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Remarkable perturbations in the stratospheric abundances of chlorine species and ozone were observed over Southern Hemisphere mid-latitudes following the 2020 Australian wildfires 1 , 2 . These changes in atmospheric chemical composition suggest that wildfire aerosols affect stratospheric chlorine and ozone depletion chemistry. Here we propose that wildfire aerosol containing a mixture of oxidized organics and sulfate 3 – 7 increases hydrochloric acid solubility 8 – 11 and associated heterogeneous reaction rates, activating reactive chlorine species and enhancing ozone loss rates at relatively warm stratospheric temperatures. We test our hypothesis by comparing atmospheric observations to model simulations that include the proposed mechanism. Modelled changes in 2020 hydrochloric acid, chlorine nitrate and hypochlorous acid abundances are in good agreement with observations 1 , 2 . Our results indicate that wildfire aerosol chemistry, although not accounting for the record duration of the 2020 Antarctic ozone hole, does yield an increase in its area and a 3–5% depletion of southern mid-latitude total column ozone. These findings increase concern 2 , 12 , 13 that more frequent and intense wildfires could delay ozone recovery in a warming world. Comparison of model simulations with atmospheric observations from the Southern Hemisphere mid-latitudes following the 2020 Australian wildfires shows that the wildfire aerosol composition promotes stratospheric chlorine and ozone depletion chemistry.

Background Recent randomized clinical trials suggest that the effect of using cetylpyridinium chloride (CPC) mouthwashes on the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral load in COVID-19 patients has been inconsistent. Additionally, no clinical study has investigated the effectiveness of on-demand aqueous chlorine dioxide mouthwash against COVID-19. Methods We performed a randomized, placebo-controlled, open-label clinical trial to assess for any effects of using mouthwash on the salivary SARS-CoV-2 viral load among asymptomatic to mildly symptomatic adult COVID-19-positive patients. Patients were randomized to receive either 20 mL of 0.05% CPC, 10 mL of 0.01% on-demand aqueous chlorine dioxide, or 20 mL of placebo mouthwash (purified water) in a 1:1:1 ratio. The primary endpoint was the cycle threshold (Ct) values employed for SARS-CoV-2 salivary viral load estimation. We used linear mixed-effects models to assess for any effect of the mouthwashes on SARS-CoV-2 salivary viral load. Results Of a total of 96 eligible participants enrolled from November 7, 2022, to January 19, 2023, 90 were accepted for the primary analysis. The use of 0.05% CPC mouthwash was not shown to be superior to placebo in change from baseline salivary Ct value at 30 min (difference vs. placebo, 0.640; 95% confidence interval [CI], -1.425 to 2.706; P  = 0.543); 2 h (difference vs. placebo, 1.158; 95% CI, -0.797 to 3.112; P  = 0.246); 4 h (difference vs. placebo, 1.283; 95% CI, -0.719 to 3.285; P  = 0.209); 10 h (difference vs. placebo, 0.304; 95% CI, -1.777 to 2.385; P  = 0.775); or 24 h (difference vs. placebo, 0.782; 95% CI, -1.195 to 2.759; P  = 0.438). The use of 0.01% on-demand aqueous chlorine dioxide mouthwash was also not shown to be superior to placebo in change from baseline salivary Ct value at 30 min (difference vs. placebo, 0.905; 95% CI, -1.079 to 2.888; P  = 0.371); 2 h (difference vs. placebo, 0.709; 95% CI, -1.275 to 2.693; P  = 0.483); 4 h (difference vs. placebo, 0.220; 95% CI, -1.787 to 2.226; P  = 0.830); 10 h (difference vs. placebo, 0.198; 95% CI, -1.901 to 2.296; P  = 0.854); or 24 h (difference vs. placebo, 0.784; 95% CI, -1.236 to 2.804; P  = 0.447). Conclusions In asymptomatic to mildly symptomatic adults with COVID-19, compared to placebo, the use of 0.05% CPC and 0.01% on-demand aqueous chlorine dioxide mouthwash did not lead to a significant reduction in SARS-CoV-2 salivary viral load. Future studies of the efficacy of CPC and on-demand aqueous chlorine dioxide mouthwash on the viral viability of SARS-CoV-2 should be conducted using different specimen types and in multiple populations and settings.

