Altered toxicological endpoints in humans from common quaternary ammonium compound disinfectant exposure

Quaternary ammonium biocides promote conjugative transfer of antibiotic resistance gene in structure- and species-dependent manner

The linkage between biocides and antibiotic resistance has been widely suggested in laboratories and various environments. However, the action mechanism of biocides on antibiotic resistance genes (ARGs) spread is still unclear. Thus, 6 quaternary ammonium biocides (QACs) with different bonded substituents or alkyl chain lengths were selected to assess their effects on the conjugation transfer of ARGs in this study. Two conjugation models with the same donor (E. coli DH5α (RP4)) into two receptors, E. coli MG1655 and pathogenic S. sonnei SE6-1, were constructed. All QACs were found to significantly promote intra- and inter-genus conjugative transfer of ARGs, and the frequency was highly impacted by their structure and receptors. At the same environmental exposure level (4 × 10-1 mg/L), didecyl dimethyl ammonium chloride (DDAC (C10)) promoted the most frequency of conjugative transfer, while benzathine chloride (BEC) promoted the least. With the same donor, the enhanced frequency of QACs of intra-transfer is higher than inter-transfer. Then, the acquisition mechanisms of two receptors were further determined using biochemical combined with transcriptome analysis. For the recipient E. coli, the promotion of the intragenus conjugative transfer may be associated with increased cell membrane permeability, reactive oxygen species (ROS) production and proton motive force (PMF)-induced enhancement of flagellar motility. Whereas, the increase of cell membrane permeability and decreased flagellar motility due to PMF disruption but encouraged biofilm formation, maybe the main reasons for promoting intergenus conjugative transfer in the recipient S. sonnei. As one pathogenic bacterium, S. sonnei was first found to acquire ARGs by biocide exposure.

Bioconcentration potential of ionic liquids: New data on membrane partitioning and its comparison with predictions obtained by COSMOmic

Ionic liquids (ILs) have recently gained significant attention in both the scientific community and industry, but there is a limited understanding of the potential risks they might pose to the environment and human health, including their potential to accumulate in organisms. While membrane and storage lipids have been considered as primary sorption phases driving bioaccumulation, in this study we used an in vitro tool known as solid-supported lipid membranes (SSLMs) to investigate the affinity of ILs to membrane lipid - phosphatidylcholine and compare the results with an existing in silico model. Our findings indicate that ILs may have a strong affinity for the lipids that form cell membranes, with the key factor being the length of the cation's side chain. For quaternary ammonium cations, increase in membrane affinity (logMA) was observed from 3.45 ± 0.06 at 10 carbon atoms in chain to 4.79 ± 0.06 at 14 carbon atoms. We also found that the anion can significantly affect the membrane partitioning of the cation, even though the anions themselves tend to have weaker interactions with phospholipids than the cations of ILs. For 1-methyl-3-octylimidazolium cation the presence of tricyanomethanide anion caused increase in logMA to 4.23 ± 0.06. Although some of our data proved to be consistent with predictions made by the COSMOmic model, there are also significant discrepancies. These results suggest that further research is needed to improve our understanding of the mechanisms and structure-activity relationships involved in ILs bioconcentration and to develop more accurate predictive models.

Oral Exposure to Benzalkonium Chlorides in Male and Female Mice Reveals Sex-Dependent Alteration of the Gut Microbiome and Bile Acid Profile

Benzalkonium chlorides (BACs) are commonly used disinfectants in a variety of consumer and food-processing settings, and the COVID-19 pandemic has led to increased usage of BACs. The prevalence of BACs raises the concern that BAC exposure could disrupt the gastrointestinal microbiota, thus interfering with the beneficial functions of the microbes. We hypothesize that BAC exposure can alter the gut microbiome diversity and composition, which will disrupt bile acid homeostasis along the gut-liver axis. In this study, male and female mice were exposed orally to d 7 -C12- and d 7 -C16-BACs at 120 µg/g/day for one week. UPLC-MS/MS analysis of liver, blood, and fecal samples of BAC-treated mice demonstrated the absorption and metabolism of BACs. Both parent BACs and their metabolites were detected in all exposed samples. Additionally, 16S rRNA sequencing was carried out on the bacterial DNA isolated from the cecum intestinal content. For female mice, and to a lesser extent in males, we found that treatment with either d 7 -C12- or d 7 -C16-BAC led to decreased alpha diversity and differential composition of gut bacteria with notably decreased actinobacteria phylum. Lastly, through a targeted bile acid quantitation analysis, we observed decreases in secondary bile acids in BAC-treated mice, which was more pronounced in the female mice. This finding is supported by decreases in bacteria known to metabolize primary bile acids into secondary bile acids, such as the families of Ruminococcaceae and Lachnospiraceae. Together, these data signify the potential impact of BACs on human health through disturbance of the gut microbiome and gut-liver interactions.

Development and Application of a Multidimensional Database for the Detection of Quaternary Ammonium Compounds and Their Phase I Hepatic Metabolites in Humans

The COVID-19 pandemic has led to significantly increased human exposure to the widely used disinfectants quaternary ammonium compounds (QACs). Xenobiotic metabolism serves a critical role in the clearance of environmental molecules, yet limited data are available on the routes of QAC metabolism or metabolite levels in humans. To address this gap and to advance QAC biomonitoring capabilities, we analyzed 19 commonly used QACs and their phase I metabolites by liquid chromatography-ion mobility-tandem mass spectrometry (LC-IM-MS/MS). In vitro generation of QAC metabolites by human liver microsomes produced a series of oxidized metabolites, with metabolism generally occurring on the alkyl chain group, as supported by MS/MS fragmentation. Discernible trends were observed in the gas-phase IM behavior of QAC metabolites, which, despite their increased mass, displayed smaller collision cross-section (CCS) values than those of their respective parent compounds. We then constructed a multidimensional reference SQLite database consisting of m/z, CCS, retention time (rt), and MS/MS spectra for 19 parent QACs and 81 QAC metabolites. Using this database, we confidently identified 13 parent QACs and 35 metabolites in de-identified human fecal samples. This is the first study to integrate in vitro metabolite biosynthesis with LC-IM-MS/MS for the simultaneous monitoring of parent QACs and their metabolites in humans.

Antimicrobial cetylpyridinium chloride causes functional inhibition of mitochondria as potently as canonical mitotoxicants, nanostructural disruption of mitochondria, and mitochondrial Ca2+ efflux in living rodent and primary human cells

People are exposed to high concentrations of antibacterial agent cetylpyridinium chloride (CPC) via food and personal care products, despite little published information regarding CPC effects on eukaryotes. Here, we show that low-micromolar CPC exposure, which does not cause cell death, inhibits mitochondrial ATP production in primary human keratinocytes, mouse NIH-3T3 fibroblasts, and rat RBL-2H3 immune mast cells. ATP inhibition via CPC (EC50 1.7 μM) is nearly as potent as that caused by canonical mitotoxicant CCCP (EC50 1.2 μM). CPC inhibition of oxygen consumption rate (OCR) tracks with that of ATP: OCR is halved due to 1.75 μM CPC in RBL-2H3 cells and 1.25 μM in primary human keratinocytes. Mitochondrial [Ca2+] changes can cause mitochondrial dysfunction. Here we show that CPC causes mitochondrial Ca2+ efflux from mast cells via an ATP-inhibition mechanism. Using super-resolution microscopy (fluorescence photoactivation localization) in live cells, we have discovered that CPC causes mitochondrial nanostructural defects in live cells within 60 min, including the formation of spherical structures with donut-like cross section. This work reveals CPC as a mitotoxicant despite widespread use, highlighting the importance of further research into its toxicological safety.

