Ultraviolet C irradiation: A promising approach for the disinfection of public spaces?

Air quality in a bus depot and a way of improving it: effect of using air purifiers

This study assessed airborne particulate matter and black carbon concentrations and their distribution inside a restricted bus depot over two campaigns. Particles with a diameter <2.5 μm were evenly distributed across the depot, influenced by limited bus activity and the depot's spacious layout with three entrances and one exit, facilitating particle dispersion. Their average baseline concentration was 25.2 μg m-3, 4.6 times higher than outdoor levels, primarily driven by bus emissions and maintenance activities. Number concentrations of particles smaller than 0.3 μm (0.01-0.3 μm) averaged 1.3 × 103 particles cm-3, while larger particles (0.3-10 μm) averaged 33 × 100 particles cm-3. Black carbon averaged 1.3 μg m-3. Concentration peaks occurred from 23:00-9:00 and 16:00-18:00 due to bus activities, maintenance, and soil resuspension. The impact of air purifiers on air quality was also investigated focusing on their location, number, and air volume flow for optimal results. APs operating at half air volume flow and placed within 6 m of the measurement equipment achieved reductions of up to 45.2 % for PM2.5 and 73.6 % for particles sized 0.3-10 μm. However, air purifiers were much less effective for particles <0.3 μm. Crossed airflows and higher air volume flow decreased effectiveness due to turbulence and particle resuspension. This study underscores the need for optimized air purifiers placement, air volume flow settings, and operational strategies to mitigate air pollution in (semi-)closed transport environments like bus depots, improving air quality and health for passengers and workers.

Impact of Ultraviolet C Radiation on Male Fertility in Rats: Suppression of Autophagy, Stimulation of Gonadotropin-Inhibiting Hormone, and Alteration of miRNAs

While ultraviolet C (UVC) radiation has beneficial applications, it can also pose risks to living organisms. Nevertheless, a detailed assessment of UVC radiation's effects on mammalian male reproductive physiology, including the underlying mechanisms and potential protective strategies, has not yet been accomplished. This study aimed to examine the critical roles of oxidative stress, autophagy, reproductive hormonal axis, and microRNAs in UVC-induced reproductive challenges in male rats. Semen, biochemical, molecular, and in silico analyses revealed significant dysregulation of testicular steroidogenesis, impaired spermatogenesis, deteriorated sperm quality, and altered reproductive hormonal profiles, which ultimately lead to a decline in fertility in male rats exposed to UVC radiation. Our data indicated that the suppression of autophagy, stimulation of gonadotropin-inhibiting hormone (GnIH), and alteration of microRNAs serve as key mediators of UVC-induced stress effects in mammalian reproduction, potentially contributing to male infertility. Targeting these pathways, particularly through pretreatment with hesperidin (HES), offers a promising strategy to counteract UVC-induced male infertility. In conclusion, the present findings emphasize the importance of understanding the molecular mechanisms behind UVC-induced male infertility and offer valuable insights into the protective mechanisms and prospective role of HES in safeguarding male reproductive health.

[Heavy metals and derangement in carbohydrate metabolism in eye diseases: a systematic review]

PURPOSE

To uncover the negative impacts of heavy metals on carbohydrate metabolism, their mechanisms and contributory factors, as well as their role on the etiopathogenesis, pathophysiology, and progression of eye diseases.

MATERIAL AND METHODS

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), various databases were searched (e.g., Scopus, PubMed, etc.) to collect evidence on the link and role of heavy metals in carbohydrate metabolism and pathogenesis of eye diseases. Included studies were appraised for quality using the Critical Appraisal Skills Programme checklists and extracted data were analyzed using the narrative synthesis method.

RESULTS

Of the 128 papers retrieved, 24 papers met the inclusion criteria. Heavy metals are associated with the onset and progression of diabetes and eye diseases secondary to diabetes (age-related macular degeneration, cataract, and diabetic retinopathy) majorly via toxic interference (induction, inhibition and/or deactivation) of glucose metabolizing enzymes and oxidative stress. The etiology of DR is intricate and includes the simultaneous disruption of several metabolic and signaling mechanisms within the retinal neurovascular unit. The retina is more susceptible to metal-induced toxicities due to the high affinity of heavy metals to melanin content of the retinal epithelium.