Chlorine dioxide is widely used for pulp bleaching because of its high delignification selectivity. However, efficient and clean chlorine dioxide bleaching is limited by the complexity of the lignin structure. Herein, the oxidation reactions of phenolic (vanillyl alcohol) and non-phenolic (veratryl alcohol) lignin model species were modulated using chlorine dioxide. The effects of chlorine dioxide concentration, reaction temperature, and reaction time on the consumption rate of the model species were also investigated. The optimal consumption rate for the phenolic species was obtained at a chlorine dioxide concentration of 30 mmol·L−1, a reaction temperature of 40 °C, and a reaction time of 10 min, resulting in the consumption of 96.3% of vanillyl alcohol. Its consumption remained essentially unchanged compared with that of traditional chlorine dioxide oxidation. However, the consumption rate of veratryl alcohol was significantly reduced from 78.0% to 17.3%. Additionally, the production of chlorobenzene via the chlorine dioxide oxidation of veratryl alcohol was inhibited. The structural changes in lignin before and after different treatments were analyzed. The overall structure of lignin remained stable during the optimization of the chlorine dioxide oxidation treatment. The signal intensities of several phenolic units were reduced. The effects of the selective oxidation of lignin by chlorine dioxide on the pulp properties were analyzed. Pulp viscosity significantly increased owing to the preferential oxidation of phenolic lignin by chlorine dioxide. The pollution load of bleached effluent was considerably reduced at similar pulp brightness levels. This study provides a new approach to chlorine dioxide bleaching. An efficient and clean bleaching process of the pulp was developed.

The COVID-19 pandemic has tremendously increased the production and sales of disinfectants. This study aimed to systematically review and analyze the efficacy and safety of chlorine dioxide as a disinfectant. The literature relating to the use of chlorine dioxide as a disinfectant was systematically reviewed in January 2021 using databases such as PubMed, Science Direct, and Google Scholar. Inclusion criteria were studies that investigated the use of chlorine dioxide to assess the efficacy, safety, and impact of chlorine dioxide as a disinfectant. Out of the 33 included studies, 14 studies focused on the disinfectant efficacy of chlorine dioxide, 8 studies expounded on the safety and toxicity in humans and animals, and 15 studies discussed the impact, such as water treatment disinfection using chlorine dioxide. Chlorine dioxide is a safe and effective disinfectant, even at concentrations as low as 20 to 30 mg/L. Moreover, the efficacy of chlorine dioxide is mostly independent of pH. Chlorine dioxide can be effectively used to disinfect drinking water without much alteration of palatability and can also be used to destroy pathogenic microbes, including viruses, bacteria, and fungi from vegetables and fruits. Our review confirms that chlorine dioxide is effective against the resistant Mycobacterium , H1N1, and other influenza viruses. Studies generally support the use of chlorine dioxide as a disinfectant. The concentration deemed safe for usage still needs to be determined on a case-by-case basis.

Chlorine dioxide (ClO2) is a strong oxidizing agent and an efficient disinfectant. Due to its broad-spectrum bactericidal properties, good inactivation effect on the vast majority of bacteria and pathogenic microorganisms, low resistance to drugs, and low generation of halogenated by-products, chlorine dioxide is widely used in fields such as water purification, food safety, medical and public health, and living environment. This review introduced the properties and application status of chlorine dioxide, compared the action mode, advantages and disadvantages of various disinfectants. The mechanism of chlorine dioxide inactivating bacteria, fungi and viruses were reviewed. The lethal target of chlorine dioxide to bacteria and fungi is to destroy the structure of cell membrane, change the permeability of cell membrane, and make intracellular substances flow out, leading to their death. The lethal targets for viruses are the destruction of viral protein capsids and the degradation of RNA fragments. The purpose of this review is to provide more scientific guidance for the application of chlorine dioxide disinfectants.

This study evaluates the in vitro antimicrobial efficacy and cytotoxicity of acidified sodium chlorite (ASC), a source of chlorine dioxide. Despite its controversial promotion in alternative medicine as a cure-all solution, known as \"Miracle Mineral Solution\" (MMS), the data on its factual medicinal activity is very limited. Therefore, we aimed to elucidate the activity of ASC against biofilms of Staphylococcus aureus , Pseudomonas aeruginosa , Enterococcus faecalis , Streptococcus mutans , Pseudomonas aeruginosa , Escherichia coli , and Lactobacillus sp . or an organic acid (ASC1, ASC2, respectively). The lowest antimicrobial concentration of ASC registered was 0.002992% (29.92 ppm) but did not exhibit stronger antimicrobial activity than polyhexamethylene biguanide. Biofilms of S. mutans and E. coli were the most susceptible to tested formulations. Biofilm formed by L. rhamnosus displayed susceptibility to concentrations lower than the minimum biofilm eradication concentration (0.09575%, 957.5 ppm). In the in vitro cytotoxic assay towards eukaryotic fibroblasts and in vivo model of Galleria mellonella larvae concentration-related increase of cytotoxic effects was observed. Our findings demonstrate that these concentrations of ASC which can effectively eradicate biofilms, also pose potential health risks due to their in vitro and in vivo cytotoxicity. It implies that ASC applied in humans can lead to damage to the mucous membrane of the gastrointestinal tract. This research contributes to the ongoing debate on the safety and efficacy of chlorine dioxide in clinical applications, highlighting the need for precise dosing to avoid mucosal damage in therapeutic contexts.

