Assessment of ecological hazards and environmental fate of disinfectant quaternary ammonium compounds

Fate of quaternary ammonium compounds upon the UV/monochloramine process: Kinetics, transformation pathways and the formation of N-nitroso-N-methyl-N-alkylamines

Quaternary ammonium compounds (QACs) are widely detected in the aquatic environment due to their extensive use in a wide array of antibacterial products during the pandemic. In the current study, UV/monochloramine (UV/NH2Cl) was used to degrade three typical QACs, namely benzalkonium compounds (BACs), dialkyl dimethyl ammonium compounds (DADMACs), and alkyl trimethyl ammonium compounds (ATMACs). This process achieved high efficiency in removing BACs from water samples. The transformation products of QACs treated with UV/NH2Cl were identified and characterized using a high-resolution mass spectrometer, and transformation pathways were proposed. The formation of N-nitroso-N-methyl-N-alkylamines (NMAs) and N-nitrosodimethylamine (NDMA) were observed during QAC degradation. The molar formation yield of NDMA from C12-BAC was 0.04 %, while yields of NMAs reached 1.05 %. The ecotoxicity of NMAs derived from QACs was predicted using ECOSAR software. The increased toxicity could be attributed to the formation of NMAs with longer alkyl chains; these NMAs, exhibited a one order of magnitude increase in toxicity compared to their parent QACs. This study provides evidence that QACs are the specific and significant precursors of NMAs. Greater attention should be given to NMA formation and its potential threat to the ecosystem, including humans.

Developing a Passive Dosing Method for Acute Aquatic Toxicity Tests of Cationic Surfactant Benzalkoniums (BACs)

Benzalkonium chlorides (BACs) have been of environmental concern due to their widespread use and potential harm. However, challenges arise in defining and controlling the exposure concentration (Cw) in aquatic toxicity tests involving BACs with a long alkyl chain (i.e., #C > 14). To address this, a novel passive dosing method was introduced in the 48 h-acute ecotoxicity test on Daphnia magna and compared to the conventional solvent-spiking method in terms of Cw stability and toxicity results. Among 13 sorbent materials tested for their sorption capacity, poly(ether sulfone) (PES) membrane was an optimal passive dosing reservoir, with equilibrium desorption of BACs to water achieved within 24 h. The Cw of BACs remained constant in both applied dosing methods during the test period. However, the Cw in solvent-spiking tests was lower than the nominal concentration for long-chain BACs, particularly at low exposure concentrations. Notably, the solvent-spiking tests indicated that the toxicity of BACs increased with alkyl chain length from C6 to 14, followed by a decline in toxicity from C14 to 18. In contrast, the passive dosing method displayed similar or slightly increasing toxicity levels of BACs from C14 to C18, indicating higher toxicity of C16 and C18-BACs than that inferred by the solvent spiking test. These findings emphasize the potential of applying this innovative passive dosing approach in aquatic toxicity tests to generate reliable and accurate toxicity data and support a comprehensive risk assessment of cationic surfactants.

Fabrication of multifunctional cotton fabrics with quaternized N-halamine endowing the synergetic rechargeable antibacterial, wound healing and self-cleaning performances

Cotton has attracted considerable attention due to its functional characteristics. The focus of research on cotton has shifted in recent years towards designing multi-functional and modified media for cotton fibers, which can be firmly combined with textiles, giving them reusability and extending their service life. This study constructed a synergistic antibacterial layer of quaternary ammonium compounds (QACs) and N-halamine (Hals) using an in-situ free radical copolymerization method in water, named QACs/Hals@cotton-Cl. The route significantly increases the number of antibacterial active centers. FTIR, XPS, and SEM were used to systematically analyze the product's chemical structure, surface morphology, and other characteristics. The modified fabric's antibacterial efficiency, wound healing, renewability, and durability were also evaluated. The chlorinated modified cotton fabric could completely eradicate S. aureus and E. coli within 10 min. Compared with pure cotton, it notably promoted the healing rate of infected wounds in mice. The modification method imparted excellent hydrophobicity to the cotton fabric, with a contact angle exceeding 130°, making it easy to remove surface stains. After 30 days of regular storage and 24 h of UV irradiation, the active chlorine concentration (Cl+%) only decreased by 25 % and 39 %, respectively, and the reduced Cl+% was effectively recharged via simple re-chlorination. The hydrophobicity and antimicrobial properties of QACs/Hals@cotton-Cl remained stable even after 20 cycles of friction. This simple synthesis technique provides a convenient approach for the scalable fabrication of multifunctional and rechargeable antibacterial textiles, with potential applications in medical devices and personal hygiene protection.

Screening for frequently detected quaternary ammonium mixture systems in waters based on frequent itemset mining and prediction of their toxicity

Screening and prioritizing research on frequently detected mixture systems in the environment is of great significance, as conducting toxicity testing on all mixtures is impractical. Therefore, the frequent itemset mining (FIM) was introduced and applied in this paper to identify variables that commonly co-occur in a dataset. Based on the dataset of the quaternary ammonium compounds (QACs) in the water environment, the four frequent QAC mixture systems with detection rate ≥ 35 % were found, including [BDMM]+Cl--[BTMM]+Cl- (M1), [BDMM]+Cl--[BHMM]+Cl- (M2), [BTMM]+Cl- -[BHMM]+Cl- (M3), and [BDMM]+Cl--[BTMM]+Cl--[BHMM]+Cl- (M4). [BDMM]+Cl-, [BTMM]+Cl-, and [BHMM]+Cl- are benzyl dodecyl dimethyl ammonium chloride, benzyl tetradecyl dimethyl ammonium chloride, and benzyl hexadecyl dimethyl ammonium chloride, respectively. Then, the toxicity of the representative mixture rays and components for the four frequently detected mixture systems was tested using Vibrio qinghaiensis sp.-Q67 (Q67) as a luminescent indicator organism at 0.25 and 12 h. The toxicity of the mixtures was predicted using concentration addition (CA) and independent action (IA) models. It was shown that both the components and the representative mixture rays for the four frequently detected mixture systems exhibited obvious acute and chronic toxicity to Q67, and their median effective concentrations (EC50) were below 7 mg/L. Both CA and IA models predicted the toxicity of the four mixture systems well. However, the CA model had a better predictive ability for the toxicity of the M3 and M4 mixtures than IA at 12 h.

Phage cocktail superimposed disinfection: A ecological strategy for preventing pathogenic bacterial infections in dairy farms

Bovine mastitis (BM) is mainly caused by bacterial infection that has a highly impact on dairy production, affecting both economic viability and animal well-being. A cross-sectional study was conducted in dairy farms to investigate the prevalence and antimicrobial resistance patterns of bacterial pathogens associated with BM. The analysis revealed that Staphylococcus (49%), Escherichia (16%), Pseudomonas (11%), and Klebsiella (6%) were the primary bacterial pathogens associated with mastitis. A significant proportion of Staphylococcus strains displayed multiple drug resistance. The use of disinfectants is an important conventional measure to control the pathogenic bacteria in the environment. Bacteriophages (Phages), possessing antibacterial properties, are natural green and effective disinfectants. Moreover, they mitigate the risk of generating harmful disinfection byproducts, which are commonly associated with traditional disinfection methods. Based on the primary bacterial pathogens associated with mastitis in the investigation area, a phage cocktail, named SPBC-SJ, containing seven phages capable of lysing S. aureus, E. coli, and P. aeruginosa was formulated. SPBC-SJ exhibited superior bactericidal activity and catharsis effect on pollutants (glass surface) compared to chemical disinfectants. Clinical trials confirmed that the SPBC-SJ-based superimposed disinfection group (phage combined with chemical disinfectants) not only cut down the dosage of disinfectants used, but significantly reduced total bacterial counts on the ground and in the feeding trough of dairy farms. Furthermore, SPBC-SJ significantly reduced the abundance of Staphylococcus and Pseudomonas in the environment of the dairy farm. These findings suggest that phage-based superimposed disinfection is a promising alternative method to combat mastitis pathogens in dairy farms due to its highly efficient and environmentally-friendly properties.

