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Cavallaro A, Rhoads WJ, Sylvestre É, Marti T, Walser JC, Hammes F. Legionella relative abundance in shower hose biofilms is associated with specific microbiome members. FEMS MICROBES 2023; 4:xtad016. [PMID: 37705999 PMCID: PMC10496943 DOI: 10.1093/femsmc/xtad016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Revised: 07/13/2023] [Accepted: 08/14/2023] [Indexed: 09/15/2023] Open
Abstract
Legionella are natural inhabitants of building plumbing biofilms, where interactions with other microorganisms influence their survival, proliferation, and death. Here, we investigated the associations of Legionella with bacterial and eukaryotic microbiomes in biofilm samples extracted from 85 shower hoses of a multiunit residential building. Legionella spp. relative abundance in the biofilms ranged between 0-7.8%, of which only 0-0.46% was L. pneumophila. Our data suggest that some microbiome members were associated with high (e.g. Chthonomonas, Vrihiamoeba) or low (e.g. Aquabacterium, Vannella) Legionella relative abundance. The correlations of the different Legionella variants (30 Zero-Radius OTUs detected) showed distinct patterns, suggesting separate ecological niches occupied by different Legionella species. This study provides insights into the ecology of Legionella with respect to: (i) the colonization of a high number of real shower hoses biofilm samples; (ii) the ecological meaning of associations between Legionella and co-occurring bacterial/eukaryotic organisms; (iii) critical points and future directions of microbial-interaction-based-ecological-investigations.
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Affiliation(s)
- Alessio Cavallaro
- Department of Environmental Microbiology, Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
- Department of Environmental Systems Science, Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, 8092 Zürich, Switzerland
| | - William J Rhoads
- Department of Environmental Microbiology, Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
| | - Émile Sylvestre
- Department of Environmental Microbiology, Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
| | - Thierry Marti
- Department of Environmental Microbiology, Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
- Department of Environmental Systems Science, Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, 8092 Zürich, Switzerland
| | - Jean-Claude Walser
- Department of Environmental Systems Science, Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, 8092 Zürich, Switzerland
- Department of Environmental Systems Science, Genetic Diversity Centre (GDC), ETH Zurich, 8092 Zürich, Switzerland
| | - Frederik Hammes
- Department of Environmental Microbiology, Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
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Shen Y, Haig SJ, Prussin AJ, LiPuma JJ, Marr LC, Raskin L. Shower water contributes viable nontuberculous mycobacteria to indoor air. PNAS NEXUS 2022; 1:pgac145. [PMID: 36712351 PMCID: PMC9802317 DOI: 10.1093/pnasnexus/pgac145] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Accepted: 11/07/2022] [Indexed: 11/11/2022]
Abstract
Nontuberculous mycobacteria (NTM) are frequently present in municipal drinking water and building plumbing, and some are believed to cause respiratory tract infections through inhalation of NTM-containing aerosols generated during showering. However, the present understanding of NTM transfer from water to air is insufficient to develop NTM risk mitigation strategies. This study aimed to characterize the contribution of shower water to the abundance of viable NTM in indoor air. Shower water and indoor air samples were collected, and 16S rRNA and rpoB genes were sequenced. The sequencing results showed that running the shower impacted the bacterial community structure and NTM species composition in indoor air by transferring certain bacteria from water to air. A mass balance model combined with NTM quantification results revealed that on average 1/132 and 1/254 of NTM cells in water were transferred to air during 1 hour of showering using a rain and massage showerhead, respectively. A large fraction of the bacteria transferred from water to air were membrane-damaged, i.e. they had compromised membranes based on analysis by live/dead staining and flow cytometry. However, the damaged NTM in air were recoverable as shown by growth in a culture medium mimicking the respiratory secretions of people with cystic fibrosis, implying a potential infection risk by NTM introduced to indoor air during shower running. Among the recovered NTM, Mycobacterium mucogenicum was the dominant species as determined by rpoB gene sequencing. Overall, this study lays the groundwork for future pathogen risk management and public health protection in the built environment.
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Affiliation(s)
| | | | - Aaron J Prussin
- Department of Civil and Environmental Engineering, Virginia Tech, 418 Durham Hall, Blacksburg, VA 24061, USA
| | - John J LiPuma
- Department of Pediatrics, University of Michigan Medical School, 1500 E. Medical Center Dr., Ann Arbor, MI 48109, USA
| | - Linsey C Marr
- Department of Civil and Environmental Engineering, Virginia Tech, 418 Durham Hall, Blacksburg, VA 24061, USA
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Dietrich AM, Yao W, Gallagher DL. Exposure at the indoor water-air interface: Fill water constituents and the consequent air emissions from ultrasonic humidifiers: A systematic review. INDOOR AIR 2022; 32:e13129. [PMID: 36437646 PMCID: PMC9828259 DOI: 10.1111/ina.13129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Revised: 09/24/2022] [Accepted: 09/26/2022] [Indexed: 06/16/2023]
Abstract
This systematic review investigates the emissions from ultrasonic humidifiers (e.g., cool mist humidifiers) within indoor air environments, namely soluble and insoluble metals and minerals as well as microorganisms and one organic chemical biocide. Relationships between ultrasonic humidifier fill water quality and the emissions in indoor air are studied, and associated potential adverse health outcomes are discussed. Literature from January 1, 1980, to February 1, 2022, was searched from online databases of PubMed, Web of Science, and Scopus to produce 27 articles. The results revealed clear positive proportional relationships of the concentration of microorganisms and soluble metals/minerals between fill water qualities and emitted airborne particles, for both microbial (n = 9) and inorganic (n = 15) constituents. When evaluating emissions and the consequent health outcomes, ventilation rates of specific exposure scenarios affect the concentrations of emitted particles. Thus, well-ventilated rooms may alleviate inhalation risks when the fill water in ultrasonic humidifiers contains microorganisms and soluble metals/minerals. Case reports (n = 3) possibly due to the inhalation of particles from ultrasonic humidifier include hypersensitivity pneumonitis in adults and a 6-month infant; the young infant exhibited nonreversible mild obstructive ventilator defect. In summary, related literature indicated correlation between fill water quality of ultrasonic humidifier and emitted particles in air quality, and inhalation of the emitted particles may cause undesirable health outcomes of impaired respiratory functions in adults and children.
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Affiliation(s)
- Andrea M. Dietrich
- Department of Civil and Environmental EngineeringVirginia TechBlacksburgVirginiaUSA
| | - Wenchuo Yao
- Department of Civil and Environmental EngineeringVirginia TechBlacksburgVirginiaUSA
| | - Daniel L. Gallagher
- Department of Civil and Environmental EngineeringVirginia TechBlacksburgVirginiaUSA
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Kermani M, Chegini Z, Mirkalantari S, Norzaee S. Assessment of the risk of Legionella pneumophila in water distribution systems in hospitals of Tehran city. ENVIRONMENTAL MONITORING AND ASSESSMENT 2022; 194:842. [PMID: 36175694 DOI: 10.1007/s10661-022-10469-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Accepted: 09/10/2022] [Indexed: 06/16/2023]
Abstract
When a sensitive host inhales aerosols containing these bacteria, Legionella infection occurs. Therefore, monitoring and assessing Legionella in the environment and water distribution systems of such places are critical due to the prone population in hospitals. However, the health risks of Legionella bacteria in the environment are not adequately evaluated. In this study, for hospitalized patients, we performed a quantitative health risk assessment of Legionella in selected hospitals in Tehran city using two scenarios of shower and toilet faucet exposure. This study identified Legionella in 38 cases (38%) out of 100 samples collected from toilet faucets and showers in 8 hospitals. The information gathered was used for quantitative microbial risk assessment (QMRA). The microbial load transmitted by inhalation was calculated using the concentration of Legionella in water. Other exposure parameters (inhalation rate and exposure time) were obtained using information from other studies and the median length of hospital stay (3.6 days). The exponential model was used to estimate the risk of infection (γ = 0.06) due to Legionella pneumophila (L. pneumophila) inhalation for each exposure event. For the mean concentration obtained for Legionella (103 CFU/L), the risk of infection for toilet faucets and showers was in the range of 0.23-2.3 and 3.5-21.9, respectively, per 10,000 hospitalized patients. The results were compared with the tolerable risk level of infection determined by the US EPA and WHO. The risk values exceeded the WHO values for waterborne pathogens in hospitals in both exposure scenarios. As a result, our QMRA results based on monitoring data showed that despite using treated water (from distribution networks in the urban areas) by hospitals, 38% of the samples were contaminated with Legionella, and faucets and showers can be sources of Legionella transmission. Hence, to protect the health of hospitalized patients, the risk of Legionella infection should be considered.
