Performance of high-efficiency UV-C LEDs in water disinfection: Experimental, life cycle assessment, and economic analysis of different operational scenarios.

The widespread use of low or medium pressure mercury lamps in UV-C water disinfection should consider recent advances in UV-C LED lamps that offer a more sustainable approach and avoid its main drawbacks. The type of water and the mode of operation are critical when deciding on the treatment technology to be used. Therefore, this study investigates the potential application of UV-C LED disinfection technology in terms of kinetics, environmental assessment, and economic analysis for two scenarios: the continuous disinfection of a wastewater treatment plant (WWTP), and disinfection of harvested rainwater (RWH) in a residential household that operates intermittently. Experiments are conducted using both the new UV-C LED system and the conventional mercury lamp to disinfect real wastewater. Removal of total coliforms and Escherichia coli bacteria, with concentrations of approximately 105 and 104 CFU per 100 mL has been followed to assess the performance of both types of UV-C lamps. The experimental study provides kinetic parameters that have been further used in the environmental assessment conducted from a life cycle perspective. Additionally, considering the significant role of electricity consumption, a preliminary economic analysis has been conducted. The results indicate that first-order kinetic constants of pathogens removal with UV-C LEDs achieve 1.4 times higher values than Hg lamp. Regarding the environmental and economic assessment, for disinfection systems operating continuously, LEDs result in environmental impacts 5 times higher than Hg lamp in most categories, indicating that Hg lamps offer a viable option both from economic and environmental point of view. However, for installations with intermittent operation, LEDs emerge as the most competitive alternative, due to their ability to be turned on and off without affecting their lifespan. This study shows that UV-C LED lamps hold promise to replace conventional mercury lamps in a near future.

Assessment of chlorine and hydrogen peroxide on airborne bacteria: Disinfection efficiency and induction of antibiotic resistance.

Airborne pathogens severely threaten public health worldwide. Air disinfection is essential to ensure public health. However, excessive use of disinfectants may endanger environmental and ecological security due to the residual disinfectants and their by-products. This study systematically evaluated disinfection efficiency, induction of multidrug resistance, and the underlying mechanisms of disinfectants (NaClO and H2O2) on airborne bacteria. The results showed that airborne bacteria were effectively inactivated by atomized NaClO (>160 µg/L) and H2O2 (>320 µg/L) after 15 min. However, some bacteria still survived after disinfection by atomized NaClO (0-80 µg/L) and H2O2 (0-160 µg/L), and they exhibited significant increases in antibiotic resistance. The whole-genome sequencing of the resistant bacteria revealed distinct mutations that were responsible for both antibiotic resistance and virulence. This study also provided evidences and insights into possible mechanisms underlying the induction of antibiotic resistance by air disinfection, which involved intracellular reactive oxygen species formation, oxidative stress responses, alterations in bacterial membranes, activation of efflux pumps, and the thickening of biofilms. The present results also shed light on the role of air disinfection in inducing antibiotic resistance, which could be a crucial factor contributing to the global spread of antibiotic resistance through the air.

Assessment of elimination efficacy on foodborne pathogenic microbes and foulant precipitates using phytic acid and sulfamic acid.

This research investigated the comparative efficacy of sulfamic acid (SA) and phytic acid (PA), both individually and in combination, for treating potential foodborne pathogens and pre-formed foulants. Pathogens studied included Listeria monocytogenes, E. coli DH5α, Salmonella typhimurium, Staphylococcus aureus, and vegetative Bacillus cereus, in suspended aqueous solutions, as well as Pseudomonas aeruginosa biofilm on quartz glass surfaces. Inactivation kinetics for Listeria monocytogenes revealed concentration-dependent rate constants (k) of 6.6(±0.2) × 10-6 M and 2.8(±0.1) × 10-8 M for single treatments of SA and PA, respectively, and ranged from 6.9(±0.3) to 50.7(±2.3) × 10-6 M for combined treatments with PA pre-treatment concentrations of 75-758 µM. Observable cellular abnormalities in Listeria monocytogenes, such as membrane vesiculation, chelation, cellular disruption, biomolecule leakage, and lipid peroxidation, were identified after exposure to PA or SA, either individually or in combination. The optimized combined treatment of PA and SA achieved significant removal (i.e., >3-log; 99.9%) of potential foodborne pathogens under simulated food-washing process conditions. Additionally, over 90% descaling efficacy was observed for pre-formed foulants such as CaCO3 precipitates and Pseudomonas aeruginosa biofilm on quartz glass surfaces with the combined treatment. These findings provide novel insights into the versatile utility of PA and SA for optimizing combinational water disinfection systems and addressing (in)organic foulant scaling on surfaces in the food processing industry.