Current insights into the effects of cationic biocides exposure on Enterococcus spp

Cationic biocides (CBs), such as quaternary ammonium compounds and biguanides, are critical for controlling the spread of bacterial pathogens like Enterococcus spp., a leading cause of multidrug-resistant healthcare-associated infections. The widespread use of CBs in recent decades has prompted concerns about the potential emergence of Enterococcus spp. populations exhibiting resistance to both biocides and antibiotics. Such concerns arise from their frequent exposure to subinhibitory concentrations of CBs in clinical, food chain and diverse environmental settings. This comprehensive narrative review aimed to explore the complexity of the Enterococcus' response to CBs and of their possible evolution toward resistance. To that end, CBs' activity against diverse Enterococcus spp. collections, the prevalence and roles of genes associated with decreased susceptibility to CBs, and the potential for co- and cross-resistance between CBs and antibiotics are reviewed. Significant methodological and knowledge gaps are identified, highlighting areas that future studies should address to enhance our comprehension of the impact of exposure to CBs on Enterococcus spp. populations' epidemiology. This knowledge is essential for developing effective One Health strategies that ensure the continued efficacy of these critical agents in safeguarding Public Health.

Synergistic Bactericidal Effects of Quaternary Ammonium Compounds with Essential Oil Constituents

Antimicrobial tolerance is a significant concern in the food industry, as it poses risks to food safety and public health. To overcome this challenge, synergistic combinations of antimicrobials have emerged as a potential solution. In this study, the combinations of two essential oil constituents (EOCs), namely carvacrol (CAR) and eugenol (EUG), with the quaternary ammonium compounds (QACs) benzalkonium chloride (BAC) and didecyldimethylammonium chloride (DDAC) were evaluated for their antimicrobial effects against Escherichia coli and Bacillus cereus, two common foodborne bacteria. The checkerboard assay was employed to determine the fractional inhibitory concentration index (FICI) and the fractional bactericidal concentration index (FBCI), indicating the presence of bactericidal, but not bacteriostatic, synergy in all QAC-EOC combinations. Bactericidal synergism was clearly supported by Bliss independence analysis. The bactericidal activity of the promising synergistic combinations was further validated by time-kill curves, achieving a >4-log10 reduction of initial bacterial load, which is significant compared to typical industry standards. The combinations containing DDAC showed the highest efficiency, resulting in the eradication of bacterial population in less than 2-4 h. These findings emphasize the importance of considering both bacteriostatic and bactericidal effects when evaluating antimicrobial combinations and the potential of EOC-QAC combinations for sanitization and disinfection in the food industry.

Effect of Organic Cation Adsorption on Ion-Transport Selectivity in a Cation-Permselective Nanopore Membrane

A key knowledge gap in the emerging field of nanofluidics concerns how the ionic composition and ion-transport properties of a nanoconfined solution differ from those of a contacting bulk solution. We and others have been using potentiometric concentration cells, where a nanopore or nanotube membrane separates salt solutions of differing concentrations to explore this issue. The membranes studied contained a fixed pore/tube wall anionic charge, which ideally would prohibit anions and salt from entering the pore/tube-confined solution. We have been investigating experimental conditions that allow for this ideally permselective cation state to be achieved. Results of potentiometric investigations of a polymeric nanopore membrane (10 ± 2 nm-diameter pores) with anionic charge due to carbonate are presented here. While studies of this type have been reported using alkaline metal and alkaline earth cations, there have been no analogous studies using organic cations. This paper uses a homologous series of tetraalkylammonium ions to address this knowledge gap. The key result is that, in contrast to the inorganic cations, the ideal cation-permselective state could not be obtained under any experimental conditions for the organic cations. We propose that this is because these hydrophobic cations adsorb onto the polymeric pore walls. This makes ideality impossible because each adsorbed alkylammonium must bring a charge-balancing anion, Cl-, with it into the nanopore solution. The alkylammonium adsorption that occurred was confirmed and quantified by using surface contact angle measurements.

Evaluating quaternium-15 effects on Mytilus galloprovincialis: New insights on physiological and cellular responses

Among personal care products, quaternium-15 is prominently featured as a preservative in items such as shampoos, soaps, shaving products, and cosmetics. The widespread use of these products in people's daily routines contributes to quaternium-15 release into aquatic ecosystems. In this context, the primary aim of the study was to assess the physiological and cellular responses of the digestive gland and gills in Mytilus galloprovincialis to quaternium-15 exposure. Cell viability and the ability of digestive gland cells to regulate their volume were evaluated. Additionally, the expression of the genes involved in oxidative stress response was assessed to further substantiate the compound's harmful effects. Results indicated a significant decrease in both the viability of digestive gland cells and their RVD (regulatory volume decrease) capacity when exposed to a hypotonic solution. Furthermore, impairment of digestive gland cell function was corroborated by the modulation of oxidative stress-related gene expression, including SOD, Cat, as well as Hsp70 and CYP4Y1. Similar gene expression alterations were observed in the gills, reflecting impaired functionality in this vital organ as well. In summary, the outcomes of the study provide conclusive evidence of the toxicity of quaternium-15. This underscores the urgent need to further investigate the toxicological effects of this contaminant on aquatic ecosystems and emphasises the necessity of limiting the use of products containing quaternium-15.

Toxicity and chemical characterization of shale gas wastewater discharged to the receiving water: Evidence from toxicity identification evaluation

Flowback and produced water (FPW) generated from shale gas extraction is a complex mixture consisting of injected drilling fluid, deep formation water, and byproducts of downhole reactions. Limited knowledge is available regarding the impact of discharged FPW on surface water in China. With the development of shale gas exploitation, this emphasizes an urgent need for comprehensive assessments and stringent regulations to ensure the safe disposal of shale gas extraction-related wastewater. Herein, we explored potential impacts of treated shale gas wastewater discharged into a local river in southwest China through toxicity identification evaluation (TIE). Results revealed that organics and particulates significantly contributed to the overall toxicity of the treated FPW wastewater. Through target and suspect chemical analyses, various categories of organic contaminants were detected, including alkanes, aromatic hydrocarbons, biocides, phenols, and phthalates. Furthermore, non-target analysis uncovered the presence of surfactant-related contaminants in tissues of exposed organisms, but their contribution to the observed toxicity was unclear due to the lack of effect data for these compounds. Higher toxicity was found at the discharge point compared with upstream sites; however, the toxicity was rapidly mitigated due to dilution in the receiving river, posing little impact on downstream areas. Our study highlighted the importance of monitoring toxicity and water quality of FPW effluent even though dilution could be a viable approach when the water volume in the discharge was small.

Toxicity of the disinfectant benzalkonium chloride (C14) towards cyanobacterium Microcystis results from its impact on the photosynthetic apparatus and cell metabolism

Quaternary ammonium compounds (QACs) are commonly used in a variety of consumer and commercial products, typically as a component of disinfectants. During the COVID-19 pandemic, QACs became one of the primary agents utilized to inactivate the SARS-CoV-2 virus on surfaces. However, the ecotoxicological effects of QACs upon aquatic organisms have not been fully assessed. In this study, we examined the effects of a widely used QAC (benzalkonium chloride-C14, BAC-14) on two toxigenic Microcystis strains and one non-toxigenic freshwater Microcystis strain and carried out an analysis focused on primary, adaptive and compensatory stress responses at apical (growth and photosynthesis) and metabolic levels. This analysis revealed that the two toxic Microcystis strains were more tolerant than the non-toxic strain, with 96 hr-EC50 values of 0.70, 0.76, and 0.38 mg/L BAC-14 for toxigenic M. aeruginosa FACHB-905, toxigenic M. aeruginosa FACHB-469, and non-toxigenic M. wesenbergii FACHB-908, respectively. The photosynthetic activities of the Microcystis, assessed via Fv/Fm values, were significantly suppressed under 0.4 mg/L BAC-14. Furthermore, this analysis revealed that BAC-14 altered 14, 12, and 8 metabolic pathways in M. aeruginosa FACHB-905, M. aeruginosa FACHB-469, and M. wesenbergii FACHB-908, respectively. It is noteworthy that BAC-14 enhanced the level of extracellular microcystin production in the toxigenic Microcystis strains, although cell growth was not significantly affected. Collectively, these data show that BAC-14 disrupted the physiological and metabolic status of Microcystis cells and stimulated the production and release of microcystin, which could result in damage to aquatic systems.

A review on sterilization methods of environmental decontamination to prevent the coronavirus SARS-CoV-2 (COVID-19 virus): A new challenge towards eco-friendly solutions

In recent years, the COVID-19 pandemic is currently wreaking havoc on the planet. SARS-CoV-2, the Severe Acute Respiratory Syndrome Coronavirus, is the current term for this outbreak. Reports about this novel coronavirus have been presented since the pandemic's breakout, and they have demonstrated that it transmits rapidly from person to person, primarily by droplets in the air. Findings have illustrated that SARS-CoV-2 can survive on surfaces from hours to days. Therefore, it is essential to find practical solutions to reduce the virus's impact on human health and the environment. This work evaluated common sterilization methods that can decontaminate the environment and items. The goal is that healthcare facilities, disease prevention organizations, and local communities can overcome the new challenge of finding eco-friendly solutions. Further, a foundation of information encompassing various sterilization procedures and highlighting their limits to choose the most appropriate method to stop disease-causing viruses in the new context has been presented. The findings of this crucial investigation contribute to gaining insight into the comprehensive sterilization approaches against the coronavirus for human health protection and sustainable environmental development.

