Fate, risk and removal of triclocarban: A critical review

The fate of pharmaceuticals and personal care products (PPCPs) in sewer sediments:Adsorption triggering resistance gene proliferation

In recent years, large quantities of pharmaceuticals and personal care products (PPCPs) have been discharged into sewers, while the mechanisms of PPCPs enrichment in sewer sediments have rarely been revealed. In this study, three PPCPs (tetracycline, sulfamethoxazole, and triclocarban) were added consecutively over a 90-day experimental period to reveal the mechanisms of PPCPs enrichment and the transmission of resistance genes in sewer sediments. The results showed that tetracycline (TC) and triclocarban (TCC) have higher adsorption concentration in sediments compared to sulfamethoxazole (SMX). The absolute abundance of Tets and suls genes increased in sediments under PPCPs pressure. The increase in secretion of extracellular polymeric substances (EPS) and the loosening of the structure exposed a large number of hydrophobic functional groups, which promoted the adsorption of PPCPs. The absolute abundance of antibiotic resistance genes (ARGs), EPS and the content of PPCPs in sediments exhibited significant correlations. The enrichment of PPCPs in sediments was attributed to the accumulation of EPS, which led to the proliferation of ARGs. These findings contributed to further understanding of the fate of PPCPs in sewer sediments and opened a new perspective for consideration of controlling the proliferation of resistance genes.

Mitigation of Triclocarban Inhibition in Microbial Electrolysis Cell-Assisted Anaerobic Digestion

Triclocarban (TCC), as a widely used antimicrobial agent, is accumulated in waste activated sludge at a high level and inhibits the subsequent anaerobic digestion of sludge. This study, for the first time, investigated the effectiveness of microbial electrolysis cell-assisted anaerobic digestion (MEC-AD) in mitigating the inhibition of TCC to methane production. Experimental results showed that 20 mg/L TCC inhibited sludge disintegration, hydrolysis, acidogenesis, and methanogenesis processes and finally reduced methane production from traditional sludge anaerobic digestion by 19.1%. Molecular docking revealed the potential inactivation of binding of TCC to key enzymes in these processes. However, MEC-AD with 0.6 and 0.8 V external voltages achieved much higher methane production and controlled the TCC inhibition to less than 5.8%. TCC in the MEC-AD systems was adsorbed by humic substances and degraded to dichlorocarbanilide, leading to a certain detoxification effect. Methanogenic activities were increased in MEC-AD systems, accompanied by complete VFA consumption. Moreover, the applied voltage promoted cell apoptosis and sludge disintegration to release biodegradable organics. Metagenomic analysis revealed that the applied voltage increased the resistance of electrode biofilms to TCC by enriching functional microorganisms (syntrophic VFA-oxidizing and electroactive bacteria and hydrogenotrophic methanogens), acidification and methanogenesis pathways, multidrug efflux pumps, and SOS response.

A large-scale survey of urinary parabens and triclocarban in the Chinese population as well as the influencing factors and health risks

Parabens and triclocarban are widely applied as antimicrobial preservatives in foodstuffs, pharmaceuticals, cosmetics, and personal care products. However, few studies have been conducted on large-scale biomonitoring of parabens and triclocarban in the Chinese general population. In the present study, there were 1157 urine samples collected from 26 Chinese provincial capitals for parabens and triclocarban measurement to evaluate the exposure levels, spatial distribution, and influencing factors, as well as associated health risks in the Chinese population. The median concentrations of Σparabens and triclocarban were 14.0 and 0.03 μg/L, respectively. Methyl paraben was the predominant compound. Subjects in western China were more exposed to parabens, possibly due to climate differences resulting in higher consumption of personal care products. Subjects who were female, aged 18-44 years, or had a higher education level were found to have higher paraben concentrations. The frequency of drinking bottled water was positively associated with paraben exposure. The assessment of health risk based on urinary paraben concentrations indicated that 0.8 % of the subjects had a hazard index exceeding one unit, while Monte Carlo analysis suggested that 3.6 % of the Chinese population exposure to parabens had a potential non-carcinogenic risk. This large-scale biomonitoring study will help to understand the exposure levels of parabens and triclocarban in the Chinese general population and provide supporting information for government decision-making.

A study on the subchronic toxicity of triclocarban to the early-life development of oryzias melastigma and focused on the analysis of osmoregulatory regulation mechanisms

Triclocarban (TCC), a novel antimicrobial agent found in personal care products, has been extensively detected in marine environments. However, research on the toxic effects of TCC on marine organisms remains inadequate. This study delved into the subchronic toxic effects of TCC on the early life stages of marine medaka (Oryzias melastigma, O. melastigma), revealing that TCC could reduce embryo heart rate and hatching rate while diminishing the survival rate of larvae. Biomarker assays indicated that TCC could inflict damage on the embryos' antioxidant and nervous systems. Transcriptomic analysis suggested that TCC could impact cell growth, reproduction, and various life processes, activating cancer signaling pathways, increasing the likelihood of cancer, and exerting toxic effects on the immune and osmoregulatory systems. To validate and enhance our understanding of TCC's unique toxic impact on the osmoregulatory system of O. melastigma, we conducted homology modeling and molecular docking analyses on the protein involved in osmoregulation. The study intuitively revealed the potential binding affinity of TCC to sodium/potassium-transporting ATPase subunit alph (ATP1A1), indicating its ability to disrupt osmotic balance in marine fish by affecting this target protein. In summary, the results of this study will further enhance our comprehension of the potential toxic effects and mechanisms of TCC on the early stages of marine fish, with a specific focus on its unique toxic effects in osmoregulation.

Long-Term Triclocarban Exposure Induced Enterotoxicity by Triggering Intestinal AhR-Mediated Inflammation and Disrupting Microbial Community in Mice

Exposure to triclocarban (TCC), a commonly used antibacterial agent, has been shown to induce significant intestine injuries and colonic inflammation in mice. However, the detailed mechanisms by which TCC exposure triggered enterotoxicity remain largely unclear. Herein, intestinal toxicity effects of long-term and chronic TCC exposure were investigated using a combination of histopathological assessments, metagenomics, targeted metabolomics, and biological assays. Mechanically, TCC exposure caused induction of intestinal aryl hydrocarbon receptor (AhR) and its transcriptional target cytochrome P4501A1 (Cyp1a1) leading to dysfunction of the gut barrier and disruption of the gut microbial community. A large number of lipopolysaccharides (LPS) are released from the gut lumen into blood circulation owing to the markedly increased permeability and gut leakage. Consequently, toll-like receptor-4 (TLR4) and NF-κB signaling pathways were activated by high levels of LPS. Simultaneously, classic macrophage phenotypes were switched by TCC, shown with marked upregulation of macrophage M1 and downregulation of macrophage M2 that was accompanied by striking upregulation of proinflammatory factors such as Il-1β, Il-6, Il-17, and Tnf-α in the intestinal lamina propria. These findings provide new evidence for the TCC-induced enterotoxicity.

An informative short-term study on the impacts of a triclocarban/weathered multi-walled carbon nanotube-adsorbed complex to benthic organisms

Freshwater organisms are suitable models to study the fate of environmental pollutants. Due to their versatile and everyday use, many environmental pollutants such as triclocarban (TCC) or multi-walled carbon nanotubes (MWCNTs) enter environmental compartments very easily. TCC is known as a disinfectant and is declared as a highly aquatic toxicant. Multi-walled carbon nanotubes are used, e.g., in the automotive industry to improve plastic properties. Both TCCs and MWCNTs can pose major pollution hazards to various organisms. In addition, these substances can bind to each other due to their tendency to interact via strong hydrophobic interactions. Therefore, a short-term test was conducted to investigate the effects of the individual chemicals TCC and weathered MWCNTs (wMWCNTs) on a benthic biofilm and a grazing organism, Lymnaea stagnalis. Furthermore, the two compounds were coupled by an adsorption experiment resulting in a coupled complex formation (TCC + wMWCNTs). L. stagnalis showed no effects in terms of mortality. For benthic biofilm, the coupling test (TCC + wMWCNTs) showed a decrease of 58% in chlorophyll a (Chl-a) concentration. The main effect could be attributed to the wMWCNTs' exposure alone (decrease of 82%), but not to presence of TCC. The concentration range of Chl-a upon TCC exposure alone was comparable to that in the control group (32 and 37 µg/cm2). With respect to the particulate organic carbon (POC) concentration, very similar results were found for the solvent control, the TCC, and also for the TCC + wMWCNTs group (3, 2.9, and 2.9 mg/cm2). In contrast to the control, a significant increase in POC concentration (100%) was observed for wMWCNTs, but no synergistic effect of TCC + wMWCNTs was detected.