Nanobubbles improve peroxymonosulfate-based advanced oxidation: High efficiency, low toxicity/cost, and novel collaborative mechanism.

Cl- activated peroxymonosulfate (PMS) oxidation technology can effectively degrade pollutants, but the generation of chlorinated disinfection byproducts (DBPs) limits the application of this technology in water treatment. In this study, a method of nanobubbles (NBs) synergistic Cl-/PMS system was designed to try to improve this technology. The results showed the synergistic effects of NBs/Cl-/PMS were significant and universal while its upgrade rate was from 12.89% to 34.97%. Moreover, the synergistic effects can be further improved by increasing the concentration and Zeta potential of NBs. The main synergistic effects of NBs/Cl-/PMS system were due to the electrostatic attraction of negatively charged NBs to Na+ from NaCl, K+ from PMS, and H+ from phenol, which acted as a "bridge" between Cl- and HSO5- as well as phenol and Cl-/HSO5-, increasing active substance concentration. In addition, the addition of NBs completely changed the oxidation system of Cl-/PMS from one that increases environmental toxicity to one that reduces it. The reason was that the electrostatic attraction of NBs changed the active sites and degradation pathway of phenol, greatly reducing the production of highly toxic DBPs. This study developed a novel environmentally friendly oxidation technology, which provides an effective strategy to reduce the generation of DBPs in the Cl-/PMS system.

Photostability and photodynamic antimicrobial profile of dye extracts from four (4) plants: prospects for eco-friendly low-cost food disinfection and topical biomedical applications.

In this study, photostability and photodynamic antimicrobial performance of dye extracts from Hibiscus sabdariffa (HS) calyces, Sorghum bicolor (SB) leaf sheaths, Lawsonia inermis (LI) leaves and Curcuma longa (CL) roots were investigated in Acetate-HCl (AH) Buffer (pH 4.6), Tris Base-HCl (TBH) Buffer (pH 8.6), distilled water (dH2O), and Phosphate Buffer Saline (PBS, pH 7.2) using Bacillus subtilis as model for gram positive bacteria, Escherichia coli as model for gram negative bacteria, phage MS2 as model for non-envelope viruses and phage phi6 as model for envelope viruses including SARS CoV-2 which is the causative agent of COVID-19. Our results showed that the photostability of the dye extracts is in the decreasing order of LI > CL > SB > HS. The dye extract-HS is photostable in dH2O but bleaches in buffers-AH, TBH and PBS. The rate of bleaching is higher in AH compared to in TBH and PBS. The bleaching and buffers affected the photodynamic and non-photodynamic antimicrobial activity of the dye extracts. The photodynamic antibacterial activity of the dye extracts is in the decreasing order of CL > HS > LI > SB while the non-photodynamic antibacterial activity is in the decreasing order of LI > CL > HS > SB. The non-photodynamic antiviral activity pattern observed is the same as that of non-photodynamic antibacterial activity observed. However, the photodynamic antiviral activity of the dye extracts is in the decreasing order of CL > LI > HS > SB. Given their performance, the dye extracts maybe mostly suitable for environmental applications including fresh produce and food disinfection, sanitation of hands and contact surfaces where water can serve as diluent for the extracts and the microenvironment is free of salts.

Resource recovery from soiled sanitary napkin waste-a state-of-the-art review.

With ever-improving social and medical awareness about menstrual hygiene in India, the demand for sanitary napkins has increased significantly. The utilization of high-quality and environment-friendly raw materials to produce these pads is further supporting the growth of the market. However, with improving demand and usage, the need for proper disposal techniques becomes more relevant, since all of these pads get contaminated with human blood which makes them a biohazard and can cause significant damage to human health and the environment. One sanitary pad takes around 800 years to degrade naturally and the plastic and super absorbent polymers (SAPs) in sanitary pads are non-biodegradable and can take multiple decades to degrade. Waste management technologies such as pyrolysis, gasification, and resource recovery can be adopted to manage tons of sanitary waste. Currently, sanitary waste treatment mainly focuses on landfilling, incineration, and composting, where biohazard wastes are mixed with tons of solid waste. Disposable sanitary pads have a high carbon footprint of about 5.3 kg CO2 equivalent every year. Innovative solutions for sanitary pad disposal are discussed in the manuscript which includes repurposing of derived waste cellulose and plastic fraction into value-added products. Future aspects of disinfection strategies and value addition to waste cellulose recovered from napkins were systematically discussed to promote a circular economy.