Beneficial or harmful: Time-dependent hormesis induced by typical disinfectants and their mixtures with toxicological interaction

Disinfectants and their mixtures can induce hormesis. However, how the mixture hormesis is related to those of components and the interactions in disinfectant mixtures remain unclear. In this paper, the luminescence inhibition toxicities of chlorinated sodium phosphate (CSP), dodecyl dimethyl benzyl ammonium bromide (DOB), dodecyl dimethyl benzyl ammonium chloride (DOC), ethanol (EtOH), glutaraldehyde (GLA), hydrogen peroxide (H2O2), isopropyl alcohol (IPA), n-propanol (NPA), and 20 mixture rays in four mixture systems (EtOH-H2O2, DOB-H2O2, DOC-EtOH, and EtOH-IPA-NPA) containing at least one component showing hormesis to Vibrio qinghaiensis sp.-Q67 (Q67) were determined at 0.25, 3, 6, 9, and 12 h. The synergism-antagonism heatmap based on independent action model (noted as SAHmapIA) was developed to systematically evaluate the interactions in various mixtures. It was shown that five disinfectants (CSP, EtOH, H2O2, NPA, and IPA) and 17 mixture rays exhibited time-dependent hormesis. The hormetic component was responsible for the hormesis of the mixture rays. Most mixture rays showed low- concentration/dose additive action and high-concentration/dose synergism at different time. This study further exemplified the interrelationship between the hormesis in the mixtures and their components and implied the need to pay attention to the time-dependent hormesis and interactions induced by the disinfectants.

Efficacy of quaternary ammonium salt-based disinfectant or chelated copper-zinc footbath solution in the treatment of digital dermatitis on one research dairy farm in Taiwan

BACKGROUND

Footbaths can be used to manage digital dermatitis (DD), a common cause of lameness in dairy cattle. Copper sulfate and chelated copper-zinc (CZS) solutions in footbaths are potentially harmful to the environment.

HYPOTHESIS/OBJECTIVES

To determine if a quaternary ammonium salt-based disinfectant (QASD) footbath is as effective as a chelated CZS solution in controlling DD in dairy cows.

ANIMALS

Fifty-one lactating Holstein cows were randomly assigned to one of two treatment groups, with DD status based on the M-stage scoring system and locomotion score balanced between treatment groups.

MATERIALS AND METHODS

The groups were treated with a 1% QASD or a 2.5% chelated CZS. Footbaths were performed once per week for 15 weeks. Logistic regression was used to analyse clinical improvement. All cows received appropriate medical treatment for DD and other hoof diseases.

RESULTS

Clinical improvement rates were 67% in the QASD group and 38% in the CZS group (p = 0.03). Logistic regression analysis showed that the odds (95% confidence interval) for clinical improvement rate in the CZS group were 0.30 (0.095-0.948) times that of the QASD group (p = 0.04). The M0 score in the QASD and CZS groups increased significantly (p < 0.05) at the end of the 15 week study period. In the QASD group, the proportion of M2, M3 and M4 scores were significantly decreased (p < 0.05).

CONCLUSION AND CLINICAL RELEVANCE

Over a 15 week period, QASD for footbathing was associated with a lower prevalence of active DD lesions than when using CZS.

Individual and combined ecotoxic effects of water-soluble polymers

Water-soluble polymers (WSPs) are a class of high-molecular-weight compounds which are widely used in several applications, including water treatment, food processing, and pharmaceuticals. Therefore, they pose a potential threat for water resources and aquatic ecosystems. We assessed the ecotoxicity of four WSPs-non-ionic polyacrylamide (PAM) and polyethylene glycol (PEG-200), anionic homopolymer of acrylic acid (P-AA), and cationic polyquaternium-6 (PQ-6)-as single compounds and in mixture. For this purpose in vitro and in vivo assays were used to record baseline toxicity, mutagenic potential, endocrine effects, and growth inhibition in the freshwater alga Raphidocelis subcapitata. Furthermore, the mixture toxicity of the two polymers P-AA and PQ-6 which showed effects in the algae tests was evaluated with the concentration addition (CA), independent action (IA), and generalized concentration addition (GCA) model and compared with experimental data. No toxic effects were observed among the polymers and their mixtures in the in vitro assays. On the contrary, in the growth inhibition test with R. subcapitata the cationic PQ-6 caused high inhibition while the anionic P-AA and its mixture with the cationic polymer caused low inhibition. The non-ionic polymers PEG-200 and PAM showed no effect in R. subcapitata in the tested concentration range up to 100 mg/L. The IA model represented the mixture effect of the combination experiment better than the CA and GCA models. The results indicate (1) that the toxic effects of anionic and cationic polymers are most likely due to interactions of the polymers with the surfaces of organisms or with nutrients in the water and (2) that the polymers elicit their effects through different mechanisms of action that do not interact with each other.

Risks of benzalkonium chlorides as emerging contaminants in the environment and possible control strategies from the perspective of ecopharmacovigilance

An unprecedented increase in the use of disinfection products triggered by the coronavirus disease 2019 (COVID-19) pandemic is resulting in aggravating environmental loads of disinfectants as emerging contaminants, which has been considered a cause for worldwide secondary disasters. This review analyzed the literature published in the last decade about occurrence, bioaccumulation, and possible environmental risks of benzalkonium chlorides (BKCs) as emerging contaminants. Results indicated that BKCs globally occurred in municipal wastewater, surface water, groundwater, reclaimed water, sludge, sediment, soil, roof runoff, and residential dust samples across 13 countries. The maximum residual levels of 30 mg/L and 421 μg/g were reported in water and solid environmental samples, respectively. Emerging evidences suggested possible bioaccumulation of BKCs in plants, even perhaps humans. Environmentally relevant concentrations of BKCs exert potential adverse impacts on aquatic and terrestrial species, including genotoxicity, respiratory toxicity, behavioural effects and neurotoxicity, endocrine disruption and reproductive impairment, phytotoxicity, etc. Given the intrinsic biocidal and preservative properties of disinfectants, the inductive effects of residual BKCs in environment in terms of resistance and imbalance of microorganisms have been paid special attention. Considering the similarities of disinfectants to pharmaceuticals, from the perspective of ecopharmacovigilance (EPV), a well-established strategy for pharmaceutical emerging contaminants, we use the control of BKC pollution as a case, and provide some recommendations for employing the EPV measures to manage environmental risks posed by disinfectant emerging contaminants.

Electrochemical-based approaches for the treatment of pharmaceuticals and personal care products in wastewater

In recent times, emerging contaminants (ECs) like pharmaceuticals and personal care products (PPCPs) in water and wastewater have become a major concern in the environment. Electrochemical treatment technologies proved to be more efficient to degrade or remove PPCPs present in the wastewater. Electrochemical treatment technologies have been the subject of intense research for the past few years. Attention has been given to electro-oxidation and electro-coagulation by industries and researchers, indicating their potential to remediate PPCPs and mineralization of organic and inorganic contaminants present in wastewater. However, difficulties arise in the successful operation of scaled-up systems. Hence, researchers have identified the need to integrate electrochemical technology with other treatment technologies, particularly advanced oxidation processes (AOPs). Integration of technologies addresses the limitation of indiviual technologies. The major drawbacks like formation of undesired or toxic intermediates, s, energy expenses, and process efficacy influenced by the type of wastewater etc., can be reduced in the combined processes. The review discusses the integration of electrochemical technology with various AOPs, like photo-Fenton, ozonation, UV/H2O2, O3/UV/H2O2, etc., as an efficient way to generate powerful radicals and augment the degradation of organic and inorganic pollutants. The processes are targeted for PPCPs such as ibuprofen, paracetamol, polyparaben and carbamezapine. The discussion concerns itself with the various advantages/disadvantages, reaction mechanisms, factors involved, and cost estimation of the individual and integrated technologies. The synergistic effect of the integrated technology is discussed in detail and remarks concerning the prospects subject to the investigation are also stated.