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Affiliation(s)
- Majid Kermani
- Research Center for Environmental Health Technology, Iran University of Medical Sciences, Tehran, Iran
- Department of Environmental Health Engineering, School of Public Health, Iran University of Medical Sciences, Tehran, Iran
| | - Zahra Chegini
- Department of Microbiology, School of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran
| | - Shiva Mirkalantari
- Department of Microbiology, School of Medicine, Iran University of Medical Sciences, Tehran, Iran.
| | - Samira Norzaee
- Research Center for Environmental Health Technology, Iran University of Medical Sciences, Tehran, Iran.
- Department of Environmental Health Engineering, School of Public Health, Iran University of Medical Sciences, Tehran, Iran.
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Evaluation of a Most Probable Number Method for Detection and Quantification of Legionella pneumophila. Pathogens 2022; 11:pathogens11070789. [PMID: 35890033 PMCID: PMC9324539 DOI: 10.3390/pathogens11070789] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Revised: 07/02/2022] [Accepted: 07/07/2022] [Indexed: 11/17/2022] Open
Abstract
The detection and enumeration of Legionella pneumophila (L. pneumophila) in water is crucial for water quality management, human health and has been a research hotspot worldwide. Due to the time-consuming and complicated operation of the plate culture method, it is necessary to adopt a fast and effective method for application. The present study aimed to comprehensively evaluate the performance and applicability of the MPN method by comparing its qualitative and quantitative results with the GB/T 18204.5-2013 and ISO methods, respectively. The qualitative results showed that 372 samples (53%) were negative for both methods; 315 samples (45%) were positively determined by the MPN method, compared with 211 samples (30%) using GB/T 18204.5-2013. The difference in the detection rate between the two methods was statistically significant. In addition, the quantitative results showed that the concentration of L. pneumophila by the MPN method was greater than ISO 11731 and the difference was statistically significant. However, the two methods were different but highly correlated (r = 0.965, p < 0.001). The specificity and sensitivity of the MPN method were 89.85% and 95.73%, respectively. Overall, the results demonstrated that the MPN method has higher sensitivity, a simple operation process and good application prospects in the routine monitoring of L. pneumophila from water samples.
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Xu PC, Zhang CM, Wang XC. Numerical simulation for spatial distribution of water aerosol produced from nozzle spray and health risk related to Legionella pneumophila in spray scenarios. WATER RESEARCH 2022; 216:118304. [PMID: 35325820 DOI: 10.1016/j.watres.2022.118304] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 02/22/2022] [Accepted: 03/14/2022] [Indexed: 06/14/2023]
Abstract
Water spray facilities are widely used in public places for sprinkling or beautifying the environment. However, the potential health risk induced by water aerosols increasingly calls for attention. In this study, the spatial distribution of water aerosols was investigated through the molecular sieve adsorption method, and predicted by discrete phase model (DPM). On this basis, the health risk regarding Legionella pneumophila for specific spray scenarios was evaluated by quantitative microbial risk assessment (QMRA). The results showed that the original droplet size can be described by the Rosin_Rommaler distribution (R2>0.99). The spatial distribution of water aerosols produced from a nozzle spray can be well predicted by the DPM. The concentration of water aerosols showed a sharp decline within 5 m from the nozzle and was not significantly different within 5 m (p>0.05) as for various spray scenarios. However, the difference was significant outside 5 m (p<0.05). Furthermore, a safe contact distance of exceeding 8 m is proposed in spray scenarios considering the risk threshold of 0.0001. Sensitivity analysis demonstrated the concentration of Legionella pneumophila in water aerosols as the critical factor affecting the health risk.
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Affiliation(s)
- Peng-Cheng Xu
- School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China; Key Lab of Northwest Water Resource, Environment and Ecology, Ministry of Education, Xi'an University of Architecture and Technology, Xi'an, 710055, China; Shaanxi Key Laboratory of Environmental Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China; International Science and Technology Cooperation Center for Urban Alternative Water Resources Development, Xi'an University of Architecture and Technology, Xi'an, 710055, China
| | - Chong-Miao Zhang
- School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China; Key Lab of Northwest Water Resource, Environment and Ecology, Ministry of Education, Xi'an University of Architecture and Technology, Xi'an, 710055, China; Shaanxi Key Laboratory of Environmental Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China; International Science and Technology Cooperation Center for Urban Alternative Water Resources Development, Xi'an University of Architecture and Technology, Xi'an, 710055, China.
| | - Xiaochang C Wang
- School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China; Key Lab of Northwest Water Resource, Environment and Ecology, Ministry of Education, Xi'an University of Architecture and Technology, Xi'an, 710055, China; International Science and Technology Cooperation Center for Urban Alternative Water Resources Development, Xi'an University of Architecture and Technology, Xi'an, 710055, China
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Inactivation of airborne microbial contaminants by a heat-pump-driven liquid-desiccant air-conditioning system. JOURNAL OF BUILDING ENGINEERING 2022; 50:104157. [PMCID: PMC8813195 DOI: 10.1016/j.jobe.2022.104157] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2021] [Revised: 01/21/2022] [Accepted: 01/31/2022] [Indexed: 04/25/2024]
Abstract
The COVID-19 pandemic has led to increasing interest in controlling airborne virus transmission during the operation of air-conditioning systems. Therefore, beyond an examination of the ability of liquid-desiccant material itself to inactivate microbes, a heat-pump-driven liquid-desiccant air-conditioning system was proposed and constructed to experimentally investigate the effect of liquid-desiccant solution on the inactivation of airborne bacteria and fungi in various air-conditioning processes. The proposed system comprises a liquid-desiccant unit to dehumidify or humidify process air using a desiccant-solution and heat-pump unit to cool or heat it and accommodate solution thermal loads. The decrease in the concentration of airborne bacteria and fungi before and after passing through the system (i.e., inactivation efficiency) were compared for the base, summer, and winter operating modes. The results indicated that airborne fungi were less inactivated than bacteria because they possess more stress-resistant cellular structures that resist inactivation. During the air-conditioning processes in both the summer and winter operating modes, the bacterial and fungal inactivation efficiencies improved compared to the base mode owing to the contact with desiccant solution. The higher solution flow rate and solution temperature improved the bacterial inactivation efficiency by 27% for the winter compared to the summer mode. Conversely, because of possible growth of fungi in the heated and humidified supply air in the winter, the fungal inactivation efficiency improved by only 1.5% for the winter compared to the summer mode. In conclusion, the proposed system can contribute to control the airborne transmission of microbial contaminants while operating air-conditioning systems.