CONCLUSION

This study emphasizes the harmful effects of chronic and intermittent exposure to heavy metals, suggesting no safe exposure levels. To prevent eye diseases secondary to heavy metals-induced altered carbohydrate metabolism, metal chelators, low glycemic diets, and lifestyle modifications should be exploited among vulnerable populations.

Far-UVC light (222 nm) efficiently inactivates clinically significant antibiotic-resistant bacteria on diverse material surfaces

In recent years, there has been a gradual increase in the prevalence of drug-resistant bacteria, primarily attributed to the widespread use of antibiotics. This has resulted in heightened mortality rates, morbidity, and exorbitant healthcare costs associated with antibiotic-resistant bacterial infections. In order to mitigate the spread of antibiotic-resistant bacteria, environmental disinfection plays a crucial role. Ultraviolet radiation C (UVC) light disinfection has emerged as a potent technique to limit the transmission of nosocomial pathogens and prevent healthcare-associated infections. Different types of high-touch surfaces were used. A serial disinfected experiment with different 222 nm UVC dosages was conducted on clinically isolated antibiotic-resistant bacteria, including methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus species (VRE), carbapenem-resistant Escherichia coli (CREC), carbapenem-resistant Klebsiella pneumonia (CRKP), carbapenem-resistant Acinetobacter baumannii (CRAB), and carbapenem-resistant Pseudomonas aeruginosa (CRPA) on different material surfaces. The bactericidal efficacy was evaluated by The Clinical & Laboratory Standards Institute (CLSI) guidelines. 222 nm UVC irradiation had a potent bactericidal efficacy on clinical antibiotic-resistant bacteria on different high-touch surfaces that are commonly found in the environment and healthcare facilities. 222 nm UVC irradiation time was tested from 10 s to 1 h. Different surfaces affect the efficiency of 222 nm UVC. The more adsorptive a material is, the higher the dosage of 222 nm UVC irradiation energy is required for effective disinfection. The use of 222 nm UVC lamps for disinfection on different materials has been shown to be a useful method. However, it is crucial to pay attention to the energy required for effective sterilization.

IMPORTANCE

This study is crucial, providing compelling evidence on Far-ultraviolet radiation C (Far-UVC) light's efficacy against clinically significant antibiotic-resistant bacteria-a pressing issue in microbiology and infection control. Our research employs antibiotic-resistant strains from clinically isolated bacteria, emphasizing real-world relevance. Simultaneously, we assess Far-UVC light (222 nm) across diverse material surfaces commonly found in clinical settings. This dual approach ensures practical applicability and broad relevance. Our comprehensive setup and rigorous methodologies unequivocally demonstrate Far-UVC light's potency in combating antibiotic-resistant bacteria. Since 222 nm far-UVC has a disinfection capability and is harmless to mammalian cells, this dual effectiveness positions Far-UVC as a secure tool for infection control, with potential applications in healthcare settings, mitigating antibiotic-resistant bacteria spread, and reducing healthcare-associated infections.

A Comprehensive Review on Studying and Developing Guidelines to Standardize the Inspection of Properties and Production Methods for Mycelium-Bound Composites in Bio-Based Building Material Applications

Mycelium-bound composites (MBCs) represent a promising advancement in bio-based building materials, offering sustainable alternatives for engineering and construction applications. This review provides a comprehensive overview of the current research landscape, production methodologies, and standardization ideas related to MBCs. A basic search on Scopus revealed over 250 publications on MBCs between 2020 and 2024, with more than 30% focusing on engineering and materials science. Key studies have investigated the physical and mechanical properties of MBCs, optimizing parameters such as substrate type, fungal species, incubation time, and post-processing to enhance material performance. Standardizing the inspection of MBC properties is crucial for ensuring quality and reliability. Various testing standards, including those from the American Society for Testing and Materials (ASTM), the International Organization for Standardization (ISO), the Japanese Industrial Standard (JIS), European Standards (EN), Deutsches Institut für Normung (DIN), and the Thai Industrial Standards Institute (TIS), are utilized to evaluate density, water absorption, compression strength, tensile strength, insulation, and other critical properties. This review highlights the distinction between lab-scale and apply-scale testing methodologies, emphasizing the need for comprehensive evaluation protocols. Additionally, the production process of MBCs involves critical steps like substrate preparation, fungal species selection, and mycelium growth, necessitating the implementation of good manufacturing practices (GMPs) to ensure consistency and quality. The internal and external structures of MBCs significantly influence their performance, necessitating standardized inspection methods using advanced techniques such as scanning electron microscopy (SEM), X-ray computed tomography (CT) scanning, and surface profilometry. By establishing robust inspection protocols and production standards, the industry can enhance the reliability and adoption of MBCs, contributing to innovations in materials science and promoting environmental sustainability. This review underscores the importance of interdisciplinary collaboration, advanced characterization tools, and regulatory frameworks to address challenges and advance the field of MBCs.