Efficient degradation of benzalkonium chloride by FeMn-CA300 catalyst activated persulfate process: Surface hydroxyl potentiation mechanism and degradation pathway

The consumption of disinfectants increased dramatically with the outbreak of the COVID-19 epidemic. Benzalkonium chloride (DDBAC), a cationic surfactant disinfectant for import and export cargoes, is used for effective degradation method. For DDBAC effective degradation, polyhedral Fe-Mn bimetallic catalyst of Prussian blue analogue (FeMn-CA300) was novelty developed for rapid peroxymonosulfate (PMS) activation. Results showed that the Fe/Mn redox and surface hydroxyl groups in the catalyst played an important role in the DDBAC-enhanced degradation. The removal effectiveness of 10 mg L-1 DDBAC was up to 99.4% in 80 min under the initial pH = 7, catalyst dosage of 0.4 g L-1, and PMS concentration of 15 mmol L-1. In addition, FeMn-CA300 had a wide pH applicability range. The results indicated that hydroxyls, sulfate radicals, and singlet oxygen could effectively improve the degradation efficiency, where sulfate radicals played a crucial role. Finally, the corresponding degradation path of DDBAC was further provided according to GC-MS results. The results of this study provide new insights into the degradation of DDBAC, thereby highlighting the great potential of FeMnca300/PMS to control refractory organic compounds in the aqueous phase.

Determination of 25 quaternary ammonium compounds in sludge by liquid chromatography-mass spectrometry

With the pandemic of COVID-19, the application of quaternary ammonium compounds (QACs), which can be used in SARS-CoV-2 disinfection products, has increased substantially. QACs cumulated in sewer system are ultimately deposited and enriched in sludge. QACs in the environment can adversely affect human health and the environment. In this study, a liquid chromatography-mass spectrometry method was established for the simultaneous determination of 25 QACs in sludge samples. Ultrasonic extraction and filtration of the samples was performed using a 50 mM hydrochloric acid-methanol solution. The samples were separated by liquid chromatography and detected in multiple reaction monitoring mode. The matrix effects of the sludge on the 25 QACs ranged from - 25.5% to 7.2%. All substances showed good linearity in the range of 0.5-100 ng/mL, with all determination coefficients (R2) greater than 0.999. The method detection limits (MDLs) were 9.0 ng/g for alkyltrimethylammonium chloride (ATMAC), 3.0 ng/g for benzylalkyldimethylammonium chloride (BAC), and 3.0 ng/g for dialkyldimethylammonium chloride (DADMAC). The spiked recovery rates were in the range of 74-107%, while the relative standard deviations were in the range of 0.8-20.6%. Considering its sensitivity, accuracy, and easy operation, the proposed method in this study was used to determine 22 sludge samples collected from a comprehensive wastewater treatment plant. The results showed that the concentrations of ΣATMACs, ΣBACs, and ΣDADMACs were 19.684, 3.199, and 8.344 μg/g, respectively. The main components included ATMAC-C16, ATMAC-C18, ATMAC-C20, ATMAC-C22, BAC-C12, and DADMAC-C18:C18, with concentrations exceeding 1.0 μg/g. The concentration relationships of different components in the congeners showed that some components were of similar origin.

Phenylalanine and Tryptophan-Based Surfactants as New Antibacterial Agents: Characterization, Self-Aggregation Properties, and DPPC/Surfactants Vesicles Formulation

Cationic surfactants based on phenylalanine (C_nPC₃NH₃Cl) and tryptophan (C_nTC₃NH₃Cl) were synthesized using renewable raw materials as starting compounds and a green synthetic procedure. The synthesis, acid-base equilibrium, aggregation properties, and antibacterial activity were investigated. Conductivity and fluorescence were used to establish critical micelle concentrations. Micellization of C_nPC₃NH₃Cl and C_nTC₃NH₃Cl occurred in the ranges of 0.42-16.2 mM and 0.29-4.6 mM, respectively. Since those surfactants have some acidic character, the apparent pK_a was determined through titrations, observing increasing acidity with increasing chain length and being slightly more acidic with the phenylalanine than the tryptophan derivatives. Both families showed promising antibacterial efficacy against eight different bacterial strains. Molecular docking studies against the enzyme peptidoglycan glycosyltransferase (PDB ID:2OQO) were used to investigate the potential binding mechanism of target surfactant molecules. According to small angle X-ray scattering (SAXS) results, the surfactants incorporate into DPPC (Dipalmitoyl Phosphatidyl Choline) bilayers without strong perturbation up to high surfactant concentration. Some of the C₁₂TC₃NH₃Cl/DPPC formulations (40%/60% and 20%/80% molar ratios) exhibited good antibacterial activity, while the others were not effective against the tested bacteria. The strong affinity between DPPC and surfactant molecules, as determined by the DFT (density functional theory) method, could be one of the reasons for the loss of antibacterial activity of these cationic surfactants when they are incorporated in vesicles.

Chronic quaternary ammonium compound exposure during the COVID-19 pandemic and the impact on human health

Objective

This review examines a relevant, and underacknowledged, emerging global public health concern—the widespread exposure to quaternary ammonium compounds (QACs) during the COVID-19 pandemic. QACs are a widely used class of cationic surfactants with broad spectrum antimicrobial activity that serve as the active ingredients in antimicrobial products. While these compounds have been used for decades, the production and consumer use of QAC-containing products have steeply risen during the COVID-19 pandemic to control and prevent the spread of the SARS-Cov-2 virus. As a result, human exposure to QACs has also drastically increased.

Methods

This critical review was conducted by searching the key terms “quaternary ammonium compounds,” “disinfectants,” “COVID-19,” “SARS-Cov-2,” “human health,” and “human exposure” in the major search engines, including Google Scholar, PubMed and Science Direct.

Results

QACs are generally considered safe and effective, yet the magnitude of QAC exposure and the subsequent health effects have not been adequately investigated. Recent studies have revealed the potential for bioaccumulation of QACs in blood and tissue. Inhalation and dermal absorption of QACs are identified as the most significant exposure routes for adults, while children and infants may be significantly more vulnerable to QAC exposure and potential adverse health effects.

Conclusions

QACs are an important tool to protect individual and public health, but understanding the impact of widespread QAC exposure is vital to guide best practices for QAC use and minimize the associated health risks. These pandemic era results warrant further investigation and raise additional questions about the short-term and long-term health effects of chronic QAC exposure.

Clinical trial registration

Not applicable.

Quaternary Ammonium Compounds: A Chemical Class of Emerging Concern

Quaternary ammonium compounds (QACs), a large class of chemicals that includes high production volume substances, have been used for decades as antimicrobials, preservatives, and antistatic agents and for other functions in cleaning, disinfecting, personal care products, and durable consumer goods. QAC use has accelerated in response to the COVID-19 pandemic and the banning of 19 antimicrobials from several personal care products by the US Food and Drug Administration in 2016. Studies conducted before and after the onset of the pandemic indicate increased human exposure to QACs. Environmental releases of these chemicals have also increased. Emerging information on adverse environmental and human health impacts of QACs is motivating a reconsideration of the risks and benefits across the life cycle of their production, use, and disposal. This work presents a critical review of the literature and scientific perspective developed by a multidisciplinary, multi-institutional team of authors from academia, governmental, and nonprofit organizations. The review evaluates currently available information on the ecological and human health profile of QACs and identifies multiple areas of potential concern. Adverse ecological effects include acute and chronic toxicity to susceptible aquatic organisms, with concentrations of some QACs approaching levels of concern. Suspected or known adverse health outcomes include dermal and respiratory effects, developmental and reproductive toxicity, disruption of metabolic function such as lipid homeostasis, and impairment of mitochondrial function. QACs' role in antimicrobial resistance has also been demonstrated. In the US regulatory system, how a QAC is managed depends on how it is used, for example in pesticides or personal care products. This can result in the same QACs receiving different degrees of scrutiny depending on the use and the agency regulating it. Further, the US Environmental Protection Agency's current method of grouping QACs based on structure, first proposed in 1988, is insufficient to address the wide range of QAC chemistries, potential toxicities, and exposure scenarios. Consequently, exposures to common mixtures of QACs and from multiple sources remain largely unassessed. Some restrictions on the use of QACs have been implemented in the US and elsewhere, primarily focused on personal care products. Assessing the risks posed by QACs is hampered by their vast structural diversity and a lack of quantitative data on exposure and toxicity for the majority of these compounds. This review identifies important data gaps and provides research and policy recommendations for preserving the utility of QAC chemistries while also seeking to limit adverse environmental and human health effects.