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Quantitative Microbial Risk Assessment Applied to Legionella Contamination on Long-Distance Public Transport. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2022; 19:ijerph19041960. [PMID: 35206148 PMCID: PMC8872098 DOI: 10.3390/ijerph19041960] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Revised: 02/07/2022] [Accepted: 02/09/2022] [Indexed: 01/01/2023]
Abstract
The quantitative microbial risk assessment (QMRA) framework is used for assessing health risk coming from pathogens in the environment. In this paper, we used QMRA to evaluate the infection risk of L. pneumophila attributable to sink usage in a toilet cabin on Italian long-distance public transportation (LDT). LDT has water distribution systems with risk points for Legionella proliferation, as well as premise plumbing for drinking water, but they are not considered for risk assessment. Monitoring data revealed that approximately 55% of water samples (217/398) were positive for L. pneumophila, and the most frequently isolated was L. pneumophila sg1 (64%, 139/217); therefore, such data were fitted to the best probability distribution function to be used as a stochastic variable in the QMRA model. Then, a sink-specific aerosolization ratio was applied to calculate the inhaled dose, also considering inhalation rate and exposure time, which were used as stochastic parameters based on literature data. At L. pneumophila sg1 concentration ≤100 CFU/L, health risk was approximately 1 infection per 1 million exposures, with an increase of up to 5 infections per 10,000 exposures when the concentrations were ≥10,000 CFU/L. Our QMRA results showed a low Legionella infection risk from faucets on LDT; however, it deserves consideration since LDT can be used by people highly susceptible for the development of a severe form of the disease, owing to their immunological status or other predisposing factors. Further investigations could also evaluate Legionella-laden aerosols from toilet flushing.
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Zhang C, Lu J. Legionella: A Promising Supplementary Indicator of Microbial Drinking Water Quality in Municipal Engineered Water Systems. FRONTIERS IN ENVIRONMENTAL SCIENCE 2021; 9:1-22. [PMID: 35004706 PMCID: PMC8740890 DOI: 10.3389/fenvs.2021.684319] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Opportunistic pathogens (OPs) are natural inhabitants and the predominant disease causative biotic agents in municipal engineered water systems (EWSs). In EWSs, OPs occur at high frequencies and concentrations, cause drinking-water-related disease outbreaks, and are a major factor threatening public health. Therefore, the prevalence of OPs in EWSs represents microbial drinking water quality. Closely or routinely monitoring the dynamics of OPs in municipal EWSs is thus critical to ensuring drinking water quality and protecting public health. Monitoring the dynamics of conventional (fecal) indicators (e.g., total coliforms, fecal coliforms, and Escherichia coli) is the customary or even exclusive means of assessing microbial drinking water quality. However, those indicators infer only fecal contamination due to treatment (e.g., disinfection within water utilities) failure and EWS infrastructure issues (e.g., water main breaks and infiltration), whereas OPs are not contaminants in drinking water. In addition, those indicators appear in EWSs at low concentrations (often absent in well-maintained EWSs) and are uncorrelated with OPs. For instance, conventional indicators decay, while OPs regrow with increasing hydraulic residence time. As a result, conventional indicators are poor indicators of OPs (the major aspect of microbial drinking water quality) in EWSs. An additional or supplementary indicator that can well infer the prevalence of OPs in EWSs is highly needed. This systematic review argues that Legionella as a dominant OP-containing genus and natural inhabitant in EWSs is a promising candidate for such a supplementary indicator. Through comprehensively comparing the behavior (i.e., occurrence, growth and regrowth, spatiotemporal variations in concentrations, resistance to disinfectant residuals, and responses to physicochemical water quality parameters) of major OPs (e.g., Legionella especially L. pneumophila, Mycobacterium, and Pseudomonas especially P. aeruginosa), this review proves that Legionella is a promising supplementary indicator for the prevalence of OPs in EWSs while other OPs lack this indication feature. Legionella as a dominant natural inhabitant in EWSs occurs frequently, has a high concentration, and correlates with more microbial and physicochemical water quality parameters than other common OPs. Legionella and OPs in EWSs share multiple key features such as high disinfectant resistance, biofilm formation, proliferation within amoebae, and significant spatiotemporal variations in concentrations. Therefore, the presence and concentration of Legionella well indicate the presence and concentrations of OPs (especially L. pneumophila) and microbial drinking water quality in EWSs. In addition, Legionella concentration indicates the efficacies of disinfectant residuals in EWSs. Furthermore, with the development of modern Legionella quantification methods (especially quantitative polymerase chain reactions), monitoring Legionella in ESWs is becoming easier, more affordable, and less labor-intensive. Those features make Legionella a proper supplementary indicator for microbial drinking water quality (especially the prevalence of OPs) in EWSs. Water authorities may use Legionella and conventional indicators in combination to more comprehensively assess microbial drinking water quality in municipal EWSs. Future work should further explore the indication role of Legionella in EWSs and propose drinking water Legionella concentration limits that indicate serious public health effects and require enhanced treatment (e.g., booster disinfection).
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Affiliation(s)
- Chiqian Zhang
- Pegasus Technical Services, Inc., Cincinnati, OH, United States
| | - Jingrang Lu
- Office of Research and Development, United States Environmental Protection Agency, Cincinnati, OH, United States
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Assaidi A, Soummane A, Ellouali M, Latrache H, Timinouni M, Zahir H, Mliji EM. Environmental surveillance of Legionella pneumophila in hot water systems of hotels in Morocco. JOURNAL OF WATER AND HEALTH 2021; 19:855-863. [PMID: 34665777 DOI: 10.2166/wh.2021.175] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
OBJECTIVE Environmental monitoring of Legionella in hot water systems of hotels in Morocco was performed during the period from January 2016 to April 2018. A total of 149 water samples from 118 different hotels were analyzed. METHODS A total of 149 water samples from 118 different hotels were analyzed. Possible risk factors were prospectively recorded, and data were analyzed in connection with building and plumbing systems characteristics. Data about building and risk factors were collected through a questionnaire survey. RESULTS Out of the 149 samples, 77(51.7%) were positive for L. pneumophila. Serological typing of the isolates revealed that 54 (70.1%) are L. pneumophila serogroup 2-15 and 23 (29.9%) are L. pneumophila serogroup 1. 56.8% of all buildings were colonized by L. pneumophila. Counts were over 1,000 CFU/L in 44%. Contamination was strongly correlated with temperature in the circulation, the age of the premise plumbing and the size of the building. CONCLUSIONS The results showed a relevant exposure to L. pneumophila in the community and the identified risk factors can serve as indicators for risk assessment and relevant actions.
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Affiliation(s)
- Abdelwahid Assaidi
- Laboratory of Bioprocess and Biointerfaces, Faculty of Sciences and Technics, Sultan Moulay Slimane University, Beni Mellal, Morocco; Laboratory of Water Microbiology and Environmental Hygiene, Institut Pasteur du Maroc, Casablanca, Morocco E-mail:
| | - Afaf Soummane
- Laboratory of Water Microbiology and Environmental Hygiene, Institut Pasteur du Maroc, Casablanca, Morocco E-mail:
| | - Mostafa Ellouali
- Laboratory of Bioprocess and Biointerfaces, Faculty of Sciences and Technics, Sultan Moulay Slimane University, Beni Mellal, Morocco
| | - Hassan Latrache
- Laboratory of Bioprocess and Biointerfaces, Faculty of Sciences and Technics, Sultan Moulay Slimane University, Beni Mellal, Morocco
| | - Mohammed Timinouni
- Laboratory of Water Microbiology and Environmental Hygiene, Institut Pasteur du Maroc, Casablanca, Morocco E-mail:
| | - Hafida Zahir
- Laboratory of Bioprocess and Biointerfaces, Faculty of Sciences and Technics, Sultan Moulay Slimane University, Beni Mellal, Morocco
| | - El Mostafa Mliji
- Laboratory of Water Microbiology and Environmental Hygiene, Institut Pasteur du Maroc, Casablanca, Morocco E-mail:
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Walker JT, McDermott PJ. Confirming the Presence of Legionella pneumophila in Your Water System: A Review of Current Legionella Testing Methods. J AOAC Int 2021; 104:1135-1147. [PMID: 33484265 PMCID: PMC8378878 DOI: 10.1093/jaoacint/qsab003] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 12/18/2020] [Accepted: 12/18/2020] [Indexed: 12/24/2022]
Abstract
Legionnaires' disease has been recognized since 1976 and Legionella pneumophila still accounts for more than 95% of cases. Approaches in countries, including France, suggest that focusing risk reduction specifically on L. pneumophila is an effective strategy, as detecting L. pneumophila has advantages over targeting multiple species of Legionella. In terms of assays, the historically accepted plate culture method takes 10 days for confirmed Legionella spp. results, has variabilities which affect trending and comparisons, requires highly trained personnel to identify colonies on a plate in specialist laboratories, and does not recover viable-but-non-culturable bacteria. PCR is sensitive, specific, provides results in less than 24 h, and determines the presence/absence of Legionella spp. and/or L. pneumophila DNA. Whilst specialist personnel and laboratories are generally required, there are now on-site PCR options, but there is no agreement on comparing genome units to colony forming units and action limits. Immunomagnetic separation assays are culture-independent, detect multiple Legionella species, and results are available in 24 h, with automated processing options. Field-use lateral flow devices provide presence/absence determination of L. pneumophila serogroup 1 where sufficient cells are present, but testing potable waters is problematic. Liquid culture most probable number (MPN) assays provide confirmed L. pneumophila results in 7 days that are equivalent to or exceed plate culture, are robust and reproducible, and can be performed in a variety of laboratory settings. MPN isolates can be obtained for epidemiological investigations. This accessible, non-technical review will be of particular interest to building owners, operators, risk managers, and water safety groups and will enable them to make informed decisions to reduce the risk of L. pneumophila.