Trihalomethanes in global drinking water: Distributions, risk assessments, and attributable disease burden of bladder cancer.

This study aimed to assess the global spatiotemporal variations of trihalomethanes (THMs) in drinking water, evaluate their cancer and non-cancer risks, and THM-attributable bladder cancer burden. THM concentrations in drinking water around fifty years on a global scale were integrated. Health risks were assessed using Monte Carlo simulations and attributable bladder cancer burden was estimated by comparative risk assessment methodology. The results showed that global mean THM concentrations in drinking water significantly decreased from 78.37 µg/L (1973-1983) to 51.99 µg/L (1984-2004) and to 21.90 µg/L (after 2004). The lifestage-integrative cancer risk and hazard index of THMs through all exposure pathways were acceptable with the average level of 6.45 × 10-5 and 7.63 × 10-2, respectively. The global attributable disability adjusted of life years (DALYs) and the age-standardized DALYs rate (ASDR) dropped by 16% and 56% from 1990-1994 to 2015-2019, respectively. A big decline in the attributable ASDR was observed in the United Kingdom (62%) and the United States (27%), while China experienced a nearly 3-fold increase due to the expanded water supply coverage and increased life expectancy. However, China also benefited from the spread of chlorination, which helped reduce nearly 90% of unsafe-water-caused mortality from 1998 to 2018.

Bromine contamination and risk management in terrestrial and aquatic ecosystems.

Bromine (Br) is widely distributed through the lithosphere and hydrosphere, and its chemistry in the environment is affected by natural processes and anthropogenic activities. While the chemistry of Br in the atmosphere has been comprehensively explored, there has never been an overview of the chemistry of Br in soil and aquatic systems. This review synthesizes current knowledge on the sources, geochemistry, health and environmental threats, remediation approaches, and regulatory guidelines pertaining to Br pollution in terrestrial and aquatic environments. Volcanic eruptions, geothermal streams, and seawater are the major natural sources of Br. In soils and sediments, Br undergoes natural cycling between organic and inorganic forms, with bromination reactions occurring both abiotically and through microbial activity. For organisms, Br is a non-essential element; it is passively taken up by plant roots in the form of the Br- anion. Elevated Br- levels can limit plant growth on coastal soils of arid and semi-arid environments. Br is used in the chemical industry to manufacture pesticides, flame retardants, pharmaceuticals, and other products. Anthropogenic sources of organobromine contaminants in the environment are primarily wastewater treatment, fumigants, and flame retardants. When aqueous Br- reacts with oxidants in water treatment plants, it can generate brominated disinfection by-products (DBPs), and exposure to DBPs is linked to adverse human health effects including increased cancer risk. Br- can be removed from aquatic systems using adsorbents, and amelioration of soils containing excess Br- can be achieved by leaching, adding various amendments, or phytoremediation. Developing cost-effective methods for Br- removal from wastewater would help address the problem of toxic brominated DBPs. Other anthropogenic organobromines, such as polybrominated diphenyl ether (PBDE) flame retardants, are persistent, toxic, and bioaccumulative, posing a challenge in environmental remediation. Future research directives for managing Br pollution sustainably in various environmental settings are suggested here.

Assessment of Cleaning and Disinfection Practices on Pig Farms across Ten European Countries.