Exposure to Tetrabutylammonium Bromide Impairs Cranial Neural Crest Specification, Neurogenic Program, and Brain Morphogenesis

Tetrabutylammonium bromide (TBAB) is a widely used industrial reagent and is commonly found in our aquatic ecosystem as an industrial byproduct. In humans, the ingestion of TBAB causes severe neurological impairments and disorders such as vertigo, hallucinations, and delirium. Yet, the extent of environmental risk and TBAB toxicity to human health is poorly understood. In this study, we aim to determine the developmental toxicity of TBAB using zebrafish embryos as a model and provide novel insights into the mechanism of action of such chemicals on neurodevelopment and the overall embryonic program. Our results show that exposure to TBAB results in impaired development of the brain, inner ear, and pharyngeal skeletal elements in the zebrafish embryo. TBAB treatment resulted in aberrations in the specification of the neural crest precursors, hindbrain segmentation, and otic neurogenesis. TBAB treatment also induced a surge in apoptosis in the head, tail, and trunk regions of the developing embryo. Long-term TBAB exposure resulted in cardiac edema and craniofacial defects. Further, in silico molecular docking analysis indicated that TBAB binds to AMPA receptors and modulates neural developmental genes such as olfactomedin and acetylcholinesterase in the embryonic brain. To summarize, our study highlights the novel effects of TBAB on embryonic brain formation and segmentation, ear morphogenesis, and craniofacial skeletal development.

Green Surfactants (Biosurfactants): A Petroleum-Free Substitute for Sustainability-Comparison, Applications, Market, and Future Prospects

Surfactants are a group of amphiphilic molecules (i.e., having both hydrophobic and hydrophilic domains) that are a vital part of nearly every contemporary industrial process such as in agriculture, medicine, personal care, food, and petroleum. In general surfactants can be derived from (i) petroleum-based sources or (ii) microbial/plant origins. Petroleum-based surfactants are obvious results from petroleum products, which lead to petroleum pollution and thus pose severe problems to the environment leading to various ecological damages. Thus, newer techniques have been suggested for deriving surfactant molecules and maintaining environmental sustainability. Biosurfactants are surfactants of microbial or plant origins and offer much added advantages such as high biodegradability, lesser toxicity, ease of raw material availability, and easy applicability. Thus, they are also termed "green surfactants". In this regard, this review focused on the advantages of biosurfactants over the synthetic surfactants produced from petroleum-based products along with their potential applications in different industries. We also provided their market aspects and future directions that can be considered with selections of biosurfactants. This would open up new avenues for surfactant research by overcoming the existing bottlenecks in this field.

Knowledge, attitudes and practice regarding environmental friendly disinfectants for household use among residents of China in the post-pandemic period

Background

A sharp rise in household consumption of disinfectants triggered by COVID-19 pandemic has generated tremendous environmental burden and risks of disinfectant emissions in the post-pandemic period. To address this emerging challenge, replacing highly hazardous disinfectants with more environmental friendly alternatives has been accepted as an inherently effective solution to environment issues posed by disinfectant emerging contaminants. However, no study has yet been done to explore the potential customers' attitudes and the market prospect of environmental friendly disinfectants until now.

Methods

This cross-sectional questionnaire-based survey was conducted from January to March, 2022, among resident volunteers in China, to explore the practices, knowledge and attitudes of the public regarding environmental friendly disinfectants for household use.

Results

Among a total of 1,861 Chinese residents finally included in the analyses, 18% agreed or strongly agreed that they paid special attention to the environmental certification label on the product, and only bought the environmental certified disinfectant products; 16% and 10% were using environmental friendly disinfectants for hand sanitization and environmental disinfection, respectively. The mean self-assessed and actual knowledge scores were 2.42 ± 1.74 and 2.12 ± 1.97, respectively, out of a total of 5. Participants having good practices of consuming environmental friendly disinfectants achieved higher knowledge scores. Residents' overall attitudes toward the development, consumption and application of environmental friendly disinfectants were very positive. "Possible conflict between disinfection effectiveness and environmental factor of disinfectants in a context of severe COVID-19 pandemic" was considered as the most important barrier jeopardizing the participants' usage intention for environmental friendly disinfectants.

Conclusions

These data suggested most residents of China had a positive attitude, poor knowledge and practices toward environmental friendly disinfectants. More should be done to enhance the residents' environmental knowledge levels about disinfectants, and to further develop and promote disinfectant products with both excellent disinfection activity and environmentally friendly attributes.

Ecological Risk Analysis for Benzalkonium Chloride, Benzethonium Chloride, and Chloroxylenol in US Disinfecting and Sanitizing Products

Use of three topical antiseptic compounds-benzalkonium chloride (BAC), benzethonium chloride (BZT), and chloroxylenol (PCMX)-has recently increased because of the phaseout of other antimicrobial ingredients (such as triclosan) in soaps and other disinfecting and sanitizing products. Further, use of sanitizing products in general increased during the coronavirus (COVID-19) pandemic. We assessed the environmental safety of BAC, BZT, and PCMX based on best available environmental fate and effects data from the scientific literature and privately held sources. The ecological exposure assessment focused on aquatic systems receiving effluent from wastewater-treatment plants (WWTPs) and terrestrial systems receiving land-applied WWTP biosolids. Recent exposure levels were characterized based on environmental monitoring data supplemented by modeling, while future exposures were modeled based on a hypothetical triclosan replacement scenario. Hazard profiles were developed based on acute and chronic studies examining toxicity to aquatic life (fish, invertebrates, algae, vascular plants) and terrestrial endpoints (plants, soil invertebrates, and microbial functions related to soil fertility). Risks to higher trophic levels were not assessed because these compounds are not appreciably bioaccumulative. The risk analysis indicated that neither BZT nor PCMX in any exposure media is likely to cause adverse ecological effects under the exposure scenarios assessed in the present study. Under these scenarios, total BAC exposures are at least three times less than estimated effect thresholds, while margins of safety for freely dissolved BAC are estimated to be greater than an order of magnitude. Because the modeling did not specifically account for COVID-19 pandemic-related usage, further environmental monitoring is anticipated to understand potential changes in environmental exposures as a result of increased antiseptic use. The analysis presented provides a framework to interpret future antiseptic monitoring results, including monitoring parameters and modeling approaches to address bioavailability of the chemicals of interest. Environ Toxicol Chem 2022;41:3095-3115. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

A fluorescently labelled quaternary ammonium compound (NBD-DDA) to study resistance mechanisms in bacteria

Quaternary ammonium compounds (QACs) are widely used as active agents in disinfectants, antiseptics, and preservatives. Despite being in use since the 1940s, there remain multiple open questions regarding their detailed mode-of-action and the mechanisms, including phenotypic heterogeneity, that can make bacteria less susceptible to QACs. To facilitate studies on resistance mechanisms towards QACs, we synthesized a fluorescent quaternary ammonium compound, namely N-dodecyl-N,N-dimethyl-[2-[(4-nitro-2,1,3-benzoxadiazol-7-yl)amino]ethyl]azanium-iodide (NBD-DDA). NBD-DDA is readily detected by flow cytometry and fluorescence microscopy with standard GFP/FITC-settings, making it suitable for molecular and single-cell studies. As a proof-of-concept, NBD-DDA was then used to investigate resistance mechanisms which can be heterogeneous among individual bacterial cells. Our results reveal that the antimicrobial activity of NBD-DDA against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa is comparable to that of benzalkonium chloride (BAC), a widely used QAC, and benzyl-dimethyl-dodecylammonium chloride (BAC₁₂), a mono-constituent BAC with alkyl-chain length of 12 and high structural similarity to NBD-DDA. Characteristic time-kill kinetics and increased tolerance of a BAC tolerant E. coli strain against NBD-DDA suggest that the mode of action of NBD-DDA is similar to that of BAC. As revealed by confocal laser scanning microscopy (CLSM), NBD-DDA is preferentially localized to the cell envelope of E. coli, which is a primary target of BAC and other QACs. Leveraging these findings and NBD-DDA's fluorescent properties, we show that reduced cellular accumulation is responsible for the evolved BAC tolerance in the BAC tolerant E. coli strain and that NBD-DDA is subject to efflux mediated by TolC. Overall, NBD-DDA's antimicrobial activity, its fluorescent properties, and its ease of detection render it a powerful tool to study resistance mechanisms of QACs in bacteria and highlight its potential to gain detailed insights into its mode-of-action.