Biochar improved the solubility of triclocarban in aqueous environment: Insight into the role of biochar-derived dissolved organic carbon

Biochar as an effective adsorbent can be used for the removal of triclocarban from wastewater. Biochar-derived dissolved organic carbon (BC-DOC) is an important carbonaceous component of biochar, nonetheless, its role in the interaction between biochar and triclocarban remains little known. Hence, in this study, sixteen biochars derived from pine sawdust and corn straw with different physico-chemical properties were produced in nitrogen-flow and air-limited atmospheres at 300-750 °C, and investigated the effect of BC-DOC on the interaction between biochar and triclocarban. Biochar of 600∼750 °C with low polarity, high aromaticity, and high porosity presented an adsorption effect on triclocarban owing to less BC-DOC release as well as the strong π-π, hydrophobic, and pore filling interactions between biochar and triclocarban. In contrast and intriguingly, biochar of 300∼450 °C with low aromaticity and high polarity exhibited a significant solubilization effect rather than adsorption effect on triclocarban in aqueous solution. The maximum solubilization content of triclocarban in biochar-added solution reached approximately 3 times its solubility in biochar-free solution. This is mainly because the solubilization effect of BC-DOC surpassed the adsorption effect of biochar though the BC-DOC only accounted for 0.01-1.5 % of bulk biochar mass. Furthermore, the high solubilization content of triclocarban induced by biochar was dependent on the properties of BC-DOC as well as the increasing BC-DOC content. BC-DOC with higher aromaticity, larger molecular size, higher polarity, and more humic-like matters had a greater promoting effect on the water-solubility of triclocarban. This study highlights that biochar may promote the solubility of some organic pollutants (e.g., triclocarban) in aqueous environment and enhance their potential risk.

Mulberrin alleviates triclocarban induced hepatic apoptosis and inflammation by regulating the ROS/NF-κB pathway in grass carp

Triclocarban (TCC) is commonly used in household, personal care and industrial products and has been frequently detected in different aquatic ecosystems. Mulberrin (Mul) is a key component of the traditional Chinese medicine Romulus Mori with antioxidant and anti-inflammatory properties. The present study aimed to investigate the hepatotoxic effects of TCC in aquatic organisms and explore the protective roles of Mul. Herein, we found that exposure to TCC at environmentally realistic concentrations (5 μg/L) could impair liver function, along with impaired antioxidant defense and infiltration of inflammatory cells. Additionally, we found that TCC increased the ratio of TUNEL staining positive cells, accompanied by upregulation of pro-apoptotic protein (Bax, caspase3 and caspase9), and downregulation of anti-apoptotic proteins (Bcl2). In contrast, Mul supplementation reversed the hepatic pathological damage, ROS elevation, and apoptosis induced by TCC, likely due to hyperactivation of nuclear factor erythroid 2-related factor 2 (Nrf2) signaling. Additionally, Mul supplementation suppressed the mRNA levels of proinflammatory factors (TNF-α, IL-1β, IFN-γ, IL-6 and IL-8) and enhanced the mRNA levels of anti-inflammatory factors (TGFβ1, TGFβ2, IL4, IL10 and IL11) in the liver of carp. We also discovered that Mul supplementation suppressed TCC-induced nuclear nuclear factor κB (NF-κB) elevation. In conclusion, Mul enhances Nrf2 signaling cascades and counteracts the NF-κB inflammatory program to rescue hepatotoxicity induced by TCC, providing new insights into the hepatotoxic effects of TCC and potential protection strategies for heart injury induced by TCC.

Cetaceans as bio-indicators revealed the increased risks of triclosan exposure and associated thyroid hormone disruption during the COVID-19 pandemic

The global surge in disinfection practices from the COVID-19 response has raised concerns about the marine exposure to the hazardous ingredients in disinfectant products, including triclosan (TCS) and triclocarban (TCC). However, there are very limited studies on the response of marine TCS and TCC (TCs) loading to the COVID-19 pandemic. Here we used cetaceans as bio-indicators for a long-term retrospective analysis of TCs loading to the South China Sea (SCS) between 2004 and 2022. Hepatic TCs was 100% detected in all nine cetacean species (n = 120). Interestingly, TCS concentrations decreased in Indo-Pacific humpback dolphins (IPHD) before the pandemic from 2010 to 2017. However, after 2019, TCS concentrations in IPHD significantly increased several-fold. Similarly, post-pandemic TCS concentrations in Indo-Pacific finless porpoises (IPFP) and two fish species were significantly higher than pre-pandemic levels. There were significant relationships between thyroid hormones (THs) and TCs in IPHD and IPFP, suggesting that increased TCs may worsen the interference of THs homeostasis and nutritional conditions in cetaceans. These findings demonstrate the profound impact of the surging use of TCs-containing products from the COVID-19 response on marine ecosystems.

Profiling of the spatiotemporal distribution, risks, and prioritization of pharmaceuticals and personal care products in coastal waters of the northern Yellow Sea, China

Pharmaceuticals and personal care products (PPCPs) have aroused global concerns due to their ubiquitous occurrence and detrimental effects. The spatiotemporal distributions of 64 PPCPs and their synergetic ecological risks were comprehensively investigated in the seawater of Yantai Bay, and 1 H-benzotriazole (BT), ethenzamide, phenazone, propyphenazone, 4-hydroxybenzophenone and N, N'-diphenylurea were first determined in the seawater of China. Fifty-six PPCPs were detected and their concentrations were 27.5-182 ng/L, with BT contributing around 58.0%. Higher PPCP concentrations were observed in winter and spring, with the concentrations of antioxidants, analgesic/anti-inflammatory drugs and human-used antibiotics significantly higher in winter, while those of aquaculture-used antibiotics and UV filters significantly higher in summer, which was closely related with their usage patterns. Positive correlations were observed for PPCP concentrations between surface and bottom water, except summer, during which time the weak vertical exchange and varied environmental behaviors among different PPCPs resulted in the distinct compositions and concentrations. Terrestrial inputs and mariculture resulted in higher PPCP concentrations in the area located adjacent to the coast and aquaculture bases. The PPCP mixtures posed medium to high risk to crustaceans, and bisphenol A was identified as a high-risk pollutant that needs special attention.

Kinetics and mechanism of triclocarban degradation by the chlorination process: Theoretical calculation and experimental verification

Triclocarban (TCC) is an antimicrobial agent commonly used in many household and personal care products, and has been found persistent in the aquatic environment. Here we elucidate the kinetics and mechanism of TCC degradation during chlorination process by density functional theory (DFT) calculation and experimental verification. Results showed that hypochlorous acid (HOCl)/hypochlorite (OCl-) reacted with TCC via Cl-substitution, OH-substitution and C-N bond cleavage pathways. The reactivity of OCl- (2.80 × 10-7 M-1 s-1) with TCC was extremely low and HOCl (1.96 M-1 s-1) played the dominant role in TCC chlorination process. The N site of TCC was the most reactive site for chlorination. The second-order rate constants, which are determined using density functional theory (DFT) (kTCC-chlorineC, 1.96 M-1 s-1), can be separated into reaction rate constants related to the reactions of HOCl and OCl- with different isomers of TCC (TCC2 and TCC6). The obtained kTCC-chlorineC was consistent with the experimental determined second-order rate constant (kTCC-chlorineE, 3.70 M-1 s-1) in chlorination process. Eight transformation products (TP348, TP382, TP127, TP161, TP195, TP330, TP204, and TP296) were experimentally detected for chlorination of TCC, which could also be predicted by DFT calculation. Explicit water molecules participated in the chlorination reaction by transmitting the proton and connecting with TCC, HOCl/OCl- and other H2O molecules, and obviously reduced the energy barrier of chlorination.