This study delves into the assessment of cleaning and disinfection (C&D) measures within the context of European pig farming, employing the Biocheck.UGent™ tool as an effective instrument for evaluation. A comprehensive set of relevant parameters was examined to enable meaningful comparisons across farms from 10 European countries during four years (2019-2022). Findings indicate a notable increase in C&D measure implementation in select countries (Belgium, Finland, Italy, and Spain), reflecting heightened awareness and responsibility among farmers. Additionally, the overall score for the C&D subcategory highlights variation across countries, with Italy (75), Poland (74), and Belgium (72) displaying the highest scores, while Ireland (56), Slovenia (55), and Serbia (50) reported the lowest scores. However, the considerable variation in the number of participating farms necessitates cautious comparisons. The study identifies well-implemented C&D measures in the frame of external biosecurity but underscores gaps in the application of C&D measures for the material introduction practices across farms (22% of farms), which are attributed to awareness gaps and resource limitations. In the areas of internal biosecurity, strong points include C&D procedures after each production cycle (79%), implementing different stages in the C&D process (65%) and sufficient sanitary break (82%), while gaps are evident in the presence and using of hand hygiene stations (19% of farms) and boots disinfection equipment (40% of farms) between compartments/units. Notably, the study reveals a lack of evaluation of hygiene after C&D procedures (only 1% of farms), signaling critical knowledge gaps among farmers regarding proper assessment tools and methods. In conclusion, this comprehensive analysis sheds light on the implementation status of C&D measures in European pig farming, offering insights into both areas of progress and those requiring improvement. The findings emphasize the need for targeted awareness campaigns and training initiatives to bolster biosecurity practices within the industry.

Assessing sustainability of microalgae-based wastewater treatment: Environmental considerations and impacts on human health.

An integrated life cycle assessment (LCA) and quantitative microbial risk assessment (QMRA) were conducted to assess microalgae-mediated wastewater disinfection (M-WWD). M-WWD was achieved by replacing ultraviolet disinfection with a microalgal open raceway pond in an existing sewage treatment plant (STP) in India. Regarding impacts on human health, both M-WWD and STP yielded comparable life cycle impacts, around 0.01 disability-adjusted life years (DALYs) per person per year. However, QMRA impacts for M-WWD (0.053 DALYs per person per year) were slightly lower than that for STP while considering exposure to E. coli O157:H7 and adenovirus. Additionally, a comparative LCA resolved the dilemma about the appropriate utilization of microalgal biomass. Among biodiesel, biocrude, and biogas production, the lowest impacts of 0.015 DALYs per person per year were obtained for biocrude for 1 m3 water treated by M-WWD. Electricity consumption in microalgae cultivation was a major environmental hotspot. Overall, M-WWD, followed by production of microalgal biocrude, emerged as a sustainable alternative from environmental and public health perspectives. These findings set the foundation for pilot-scale M-WWD system development, testing, and economic evaluation. Such comprehensive investigations, encompassing LCA, QMRA, and resource recovery scenarios, offer crucial insights for stakeholders and decision-makers in wastewater treatment and environmental management.

A qualitative assessment of cleaning and hand hygiene practices at shelters serving people experiencing homelessness during the COVID-19 pandemic, Atlanta, GA - May-June, 2020.

BACKGROUND: Cleaning practices and hand hygiene are important behaviors to prevent and control the spread of infectious disease, especially in congregate settings. This project explored hygiene- and cleaning-related experiences in shelters serving people experiencing homelessness (PEH) during May-June 2020 of the COVID-19 pandemic. METHODS: We conducted qualitative, in-depth interviews by phone with 22 staff from six shelters in Atlanta, Georgia. The interview guide included questions about cleaning routines, cleaning barriers and facilitators, cleaning promotion, hand hygiene promotion, and hand hygiene barriers and facilitators. We analyzed interview transcripts using thematic analysis. RESULTS: Multiple individuals, such as shelter individuals (clients), volunteers, and staff, played a role in shelter cleaning. Staff reported engaging in frequent hand hygiene and cleaning practices. Barriers to cleaning included staffing shortages and access to cleaning supplies. Staff reported barriers (e.g., differing perceptions of cleanliness) for clients who were often involved in cleaning activities. Barriers to hand hygiene included limited time to wash hands, forgetting, and inconvenient handwashing facilities. Specific guidance about when and how to clean, and what supplies to use, were requested. CONCLUSION: During the early months of the COVID-19 pandemic, shelters serving PEH in the Atlanta-metro area needed resources and support to ensure sufficient staffing and supplies for cleaning activities. As part of future pandemic planning and outbreak prevention efforts, shelters serving PEH could benefit from specific guidance and training materials on cleaning and hand hygiene practices.

Plasma-activated liquid as a potential decontaminant in healthcare: assessment of antibacterial activity and use with cleaning cloths.