Multi-site fungicides suppress banana Panama disease, caused by Fusarium oxysporum f. sp. cubense Tropical Race 4

Global banana production is currently challenged by Panama disease, caused by Fusarium oxysporum f.sp. cubense Tropical Race 4 (FocTR4). There are no effective fungicide-based strategies to control this soil-borne pathogen. This could be due to insensitivity of the pathogen to fungicides and/or soil application per se. Here, we test the effect of 12 single-site and 9 multi-site fungicides against FocTR4 and Foc Race1 (FocR1) in quantitative colony growth, and cell survival assays in purified FocTR4 macroconidia, microconidia and chlamydospores. We demonstrate that these FocTR4 morphotypes all cause Panama disease in bananas. These experiments reveal innate resistance of FocTR4 to all single-site fungicides, with neither azoles, nor succinate dehydrogenase inhibitors (SDHIs), strobilurins or benzimidazoles killing these spore forms. We show in fungicide-treated hyphae that this innate resistance occurs in a subpopulation of "persister" cells and is not genetically inherited. FocTR4 persisters respond to 3 μg ml-1 azoles or 1000 μg ml-1 strobilurins or SDHIs by strong up-regulation of genes encoding target enzymes (up to 660-fold), genes for putative efflux pumps and transporters (up to 230-fold) and xenobiotic detoxification enzymes (up to 200-fold). Comparison of gene expression in FocTR4 and Zymoseptoria tritici, grown under identical conditions, reveals that this response is only observed in FocTR4. In contrast, FocTR4 shows little innate resistance to most multi-site fungicides. However, quantitative virulence assays, in soil-grown bananas, reveals that only captan (20 μg ml-1) and all lipophilic cations (200 μg ml-1) suppress Panama disease effectively. These fungicides could help protect bananas from future yield losses by FocTR4.

Evaluation of 1,4-naphthoquinone derivatives as antibacterial agents: activity and mechanistic studies

The diverse and large-scale application of disinfectants posed potential health risks and caused ecological damage during the 2019-nCoV pandemic, thereby increasing the demands for the development of disinfectants based on natural products, with low health risks and low aquatic toxicity. In the present study, a few natural naphthoquinones and their derivatives bearing the 1,4-naphthoquinone skeleton were synthesized, and their antibacterial activity against selected bacterial strains was evaluated. In vitro antibacterial activities of the compounds were investigated against Escherichia coli and Staphylococcus aureus. Under the minimum inhibitory concentration (MIC) of ⩽ 0.125 µmol/L for juglone (1a), 5,8-dimethoxy-1,4-naphthoquinone (1f), and 7-methyl-5-acetoxy-1,4-naphthoquinone (3c), a strong antibacterial activity against S. aureus was observed. All 1,4-naphthoquinone derivatives exhibited a strong antibacterial activity, with MIC values ranging between 15.625 and 500 µmol/L and EC₅₀ values ranging between 10.56 and 248.42 µmol/L. Most of the synthesized compounds exhibited strong antibacterial activities against S. aureus. Among these compounds, juglone (1a) showed the strongest antibacterial activity. The results from mechanistic investigations indicated that juglone, a natural naphthoquinone, caused cell death by inducing reactive oxygen species production in bacterial cells, leading to DNA damage. In addition, juglone could reduce the self-repair ability of bacterial DNA by inhibiting RecA expression. In addition to having a potent antibacterial activity, juglone exhibited low cytotoxicity in cell-based investigations. In conclusion, juglone is a strong antibacterial agent with low toxicity, indicating that its application as a bactericidal agent may be associated with low health risks and aquatic toxicity.

ELECTRONIC SUPPLEMENTARY MATERIAL

Supplementary material is available in the online version of this article at 10.1007/s11783-023-1631-2 and is accessible for authorized users.

Cytogenotoxicity of fifth-generation quaternary ammonium using three plant bioindicators

The investigation aimed to determine the cytogenotoxic effect of fifth-generation quaternary ammonium using three plant species as bioindicators. Bulbs of A. cepa and seeds of L. culinaris and P. sativum were exposed to different concentrations of fifth-generation quaternary ammonium and a control solution of distilled water for 72 h. The results showed that the A. cepa bioindicator presented the greatest reduction in root length at 50 mg L^-1 and no mitotic index at 40 and 50 mg L^-1, reaching 100% mitotic inhibition. Cell abnormalities were present among the three bioindicator species, where the highest index of micronuclei occurred at 50 mg L^-1, being A. cepa the bioindicator with the highest relative rate of abnormality (25.28%). It was concluded that fifth-generation quaternary ammonium, in all treatments, caused a cytogenotoxic effect on the apical meristematic cells of the three species, A. cepa was the most sensitive species.

Didecyldimethylammonium Chloride- and Polyhexamethylene Guanidine-Resistant Bacteria Isolated from Fecal Sludge and Their Potential Use in Biological Products for the Detoxification of Biocide-Contaminated Wastewater Prior to Conventional Biological Treatment

Simple Summary

Every year, more than a million tons of fecal sludge (FS) containing biocides based on quaternary ammonium compounds and guanidine derivatives, which are widely used for FS deodorization and control of microbial activity, are generated in the environmentally safe toilet complexes of Russian Railways trains. Higher disposal costs for such biocide-contaminated FS due to activated sludge toxicity increases pressure on sanitary equipment servicing companies («Ecotol Service» LLC) to more efficiently discharge FS to wastewater treatment plants. In this work, we have developed a new environmentally friendly approach to reducing the toxicity of FS, based on the use of biological products from biocide-resistant bacterial strains isolated from FS. Our approach has proven to be effective in a series of FS biodegradation experiments, biological oxygen demand tests, and a newly developed disk-diffusion bioassay.

Abstract

Toxic shock caused by the discharge of biocide-contaminated fecal sludge (FS) from chemical toilets to conventional wastewater treatment plants (WWTP) can be a major problem in activated sludge operation. It is necessary to develop new environmental approaches to mitigate the toxicity of biocides in order to avoid degrading the performance of WWTP. “Latrina”, a chemical toilet additive containing didecyldimethylammonium chloride and polyhexamethylene guanidine, is widely used in environmentally safe toilet complexes (ESTC) on Russian railway trains to deodorize FS and control microbial activity. In this work, seven biocide-resistant bacterial strains were isolated and identified from the FS of ESTC. The values of the minimum inhibitory and bactericidal concentrations of biocides for the isolated strains were 4.5–10 times higher than for the collection microorganisms. The bacterium Alcaligenes faecalis DOS7 was found to be particularly resistant to “Latrina”, the minimum inhibitory concentration of which was almost 30 times higher than recommended for ESTC. Biological products based on isolated bacterial strains proved to be effective for FS biodegradation under both aerobic and anaerobic conditions. The results of the biochemical oxygen demand test and the newly developed disk-diffusion bioassay confirmed that isolated strains contribute to reducing toxicity of biocidal agents in FS. Hyper-resistance, non-pathogenicity, and potential plant growth-promoting ability make A. faecalis DOS7 promising for use in various biological products for wastewater treatment and bioremediation of soils contaminated with biocides, as well as in agriculture to increase plant productivity.

Effects of three surfactants on the degradation and environmental risk of metolachlor in aquatic environment

Surfactants and pesticides can be simultaneously detected in the environment by the reason of their widespread use and large amounts of emissions. Due to the special amphipathicity of surfactants, it may have special effects on the environmental behaviors and toxic effects of other substances in the environment. There are few relevant studies at present. In this study, the effects of three surfactants on the degradation of the amide pesticide metolachlor in water-sediment system were investigated. The study found that the three surfactants had no significant effect on the degradation of metolachlor in the system at environmental concentrations. However, at critical micelle concentration, cationic surfactant octadecyl trimethyl ammonium bromide and nonionic surfactant nonylphenol polyoxyethylene ether promoted the degradation of metolachlor in water-sediment system. Anionic surfactant odium dodecylbenzene sulfonate (SDBS) prolonged the degradation half-life of metolachlor. The presence of surfactants not only affected the environmental behavior of pesticides. When they coexisted with pesticides, the joint toxicity to aquatic organisms cannot be ignored. This study found that the combined effects of three surfactants and metolachlor on the acute developmental toxicity of zebrafish embryos were all synergistic effects. The combined effects of two ionic surfactants and metolachlor on the acute toxicity of adult zebrafish were synergistic effects. Further study showed that co-exposure of SDBS and metolachlor increased the absorption of metolachlor by zebrafish. Combined exposure of SDBS and metolachlor caused oxidative stress in brain, gill and liver of zebrafish. The results showed that the simultaneous presence of anionic surfactants and pesticides in the environment may increase the environmental risk of pesticides.