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Hamilton KA, Kuppravalli A, Heida A, Joshi S, Haas CN, Verhougstraete M, Gerrity D. Legionnaires' disease in dental offices: Quantifying aerosol risks to dental workers and patients. JOURNAL OF OCCUPATIONAL AND ENVIRONMENTAL HYGIENE 2021; 18:378-393. [PMID: 34161202 DOI: 10.1080/15459624.2021.1939878] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Legionella pneumophila is an opportunistic bacterial respiratory pathogen that is one of the leading causes of drinking water outbreaks in the United States. Dental offices pose a potential risk for inhalation or aspiration of L. pneumophila due to the high surface area to volume ratio of dental unit water lines-a feature that is conducive to biofilm growth. This is coupled with the use of high-pressure water devices (e.g., ultrasonic scalers) that produce fine aerosols within the breathing zone. Prior research confirms that L. pneumophila occurs in dental unit water lines, but the associated human health risks have not been assessed. We aimed to: (1) synthesize the evidence for transmission and management of Legionnaires' disease in dental offices; (2) create a quantitative modeling framework for predicting associated L. pneumophila infection risk; and (3) highlight influential parameters and research gaps requiring further study. We reviewed outbreaks, management guidance, and exposure studies and used these data to parameterize a quantitative microbial risk assessment (QMRA) model for L. pneumophila in dental applications. Probabilities of infection for dental hygienists and patients were assessed on a per-exposure and annual basis. We also assessed the impact of varying ventilation rates and the use of personal protective equipment (PPE). Following an instrument purge (i.e., flush) and with a ventilation rate of 1.2 air changes per hour, the median per-exposure probability of infection for dental hygienists and patients exceeded a 1-in-10,000 infection risk benchmark. Per-exposure risks for workers during a purge and annual risks for workers wearing N95 masks did not exceed the benchmark. Increasing air change rates in the treatment room from 1.2 to 10 would achieve an ∼85% risk reduction, while utilization of N95 respirators would reduce risks by ∼95%. The concentration of L. pneumophila in dental unit water lines was a dominant parameter in the model and driver of risk. Future risk assessment efforts and refinement of microbiological control protocols would benefit from expanded occurrence datasets for L. pneumophila in dental applications.
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Affiliation(s)
- Kerry A Hamilton
- School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, Arizona
- The Biodesign Institute Center for Environmental Health Engineering, Arizona State University, Tempe, Arizona
| | - Aditya Kuppravalli
- School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, Arizona
- The Biodesign Institute Center for Environmental Health Engineering, Arizona State University, Tempe, Arizona
- BASIS Scottsdale High School, Scottsdale, Arizona
| | - Ashley Heida
- School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, Arizona
- The Biodesign Institute Center for Environmental Health Engineering, Arizona State University, Tempe, Arizona
| | - Sayalee Joshi
- School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, Arizona
- The Biodesign Institute Center for Environmental Health Engineering, Arizona State University, Tempe, Arizona
| | - Charles N Haas
- Department of Civil, Architectural, and Environmental Engineering, Drexel University, Philadelphia, Pennsylvania
| | - Marc Verhougstraete
- Mel and Enid Zuckerman College of Public Health, The University of Arizona, Tucson, Arizona
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Couturier J, Ginevra C, Nesa D, Adam M, Gouot C, Descours G, Campèse C, Battipaglia G, Brissot E, Beraud L, Ranc AG, Jarraud S, Barbut F. Transmission of Legionnaires' Disease through Toilet Flushing. Emerg Infect Dis 2021; 26:1526-1528. [PMID: 32568063 PMCID: PMC7323554 DOI: 10.3201/eid2607.190941] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
We describe 2 cases of healthcare-associated Legionnaires’ disease in patients in France hospitalized 5 months apart in the same room. Whole-genome sequencing analyses showed that clinical isolates from the patients and isolates from the room’s toilet clustered together. Toilet contamination by Legionella pneumophila could lead to a risk for exposure through flushing.
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Pascale MR, Mazzotta M, Salaris S, Girolamini L, Grottola A, Simone ML, Cordovana M, Bisognin F, Dal Monte P, Bucci Sabattini MA, Viggiani M, Cristino S. Evaluation of MALDI-TOF Mass Spectrometry in Diagnostic and Environmental Surveillance of Legionella Species: A Comparison With Culture and Mip-Gene Sequencing Technique. Front Microbiol 2021; 11:589369. [PMID: 33384668 PMCID: PMC7771186 DOI: 10.3389/fmicb.2020.589369] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Accepted: 11/19/2020] [Indexed: 12/19/2022] Open
Abstract
Legionella spp. are widespread bacteria in aquatic environments with a growing impact on human health. Between the 61 species, Legionella pneumophila is the most prevalent in human diseases; on the contrary, Legionella non-pneumophila species are less detected in clinical diagnosis or during environmental surveillance due to their slow growth in culture and the absence of specific and rapid diagnostic/analytical tools. Reliable and rapid isolate identification is essential to estimate the source of infection, to undertake containment measures, and to determine clinical treatment. Matrix-assisted laser desorption ionization–time-of-flight mass spectrometry (MALDI–TOF MS), since its introduction into the routine diagnostics of laboratories, represents a widely accepted method for the identification of different bacteria species, described in a few studies on the Legionella clinical and environmental surveillance. The focus of this study was the improvement of MALDI–TOF MS on Legionella non-pneumophila species collected during Legionella nosocomial and community surveillance. Comparative analysis with cultural and mip-gene sequencing results was performed. Moreover, a phylogenetic analysis was carried out to estimate the correlations amongst isolates. MALDI–TOF MS achieved correct species-level identification for 45.0% of the isolates belonging to the Legionella anisa, Legionella rubrilucens, Legionella feeleii, and Legionella jordanis species, displaying a high concordance with the mip-gene sequencing results. In contrast, less reliable identification was found for the remaining 55.0% of the isolates, corresponding to the samples belonging to species not yet included in the database. The phylogenetic analysis showed relevant differences inside the species, regruped in three main clades; among the Legionella anisa clade, a subclade with a divergence of 3.3% from the main clade was observed. Moreover, one isolate, identified as Legionella quinlivanii, displayed a divergence of 3.8% from the corresponding reference strain. However, these findings require supplementary investigation. The results encourage the implementation of MALDI–TOF MS in routine diagnostics and environmental Legionella surveillance, as it displays a reliable and faster identification at the species level, as well as the potential to identify species that are not yet included in the database. Moreover, phylogenetic analysis is a relevant approach to correlate the isolates and to track their spread, especially in unconventional reservoirs, where Legionella prevention is still underestimated.