We present a comprehensive simulation of tropospheric chlorine within the GEOS-Chem global 3-D model of oxidant–aerosol–halogen atmospheric chemistry. The simulation includes explicit accounting of chloride mobilization from sea salt aerosol by acid displacement of HCl and by other heterogeneous processes. Additional small sources of tropospheric chlorine (combustion, organochlorines, transport from stratosphere) are also included. Reactive gas-phase chlorine Cl*, including Cl, ClO, Cl2, BrCl, ICl, HOCl, ClNO3, ClNO2, and minor species, is produced by the HCl+OH reaction and by heterogeneous conversion of sea salt aerosol chloride to BrCl, ClNO2, Cl2, and ICl. The model successfully simulates the observed mixing ratios of HCl in marine air (highest at northern midlatitudes) and the associated HNO3 decrease from acid displacement. It captures the high ClNO2 mixing ratios observed in continental surface air at night and attributes the chlorine to HCl volatilized from sea salt aerosol and transported inland following uptake by fine aerosol. The model successfully simulates the vertical profiles of HCl measured from aircraft, where enhancements in the continental boundary layer can again be largely explained by transport inland of the marine source. It does not reproduce the boundary layer Cl2 mixing ratios measured in the WINTER aircraft campaign (1–5 ppt in the daytime, low at night); the model is too high at night, which could be due to uncertainty in the rate of the ClNO2+Cl- reaction, but we have no explanation for the high observed Cl2 in daytime. The global mean tropospheric concentration of Cl atoms in the model is 620 cm−3 and contributes 1.0 % of the global oxidation of methane, 20 % of ethane, 14 % of propane, and 4 % of methanol. Chlorine chemistry increases global mean tropospheric BrO by 85 %, mainly through the HOBr+Cl- reaction, and decreases global burdens of tropospheric ozone by 7 % and OH by 3 % through the associated bromine radical chemistry. ClNO2 chemistry drives increases in ozone of up to 8 ppb over polluted continents in winter.

Hollow core optical fibres (HCFs) are a specialty optical fibre, where light can be transmitted with low loss within an air-filled core. This is in contrast to conventional optical fibres, where light is usually transmitted in glass (most often silica). The advantages of HCFs over conventional fibres include ultra-low loss, low latency and low non-linearity, and rapid progress in recent years is now leading to their deployment in real-world applications [1]. Hence the long-term reliability and consistency of their optical performance is becoming one of the current essential research topics. In a HCF, light is confined with low loss within the air core by a carefully designed microstructured cladding, that, depending on fibre design, can consist of up to several hundred air-filled holes, defined by thin silica membranes. It is reasonable to consider that these air holes, which extend longitudinally along the full length of a HCF, add extra complexity to their ageing mechanism(s) compared to conventional solid fibres. The extensive surface areas due to the hollow structures within the fibres increase the potential for optical degradation through reactions with gas species within the hollow structure. This study describes progress in understanding and identification of processes, and their origins, which affect the long-term fibre optical performance, and suitable treatments, during or post fabrication, are considered as a means to improve the fibre's durability. This investigation is performed considering two key silica surface areas with an HCF: the inner surfaces created by the thin silica membranes which extend throughout the fibre length and also the fibre end-faces, which are created when an HCF is cleaved. Although these separate works have their own specific focuses, they are closely interlinked with each other and their study is relevant to a wide range of applications and to understand the long term optical performance of a HCF in various scenarios. Within this work, the high potential for atmospheric water vapour to degrade the inside of a HCF was revealed. Water vapour not only absorbs light at specific wavelengths (absorption resonances) but also accumulates on the inner surfaces within a HCF via chemical and physical reactions with the silica membranes. Most of the water vapour involved in the reaction originates from the fibre's surrounding atmosphere, initially being drawn into the open-ended fibre due to sub-atmospheric absolute pressure inside a HCF immediately after fabrication. It was found that the formation of the surface water groups on the inner silica surface increased the loss of hollow core photonic bandgap fibres when the fibre was open to standard atmosphere (HC-PBGFs, a specific type of HCF), but the increase in loss due to the atmospheric water vapour was shown to be negligible within state-of-art, low loss hollow core anti-resonant fibres (HC-ARF). This can be attributed to the substantially lower overlap between the guided light in and the microstructured cladding within a HC-ARF as compared to a HC-PBGF. One of the simplest methods to extend the lifespan of HCFs, which is suggested here, will be to isolate the inside of the hollow structure from the humidity containing atmosphere as much as possible after fibre draw; this is practical in many applications, such as telecommunications, where the fibre can be hermetically spliced to other optical components. Degradation of the end-faces of a HCF due to crystalline contamination has been previously identified and is a known concern for reliability of a HCF when the fibre is used in a free-space optical set-up. However, prior to this work, several fundamental pieces of information about this phenomena had been left unsolved. Here, the contaminant appearing on a cleaved end-face surface of a HCF was identified as the ammonium chloride crystal and it was confirmed that this contamination occurs specifically on microstructured fibres which contain longitudinal air holes. The source of the chlorine required to form this crystal contaminant is the raw material used for fabrication of HCFs (high purity silica glass containing a small amount of chlorine). Whilst the origin of the ammonium is still unclear, our findings through different experiments suggest that an intermediate molecule is produced under the high temperature environment required during fibre fabrication and is present on the inner silica surfaces within a HCF. With this understanding, several methods to mitigate/stop the degradation are demonstrated and proposed: use of a lower-chlorine containing material, removal of the hydrogen chloride gas and treatment of a cleaved end-face.

