Exposure to common quaternary ammonium disinfectants decreases fertility in mice

Benzalkonium chloride induces hematopoietic stem cell reduction and immunotoxicity in zebrafish larvae

Benzalkonium chloride (BAC) is a broad-spectrum antibacterial agent that possesses cleaning and bactericidal properties, but impact of BAC on wellbeing of aquatic organisms remains uncertain. Consequently, in this current study, we have examined the immunotoxic potential of BAC in zebrafish embryos, thus marking it as the pioneering effort in this field. According to the findings, zebrafish embryos exposed to BAC exhibited a decline in yolk area that varied with the concentration, along with a significant decrease in the count of neutrophils, macrophages, red blood cells, and thymus T-cells. We observed significantly up-regulated expression of immune-related signaling genes such as cxcl-c1c, il-8, tir4 and inf-γ, but expression of nf-κb was downregulated. In addition, we observed a marked reduction in the number of hematopoietic stem cells in zebrafish larvae after BAC exposure, which could be the result of oxidative stress-mediated apoptosis. We found that compared with the control group, the number of red blood cells in juvenile zebrafish in BAC-exposure group was significantly down-regulated, which could be attributed to hematopoietic stem cell defect. Astaxanthin restored immune cells and hematopoietic stem cells after BAC exposure, whereas Inhibitor of Wnt Response-1(IWR-1) restored neutrophils after BAC exposure. The research findings demonstrated that exposure to BAC displayed harmful effects on the development and immune system of zebrafish embryos. These effects might be associated with alterations in reactive oxygen species(ROS) levels and activation of the Wnt signaling pathway caused by BAC.

Reproductive & Developmental Toxicity of quaternary ammonium compounds

Quaternary ammonium compounds (QACs) are a class of chemicals commonly used as disinfectants in household and healthcare settings. Their usage has significantly increased in recent years due to the COVID-19 pandemic. In addition, QACs have replaced the recently banned disinfectants triclosan and triclocarban in consumer products. QACs are found in daily antimicrobial and personal care products such as household disinfectants, mouthwash, and hair care products. Due to the pervasiveness of QACs in daily use products, humans are constantly exposed. However, little is known about the health effects of everyday QAC exposure, particularly effects on human reproduction and development. Studies that investigate the harmful effects of QACs on reproduction are largely limited to high-dose studies, which may not be predictive of low dose, daily exposure, especially as QACs may be endocrine disrupting chemicals. This review analyzes recent studies on QAC effects on reproductive health, identifying knowledge gaps, and recommending future directions in QAC-related research.

Salinity-mediated enhancement of quaternary ammonium compounds resistance and removal in endophytic bacteria LSE01

The widespread usage of quaternary ammonium compounds (QACs) as disinfectants during the COVID-19 pandemic poses significant environmental risks, such as toxicity to organisms and the emergence of superbugs. In this study, different inorganic salts (NaCl, KCl, CaCl2, MgCl2) were used to induce endophytes LSE01 isolated from hyperaccumulating plants. After five generations of cultivation under 80 g/L NaCl, the minimum inhibitory concentration (MIC) of LSE01 to QACs increased by about 3-fold, while its degradation extent increased from 8% to 84% for C12BDMA-Cl and 5%-89% for C14BDMA-Cl. Transmission electron microscopy (TEM) and three-dimensional fluorescence spectra indicated that the cells induced by high concentration of salt caused plasmolysis and secreted more bound extracellular polymeric substances (B-EPS); these changes are likely to be an important reason for the observed increased resistance and enhanced degradation extent of LSE01 to QACs. Our findings suggest that salt-induction could be an effective way to enhance the resistance and removal of toxic organic pollutants by functional microorganisms.

Screening and characterization of 133 physiologically-relevant environmental chemicals for reproductive toxicity

Reproduction is a functional outcome that relies on complex cellular, tissue, and organ interactions that span the developmental period to adulthood. Thus, the assessment of its disruption by environmental chemicals would benefit significantly from scalable and innovative approaches to testing using functionally comparable reproductive models such as the nematode C. elegans. We adapted a previously described low-throughput in vivo chromosome segregation assay using C. elegans predictive of reproductive toxicity and leveraged available public data sources (ToxCast, ICE) to screen and characterize 133 physiologically-relevant chemicals in a high-throughput manner. The screening outcome was further validated in a second, independent in vivo assay assessing embryonic viability. In total, 13 chemicals were classified as reproductive toxicants with the two most active chemicals belonging to the large family of Quaternary Ammonium Compounds (QACs) commonly used as disinfectants but with limited available reproductive toxicity data. We compared the results from the C. elegans assay with ToxCast in vitro data compiled from 700+ cell response assays and 300+ signaling pathways-based assays. We did not observe a difference in the bioactivity or in the average potency (AC50) between the top and bottom chemicals. However, the intended target categories were significantly different between the classified chemicals with, in particular, an over-representation of steroid hormone targets for the high Z-score chemicals. Taken together, these results point to the value of in vivo models that scale to high-throughput level for reproductive toxicity assessment and to the need to prioritize the assessment of QACs impacts on reproduction.