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Affiliation(s)
- Maria Rosaria Pascale
- Department of Biological, Geological, and Environmental Sciences, University of Bologna, Bologna, Italy
| | - Marta Mazzotta
- Department of Biological, Geological, and Environmental Sciences, University of Bologna, Bologna, Italy
| | - Silvano Salaris
- Department of Biological, Geological, and Environmental Sciences, University of Bologna, Bologna, Italy
| | - Luna Girolamini
- Department of Biological, Geological, and Environmental Sciences, University of Bologna, Bologna, Italy
| | - Antonella Grottola
- Regional Reference Laboratory for Clinical Diagnosis of Legionellosis, Unit of Microbiology and Virology, Modena University Hospital, Modena, Italy
| | - Maria Luisa Simone
- Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy
| | - Miriam Cordovana
- Microbiology Unit-Department of Experimental, Diagnostic and Specialty Medicine, S. Orsola-Malpighi University Hospital, Bologna, Italy
| | - Francesco Bisognin
- Microbiology Unit-Department of Experimental, Diagnostic and Specialty Medicine, S. Orsola-Malpighi University Hospital, Bologna, Italy
| | - Paola Dal Monte
- Microbiology Unit-Department of Experimental, Diagnostic and Specialty Medicine, S. Orsola-Malpighi University Hospital, Bologna, Italy
| | | | | | - Sandra Cristino
- Department of Biological, Geological, and Environmental Sciences, University of Bologna, Bologna, Italy
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15
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Madera-García V, Mraz AL, López-Gálvez N, Weir MH, Werner J, Beamer PI, Verhougstraete MP. Legionella pneumophila as a Health Hazard to Miners: A Pilot Study of Water Quality and QMRA. WATER 2019; 11:1528. [PMID: 31583125 PMCID: PMC6776080 DOI: 10.3390/w11081528] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Legionella pneumophila (L. pneumophila), the causative agent of legionellosis, is an aquatic bacterium that grows in warm water. Humans are only presented with a health risk when aerosolized water containing L. pneumophila is inhaled. In mining operations, aerosolized water is used as dust control and as part of the drilling operations, a currently ignored exposure route. This study characterized L. pneumophila concentrations in the mine's non-potable water and the relationship between L. pneumophila and chlorine concentrations. These concentrations informed a quantitative microbial risk assessment (QMRA) model to estimate the infection risk to miners exposed to aerosolized water containing L. pneumophila. Fourteen water samples were collected from seven locations at a mine and analyzed for temperature, pH, chlorine, and L. pneumophila serogroup. Most samples (93%) tested positive for L. pneumophila cells. The faucet from the sprinkler system on the adit level (entrance to the underground mine levels) showed the highest concentration of L. pneumophila (8.35 × 104 MPN/L). Disability adjusted life years (DALYs) were estimated in the QMRA model and showed that the risk for all miners was significantly lower (p < 0.0001) with the ventilation system on than when the system was off. Our study showed that the use of a ventilation system at the adit level of the mine reduced the risk of infection with aerosolized L. pneumophila.
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Affiliation(s)
- Valerie Madera-García
- Department of Community, Environment, and Policy, Mel and Enid Zuckerman College of Public Health, The University of Arizona, Tucson, AZ 85724, USA
| | - Alexis L. Mraz
- Department of Epidemiology and Biostatistics, College of Public Health, Temple University, Philadelphia, PA 19122, USA
| | - Nicolás López-Gálvez
- Department of Community, Environment, and Policy, Mel and Enid Zuckerman College of Public Health, The University of Arizona, Tucson, AZ 85724, USA
| | - Mark H. Weir
- Division of Environmental Health Sciences, College of Public Health, The Ohio State University, Columbus, OH 43210, USA
| | - James Werner
- Department of Community, Environment, and Policy, Mel and Enid Zuckerman College of Public Health, The University of Arizona, Tucson, AZ 85724, USA
| | - Paloma I. Beamer
- Department of Community, Environment, and Policy, Mel and Enid Zuckerman College of Public Health, The University of Arizona, Tucson, AZ 85724, USA
| | - Marc P. Verhougstraete
- Department of Community, Environment, and Policy, Mel and Enid Zuckerman College of Public Health, The University of Arizona, Tucson, AZ 85724, USA
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16
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Sharaby Y, Rodríguez-Martínez S, Höfle MG, Brettar I, Halpern M. Quantitative microbial risk assessment of Legionella pneumophila in a drinking water supply system in Israel. THE SCIENCE OF THE TOTAL ENVIRONMENT 2019; 671:404-410. [PMID: 30933796 DOI: 10.1016/j.scitotenv.2019.03.287] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2019] [Revised: 03/13/2019] [Accepted: 03/19/2019] [Indexed: 06/09/2023]
Abstract
Legionella pneumophila cause human infections via inhalation of contaminated water aerosols, resulting in severe pneumonia. Legionella spp. prevalence was monitored in a drinking-water distribution system (DWDS) in Northern Israel. Five points (toilet faucets and showers) were sampled seasonally along a three years period. Toilet faucets and shower use, both generating aerosols, are known transmission routes for this pathogen and thus, present a potential health risk. Quantitative Microbial Risk Assessment (QMRA) was applied in order to assess the health risks posed by Legionella for these two exposure scenarios, while considering Legionella seasonality. The obtained results were compared with estimated tolerable risk levels of infection and of disease set by the USEPA and WHO. Both limits were expressed as Disability-Adjusted Life Years index (DALY) being 1 × 10-4 and 1 × 10-6, respectively. The QMRA revealed that the annual risk levels for both faucets and showers use exceeded the acceptable risk of infection with an average of 5.52 × 10-4 and 2.37 × 10-3 DALY'S per person per year, respectively. Annual risk levels were stable with no significant differences between the three years. Risk levels varied significantly between seasons by up to three orders of magnitude. Risk levels were highest during summer, autumn, and lowest during winter. The highest seasonal infection risk values were found in summer for both faucets and showers, which corresponded to 8.09 × 10-4 and 2.75 × 10-3 DALY'S per person per year, respectively. In conclusion, during summer and autumn there is a significant increase of the infection risk associated with exposure to Legionella-contaminated aerosols, in the studied water system. Public health assessment and prevention measures should focus on these seasons.
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Affiliation(s)
- Y Sharaby
- Department of Evolutionary and Environmental Biology, Faculty of Natural Sciences, University of Haifa, Haifa, Israel.