BACKGROUND: Cold air plasma (CAP) can generate plasma-activated liquids (PALs) with high concentrations of reactive oxygen (ROS) and nitrogen species (RNS), e.g., nitrites, with antimicrobial properties. AIM: We investigated the concentrations of ROS and RNS in saline PAL. We assessed planktonic bacterial inactivation by PAL and the decontamination of contaminated cleaning cloths. METHODS: Phosphate-buffered saline (PBS) was treated with an air-driven CAP jet for 90 or 300 s to generate PAL. The ROS and RNS were measured using quantitative fluorescent (2,7-dichlorofluorescin diacetate) and colourimetric (Greiss) assays. Isolates of MRSA and Escherichia coli were incubated in PAL overnight and inactivation measured through colony forming unit (cfu) assays. Sections of cleaning cloths were incubated with MRSA and E. coli, and treated with PAL for 1 h. Bacterial inactivation was measured through resazurin reduction assays. RESULTS: Nitrites increased from 0.1 µM in untreated PBS to 49.1 µM and to 94.0 µM in 90- and 300-s CAP-treated PAL, respectively. ROS increased from 30 µM in untreated PBS to 75 µM and to 103 µM in 90- and 300-s CAP-treated PAL, respectively. 90-s PAL reduced MRSA and E. coli viability (P<0.05) and 300-s PAL resulted in more than a 7-log reduction of both. One-hour treatment of contaminated cleaning cloths in PAL resulted in a 55% and 73% reduction in viable MRSA and E. coli, respectively (P<0.05). CONCLUSION: Inactivation of planktonic bacteria correlated with ROS and RNS concentrations. PAL reduced bacteria contaminated cleaning cloths. PAL has potential as a hospital disinfectant, including cleaning cloths.

Comparison of Trihalomethane exposure assessment metrics in epidemiologic analyses of reproductive and developmental outcomes.

BACKGROUND: Researchers have developed exposure assessment metrics for disinfection by-products (DBPs) utilizing drinking water monitoring data and accounting for spatial and temporal variability, water consumption, and showering and bathing time with an expectation of decreasing exposure misclassification compared to the use of measured concentrations at public water supply (PWS) monitoring locations alone. OBJECTIVE: We used exposure data collected for a previous study of DBPs to evaluate how different sources of information impact trihalomethane (THM) exposure estimates. METHODS: We compared gestational exposure estimates to THMs based on water utility monitoring data alone, statistical imputation of daily concentrations to incorporate temporal variability, and personal water consumption and use (bathing and showering). We used Spearman correlation coefficients and ranked kappa statistics to compare exposure classifications. RESULTS: Exposure estimates based on measured or imputed daily THM concentrations, self-reported consumption, or bathing and showering differed substantially from estimates based solely on concentrations from PWS quarterly monitoring reports. Ranked exposure classifications, high to low quartiles or deciles, were generally consistent across each exposure metric (i.e., a subject with "high" exposure based on measured or imputed THM concentrations generally remained in the "high" category across exposure metrics.) The measured concentrations and imputed daily (i.e., spline regression) concentrations were highly correlated (r = 0.98). The weighted kappa statistics comparing exposure estimates using different exposure metrics ranged from 0.27 to 0.89, with the highest values for the ingestion + bathing/showering metrics compared to metrics for bathing/showering only (0.76 and 0.89). Bathing and showering contributed the most to "total" THM exposure estimates. IMPACT STATEMENT: We compare exposure metrics capturing temporal variability and multiple estimates of personal THM exposure with THM concentrations from PWS monitoring data. Our results show exposure estimates based on imputed daily concentrations accounting for temporal variability were very similar to the measured THM concentrations. We observed low agreement between imputed daily concentrations and ingestion-based estimates. Considering additional routes of exposure (e.g., inhalation and dermal) slightly increased agreement with the measured PWS exposure estimate in this population. Overall, the comparison of exposure assessment metrics allows researchers to understand the added value of additional data collection for future epidemiologic analyses of DBPs.

Enhancing the effectiveness of bioaerosol disinfection in indoor environments by optimizing far-UVC lamp locations based on Markov chain model.