Chemical Inhibition of Sterol Biosynthesis

Cholesterol is an essential molecule of life, and its synthesis can be inhibited by both genetic and nongenetic mechanisms. Hundreds of chemicals that we are exposed to in our daily lives can alter sterol biosynthesis. These also encompass various classes of FDA-approved medications, including (but not limited to) commonly used antipsychotic, antidepressant, antifungal, and cardiovascular medications. These medications can interfere with various enzymes of the post-lanosterol biosynthetic pathway, giving rise to complex biochemical changes throughout the body. The consequences of these short- and long-term homeostatic disruptions are mostly unknown. We performed a comprehensive review of the literature and built a catalogue of chemical agents capable of inhibiting post-lanosterol biosynthesis. This process identified significant gaps in existing knowledge, which fall into two main areas: mechanisms by which sterol biosynthesis is altered and consequences that arise from the inhibitions of the different steps in the sterol biosynthesis pathway. The outcome of our review also reinforced that sterol inhibition is an often-overlooked mechanism that can result in adverse consequences and that there is a need to develop new safety guidelines for the use of (novel and already approved) medications with sterol biosynthesis inhibiting side effects, especially during pregnancy.

Interaction and Transport of Benzalkonium Chlorides by the Organic Cation and Multidrug and Toxin Extrusion Transporters

Humans are chronically exposed to benzalkonium chlorides (BACs) from environmental sources. The U.S. Food and Drug Administration (FDA) has recently called for additional BAC safety data, as these compounds are cytotoxic and have great potential for biochemical interactions. Biodistribution studies revealed that BACs extensively distribute to many tissues and accumulate at high levels, especially in the kidneys, but the underlying mechanisms are unclear. In this study, we characterized the interactions of BACs of varying alkyl chain length (C8 to C14) with the human organic cation transporters (hOCT1-3) and multidrug and toxin extrusion proteins (hMATE1/2K) with the goal to identify transporters that could be involved in BAC disposition. Using transporter-expressing cell lines, we showed that all BACs are inhibitors of hOCT1-3 and hMATE1/2K (IC50 ranging 0.83-25.8 μM). Further, the short-chain BACs (C8 and C10) were identified as substrates of these transporters. Interestingly, although BAC C8 displayed typical Michaelis-Menten kinetics, C10 demonstrated a more complex substrate-inhibition profile. Transwell studies with transfected Madin-Darby canine kidney cells revealed that intracellular accumulation of basally applied BAC C8 and C10 was substantially higher (8.2- and 3.7-fold, respectively) in hOCT2/hMATE1 double-transfected cells in comparison with vector-transfected cells, supporting a role of these transporters in mediating renal accumulation of these compounds in vivo. Together, our results suggest that BACs interact with hOCT1-3 and hMATE1/2K as both inhibitors and substrates and that these transporters may play important roles in tissue-specific accumulation and potential toxicity of short-chain BACs. Our findings have important implications for understanding human exposure and susceptibility to BACs due to environmental exposure. SIGNIFICANCE STATEMENT: Humans are systemically exposed to benzalkonium chlorides (BACs). These compounds broadly distribute through tissues, and their safety has been questioned by the FDA. Our results demonstrate that hOCT2 and hMATE1 contribute to the renal accumulation of BAC C8 and C10 and that hOCT1 and hOCT3 may be involved in the tissue distribution of these compounds. These findings can improve our understanding of BAC disposition and toxicology in humans, as their accumulation could lead to biochemical interactions and deleterious effects.

Photochemical fate of quaternary ammonium compounds (QACs) and degradation pathways predication through computational analysis

Quaternary ammonium compounds (QACs) are commonly used in many products, such as disinfectants, detergents and personal care products. However, their widespread use has led to their ubiquitous presence in the environment, posing a potential risk to human and environmental health. Several methods, including direct and indirect photodegradation, have been explored to remove QACs such as benzylalkyldimethyl ammonium compounds (BACs) and alkyltrimethyl ammonium compounds (ATMACs) from the environment. Hence, in this research, a systematic review of the literature was conducted using PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis) method to understand the fate of these QACs during direct and indirect photodegradation in UV/H2O2, UV/PS, UV/PS/Cu2+, UV/chlorine, VUV/UV/chlorine, O3/UV and UV/O3/TiO2 systems which produce highly reactive radicals that rapidly react with the QACs, leading to their degradation. As a result of photodegradation, several transformation products (TPs) of QACs are formed, which can pose a greater risk to the environment and human health than the parent QACs. Only limited research in this area has been conducted with fewer QACs. Hence, quantum mechanical calculations such as density functional theory (DFT)-based computational calculations using Gaussian09 software package were used here to explain better the photo-resistant nature of a specific type of QACs, such as BACs C12-18 and ATMACs C12, C14, C18, and their transformation pathways, providing insights into active sites participating in the phototransformation. Recognizing that different advanced oxidation processes (AOPs) come with pros and cons in the elimination of QACs, this review also highlighted the importance of implementing each AOP concerning the formation of toxic transformation products and electrical energy per order (EEO), especially when QACs coexist with other emerging contaminants (ECs).

Hygiene requirements for cleaning and disinfection of surfaces: recommendation of the Commission for Hospital Hygiene and Infection Prevention (KRINKO) at the Robert Koch Institute

This recommendation of the Commission for Hospital Hygiene and Infection Prevention (KRINKO) addresses not only hospitals, but also outpatient health care facilities and compiles current evidence. The following criteria are the basis for the indications for cleaning and disinfection: Infectious bioburden and tenacity of potential pathogens on surfaces and their transmission routes, influence of disinfecting surface cleaning on the rate of nosocomial infections, interruption of cross infections due to multidrug-resistant organisms, and outbreak control by disinfecting cleaning within bundles. The criteria for the selection of disinfectants are determined by the requirements for effectiveness, the efficacy spectrum, the compatibility for humans and the environment, as well as the risk potential for the development of tolerance and resistance. Detailed instructions on the organization and implementation of cleaning and disinfection measures, including structural and equipment requirements, serve as the basis for their implementation. Since the agents for surface disinfection and disinfecting surface cleaning have been classified as biocides in Europe since 2013, the regulatory consequences are explained. As possible addition to surface disinfection, probiotic cleaning, is pointed out. In an informative appendix (only in German), the pathogen characteristics for their acquisition of surfaces, such as tenacity, infectious dose and biofilm formation, and the toxicological and ecotoxicological characteristics of microbicidal agents as the basis for their selection are explained, and methods for the evaluation of the resulting quality of cleaning or disinfecting surface cleaning are presented.

Benzalkonium Chloride Poisoning in Pediatric Patients: Report of Case with a Severe Clinical Course and Literature Review

The use of disinfectants, particularly those containing quaternary ammonium compounds (QUACs), has dramatically escalated globally since the coronavirus disease 2019 pandemic. We report a case that highlights the risks associated with ingesting low-concentration QUAC solutions and emphasize the importance of effective management in resolving severe lesions without sequelae. A 17-month-old boy experienced severe respiratory failure after ingesting a disinfectant containing benzalkonium chloride (BAC). The child was initially treated at a local emergency department and was subsequently transferred to a pediatric poison center. Upon evaluation, the child was found to have grade III-A corrosive esophageal lesions and chemical pneumonitis. Several complications, including massive pneumothorax and candidemia, occurred during the clinical course of the disease. However, with timely medical intervention and appropriate supportive care, the patient completely recovered without any long-term sequelae. The properties of BAC and the comprehensive management approach may have been responsible for the patient's full recovery, despite the potentially life-threatening effects of ingesting disinfectants.