| | - S Rodríguez-Martínez
- Department of Evolutionary and Environmental Biology, Faculty of Natural Sciences, University of Haifa, Haifa, Israel
| | - M G Höfle
- Department of Vaccinology and Applied Microbiology, Helmholtz Centre for Infection Research (HZI), Braunschweig, Germany
| | - I Brettar
- Department of Vaccinology and Applied Microbiology, Helmholtz Centre for Infection Research (HZI), Braunschweig, Germany
| | - M Halpern
- Department of Evolutionary and Environmental Biology, Faculty of Natural Sciences, University of Haifa, Haifa, Israel; Department of Biology and Environment, Faculty of Natural Sciences, University of Haifa, Oranim, Tivon, Israel
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Hamilton KA, Hamilton MT, Johnson W, Jjemba P, Bukhari Z, LeChevallier M, Haas CN, Gurian PL. Risk-Based Critical Concentrations of Legionella pneumophila for Indoor Residential Water Uses. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:4528-4541. [PMID: 30629886 DOI: 10.1021/acs.est.8b03000] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Legionella spp. is a key contributor to the United States waterborne disease burden. Despite potentially widespread exposure, human disease is relatively uncommon, except under circumstances where pathogen concentrations are high, host immunity is low, or exposure to small-diameter aerosols occurs. Water quality guidance values for Legionella are available for building managers but are generally not based on technical criteria. To address this gap, a quantitative microbial risk assessment (QMRA) was conducted using target risk values in order to calculate corresponding critical concentrations on a per-fixture and aggregate (multiple fixture exposure) basis. Showers were the driving indoor exposure risk compared to sinks and toilets. Critical concentrations depended on the dose response model (infection vs clinical severity infection, CSI), risk target used (infection risk vs disability adjusted life years [DALY] on a per-exposure or annual basis), and fixture type (conventional vs water efficient or "green"). Median critical concentrations based on exposure to a combination of toilet, faucet, and shower aerosols ranged from ∼10-2 to ∼100 CFU per L and ∼101 to ∼103 CFU per L for infection and CSI dose response models, respectively. As infection model results for critical L. pneumophila concentrations were often below a feasible detection limit for culture-based assays, the use of CSI model results for nonhealthcare water systems with a 10-6 DALY pppy target (the more conservative target) would result in an estimate of 12.3 CFU per L (arithmetic mean of samples across multiple fixtures and/or over time). Single sample critical concentrations with a per-exposure-corrected DALY target at each conventional fixture would be 1.06 × 103 CFU per L (faucets), 8.84 × 103 CFU per L (toilets), and 14.4 CFU per L (showers). Using a 10-4 annual infection risk target would give a 1.20 × 103 CFU per L mean for multiple fixtures and single sample critical concentrations of 1.02 × 105, 8.59 × 105, and 1.40 × 103 CFU per L for faucets, toilets, and showers, respectively. Annual infection risk-based target estimates are in line with most current guidance documents of less than 1000 CFU per L, while DALY-based guidance suggests lower critical concentrations might be warranted in some cases. Furthermore, approximately <10 CFU per mL L. pneumophila may be appropriate for healthcare or susceptible population settings. This analysis underscores the importance of the choice of risk target as well as sampling program considerations when choosing the most appropriate critical concentration for use in public health guidance.
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Affiliation(s)
- Kerry A Hamilton
- School for Sustainable Engineering and the Built Environment , Arizona State University , Tempe , Arizona 85281 , United States
- The Biodesign Institute Center for Environmental Health Engineering , Arizona State University , Tempe , Arizona 85281 , United States
| | - Mark T Hamilton
- Microsoft Applied Artificial Intelligence Group , 1 Memorial Drive , Cambridge , Massachusetts 02142 , United States
| | - William Johnson
- American Water Research Laboratory , 213 Carriage Lane , Delran , New Jersey 08075 , United States
| | - Patrick Jjemba
- American Water Research Laboratory , 213 Carriage Lane , Delran , New Jersey 08075 , United States
| | - Zia Bukhari
- American Water Research Laboratory , 213 Carriage Lane , Delran , New Jersey 08075 , United States
| | - Mark LeChevallier
- American Water Research Laboratory , 213 Carriage Lane , Delran , New Jersey 08075 , United States
| | - Charles N Haas
- Drexel University , 3141 Chestnut Street , Philadelphia , Pennsylvania 19104 , United States
| | - P L Gurian
- Drexel University , 3141 Chestnut Street , Philadelphia , Pennsylvania 19104 , United States
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18
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Hamilton KA, Prussin AJ, Ahmed W, Haas CN. Outbreaks of Legionnaires’ Disease and Pontiac Fever 2006–2017. Curr Environ Health Rep 2018; 5:263-271. [DOI: 10.1007/s40572-018-0201-4] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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19
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Hamilton KA, Hamilton MT, Johnson W, Jjemba P, Bukhari Z, LeChevallier M, Haas CN. Health risks from exposure to Legionella in reclaimed water aerosols: Toilet flushing, spray irrigation, and cooling towers. WATER RESEARCH 2018; 134:261-279. [PMID: 29428779 DOI: 10.1016/j.watres.2017.12.022] [Citation(s) in RCA: 59] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 11/30/2017] [Accepted: 12/12/2017] [Indexed: 05/05/2023]
Abstract
The use of reclaimed water brings new challenges for the water industry in terms of maintaining water quality while increasing sustainability. Increased attention has been devoted to opportunistic pathogens, especially Legionella pneumophila, due to its growing importance as a portion of the waterborne disease burden in the United States. Infection occurs when a person inhales a mist containing Legionella bacteria. The top three uses for reclaimed water (cooling towers, spray irrigation, and toilet flushing) that generate aerosols were evaluated for Legionella health risks in reclaimed water using quantitative microbial risk assessment (QMRA). Risks are compared using data from nineteen United States reclaimed water utilities measured with culture-based methods, quantitative PCR (qPCR), and ethidium-monoazide-qPCR. Median toilet flushing annual infection risks exceeded 10-4 considering multiple toilet types, while median clinical severity infection risks did not exceed this value. Sprinkler and cooling tower risks varied depending on meteorological conditions and operational characteristics such as drift eliminator performance. However, the greatest differences between risk scenarios were due to 1) the dose response model used (infection or clinical severity infection) 2) population at risk considered (residential or occupational) and 3) differences in laboratory analytical method. Theoretical setback distances necessary to achieve a median annual infection risk level of 10-4 are proposed for spray irrigation and cooling towers. In both cooling tower and sprinkler cases, Legionella infection risks were non-trivial at potentially large setback distances, and indicate other simultaneous management practices could be needed to manage risks. The sensitivity analysis indicated that the most influential factors for variability in risks were the concentration of Legionella and aerosol partitioning and/or efficiency across all models, highlighting the importance of strategies to manage Legionella occurrence in reclaimed water.
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Affiliation(s)
- Kerry A Hamilton
- Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104, USA.
| | | | - William Johnson
- American Water Research Laboratory, 213 Carriage Lane, Delran, New Jersey 08075, USA
| | - Patrick Jjemba
- American Water Research Laboratory, 213 Carriage Lane, Delran, New Jersey 08075, USA
| | - Zia Bukhari
- American Water Research Laboratory, 213 Carriage Lane, Delran, New Jersey 08075, USA
| | - Mark LeChevallier
- American Water Research Laboratory, 213 Carriage Lane, Delran, New Jersey 08075, USA
| | - Charles N Haas
- Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104, USA
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20
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Donohue MJ. Increasing nontuberculous mycobacteria reporting rates and species diversity identified in clinical laboratory reports. BMC Infect Dis 2018; 18:163. [PMID: 29631541 PMCID: PMC5891905 DOI: 10.1186/s12879-018-3043-7] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Accepted: 03/12/2018] [Indexed: 01/15/2023] Open
Abstract
Background Nontuberculous Mycobacteria (NTM) are environmental microorganisms that can affect human health. A 2009–2010 occurrence survey of NTM in potable tap water samples indicated an increased recovery rate for many clinically significant species such as M. avium (30%) and M. abscessus (12%). To determine if these trends by species were mirrored in human infections, isolation rates of NTM species identified in clinical laboratory reports from four states were evaluated. Method Clinical laboratory reports from the Mississippi, Missouri, Ohio, and Wisconsin Health Departments were used to investigate the species of NTM isolated from human specimens in 2014. The NTM positive specimen reports were tabulated for each species and complex/group. The number of reports by month were used to investigate seasonal trends. The 2014 isolation rates were compared to historic values to examine longitudinal trends. Results The positive rate of NTM specimens increased from 8.2 per 100,000 persons in 1994 to 16 per 100,000 persons in 2014 (or 13.3 per 100,000 after excluding Mycobacterium gordonae). Changes in NTM diversity were observed in complex/groups known to be clinically significant. Between 1994 and 2014 the rate implicating M. abscesses-chelonae group and M. avium complex increased by 322 and 149%, respectively. Conclusions Based on public health data supplied by the four State’s Health Departments and the 2014 U.S. population, 50,976 positive NTM specimen reports per year were projected for the nation; serving as an indicator for the national potential disease burden that year. Electronic supplementary material The online version of this article (10.1186/s12879-018-3043-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Maura J Donohue
- United States Environmental Protection Agency, 26 W. Martin Luther King Dr. Mail Stop 587, Cincinnati, Ohio, 45268, USA.