Far-ultraviolet C (far-UVC) light is an effective and safe disinfection method for bioaerosol control in occupied indoor environments. The installation location of a far-UVC lamp strongly influences the spatial distribution of far-UVC irradiance, and thus the effectiveness of bioaerosol disinfection. To assist the design process, this study developed a fast prediction approach based on the Markov chain model for optimizing the installation locations of far-UVC lamps in order to enhance the disinfection effectiveness for indoor bioaerosol control. Experiments were conducted in an environmental chamber to validate the proposed simulation-based optimization approach. The results show that the proposed method can correctly predict the disinfection efficiency when compared with experimental data, and optimizing the installation location of the far-UVC lamp increased the disinfection efficiency by 54 % compared with the worst location. As an application, the validated method was then used to design the installation location of a far-UVC lamp in a real conference room. The results show that installing the far-UVC lamp in the optimal location can increase the disinfection efficiency by 48 % compared with the worst installation location. Therefore, optimizing the far-UVC lamp location using the proposed Markov chain model can enhance the effectiveness of bioaerosol disinfection in indoor environments.

Recommendations and guidelines for endoscope reprocessing: Current position statement of digestive endoscopic society of Taiwan.

Reprocessing of gastrointestinal (GI) endoscopes and accessories is an essential part of patient safety and quality control in GI endoscopy centers. However, current endoscopic reprocessing guidelines or procedures are not adequate to ensure patient-safe endoscopy. Approximately 5.4 % of the clinically used duodenoscopes remain contaminated with high-concern microorganisms. Thus, the Digestive Endoscopy Society of Taiwan (DEST) sets standards for the reprocessing of GI endoscopes and accessories in endoscopy centers. DEST organized a task force working group using the guideline-revision process. These guidelines contain principles and instructions of step-by-step for endoscope reprocessing. The updated guidelines were established after a thorough review of the existing global and local guidelines, systematic reviews, and health technology assessments of clinical effectiveness. This guideline aims to provide detailed recommendations for endoscope reprocessing to ensure adequate quality control in endoscopy centers.

Occupational inhalation exposure during surface disinfection-exposure assessment based on exposure models compared with measurement data.

BACKGROUND: For healthcare workers, surface disinfections are daily routine tasks. An assessment of the inhalation exposure to hazardous substances, in this case the disinfectant´s active ingredients, is necessary to ensure workers safety. However, deciding which exposure model is best for exposure assessment remains difficult. OBJECTIVE: The aim of the study was to evaluate the applicability of different exposure models for disinfection of small surfaces in healthcare settings. METHODS: Measurements of the air concentration of active ingredients in disinfectants (ethanol, formaldehyde, glutaraldehyde, hydrogen peroxide, peroxyacetic acid) together with other exposure parameters were recorded in a test chamber. The measurements were performed using personal and stationary air sampling. In addition, exposure modelling was performed using three deterministic models (unsteady 1-zone, ConsExpo and 2-component) and one modifying-factor model (Stoffenmanager®). Their estimates were compared with the measured values using various methods to assess model quality (like accuracy and level of conservatism). RESULTS: The deterministic models showed overestimation predominantly in the range of two- to fivefold relative to the measured data and high conservatism for all active ingredients of disinfectants with the exception of ethanol. With Stoffenmanager® an exposure distribution was estimated for ethanol, which was in good accordance with the measured data. IMPACT STATEMENT: To date, workplace exposure assessments often involve expensive and time consuming air measurements. Reliable exposure models can be used to assess occupational inhalation exposure to hazardous substances, in this case surface disinfectants. This study describes the applicability of three deterministic and one modifying-factor model for disinfection of small surfaces in healthcare settings, in direct comparison to measurements performed and will facilitate future exposure assessments at these workplaces.

In Vitro Assessment of SWEEPS and Antimicrobial Photodynamic Therapy Alone or in Combination for Eradicating Enterococcus faecalis Biofilm in Root Canals.

OBJECTIVES: This study investigates the efficacy of antimicrobial photodynamic therapy (aPDT) using riboflavin and a blue diode laser (BDL), combined with shock wave-enhanced emission photoacoustic streaming (SWEEPS), against Enterococcus faecalis. MATERIALS AND METHODS: A total of 48 extracted single-rooted human teeth were used. The root canals were instrumented, sealed at their apices, had the smear layer removed, and then underwent autoclave sterilization. Subsequently, each canal was inoculated with E. faecalis bacterial suspension and allowed to incubate for ten days. After confirming the presence of biofilms through scanning electron microscopy (SEM) in three teeth, the remaining teeth were randomly allocated into nine groups, each containing five teeth: control, 5.25% sodium hypochlorite (NaOCl), BDL, SWEEPS + normal saline, SWEEPS + NaOCl, riboflavin, riboflavin + SWEEPS, riboflavin + BDL, and riboflavin + BDL + SWEEPS. After the treatment, the numbers of colony-forming units (CFUs)/mL were calculated. The data were analysed using one-way ANOVA followed by Tukey's test for comparisons. RESULTS: All groups, with the exception of the BDL group, exhibited a significant reduction in E. faecalis CFU/mL when compared to the control group (p < 0.001). The difference in CFU/mL value between riboflavin + BDL + SWEEPS and riboflavin + SWEEPS was significant (p = 0.029), whereas there was no significant difference between riboflavin + BDL + SWEEPS and riboflavin + BDL (p = 0.397). Moreover, there was no statistically significant difference between the riboflavin + SWEEPS group and the riboflavin + BDL group (p = 0.893). CONCLUSIONS: The results demonstrated that combining the SWEEPS technique with riboflavin as a photosensitizer activated by BDL in aPDT effectively reduced the presence of E. faecalis in root canals.