Silver nanoparticles coated medical fiber synthesized by surface engineering with bio-inspired mussel powered polydopamine: An investigated antimicrobial potential with bacterial membrane leakage reaction mechanism

Nature frequently provides narrative biological motivation. This study reports on oxygen-induced auto-polymerization of dopamine on the surface of medical cotton fibers to develop super-hydrophobic surfaces. The versatile reactivity of polydopamine (PDA) surfactant was adopted to deposit silver nanoparticles (Ag NPs) on the surface of medical cotton. SEM micrographs demonstrated the uniform deposition of Ag NPs. The antimicrobial reactivity confirmed the potential of Ag-loaded PDA-cotton fiber to hinder the growth of some tested pathogenic microbes. Silver-loaded PDA-cotton fibers showed the most promising zone of inhibition (ZOI) against (33.5 mm), Candida tropicalis (30.2 mm), and Aspergillus niger (30.2 mm). In growth curve assay, after addition of silver-loaded PDA-cotton fibers, the O.D. were lower (0.365 nm), showing the repression impact on S. aureus. It was observed that the quantity of cellular protein discharged from S. aureus is directly proportional to the concentration of silver-loaded PDA-cotton fibers and found to be 159.68 μg/ml after the treatment with silver-loaded PDA-cotton fibers (2 cm × 2 cm), which proves the antibacterial characteristics of the synthesied silver-loaded PDA-cotton fibers. The obtained antimicrobial results gives solution in treating pathogenic microbes and the application of silver-loaded PDA-cotton fibers as wound dressing in biomedical and pharmaceutical fields.

Adverse Outcome Pathway for Antimicrobial Quaternary Ammonium Compounds

Quaternary ammonium compounds (QACs) or quats are a large class of antimicrobial chemicals used in households and institutions as sanitizers and disinfectants. These chemicals are utilized as food processing sanitizers, algicides, in the process of water treatment, and preservatives in cosmetics. The aim of this study was to determine an Adverse Outcome Pathway (AOP) whereby two widely used QACs, alkyl dimethyl benzyl ammonium chloride (ADBAC) and didecyl dimethyl ammonium chloride (DDAC), may result in respiratory tract and gastrointestinal tract effects. When inhaled or ingested, these QACs are incorporated into the epithelial cell membrane at the point of contact. With sufficient dosage, the epithelial membrane is disrupted, reducing its fluidity, and releasing cellular contents. Further, ADBAC and DDAC might disrupt mitochondrial functions leading to decreased ATP production. Both events might lead to cell death, either attributed to direct lysis, necrosis, or apoptosis. Pro-inflammatory mediators are recruited to the tissue, inducing inflammation, edema, and excess mucus production. The primary tissue-level adverse outcome is epithelial degeneration and dysplasia. Most important, no apparent metabolism or distribution is involved in QAC action. Based upon this knowledge, it is suggested to replace default Uncertainty Factors for risk assessments with a set of Data Derived Extrapolation Factors.

Synthesis and characterization ofα-Fe2O3nanoparticles showing potential applications for sensing quaternary ammonium vapor at room temperature

P-type and n-type metal oxide semiconductors are widely used in the manufacture of gas sensing materials, due to their excellent electronic, electrical and electrocatalytic properties. Hematite (α-Fe₂O₃) compound has been reported as a promising material for sensing broad types of gases, due to its affordability, good stability and semiconducting properties. In the present work, the efficient and easy-to-implement sol-gel method has been used to synthesizeα-Fe₂O₃nanoparticles (NPs). The TGA-DSC characterizations of the precursor gel provided information about the phase transformation temperature and the mass percentage of the hematite NPs. X-ray diffraction, transmission electron microscopy and x-ray photoelectron spectroscopy data analyses indicated the formation of two iron oxide phases (hematite and magnetite) when the NPs are subjected to thermal treatment at 400 °C. Meanwhile, only the hematite phase was determined for thermal annealing above 500 °C up to 800 °C. Besides, the crystallite size shows an increasing trend with the thermal annealing and no defined morphology. A clear reduction of surface defects, associated with oxygen vacancies was also evidenced when the annealing temperature was increased, resulting in changes on the electrical properties of hematite NPs. Resistive gas-sensing tests were carried out using hematite NPs + glycerin paste, to detect quaternary ammonium compounds. Room-temperature high sensitivity values (S_r ∼ 4) have been obtained during the detection of ∼1 mM quaternary ammonium compounds vapor. The dependence of the sensitivity on the particle size, the mass ratio of NPs with respect to the organic ligand, changes in the dielectric properties, and the electrical conduction mechanism of gas sensing was discussed.

Oxidative Stress and Histopathological Changes in Gills and Kidneys of Cyprinus carpio following Exposure to Benzethonium Chloride, a Cationic Surfactant

One cationic surfactant with a wide spectrum of microbiocidal activity is benzethonium chloride (BEC). Despite being widely used, the toxicity data on vertebrate organisms are limited. Therefore, we aimed to evaluate within this study the acute toxicity of BEC on the gills and kidneys of Cyprinus carpio (European carp). An alteration of the antioxidant enzymes activities (glutathione reductase, glutathione peroxidase and glutathione S-transferase) was noticed after 96 h of exposure, along with an elevation of lipid peroxidation and decreased concentration of reduced glutathione, which confirmed that BEC was able to induce toxicity to these tissues. These metabolic effects were correlated with unspecific structural changes observed in gills and kidneys, having moderate degree of severity (such as an increase of melanomacrophages aggregation incidence and cytoplasm vacuolation of goblet cells in collecting tubules) and generally being compatible with life for the exposure time studied. The most severe structural effects were observed in gills after 96 h, noticing a lamellar aneurysm, hemorrhages and lamellar epithelium disruption due to the blood vessels and pillar cells damages and increased blood flow inside the lamellae. By our research we can confirm the utility of biochemical and histological analyses in the fish organs as tools for monitoring the water quality and ecotoxicological potential of chemicals.

Pulmonary inflammation and cellular responses following exposure to benzalkonium chloride: Potential impact of disrupted pulmonary surfactant homeostasis

Benzalkonium chloride (BKC) is a prototypical quaternary ammonium disinfectant. Previously, we suggested a no lethal dose level (0.005%) and an LD50 range (0.5-0.05%) of BKC following a single pharyngeal aspiration. Herein, we exposed BKC repeatedly by pharyngeal aspiration for 14 days (0.005 and 0.01%, female mice, total five times with interval of two days, 5 mice/group) and 28 days (0, 0.001, 0.005, and 0.01%, male and female mice, weekly, 16 mice/sex/group). Death following 14 days-repeated exposure did not occur. Meanwhile, chronic pathological lesions were observed in the lung tissues of mice exposed to BKC for 28 days. The total number of bronchial alveolar lavage cells increased, and pulmonary homeostasis of immunologic messenger molecules was disturbed. Following, we investigated BKC-induced cellular responses using human bronchial epithelial cells. The cytotoxicity increased rapidly with concentration. Lysosomal volume, NO production, and lipid peroxidation increased in BKC-treated cells, whereas intracellular ROS level decreased accompanying structural and functional damage of mitochondria. We also found that BKC affected the expression level of immune response, DNA damage, and amino acid biosynthesis-related molecules. More interestingly, lamellar body- and autophagosome-like structures were notably observed in cells exposed to BKC, and necrotic and apoptotic cell death were identified accompanying cell accumulation in the G2/M phase. Therefore, we suggest that repeated respiratory exposure of BKC causes pulmonary inflammation and lung tissue damage and that dead and damaged cells may contribute to the inflammatory response. In addition, the formation process of lamellar body-like structures may function as a key toxicity mechanism.

Molecular evidence for suppression of swimming behavior and reproduction in the estuarine rotifer Brachionus koreanus in response to COVID-19 disinfectants

The increased use of disinfectants due to the spread of the novel coronavirus infection (e.g. COVID-19) has caused burden in the environment but knowledge on its ecotoxicological impact on the estuary environment is limited. Here we report in vivo and molecular endpoints that we used to assess the effects of chloroxylenol (PCMX) and benzalkonium chloride (BAC), which are ingredients in liquid handwash, dish soap products, and sanitizers used by consumers and healthcare workers on the estuarine rotifer Brachionus koreanus. PCMX and BAC significantly affected the life table parameters of B. koreanus. These chemicals modulated the activities of antioxidant enzymes such as superoxide dismutase and catalase and increased reactive oxygen species even at low concentrations. Also, PCMX and BAC caused alterations in the swimming speed and rotation rate of B. koreanus. Furthermore, an RNA-seq-based ingenuity pathway analysis showed that PCMX affected several signaling pathways, allowing us to predict that a low concentration of PCMX will have deleterious effects on B. koreanus. The neurotoxic and mitochondrial dysfunction event scenario induced by PCMX reflects the underlying molecular mechanisms by which PCMX produces outcomes deleterious to aquatic organisms.