Potential of ionic liquids as emerging green solvent for the pretreatment of lignocellulosic biomass

Lignocellulosic biomass is available in abundance as a renewable resource, but the major portion of it is often discarded as waste without utilizing its immense potential as an alternative renewable energy resource. To overcome recalcitrance of lignocellulosic biomass, various pretreatment methods are applied to it, so that the complex and rigid polymeric structure can be broken down into fractions susceptible for enzymatic hydrolysis. Effective and efficient biomass processing is the goal of pretreatment methods, but none of the explored pretreatment methods are versatile enough to fulfil the requirement of biomass processing with greater flexibility in terms of operational cost and desired output efficiency. Deployment of green solvents such as ionic liquids for the pretreatment of lignocellulosic biomass has been a topic of discussion amongst the scientific community in recent times. The presented work provides a detailed overview on the deployment of ionic liquid for the pretreatment of lignocellulosic biomass coupled with a brief discussion on other pretreatments methods. The recyclability and reusability along with other unique properties makes an ionic liquid pretreatment different from the other traditional pretreatment methods. Also, this study explores diverse critical parameters that governs the dissolution process of biomass. Hazardous properties of ionic liquids have also been explored. Future perspective and recommendations have been given for an efficient, effective, and eco-friendly deployment of ionic liquid in biomass pretreatment process.

An exposure assessment of 27 quaternary ammonium compounds in pet dogs and cats from New York State, USA

Benzylalkyldimethylammonium (BACs), dialkyldimethylammonium (DDACs), and alkyltrimethylammonium compounds (ATMACs) are quaternary ammonium compounds (QACs) used widely as biocides, disinfectants, and sanitizers. Owing to their toxicity, human exposure to this class of chemicals is a concern. Pet animals are sentinels of human exposure to several indoor environmental chemicals. For the first time, we measured 7 BACs, 6 DDACs, 6 ATMACs, and 8 metabolites of BACs in urine and feces of pet dogs and cats from New York State, USA. We found widespread occurrence of QACs in feces, with median concentration of ∑All (sum concentration of all 27 QAC analytes) at 9680 and 1260 ng/g dry weight (dw) in dog and cat feces, respectively. BACs were the most abundant compounds among the four types of QACs, accounting for 64 % and 57 % of ∑All in dog and cat feces, respectively, followed by DDACs (33 % and 34 %, respectively), ATMACs (4 % and 9 %, respectively), and BAC metabolites (0.2 % and 0.3 %, respectively). However, in urine, only ω-carboxylic acid metabolites of BACs were found at median concentrations at 2.08 and 0.28 ng/mL in dogs and cats, respectively. Samples collected from animal shelters contained elevated levels of QACs than those from homes of pet owners. A significant positive correlation was found among the four types of QACs analyzed, which suggested usage of these chemicals in combination as mixtures. Based on the concentrations measured in feces, and through a reverse dosimetry approach, the median cumulative daily intakes (CDIs) of QACs were estimated to be 49.4 and 4.75 µg/kg body weight (BW)/day for dogs and cats, respectively. This study provides first evidence that pet dogs and cats are exposed to QACs at significant levels that warrant further attention.

Evaluation of the Antitumor Activity of Quaternary Ammonium Surfactants

Quaternary ammonium surfactants, due to their diverse chemical structure and their biological properties, can be used in medicine as DNA carriers, disinfectants, and antimicrobial and antitumor agents. In this study, using melanoma A375, colon adenocarcinoma HT-29 and normal human dermal fibroblast (NHDF) cells, we tested the hypothesis that the quaternary ammonium surfactants 2-dodecanoyloxyethyl)trimethylammonium bromide (DMM-11), 2-dodecanoyloxypropyl)trimethylammonium bromide (DMPM-11) and 2-pentadecanoyloxymethyl)trimethylammonium bromide (DMGM-14) act selectively against cancer cells. The results showed that these compounds led to the initiation of the apoptotic process of programmed cell death, as evidenced by the ratio of the relative expression of Bax protein to Bcl-2. The encapsulation of surfactants in liposomes allowed lower concentrations to be used. Moreover, encapsulation reduced their toxicity towards non-cancerous cells. The anticancer efficiency and apoptotic effect of the liposomal formulations with surfactants (DMM-11, DMPM-11 and DMGM-14) were higher than those of surfactant-free liposomes. Therefore, quaternary ammonium surfactant-loaded liposomes show significant potential as delivery vehicles for the treatment of melanoma and colon cancers. The use of nano-formulations offers the advantage of optimizing quaternary ammonium surfactant delivery for improved anticancer therapy.

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.

From disinfectants to antibiotics: Enhanced biosafety of quaternary ammonium compounds by chemical modification

The excessive use of quaternary ammonium compounds (QACs) following the COVID-19 pandemic has raised substantial concerns regarding their biosafety. Overuse of QACs has been associated with chronic biological adverse effects, including genotoxicity or carcinogenicity. In particular, inadvertent intravascular administration or oral ingestion of QACs can lead to fatal acute toxicity. To enhance the biosafety and antimicrobial efficacy of QACs, this study reports a new series of QACs, termed as PACs, with the alkyl chain of benzalkonium substituted by a phthalocyanine moiety. Firstly, the rigid phthalocyanine moiety enhances the selectivity of QACs to bacteria over human cells and reduces alkyl chain's entropic penalty of binding to bacterial membranes. Furthermore, phthalocyanine neutralizes hemolysis and cytotoxicity of QACs by binding with albumin in plasma. Our experimental results demonstrate that PACs inherit the optical properties of phthalocyanine and validate the broad-spectrum antibacterial activity of PACs in vitro. Moreover, the intravascular administration of the most potent PAC, PAC1a, significantly reduced bacterial burden and ameliorated inflammation level in a bacteria-induced septic mouse model. This study presents a new strategy to improve the antimicrobial efficacy and biosafety of QACs, thus expanding their range of applications to the treatment of systemic infections.

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.

Pharmaceutical agent cetylpyridinium chloride inhibits immune mast cell function by interfering with calcium mobilization

Cetylpyridinium chloride (CPC) is an antimicrobial used in numerous personal care and janitorial products and food for human consumption at millimolar concentrations. Minimal information exists on the eukaryotic toxicology of CPC. We have investigated the effects of CPC on signal transduction of the immune cell type mast cells. Here, we show that CPC inhibits the mast cell function degranulation with antigen dose-dependence and at non-cytotoxic doses ∼1000-fold lower than concentrations in consumer products. Previously we showed that CPC disrupts phosphatidylinositol 4,5-bisphosphate, a signaling lipid critical for store-operated Ca2+ entry (SOCE), which mediates degranulation. Our results indicate that CPC inhibits antigen-stimulated SOCE: CPC restricts Ca2+ efflux from endoplasmic reticulum, reduces Ca2+ uptake into mitochondria, and dampens Ca2+ flow through plasma membrane channels. While inhibition of Ca2+ channel function can be caused by alteration of plasma membrane potential (PMP) and cytosolic pH, CPC does not affect PMP or pH. Inhibition of SOCE is known to depress microtubule polymerization, and here we show that CPC indeed dose-dependently shuts down formation of microtubule tracks. In vitro data reveal that CPC inhibition of microtubules is not due to direct CPC interference with tubulin. In summary, CPC is a signaling toxicant that targets Ca2+ mobilization.