Chemical prioritization of pharmaceuticals and personal care products in an urban tributary of the Potomac River

Pharmaceuticals and personal care products (PPCPs) are incredibly diverse in terms of chemical structures, physicochemical properties, and modes of action, making their environmental impacts challenging to assess. New chemical prioritization methodologies have emerged that compare contaminant monitoring concentrations to multiple toxicity data sources, including whole organism and high-throughput data, to develop a list of "high priority" chemicals requiring further study. We applied such an approach to assess PPCPs in Hunting Creek, an urban tributary of the Potomac River near Washington, DC, which has experienced extensive human population growth. We estimated potential risks of 99 PPCPs from surface water and sediment collected upstream and downstream of a major wastewater treatment plant (WWTP), nearby combined sewer overflows (CSO), and in the adjacent Potomac River. The greatest potential risks to the aquatic ecosystem occurred near WWTP and CSO outfalls, but risk levels rapidly dropped below thresholds of concern - established by previous chemical prioritization studies - in the Potomac mainstem. These results suggest that urban tributaries, rather than larger rivers, are important to monitor because their lower or intermittent flow may not adequately dilute contaminants of concern. Common psychotropics, such as fluoxetine and venlafaxine, presented the highest potential risks, with toxicity quotients often > 10 in surface water and > 1000 in sediment, indicating the need for further field studies. Several ubiquitous chemicals such as caffeine and carbamazepine also exceeded thresholds of concern throughout our study area and point to specific neurotoxic and endocrine modes of action that warrant further investigation. Since many "high priority" chemicals in our analysis have also triggered concerns in other areas around the world, better coordination is needed among environmental monitoring programs to improve global chemical prioritization efforts.

Triclocarban exposure aggravates dextran sulfate sodium-induced colitis by deteriorating the gut barrier function and microbial community in mice

Triclocarban (TCC) is an antibacterial component widely used in personal care products with potential toxicity possessing public health issues. Unfortunately, enterotoxicity mechanisms of TCC exposure remain largely unknown. Using a combination of 16S rRNA gene sequencing, metabolomics, histopathological and biological examinations, this study systematically explored the deteriorating effects of TCC exposure on a dextran sulfate sodium (DSS)-induced colitis mouse model. We found that TCC exposure at different doses significantly aggravated colitis phenotypes including shortened colon length and altered colonic histopathology. Mechanically, TCC exposure further disrupted intestinal barrier function, manifested by significant downregulation of the number of goblet cells, mucus layer thickness and expression of junction proteins (MUC-2, ZO-1, E-cadherin and Occludin). The gut microbiota composition and its metabolites such as short-chain fatty acids (SCFAs) and tryptophan metabolites were also markedly altered in DSS-induced colitis mice. Consequently, TCC exposure markedly exacerbated colonic inflammatory status of DSS-treated mice by activating NF-κB pathway. These findings provided new evidence that TCC could be an environmental hazards for development of IBD or even colon cancer.

Triclocarban-contaminated wastewater treatment by innovative hybrid moving entrapped bead activated sludge reactor (HyMER): Continuous performance and computational dynamic simulation analysis

Triclocarban (TCC) has been used in consumer products and is a widespread contaminant in municipal wastewater treatment systems that ultimately accumulates in natural receiving water and soil. This work aims to apply an innovative hybrid moving entrapped bead activated sludge reactor (named "HyMER") that integrates entrapped TCC-degrading microbes and freely suspended activated sludge to treat TCC-contaminated wastewater. A previously isolated TCC-degrading bacterium (Pseudomonas fluorescens strain MC46, called MC46) and barium alginate entrapment were applied. The synthetic TCC-contaminated wastewater treatment (with TCC concentration of 10 mg/L) was performed using 20-cycle fed-batch reactor operation with feeding times of 12 and 24 h and cycle times of 13 and 25 h. The results indicated that the HyMER effectively reduced chemical oxygen demand by up to 80 and 95 % and TCC by up to 53 and 83 %, respectively, with feeding times of 12 and 24 h. Three TCC degradation intermediate products were found-3,4-dichloroaniline, 4-chloroaniline, and aniline. Scanning electron microscopic analysis revealed shorter cells and bacterial appendage development as cell adaptations against TCC and its intermediates. The live/dead assay indicated high survival of entrapped MC46 in toxic conditions, with up to 84 % viable cells. Based on computational fluid dynamic analysis, no entrapped cell agglomeration showed in the reactor, indicating the potential application of HyMER for real wastewater treatment. These results exhibit the feasibility of HyMER and its applicability for future toxic wastewater treatment.

Complementary Biotransformation of Antimicrobial Triclocarban Obviously Mitigates Nitrous Oxide Emission toward Sustainable Microbial Denitrification

Sustainable nitrogen cycle is an essential biogeochemical process that ensures ecosystem safety and byproduct greenhouse gas nitrous oxide reduction. Antimicrobials are always co-occurring with anthropogenic reactive nitrogen sources. However, their impacts on the ecological safety of microbial nitrogen cycle remain poorly understood. Here, a denitrifying bacterial strain Paracoccus denitrificans PD1222 was exposed to a widespread broad-spectrum antimicrobial triclocarban (TCC) at environmental concentrations. The denitrification was hindered by TCC at 25 μg L^-1 and was completely inhibited once the TCC concentration exceeded 50 μg L^-1. Importantly, the accumulation of N₂O at 25 μg L^-1 of TCC was 813 times as much as the control group without TCC, which attributed to the significantly downregulated expression of nitrous oxide reductase and the genes related to electron transfer, iron, and sulfur metabolism under TCC stress. Interestingly, combining TCC-degrading denitrifying Ochrobactrum sp. TCC-2 with strain PD1222 promoted the denitrification process and mitigated N₂O emission by 2 orders of magnitude. We further consolidated the importance of complementary detoxification by introducing a TCC-hydrolyzing amidase gene tccA from strain TCC-2 into strain PD1222, which successfully protected strain PD1222 against the TCC stress. This study highlights an important link between TCC detoxification and sustainable denitrification and suggests a necessity to assess the ecological risks of antimicrobials in the context of climate change and ecosystem safety.

Immunotoxicity induced by triclocarban exposure in zebrafish triggering the risk of pancreatic cancer

Owing to frequent application as a broad-spectrum bactericide, triclocarban (TCC) exposure has raised great concern for aquatic organisms and human health. Herein, based on transcriptome sequencing data analysis of zebrafish, we confirmed that TCC induced oxidative stress and dysimmunity through transcriptional regulation of the related genes. With aid of the Cancer Genome Atlas (TCGA) assembler database, 52 common differentially expressed genes, whose functions were related to immunity, were screened out by virtue of the meta-analysis of pancreatic cancer sample data and differential transcription profiles from TCC-exposed larvae. Acute TCC exposure affected formation of the innate immune cells, delayed mature thymic T-cell development, reduced immunoglobulin M (IgM) levels and promoted excessive release of the pro-inflammatory factors (IL-6, IL-1β and tnfα). Under TCC exposure, the expressions of the genes associated with immune cell abundance in pancreatic cancer were significantly down-regulated, while the levels of ROS were prominently increased in concomitant with suppressed antioxidant activity. Moreover, a series of marker genes (pi3k, nrf2, keap1, ho-1 and nqo1) in the PI3K/Nrf2 antioxidant-stress pathway were abnormally expressed under TCC exposure. Interestingly, vitamin C decreased the malformation and increased the survival rate of 120-hpf larvae and effectively alleviated TCC-induced oxidative stress and immune responses. Overall, TCC exposure induced immunotoxicity and increased the risk of pancreatic cancer by inhibiting the antioxidant capacity of the PI3K/Nrf2 signal pathway. These observations enrich our in-depth understanding of the effects of TCC on early embryonic-larval development and immune damage in zebrafish.