Tetraalkylammonium salts (TAS) in solar energy applications - A review on in vitro and in vivo toxicity

Tetraalkylammonium salt (TAS) is an organic salt widely employed as a precursor, additive or electrolyte in solar cell applications, such as perovskite or dye-sensitized solar cells. Notably, Perovskite solar cells (PSCs) have garnered acclaim for their exceptional efficiency. However, PSCs have been associated with environmental and health concerns due to the presence of lead (Pb) content, the use of hazardous solvents, and the incorporation of TAS in their fabrication processes, which significantly contributes to environmental and human health toxicity. As a response, there is a growing trend towards transitioning to safer and biobased materials in PSC fabrication to address these concerns. However, the potential health hazards associated with TAS necessitate a thorough evaluation, considering the widespread use of this substance. Nevertheless, the overexploitation of TAS could potentially increase the disposal of TAS in the ecosystem, thus, posing a major health risk and severe pollution. Therefore, this review article presents a comprehensive discussion on the in vitro and in vivo toxicity assays of TAS as a potential material in solar energy applications, including cytotoxicity, genotoxicity, in vivo dermal, and systemic toxicity. In addition, this review emphasizes the toxicity of TAS compounds, particularly the linear tetraalkyl chain structures, and summarizes essential findings from past studies as a point of reference for the development of non-toxic and environmentally friendly TAS derivatives in future studies. The effects of the TAS alkyl chain length, polar head and hydrophobicity, cation and anion, and other properties are also included in this review.

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.

Screening and characterization of 133 physiologically-relevant environmental chemicals for reproductive toxicity

Reproduction is a functional outcome that relies on complex cellular, tissue, and organ interactions that span the developmental period to adulthood. Thus, the assessment of its disruption by environmental chemicals is remarkably painstaking in conventional toxicological animal models and does not scale up to the number of chemicals present in our environment and requiring testing. We adapted a previously described low-throughput in vivo chromosome segregation assay using C. elegans predictive of reproductive toxicity and leveraged available public data sources (ToxCast, ICE) to screen and characterize 133 physiologically-relevant chemicals in a high-throughput manner. The screening outcome was further validated in a second, independent in vivo assay assessing embryonic viability. In total, 13 chemicals were classified as reproductive toxicants with the two most active chemicals belonging to the large family of Quaternary Ammonium Compounds (QACs) commonly used as disinfectants but with limited available reproductive toxicity data. We compared the results from the C. elegans assay with ToxCast in vitro data compiled from 700+ cell response assays and 300+ signaling pathways-based assays. We did not observe a difference in the bioactivity or in average potency (AC50) between the top and bottom chemicals. However, the intended target categories were significantly different between the classified chemicals with, in particular, an over-representation of steroid hormone targets for the high Z-score chemicals. Taken together, these results point to the value of in vivo models that scale to high-throughput level for reproductive toxicity assessment and to the need to prioritize the assessment of QACs impacts on reproduction.

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.

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.

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.

High-Resolution Mass Spectrometry Screening of Quaternary Ammonium Compounds (QACs) in Dust from Homes and Various Microenvironments in South China

Despite their ubiquitous use, information regarding the presence of quaternary ammonium compounds (QACs) in various microenvironments remains scarce and only a small subset of QACs has been monitored using targeted chemical analysis. In this study, a total of 111 dust samples were collected from homes and various public settings in South China during the COVID-19 pandemic and were analyzed for traditional and emerging QACs using high-resolution mass spectrometry. The total traditional QAC concentrations in residential dust (∑traditional QAC, sum of 18 traditional QACs) ranged from 13.8 to 150 μg/g with a median concentration of 42.2 μg/g. Twenty-eight emerging QACs were identified in these samples, and the composition of ∑emerging QAC (sum of emerging QACs) to ∑QAC (sum of traditional and emerging QACs) ranged from 19 to 42% across various microenvironments, indicating the widespread existence of emerging QACs in indoor environments. Additionally, dust samples from cinemas exhibited higher ∑QAC concentrations compared to homes (medians 65.9 μg/g vs 58.3 μg/g, respectively), indicating heavier emission sources of QACs in these places. Interestingly, significantly higher ∑QAC concentrations were observed in dust from the rooms with carpets than those without (medians 65.6 μg/g vs 32.6 μg/g, p < 0.05, respectively). Overall, this study sheds light on the ubiquitous occurrence of QACs in indoor environments in South China.

Advancing Antimicrobial Textiles: A Comprehensive Study on Combating ESKAPE Pathogens and Ensuring User Safety

Antibiotic-resistant bacteria, ESKAPE pathogens, present a significant and alarming threat to public health and healthcare systems. This study addresses the urgent need to combat antimicrobial resistance by exploring alternative ways to reduce the health and cost implications of infections caused by these pathogens. To disrupt their transmission, integrating antimicrobial textiles into personal protective equipment (PPE) is an encouraging avenue. Nevertheless, ensuring the effectiveness and safety of these textiles remains a persistent challenge. To achieve this, we conduct a comprehensive study that systematically compares the effectiveness and potential toxicity of five commonly used antimicrobial agents. To guide decision making, a MULTIMOORA method is employed to select and rank the optimal antimicrobial textile finishes. Through this approach, we determine that silver nitrate is the most suitable choice, while a methoxy-terminated quaternary ammonium compound is deemed less favorable in meeting the desired criteria. The findings of this study offer valuable insights and guidelines for the development of antimicrobial textiles that effectively address the requirements of effectiveness, safety, and durability. Implementing these research outcomes within the textile industry can significantly enhance protection against microbial infections, contribute to the improvement of public health, and mitigate the spread of infectious diseases.