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.

Identification and characterization of quaternary ammonium compounds in Flemish indoor dust by ion-mobility high-resolution mass spectrometry

Quaternary ammonium compounds (QACs) are a class of surfactants commonly used in disinfecting and cleaning products. Their use has substantially increased during the COVID-19 pandemic leading to increasing human exposure. QACs have been associated with hypersensitivity reactions and an increased risk of asthma. This study introduces the first identification, characterization and semi-quantification of QACs in European indoor dust using ion-mobility high-resolution mass spectrometry (IM-HRMS), including the acquisition of collision cross section values (^DTCCS_N2) for targeted and suspect QACs. A total of 46 indoor dust samples collected in Belgium were analyzed using target and suspect screening. Targeted QACs (n = 21) were detected with detection frequencies ranging between 4.2 and 100 %, while 15 QACs showed detection frequencies > 90 %. Semi-quantified concentrations of individual QACs showed a maximum of 32.23 µg/g with a median ∑QAC concentration of 13.05 µg/g and allowed the calculation of Estimated Daily Intakes for adults and toddlers. Most abundant QACs matched the patterns reported in indoor dust collected in the United States. Suspect screening allowed the identification of 17 additional QACs. A dialkyl dimethyl ammonium compound with mixed chain lengths (C16:C18) was characterized as a major QAC homologue with a maximum semi-quantified concentration of 24.90 µg/g. The high detection frequencies and structural variabilities observed call for more European studies on potential human exposure to these compounds. For all targeted QACs, drift tube IM-HRMS derived collision cross section values (^DTCCS_N2) are reported. Reference ^DTCCS_N2 values allowed the characterization of CCS-m/z trendlines for each of the targeted QAC classes. Experimental CCS-m/z ratios of suspect QACs were compared with the CCS-m/z trendlines. The alignment between the two datasets served as an additional confirmation of the assigned suspect QACs. The use of the 4bit multiplexing acquisition mode with consecutive high-resolution demultiplexing confirmed the presence of isomers for two of the suspect QACs.

Pharmaceutical agent cetylpyridinium chloride inhibits immune mast cell function by interfering with calcium mobilization

Cetylpyridinium chloride (CPC) is an antimicrobial used in numerous personal care and janitorial products and food for human consumption at millimolar concentrations. Minimal information exists on the eukaryotic toxicology of CPC. We have investigated the effects of CPC on signal transduction of the immune cell type mast cells. Here, we show that CPC inhibits the mast cell function degranulation with antigen dose-dependence and at non-cytotoxic doses ∼1000-fold lower than concentrations in consumer products. Previously we showed that CPC disrupts phosphatidylinositol 4,5-bisphosphate, a signaling lipid critical for store-operated Ca 2+ entry (SOCE), which mediates degranulation. Our results indicate that CPC inhibits antigen-stimulated SOCE: CPC restricts Ca 2+ efflux from endoplasmic reticulum, reduces Ca 2+ uptake into mitochondria, and dampens Ca 2+ flow through plasma membrane channels. While inhibition of Ca 2+ channel function can be caused by alteration of plasma membrane potential (PMP) and cytosolic pH, CPC does not affect PMP or pH. Inhibition of SOCE is known to depress microtubule polymerization, and here we show that CPC indeed dose-dependently shuts down formation of microtubule tracks. In vitro data reveal that CPC inhibition of microtubules is not due to direct CPC interference with tubulin. In summary, CPC is a signaling toxicant that targets Ca 2+ mobilization.

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.

Cytotoxicity and Microbiological Properties of Copolymers Comprising Quaternary Ammonium Urethane-Dimethacrylates with Bisphenol A Glycerolate Dimethacrylate and Triethylene Glycol Dimethacrylate

Using dental composite restorative materials with a copolymeric matrix chemically modified towards bioactive properties can help fight secondary caries. In this study, copolymers of 40 wt.% bisphenol A glycerolate dimethacrylate, 40 wt.% quaternary ammonium urethane-dimethacrylates (QAUDMA-m, where m represents 8, 10, 12, 14, 16 and 18 carbon atoms in the N-alkyl substituent), and 20 wt.% triethylene glycol dimethacrylate (BG:QAm:TEGs) were tested for (i) cytotoxicity on the L929 mouse fibroblast cell line; (ii) fungal adhesion, fungal growth inhibition zone, and fungicidal activity against C. albicans; and (iii) bactericidal activity against S. aureus and E. coli. BG:QAm:TEGs had no cytotoxic effects on L929 mouse fibroblasts because the reduction of cell viability was less than 30% compared to the control. BG:QAm:TEGs also showed antifungal activity. The number of fungal colonies on their surfaces depended on the water contact angle (WCA). The higher the WCA, the greater the scale of fungal adhesion. The fungal growth inhibition zone depended on the concentration of QA groups (x_QA). The lower the x_QA, the lower the inhibition zone. In addition, 25 mg/mL BG:QAm:TEGs suspensions in culture media showed fungicidal and bactericidal effects. In conclusion, BG:QAm:TEGs can be recognized as antimicrobial biomaterials with negligible biological patient risk.

Environmental factors and their impact on the COVID-19 pandemic

The coronavirus disease 2019 (COVID-19) pandemic has resulted in numerous cases of illness and death worldwide. Research has shown that there are associations between transmission, as well as the severity of SARS-CoV‑2 (severe acute respiratory syndrome coronavirus 2) infections, and various environmental factors. For example, air pollution with particulate matter is thought to play a crucial role, and both climatic and geographical aspects must be considered. Furthermore, environmental conditions such as industry and urban lifestyle have a significant impact on air quality and thus on health aspects of the population. In this regard, other factors such as chemicals, microplastics, and diet also critically impact health, including respiratory and cardiovascular diseases. Overall, the COVID-19 pandemic has highlighted how closely health and the environment are linked. This review discusses the impact of environmental factors on the COVID-19 pandemic.

Quaternary ammonium disinfectants and antiseptics: tolerance, resistance and potential impact on antibiotic resistance

BACKGROUND

Due to the substantial increase in the use of disinfectants containing quaternary ammonion compounds (QACs) in healthcare and community settings during the COVID-19 pandemic, there is increased concern that heavy use might cause bacteria to develop resistance to QACs or contribute to antibiotic resistance. The purpose of this review is to briefly discuss the mechanisms of QAC tolerance and resistance, laboratory-based evidence of tolerance and resistance, their occurrence in healthcare and other real-world settings, and the possible impact of QAC use on antibiotic resistance.

METHODS

A literature search was conducted using the PubMed database. The search was limited to English language articles dealing with tolerance or resistance to QACs present in disinfectants or antiseptics, and potential impact on antibiotic resistance. The review covered the period from 2000 to mid-Jan 2023.

