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      Temporary reduction in fine particulate matter due to ‘anthropogenic emissions switch-off’ during COVID-19 lockdown in Indian cities

      research-article
      * , , , , , , , , ,
      Sustainable Cities and Society
      The Author(s). Published by Elsevier Ltd.
      AOD, aerosol optical depth, AQI, air quality index, CO, carbon monoxide, CO2, carbon dioxide, COVID-19, Coronavirus disease 2019, EPA, Environmental Protection Agency, ER, excess risk, ESA, European Space Agency, GEV, generalized extreme value, GoI, Government of India, HB, health burden, MODIS, moderate resolution imaging spectroradiometer, MSL, mean sea level, NASA, National Aeronautics and Space Administration, NH3, ammonia, NO2, nitrogen dioxide, O3, ozone, PDF, probability density function, PM, particulate matter, PM2.5, PM with aerodynamic diameter of < 2.5 µm, PM10, PM with aerodynamic diameter of < 10 µm, RH, relative humidity, RR, relative risk, SARS-CoV-2, Severe Acute Respiratory Syndrome Coronavirus 2, SO2, sulphur dioxide, SSEC, Space Science and Engineering Centre, TROPOMI, TROPOspheric monitoring instrument, UK, United Kingdom, USA, United States of America, USD, United States Dollar, VSL, value of statistical life, WHO, World Health Organization, Coronavirus pandemic, SARS-CoV-2 Virus, Air pollution, Health and economic impacts, PM2.5 concentration, Emission switch-off

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          Graphical abstract

          Highlights

          • COVID-19 lockdown reduced PM 2.5 concentrations in five Indian cities by up to 54 %.

          • PM 2.5 reduction in Delhi was similar to that of other Asian and European cities.

          • Modelling revealed fewer extreme PM 2.5 values during the lockdown in all cities.

          • Spatial distribution of AOD showed a general decrease in aerosol loading.

          • PM 2.5 reductions prevented ∼630 premature deaths, valued at 0.69 billion USD.

          Abstract

          The COVID-19 pandemic elicited a global response to limit associated mortality, with social distancing and lockdowns being imposed. In India, human activities were restricted from late March 2020. This ‘anthropogenic emissions switch-off’ presented an opportunity to investigate impacts of COVID-19 mitigation measures on ambient air quality in five Indian cities (Chennai, Delhi, Hyderabad, Kolkata, and Mumbai), using in-situ measurements from 2015 to 2020. For each year, we isolated, analysed and compared fine particulate matter (PM 2.5) concentration data from 25 March to 11 May, to elucidate the effects of the lockdown. Like other global cities, we observed substantial reductions in PM 2.5 concentrations, from 19 to 43% (Chennai), 41–53 % (Delhi), 26–54 % (Hyderabad), 24–36 % (Kolkata), and 10–39 % (Mumbai). Generally, cities with larger traffic volumes showed greater reductions. Aerosol loading decreased by 29 % (Chennai), 11 % (Delhi), 4% (Kolkata), and 1% (Mumbai) against 2019 data. Health and related economic impact assessments indicated 630 prevented premature deaths during lockdown across all five cities, valued at 0.69 billion USD. Improvements in air quality may be considered a temporary lockdown benefit as revitalising the economy could reverse this trend. Regulatory bodies must closely monitor air quality levels, which currently offer a baseline for future mitigation plans.

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          Most cited references88

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          Aerodynamic analysis of SARS-CoV-2 in two Wuhan hospitals

          The ongoing outbreak of coronavirus disease 2019 (COVID-19) has spread rapidly on a global scale. Although it is clear that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is transmitted through human respiratory droplets and direct contact, the potential for aerosol transmission is poorly understood1-3. Here we investigated the aerodynamic nature of SARS-CoV-2 by measuring viral RNA in aerosols in different areas of two Wuhan hospitals during the outbreak of COVID-19 in February and March 2020. The concentration of SARS-CoV-2 RNA in aerosols that was detected in isolation wards and ventilated patient rooms was very low, but it was higher in the toilet areas used by the patients. Levels of airborne SARS-CoV-2 RNA in the most public areas was undetectable, except in two areas that were prone to crowding; this increase was possibly due to individuals infected with SARS-CoV-2 in the crowd. We found that some medical staff areas initially had high concentrations of viral RNA with aerosol size distributions that showed peaks in the submicrometre and/or supermicrometre regions; however, these levels were reduced to undetectable levels after implementation of rigorous sanitization procedures. Although we have not established the infectivity of the virus detected in these hospital areas, we propose that SARS-CoV-2 may have the potential to be transmitted through aerosols. Our results indicate that room ventilation, open space, sanitization of protective apparel, and proper use and disinfection of toilet areas can effectively limit the concentration of SARS-CoV-2 RNA in aerosols. Future work should explore the infectivity of aerosolized virus.
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            Airborne transmission of SARS-CoV-2: the world should face the reality