Ultraviolet irradiation enhances the nitration of allergens

Ultraviolet (UV) light is widely used for disinfection in indoor environments. Some wavelengths of UV light can produce high concentration of O3. UV irradiation combined with O3 may have great potential for nitration of allergens in the presence of NO2 in the air. In this study, the effects of UV irradiation on the nitration of three major indoor allergens including group Ⅰ allergens of house dust mite (Der p 1 and Der f 1) and group Ⅰ allergen of dog (Can f 1) in the presence of NO2 and O3 were investigated by analysis of the protein quantity, tyrosine, peptides, and nitration degree. The results showed that UV irradiation induced a significant increase in the quantity of 3-nitrotyrosine in the allergens from 0.4 ± 0.4 ng to 4.0 ± 0.8 ng. After 12 h of UV-O3 co-exposure, the total nitration degrees of the three allergens ranged from 0.1% to 0.5%, which were significantly higher than those after only O3 exposure (p < 0.05). The analysis of peptides revealed that the nitration of tyrosine was site-specific. The tyrosine Y231, which was adjacent to aspartic acid, posed the highest nitration degree of 41.1 ± 24.0% in Der p 1. The nitration degree of tyrosine Y162 was the highest (1.7 ± 0.1%) in Der f 1. Overall, this study demonstrated that UV irradiation enhanced the O3-related nitration of allergens in the air, which provides an experimental basis for the impact of daily disinfection behavior on allergens.

Ozone generation and chemistry from 222 nm germicidal ultraviolet light in a fragrant restroom

Devices using 222 nm germicidal ultraviolet light (GUV222) have been marketed to reduce virus transmission indoors with low risk of occupant harm from direct UV exposure. GUV222 generates ozone, an indoor air pollutant and oxidant, under constrained laboratory conditions, but the chemistry byproducts of GUV222-generated ozone in real indoor spaces is uncharacterized. We deployed GUV222 in a public restroom, with an air change rate of 1 h-1 one weekend and 2 h-1 the next, to measure ozone formation and byproducts generated from ozone chemistry indoors. Ozone from GUV222 increased background concentrations by 5 ppb on average for both weekends and reacted rapidly (e.g., at rates of 3.7 h-1 for the first weekend and 2.0 h-1 for the second) with gas-phase precursors emitted by urinal screens and on surfaces. These ozone reactions generated volatile organic compound and aerosol byproducts (e.g., up to 2.6 μg m-3 of aerosol mass). We find that GUV222 is enhancing indoor chemistry by at least a factor of two for this restroom. The extent of this enhanced chemistry will likely be different for different indoor spaces and is dependent upon ventilation rates, species and concentrations of precursor VOCs, and surface reactivity. Informed by our measurements of ozone reactivity and background aerosol concentrations, we present a framework for predicting aerosol byproduct formation from GUV222 that can be extended to other indoor spaces. Further research is needed to understand how typical uses of GUV222 could impact air quality in chemically diverse indoor spaces and generate indoor air chemistry byproducts that can affect human health.