RESULTS

Mechanisms of QAC tolerance or resistance include innate bacterial cell wall structure, changes in cell membrane structure and function, efflux pumps, biofilm formation, and QAC degradation. In vitro studies have helped elucidate how bacteria can develop tolerance or resistance to QACs and antibiotics. While relatively uncommon, multiple episodes of contaminated in-use disinfectants and antiseptics, which are often due to inappropriate use of products, have caused outbreaks of healthcare-associated infections. Several studies have identified a correlation between benzalkonium chloride (BAC) tolerance and clinically-defined antibiotic resistance. The occurrence of mobile genetic determinants carrying multiple genes that encode for QAC or antibiotic tolerance raises the concern that widespread QAC use might facilitate the emergence of antibiotic resistance. Despite some evidence from laboratory-based studies, there is insufficient evidence in real-world settings to conclude that frequent use of QAC disinfectants and antiseptics has promoted widespread emergence of antibiotic resistance.

CONCLUSIONS

Laboratory studies have identified multiple mechanisms by which bacteria can develop tolerance or resistance to QACs and antibiotics. De novo development of tolerance or resistance in real-world settings is uncommon. Increased attention to proper use of disinfectants is needed to prevent contamination of QAC disinfectants. Additional research is needed to answer many questions and concerns related to use of QAC disinfectants and their potential impact on antibiotic resistance.

Quaternary ammonium compounds of emerging concern: Classification, occurrence, fate, toxicity and antimicrobial resistance

Amplified hygiene and precautionary measures are of utmost importance to control the spread of COVID-19 and future infection; however, these changes in practice are projected to trigger a rise in the purchase, utilisation and hence, discharge of many disinfectants into the environment. While alcohol-based, hydrogen peroxide-based, and chlorine-based compounds have been used widely, quaternary ammonium compounds (QACs) based disinfectants are of significant concern due to their overuse during this pandemic. This review presents the classification of disinfectants and their mechanism of action, focusing on QACs. Most importantly, the occurrence, fate, toxicity and antimicrobial resistance due to QACs are covered in this paper. Here we collated evidence from multiple studies and found rising trends of concern, including an increase in the mass load of QACs at a wastewater treatment plant (WWTP) by 331% compared to before the COVID-19 pandemic, as well as an increases in the concentration of 62% in residential dust, resulting in high concentrations of QACs in human blood and breast milk and suggesting that these could be potential sources of persistent QACs in infants. In addition to increased toxicity to human and aquatic life, increased use of QACs and accelerated use of antibiotics and antimicrobials during the COVID-19 pandemic could multiply the threat to antimicrobial resistance.

[Simultaneous determination of seven quaternary ammonium compounds in frozen food by ultra performance liquid chromatography-tandem mass spectrometry combined with modified QuEChERS method]

Quaternary ammonium compounds (QACs) are a class of cationic surfactants that can be used as the main active ingredient of disinfectants. The increased use of QACs is concerning as exposure from inhalation or ingestion to these compounds that has been associated with adverse effects on the reproductive and respiratory systems. Humans are exposed to QACs primarily by food consumption and inhalation of air. QAC residues pose significant threats to public health. Given the importance of assessing potential residue levels for QACs in food, therefore, a method was developed for the simultaneous detection of six common QACs and one emerging QAC (Ephemora) in frozen food by ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) coupled with the modified QuEChERS method. The main factors governing the response, recovery, and sensitivity of the method, including extraction solvents, types and dosages of adsorbents, apparatus conditions, and mobile phases, were optimized in the course of sample pretreatment and instrument analysis. QAC residues in frozen food were extracted using 20 mL methanol-water (90∶10, containing 0.5% formic acid) for 20 min by the vortex shock method. The mixture was ultrasonicated for 10 min and centrifuged at 10000 r/min for 10 min. A 1-mL aliquot of the supernatant was transferred to a new tube and purified using 100 mg of PSA adsorbents. After mixing and centrifugation at 10000 r/min for 5 min, the purified solution was analyzed. Target analytes were separated on an ACQUITY UPLC BEH C8 chromatographic column (50 mm×2.1 mm, 1.7 μm) at a column temperature of 40 ℃ and a flow rate of 0.3 mL/min. The injection volume was 1 μL. Gradient elution was performed using methanol and 5 mmol/L ammonium acetate solution as the mobile phases. Multiple reaction monitoring (MRM) was conducted in the positive electrospray ionization (ESI+) mode. The matrix-matched external standard method was used to quantify seven QACs. The optimized chromatography-based method completely separated the seven analytes. Good linear relationships were obtained for the seven QACs in the range of 0.1-100.0 ng/mL. The correlation coefficient (r2) ranged from 0.9971 to 0.9983. The limits of detection and limits of quantification ranged from 0.5 to 1.0 μg/kg and 1.5 to 3.0 μg/kg, respectively. Accuracy and precision were determined by spiking salmon and chicken samples with 3.0, 10.0, and 100.0 μg/kg of analytes, in compliance with the current legislation, with six replicates per determination. The average recoveries of the seven QACs ranged from 65.4% to 101%. The relative standard deviations (RSDs) were between 0.64% and 16.8%. Matrix effects of the analytes were between -27.5% and 33.4% in salmon and chicken samples after purifying using PSA. The developed method was applied to the determination of seven QACs in rural samples. QACs were detected in only one sample; the level did not exceed European Food Safety Authority specified residue limit standards. The detection method has high sensitivity, good selectivity and stability, and the results are accurate and reliable. It is suitable for the simultaneous rapid determination of seven QAC residues in frozen food. The results provide valuable information for future risk assessment studies targeting this class of compounds.

The spread of different resistance genes fractions in nitrification system under chronic exposure to varying alkyl chain length benzalkyl dimethylammonium compounds

Benzalkyl dimethylammonium compounds (BACs) are generally applied as surfactants and disinfectants. In this study, the nitrification systems were exposed to different alkyl chain lengths (C12-C16) and different levels of BACs (0-5 mg/L), respectively, totally 120 days and to explore the chronic effect of BACs on resistance genes (RGs). RGs were classified into four fractions based on activated sludge properties. Ammonia oxidation performance were not significantly affected by BACs, whereas BACs increased the absolute abundance of most intracellular RGs in sludge (si-RGs). Under the exposure of BACs, extracellular RGs in water (we-RGs) showed a decrease trend and si-RGs tended to be converted to we-RGs. Tightly bound-Tyrosine side chain was significantly correlated with most we-RGs, and we-intI1 might contribute to the propagation of RGs. Therefore, the risk of transmission of different fractions of RGs in the nitrification system under the stress of BACs should be taken seriously.

Widespread occurrence of quaternary alkylammonium disinfectants in soils of Hesse, Germany

Quaternary alkylammonium compounds (QAACs) are cationic organic compounds with amphiphilic properties that are widely used as surfactants and disinfectants in industry, households and agriculture. Several studies suggest that QAACs co-select for antibiotic resistant microorganisms and thus may contribute to the spread of antibiotic resistance in the environment. Data on QAAC occurrence in soil are scarce and limited to soils that are prone to direct exposure to QAACs. Therefore, we conducted a comprehensive study on the occurrence of QAACs in soils of Hesse, a federal state in Germany, covering an area of 21,115 km². Sixty-five soil samples that comprised different land uses (arable, grassland, forest, vineyard) and area types (rural, agglomeration) were analysed for concentrations of alkyltrimethylammonium (ATMACs, with alkyl chain lengths C8-C16), benzylalkyldimethylammonium (BACs, C8-C18) and dialkyldimethylammonium compounds (DADMACs, C8-C18) via HPLC-MS/MS after ultrasonic-assisted extraction with acidified acetonitrile. QAACs were detected in 97 % of the soil samples irrespective of land use and area type. The most abundant QAAC homologues were DADMACs > BACs > ATMACs. The highest total QAAC concentrations were detected in alluvial soils influenced by the deposition of suspended particles during flood events, with DADMAC-C16 and -C18 as the dominant homologues. The high abundance of long-chain DADMACs suggests that legacy pollution and accumulation govern QAAC concentrations in soils. The presence of QAACs in forest soils points to a potential input via atmospheric deposition. Our work highlights the widespread occurrence of QAACs in soils of Hesse and the need for more research on their entry paths and fate in the soil ecosystem.

