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Park S, Won Y, Rim D. Formation and Transport of Secondary Contaminants Associated with Germicidal Ultraviolet Light Systems in an Occupied Classroom. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:12051-12061. [PMID: 38922431 DOI: 10.1021/acs.est.4c00575] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/27/2024]
Abstract
Germicidal ultraviolet light (GUV) systems are designed to control airborne pathogen transmission in buildings. However, it is important to acknowledge that certain conditions and system configurations may lead GUV systems to produce air contaminants including oxidants and secondary organic aerosols (SOA). In this study, we modeled the formation and dispersion of oxidants and secondary contaminants generated by the operation of GUV systems employing ultraviolet C 254 and 222 nm. Using a three-dimensional computational fluid dynamics model, we examined the breathing zone concentrations of chemical species in an occupied classroom. Our findings indicate that operating GUV 222 leads to an approximate increase of 10 ppb in O3 concentration and 5.2 μg·m-3 in SOA concentration compared to a condition without GUV operation, while GUV 254 increases the SOA concentration by about 1.2 μg·m-3, with a minimal impact on the O3 concentration. Furthermore, increasing the UV fluence rate of GUV 222 from 1 to 5 μW·cm-2 results in up to 80% increase in the oxidants and SOA concentrations. For GUV 254, elevating the UV fluence rate from 30 to 50 μW·cm-2 or doubling the radiating volume results in up to 50% increase in the SOA concentration. Note that indoor airflow patterns, particularly buoyancy-driven airflow (or displacement ventilation), lead to 15-45% lower SOA concentrations in the breathing zone compared to well-mixed airflow. The results also reveal that when the ventilation rate is below 2 h-1, operating GUV 254 has a smaller impact on human exposure to secondary contaminants than GUV 222. However, GUV 254 may generate more contaminants than GUV 222 when operating at high indoor O3 levels (>15 ppb). These results suggest that the design of GUV systems should consider indoor O3 levels and room ventilation conditions.
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Affiliation(s)
- Seongjun Park
- Department of Architectural Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Youngbo Won
- Department of Architectural Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Donghyun Rim
- Department of Architectural Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, United States
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Lee LD, Lie L, Bauer M, Bolanos B, Olmsted RN, Varma JK, Parada JP. Reduction of airborne and surface-borne bacteria in a medical center burn intensive care unit using active, upper-room, germicidal ultraviolet (GUV) disinfection. Infect Control Hosp Epidemiol 2024; 45:367-373. [PMID: 37877197 PMCID: PMC10933500 DOI: 10.1017/ice.2023.223] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Revised: 08/21/2023] [Accepted: 09/15/2023] [Indexed: 10/26/2023]
Abstract
OBJECTIVE To determine the effectiveness of active, upper-room, germicidal ultraviolet (GUV) devices in reducing bacterial contamination in patient rooms in air and on surfaces as a supplement to the central heating, ventilation, and air conditioning (HVAC) air handling unit (AHU) with MERV 14 filters and UV-C disinfection. METHODS This study was conducted in an academic medical center, burn intensive care unit (BICU), for 4 months in 2022. Room occupancy was monitored and recorded. In total, 402 preinstallation and postinstallation bacterial air and non-high-touch surface samples were obtained from 10 BICU patient rooms. Airborne particle counts were measured in the rooms, and bacterial air samples were obtained from the patient-room supply air vents and outdoor air, before and after the intervention. After preintervention samples were obtained, an active, upper-room, GUV air disinfection system was deployed in each of the patient rooms in the BICU. RESULTS The average levels of airborne bacteria of 395 CFU/m3 before GUV device installation and 37 CFU/m3 after installation indicated an 89% overall decrease (P < .0001). Levels of surface-borne bacteria were associated with a 69% decrease (P < .0001) after GUV device installation. Outdoor levels of airborne bacteria averaged 341 CFU/m3 in March before installation and 676 CFU/m3 in June after installation, but this increase was not significant (P = .517). CONCLUSIONS Significant reductions in air and surface contamination occurred in all rooms and areas and were not associated with variations in outdoor air concentrations of bacteria. The significant decrease of surface bacteria is an unexpected benefit associated with in-room GUV air disinfection, which can potentially reduce overall bioburden.