A Review of the Effects of Some Extrinsic Factors on Mice Used in Research

Animals have been used in research for over 2,000 y. From very crude experiments conducted by ancient scholars, animal research, as a science, was refined over hundreds of years to what we know it as today. However, the housing conditions of animals used for research did not improve significantly until less than 100 years ago when guidelines for housing research animals were first published. In addition, it was not until relatively recently that some extrinsic factors were recognized as a research variable, even when animals were housed under recommended guidelines. For example, temperature, humidity, light, noise, vibration, diet, water, caging, bedding, etc., can all potentially affect research using mice, contributing the inability of others to reproduce published findings. Consequently, these external factors should be carefully considered in the design, planning, and execution of animal experiments. In addition, as recommended by others, the housing and husbandry conditions of the animals should be described in detail in publications resulting from animal research to improve study reproducibility. Here, we briefly review some common, and less common, external factors that affect research in one of the most popular animal models, the mouse.

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.

Bioaccumulation and in vivo fate of toxic benzylalkyldimethylammonium chloride in rats via the radiotracer analysis

Benzylalkyldimethylammonium chloride (BAC), a quaternary ammonium compound (QAC), is utilized in industrial and biomedical applications for antimicrobial purposes. Since the coronavirus disease (COVID-19) outbreak, various types of BAC-containing household chemicals have been produced. BACs have several adverse effects; however, their biological uptake, translocation, and excretion in animal models (essential for better understanding in vivo behavior and toxicological impact) remain unclear. In this study, we performed the first biodistribution and whole-body imaging studies of BAC in male Sprague Dawley rats, using two different administration routes. Quantitative whole-body autoradiography (QWBA) data obtained for intranasal 14C-labeled BAC ([14C]C12-BAC) exposure showed substantial uptake values for the respiratory organs (e.g. 346 ng g-1 of lung at 3 h post administration) and the radiotracer was transported to other internal organs. The amount of radiotracer in the heart, adrenal gland, and pancreas were 198, 1410, and 186 ng g-1 tissue respectively at 168 h following exposure. Autoradiograms obtained after intravenous injection also showed high accumulation and slow excretion in these organs. The cumulative excretion analysis revealed that approximately 6.4% of the administered radioactivity remained in rats after a week. The results indicated that continuous inhalation exposure to BAC leads to potential toxic effects in extrapulmonary organs and the respiratory tract. Thus, the radiolabeling method utilized may help assess various synthetic QACs in living subjects.

Maternal exposure to cetylpyridinium chloride impairs oogenesis by causing mitochondria disorder in neonates

Cetylpyridinium Chloride (CPC) is a common disinfectant with potential mitochondrial toxicity. However, the effects of CPC on female reproduction remains unclear. In the present study, pregnant mice were exposed to environmentally relevant doses of CPC for 3 days, the effects were evaluated in the female offspring. Maternal exposure to CPC caused loss of oocytes in neonatal ovaries. TEM analysis of neonatal ovaries showed CPC caused aberrant mitochondrial morphology including vacuolated and disorganized structure, reduced functional cristae. In addition, CPC decreased mitochondrial membrane potential in neonatal oocytes. Seahorse analysis showed that CPC hampered mitochondrial reserve, manifested as reduced spare respiratory capacity. Furthermore, CPC damaged mitochondrial function and impaired developmental competence of MII oocytes, suggesting a persisting impact into adulthood. In summary, this is the first known demonstration that maternal exposure to CPC caused mitochondrial disorders in neonatal ovaries and had long-term effects on fertility of the female offspring.

Bedding as a variable affecting fasting blood glucose and vascular physiology in mice

Rodent husbandry requires careful consideration of environmental factors that may impact colony performance and subsequent physiological studies. Of note, recent reports have suggested corncob bedding may affect a broad range of organ systems. As corncob bedding may contain digestible hemicelluloses, trace sugars, and fiber, we hypothesized that corncob bedding impacts overnight fasting blood glucose and murine vascular function. Here, we compared mice housed on corncob bedding, which were then fasted overnight on either corncob or ALPHA-dri bedding, a virgin paper pulp cellulose alternative. Male and female mice were used from two noninduced, endothelial-specific conditional knockout strains [Cadherin 5-cre/ERT2, floxed hemoglobin-α1 (Hba1fl/fl) or Cadherin 5-cre/ERT2, floxed cytochrome-B5 reductase 3 (CyB5R3fl/fl)] on a C57BL/6J genetic background. After fasting overnight, initial fasting blood glucose was measured, and mice were anesthetized with isoflurane for measurement of blood perfusion via laser speckle contrast analysis using a PeriMed PeriCam PSI NR system. After a 15-min equilibration, the mice were injected intraperitoneally with the α1-adrenergic receptor agonist, phenylephrine (5 mg/kg), or saline, and monitored for changes in blood perfusion. After a 15-min response period, blood glucose was remeasured postprocedure. In both strains, mice fasted on corncob bedding had higher blood glucose than the pulp cellulose group. In the CyB5R3fl/fl strain, mice housed on corncob bedding displayed a significant reduction in phenylephrine-mediated change in perfusion. In the Hba1fl/fl strain, phenylephrine-induced change in perfusion was not different in the corncob group. This work suggests that corncob bedding, in part due to its ingestion by mice, could impact vascular measurements and fasting blood glucose. To promote scientific rigor and improve reproducibility, bedding type should be routinely included in published methods.NEW & NOTEWORTHY This study demonstrates real-time measurement of changes in perfusion to pharmacological treatment using laser speckle contrast analysis. Furthermore, this investigation revealed that fasting mice overnight on corncob bedding has differential effects on vascular function and that there was increased fasting blood glucose in mice fasted on corncob bedding compared with paper pulp cellulose bedding. This highlights the impact that bedding type can have on outcomes in vascular and metabolic research and reinforces the need for thorough and robust reporting of animal husbandry practices.

