Respiratory infection transmission risk and indoor air quality at outpatient departments and emergency treatment units of Sri Lankan teaching hospitals

Abstract

Indoor carbon dioxide (CO2) concentration has been used as a proxy of the degree of ventilation and, by extension, as an indicator of the risk of contracting respiratory infections. No publications exist regarding indoor air quality (IAQ) parameters of Sri Lankan hospitals.We measured the levels of CO2 and seven other IAQ parameters during morning rush hours for three days, in outpatient departments (OPDs) and emergency treatment units (ETUs) of all 21 teaching hospitals of Sri Lanka. We measured the same parameters of outdoor air also. We calculated the mean values of those parameters. We looked for correlations between outdoors and OPD and ETU levels of selected air quality parameters.The average CO2 levels of outdoors, OPDs and ETUs respectively were 514ppm (ppm = parts per million), 749ppm and 795ppm. The average levels of PM2.5 (particulate matter with diameters <2.5μm) outdoors, OPDs and ETUs respectively, were 28.7μg/m3,32μg/m3 and 25.6 μg/m3. The average levels of PM10 (particulate matter with diameters <10μm) outdoors, OPDs and ETUs respectively, were 49.4μg/m3, 55.5μg/m3 and 47.9 μg/m3. The median levels of formaldehyde outdoors, OPDs and ETUs respectively, were 0.03mg/m3, 0.04mg/m3 and 0.08mg/m3. The median levels of total volatile organic compounds (VOC) outdoors, OPDs and ETUs respectively were 0.12mg/m3, 0.19mg/m3 and 0.38mg/m3.CO2 levels of air in OPDs and ETUs generally were below the national ceilings but above the ceilings used by some developed countries. Outdoors, OPDs and ETUs air contain PM10, PM2.5 levels higher than WHO ceilings, although below the national ceilings. VOC and formaldehyde levels are generally below the national ceilings. Air in OPDs and ETUs is hotter and humid than national ceilings. Outdoor PM10, PM2.5 levels influence OPDs and ETUs levels. We propose methods to reduce the risk of nosocomial respiratory infections and to improve IAQ of Sri Lankan OPDs and ETUs.

Fig 1. Schematic representation of how respiratory infections are transmitted from an infected person during a forceful exhalation in indoors.

This illustrates exhalation of infected respiratory droplets of various sizes (red color), how larger ones fall on surfaces resulting fomites, how fomites lead to contraction of infections when touch the face with contaminated hands, how a few droplets can directly get deposited in the respiratory tract and how smaller droplets (aerosols) that hang in the air for a long time infect susceptible people. This depicts how ventilation (outdoor air) dilutes droplet concentration and shrinking of droplet size with evaporation (blue arc) as well. Green droplets are non-infected ones exhaled during normal exhalations. This figure was created by the first author using Microsoft Office2010 software and clipart from https://openclipart.org/.

Fig 2. The locations of teaching hospitals of Sri Lanka participated in this study are marked as blue dots in the map.

The background shows population density in color codes. Due to the proximity of some hospitals to each other, some blue dots overlap at this scale. We adopted Fig 1 of https://doi.org/10.1371/journal.pntd.0004813 published under CC BY4.0. [34] as the base layer of this map.

Fig 3. Average CO2 concentrations of OPDs and ETUs of each hospital.

This figure was created by the first author using Microsoft Office 2010 software. National Hospital Colombo (NHSL), National Hospital Kandy (NHK), Teaching Hospital (TH) Peradeniya (Peradeni), TH Karapitiya (Karapiti), Castle Street Hospital for Women (CSHW), De Soysa Hospital for Women (DMH), TH Mahamodara (Mahamoda), TH Anuradhapura (Anuradha), TH Colombo North Ragama (Ragama), TH Batticaloa (Batti), TH Jaffna (Jaffna), Lady Ridgeway Hospital for Children (LRH), Sirimavo Bandaranaike Specialized Childrens Hospital (SBSCH), TH Colombo South Kalubowila (CSTH), TH Kuliyapitiya (Kuliya), TH Ratnapura (Ratnapura), National Eye Hospital-Colombo (Eye), TH (Chest hospital)-Welisara (Welisara), Rehabilitation Hospital-Ragama (RHR), Dental Institute-Colombo (DI-C), National Institute of Mental Health-Angoda (NIMH), National Cancer Institute Maharagama (Apeksha).