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Affiliation(s)
| | - Louise Lie
- Loyola University Medical Center, Maywood, Illinois
| | | | | | | | - Jay K. Varma
- Weill Cornell Medical College, New York, New York
| | - Jorge P. Parada
- Loyola University Medical Center, Maywood, Illinois
- Loyola University Chicago, Chicago, Illinois
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Li P, Koziel JA, Paris RV, Macedo N, Zimmerman JJ, Wrzesinski D, Sobotka E, Balderas M, Walz WB, Liu D, Yedilbayev B, Ramirez BC, Jenks WS. Indoor air quality improvement with filtration and UV-C on mitigation of particulate matter and airborne bacteria: Monitoring and modeling. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2024; 351:119764. [PMID: 38100867 DOI: 10.1016/j.jenvman.2023.119764] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2023] [Revised: 11/28/2023] [Accepted: 12/03/2023] [Indexed: 12/17/2023]
Abstract
Indoor air, especially with suspended particulate matter (PM), can be a carrier of airborne infectious pathogens. Without sufficient ventilation, airborne infectious diseases can be transmitted from one person to another. Indoor air quality (IAQ) significantly impacts people's daily lives as people spend 90% of their time indoors. An industrial-grade air cleaner prototype (filtration + ultraviolet light) was previously upgraded to clean indoor air to improve IAQ on two metrics: particulate matter (PM) and viable airborne bacteria. Previous experiments were conducted to test its removal efficiency on PM and airborne bacteria between the inlet and treated air. However, the longer-term improvement on IAQ would be more informative. Therefore, this research focused on quantifying longer-term improvement in a testing environment (poultry facility) loaded with high and variable PM and airborne bacteria concentrations. A 25-day experiment was conducted to treat indoor air using an air cleaner prototype with intermittent ON and OFF days in which PM and viable airborne bacteria were measured to quantify the treatment effect. The results showed an average of 55% reduction of total suspended particulate (TSP) concentration between OFF days (110 μg/m3) and ON days (49 μg/m3). An average of 47% reduction of total airborne viable bacteria concentrations was achieved between OFF days (∼3200 CFU/m3) and ON days (∼2000 CFU/m3). A cross-validation (CV) model was established to predict PM concentrations with five input variables, including the status of the air cleaner, time (h), ambient temperature, indoor relative humidity, and day of the week to help simulate the air-cleaning effect of this prototype. The model can approximately predict the air quality trend, and future improvements may be made to improve its accuracy.
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Affiliation(s)
- Peiyang Li
- Department of Agricultural and Biosystems Engineering, Iowa State University, Ames, IA, USA
| | - Jacek A Koziel
- Department of Agricultural and Biosystems Engineering, Iowa State University, Ames, IA, USA; Livestock Nutrient Management Research Unit, USDA-ARS Conservation & Production Research Laboratory, Bushland, TX, USA.
| | | | - Nubia Macedo
- Department of Veterinary Diagnostic and Production Animal Medicine, Iowa State University, Ames, IA, USA
| | - Jeffrey J Zimmerman
- Department of Veterinary Diagnostic and Production Animal Medicine, Iowa State University, Ames, IA, USA
| | - Danielle Wrzesinski
- Department of Agricultural and Biosystems Engineering, Iowa State University, Ames, IA, USA
| | - Erin Sobotka
- Department of Agricultural and Biosystems Engineering, Iowa State University, Ames, IA, USA
| | - Mateo Balderas
- Department of Mechanical Engineering, Iowa State University, Ames, IA, USA
| | - William B Walz
- Department of Agricultural and Biosystems Engineering, Iowa State University, Ames, IA, USA
| | - Dongjie Liu
- Department of Biomedical Sciences, Iowa State University, Ames, IA, USA
| | - Bauyrzhan Yedilbayev
- Department of Agricultural and Biosystems Engineering, Iowa State University, Ames, IA, USA; Department of Geography and Environmental Sciences, al-Farabi Kazakh National University, Almaty, Kazakhstan
| | - Brett C Ramirez
- Department of Agricultural and Biosystems Engineering, Iowa State University, Ames, IA, USA
| | - William S Jenks
- Department of Chemistry, Iowa State University, Ames, IA, USA
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Messina G, Amodeo D, Taddeini F, De Palma I, Puccio A, Cevenini G. Wind of change: Better air for microbial environmental control. CASE STUDIES IN CHEMICAL AND ENVIRONMENTAL ENGINEERING 2022; 6:100240. [PMID: 37520926 PMCID: PMC9339158 DOI: 10.1016/j.cscee.2022.100240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Revised: 07/22/2022] [Accepted: 07/25/2022] [Indexed: 08/01/2023]
Abstract