Further Study of the Polar Group's Influence on the Antibacterial Activity of the 3-Substituted Quinuclidine Salts with Long Alkyl Chains

Quaternary ammonium compounds (QACs) are among the most potent antimicrobial agents increasingly used by humans as disinfectants, antiseptics, surfactants, and biological dyes. As reports of bacterial co- and cross-resistance to QACs and their toxicity have emerged in recent years, new attempts are being made to develop soft QACs by introducing hydrolyzable groups that allow their controlled degradation. However, the development of such compounds has been hindered by the structural features that affect the bioactivity of QACs, one of them being polarity of the substituent near the quaternary center. To further investigate the influence of the polar group on the bioactivity of QACs, we synthesized 3-aminoquinuclidine salts for comparison with their structural analogues, 3-acetamidoquinuclidines. We found that the less polar amino-substituted compounds exhibited improved antibacterial activity over their more polar amide analogues. In addition to their better minimum inhibitory concentrations, the candidates were excellent at suppressing Staphylococcus aureus biofilm formation and killing bacteria almost immediately, as shown by the flow cytometry measurements. In addition, two candidates, namely QNH2-C14 and QNH2-C16, effectively suppressed bacterial growth even at concentrations below the MIC. QNH2-C14 was particularly effective at subinhibitory concentrations, inhibiting bacterial growth for up to 6 h. In addition, we found that the compounds targeted the bacterial membrane, leading to its perforation and subsequent cell death. Their low toxicity to human cells and low potential to develop bacterial resistance suggest that these compounds could serve as a basis for the development of new QACs.

In vitro evaluation for estrogenic mechanisms of the disinfectant benzalkonium chloride as an emerging contaminant

This study aimed to evaluate in vitro the possible mechanisms underlying the estrogenic potential of benzalkonium chloride (BAC) as a disinfectant emerging contaminant. Effects of BAC at the environmentally-relevant concentrations on estrogen synthesis and estrogen receptor (ER) signaling were assessed using the H295R steroidogenesis assay and the MCF-7 proliferation assay, respectively. Results showed that exposure to BAC at concentrations of 1.0-1.5 mg/L for 48 h significantly increased estradiol production of H295R cells in a concentration-dependent manner. Transcription of steroidogenic genes 3β-HSD2, 17β-HSD1, 17β-HSD4, and CYP19A were significantly enhanced by BAC. In ER-positive MCF-7 cells, exposure to 0.5-1.5 mg/L BAC for 48 h significantly promoted cell proliferation and increased the expressions of ERα and G-protein coupled estrogen receptor 1. Flow cytometry analysis showed that 0.5-1.5 mg/L BAC significantly decreased the percentage of cells in G0/G1 phase, increased the percentage in S phase, and BAC at concentrations of 1.0 and 1.5 mg/L increased the G2/M phase cells. Findings of the study suggested that BAC at environmentally-relevant concentrations might act as a xenoestrogen through its inhibitory effect on steroidogenesis and ER-mediated mechanism.

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.

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.

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.

Assessing the Potential Ecotoxicological Risk of Different Organic Amendments Used in Agriculture: Approach Using Acute Toxicity Tests on Plants and Earthworms

In Europe, spreading organic wastes to fertilize soils is an alternative commonly used instead of chemical fertilizers. Through their contributions of nutrients and organic matter, these wastes promote plant growth and thus agricultural production. However, these organic amendments can also contain mineral and organic pollutants requiring chemical and ecotoxicological analyses to guarantee their harmlessness on soil and its organisms during spreading. The purpose of this study was to assess the potential toxicity of three organic amendments from different sources (sewage sludge, dairy cow manure, dairy cow slurry) by performing chemical analyses and acute toxicity tests on three types of organism: earthworms, plants, soil microbial communities. Chemical analysis revealed a higher content of certain pharmaceuticals, polycyclic aromatic hydrocarbons and metals in sewage sludge in comparison with the two other types of organic wastes. The ecotoxicological assessment showed a dose-dependent effect on soil organisms for the three organic amendments with higher toxic effects during the exposure tests with a soil amended with dairy cow slurry. However, at realistic spreading doses (10 and 20 g kg^-1 dry weight of organic amendments) on a representative exposed soil, organic amendment did not show any toxicity in the three organisms studied and had positive effects such as increased earthworm biomass, increased plant root growth and earthworm behavior showing attraction for organic amendment. On the contrary, exposure assays carried out on a limited substrate like sandy soil showed increased toxicity of organic amendments on plant germination and root growth. Overall, the ecotoxicological analysis revealed greater toxicity for soil organisms during the amendment of cow slurry, contrary to the chemical analysis which showed the potential high risk of spreading sewage sludge due to the presence of a higher quantity of pollutants. The analysis of the chemical composition and use of acute toxicity tests is the first essential step for assessing the ecotoxicological risk of spreading organic amendments on soil organisms. In addition to standard tests, the study suggests using a representative soil in acute toxicity tests to avoid overestimating the toxic effects of these organic amendments.

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.

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.

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.

