Indoor Air Quality in Hospitals: PM and Airborne Viruses

Abstract

In this study, we characterize particulate matter concentrations and airborne viruses at a health care facility and explore correlations with indoor parameters such as the air exchange rate, relative humidity and temperature. We also examine the transmission, decay, and suspension of virus shedding by patients. For this purpose, PM2.5, PM10, and airborne viruses (influenza A, influenza B, respiratory syncytial virus (RSV)) were monitored in patient rooms with confirmed infections. The indoor measurements showed that patients were exposed to elevated PM2.5 levels, ranging between 7 and 53 µg/m3 with a mean of 24.5 µg/m3, and to PM10 concentrations that reached 89 µg/m3. Overall, 91% of the monitored patient rooms exceeded the PM2.5 daily exposure level of 10 mg/m3, while 70% of the rooms exceeded the PM10 daily exposure level of 20 mg/m3. Influenza A was detected in 42% of the monitored rooms, with concentrations ranging between 222 and 5,760 copies/m3, with a mean of 820 copies/m3. The results showed that while viral concentrations (RNA copies/m3) tended to decrease significantly with distance away from the patient, traces were still detectable at 1 m and even at 1.5 m. Statistical and numerical analyses clearly showed that the viral removal efficiency was affected by changes in the relative humidity more than changes in room temperature. Moreover, the results from a calibrated Gaussian puff model showed that dispersion was the dominant pathways for viral removal. Based on the results of this study, a set of mitigation measures are proposed within a management framework to reduce exposure of staff, visitors and patients to particulate matter and airborne viruses in hospitals.