LC-MS/MS methods for the determination of 30 quaternary ammonium compounds including benzalkonium and paraquat in human serum and urine

Benzalkyldimethylammonium (or benzalkonium; BACs), alkyltrimethylammonium (ATMACs), and dialkyldimethylammonium compounds (DDACs) have been widely used for over six decades as disinfectants, especially during the COVID-19 pandemic. Here we describe methods for the determination of 7 BACs, 6 ATMACs, 6 DDACs, 8 BAC metabolites, and the structurally similar quaternary ammonium compound (QAC) herbicides diquat, paraquat, and difenzoquat in human serum and urine using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The methods were optimized using isotopically labelled internal standards and solid-phase extraction with weak cation-exchange cartridges. We separated diquat and paraquat chromatographically using a mixed-mode LC column, and BACs, ATMACs, DDACs, difenzoquat, and BAC metabolites using reversed-phase (C8 and C18) LC columns. Method limits of detection (MLODs) and quantification (MLOQs) were 0.002-0.42 and 0.006-1.40 ng/mL, respectively. Recoveries of all analytes fortified at 1, 5, and 20 ng/mL concentrations in serum and urine matrices were 61-129%, with standard deviations of 0-20%. Repeated analysis of similarly fortified serum and urine samples yielded intra-day and inter-day variations of 0.22-17.4% and 0.35-17.3%, respectively. Matrix effects for analytes spiked into serum and urine matrices ranged from -27% to 15.4%. Analysis of real urine and serum samples revealed the presence of several QACs in human serum. Although no parent BACs were found in urine, we detected, for the first time, several ω-hydroxy and ω-carboxylic acid metabolites of BACs at average concentrations in the range of 0.05-0.35 ng/mL. The developed method is suitable for application in large-scale biomonitoring of human exposure to QACs and their metabolites in human serum and urine.

A new class of quaternary ammonium compounds as potent and environmental friendly disinfectants

Quaternary ammonium compounds (QACs) are inexpensive and readily available disinfectants, and have been widely used, especially since the COVID-19 outbreak. The toxicity of QACs to humans has raised increasing concerns in recent years. Here, a new type of QACs was synthesized by replacing the alkyl chain with zinc phthalocyanine (ZnPc), which consists of a large aromatic ring and is hydrophobic in nature, similar to the alkyl chain of QACs. Three ZnPc-containing disinfectants were synthesized and fully characterized. These compounds showed 15-16 fold higher antimicrobial effect against Gram-negative bacteria than the well-known QACs with half-maximal inhibitory (IC₅₀) values of 1.43 μM, 2.70 μM, and 1.31 μM, respectively. With the assistance of 680 nm light, compounds 4 and 6 had much higher bactericidal toxicities at nanomolar concentrations. Compound 6 had a bactericidal efficacy of close to 6 logs (99.9999% kill rate) at 1 μM to Gram-positive bacteria, including MRSA, under light illumination. Besides, these compounds were safe for mammalian cells. In a mouse model, compound 6 was effective in healing wound infection. Importantly, compound 6 was easily degraded at working concentrations under sunlight illumination, and is environmentally friendly. Thus, compound 6 is a novel and promising disinfectant.

Bacteriophage-based decontamination to control environmental colonization by Staphylococcus capitis in neonatal intensive care units: An in vitro proof-of-concept

Introduction

In neonatal intensive care units (NICUs), the standard chemical-based disinfection procedures do not allow a complete eradication of pathogens from environmental surfaces. In particular, the clone Staphylococcus capitis NRCS-A, a significant pathogen in neonates, was shown to colonize neonatal incubators. The aim of this study was to evaluate the in vitro effect of a bacteriophage cocktail on NRCS-A eradication.

Methods

Three bacteriophages were isolated, genetically characterized and assessed for their host range using a collection of representative clinical strains (n=31) belonging to the clone NRCS-A. The efficacy of a cocktail including these three bacteriophages to eradicate the reference strain S. capitis NRCS-A CR01 was determined in comparison or in combination with the chemical disinfectant Surfanios Premium on either dry inoculum or biofilm-embedded bacteria. The emergence of bacterial resistance against the bacteriophages alone or in cocktail was evaluated by growth kinetics.

Results

The three bacteriophages belonged to two families and genera, namely Herelleviridae/Kayvirus for V1SC01 and V1SC04 and Rountreeviridae/Andhravirus for V1SC05. They were active against 17, 25 and 16 of the 31 tested strains respectively. Bacteriophage cocktails decreased the bacterial inoculum of both dry spots and biofilms, with a dose dependent effect. The sequential treatment with bacteriophages then Surfanios Premium did not show enhanced efficacy. No bacterial resistance was observed when using the bacteriophage cocktail.

Discussion

This study established a proof-of-concept for the use of bacteriophages to fight against S. capitis NRCS-A. Further investigations are needed using a larger bacterial collection and in real-life conditions before being able to use such technology in NICUs

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.

Ionic liquids as potentially hazardous pollutants: Evidences of their presence in the environment and recent analytical developments

Ionic liquids (ILs) are considered to be very promising group of chemicals and the number of their potential applications is growing rapidly. However, while these compounds were originally proposed as a green alternative to classical solvents, there are certain doubts as to whether this classification is correct. Although in recent years there have been first reports published proving the presence of some ILs in the environment and even in human blood, at this point the scale of this possible problem is not yet fully understood. However, there is no doubt that as the number of ILs applications increases, analytical capabilities for rapid detection of possible environmental contamination should be also considered. Therefore, in this review paper, recent evidences for the ILs environmental contamination as well as analytical achievements related to the extraction of ILs from various environmental matrices have been summarized and important gaps and future perspectives have been pointed out. Based on the presented data it might be concluded that there is the urgent need for further development towards risk assessment of these potential environmental contaminants.

The first detection of quaternary ammonium compounds in breast milk: Implications for early-life exposure

BACKGROUND

Quaternary ammonium compounds (QACs), commonly used in cleaning, disinfecting, and personal care products, have recently gained worldwide attention due to the massive use of disinfectants during the COVID-19 pandemic. However, despite extensive use of these chemicals, no studies have focused on the analysis of QACs in human milk, a major route of exposure for infants.

OBJECTIVE

Our objectives were to identify and measure QACs in breast milk and evaluate early-life exposure to this group of compounds for nursing infants.

METHODS

Eighteen QACs, including 6 benzylalkyldimethyl ammonium compounds (BACs, with alkyl chain lengths of C8-C18), 6 dialkyldimethyl ammonium compounds (DDACs, C8-C18), and 6 alkyltrimethyl ammonium compounds (ATMACs, C8-C18), were measured in breast milk samples collected from U.S. mothers. Daily lactational intake was estimated based on the determined concentrations for 0-12 month old nursing infants.