Personal Care Products as a Contributing Factor to Antimicrobial Resistance: Current State and Novel Approach to Investigation

Antimicrobial resistance (AMR) is one of the world's industrialized nations' biggest issues. It has a significant influence on the ecosystem and negatively affects human health. The overuse of antibiotics in the healthcare and agri-food industries has historically been defined as a leading factor, although the use of antimicrobial-containing personal care products plays a significant role in the spread of AMR. Lotions, creams, shampoos, soaps, shower gels, toothpaste, fragrances, and other items are used for everyday grooming and hygiene. However, in addition to the primary ingredients, additives are included to help preserve the product by lowering its microbial load and provide disinfection properties. These same substances are released into the environment, escaping traditional wastewater treatment methods and remaining in ecosystems where they contact microbial communities and promote the spread of resistance. The study of antimicrobial compounds, which are often solely researched from a toxicological point of view, must be resumed considering the recent discoveries, to highlight their contribution to AMR. Parabens, triclocarban, and triclosan are among the most worrying chemicals. To investigate this issue, more effective models must be chosen. Among them, zebrafish is a crucial study system because it allows for the assessment of both the risks associated with exposure to these substances as well as environmental monitoring. Furthermore, artificial intelligence-based computer systems are useful in simplifying the handling of antibiotic resistance data and speeding up drug discovery processes.

The last 50 years of organic contamination of a highly anthropized tributary of the Po River (Italy)

We examined the temporal profiles of many organic micropollutants analysed in a sediment core sampled from a highly anthropized tributary of the Po River, the Lambro River. Analysed for extractable organic halogens (EOX), total petroleum hydrocarbons (C₁₀-C₄₀TPH), polycyclic aromatic hydrocarbons (PAHs), common legacy pollutants (DDTs, PCBs), halogenated flame retardants (PBDEs, DBDPE, TBBPA-bis, TCBPA, TBBPA, HBCDs), organotins (TBT, TPhT), antimicrobials (TCS, TCC), fragrances (AHTN, HHCB) and phthalates (DMP, DEP, DnBP, BBP, DEHP, DnOP), the dated sediment core revealed the historical record of 50 years of chemical contamination discharged into the Lambro and thereby the Po River. In this regard, the peak levels of PCBs and DDTs found in Lambro sediments were also identified in other sediment cores collected from the Po River prodelta in the Adriatic Sea, thus hundreds of kilometres downstream (Combi et al., 2020). The highest risk to aquatic organisms was associated with decades of high levels of C₁₀-C₄₀ TPH, PBDEs, PCBs, PAHs, DDTs, EOX, TCC, AHTN and DEHP, which in different periods of the contamination history, showed exceedances of guideline/threshold values. C₁₀-C₄₀ TPH and TCC, for example, were very high in the 1960s, whereas PCBs, DDTs, and PBDEs, peaked from the 1980s onward. The corresponding sums of PEC quotients ranged between 0.48 and 28.63, with a mean value (±SD) for the entire recording period of 10.62 ± 9.83. Environmental legislations and improved wastewater treatments were the main drivers of the recent downward trends observed for most of the chemicals investigated. Floods in turn resulted in macroscopic yet temporary improvements in the chemical quality of the tributary, conveying contaminated sediments into the Po River.

The Influence of the Chemical Composition of Natural Waters about the Triclocarban Sorption on Pristine and Irradiated MWCNTs

The influence of the chemical composition of natural waters on triclocarban (TCC) sorption on pristine and irradiated multi-walled carbon nanotubes (MWCNTs) at different temperatures was studied. Natural waters have been characterized in terms of the concentrations of cations and anions, pH, and electric conductivity. The sorption process of TCC on MWCNTs is influenced by both the chemical composition of natural waters and the variation of the temperature. The adsorption capacity of TCC on pristine and irradiated MWCNTs in the studied natural waters increased by increasing the temperature. The increase of the concentration of monovalent cations (Na+ and K+) in natural waters determined a significant decrease of the adsorption capacity of TCC on both pristine and irradiated MWCNTs while the increase of the bivalent cations (Ca2+ and Mg2+) determined an easy increase adsorption capacity. Freundlich and Langmuir models were selected to describe the steady adsorption of the TCC on the pristine and irradiated MWCNTs.

Enhanced bioremediation of triclocarban-contaminated soil by Rhodococcus rhodochrous BX2 and Pseudomonas sp. LY-1 immobilized on biochar and microbial community response

Triclocarban (TCC), an emerging organic contaminant (EOC), has become a severe threat to soil microbial communities and ecological security. Here, the TCC-degrading strain Rhodococcus rhodochrous BX2 and DCA-degrading strain Pseudomonas sp. LY-1 (together referred to as TC1) were immobilized on biochar to remove TCC and its intermediates in TCC-contaminated soil. High-throughput sequencing was used to investigate the microbial community structure in TCC-contaminated soil. Analysis of co-occurrence networks was used to explore the mutual relationships among soil microbiome members. The results showed that the immobilized TC1 significantly increased the removal efficiency of TCC from 84.7 to 92.7% compared to CK (no TC1 cells on biochar) in 10 mg/L TCC liquid medium. The utilization of immobilized TC1 also significantly accelerated the removal of TCC from contaminated soil. Microbial community analysis revealed the crucial microorganisms and their functional enzymes participating in TCC degradation in soil. Moreover, the internal labor division patterns and connections of TCC-degrading microbes, with a focus on strains BX2 and LY-1, were unraveled by co-occurrence networks analysis. This work provides a promising strategy to facilitate the bioremediation of TCC in soil, which has potential application value for sustainable biobased economies.

The effect of disinfectants and antiseptics on co- and cross-selection of resistance to antibiotics in aquatic environments and wastewater treatment plants

The outbreak of the SARS-CoV-2 pandemic led to increased use of disinfectants and antiseptics (DAs), resulting in higher concentrations of these compounds in wastewaters, wastewater treatment plant (WWTP) effluents and receiving water bodies. Their constant presence in water bodies may lead to development and acquisition of resistance against the DAs. In addition, they may also promote antibiotic resistance (AR) due to cross- and co-selection of AR among bacteria that are exposed to the DAs, which is a highly important issue with regards to human and environmental health. This review addresses this issue and provides an overview of DAs structure together with their modes of action against microorganisms. Relevant examples of the most effective treatment techniques to increase the DAs removal efficiency from wastewater are discussed. Moreover, insight on the resistance mechanisms to DAs and the mechanism of DAs enhancement of cross- and co-selection of ARs are presented. Furthermore, this review discusses the impact of DAs on resistance against antibiotics, the occurrence of DAs in aquatic systems, and DA removal mechanisms in WWTPs, which in principle serve as the final barrier before releasing these compounds into the receiving environment. By recognition of important research gaps, research needs to determine the impact of the majority of DAs in WWTPs and the consequences of their presence and spread of antibiotic resistance were identified.

Cosmetic Preservatives: Hazardous Micropollutants in Need of Greater Attention?