CuS-PNIPAm Nanoparticles with the Ability to Initiatively Capture Bacteria for Photothermal Treatment of Infected Skin

Copper sulfide nanoparticles (CuS NPs) have shown great potential in various application fields, especially in biomedical engineering fields. CuS NPs, with the ability to actively capture and kill bacteria and without the worry of biocompatibility, will greatly expand their applications. Herein, a four-arm star thermo-sensitive polyisopropylacrylamide (4sPNIPAm) was used to modify CuS NPs (CuS-PNIPAm NPs). The obtained nanoparticles displayed the controlled release of copper ions and higher photothermal conversion ability in comparison with contrast materials CuS-PEG NPs and CuS NPs. Aggregation of CuS-PNIPAm NPs at above 34 °C resulted in capturing bacteria by forming the aggregates of nanoparticles-bacteria. Both S. aureus and E. coli co-cultured with CuS-PNIPAm NPs were completely killed upon NIR irradiation in minutes. Furthermore, CuS-PNIPAm NPs were verified to be a photothermal agent without toxic effect. In in vivo experiment, the nanoparticles effectively killed the bacteria in the wound and accelerated the process of wound repairment. Overall, photothermal treatment by CuS-PNIPAm NPs demonstrates the ability to actively capture and kill bacteria, and has a potential in the treatment of infected skin and the regeneration of skin tissues. The therapy will exert a far-reaching impact on the regeneration of stubborn chronic wounds.

Application of an Accessible Interface for Pharmacokinetic Modeling and In Vitro to In Vivo Extrapolation

Regulatory toxicology testing has traditionally relied on in vivo methods to inform decision-making. However, scientific, practical, and ethical considerations have led to an increased interest in the use of in vitro and in silico methods to fill data gaps. While in vitro experiments have the advantage of rapid application across large chemical sets, interpretation of data coming from these non-animal methods can be challenging due to the mechanistic nature of many assays. In vitro to in vivo extrapolation (IVIVE) has emerged as a computational tool to help facilitate this task. Specifically, IVIVE uses physiologically based pharmacokinetic (PBPK) models to estimate tissue-level chemical concentrations based on various dosing parameters. This approach is used to estimate the administered dose needed to achieve in vitro bioactivity concentrations within the body. IVIVE results can be useful to inform on metrics such as margin of exposure or to prioritize potential chemicals of concern, but the PBPK models used in this approach have extensive data requirements. Thus, access to input parameters, as well as the technical requirements of applying and interpreting models, has limited the use of IVIVE as a routine part of in vitro testing. As interest in using non-animal methods for regulatory and research contexts continues to grow, our perspective is that access to computational support tools for PBPK modeling and IVIVE will be essential for facilitating broader application and acceptance of these techniques, as well as for encouraging the most scientifically sound interpretation of in vitro results. We highlight recent developments in two open-access computational support tools for PBPK modeling and IVIVE accessible via the Integrated Chemical Environment (https://ice.ntp.niehs.nih.gov/), demonstrate the types of insights these tools can provide, and discuss how these analyses may inform in vitro-based decision making.

PDE concept for controlling cleaning agent residues in pharmaceuticals- A critical analysis

Cleaning agents (CAs) are used in multipurpose facilities to control carryover contamination of active pharmaceutical ingredients (APIs) to scientifically justified limits. While this is often done with the PDE methodology used for API impurities, it is unclear if it is justifiable and necessary for cleaning agents, which generally represent a comparatively lower health risk. Comparing calculated oral PDE values for CA ingredients (CAIs) from four companies with PDEs of a selected number of small-molecule APIs showed that the toxicity of CAIs is several orders of magnitude lower. Furthermore, a critical review of the toxicity and everyday exposure to the general population of the main CAIs functional groups showed that the expected health risks are generally negligible. This is particularly true if the associated mode of actions cause local toxicity that is usually irrelevant at the concentration of potential residue carryover. This work points towards alternative approaches to the PDE concept to control CAIs' contamination and provides some guidance on grouping and identifying compounds with lower health risks based on exposure and mode of action reasoning. In addition, this work supports the concept that limit values should only be set for CAIs of toxicological concern.

Systematic assessment of quaternary ammonium compounds for the potential to elicit developmental and reproductive effects

INTRODUCTION

Quaternary ammonium compounds (QUATs) are commonly found in cleaning products, disinfectants, hand sanitizers, and personal care products. They have been used for >50 years and are considered safe when used according to directions. Recent papers report reduced fertility and neural tube defects in rodents after low-level exposures. To determine if QUATs interfere with mammalian reproduction and development, we conducted a methodical assessment of all available data.

METHODS

A systematic literature search identified 789 potential articles. Review of titles and abstracts found eight relevant studies, including two dissertation chapters; to these, 10 unpublished, guideline-compliant developmental and reproductive toxicity (DART) studies of QUATs (alkyldimethylbenzylammonium chloride [ADBAC] and dialkyldimethylammonium chloride [DDAC]) were added. ToxRTool was utilized to evaluate all 18 studies for data quality.

RESULTS

Six studies were scored as "reliable without restriction"; four studies were considered "reliable with restriction" (mainly due to small rabbit group sizes). No test article-related, adverse DART endpoints were reported in these studies. ToxRTool scored the remaining eight studies as "not reliable." The unreliable studies failed to fully describe methods and/or endpoints, did not quantify (and in some cases, did not verify) exposures, utilized non-standard test methods, reported endpoints incorrectly, and assessed endpoints at inappropriate times. Some (not all) unreliable studies reported adverse effects after 7.5 mg QUATs/kg/day (mice), but these results were inconsistent. The reliable studies tested exposures ≥100 mg/kg/day (rats) with no effects.

