are key components that affect climate, air quality, and human health. While putative structures have been proposed, the molecular characteristics of EPFRs remain unknown. Here, we report a surrogate method to characterize EPFRs in real ambient samples using mass spectrometry. The method identifies chemically relevant oxygenated polycyclic aromatic hydrocarbons (OxPAH) that interconvert with oxygen-centered EPFR (OC-EPFR). We found OxPAH compounds most relevant to OC-EPFRs are structurally rich and diverse quinones, whose diversity is strongly associated with OC-EPFR levels. Both atmospheric oxidation and combustion contributed to OC-EPFR formation. Redundancy analysis and photochemical aging model show pyrolytic sources generated more oxidized OC-EPFRs than photolytic sources. Our study reveals the detailed molecular characteristics of OC-EPFRs and shows that oxidation states can be used to identify the origins of OC-EPFRs, offering a way to track the development and evolution of aerosol particles in the environment.

An Integrated Workflow Assisted by In Silico Predictions To Expand the List of Priority Polycyclic Aromatic Compounds.

The limited information in existing mass spectral libraries hinders an accurate understanding of the composition, behavior, and toxicity of organic pollutants. In this study, a total of 350 polycyclic aromatic compounds (PACs) in 9 categories were successfully identified in fine particulate matter by gas chromatography high resolution mass spectrometry. Using mass spectra and retention indexes predicted by in silico tools as complementary information, the scope of chemical identification was efficiently expanded by 27%. In addition, quantitative structure-activity relationship models provided toxicity data for over 70% of PACs, facilitating a comprehensive health risk assessment. On the basis of extensive identification, the cumulative noncarcinogenic risk of PACs warranted attention. Meanwhile, the carcinogenic risk of 53 individual analogues was noteworthy. These findings suggest that there is a pressing need for an updated list of priority PACs for routine monitoring and toxicological research since legacy polycyclic aromatic hydrocarbons (PAHs) contributed modestly to the overall abundance (18%) and carcinogenic risk (8%). A toxicological priority index approach was applied for relative chemical ranking considering the environmental occurrence, fate, toxicity, and analytical availability. A list of 39 priority analogues was compiled, which predominantly consisted of high-molecular-weight PAHs and alkyl derivatives. These priority PACs further enhanced source interpretation, and the highest carcinogenic risk was attributed to coal combustion.

Transport of environmental natural organic matter coated silver nanoparticle across cell membrane based on membrane etching treatment and inhibitors.

Environmental natural organic matters (NOMs) have great effects on the physicochemical properties of engineering nanoparticles, which may impact the transport of nanoparticles across plasma membrane and the cytotoxicity. Therefore, the kinetics, uptake pathway and mass of transporting into A549 cell membrane of silver nanoparticles (AgNPs) coated with citric acid (CA), tartaric acid (TA) and fulvic acid (FA) were investigated, respectively. CA, FA and TA enhanced the colloidal stability of AgNPs in culture medium and have greatly changed the surface plasmon resonance spectrum of AgNPs due to the absorption of CA, FA and TA on surface of AgNPs. Internalizing model showed that velocity of CA-, TA- and FA-nAg transporting into A549 cell were 5.82-, 1.69- and 0.29-fold higher than those of the control group, respectively. Intracellular mass of Ag was dependent on mass of AgNPs delivered to cell from suspension, which obeyed Logistic model and was affected by NOMs that CA- and TA-nAg showed a large promotion on intracellular mass of Ag. The lipid raft/caveolae-mediated endocytosis (LME) of A549 cell uptake of AgNPs were susceptible to CA, TA and FA that uptake of CA-, TA- and FA-nAg showed lower degree of dependent on LME than that of the control (uncoated AgNPs). Actin-involved uptake pathway and macropinocytosis would have less contribution to uptake of FA-nAg. Overall, transmembrane transport of NOMs-coated AgNPs differs greatly from that of the pristine AgNPs.

In vitro inhalation bioaccessibility procedures for lead in PM2.5 size fraction of soil assessed and optimized by in vivo-in vitro correlation.

In order to assess and optimize frequently used in vitro inhalation bioaccessibility procedures for heavy metals in the inhalation risk assessment, in vivo inhalation bioavailability of Pb in simulated atmosphere fine particles (PM2.5) from aging soils spiked with lead compounds and field soils in lead-zinc mining areas was investigated via intranasally instilled experiments with these PM2.5 suspensions to mice and Pb bioaccessibility was extracted by using four frequently used in vitro procedures (Gamble Solution, simulated lung fluid, simulated epithelial lung fluid and artificial lysosomal fluid). Mouse exposure experiments showed that Pb was mainly distributed in the liver, kidneys, blood and spleen. Based on the kidney model, in vitro inhalation bioaccessibility of Pb extracted with optimized Gamble Solution, in which solid to liquid ratio (S/L) was optimized to 1:1000 g ml-1 and DTPA was proved to be the key effective component, showed a strong linear relationship with its in vivo inhalation bioavailability (y = 1.07x - 3.86, R2 = 0.73). Moreover, in vitro bioaccessible and bioavailable fractions of Pb were mainly from acid exchangeable and reducible fractions of Pb in PM2.5. Altogether, optimized Gamble Solution was suggested for the analysis of in vitro bioaccessibility for risk-based assessments.

Aggregation and dissolution of engineering nano Ag and ZnO pretreated with natural organic matters in the simulated lung biological fluids.

The increasing application of engineered nanoparticles such as silver nanoparticles (nAg) and zinc oxide nanoparticles (nZnO), results in their accumulation in environmental media. The environmental natural organic matter (NOM) adsorbed by these nanoparticles may have great effects on the aggregation and dissolution of metall ions, which are interesting and important for the assessment of the inhalation risks of these airborne suspended NOM-coated nanoparticles to humans. Therefore, the aggregation and dissolution of nAg and nZnO pretreated with citric acid (CA), tartaric acid (TA) and fulvic acid (FA) in simulated lung biological fluids (artificial lysosomal fluid (ALF) and Gamble Solution) were investigated. The surface properties, morphology and size of the NOM-treated ENPs changed, but the crystalline phase was relatively stable when observed using surface-enhanced Raman scattering, transmission electron microscope, and X-ray diffraction. NOM treatment had no significant influence on the particle size of NOM-treated nAg and nZnO except for a decrease in the size of CA-treated nAg, and it could not promote the aggregation of NOM-treated nAg and nZnO except for the aggregation of TA-treated nAg in Gamble Solution or TA-treated nZnO in ALF. CA- and FA-treatments promoted the release of Zn2+ and Ag+, respectively, while no promotion was observed after TA-treatment. Therefore, NOM affects the release of Zn2+ and Ag+ from NOM-treated nAg and nZnO but does not promote the aggregation of NOM-treated nAg and nZnO, which influences the inhalation risk-based assessment.