In recent years, personal care products (PCPs) have surfaced as a novel class of pollutants due to their release into wastewater treatment plants (WWTPs) and receiving environments by sewage effluent and biosolid-augmentation soil, which poses potential risks to non-target organisms. Among PCPs, there are preservatives that are added to cosmetics for protection against microbial spoilage. This paper presents a review of the occurrence in different environmental matrices, toxicological effects, and mechanisms of microbial degradation of four selected preservatives (triclocarban, chloroxylenol, methylisothiazolinone, and benzalkonium chloride). Due to the insufficient removal from WWTPs, cosmetic preservatives have been widely detected in aquatic environments and sewage sludge at concentrations mainly below tens of µg L^-1. These compounds are toxic to aquatic organisms, such as fish, algae, daphnids, and rotifers, as well as terrestrial organisms. A summary of the mechanisms of preservative biodegradation by micro-organisms and analysis of emerging intermediates is also provided. Formed metabolites are often characterized by lower toxicity compared to the parent compounds. Further studies are needed for an evaluation of environmental concentrations of preservatives in diverse matrices and toxicity to more species of aquatic and terrestrial organisms, and for an understanding of the mechanisms of microbial degradation. The research should focus on chloroxylenol and methylisothiazolinone because these compounds are the least understood.

Nicarbazin Residue in Tissues from Broilers Reared on Reused Litter Conditions

Nicarbazin (NCZ) is a worldwide used anticoccidial in poultry farming to avoid coccidiosis disease when chickens are reared on conventional poultry litter. If proper dosage and withdrawal time are not followed, the component dinitrocarbanilide (DNC) of NCZ may be present in chicken tissues, therefore posing a risk to consumers if the residues are above 200 µg/kg. Litter reuse is a common and important practice in commercial chicken production. Literature is lacking about the influence of litter reuse on DNC deposition in chicken tissues and its impact on food safety. We aimed to evaluate DNC residues in breast and liver by LC-MS/MS from broilers from an experiment with 10 consecutive flocks during 2 years. The experiment included three treatments containing NCZ in the diet (T1 = 125 mg/kg, 1−21 d; T2 = 125 mg/kg, 1−32 d; T3 = 40 mg/kg, 1−32 d). DNC residues in chicken breast at 21 d in T1 ranged from 648.8−926 µg/kg, at 32 d in T2 and T3 varied, respectively, from 232−667 µg/kg and 52−189 µg/kg. Regarding liver, DNC residues at 21 days in T1 ranged from 11,754−15,281 µg/kg, at 32 days in T2 and T3 varied, respectively, from 10,168−15,021 µg/kg and 2899−4573 µg/kg. When NCZ was withdrawn from feed, DNC residues dropped to <LOQ at 42 d in all treatments. Therefore, the reuse of poultry litter does not compromise food safety regarding DNC residues in chicken tissues, as shown herein up to 10 flocks.

Genetic bioaugmentation with triclocarban-catabolic plasmid effectively removes triclocarban from wastewater

Triclocarban, one of the emerging pollutants, has been accumulating, and it is frequently detected in wastewater. Due to its toxicity and persistence, the efficient removal of triclocarban from wastewater systems is challenging. Genetic bioaugmentation with transferable catabolic plasmids has been considered to be a long-lasting method to clean up pollutants in continuous flow wastewater treatment systems. In this study, bioaugmentation with Pseudomonas putida KT2440, harboring the transferrable triclocarban-catabolic plasmid pDCA-1-gfp-tccA2, rapidly converted 50 μM triclocarban in wastewater into 3,4-dichloroaniline and 4-chloroaniline, which are further mineralized more easily. RT-qPCR results showed that the ratio of the copy number of pDCA-1-gfp-tccA2 to the cell number of strain KT2440 gradually increased during genetic bioaugmentation, suggesting horizontal transfer and proliferation of the plasmid. By using DNA stable isotope probing (SIP) and amplicon sequencing, OTU86 (Escherichia-Shigella), OTU155 (Citrobacter), OTU5 (Brucella), and OTU15 (Enterobacteriaceae) were found to be the potential recipients of the plasmid pDCA-1-gfp-tccA2 in the wastewater bacterial community. Furthermore, three transconjugants in the genera of Escherichia, Citrobacter, and Brucella showing triclocarban-degrading abilities were isolated from the wastewater. This study develops a new method for removing triclocarban from wastewater and provides insights into the environmental behavior of transferrable catabolic plasmids in bacterial community in wastewater systems.

Fate, toxicity and effect of triclocarban on the microbial community in wastewater treatment systems

Triclocarban (TCC), one of the typical antimicrobial agents, is a contaminant of emerging concern commonly found in high concentration in water environments. However, the fate and toxicity of TCC in wastewater treatment systems remain poorly understood. Here, we investigated how TCC impacts chemical oxygen demand and inorganic nitrogen transformation in a hydrolytic anaerobic-anoxic/oxic process. In the anaerobic section, the transformation of TCC was dominated by reductive dechlorination and supplemented by two amid bonds hydrolysis. In the anoxic and oxic sections, the hydrolysis of amid bonds dominated. The toxicity was reduced after the treatment (IC₅₀ from 0.09 to 0.54). TCC inhibited NH₄⁺-N removal in the anaerobic section and led to the NO₃^--N accumulation (2.84-4.13 mg/L) after treatment, with the abundance of N-removal bacteria decreased by 6%. Furthermore, the original ecological niche was gradually replaced by TCC-resistant/degradative bacteria, formating new microbial modules to resist the TCC stress. Importantly, fourteen genera including Methanosaeta, Longilinea, Dokdonella and Mycobacterium as potential bioindicators warning TCC and its intermediates were proposed. Overall, this study provides new insights into the fate of TCC in biological wastewater treatment systems and suggests a great importance for TCC control to ensure the health and resilience of ecosystems.

Equilibrium Solubility of Triclocarban in (Cyclohexane + 1,4-Dioxane) Mixtures: Determination, Correlation, Thermodynamics and Preferential Solvation

Equilibrium solubility of triclocarban (TCC) expressed in mole fraction in 1,4-dioxane and cyclohexane, as well, as in 19 {cyclohexane (1) + 1,4-dioxane (2)} mixtures, was determined at seven temperatures from T = (288.15 to 318.15) K. Logarithmic TCC solubility in these cosolvent mixtures was adequately correlated with a lineal bivariate equation as function of both the mixtures composition and temperature. Apparent thermodynamic quantities for the dissolution and mixing processes were computed by means of the van’t Hoff and Gibbs equations observing endothermal and entropy-driven dissolution processes in all cases. The enthalpy–entropy compensation plot of apparent enthalpy vs. apparent Gibbs energy was linear exhibiting positive slope implying enthalpy-driving for TCC transfer from cyclohexane to 1,4-dioxane. Ultimately, by using the inverse Kirkwood–Buff integrals it is observed that TCC is preferentially solvated by cyclohexane molecules in 1,4-dioxane-rich mixtures but preferentially solvated by 1,4-dioxane molecules in cyclohexane-rich mixtures.

Degradation of Triclosan in the Water Environment by Microorganisms: A Review

Triclosan (TCS), a kind of pharmaceuticals and personal care products (PPCPs), is widely used and has had a large production over years. It is an emerging pollutant in the water environment that has attracted global attention due to its toxic effects on organisms and aquatic ecosystems, and its concentrations in the water environment are expected to increase since the COVID-19 pandemic outbreak. Some researchers found that microbial degradation of TCS is an environmentally sustainable technique that results in the mineralization of large amounts of organic pollutants without toxic by-products. In this review, we focus on the fate of TCS in the water environment, the diversity of TCS-degrading microorganisms, biodegradation pathways and molecular mechanisms, in order to provide a reference for the efficient degradation of TCS and other PPCPs by microorganisms.