A Review Delving into the Factors Influencing Mycelium-Based Green Composites (MBCs) Production and Their Properties for Long-Term Sustainability Targets

Mycelium-based green composites (MBCs) represent an eco-friendly material innovation with vast potential across diverse applications. This paper provides a thorough review of the factors influencing the production and properties of MBCs, with a particular focus on interdisciplinary collaboration and long-term sustainability goals. It delves into critical aspects such as fungal species selection, substrate type selection, substrate preparation, optimal conditions, dehydrating methods, post-processing techniques, mold design, sterilization processes, cost comparison, key recommendations, and other necessary factors. Regarding fungal species selection, the paper highlights the significance of considering factors like mycelium species, decay type, hyphal network systems, growth rate, and bonding properties in ensuring the safety and suitability of MBCs fabrication. Substrate type selection is discussed, emphasizing the importance of chemical characteristics such as cellulose, hemicellulose, lignin content, pH, organic carbon, total nitrogen, and the C: N ratio in determining mycelium growth and MBC properties. Substrate preparation methods, optimal growth conditions, and post-processing techniques are thoroughly examined, along with their impacts on MBCs quality and performance. Moreover, the paper discusses the importance of designing molds and implementing effective sterilization processes to ensure clean environments for mycelium growth. It also evaluates the costs associated with MBCs production compared to traditional materials, highlighting potential cost savings and economic advantages. Additionally, the paper provides key recommendations and precautions for improving MBC properties, including addressing fungal strain degeneration, encouraging research collaboration, establishing biosecurity protocols, ensuring regulatory compliance, optimizing storage conditions, implementing waste management practices, conducting life cycle assessments, and suggesting parameters for desirable MBC properties. Overall, this review offers valuable insights into the complex interplay of factors influencing MBCs production and provides guidance for optimizing processes to achieve sustainable, high-quality composites for diverse applications.

Coverage Planning for UVC Irradiation: Robot Surface Disinfection Based on Swarm Intelligence Algorithm

Ultraviolet (UV) radiation has been widely utilized as a disinfection strategy to effectively eliminate various pathogens. The disinfection task achieves complete coverage of object surfaces by planning the motion trajectory of autonomous mobile robots and the UVC irradiation strategy. This introduces an additional layer of complexity to path planning, as every point on the surface of the object must receive a certain dose of irradiation. Nevertheless, the considerable dosage required for virus inactivation often leads to substantial energy consumption and dose redundancy in disinfection tasks, presenting challenges for the implementation of robots in large-scale environments. Optimizing energy consumption of light sources has become a primary concern in disinfection planning, particularly in large-scale settings. Addressing the inefficiencies associated with dosage redundancy, this study proposes a dose coverage planning framework, utilizing MOPSO to solve the multi-objective optimization model for planning UVC dose coverage. Diverging from conventional path planning methodologies, our approach prioritizes the intrinsic characteristics of dose accumulation, integrating a UVC light efficiency factor to mitigate dose redundancy with the aim of reducing energy expenditure and enhancing the efficiency of robotic disinfection. Empirical trials conducted with autonomous disinfecting robots in real-world settings have corroborated the efficacy of this model in deactivating viruses.

Evaluating the Performance of UV Disinfection across the 222-365 nm Spectrum against Aerosolized Bacteria and Viruses

Bioaerosols play a significant role in the transmission of many infectious diseases, especially in enclosed indoor environments. Ultraviolet (UV) disinfection has demonstrated a high efficacy in inactivating microorganisms suspended in the air. To develop more effective and efficient UV disinfection protocols, it is necessary to evaluate and optimize the effectiveness of UV disinfection against aerosolized bacteria and viruses across the entire UV spectrum. In this study, we evaluated the performance of UV disinfection across the UV spectrum, ranging from 222 to 365 nm, against aerosolized bacteria and viruses, including Escherichia coli, Staphylococcus epidermidis, Salmonella enterica, MS2, P22, and Phi6. Six commonly available UV sources, including gas discharge tubes and light-emitting diodes with different emission spectra, were utilized, and their performance in terms of inactivation efficacy, action spectrum, and energy efficiency was determined. Among these UV sources, the krypton chloride excilamp emitting at a peak wavelength of 222 nm was the most efficient in inactivating viral bioaerosols. A low-pressure mercury lamp emitting at 254 nm performed well on both inactivation efficacy and energy efficiency. A UV light-emitting diode emitting at 268 nm demonstrated the highest bacterial inactivation efficacy, but required approximately 10 times more energy to achieve an equivalent inactivation level compared with that of the krypton chloride excilamp and low-pressure mercury lamp. This study provides insights into UV inactivation on bioaerosols, which can guide the development of effective wavelength-targeted UV air disinfection technologies and may significantly help reduce bioaerosol transmission in public areas.

