What is the relationship between indoor air quality parameters and airborne microorganisms in hospital environments? A systematic review and meta-analysis.

Waseem Hiwar,Catherine J Noakes,Marco‐Felipe King,Louise A Fletcher,Farag Shuweihdi,Stephanie J Dancer

doi:10.1111/ina.12846

Waseem Hiwar, Catherine J Noakes + Show 4 more

Open Access

https://doi.org/10.1111/ina.12846

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Abstract

Airborne microorganisms in hospitals have been associated with several hospital-acquired infections (HAIs), and various measures of indoor air quality (IAQ) parameters such as temperature, relative humidity, carbon dioxide (CO2 ), particle mass concentration, and particle size have been linked to pathogen survival or mitigation of pathogen spread. To investigate whether there are quantitative relationships between the concentration of airborne microorganisms and the IAQ in the hospital environment. Web of Science, Scopus and PubMed databases were searched for studies reporting airborne microbial levels and any IAQ parameter(s) in hospital environments, from database inception to October 2020. Pooled effect estimates were determined via random-effects models. Seventeen of 654 studies were eligible for the meta-analysis. The concentration of airborne microbial measured as aerobic colony count (ACC) was significantly correlated with temperature (r=0.25 [95% CI=0.06-0.42], p=0.01), CO2 concentration (r=0.53 [95% CI=0.40-0.64], p˂0.001), particle mass concentration (≤5µg/m3 ; r=0.40 [95% CI=0.04-0.66], p=0.03), and particle size (≤5 and ˃5µm), (r=0.51 [95% CI=0.12-0.77], p=0.01 and r=0.55 [95% CI=0.20-0.78], p=0.003), respectively, while not being significantly correlated with relative humidity or particulate matter of size >5µm. Conversely, airborne total fungi (TF) were not significantly correlated with temperature, relative humidity, or CO2 level. However, there was a significant weak correlation between ACC and TF (r=0.31 [95% CI=0.07-0.52], p=0.013). Although significant correlations exist between ACC and IAQ parameters, the relationship is not definitive; the IAQ parameters may affect the microorganisms but are not responsible for the presence of airborne microorganisms. Environmental parameters could be related to the generating source, survival, dispersion, and deposition rate of microorganisms. Future studies should record IAQ parameters and factors such as healthcare worker presence and the activities carried out such as cleaning, sanitizing, and disinfection protocols. Foot traffic would influence both the generation of microorganisms and their deposition rate onto surfaces in the hospital environment. These data would inform models to improve the understanding of the likely concentration of airborne microorganisms and provide an alternative approach for real-time monitoring of the healthcare environment.

Highlights

Hospital-acquired infections (HAIs) are a globally significant problem and their treatment can be costly.1-3 In the UK, HAIs are estimated to cost up to a billion pounds per year as of 2017 and the hospital environment is thought to play a role in approximately 20% of all HAIs by influencing the survival and spread of pathogens in the environment.[4,5] The hospital environment is subject to workplace design and layout, operation and maintenance, and hosts multiple interactions between environment and people
These presented quantitative airborne microbial concentration measured as aerobic colony count (ACC) or airborne total fungi (TF) concentration (TF) with at least one quantitative factor of the indoor air quality (IAQ) parameters at the same time point in a hospital setting and the correlation coefficient values and sample size for the relationships are given for each study (Table 1).1,2,7,8,10-12,28-32,44-48
The importance of ensuring good IAQ to minimize airborne microorganism transmission is recognized,[51] we found that there are a very small number of studies that carry out sufficient quantitative measurement to reliably assess relationships between airborne microorganisms and environmental parameters

Summary

Introduction

Hospital-acquired infections (HAIs) are a globally significant problem and their treatment can be costly.1-3 In the UK, HAIs are estimated to cost up to a billion pounds per year as of 2017 and the hospital environment is thought to play a role in approximately 20% of all HAIs by influencing the survival and spread of pathogens in the environment.[4,5] The hospital environment is subject to workplace design and layout, operation and maintenance, and hosts multiple interactions between environment and people. Studies investigating microbial contamination of the environment have suggested that a wide range of factors may influence the presence of microorganisms including IAQ parameters such as temperature, relative humidity, and ventilation; staff activities, patient status, and visitor numbers; and surface types, including how and when they are cleaned.1,3,6-12 A very small number of studies correlated virus concentrations to these factors, the focus of this study on the investigation of relationships between bacteria and fungi in the air and IAQ parameters. Microbial sampling of the air can be used to evaluate the likely concentration of airborne microorganisms present in the hospital environment. Airborne microbial load can be quantified by using either active or passive sampling methods.[8,16]

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