CONCLUSIONS

The available weight of evidence indicates no adverse DART effects after QUATs exposures at anticipated concentrations and normal use.

Assessment of agonistic and antagonistic properties of humidifier disinfectants to the estrogenic and androgenic receptors by transactivation assay

Before being recalled and banned from the Korean market, humidifier disinfectants (HDs) were added to the humidifier water tank to prevent microbial growth. The known HDs active ingredients included the are oligo(2-(2-ethoxy)ethoxyethyl guanidine (PGH), polyhexamethylene guanidine (PHMG), a mixture of methylisothiazolinone (MIT) and chloromethylisothiazolinone (CMIT), didecyldimethyl ammonium chloride (DDAC), Sodium dichloroisocyanurate (NaDCC), and alkyldimethylbenzyl ammonium chloride (BAC). Previous epidemiological studies have suggested that PHMG induces fatal lung disease in pregnant, post-partum women, and young children. In an animal study, a mixture of DDAC and BAC exhibited decreased fertility and fecundity; increased time to first litter, longer pregnancy intervals, fewer pups per litter, and fewer pregnancies. In this study, endocrine-disrupting effects of HDs were investigated using estrogen receptor (ER) and androgen receptor (AR) transactivation assay based on OECD Test guidelines. Unexpectedly, unlike the previously reported reproductive toxicity data, in the present study, HDs did not show ER and AR transcriptional activation agonist and/or antagonist effects. However, it is difficult to conclude that HDs has no endocrine disruption effects, and further research on the effects of HDs mixtures, and in vivo tests including Uterotrophic bioassay and Hershberger bioassay would be necessary.

Reproductive toxicity assessment of alkyl dimethyl benzyl ammonium chloride and didecyl dimethyl ammonium chloride in CD® rats

AIM

To determine the potential of alkyl dimethyl benzyl ammonium chloride (ADBAC) and didecyl dimethyl ammonium chloride (DDAC) to induce reproductive toxicity in CD® rats in two independent 2-generation reproduction studies conducted according to Good Laboratory Practices and standardized testing guidelines.

MATERIALS AND METHODS

Male and female rats (parents and offspring) were allowed continual free access to diets containing concentrations of ADBAC (0, 300, 1,000, or 2,000 ppm) or DDAC (0, 300, 750, or 1,500 ppm), beginning with F₀ generation adults at 10 weeks prior to breeding.

RESULTS

No clinical signs of toxicity were observed in parental rats or their offspring in either study. Dietary exposure of parental rats to ADBAC or DDAC at the highest concentrations produced transient decreases in body weight and/or body weight changes with no or minimal corresponding reduction in food consumption. Offspring (F₁ and F₂ ) in the highest concentration group in each study also exhibited reduced body weights, often with a corresponding reduction in weight change, beginning on postnatal day (PND) 14 through weaning on PND 28. This reduction in pup body weight corresponded to initiation of self-feeding.

CONCLUSIONS

Based on reduced body weights, the no observed adverse effect level (NOAEL) for adult and offspring systemic toxicity was 1,000 ppm for ADBAC and 750 ppm for DDAC (equivalent to approximate daily oral doses of 59 and 45 mg/kg/day, respectively). The reproductive and developmental NOAEL for F₀ , F₁ , and F₂ generation male and female rats was 2,000 ppm for ADBAC and 1,500 ppm for DDAC (equivalent to approximate daily oral doses of 118 and 91 mg/kg/day, respectively).

Evaluation of Effects of Laboratory Disinfectants on Mouse Gut Microbiota

Disturbances in the gut microbiota are known to be associated with numerous human diseases. Mice have proven to be an invaluable tool for investigating the role of the gut microbiota in disease processes. Nonexperimental factors related to maintaining mice in the laboratory environment are increasingly being shown to have inadvertent effects on the gut microbiotaand may function as confounding variables. Microisolation technique is a term used to describe the common biosecuritypractice of spraying gloved hands with disinfectant before handling research mice. This practice prevents contamination with pathogenic microorganisms. To investigate if exposure to disinfectants can affect the mouse gut microbiota, C57BL/6 micewere exposed daily for 27 consecutive days to commonly used laboratory disinfectants through microisolation technique.The effects of 70% ethanol and disinfectant products containing chlorine dioxide, hydrogen peroxide, or potassium peroxymonosulfate were each evaluated. Fecal pellets were collected after 7, 14, 21, and 28 d of disinfectant exposure, and cecal contents were collected at day 28. DNA extractions were performed on all cecal and fecal samples, and microbial community structure was characterized using 16S ribosomal RNA amplicon sequencing. Alpha and β diversity metrics and taxon-level analyses were used to evaluate differences in microbial communities. Disinfectant had a small but significant effect on fecal microbial communities compared with sham-exposed controls, and effects varied by disinfectant type. In general, longerexposure times resulted in greater changes in the fecal microbiota. Effects on the cecal microbiota were less pronounced and only seen with the hydrogen peroxide and potassium peroxymonosulfate disinfectants. These results indicate that laboratory disinfectant use should be considered as a potential factor that can affect the mouse gut microbiota.

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.