Drug Chemical Space as a Guide for New Herbicide Development: A Cheminformatic Analysis

Herbicides are critical resources for meeting agricultural demand. While similar in structure and function to pharmaceuticals, the development of new herbicidal mechanisms of action and new scaffolds against known mechanisms of action has been much slower than in pharmaceutical sciences. We hypothesized that this may be due in part to a relative undersampling of possible herbicidal chemistries and set out to test whether this difference in sampling existed and whether increasing the diversity of possible herbicidal chemistries would be likely to result in more efficacious herbicides. To conduct this work, we first identified databases of commercially available herbicides and clinically approved pharmaceuticals. Using these databases, we created a two-dimensional embedding of the chemical, which provides a qualitative visualization of the degree to which each chemotype is distributed within the combined chemical space and shows a moderate degree of overlap between the two sets. Next, we trained several machine learning models to classify herbicides versus drugs based on physicochemical characteristics. The most accurate of these models has an accuracy of 93% with the key differentiating characteristics being the number of polar hydrogens, number of amide bonds, LogP, and polar surface area. We then used several types of scaffold decomposition to quantitatively evaluate the chemical diversity of each molecular family and showed herbicides to have considerably fewer unique structural fragments. Finally, we used molecular docking as an in silico evaluation of further structural diversification in herbicide development. To this end, we identified herbicides with well-characterized binding sites and modified those scaffolds based on similar structural subunits from the drug dataset not present in any commercial herbicide while using the machine-learned model to ensure that required herbicide properties were maintained. Redocking the original and modified scaffolds of several herbicides showed that even this simple design strategy is capable of yielding new molecules with higher predicted affinity for the target enzymes. Overall, we show that herbicides are distinct from drugs based on physicochemical properties but less diverse in their chemistry in a way not governed by these properties. We also demonstrate in silico that increasing the diversity of herbicide scaffolds has the potential to increase potency, potentially reducing the amount needed in agricultural practice.

Bioelectrochemical catabolism of triclocarban through the cascade acclimation of triclocarban-hydrolyzing and chloroanilines-oxidizing microbial communities

Chlorinated antimicrobial triclocarban (3,4,4'-trichlorocarbanilide, TCC) is an emerging refractory contaminant omnipresent in various environments. Preferential microbial hydrolysis of TCC to chloroanilines is essential for its efficient mineralization. However, the microbial mineralization of TCC in domestic wastewater is poorly understood. Here, the bioelectrochemical catabolism of TCC to chloroanilines (3,4-dichloroaniline and 4-chloroaniline) and then to CO₂ was realized through the cascade acclimation of TCC-hydrolyzing and chloroanilines-oxidizing microbial communities. The biodegradation of chloroanilines was obviously enhanced in the bioelectrochemical reactors. Pseudomonas, Diaphorobacter, and Sphingomonas were the enriched TCC or chloroanilines degraders in the bioelectrochemical reactors. The addition of TCC enhanced the synergistic effect within functional microbial communities based on the feature of the phylogenetic ecological networks. This study provides a new idea for the targeted domestication and construction of functionally differentiated microbial communities to efficiently remove TCC from domestic wastewater through a green and low-carbon bioelectrochemical method.

An amidase and a novel phenol hydroxylase catalyze the degradation of the antibacterial agent triclocarban by Rhodococcus rhodochrous

Triclocarban (TCC) is an emerging and intractable environmental contaminant due to its hydrophobicity and chemical stability. However, the antibacterial property of TCC limits its biodegradation, and only the functional enzyme TccA involved in TCC degradation has been characterized to date. In this study, we report a highly efficient TCC-degrading bacterium, Rhodococcus rhodochrous BX2, that could degrade and mineralize TCC (10 mg/L) by 76.8% and 56.5%, respectively, within 5 days. Subsequently, the TCC biodegradation pathway was predicted based on the detection of metabolites using modern mass spectrometry techniques. Furthermore, an amidase (TccS) and a novel phenol hydroxylase (PH_IND) encoded by the tccS and PH_IND genes, respectively, were identified by genomic and transcriptomic analyses of strain BX2, and these enzymes were further unequivocally proven to be the key enzymes responsible for the metabolism of TCC and its intermediate 4-chloroaniline (4-CA) by using a combination of heterologous expression and gene knockout. Our results shed new light on the mechanism of TCC biodegradation and better utilization of microbes to remediate TCC contamination.

Triclocarban shifted the microbial communities and promoted the spread of antibiotic resistance genes in nitrifying granular sludge system

Triclocarban (TCC) is in great market demand especially after the outbreak of COVID-19 pandemic, becoming an emerging pollutant. However, the impacts of TCC on the performance of nitrifying granular sludge system and the occurrence of antibiotic resistance genes (ARGs) were still unknown. This work explored the impacts of different concentrations of TCC on nitrifying granular sludge. Results showed that TCC suppressed the activities of ammonia-oxidizing microorganisms and decreased the abundance of Nitrospira. Adsorption was the main way for the removal of TCC and the biodegradation efficiency of TCC increased to 28.00% under 19.70 mg/L TCC addition. TCC enriched the ARGs and promoted the risks of their transferring in microorganisms. Pseudomonas might not only have strong resistance to TCC, but also propagate ARGs. The removal process of TCC and bacterial communities were important factors to promote the spread of ARGs. Thus, the existence of TCC presented a great environmental risk.

Ultrasound-assisted electrochemical treatment of cosmetic industry wastewater: Mechanistic and detoxification analysis

This study aims to investigate the mineralization of cosmetics producing industrial wastewater (CW) using sono-electrochemical (US-EC) treatments. The influence of operating parameters such as current density (j), electrolyte (Na₂SO₄) concentration (m), initial pH (pH_o), and ultrasonic power was investigated using Ti/RuO₂ dimensionally stable electrodes. The results demonstrated 80.9% chemical oxygen demand (COD) removal efficiency, 433.5 kWh (kg COD removed)^-1 of specific energy consumption at the optimum conditions of P = 100 W, j = 213 A m^-2, pH_o= 7.6 (natural pH), and m = 1.5 g L^-1. With the application of ultrasound, COD removal efficiency increases from 60.2% to 80.9%, with a synergistic effect of 1.1. Kinetics study analysis confirms that mineralization follows the n^th order kinetics model. In the presence of ultrasound, the performance of electrochemical treatment gets enhanced due to higher electron transfer, the enhanced production of ^•OH radicals, and sulfate radicals (SO₄^•-). The pathway for the degradation of the compound was suggested by quadrupole time of flight mass spectroscopy (QToF-MS). The operating cost of the process was also evaluated to establish the applicability of the US-EC process at the industrial scale.

Prenatal Exposure to Triclocarban Impairs ESR1 Signaling and Disrupts Epigenetic Status in Sex-Specific Ways as Well as Dysregulates the Expression of Neurogenesis- and Neurotransmitter-Related Genes in the Postnatal Mouse Brain

Triclocarban is a highly effective and broadly used antimicrobial agent. Humans are continually exposed to triclocarban, but the safety of prenatal exposure to triclocarban in the context of neurodevelopment remains unknown. In this study, we demonstrated for the first time that mice that had been prenatally exposed to environmentally relevant doses of triclocarban had impaired estrogen receptor 1 (ESR1) signaling in the brain. These mice displayed decreased mRNA and protein expression levels of ESR1 as well as hypermethylation of the Esr1 gene in the cerebral cortex. Prenatal exposure to triclocarban also diminished the mRNA expression of Esr2, Gper1, Ahr, Arnt, Cyp19a1, Cyp1a1, and Atg7, and the protein levels of CAR, ARNT, and MAP1LC3AB in female brains and decreased the protein levels of BCL2, ARNT, and MAP1LC3AB in male brains. In addition, exposure to triclocarban caused sex-specific alterations in the methylation levels of global DNA and estrogen receptor genes. Microarray and enrichment analyses showed that, in males, triclocarban dysregulated mainly neurogenesis-related genes, whereas, in females, the compound dysregulated mainly neurotransmitter-related genes. In conclusion, our data identified triclocarban as a neurodevelopmental risk factor that particularly targets ESR1, affects apoptosis and autophagy, and in sex-specific ways disrupts the epigenetic status of brain tissue and dysregulates the postnatal expression of neurogenesis- and neurotransmitter-related genes.