            Hand washing and maintaining social distance are the main measures recommended by the World Health Organization (WHO) to avoid contracting COVID-19. Unfortunately, these measured do not prevent infection by inhalation of small droplets exhaled by an infected person that can travel distance of meters or tens of meters in the air and carry their viral content. Science explains the mechanisms of such transport and there is evidence that this is a significant route of infection in indoor environments. Despite this, no countries or authorities consider airborne spread of COVID-19 in their regulations to prevent infections transmission indoors. It is therefore extremely important, that the national authorities acknowledge the reality that the virus spreads through air, and recommend that adequate control measures be implemented to prevent further spread of the SARS-CoV-2 virus, in particularly removal of the virus-laden droplets from indoor air by ventilation.
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              Estimating clinical severity of COVID-19 from the transmission dynamics in Wuhan, China

              As of 29 February 2020 there were 79,394 confirmed cases and 2,838 deaths from COVID-19 in mainland China. Of these, 48,557 cases and 2,169 deaths occurred in the epicenter, Wuhan. A key public health priority during the emergence of a novel pathogen is estimating clinical severity, which requires properly adjusting for the case ascertainment rate and the delay between symptoms onset and death. Using public and published information, we estimate that the overall symptomatic case fatality risk (the probability of dying after developing symptoms) of COVID-19 in Wuhan was 1.4% (0.9–2.1%), which is substantially lower than both the corresponding crude or naïve confirmed case fatality risk (2,169/48,557 = 4.5%) and the approximator 1 of deaths/deaths + recoveries (2,169/2,169 + 17,572 = 11%) as of 29 February 2020. Compared to those aged 30–59 years, those aged below 30 and above 59 years were 0.6 (0.3–1.1) and 5.1 (4.2–6.1) times more likely to die after developing symptoms. The risk of symptomatic infection increased with age (for example, at ~4% per year among adults aged 30–60 years).
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                Author and article information

                Contributors
                Journal
                Sustain Cities Soc
                Sustain Cities Soc
                Sustainable Cities and Society
                The Author(s). Published by Elsevier Ltd.
                2210-6707
                2210-6715
                13 July 2020
                13 July 2020
                : 102382
                Affiliations
                [0005]Global Centre for Clean Air Research (GCARE), Department of Civil and Environmental Engineering, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford GU2 7XH, United Kingdom
                Author notes
                Article
                S2210-6707(20)30603-X 102382
                10.1016/j.scs.2020.102382
                7357527
                32834936
                74a733bf-af4b-430f-b697-d7d52704c1d5
                © 2020 The Author(s)

                Since January 2020 Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on the novel coronavirus COVID-19. The COVID-19 resource centre is hosted on Elsevier Connect, the company's public news and information website. Elsevier hereby grants permission to make all its COVID-19-related research that is available on the COVID-19 resource centre - including this research content - immediately available in PubMed Central and other publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for free by Elsevier for as long as the COVID-19 resource centre remains active.

                History
                : 31 May 2020
                : 21 June 2020
                : 24 June 2020
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                Article

                aod, aerosol optical depth,aqi, air quality index,co, carbon monoxide,co2, carbon dioxide,covid-19, coronavirus disease 2019,epa, environmental protection agency,er, excess risk,esa, european space agency,gev, generalized extreme value,goi, government of india,hb, health burden,modis, moderate resolution imaging spectroradiometer,msl, mean sea level,nasa, national aeronautics and space administration,nh3, ammonia,no2, nitrogen dioxide,o3, ozone,pdf, probability density function,pm, particulate matter,pm2.5, pm with aerodynamic diameter of < 2.5 µm,pm10, pm with aerodynamic diameter of < 10 µm,rh, relative humidity,rr, relative risk,sars-cov-2, severe acute respiratory syndrome coronavirus 2,so2, sulphur dioxide,ssec, space science and engineering centre,tropomi, tropospheric monitoring instrument,uk, united kingdom,usa, united states of america,usd, united states dollar,vsl, value of statistical life,who, world health organization,coronavirus pandemic,sars-cov-2 virus,air pollution,health and economic impacts,pm2.5 concentration,emission switch-off

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