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21
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Experimental human-like model to assess the part of viable Legionella reaching the thoracic region after nebulization. PLoS One 2017; 12:e0186042. [PMID: 28982141 PMCID: PMC5628919 DOI: 10.1371/journal.pone.0186042] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Accepted: 09/25/2017] [Indexed: 11/24/2022] Open
Abstract
The incidence of Legionnaires’ disease (LD) in European countries and the USA has been constantly increasing since 1998. Infection of humans occurs through aerosol inhalation. To bridge the existing gap between the concentration of Legionella in a water network and the deposition of bacteria within the thoracic region (assessment of the number of viable Legionella), we validated a model mimicking realistic exposure through the use of (i) recent technology for aerosol generation and (ii) a 3D replicate of the human upper respiratory tract. The model’s sensitivity was determined by monitoring the deposition of (i) aerosolized water and Tc99m radio-aerosol as controls, and (ii) bioaerosols generated from both Escherichia coli and Legionella pneumophila sg 1 suspensions. The numbers of viable Legionella prior to and after nebulization were provided by culture, flow cytometry and qPCR. This study was designed to obtain more realistic data on aerosol inhalation (vs. animal experimentation) and deposition at the thoracic region in the context of LD. Upon nebulization, 40% and 48% of the initial Legionella inoculum was made of cultivable and non-cultivable cells, respectively; 0.7% of both populations reached the filter holder mimicking the thoracic region in this setup. These results are in agreement with experimental data based on quantitative microbial risk assessment methods and bring new methods that may be useful for preventing LD.
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Prussin AJ, Schwake DO, Marr LC. Ten Questions Concerning the Aerosolization and Transmission of Legionella in the Built Environment. BUILDING AND ENVIRONMENT 2017; 123:684-695. [PMID: 29104349 PMCID: PMC5665586 DOI: 10.1016/j.buildenv.2017.06.024] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Legionella is a genus of pathogenic Gram-negative bacteria responsible for a serious disease known as legionellosis, which is transmitted via inhalation of this pathogen in aerosol form. There are two forms of legionellosis: Legionnaires' disease, which causes pneumonia-like symptoms, and Pontiac fever, which causes influenza-like symptoms. Legionella can be aerosolized from various water sources in the built environment including showers, faucets, hot tubs/swimming pools, cooling towers, and fountains. Incidence of the disease is higher in the summertime, possibly because of increased use of cooling towers for air conditioning systems and differences in water chemistry when outdoor temperatures are higher. Although there have been decades of research related to Legionella transmission, many knowledge gaps remain. While conventional wisdom suggests that showering is an important source of exposure in buildings, existing measurements do not provide strong support for this idea. There has been limited research on the potential for Legionella transmission through heating, ventilation, and air conditioning (HVAC) systems. Epidemiological data suggest a large proportion of legionellosis cases go unreported, as most people who are infected do not seek medical attention. Additionally, controlled laboratory studies examining water-to-air transfer and source tracking are still needed. Herein, we discuss ten questions that spotlight current knowledge about Legionella transmission in the built environment, engineering controls that might prevent future disease outbreaks, and future research that is needed to advance understanding of transmission and control of legionellosis.
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Affiliation(s)
- Aaron J. Prussin
- Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA, 24061, USA
- Corresponding Author:
| | - David Otto Schwake
- Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Linsey C. Marr
- Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA, 24061, USA
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23
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Hamilton KA, Ahmed W, Toze S, Haas CN. Human health risks for Legionella and Mycobacterium avium complex (MAC) from potable and non-potable uses of roof-harvested rainwater. WATER RESEARCH 2017; 119:288-303. [PMID: 28500949 DOI: 10.1016/j.watres.2017.04.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2016] [Revised: 03/30/2017] [Accepted: 04/02/2017] [Indexed: 05/25/2023]
Abstract
A quantitative microbial risk assessment (QMRA) of opportunistic pathogens Legionella pneumophila (LP) and Mycobacterium avium complex (MAC) was undertaken for various uses of roof-harvested rainwater (RHRW) reported in Queensland, Australia to identify appropriate usages and guide risk management practices. Risks from inhalation of aerosols due to showering, swimming in pools topped up with RHRW, use of a garden hose, car washing, and toilet flushing with RHRW were considered for LP while both ingestion (drinking, produce consumption, and accidental ingestion from various activities) and inhalation risks were considered for MAC. The drinking water route of exposure presented the greatest risks due to cervical lymphadenitis and disseminated infection health endpoints for children and immune-compromised populations, respectively. It is therefore not recommended that these populations consume untreated rainwater. LP risks were up to 6 orders of magnitude higher than MAC risks for the inhalation route of exposure for all scenarios. Both inhalation and ingestion QMRA simulations support that while drinking, showering, and garden hosing with RHRW may present the highest risks, car washing and clothes washing could constitute appropriate uses of RHRW for all populations, and toilet flushing and consumption of lettuce irrigation with RHRW would be appropriate for non- immune-compromised populations.
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Affiliation(s)
- Kerry A Hamilton
- CSIRO Land and Water, Ecosciences Precinct, 41 Boggo Road, Qld 4102, Australia; Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104, USA.
| | - Warish Ahmed
- CSIRO Land and Water, Ecosciences Precinct, 41 Boggo Road, Qld 4102, Australia
| | - Simon Toze
- CSIRO Land and Water, Ecosciences Precinct, 41 Boggo Road, Qld 4102, Australia
| | - Charles N Haas
- Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104, USA
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Whiley H, Bentham R, Brown MH. Legionella Persistence in Manufactured Water Systems: Pasteurization Potentially Selecting for Thermal Tolerance. Front Microbiol 2017; 8:1330. [PMID: 28769899 PMCID: PMC5515819 DOI: 10.3389/fmicb.2017.01330] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Accepted: 06/30/2017] [Indexed: 01/13/2023] Open
Abstract
Legionella is an opportunistic waterborne pathogen of increasing public health significance. Pasteurization, otherwise known as super-heat and flush (increasing water temperature to above 70°C and flushing all outlets), has been identified as an important mechanism for the disinfection of Legionella in manufactured water systems. However, several studies have reported that this procedure was ineffective at remediating water distribution systems as Legionella was able to maintain long term persistent contamination. Up to 25% of L. pneumophila cells survived heat treatment of 70°C, but all of these were in a viable but non-culturable state. This demonstrates the limitations of the culture method of Legionella detection currently used to evaluate disinfection protocols. In addition, it has been demonstrated that pasteurization and nutrient starvation can select for thermal tolerant strains, where L. pneumophila was consistently identified as having greater thermal tolerance compared to other Legionella species. This review demonstrates that further research is needed to investigate the effectiveness of pasteurization as a disinfection method. In particular, it focuses on the potential for pasteurization to select for thermal tolerant L. pneumophila strains which, as the primary causative agent of Legionnaires disease, have greater public health significance compared to other Legionella species.