Toxic effects of triclocarban on larval zebrafish: A focus on visual dysfunction

Triclocarban (TCC) is considered an endocrine disruptor and shows antagonist activity on thyroid receptors. In view of the report that thyroid hormone signaling mediates retinal cone photoreceptor specification, we hypothesize that TCC could impair visual function, which is vital to wildlife. In order to verify our hypothesis, we assessed alteration in the retinal structure (retinal layer thickness and cell density), visually-mediated behavior, cone and rod opsin gene expression, and photoreceptor immunostaining in zebrafish larvae exposed to TCC at environmentally realistic concentrations (0.16 ± 0.005 µg/L, L-group) and one-fifth of the median lethal concentrations (25.4 ± 1.02 µg/L, H-group). Significant decrease in eye size, ganglion cell density, optokinetic response, and phototactic response can be observed in the L-group, while the thickness of outer nuclear layer, where the cell bodies of cone and rod cells are located, was significantly reduced with the down-regulation of critical opsin gene (opn1sw2, opn1mw1, opn1mw3, opn1lw1, opn1lw2, and rho) expression and rhodopsin immunofluorescence in the H-group. It should be noted that TCC could affect the sensitivity of zebrafish larvae to red and green light according to the results of behavioral and opsin gene expression analysis. These findings provide the first evidence to support our hypothesis that the visual system, a novel toxicological target, is affected by TCC. Consequently, we urgently call for a more in-depth exploration of TCC-induced ocular toxicity to aquatic organisms and even to humans.

Occurrence, effect, and fate of residual microplastics in anaerobic digestion of waste activated sludge: A state-of-the-art review

The plastic products have large consumption over last decades, resulting in a serious microplastics (MPs) pollution. Specially, the main removal way of MPs from wastewater is to transfer MPs from liquid to solid phase, leading to its enrichment in waste activated sludge (WAS). Anaerobic digestion has been served as the most potential technique to achieve both resource recovery and sludge reduction, herein this review provides current information on occurrence, effect, and fate of MPs in anaerobic digestion of WAS. The effects of MPs on WAS anaerobic digestion are greatly related to forms, particles sizes, contents, compositions and leachates of MPs. Also, the presence of MPs not only can change the effects of other pollutants on anaerobic digestion of WAS, but also can affect the fates of them. Besides, the future perspectives focused on the fate, effect and final removal of MPs during WAS anaerobic digestion process are outlined.

Benzothiazole-Containing Analogues of Triclocarban with Potent Antibacterial Activity

Triclocarban (TCC) is a polychlorinated, aromatic, antimicrobial agent commercially used since the 1950s in personal care products for the prevention of spoilage and infections. Humans are frequently exposed to TCC due to its widespread use, leading to its substantial release into the aquatic environment. With the recent ban of TCC from some personal care products, implemented in 2016, many replacement antimicrobial compounds have been studied by researchers. Herein, we report the synthesis and biological activity of a series of diarylureas, analogues of TCC that bear the benzothiazole nucleus as one of the two aryl moieties. Among the studied compounds, 2bF and 2eC showed the highest antimicrobial activity against Staphylococcus aureus, being also more active than TCC, with MIC values of 8 µg/mL versus 16 µg/mL of TCC. Moreover, compound 2bB was much more active than TCC against Enterococcus faecalis, a Gram-positive bacterium that is, unfortunately, strongly responsible for nosocomial infections. Finally, interesting results were found for compound 2bG that, even though less active than the others, exerts an interesting bactericidal action.

Fate and biodegradation characteristics of triclocarban in wastewater treatment plants and sewage sludge composting processes and risk assessment after entering the ecological environment

Triclocarban (TCC) has a high detection frequency in soil, rivers, sediments, and organisms, and its ecological risks have attracted substantial attention. In this study, we analyzed the fate of TCC in four wastewater treatment plants (WWTPs) in Zhengzhou, China, the biodegradation characteristics during the composting process, and the ecological risks of TCC when entering different environmental compartments. The concentration of TCC in the influent was 731.1-812.4 ng/L. More than 53.4% of TCC was biodegraded during the wastewater treatment process, and less than 2.5% was retained in the effluent. TCC was effectively removed through microbial degradation and sewage sludge absorption, and there were only minor differences in the different wastewater treatment processes. It is worth noting that more than 38% of TCC was enriched in sewage sludge (1430.1-1663.8 ng/g). The corresponding biodegradation rates of TCC were 65.7% and 82.8% in sewage sludge after 17 days of composting treatment with sawdust and straw as bulking agents, respectively. The estimated results showed that effluent discharge into the city rivers was safe. Composting could effectively degrade TCC and decrease the ecological risk of TCC when applied to sewage sludge.

The Different Facets of Triclocarban: A Review

In the late 1930s and early 1940s, it was discovered that the substitution on aromatic rings of hydrogen atoms with chlorine yielded a novel chemistry of antimicrobials. However, within a few years, many of these compounds and formulations showed adverse effects, including human toxicity, ecotoxicity, and unwanted environmental persistence and bioaccumulation, quickly leading to regulatory bans and phase-outs. Among these, the triclocarban, a polychlorinated aromatic antimicrobial agent, was employed as a major ingredient of toys, clothing, food packaging materials, food industry floors, medical supplies, and especially of personal care products, such as soaps, toothpaste, and shampoo. Triclocarban has been widely used for over 50 years, but only recently some concerns were raised about its endocrine disruptive properties. In September 2016, the U.S. Food and Drug Administration banned its use in over-the-counter hand and body washes because of its toxicity. The withdrawal of triclocarban has prompted the efforts to search for new antimicrobial compounds and several analogues of triclocarban have also been studied. In this review, an examination of different facets of triclocarban and its analogues will be analyzed.

Searching for Small Molecules as Antibacterials: Non-Cytotoxic Diarylureas Analogues of Triclocarban

Triclocarban (TCC), a broad-spectrum lipophilic antimicrobial agent, is a diarylurea derivative that has been used for more than 60 years as a major ingredient of toys, clothing, food packaging materials, food industry floors, medical supplies and especially of personal care products, such as soaps, toothpaste and shampoo. In September 2016, the U.S. FDA banned nineteen antimicrobial ingredients, including TCC, in over-the-counter consumer antiseptic wash products, due to their toxicity. Withdrawal of TCC has prompted efforts to search for new antimicrobial compounds. In this paper, we present the synthesis and biological evaluation, as antibiotic and non-cytotoxic agents, of a series of diarylureas, analogues of TCC. These compounds are characterized by an intriguingly simple chemistry and can be easily synthesized. Among the synthesized compounds, 1ab and 1bc emerge as the most interesting compounds as they show the same activity of TCC (MIC = 16 µg/mL) against Staphylococcus aureus, and a higher activity than TCC against Enterococcus faecalis (MIC = 32 µg/mL versus MIC = 64 µg/mL). Moreover, 1ab and 1bc show no cytotoxicity towards the human mammary epithelial cells MCF-10A and embryonic kidney epithelial cells Hek-293, in opposition to TCC, which exhibits a marked cytotoxicity on the same cell lines and shows a good antitumor activity on a panel of cell lines tested.

