Efficacy of graphene nanocomposites for air disinfection in dental clinics: A randomized controlled study

BACKGROUND Aerosols containing disease-causing microorganisms are produced during oral diagnosis and treatment can cause secondary contamination.AIM To investigate the use of graphene material for air disinfection in dental clinics by leveraging its adsorption and antibacterial properties.METHODS Patients who received ultrasonic cleaning at our hospital from April 2023 to April 2024.They were randomly assigned to three groups(n=20 each):Graphene nanocomposite material suction group(Group A),ordinary filter suction group(Group B),and no air suction device group(Group C).The air quality and air colony count in the clinic rooms were assessed before,during,and after the procedure.Additionally,bacterial colony counts were obtained from the air outlets of the suction devices and the filter screens in Groups A and B.RESULTS Before ultrasonic cleaning,no significant differences in air quality PM2.5 and colony counts were observed among the three groups.However,significant differences in air quality PM2.5 and colony counts were noted among the three groups during ultrasonic cleaning and after ultrasonic treatment.Additionally,the number of colonies on the exhaust port of the suction device and the surface of the filter were significantly lower in Group A than in Group B(P=0.000 and P=0.000,respectively).CONCLUSION Graphene nanocomposites can effectively sterilize the air in dental clinics by exerting their antimicrobial effects and may be used to reduce secondary pollution.

simple and effective aerosol pathogen disinfection test for a flowing air disinfector

Aerosol transmission is an important disease transmission route and has been especially pertinent to hospital and biosafety laboratories during the SARS-CoV-2 pandemic.The thermal resistance of airborne SARS-CoV-2 is lower than that of Bacillus subtilis spores,which are often used to test the effectiveness of SARS-CoV-2 and other pathogen disinfection methods.Herein,we propose a new method to test the disinfection ability of a flowing air disinfector(a digital electromagnetic induction air heater)using B.subtilis spores.The study provides an alternative air disinfection test method.The new test system combined an aerosol generator and a respiratory filter designed in-house and could effectively recover spores on the filter membrane at the air outlet after passing through the flowing air disinfector.The total number of bacterial spores used in the test was within the range of 5×10^(5)–5×10^(6)colony-forming units(CFUs)specified in the technical standard for disinfection.The calculation was based on the calculation method in Air Disinfection Effect Appraisal Test in Technical Standard for Disinfection(2002 Edition).At an air speed of 3.5 m/s,we used a digital electromagnetic induction air heater to disinfect flowing air containing 4.100×10^(6)CFUs of B.subtilis spores and determined that the minimum disinfection temperature was 350℃for a killing rate of 99.99%.At 400℃,additional experiments using higher spore concentrations(4.700×10^(6)±1.871×10^(5)CFU)and a higher airspeed(4 m/s)showed that the killing rate remained>99.99%.B.subtilis spores,as a biological indicator for testing the efficiency of dry-heat sterilization,were killed by the high temperatures used in this system.The proposed method used to test the flowing air disinfector is simple,stable,and effective.This study provides a reference for the development of test systems that can assess the disinfection ability of flowing air disinfectors.

Airinspace plasmair system in cardiac postoperative infection wards

Background Postoperative wound infection was frequently reported in patients undergoing heart valve re- placement and coronary artery bypass surgery （CABG） due to major trauma, long-term bed rest, malnutrition and compromised immune system. Infected patients were usually housed in the same airborne infection isolation rooms. A series of air monitoring and control strategies should be strictly enforced to aim at avoiding airborne fungal contamination and achieving higher cure rate in infected patients. The efficacy of Airinspace plasmair sys- tem in reducing airborne fungal contamination in cardiac postoperative infection wards has not been clearly de- termined. Methods A survey of air contamination was conducted in the cardiac postoperative infection ward using Airinspace plasmair system. 0.3μm？ and 0.5 μm？ in size. Air Laser particle counter was used to determine the air borne particles of samples were incubated and examined for fungal development. Airborne par- ticle counts and fungal loads of air samples collected before and after treatment with Airinspace plasmair system were compared. Results The particle counts in 0.3 μm range collected before （52206 〈 2345） and after （9408 〈 4317） treated with Airinspace plasmair system differed significantly （P 〈 0.01）. The particle counts in 0.5μm range before （12995 〈 422） and after （2016 〈 915） treatment with Airinspace plasmair system also differed significantly （P 〈 0.01 ）. The fungal loads before and after using Airinspace plasmair system showed significant difference [（1975.3 〈 356.1）cfu/m3 vs. （193.83 〈 29.5）cfu/m3, P 〈 0.01]. Conclusion Airinspace plasmair system used in cardiac postoperative infection wards has shown remarkable efficacy in reducing airborne particles and fungal contamination and helpes prevent cross infection.

Feasibility of bubble surface modification for natural organic matter removal from river water using dissolved air flotation

A novel, functionalized bubble surface can be obtained in dissolved air flotation （DAF） by dosing chemicals in the saturator. In this study, different cationic chemicals were used as bubble surface modifiers, and their effects on natural organic matter （NOM） removal from river water were investigated. NOM in the samples was fractionated based on molecular weight and hydrophobicity. The disinfection byproduct formation potentials of each fraction and their removal efficiencies were also evaluated. The results showed that chitosan was the most promising bubble modifier compared with a surfactant and a synthetic polymer. Tiny bubbles in the OAF pump system facilitated the adsorption of chitosan onto microbubble surfaces. The hydrophobic NOM fraction was preferentially removed by chitosan-modified bubbles. Decreasing the recycle water pH from 7.0 to 5.5 improved the removal of hydrophilic NOM with low molecular weight. Likewise, hydrophilic organic compounds gave high dihaloacetic acid yields in raw water. An enhanced reduction of haloacetic acid precursors was obtained with recycle water at pH values of 5.5 and 4.0. The experimental results indicate that NOM fractions may interact with bubbles through different mechanisms. Positive bubble modification provides an alternative approach for OAF to enhance NOM removal.

Concentrations of disinfection by-products in swimming pool following modifications of the water treatment process:An exploratory study

The formation and concentration of disinfection by-products（DBPs） in pool water and the ambient air vary according to the type of water treatment process used. This exploratory study was aimed at investigating the short-term impact of modifications of the water treatment process on traditional DBP levels（e.g., trihalomethanes（THMs）, chloramines） and emerging DBPs（e.g., Halonitromethanes, Haloketones, NDMA） in swimming pool water and/or air. A sampling program was carried to understand the impact of the following changes made successively to the standard water treatment process： activation of ultraviolet（UV）photoreactor, halt of air stripping with continuation of air extraction from the buffer tank,halt of air stripping and suppression of air extraction from the buffer tank, suppression of the polyaluminium silicate sulfate（PASS） coagulant. UV caused a high increase of Halonitromethanes（8.4 fold）, Haloketones（2.1 fold）, and THMs in the water（1.7 fold） and, of THMs in the air（1.6 fold） and contributed to reducing the level of chloramines in the air（1.6fold） and NDMA in the water（2.1 fold）. The results highlight the positive impact of air stripping in reducing volatile contaminants. The PASS did not change the presence of DBPs, except for the THMs, which decrease slightly with the use of this coagulant. This study shows that modifications affecting the water treatment process can rapidly produce important and variable impacts on DBP levels in water and air and suggests that implementation of any water treatment process to reduce DBP levels should take into account the specific context of each swimming pool.