Far-UV-C irradiation promotes synergistic bactericidal action against adhered cells of Escherichia coli and Staphylococcus epidermidis

The contamination of indoor areas is a global health problem that can cause the dispersion of infectious diseases. In that sense, it is urgent to find new strategies applying a lower concentration of the traditional chemicals used for cleaning and disinfection. Ultraviolet radiation (UV), in particular far-UV-C (200-225 nm), has emerged as a successful, powerful, easy-to-apply, and inexpensive approach for bacterial eradication that still requires scientific assessment. This study investigated new strategies for disinfection based on far-UV-C (222 nm) combined with chlorine and mechanical cleaning, providing an innovative solution using low doses. The bactericidal activity of far-UV-C (222 nm) was tested at an intensity of irradiation from 78.4 μW/cm2 to 597.7 μW/cm2 (for 1 min) against Escherichia coli and Staphylococcus epidermidis adhered on polystyrene microtiter plates. It was further tested in combination with mechanical cleaning (ultrasounds for 1 min) and free chlorine (0.1, 0.5, and 1 mg/L for 5 min). The triple combination consisting of mechanical cleaning + free chlorine (0.5 mg/L) + far-UV-C (54 mJ/cm2) was tested against cells adhered to materials found in hospital settings and other public spaces: polyvinyl chloride (PVC), stainless steel (SS), and polyetheretherketone (PEEK). Disinfection with far-UV-C (54 mJ/cm2) and free chlorine at 0.5 mg/L for 5 min allowed a total reduction of culturable E. coli cells and a logarithmic reduction of 2.98 ± 0.03 for S. epidermidis. The triple combination of far-UV-C, free chlorine, and mechanical cleaning resulted in a total reduction of culturable cells for both adhered bacteria. Bacterial adhesion to PVC, SS, and PEEK occurred at distinct extents and influenced the bactericidal activity of the triple combination, with logarithmic reductions of up to three. The overall results highlight that, based on culturability assessment, far-UV-C (54 mJ/cm2) with chlorine (0.5 mg/L; 5 min) and mechanical cleaning (1 min) as an efficient disinfection strategy using mild conditions. The combination of culturability and viability assessment of disinfection is recommended to detect regrowth events and increase the effectiveness in microbial growth control.

Unleashing the power of acetylacetone: Effective control of harmful cyanobacterial blooms with ecological safety

Harmful algal blooms resulting from eutrophication pose a severe threat to human health. Acetylacetone (AA) has emerged as a potential chemical for combatting cyanobacterial blooms, but its real-world application remains limited. In this study, we conducted a 42-day evaluation of AA's effectiveness in controlling blooms in river water, with a focus on the interplay between ecological community structure, organism functional traits, and water quality. At a concentration of 0.2 mM, AA effectively suppressed the growth of Cyanobacteria (88 %), Bacteroidia (49 %), and Alphaproteobacteria (52 %), while promoting the abundance of Gammaproteobacteria (5.0 times) and Actinobacteria (7.2 times) that are associated with the degradation of organic matter. Notably, after dosing of AA, the OD680 (0.07 ± 0.02) and turbidity (8.6 ± 2.1) remained at a satisfactory level. AA induced significant disruptions in two photosynthesis and two biosynthesis pathways (P < 0.05), while simultaneously enriching eight pathways of xenobiotics biodegradation and metabolism. This enrichment facilitated the reduction of organic pollutants and supported improved water quality. Importantly, AA treatment decreased the abundance of two macrolide-related antibiotic resistance genes (ARGs), ereA and vatE, while slightly increased the abundance of two aminoglycoside-related ARGs, aacA and strB. Overall, our findings establish AA as an efficient and durable algicide with favorable ecological safety. Moreover, this work contributes to the development of effective strategies for maintaining and restoring the health and resilience of aquatic ecosystems impacted by harmful algal blooms.