Impact of high precipitation and temperature events on the distribution of emerging contaminants in surface water in the Mid-Atlantic, United States

Extreme weather events induced by climate change have potential to impact water quality and have received increasing attention from surface water source management perspectives. However, it remains unclear how such phenomenon may influence concentration of emerging contaminants (ECs) in surface water that are vital source of irrigation. In the present study, we investigated the impact of high precipitation and ambient temperature on the distribution of ECs in surface water samples (N = 250) from Mid-Atlantic region, collected between 2016 and 2018. We analyzed the water samples using a liquid chromatography tandem mass spectrometry (LC-MS/MS) based method. We then investigated how the detection frequencies and concentrations of ten emerging contaminants were influenced by high precipitation and temperature events in the previous day or 7 days prior to the sampling events using a generalized additive model (GAM). We observed that heavy rainfalls occurring within 24 h before sampling increased the concentration/likelihood of detection of the ECs in surface waters, likely due to surface runoffs, remobilization from soil/sediment and sewage overflows. The impact of high precipitation during previous seven days varied across chemicals. Likewise, the detection frequency and concentration of most analytes increased with increasing temperature, in previous day of sampling event, likely due to enhanced solubility in water. Long-term high temperature events appeared to decrease the detection of the most tested ECs probably due to enhanced degradation. However, the potential risk of unknown degradation products cannot be ignored. Our results indicate potential decline of water quality after extreme weather events which may have implications for water source management under changing climate.

Combined bioaugmentation with electro-biostimulation for improved bioremediation of antimicrobial triclocarban and PAHs complexly contaminated sediments

Haloaromatic antimicrobial triclocarban (TCC) is an emerging refractory contaminant that commonly coexisted with conventional contaminants such as polycyclic aromatic hydrocarbons (PAHs). TCC may negatively affect the metabolic activity of sediment microorganisms and persist in environment; however, remediation methods that relieve the TCC inhibitory effect in sediments remain unknown. Here, a novel electro-biostimulation and bioaugmentation combined remediation system was proposed by the simultaneous introduction of a TCC-degrading Ochrobactrum sp. TCC-2 and electrode into the TCC and PAHs co-contaminated sediments. Results indicated the PAHs and TCC degradation efficiencies of the combined system were 2.9-3.0 and 4.6 times respectively higher than those of the control group (no electro-biostimulation and no bioaugmentation treatments). The introduced strain TCC-2 and the enriched electroactive bacteria and PAHs degraders (e.g. Desulfobulbus, Clostridium, and Paenarthrobacter) synergistically contributed to the accelerated degradation of PAHs and TCC. The preferential elimination of the TCC inhibitory effect through bioaugmentation treatment could restore microbial functions by increasing the functional gene abundances related to various metabolic processes. This study offers new insights into the response of sediment functional communities to TCC stress, electro-biostimulation and bioaugmentation operations and provides a promising system for the enhanced bioremediation of the PAHs and TCC co-contaminated sediments.

Diarylureas: Repositioning from Antitumor to Antimicrobials or Multi-Target Agents against New Pandemics

Antimicrobials have allowed medical advancements over several decades. However, the continuous emergence of antimicrobial resistance restricts efficacy in treating infectious diseases. In this context, the drug repositioning of already known biological active compounds to antimicrobials could represent a useful strategy. In 2002 and 2003, the SARS-CoV pandemic immobilized the Far East regions. However, the drug discovery attempts to study the virus have stopped after the crisis declined. Today’s COVID-19 pandemic could probably have been avoided if those efforts against SARS-CoV had continued. Recently, a new coronavirus variant was identified in the UK. Because of this, the search for safe and potent antimicrobials and antivirals is urgent. Apart from antiviral treatment for severe cases of COVID-19, many patients with mild disease without pneumonia or moderate disease with pneumonia have received different classes of antibiotics. Diarylureas are tyrosine kinase inhibitors well known in the art as anticancer agents, which might be useful tools for a reposition as antimicrobials. The first to come onto the market as anticancer was sorafenib, followed by some other active molecules. For this interesting class of organic compounds antimicrobial, antiviral, antithrombotic, antimalarial, and anti-inflammatory properties have been reported in the literature. These numerous properties make these compounds interesting for a new possible pandemic considering that, as well as for other viral infections also for CoVID-19, a multitarget therapeutic strategy could be favorable. This review is meant to be an overview on diarylureas, focusing on their biological activities, not dwelling on the already known antitumor activity. Quite a lot of papers present in the literature underline and highlight the importance of these molecules as versatile scaffolds for the development of new and promising antimicrobials and multitarget agents against new pandemic events.

A Review on the Fate of Legacy and Alternative Antimicrobials and Their Metabolites during Wastewater and Sludge Treatment

Antimicrobial compounds are used in a broad range of personal care, consumer and healthcare products and are frequently encountered in modern life. The use of these compounds is being reexamined as their safety, effectiveness and necessity are increasingly being questioned by regulators and consumers alike. Wastewater often contains significant amounts of these chemicals, much of which ends up being released into the environment as existing wastewater and sludge treatment processes are simply not designed to treat many of these contaminants. Furthermore, many biotic and abiotic processes during wastewater treatment can generate significant quantities of potentially toxic and persistent antimicrobial metabolites and byproducts, many of which may be even more concerning than their parent antimicrobials. This review article explores the occurrence and fate of two of the most common legacy antimicrobials, triclosan and triclocarban, their metabolites/byproducts during wastewater and sludge treatment and their potential impacts on the environment. This article also explores the fate and transformation of emerging alternative antimicrobials and addresses some of the growing concerns regarding these compounds. This is becoming increasingly important as consumers and regulators alike shift away from legacy antimicrobials to alternative chemicals which may have similar environmental and human health concerns.

Characterization of triclosan and triclocarban in indoor dust from home micro-environments in Vietnam and relevance of non-dietary exposure

Contamination status, spatial variability, and exposure risk of triclosan (TCS) and triclocarban (TCC) in indoor dusts from different micro-environments were evaluated for the first time in Vietnam as well as in Southeast Asian region. TCS and TCC were measured in 89 dust samples collected from bedrooms, living rooms, and kitchens of private houses in four northern cities including Hanoi, Bac Ninh, Hung Yen, and Nam Dinh, by means of liquid chromatography-tandem mass spectrometry. Concentrations of TCS and TCC ranged from <5 to 1090 (median 33.2) and from <3 to 531 (median 19.3) ng g^-1, respectively. Concentrations of TCS and TCC in the kitchen and bedroom dusts were markedly higher than levels found in the living room samples, probably due to their applications in kitchen utensils, household cleaning reagents, and personal care products. A strong positive correlation between TCS and TCC concentrations was detected in the whole dataset (R² = 0.810, p < 0.001). For samples in which both TCS and TCC were quantified, TCS/TCC ratios ranged from 0.3 to 12 with a median value of 1.8, and did not show big differences between micro-environments. Human exposures to TCS and TCC through dust ingestion were estimated for various age groups with 95% CI daily intake doses ranging from (0.032-0.070) to (0.340-0.740) and from (0.017-0.033) to (0.175-0.345) ng kg-bw^-1 d^-1 for adults and infants respectively. Although our derived values were much lower than reference doses, more comprehensive risk assessment considering multiple exposure pathways of TCS and TCC is needed.

Disposition and metabolism of antibacterial agent, triclocarban, in rodents; a species and route comparison

Triclocarban is a residue-producing antibacterial agent used in a variety of consumer products. These studies investigated the disposition and metabolism of [¹⁴C]triclocarban. In male rats following a single gavage administration of 50, 150, and 500 mg/kg, excretion was primarily via feces (feces, 85-86%; urine, 3-6%) with no apparent dose-related effect. In male rats, 29% of the administered dose was excreted in bile suggesting some of the fecal excretion is from the absorbed dose which was excreted to the intestine via bile. The tissue retention of radioactivity was low in male rats (24 h, 3.9%; 72 h, 0.1%). Disposition pattern following gavage administration of 50 mg/kg in female rats and male and female mice were similar to male rats. Plasma elimination half-life of triclocarban in rats following gavage administration was shorter (∼2 h) compared to that based on total radioactivity (≥9 h) which included all products of triclocarban. Absorption following a single dermal application of 1.5 or 3% was low (≤3%) in rodents. Hydroxylated and conjugated metabolites of triclocarban predominated in bile. In hepatocytes, clearance of triclocarban in mouse and human was similar and was faster than in rat.