Biomaterials for human space exploration: A review of their untapped potential

As biomaterial advances make headway into lightweight radiation protection, wound healing dressings, and microbe resistant surfaces, a relevance to human space exploration manifests itself. To address the needs of the human in space, a knowledge of the space environment becomes necessary. Both an understanding of the environment itself and an understanding of the physiological adaptations to that environment must inform design parameters. The space environment permits the fabrication of novel biomaterials that cannot be produced on Earth, but benefit Earth. Similarly, designing a biomaterial to address a space-based challenge may lead to novel biomaterials that will ultimately benefit Earth. This review describes several persistent challenges to human space exploration, a variety of biomaterials that might mitigate those challenges, and considers a special category of space biomaterial. STATEMENT OF SIGNIFICANCE: This work is a review of the major human and environmental challenges facing human spaceflight, and where biomaterials may mitigate some of those challenges. The work is significant because a broad range of biomaterials are applicable to the human space program, but the overlap is not widely known amongst biomaterials researchers who are unfamiliar with the challenges to human spaceflight. Additionaly, there are adaptations to microgravity that mimic the pathology of certain disease states ("terrestrial analogs") where treatments that help the overwhelmingly healthy astronauts can be applied to help those with the desease. Advances in space technology have furthered the technology in that field on Earth. By outlining ways that biomaterials can promote human space exploration, space-driven advances in biomaterials will further biomaterials technology.

COVID-19 and children's health in the United States: Consideration of physical and social environments during the pandemic

Public health measures necessary to counteract the coronavirus disease 2019 (COVID-19) pandemic have resulted in dramatic changes in the physical and social environments within which children grow and develop. As our understanding of the pathways for viral exposure and associated health outcomes in children evolves, it is critical to consider how changes in the social, cultural, economic, and physical environments resulting from the pandemic could affect the development of children. This review article considers the environments and settings that create the backdrop for children's health in the United States during the COVID-19 pandemic, including current threats to child development that stem from: A) change in exposures to environmental contaminants such as heavy metals, pesticides, disinfectants, air pollution and the built environment; B) changes in food environments resulting from adverse economic repercussion of the pandemic and limited reach of existing safety nets; C) limited access to children's educational and developmental resources; D) changes in the social environments at the individual and household levels, and their interplay with family stressors and mental health; E) social injustice and racism. The environmental changes due to COVID-19 are overlaid onto existing environmental and social disparities. This results in disproportionate effects among children in low-income settings and among populations experiencing the effects of structural racism. This article draws attention to many environments that should be considered in current and future policy responses to protect children's health amid pandemics.

Benzalkonium Chloride Disinfectants Induce Apoptosis, Inhibit Proliferation, and Activate the Integrated Stress Response in a 3-D in Vitro Model of Neurodevelopment

We previously found that the widely used disinfectants, benzalkonium chlorides (BACs), alter cholesterol and lipid homeostasis in neuronal cell lines and in neonatal mouse brains. Here, we investigate the effects of BACs on neurospheres, an in vitro three-dimensional model of neurodevelopment. Neurospheres cultured from mouse embryonic neural progenitor cells (NPCs) were exposed to increasing concentrations (from 1 to 100 nM) of a short-chain BAC (BAC C12), a long-chain BAC (BAC C16), and AY9944 (a known DHCR7 inhibitor). We found that the sizes of neurospheres were decreased by both BACs but not by AY9944. Furthermore, we observed potent inhibition of cholesterol biosynthesis at the step of DHCR7 by BAC C12 but not by BAC C16, suggesting that cholesterol biosynthesis inhibition is not responsible for the observed reduction in neurosphere growth. By using immunostaining and cell cycle analysis, we found that both BACs induced apoptosis and decreased proliferation of NPCs. To explore the mechanisms underlying their effect on neurosphere growth, we carried out RNA sequencing on neurospheres exposed to each BAC at 50 nM for 24 h, which revealed the activation of the integrated stress response by both BACs. Overall, these results suggest that BACs affect neurodevelopment by inducing the integrated stress response in a manner independent of their effects on cholesterol biosynthesis.

Ultrabroad-spectrum, multidrug resistant bacteria-killing, and biocompatible quaternized chitin derivative for infected wound healing

Wound infections have consistently been recognized as serious threats to human. The design of antimicrobial and biocompatible wound dressings for infected wounds is an area of constant research. Herein, we homogeneously synthesized an ultrabroad-spectrum antimicrobial and biocompatible quaternized chitin derivative (QC-4) in a high-efficiency and sustainable route using aqueous KOH/urea solution. Particularly, QC-4 displayed powerful multidrug resistant bacteria-killing activities even at a very low antimicrobial concentration range from 500 ng/mL to 5 μg/mL, including clinically prevalent multidrug-resistant Escherichia coli (MDR-E. coli), methicillin resistant Staphylococcus aureus (MRSA), multidrug-resistant Pseudomonas aeruginosa (MRPA), and multidrug-resistant Acinetobacter baumannii (MDR-A. baumannii). With the aim to facilitate clinical translation, we validated the biocompatibility and safety of QC-4 both in vitro and in vivo, and further assessed the effects of QC-4 on infected wound healing in a porcine infectious full-thickness skin wound model. QC-4 demonstrated significant reduction of microbial aggregates and enhanced wound-healing effects by promoted re-epithelialization and collagen deposition, which were quite comparable to that of commercial Alginate-Ag dressing and absolutely superior to commercial Chitoclot Bandage dressing. Additionally, we provided clear evidences that QC-4 had a unique mechanism of action by attracting electrostatically to the negatively charged microbial surface, thus damaging the microbial cell wall and membrane. Findings of this work provided robust preclinical rationale for the future translational applications of QC-4 as a novel ultrabroad-spectrum and multidrug resistant bacteria-killing antimicrobial wound dressing for clinical wound management.