RESULTS

Thirteen of the 18 QACs were detected in breast milk and 7 of them were found in more than half of the samples. The total QAC concentrations (ΣQAC) ranged from 0.33 to 7.4 ng/mL (median 1.5 ng/mL). The most abundant QAC was C14-BAC with a median concentration of 0.45 ng/mL. The highest median ΣQAC estimated daily intake (EDI) was determined for <1-month old infants based on the average (using the median concentration) and high (using the 95th percentile concentration) exposure scenarios (230 and 750 ng/kg body weight/day, respectively).

SIGNIFICANCE

Our findings provide the first evidence of the detection of several QACs in breast milk and identify breastfeeding as an exposure pathway to QACs for nursing infants.

IMPACT STATEMENT

Our findings provide the first evidence of QAC occurrence in breast milk and identify breastfeeding as one of the exposure pathways to QACs for nursing infants.

In Situ Application of Anti-Fouling Solutions on a Mosaic of the Archaeological Park of Ostia Antica

Biodegradation is among the most common issues affecting Cultural Heritage stone materials in outdoor environments. In recent years, the application of chemical agents with biocidal activity has been the most usual practice when dealing with biofilm removal. In outdoor environments, the use of these biocides is not effective enough, since the materials are constantly exposed to environmental agents and atmospheric pollutants. Thus, it becomes necessary to protect the surface of Cultural Heritage works with antimicrobial coatings to either prevent or at least limit future colonization. In this study, innovative biocides-both natural and synthetic-were applied on a Roman mosaic located in the Archaeological Park of Ostia Antica to compare their effectiveness in removing the biological degradation affecting it. In addition, an antimicrobial coating called "SI-QUAT" was applied and analyzed in situ. SI-QUAT has recently entered the market for its prevention activity against biocolonization. The biocidal activity of these products was tested and monitored using different analytical portable instruments, such as the multispectral system, the spectrocolorimeter, and the bioluminometer. The analyses showed that promising results can be obtained using the combination of the biocide and the protective effect of Preventol^® RI50 and SI-QUAT.

In vitro neurotoxicity evaluation of biocidal disinfectants in a human neuron-astrocyte co-culture model

Biocidal disinfectants (BDs) that kill microorganisms or pathogens are widely used in hospitals and other healthcare fields. Recently, the use of BDs has rapidly increased as personal hygiene has become more apparent owing to the pandemic, namely the coronavirus outbreak. Despite frequent exposure to BDs, toxicity data of their potential neurotoxicity (NT) are lacking. In this study, a human-derived SH-SY5Y/astrocyte was used as a co-culture model to evaluate the chemical effects of BDs. Automated high-content screening was used to evaluate the potential NT of BDs through neurite growth analysis. A set of 12 BD substances classified from previous reports were tested. Our study confirms the potential NT of benzalkonium chloride (BKC) and provides the first evidence of the potential NT of poly(hexamethylenebicyanoguanide-hexamethylenediamine) hydrochloride (PHMB). BKC and PHMB showed significant NT at concentrations without cytotoxicity. This test system for analyzing the potential NT of BDs may be useful in early screening studies for NT prior to starting in vivo studies.

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.

Fates of quaternary ammonium compound resistance genes and the corresponding resistant strain in partial nitrification/anammox system under pressure of hexadecyl trimethyl ammonium chloride

Hexadecyl trimethyl ammonium chloride (ATMAC-C16) is a kind of quaternary ammonium compound (QACs) which is extensively consumed as disinfectants, antimicrobials and surfactants. Here, the partial nitrification/anammox (PN/A) system was exposed to different levels of ATMAC-C16 (0-10 mg/L) and the main objective was to reveal the long-term microbiological responses of PN/A system to ATMAC-C16, importantly, explore the tolerance of PN/A to ATMAC-C16 and the key resistant strain. Nitrogen removal efficiency was influenced by environmental and extreme levels of ATMAC-C16 through mainly affecting the anammox (hzsB) gene. Two types of anammox, Candidatus Jettenia and Candidatus Kuenenia, were enriched under the pressure of ATMAC-C16, which allowed PN/A system to maintain good nitrogen removal performance. ATMAC-C16 might cause the hormesis of entire microbial population in PN/A system, leading to the enhancement of cell viability. ATMAC-C16 decreased the relative abundances of most antibiotics resistance genes (ARGs) but significantly enriched QACs resistance genes (QRGs). The tolerance of PN/A system to ATMAC-C16 might be strengthened by inducing the efflux pumps encoding genes (qacH-01/02). Microbial hosts dynamic and co-selection mechanism among ARGs and QRGs resulted in the opposite trends of qacEdeltal-01/02 and qacH-01/02. Pseudoxanthomonas mexicana was identified as the ATMAC-C16 resistant strain, and its resistance to 10 mg/L ATMAC-C16 might not only obtain by capturing the qacH gene, but also benefit from its own efflux pump system. Therefore, from the perspective of the transmission of resistance genes, especially for QRGs, the spread risk of QRGs and ATMAC-C16 resistant strain in PN/A technique should be taken seriously.

In-Situ Comparative Study of Eucalyptus, Basil, Cloves, Thyme, Pine Tree, and Tea Tree Essential Oil Biocide Efficacy

Bio-colonization is a dynamic and multiphasic process headed by microorganisms. Conventional treatments to process affected stone materials include chemical biocides, whose formulations are mainly composed of quaternary ammonium salts(QAs), reported to be toxic for human health, dangerous for the environment, and not biodegradable. Accordingly, novel green and eco-friendly products are a promising alternative to treat stone materials deteriorated by microorganism colonization. In this study, the efficacy of pure essential oils (EOs) and a mix of EOs was assessed in situ and compared to a conventional biocide based on QAs, and two commercially green products based on EOs, which were taken as references, through application on a mosaic located at the Archaeological Park of Ostia Antica (Rome). The EO biocide efficacy was analyzed by ultraviolet induced luminescence, spectro-colorimetry and bio-luminometry analyses while the possibility of their permanence on simulated substrate was studied by FTIR spectroscopy. It was observed by FTIR analysis, that EOs considered volatile can leave a residue after the application; typical fingerprint bands at about 2926, 1510, and 1455 cm⁻¹ were recorded in the EO spectra. Every tested oil was confirmed to have a biocide action although minimal in relation to the most conventional products based on QAs. The synergy of the essential oils revealed positive results, showing a stronger biocide efficacy. Further investigation should be carried out to develop the method of application and study of essential oils on cultural heritage.

A microfluidic system for viability determination of microalgae upon disinfectant treatment under continuous flow

The extensive use of quaternary ammonium compounds (QACs) has raised concerns regarding their environmental fate and potential risks to the ecosystem. As sensitive pollution indicators, green microalgae could readily monitor the aquatic toxicity of QACs as reflective of the changes in cell viability. Recent microfluidic-based systems have been designed for environmental biomonitoring and ecotoxicity studies while overall information of cell viability cannot be directly visualized under flowing conditions. In the present study, we developed a multifunctional microfluidic platform with the integration of analytical techniques including laser speckle contrast imaging and fluorescence spectroscopy for monitoring algal activity in response to QAC treatment. The biocidal efficiency of a representative QAC benzalkonium bromide (BAB) on a typical aquatic algae Chlorella vulgaris was determined by collecting the bio-speckles and chlorophyll autofluorescence in real-time, where dose-dependent and time-dependent decrease of algal growth was found with the increase of BAB concentration and interaction time. The integrated system was capable of rapid detection of the aquatic toxicity of QACs along with macroscopical visualization of algal activities under flowing conditions in time-course, which could be extended to future implementation for broad ecotoxicity analysis of versatile environmental samples.