Propane dehydrogenation (PDH) to propene is an important alternative to oil-based cracking processes, to produce this industrially important platform chemical 1 , 2 . The commercial PDH technologies utilizing Cr-containing (refs. 3 , 4 ) or Pt-containing (refs. 5 – 8 ) catalysts suffer from the toxicity of Cr( vi ) compounds or the need to use ecologically harmful chlorine for catalyst regeneration 9 . Here, we introduce a method for preparation of environmentally compatible supported catalysts based on commercial ZnO. This metal oxide and a support (zeolite or common metal oxide) are used as a physical mixture or in the form of two layers with ZnO as the upstream layer. Supported ZnO x species are in situ formed through a reaction of support OH groups with Zn atoms generated from ZnO upon reductive treatment above 550 °C. Using different complementary characterization methods, we identify the decisive role of defective OH groups for the formation of active ZnO x species. For benchmarking purposes, the developed ZnO–silicalite-1 and an analogue of commercial K–CrO x /Al 2 O 3 were tested in the same setup under industrially relevant conditions at close propane conversion over about 400 h on propane stream. The developed catalyst reveals about three times higher propene productivity at similar propene selectivity. Propene is obtained through propane dehydrogenation using catalysts that are toxic, expensive or demanding to regenerate with ecologically harmful compounds, but the ZnO-based alternative reported here is cheap, clean and scalable.

We aimed to conduct a systematic review on published data in order to investigate the efficacy of mouthwash products containing chlorine dioxide in halitosis. Systematic review and meta-analysis. Our search was conducted on 14th October 2021. We searched the following electronic databases: MEDLINE, Embase, Scopus, Web of Science, and CENTRAL. We analysed data on adults with halitosis, included only randomised controlled trials and excluded in vitro and animal studies. The interventional groups used chlorine dioxide, and the comparator groups used a placebo or other mouthwash. Our primary outcomes were changes in organoleptic test scores (OLS) and Volatile Sulfur Compound (VSC) levels from baseline to the last available follow-up. We found 325 articles in databases. After the selection process, ten articles were eligible for qualitative synthesis, and 7 RCTs with 234 patients were involved in the meta-analysis. Our findings showed a significant improvement in the parameters of the chlorine dioxide group compared to the placebo group in OLS one-day data (mean difference (MD): -0.82; 95% confidence intervals (95% CIs): [-1.04 --0.6]; heterogeneity: I2 = 0%, p = 0.67); and one-week OLS data (MD: -0.24; 95% CIs: [-0.41 --0.07]; I2 = 0%, p = 0.52); and also changes in H2S one-day data (standardised mean difference (SMD): -1.81; 95% CIs: [-2.52 --1.10]); I2 = 73.4%, p = 0.02). Our data indicate that chlorine dioxide mouthwash may be a good supportive therapy in oral halitosis without known side effects.