Background The COVID19 epidemic highlighted the importance of air in the transmission of pathogens. Air disinfection is one of the key points to reduce the risk of transmission both in the health sector and in public, civil and industrial environments. All bacteria and viruses tested to date can be inactivated by UV-C rays. Laboratory tested UV-C systems are increasingly popular and proposed as effective technologies for air purification; few studies have evaluated their performance in populated indoor environments. The aim of this investigation was to evaluate the effectiveness of a UV-C disinfection system for air in a real working context. Methods This experimental study was conducted between December 2020 and February 2021 in an office of the Department of Molecular and Developmental Medicine of the University of Siena, Italy. A pre-final version air purifier (Cleaning Air T12), capable of treating 210 m3/h of air, was first tested for its ability to filter particulates and reduce microbial air contamination in the absence of people. Subsequently, the experiments were conducted in the presence of 3-5 subjects who worked for several hours in an office. During the tests, microbiological samples of air were collected in real time, switching the system on and off periodically. Air samples were collected and incubated on Petri dishes at 36 °C and 22 °C. Statistical analysis was performed with Stata 16 software assuming a significance level of 95%. An interpolating model was identified to describe the dynamics of contamination reduction when the device operates. Results Preliminary tests showed a significant 62.5% reduction in Colony-Forming Units (CFUs) with 36 °C incubation. Reductions in the particulate component were also observed. In the main test, comparison of CFU data, between the device-on phase (90 min) and the subsequent device-off phase (60 min), showed statistically significant increase (p = 0.001) of environmental contamination passing from a mean of 86.6 (65.8-107.4) to 171.1 (143.9-198.3) CFU/m3, that is a rise of about 100%. The interpolating model exhibited a good fit of CFU reduction trend with the device on. Conclusions The system, which mainly uses UV-C lamps for disinfection, was able to significantly reduce environmental and human contamination in real time. Experimental tests have shown that as soon as the device is switched off, after at least half an hour of operation, the healthiness of the air decreases drastically within 10 minutes, bringing the airborne microbial contamination (induced by the presence of operators in the environment) to levels even higher than 150% of the last value with the device on. Re-engineering strategies for system improvement were also discussed.
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Affiliation(s)
- G Messina
- Post Graduate School of Public Health, University of Siena, Italy
- Department of Molecular and Developmental Medicine, University of Siena, Italy
| | - D Amodeo
- Department of Molecular and Developmental Medicine, University of Siena, Italy
| | - F Taddeini
- Post Graduate School of Public Health, University of Siena, Italy
| | - I De Palma
- Department of Molecular and Developmental Medicine, University of Siena, Italy
| | - A Puccio
- Department of Medical Biotechnologies, Bioengineering Lab, University of Siena, Italy
| | - G Cevenini
- Department of Medical Biotechnologies, Bioengineering Lab, University of Siena, Italy
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Kowalski W, Moeller R, Walsh TJ, Petraitis V, Passman FJ. Ultraviolet disinfection efficacy test method using bacteria monolayers. J Microbiol Methods 2022; 200:106541. [PMID: 35870538 DOI: 10.1016/j.mimet.2022.106541] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Revised: 07/13/2022] [Accepted: 07/14/2022] [Indexed: 11/28/2022]
Abstract
Monolayers of bacterial cells of Staphylococcus aureus and Pseudomonas aeruginosa were inoculated on glass slide carriers using an automated inoculum spray deposition system. The use of bacterial monolayers allows for control of critical variables for testing and verification of light-based disinfection technologies. This approach avoids the variability associated with manual inoculation and high inoculum titers, which can engender clustering of cells and the associated photoprotection that clustering incurs. The use of glass slide carriers avoids problems caused by irregular microscopic surface features, which can impact the efficacy evaluation of light-based disinfection technologies. Scanning electron micrographic (SEM) imaging was used to verify the surface topography and the presence of monolayers. The spray deposition method produced a mean density of >106 colony forming units (CFU) per carrier. The inoculated carriers were exposed to ultraviolet light for 120 s from a focused multivector ultraviolet (FMUV) light system. A mean log CFU reduction of 4.8 was achieved for S. aureus (p < 0.0001). A mean log CFU reduction of 5.1 was achieved for P. aeruginosa (p < 0.0001). The test method presented herein will facilitate increased accuracy in the measurement of ultraviolet susceptibility rate constants.