Engineered magnetic oxides nanoparticles as efficient sorbents for wastewater remediation: a review

The rapid urbanization and industrialization is causing worldwide water pollution, calling for advanced cleaning methods. For instance, pollutant adsorption on magnetic oxides is efficient and very practical due to the easy separation from solutions by an magnetic field. Here we review the synthesis and performance of magnetic oxides such as iron oxides, spinel ferrites, and perovskite oxides for water remediation. We present structural, optical, and magnetic properties. Magnetic oxides are also promising photocatalysts for the degradation of organic pollutants. Antimicrobial activities and adsorption of heavy metals and radionucleides are also discussed.

Gut Microbiota: A Key Regulator in the Effects of Environmental Hazards on Modulates Insulin Resistance

Insulin resistance is a hallmark of Alzheimer’s disease (AD), type II diabetes (T2D), and Parkinson’s disease (PD). Emerging evidence indicates that these disorders are typically characterized by alterations in the gut microbiota composition, diversity, and their metabolites. Currently, it is understood that environmental hazards including ionizing radiation, toxic heavy metals, pesticides, particle matter, and polycyclic aromatic hydrocarbons are capable of interacting with gut microbiota and have a non-beneficial health effect. Based on the current study, we propose the hypothesis of “gut microenvironment baseline drift”. According to this “baseline drift” theory, gut microbiota is a temporarily combined cluster of species sharing the same environmental stresses for a short period, which would change quickly under the influence of different environmental factors. This indicates that the microbial species in the gut do not have a long-term relationship; any split, division, or recombination may occur in different environments. Nonetheless, the “baseline drift” theory considers the critical role of the response of the whole gut microbiome. Undoubtedly, this hypothesis implies that the gut microbiota response is not merely a “cross junction” switch; in contrast, the human health or disease is a result of a rich palette of gut-microbiota-driven multiple-pathway responses. In summary, environmental factors, including hazardous and normal factors, are critical to the biological impact of the gut microbiota responses and the dual effect of the gut microbiota on the regulation of biological functions. Novel appreciation of the role of gut microbiota and environmental hazards in the insulin resistance would shed new light on insulin resistance and also promote the development of new research direction and new overcoming strategies for patients.

Combination of biodegradation and fenton process for efficient removal of PDM/ZnO

In the present study, an investigation was conducted on the removal of polydiallyldimethylammonium chloride-acrylic-acrylamide-hydroxyethyl acrylate/ZnO nanocomposites (PDM/ZnO) through biodegradation and Fenton process coupled treatments. As revealed from the results of the chemical oxygen demand, the total organic carbon, the biochemical oxygen demand and the CO₂ production analysis, PDM/ZnO could be partially biodegraded. The optimal initial pH, the mixed liquid suspended solids concentration and additional carbon source (glucose) dosage in the biodegradation were 7.0, 4.0 g/L and 1.0 g/L, respectively. On the whole, NaCl, the coexisted metal cations (Cu²⁺, Zn²⁺ and Cr³⁺) and additional NH₄Cl inhibited the biodegradation of PDM/ZnO. PDM/ZnO was suggested to adversely affect on microbial community structure and activity. Optimum conditions for Fenton treatment were 50 mg/L Fe²⁺, 20 mL/L H₂O₂ and pH 2.0. Biodegradation showed that 64% of PDM/ZnO was removed. Besides, the combination of Fenton post-treatment could achieve an over 97% removal of PDM/ZnO. Thus, Fenton process combined biodegradation pre-treatment can act as an effective method to remove PDM/ZnO.

Constructed wetlands for polishing oil and gas produced water releases

Produced water (PW) is the largest waste stream associated with oil and gas (O&G) operations and contains petroleum hydrocarbons, heavy metals, salts, naturally occurring radioactive materials and any remaining chemical additives. In some areas in Wyoming, constructed wetlands (CWs) are used to polish PW downstream of National Pollutant Discharge Elimination System (NPDES) PW release points. In recent years, there has been increased interest in finding lower cost options, such as CWs, for PW treatment. The goal of this study was to understand the efficacy of removal and environmental fate of O&G organic chemical additives in CW systems used to treat PW released for agricultural beneficial reuse. To achieve this goal, we analyzed water and sediment samples for organic O&G chemical additives and conducted 16S rRNA gene sequencing for microbial community characterization on three such systems in Wyoming, USA. Three surfactants (polyethylene glycols, polypropylene glycols, and nonylphenol ethoxylates) and one biocide (alkyldimethylammonium chloride) were detected in all three PW discharges and >94% removal of all species from PW was achieved after treatment in two CWs in series. These O&G extraction additives were detected in all sediment samples collected downstream of PW discharges. Chemical and microbial analyses indicated that sorption and biodegradation were the main attenuation mechanisms for these species. Additionally, all three discharges showed a trend of increasingly diverse, but similar, microbial communities with greater distance from NPDES PW discharge points. Results of this study can be used to inform design and management of constructed wetlands for produced water treatment.

Impacts of COVID-19 on the Aquatic Environment and Implications on Aquatic Food Production

The COVID-19 pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), resulted in ecological changes of aquatic ecosystems, affected the aquatic food supply chain, and disrupted the socio-economy of global populations. Due to reduced human activities during the pandemic, the aquatic environment was reported to improve its water quality, wild fishery stocks, and biodiversity. However, the sudden surge of plastics and biomedical wastes during the COVID-19 pandemic masked the positive impacts and increased the risks of aquatic pollution, especially microplastics, pharmaceuticals, and disinfectants. The transmission of SARS-CoV-2 from wastewater treatment plants to natural water bodies could have serious impacts on the environment and human health, especially in developing countries with poor waste treatment facilities. The presence and persistence of SARS-CoV-2 in human excreta, wastewaters, and sludge and its transmission to aquatic ecosystems could have negative impacts on fisheries and aquaculture industries, which have direct implications on food safety and security. COVID-19 pandemic-related environmental pollution showed a high risk to aquatic food security and human health. This paper reviews the impacts of COVID-19, both positive and negative, and assesses the causes and consequences of anthropogenic activities that can be managed through effective regulation and management of eco-resources for the revival of biodiversity, ecosystem health, and sustainable aquatic food production.

Quaternary ammonium compounds: perspectives on benefits, hazards, and risk

Quaternary ammonium compounds are antimicrobial chemicals that provide significant public health benefits by controlling bacteria and viruses that cause infections such as colds, flu, and COVID. The benefits of antimicrobial QACs are seen in increased quality-of-life measures, such as reduced time away from work and school and reduced medical costs. As active antimicrobial agents, QACs and QAC-containing consumer and professional products are highly regulated by authorities such as the US Environmental Protection Agency and the European Chemicals Agency. A complete database of guideline safety studies, covering human and environmental health, is available and has been reviewed by multiple regulatory agencies globally. The conclusions of regulatory agencies from these studies indicate no concerns regarding reproductive effects, genotoxicity, carcinogenicity, or other systemic adverse effects. In contrast, some published academic studies provide mixed findings on lipid synthesis, reproductive effects, and asthma. However, many of these studies have been found not to be robust in design and lacked appropriate controls to support conclusions of a clear and direct association with an adverse effect. The hazard data for the QACs show that their primary critical effects are point-of-contact effects such as irritation, which exhibit a threshold and occur in a dose–response manner. This review compares toxicity information for QACs, examines human exposures, and quantifies the risks estimated from QAC product use. QACs are an important cleaning and hygiene tool, and the abundance of safety data generated for them provides assurance they can be safely used in professional and household products.

Strategies toward development of antimicrobial biomaterials for dental healthcare applications

Several approaches for elimination of oral pathogens are being explored at the present time since oral diseases remain prevalent affecting approximately 3.5 billion people worldwide. Need for antimicrobial biomaterials in dental healthcare include but is not restricted to designing resin composites and adhesives for prevention of dental caries. Constant efforts are also being made to develop antimicrobial strategies for clearance of endodontic space prior root canal treatment and for treatment of periimplantitis and periodontitis. This article discusses various conventional and nanotechnology-based strategies to achieve antimicrobial efficacy in dental biomaterials. Recent developments in the design and synthesis of antimicrobial peptides and antifouling zwitterionic polymers to effectively lessen the risks of antimicrobial drug resistance are also outlined in this review. Further, the role of contemporary strategies such as use of smart biomaterials, ionic solvent-based biomaterials and quorum quenchers incorporated biomaterials in the elimination of dental pathogens are described in detail. Lastly, we mentioned the approach of using polymers to print custom-made three-dimensional antibacterial dental products via additive manufacturing technologies. This review provides a critical perspective on the chemical, biomimetic, and engineering strategies intended for developing antimicrobial biomaterials that have the potential to substantially improve the dental health.