Quantitative Microbial Risk Assessment for Quantification of the Effects of Ultraviolet Germicidal Irradiation on COVID-19 Transmission.

Quantitative microbial risk assessment (QMRA) is presented as a tool for evaluation of the effectiveness of ultraviolet germicidal irradiation (UVGI) systems for the disinfection of indoor air. The QMRA is developed in the context of UVGI system implementation for control of SARS-CoV-2 infection and comprises submodels to address problem formulation, exposure assessment, and health effects assessment, all of which provide input to a risk characterization submodel. The model simulations indicate that UVGI systems can effectively control the risk of infection associated with SARS-CoV-2 for low to moderate virus emission rates. The risk of disease transmission is strongly influenced by the rate of pathogen emission by an infected individual, the output power of UVGI fixtures and their configuration, the source of UV-C radiation implemented in the UVGI fixtures, and the characteristics of the heating, ventilation, and air conditioning (HVAC) system. The QMRA framework provides a quantitative link between UVGI/HVAC system characteristics and changes in the risk of disease transmission. The framework can be adapted to other airborne pathogens and provides a rational basis for the design, testing, and validation of UVGI systems.

Wrangling Whole Mixtures Risk Assessment: Recent Advances in Determining Sufficient Similarity.

Human health risk assessments for complex mixtures can address real-world exposures and protect public health. While risk assessors typically prefer whole mixture approaches over component-based approaches, data from the precise exposure of interest are often unavailable and surrogate data from a sufficiently similar mixture(s) are required. This review describes recent advances in determining sufficient similarity of whole, complex mixtures spanning the comparison of chemical features, bioactivity profiles, and statistical evaluation to determine "thresholds of similarity". Case studies, including water disinfection byproducts, botanical ingredients, and wildfire emissions, are used to highlight tools and methods. Limitations to application of sufficient similarity in risk-based decision making are reviewed and recommendations presented for developing best practice guidelines.

Genotoxicity Assessment of Haloacetaldehyde Disinfection Byproducts via a Simplified Yeast-Based Toxicogenomics Assay.

Haloacetaldehydes (HALs) represent the third-largest category of disinfection byproducts (DBPs) in drinking water in terms of weight. As a subset of unregulated DBPs, only a few HALs have undergone assessment, yielding limited information regarding their genotoxicity mechanisms. Herein, we developed a simplified yeast-based toxicogenomics assay to evaluate the genotoxicity of five specific HALs. This assay recorded the protein expression profiles of eight Saccharomyces cerevisiae strains fused with green fluorescent protein, including all known DNA damage and repair pathways. High-resolution real-time pathway activation data and protein expression profiles in conjunction with clustering analysis revealed that the five HALs induced various DNA damage and repair pathways. Among these, chloroacetaldehyde and trichloroacetaldehyde were found to be positively associated with genotoxicity, while dichloroacetaldehyde, bromoacetaldehyde, and tribromoacetaldehyde displayed negative associations. The protein effect level index, which are molecular end points derived from a toxicogenomics assay, exhibited a statistically significant positive correlation with the results of traditional genotoxicity assays, such as the comet assay (rp = 0.830 and p < 0.001) and SOS/umu assay (rp = 0.786 and p = 0.004). This yeast-based toxicogenomics assay, which employs a minimal set of gene biomarkers, can be used for mechanistic genotoxicity screening and assessment of HALs and other chemical compounds. These results contribute to bridging the knowledge gap regarding the molecular mechanisms underlying the genotoxicity of HALs and enable the categorization of HALs based on their distinct DNA damage and repair mechanisms.