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Affiliation(s)
- Harriet Whiley
- College of Science and Engineering, Flinders University, Bedford ParkSA, Australia
| | - Richard Bentham
- College of Science and Engineering, Flinders University, Bedford ParkSA, Australia
| | - Melissa H Brown
- College of Science and Engineering, Flinders University, Bedford ParkSA, Australia
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25
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Collins S, Stevenson D, Bennett A, Walker J. Occurrence of Legionella in UK household showers. Int J Hyg Environ Health 2017; 220:401-406. [DOI: 10.1016/j.ijheh.2016.12.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Accepted: 12/01/2016] [Indexed: 10/20/2022]
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Hamilton KA, Weir MH, Haas CN. Dose response models and a quantitative microbial risk assessment framework for the Mycobacterium avium complex that account for recent developments in molecular biology, taxonomy, and epidemiology. WATER RESEARCH 2017; 109:310-326. [PMID: 27915187 DOI: 10.1016/j.watres.2016.11.053] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Revised: 11/20/2016] [Accepted: 11/22/2016] [Indexed: 06/06/2023]
Abstract
Mycobacterium avium complex (MAC) is a group of environmentally-transmitted pathogens of great public health importance. This group is known to be harbored, amplified, and selected for more human-virulent characteristics by amoeba species in aquatic biofilms. However, a quantitative microbial risk assessment (QMRA) has not been performed due to the lack of dose response models resulting from significant heterogeneity within even a single species or subspecies of MAC, as well as the range of human susceptibilities to mycobacterial disease. The primary human-relevant species and subspecies responsible for the majority of the human disease burden and present in drinking water, biofilms, and soil are M. avium subsp. hominissuis, M. intracellulare, and M. chimaera. A critical review of the published literature identified important health endpoints, exposure routes, and susceptible populations for MAC risk assessment. In addition, data sets for quantitative dose-response functions were extracted from published in vivo animal dosing experiments. As a result, seven new exponential dose response models for human-relevant species of MAC with endpoints of lung lesions, death, disseminated infection, liver infection, and lymph node lesions are proposed. Although current physical and biochemical tests used in clinical settings do not differentiate between M. avium and M. intracellulare, differentiating between environmental species and subspecies of the MAC can aid in the assessment of health risks and control of MAC sources. A framework is proposed for incorporating the proposed dose response models into susceptible population- and exposure route-specific QMRA models.
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Affiliation(s)
- Kerry A Hamilton
- Department of Civil, Architectural, and Environmental Engineering, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104, USA.
| | - Mark H Weir
- Division of Environmental Health Sciences and Department of Civil Environmental and Geodetic Engineering, The Ohio State University, USA
| | - Charles N Haas
- Department of Civil, Architectural, and Environmental Engineering, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104, USA
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Assessing Inhalation Exposures Associated with Contamination Events in Water Distribution Systems. PLoS One 2016; 11:e0168051. [PMID: 27930709 PMCID: PMC5145240 DOI: 10.1371/journal.pone.0168051] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Accepted: 11/24/2016] [Indexed: 01/15/2023] Open
Abstract
When a water distribution system (WDS) is contaminated, short-term inhalation exposures to airborne contaminants could occur as the result of domestic water use. The most important domestic sources of such exposures are likely to be showering and the use of aerosol-producing humidifiers, i.e., ultrasonic and impeller (cool-mist) units. A framework is presented for assessing the potential effects of short-term, system-wide inhalation exposures that could result from such activities during a contamination event. This framework utilizes available statistical models for showering frequency and duration, available exposure models for showering and humidifier use, and experimental results on both aerosol generation and the volatilization of chemicals during showering. New models for the times when showering occurs are developed using time-use data for the United States. Given a lack of similar models for how humidifiers are used, or the information needed to develop them, an analysis of the sensitivity of results to assumptions concerning humidifier use is presented. The framework is applied using network models for three actual WDSs. Simple models are developed for estimating upper bounds on the potential effects of system-wide inhalation exposures associated with showering and humidifier use. From a system-wide, population perspective, showering could result in significant inhalation doses of volatile chemical contaminants, and humidifier use could result in significant inhalation doses of microbial contaminants during a contamination event. From a system-wide perspective, showering is unlikely to be associated with significant doses of microbial contaminants. Given the potential importance of humidifiers as a source of airborne contaminants during a contamination event, an improved understanding of the nature of humidifier use is warranted.
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Kruse EB, Wehner A, Wisplinghoff H. Prevalence and distribution of Legionella spp in potable water systems in Germany, risk factors associated with contamination, and effectiveness of thermal disinfection. Am J Infect Control 2016; 44:470-4. [PMID: 26775932 DOI: 10.1016/j.ajic.2015.10.025] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Revised: 10/20/2015] [Accepted: 10/28/2015] [Indexed: 11/28/2022]
Abstract
BACKGROUND Worldwide, Legionella spp are a common cause of community-acquired pneumonia. Potable water systems are a main reservoir; however, exposure in the community is unknown. METHODS Water samples from 718 buildings in Germany were collected. Possible risk factors were prospectively recorded. All samples were tested for Legionella spp using cultural microbiologic methods. Samples were assigned to 1 of 5 levels of contamination. Statistical analysis was performed to determine the influence of risk factors for contamination and, in a subgroup of buildings, for unsuccessful thermal disinfection. RESULTS In total, 4,482 water samples from 718 different water supply systems were analyzed. In 233 buildings (32.7%), Legionella spp were identified, 148 (63.5%) of which had a medium or higher level of contamination. The most common species was Legionella pneumophila (94%). Contamination was strongly associated with temperature in the circulation, but not with the size of the building, time of the year, or transport time to the laboratory. Thermal disinfection was successful in fewer than half of the buildings. CONCLUSIONS There is relevant exposure to Legionella spp in the community. Water systems are not always up to current technical standards. Although microbiological risk assessment remains a challenge, there is a case for monitoring for Legionella spp outside of hospitals.
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Affiliation(s)
| | | | - Hilmar Wisplinghoff
- Wisplinghoff Laboratories, Cologne, Germany; Institute for Medical Microbiology, Immunology, and Hygiene, University of Cologne, Cologne, Germany
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Angelon-Gaetz KA, Richardson DB, Lipton DM, Marshall SW, Lamb B, LoFrese T. The effects of building-related factors on classroom relative humidity among North Carolina schools participating in the 'Free to Breathe, Free to Teach' study. INDOOR AIR 2015; 25:620-30. [PMID: 25515546 PMCID: PMC4470893 DOI: 10.1111/ina.12176] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2014] [Accepted: 12/11/2014] [Indexed: 05/22/2023]
Abstract
UNLABELLED Both high and low indoor relative humidity (RH) directly impact Indoor Air Quality (IAQ), an important school health concern. Prior school studies reported a high prevalence of mold, roaches, and water damage; however, few examined associations between modifiable classroom factors and RH, a quantitative indicator of dampness. We recorded RH longitudinally in 134 North Carolina classrooms (n = 9066 classroom-days) to quantify the relationships between modifiable classroom factors and average daily RH below, within, or above levels recommended to improve school IAQ (30-50% or 30-60% RH). The odds of having high RH (>60%) were 5.8 [95% Confidence Interval (CI): 2.9, 11.3] times higher in classrooms with annual compared to quarterly heating, ventilating, and air-conditioning (HVAC) system maintenance and 2.5 (95% CI: 1.5, 4.2) times higher in classrooms with HVAC economizers compared to those without economizers. Classrooms with direct-expansion split systems compared to chilled water systems had 2.7 (95% CI: 1.7, 4.4) times higher odds of low RH (<30%). When unoccupied, classrooms with thermostat setbacks had 3.7 (95% CI: 1.7, 8.3) times the odds of high RH (>60%) of those without setbacks. This research suggests actionable decision points for school design and maintenance to prevent high or low classroom RH. PRACTICAL IMPLICATIONS This study combines longitudinal measurements of classroom relative humidity with school inspection data from several schools to describe the problem of relative humidity control in schools. Our findings on how maintenance and mechanical factors affect classroom humidity provide suggestions on building operations policies and heating, ventilating, and air-conditioning (HVAC) design considerations that may improve classroom relative humidity control.
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Affiliation(s)
- K A Angelon-Gaetz
- Epidemiology Department, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - D B Richardson
- Epidemiology Department, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - D M Lipton
- North Carolina Division of Public Health, Department of Health and Human Services, Raleigh, NC, USA
| | - S W Marshall
- Epidemiology Department, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - B Lamb
- Maintenance Operations Department, New Hanover County Schools, Wilmington, NC, USA
| | - T LoFrese
- Support Services, Chapel Hill-Carrboro City Schools, Chapel Hill, NC, USA
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