Initial hazard assessment of ethyl(dimethyl)(tetradecyl)ammonium ethyl sulfate: Genotoxicity tests and combined repeated-dose and reproductive/developmental toxicity screening in rats

Ethyl(dimethyl)(tetradecyl)ammonium ethyl sulfate, used in laundry detergents, shampoos, and body soaps, is classified by the Japanese Chemical Substances Control Law as a priority assessment chemical substance for environmental effects. However, its toxicity data for human health are insufficient. This study evaluated this chemical under the Safety Examination of Existing Chemicals and Safety Programmes of the Ministry of Health, Labour and Welfare (MHLW). The MHLW conducted bacterial reverse mutation (Ames test), in vitro chromosomal aberration, and combined repeated-dose and reproductive/developmental toxicity screening tests. We performed a screening assessment of ethyl(dimethyl)(tetradecyl)ammonium ethyl sulfate for human health. The chemical showed a negative reaction in the Ames test and a positive reaction in the in vitro chromosomal aberration test with metabolic activation in rats. The combined repeated-dose and reproductive/developmental toxicity screening test showed significantly decreased food consumption at 50 mg/kg body weight/day, but no reproductive and developmental toxicity was observed. The no-observed-effect level of 15 mg/kg/day was obtained as a screening value. Therefore, this chemical was classified as hazard class 3, with a derived-no-effect level of 0.025 mg/kg/day. The results of this study will be useful for risk assessment of groups of structurally similar alkyl quaternary ammonium surfactants.

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

Humans are frequently exposed to Quaternary Ammonium Compounds (QACs). QACs are ubiquitously used in medical settings, restaurants, and homes as cleaners and disinfectants. Despite their prevalence, nothing is known about the health effects associated with chronic low-level exposure. Chronic QAC toxicity, only recently identified in mice, resulted in developmental, reproductive, and immune dysfunction. Cell based studies indicate increased inflammation, decreased mitochondrial function, and disruption of cholesterol synthesis. If these findings translate to human toxicity, multiple physiological processes could be affected. This study tested whether QAC concentrations could be detected in the blood of 43 human volunteers, and whether QAC concentrations influenced markers of inflammation, mitochondrial function, and cholesterol synthesis. QAC concentrations were detected in 80 % of study participants. Blood QACs were associated with increase in inflammatory cytokines, decreased mitochondrial function, and disruption of cholesterol homeostasis in a dose dependent manner. This is the first study to measure QACs in human blood, and also the first to demonstrate statistically significant relationships between blood QAC and meaningful health related biomarkers. Additionally, the results are timely in light of the increased QAC disinfectant exposure occurring due to the SARS-CoV-2 pandemic.

MAIN FINDINGS

This study found that 80 % of study participants contained QACs in their blood; and that markers of inflammation, mitochondrial function, and sterol homeostasis varied with blood QAC concentration.

A Critical Review of Disinfection Processes to Control SARS-CoV-2 Transmission in the Food Industry

Industries of the food sector have made a great effort to control SARS-CoV-2 indirect transmission, through objects or surfaces, by updating cleaning and disinfection protocols previously focused on inactivating other pathogens, as well as food spoilage microorganisms. The information, although scarce at the beginning of the COVID-19 pandemic, has started to be sufficiently reliable to avoid over-conservative disinfection procedures. This work reviews the literature to propose a holistic view of the disinfection process where the decision variables, such as type and concentration of active substances, are optimised to guarantee the inactivation of SARS-CoV-2 and other usual pathogens and spoilage microorganisms while minimising possible side-effects on the environment and animal and human health.

Quaternary Ammonium Compound Disinfectants Reduce Lupus-Associated Splenomegaly by Targeting Neutrophil Migration and T-Cell Fate

Hypersensitivity reactions and immune dysregulation have been reported with the use of quaternary ammonium compound disinfectants (QACs). We hypothesized that QAC exposure would exacerbate autoimmunity associated with systemic lupus erythematosus (lupus). Surprisingly, however, we found that compared to QAC-free mice, ambient exposure of lupus-prone mice to QACs led to smaller spleens with no change in circulating autoantibodies or the severity of glomerulonephritis. This suggests that QACs may have immunosuppressive effects on lupus. Using a microfluidic device, we showed that ambient exposure to QACs reduced directional migration of bone marrow-derived neutrophils toward an inflammatory chemoattractant ex vivo. Consistent with this, we found decreased infiltration of neutrophils into the spleen. While bone marrow-derived neutrophils appeared to exhibit a pro-inflammatory profile, upregulated expression of PD-L1 was observed on neutrophils that infiltrated the spleen, which in turn interacted with PD-1 on T cells and modulated their fate. Specifically, QAC exposure hindered activation of splenic T cells and increased apoptosis of effector T-cell populations. Collectively, these results suggest that ambient QAC exposure decreases lupus-associated splenomegaly likely through neutrophil-mediated toning of T-cell activation and/or apoptosis. However, our findings also indicate that even ambient exposure could alter immune cell phenotypes, functions, and their fate. Further investigations on how QACs affect immunity under steady-state conditions are warranted.