Cetylpyridinium chloride inhibits human breast tumor cells growth in a no-selective way

OBJECTIVE

Analyze the antitumor capacity of cetylpyridinium chloride (CPC) on human breast tumor cells, and the possible action mechanism.

MATERIAL AND METHODS

The human breast tumor cells MCF-7 and no-tumor breast cells MCF-10A were exposed to CPC under various condition (concentration and duration). Cell viability was measured with MTT assay, the LIVE/DEAD assay, and fluorescence microscopy. Membrane permeability after CPC exposure was evaluated by Calcein AM assay, mitochondrial morphology with a MitoView staining, and genotoxicity with the comet assay and fluorescence microscopy.

RESULTS

CPC was cytotoxic to both MCF-7 and MCF-10A as of a 24-h exposure to 0.1 µM. Cytotoxicity was dose-dependent and reached 91% for MCF-7 and 78% for MCF-10A after a 24-h exposure to 100 µM CPC, which outperformed the positive control doxorubicin in effectiveness and selectivity. The LD50 of CPC on was 6 µM for MCF-7 and 8 µM for MCF-10A, yielding a selectivity index of 1.41. A time response analysis revealed 64% dead cells after only 5 min of exposure to 100 µM CPC. With respect to the action mechanisms, the comet assay did not reveal genome fragmentation. On the other hand, membrane damage was dose-dependent and may also affect mitochondrial morphology.

CONCLUSION

Cetylpyridinium chloride inhibits MCF-7 cell growing in a non-selective way as of 5 min of exposure. The action mechanism of CPC on tumor cells involves cell membrane damage without change neither mitochondrial morphology nor genotoxicity.

Genotoxic effect of microplastics and COVID-19: The hidden threat

Microplastics (MPs) are ubiquitous anthropogenic contaminants, and their abundance in the entire ecosystem raises the question of how far is the impact of these MPs on the biota, humans, and the environment. Recent research has overemphasized the occurrence, characterization, and direct toxicity of MPs; however, determining and understanding their genotoxic effect is still limited. Thus, the present review addresses the genotoxic potential of these emerging contaminants in aquatic organisms and in human peripheral lymphocytes and identified the research gaps in this area. Several genotoxic endpoints were implicated, including the frequency of micronuclei (MN), nucleoplasmic bridge (NPB), nuclear buds (NBUD), DNA strand breaks, and the percentage of DNA in the tail (%Tail DNA). In addition, the mechanism of MPs-induced genotoxicity seems to be closely associated with reactive oxygen species (ROS) production, inflammatory responses, and DNA repair interference. However, the gathered information urges the need for more studies that present environmentally relevant conditions. Taken into consideration, the lifestyle changes within the COVID-19 pandemic, we discussed the impact of the pandemic on enhancing the genotoxic potential of MPs whether through increasing human exposure to MPs via inappropriate disposal and overconsumption of plastic-based products or by disrupting the defense system owing to unhealthy food and sleep deprivation as well as stress. Overall, this review provided a reference for the genotoxic effect of MPs, their mechanism of action, as well as the contribution of COVID-19 to increase the genotoxic risk of MPs.

Disinfectant-induced hormesis: An unknown environmental threat of the application of disinfectants to prevent SARS-CoV-2 infection during the COVID-19 pandemic?

Massive additional quantities of disinfectants have been applied during the COVID-19 pandemic as infection preventive and control measures. While the application of disinfectants plays a key role in preventing the spread of SARS-CoV-2 infection, the effects of disinfectants applied during the ongoing pandemic on non-target organisms remain unknown. Here we collated evidence from multiple studies showing that chemicals used for major disinfectant products can induce hormesis in various organisms, such as plants, animal cells, and microorganisms, when applied singly or in mixtures, suggesting potential ecological risks at sub-threshold doses that are normally considered safe. Among other effects, sub-threshold doses of disinfectant chemicals can enhance the proliferation and pathogenicity of pathogenic microbes, enhancing the development and spread of drug resistance. We opine that hormesis should be considered when evaluating the effects and risks of such disinfectants, especially since the linear-no-threshold (LNT) and threshold dose-response models cannot identify or predict their effects.

Quaternary Ammonium Compounds: Bioaccumulation Potentials in Humans and Levels in Blood before and during the Covid-19 Pandemic

Quaternary ammonium compounds (QACs) are commonly used in a variety of consumer, pharmaceutical, and medical products. In this study, bioaccumulation potentials of 18 QACs with alkyl chain lengths of C8-C18 were determined in the in vitro-in vivo extrapolation (IVIVE) model using the results of human hepatic metabolism and serum protein binding experiments. The slowest in vivo clearance rates were estimated for C12-QACs, suggesting that these compounds may preferentially build up in blood. The bioaccumulation of QACs was further confirmed by the analysis of human blood (sera) samples (n = 222). Fifteen out of the 18 targeted QACs were detected in blood with the ΣQAC concentrations reaching up to 68.6 ng/mL. The blood samples were collected during two distinct time periods: before the outbreak of the COVID-19 pandemic (2019; n = 111) and during the pandemic (2020, n = 111). The ΣQAC concentrations were significantly higher in samples collected during the pandemic (median 6.04 ng/mL) than in those collected before (median 3.41 ng/mL). This is the first comprehensive study on the bioaccumulation and biomonitoring of the three major QAC groups and our results provide valuable information for future epidemiological, toxicological, and risk assessment studies targeting these chemicals.

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.

Biological removal of benzalkonium chlorides from wastewater by immobilized cells of Pseudomonas sp. BIOMIG1 in an up-flow packed bed reactor

Quaternary ammonium compounds (QACs) are active ingredients of many disinfectants used against SARS-CoV-2 to control the transmission of the virus through human-contact surfaces. As a result, QAC consumption has increased more than twice during the pandemic. Consequently, the concentration of QACs in wastewater and receiving environments may increase. Due to their antimicrobial activity, high levels of QACs in wastewater may cause malfunctioning of biological treatment systems resulting in inadequate treatment of wastewater. In this study, a biocatalyst was produced by entrapping Pseudomonas sp. BIOMIG1 capable of degrading QACs in calcium alginate. Bioactive 3-mm alginate beads degraded benzalkonium chlorides (BACs), a group of QACs, with a rate of 0.47 µM-BACs/h in shake flasks. A bench-scale continuous up-flow reactor packed with BIOMIG1-beads was operated over one and a half months with either synthetic wastewater or secondary effluent containing 2-20 µM BACs at an empty bed contact time (EBCT) ranging between 0.6 and 4.7 h. Almost complete BAC removal was achieved from synthetic and real wastewater at and above 1.2 h EBCT without aeration and effluent recirculation. The microbial community in beads dominantly composed of BIOMIG1 with trace number of Achromobacter spp. after the operation of the reactor with the real wastewater, suggesting that BIOMIG1 over-competed native wastewater bacteria during the operation. This reactor system offers a low cost and robust treatment of QACs in wastewater. It can be integrated to conventional treatment systems for efficient removal of QACs from the wastewater, especially during the pandemic period.