Formation of halonitromethanes from glycine during LED-UV265/chlorine disinfection

LED-UV265/chlorine is a promising alternative disinfection technology that emits mono-wavelength light for high germicidal efficiency. Halonitromethanes (HNMs) are highly cytotoxic and genotoxic disinfection byproducts that can be formed during LED-UV265/chlorine disinfection. Thus, this work aimed to investigate the HNMs formation from glycine (Gly) during LED-UV265/chlorine disinfection. The results indicated that the concentrations of chlorinated-HNMs (Cl-HNMs) increased first and then decreased as the reaction proceeded. Besides, the effects of operating parameters (UV intensity, free chlorine dosage, and pH) and coexisting ions (Cu2+ and Br-) on HNMs formation were investigated. It was found that the formation concentrations of Cl-HNMs increased with the increase of LED-UV265 intensity and free chlorine dosage but decreased with increased pH. The presence of Cu2+ promoted the formation of Cl-HNMs. The total concentration of HNMs (at 3 min) with adding 1.5 mg/L Cu2+ was 30.90% higher than that without Cu2+. Notably, nine species of HNMs were detected after adding Br-, and the total concentrations of HNMs were enhanced. Moreover, Cl-HNMs were gradually transformed into brominated (chlorinated)-HNMs and brominated-HNMs as Br- concentration increased. According to the findings, the possible formation mechanism of HNMs from Gly during LED-UV265/chlorine disinfection was deduced. Finally, it was demonstrated that the formation laws of HNMs from Gly in real water samples were basically consistent with those in simulated water. Insights obtained in this study help to comprehend the HNMs formation from Gly and provide strategies for controlling the production of HNMs during LED-UV265/chlorine disinfection.

Using photon disinfection technologies for reducing bioburden in hospitals

BACKGROUND

Environmental cleaning and disinfection is the basis of the prevention of healthcare-acquired infections (HAIs).

AIM

This study aimed to describe photon disinfection technologies (PDTs), report their impact on inactivating micro-organisms and preventing HAIs and to create recommendations for their implementation in hospital settings.

METHODS

An integrated literature review was completed to evaluate and report the impact of PDTs in hospital settings. The quality of 23 articles were assessed, their contents analysed and results reported according to the PICOT model.

FINDINGS

The microbiological impact of the PDT varied by micro-organism, settings and according to the used devices. It was crucial that environmental cleaning was completed before the disinfection.

CONCLUSION

The implementation of PDT in the hospital setting requires inquiry from the viewpoints of microbiological, environmental, occupational, technical and human safety. To enhance the safe implementation of PDTs, the construction and use of evidence-based global standards for PDT are crucial.

The Prophylactic Effect of Vitamin C and Vitamin B12 against Ultraviolet-C-Induced Hepatotoxicity in Male Rats

Ultraviolet C (UVC) devices are an effective means of disinfecting surfaces and protecting medical tools against various microbes, including coronavirus. Overexposure to UVC can induce oxidative stress, damage the genetic material, and harm biological systems. This study investigated the prophylactic efficacy of vitamin C and B12 against hepatotoxicity in UVC-intoxicated rats. Rats were irradiated with UVC (725.76, 967.68, and 1048.36 J/cm²) for 2 weeks. The rats were pretreated with the aforementioned antioxidants for two months before UVC irradiation. The prophylactic effect of vitamins against UVC hepatotoxicity was evaluated by monitoring the alteration of liver enzyme activities, antioxidant status, apoptotic and inflammatory markers, DNA fragmentation, and histological and ultrastructural alterations. Rats exposed to UVC showed a significant increase in liver enzymes, oxidant-antioxidant balance disruption, and increased hepatic inflammatory markers (TNF-α, IL-1β, iNOS, and IDO-1). Additionally, obvious over-expression of activated caspase-3 protein and DNA fragmentation were detected. Histological and ultrastructural examinations verified the biochemical findings. Co-treatment with vitamins ameliorated the deviated parameters to variable degrees. In conclusion, vitamin C could alleviate UVC-induced hepatotoxicity more than vitamin B12 by diminishing oxidative stress, inflammation, and DNA damage. This study could provide a reference for the clinical practice of vitamin C and B12 as radioprotective for workers in UVC disinfectant areas.