Impact of Chemical Properties of Human Respiratory Droplets and Aerosol Particles on Airborne Viruses' Viability and Indoor Transmission.

The airborne transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been identified as a potential pandemic challenge, especially in poorly ventilated indoor environments, such as certain hospitals, schools, public buildings, and transports. The impacts of meteorological parameters (temperature and humidity) and physical property (droplet size) on the airborne transmission of coronavirus in indoor settings have been previously investigated. However, the impacts of chemical properties of viral droplets and aerosol particles (i.e., chemical composition and acidity (pH)) on viability and indoor transmission of coronavirus remain largely unknown. Recent studies suggest high organic content (proteins) in viral droplets and aerosol particles supports prolonged survival of the virus by forming a glassy gel-type structure that restricts the virus inactivation process under low relative humidity (RH). In addition, the virus survival was found at neutral pH, and inactivation was observed to be best at low (<5) and high pH (>10) values (enveloped bacteriophage Phi6). Due to limited available information, this article illustrates an urgent need to research the impact of chemical properties of exhaled viral particles on virus viability. This will improve our fundamental understanding of indoor viral airborne transmission mechanisms.

Respiratory Deposition Dose of PM2.5 and PM10 Before, During and After COVID-19 Lockdown Phases in Megacity-Delhi, India

Considerable changes in particulate matter (PM) during COVID-19 lockdown in major cities around the World demand changes in exposure assessment studies of PM. The present study shows variations in respiratory deposition dose (RDD) of both fine (PM2.5) and coarse (PM10) particles before, during and after Covid-19 lockdown phases at three sites (with different pollution signatures) in Delhi—Alipur, Okhla and Pusa Road. Exposure assessment study showed mean PM2.5 RDD (± S.D.) (µg/min) for walk and sit mode during before lockdown (BL) as 2.41(± 1.20) and 0.84(± 0.42) for Alipur, 2.71(± 1.60) and 0.94(± 0.56) for Okhla, and 2.54(± 1.28) and 0.88(± 0.44) for Pusa road, which decreased drastically during Lockdown 1(L1) as 0.85(± 0.35) and 0.30(± 0.12) for Alipur, 0.83(± 0.33) and 0.29(± 0.11) for Okhla, and 0.68(± 0.28) and 0.23(± 0.10) for Pusa road, respectively. Mean PM10 RDD (± S.D.) (µg/min) for walk and sit mode during before lockdown (BL) as 3.90 (± 1.73) and 1.36 (± 0.60) for Alipur, 4.74 (± 2.04) and 1.65 (± 0.71) for Okhla, and 4.25 (± 1.69) and 1.48 (± 0.59) for Pusa Road, respectively which decreased drastically during Lockdown 1(L1) as 2.19 (± 0.95) and 0.76 (± 0.33) for Alipur, 1.73 (± 0.67) and 0.60 (± 0.23) for Okhla and, 1.45 (± 0.50) and 0.50 (± 0.17) for Pusa Road, respectively. Significant decrease in RDD concentrations (Both PM2.5 and PM10) than that of BL phase have been found during Lockdown 1(L1) phase and other successive lockdown and unlock phases—Lockdown 2(L2), Lockdown 3(L3), Lockdown 4(L4) and Unlock1 (UL1) phases. Changes in RDD values during lockdown phases were affected by lesser traffic emission, minimized industrial activities, biomass burning activities, precipitation activities, etc. Seasonal variations of RDD showed Delhites are found exposed to more fine and coarse particles’ RDD (walk and sit modes) before and after lockdown, i.e. during normal days than during lockdown phases showing potential health effects. People in sit condition found less exposed to fine and coarse RDD comparison to those in walk condition both during normal and lockdown days.

Variations and Source Apportionment of PM2.5 and PM10 Before and During COVID-19 Lockdown Phases in Delhi, India

Major cities across the globe including megacity Delhi have experienced considerable lower levels of air pollutants including particulate matter (PM) during COVID-19 lockdown. This study explores pre-lockdown and during lockdown air quality changes in PM2.5, PM10, PM2.5/PM10 ratio along with meteorological effects. Selected sites with different pollution signatures in Delhi including Alipur (residential), Okhla (industrial) and Pusa Road (traffic) have experienced mean (S.D.) PM2.5 as 87.56(± 54.06), 124.45(± 73.49) and 62.14(± 58.64) µg/m3 and PM10 as 163.01(± 77.37), 217.71(± 93.94) and 135.15(± 77.90) µg/m3 before lockdown (BL), while for Lockdown 1 (L1), PM2.5 concentrations decreased drastically as 39.26(± 16.31), 38.01(± 15.16) and 31.03(± 12.79) µg/m3 and for PM10 as 100.76(± 43.71), 79.47(± 30.97) and 66.53(± 22.78) µg/m3, respectively, with gradual increase in both pollutants during successive lockdown phase—Lockdown 2, Lockdown 3, Lockdown 4 and Unlock phase 1. The percentage (%) decrease in PM2.5 (69.46%) and PM10 (63.49%) during lockdown was found well correlated with people mobility (Google and Apple mobility reports), as outdoor activities showed 70–80% decrease in L1 from BL phase. Source apportionment studies suggested both local and regional pollution contribution in Delhi. Comparison of PM2.5 and PM10 concentrations for the year 2020 with that of 2018 and 2019 and study on diurnal variations of PM2.5 and PM10 have been discussed.

Preventing Airborne Transmission of SARS-CoV-2 in Hospitals and Nursing Homes.

The first case of the coronavirus disease 2019 (COVID-19), the novel contagious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was reported in Wuhan, China in December 2019 [...].

Impact of COVID-19 lockdown on aerosol optical and radiative properties over Indo-Gangetic Plain

Aerosol optical and radiative properties, measured with the ground based sun-sky radiometer (under AERONET), were explored at Kanpur in the central and Gandhi College (Ballia) in the Eastern Indo-Gangetic Plain (IGP) in Northern India during January to July 2019 (non-lockdown) and 2020 (lockdown). This year 2020 is marked an overall reduction of 15.79% and 3.39% in aerosol optical depth (AOD) than year 2019 at Kanpur and Gandhi College respectively. Lockdown 1 (23rd March to 14th April 2020) showed a reduction of 52.52% and 42.22% in AOD compared to pre-lockdown condition at Kanpur and Gandhi College respectively. Higher values of angstrom exponent measured at Eastern region (1.13 ± 0.17) than central region (0.97 ± 0.26) indicating the dominance of fine particles at Gandhi College. There was an overall reduction of 1.31% in single scattering albedo (SSA) at Kanpur while 4.34% reduction was observed at Gandhi College in year 2020 than 2019. The resultant atmospheric forcing and heating rate shows 11.86% reduction at Kanpur while 35.27% increase at Gandhi College during the lockdown period in 2020 compared to 2019. However, these values were found to decrease by 23.48% and 15.07% at Kanpur and Gandhi College respectively during the strict lockdown period compared to year 2019.