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Affiliation(s)
| | - Ralf Moeller
- German Aerospace Center (DLR e.V.), Institute of Aerospace Medicine, Radiation Biology Department, Aerospace Microbiology Research Group, Cologne, Germany
| | - Thomas J Walsh
- Infectious Diseases Translational Research Laboratory, Transplantation-Oncology Infectious Diseases Program, Weill Cornell Medicine of Cornell University, New York City, NY, USA
| | - Vidmantas Petraitis
- Infectious Diseases Translational Research Laboratory, Transplantation-Oncology Infectious Diseases Program, Weill Cornell Medicine of Cornell University, New York City, NY, USA
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Caggiano G, Lopuzzo M, Spagnuolo V, Diella G, Triggiano F, D’Ambrosio M, Trerotoli P, Marcotrigiano V, Barbuti G, Sorrenti GT, Magarelli P, Sorrenti DP, Napoli C, Montagna MT. Investigations on the Efficacy of Ozone as an Environmental Sanitizer in Large Supermarkets. Pathogens 2022; 11:pathogens11050608. [PMID: 35631128 PMCID: PMC9147425 DOI: 10.3390/pathogens11050608] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2022] [Revised: 05/18/2022] [Accepted: 05/20/2022] [Indexed: 11/16/2022] Open
Abstract
Awareness of the importance of the microbial contamination of air and surfaces has increased significantly during the COVID-19 pandemic. The aim of this study was to evaluate the presence of bacteria and fungi in the air and on surfaces within some critical areas of large supermarkets with and without an ozonation system. Surveys were conducted in four supermarkets belonging to the same commercial chain of an Apulian city in June 2021, of which two (A and B) were equipped with an ozonation system, and two (C and D) did not have any air-diffused remediation treatment. There was a statistically significant difference in the total bacterial count (TBC) and total fungal count (TFC) in the air between A/B and C/D supermarkets (p = 0.0042 and p = 0.0002, respectively). Regarding surfaces, a statistically significant difference in TBC emerged between A/B and C/D supermarkets (p = 0.0101). To the best of our knowledge, this is the first study evaluating the effect of ozone on commercial structures in Italy. Future investigations, supported by a multidisciplinary approach, will make it possible to deepen the knowledge on this method of sanitation, in light of any other epidemic/pandemic waves.
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Affiliation(s)
- Giuseppina Caggiano
- Interdisciplinary Department of Medicine, Hygiene Section, University of Bari Aldo Moro, Piazza G. Cesare 11, 70124 Bari, Italy; (G.D.); (P.T.); (M.T.M.)
- Correspondence: ; Tel.: +39-(0)-80-5478-475
| | - Marco Lopuzzo
- Department of Biomedical Science and Human Oncology, University of Bari Aldo Moro, Piazza G. Cesare 11, 70124 Bari, Italy; (M.L.); (V.S.); (F.T.); (M.D.); (G.B.)
| | - Valentina Spagnuolo
- Department of Biomedical Science and Human Oncology, University of Bari Aldo Moro, Piazza G. Cesare 11, 70124 Bari, Italy; (M.L.); (V.S.); (F.T.); (M.D.); (G.B.)
| | - Giusy Diella
- Interdisciplinary Department of Medicine, Hygiene Section, University of Bari Aldo Moro, Piazza G. Cesare 11, 70124 Bari, Italy; (G.D.); (P.T.); (M.T.M.)
| | - Francesco Triggiano
- Department of Biomedical Science and Human Oncology, University of Bari Aldo Moro, Piazza G. Cesare 11, 70124 Bari, Italy; (M.L.); (V.S.); (F.T.); (M.D.); (G.B.)
| | - Marilena D’Ambrosio
- Department of Biomedical Science and Human Oncology, University of Bari Aldo Moro, Piazza G. Cesare 11, 70124 Bari, Italy; (M.L.); (V.S.); (F.T.); (M.D.); (G.B.)
| | - Paolo Trerotoli
- Interdisciplinary Department of Medicine, Hygiene Section, University of Bari Aldo Moro, Piazza G. Cesare 11, 70124 Bari, Italy; (G.D.); (P.T.); (M.T.M.)
| | - Vincenzo Marcotrigiano
- Department of Prevention, Food Hygiene and Nutrition Service, Local Health Unit BT, Barletta-Andria-Trani, 76125 Trani, Italy; (V.M.); (G.T.S.); (P.M.); (D.P.S.)
| | - Giovanna Barbuti
- Department of Biomedical Science and Human Oncology, University of Bari Aldo Moro, Piazza G. Cesare 11, 70124 Bari, Italy; (M.L.); (V.S.); (F.T.); (M.D.); (G.B.)
| | - Giovanni Trifone Sorrenti
- Department of Prevention, Food Hygiene and Nutrition Service, Local Health Unit BT, Barletta-Andria-Trani, 76125 Trani, Italy; (V.M.); (G.T.S.); (P.M.); (D.P.S.)
| | - Pantaleo Magarelli
- Department of Prevention, Food Hygiene and Nutrition Service, Local Health Unit BT, Barletta-Andria-Trani, 76125 Trani, Italy; (V.M.); (G.T.S.); (P.M.); (D.P.S.)
| | - Domenico Pio Sorrenti
- Department of Prevention, Food Hygiene and Nutrition Service, Local Health Unit BT, Barletta-Andria-Trani, 76125 Trani, Italy; (V.M.); (G.T.S.); (P.M.); (D.P.S.)
| | - Christian Napoli
- Department of Medical Surgical Sciences and Translational Medicine, Sapienza University of Rome, 00189 Rome, Italy;
| | - Maria Teresa Montagna
- Interdisciplinary Department of Medicine, Hygiene Section, University of Bari Aldo Moro, Piazza G. Cesare 11, 70124 Bari, Italy; (G.D.); (P.T.); (M.T.M.)
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