Mumbai, New Delhi | NO2 | ~ 10 μg/m3 (Mumbai) |
Sentinel-SP satellite images ESA and NASA | January 1–March 24 2020 (before lockdown) |
Reduction in NO2 due to decrease in electric consumption | |
366 urban areas in China's mainland | AQI, PM2.5, PM10, NO2, SO2, CO, O3 | Average AQI for all stations reduced from 89.6 to 71.6 | China's National Environmental Monitoring Centre. | January 1–January 23 2020 (before control period) |
Reduction in pollutants due to lockdown of transport and secondary industries. Increase of ozone due to less scavenging of HO2. |
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Pengfei et al. (2020) | 10 major cities in China | PM2.5 and its components SO4, NO3, NH4, and SOA |
10% – 20% reduction in PM2.5; 30% – 50% reduction in its components. Increase in PM2.5 with value of 69.38 μg/m3 in Tiajin and 14.24% increase in Xian |
China's National Environmental Monitoring Centre |
January 1–February 12, 2020 (High and low pollution days) |
Reduction due to transportation and slight reduction in industrial activity Increase in PM2.5 due to unfavourable meteorological conditions |
Wuhan | PM2.5 and other air pollutants, PM2.5 chemical species, Meteorological parameters | PM2.5 reduced by 27.0 μg/m3 (Compared to previous year, same time period) | In situ observations |
January 23–February 22 2020 (During lockdown and comparison with previous year, same period) Residential/commercial with no industrial emissions at surroundings |
Reduction in chemical species and sources. Primary emission decreased and secondary emission enhanced |
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Beijing Wuhan Guangzhou | NO2, SO2, O3, HCHO, PM2.5 |
NO2 decreased by 28%, 57% and 46% Little influence on SO2 irrespective of cities |
Lockdown period (same period as previous year) | NO2 and HCHO by remote sensing satellite - Other indices – In-situ measurements | Different responses for different air pollutants in different places. | |
33 locations in China | AQI | -- | January 29–February 15 2020 (Lockdown period) |
China National Environmental Monitoring Centre Meteorological data provider and China Meteorological Data Service Centre |
AQI effect on confirmed cases in temperature range 10–20 °C is stronger and spread of COVID enhanced under low relative humidity. | |
Shanghai, China | NR-PM2.5, SO2, CO, Sulphate and OOA |
Nitrate decreased by 60%, SO2 by 15%, CO by 22%. Sulphate and OOA barely decreased |
January 8–January 23 (before lockdown) January 24–February 8 (lockdown) |
A Time of Flight- Aerosol Chemical Speciation Monitor (Tof- ACSM) - NR PM2.5 PM2.5, SO2, NOx, CO and O3-Air quality station |
Nitrate was dominant NR-PM2.5 component A slight reduction in sulphate and OOA concentrations inhibited PM2.5 reduction. |
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Globally, 597 major cities from 76 countries | PM2.5, PM10, NO2, SO2, CO, O3 | NO2 falls more precipitously, followed by PM10, SO2, PM2.5, and CO, but O3 increases relative to pre lockdown period. | January 1–July 5 2020 (lockdown period) | Air quality open data platform | Improvement in air quality due to lockdown | |
44 cities in northern China | AQI, PM2.5, PM10, NO2, SO2, CO | The concentrations of SO2, PM2.5, PM10, NO2 and CO decreased by 6.76%, 5.93%, 13.66%, 24.67% and 4.58% respectively. | January 1–March 21 2020 |
Real time data system of the MEE Human mobility measured by real time IMI index extracted from Baidu Maps |
Travel restriction measures significantly reduced air pollution. | |
120 cities in China | PM2.5, PM10, NO2, SO2, CO, O3, Covid-19 confirmed cases | Increase in air pollutants except SO2 was associated with increase in daily counts of COVID-19 confirmed cases. | January 23–February 29 2020 |
Local health commissions on official websites Air pollution data from online platform Meteorological data from National Meteorological Information centre |
Positive association of PM2.5, PM10, CO, NO2 and O3 with COVID-19 confirmed cases SO2 was negatively associated with confirmed cases |
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10 most affected provinces in China | Temperature COVID-19 confirmed cases | Positive relationship with temperature and COVID-19 | January 22–March 31 2020 |
Weather underground company Chinese National Health Commission |
Positive, negative, and mixed trends | |
31 provincial cities in China | PM2.5, PM10, NO2, SO2, CO, O3 | All air pollutants except O3 reduced | January 1–May 2, 2020 | Website of National Environmental Monitoring Centre of China | Increase in O3 is of primary concern | |
New York City 15 central monitoring stations | PM2.5 and NO2 | 36% and 51% reduction in PM2.5 and NO2 after shutdown | January–May 2015 to 2020 | DEC's air monitoring website (New York state Department of Environmental Conservation, 2020) | Short-term decline in pollution levels in 2020 | |
London borough | PM2.5 and NO2 | Correlation of PM2.5 and NO2 with Covid cases | As of March 31 2020 | Public Health England 2020 |
Correlation between increment in PM2.5 and NO2 and increase in risk of COVID-19 transmission | |
Cities of Barcelona and Madrid, Spain | NO2 | Reduction compared to previous years | March 2018–2020 | Air Quality Monitoring Networks |
Under lockdown, reduction of NO2 in Barcelona and Madrid were 50% and 62%, respectively. | |
Metropolitan city of Milan, Italy | PM2.5, PM10, NOx, SO2, NO2, CO, O3, BC, benzene |
PM2.5, PM10, NOx, BC, Benzene and CO reduced and O3 increased. SO2 dropped only in Milan not in adjacent areas. |
9 to 22 March 2020 (partial lockdown) 23 March to 5 April 2020 (total lockdown) |
Air quality data from local environmental protection agency Data for estimation of sources of PM2.5, PM10, CO, NO2, SO2, NOx from regional inventory of emissions from Lombardy Meteorological data by local environmental protection agency |
Increase in O3 due to presence of benzene even though VOCs emissions from vehicular traffic and industrial combustion decreased. | |
21 Italian regions | PM2.5 and NO2 | High correlation between PM2.5 and total number of cases, ICU admissions, deaths and hospitalizations | February 2020 |
Air pollution data from Air-Matters app Patient data- Italian civil protection website Population data – Italian Statistical agency |
Exposure to high levels of NO2 exacerbates symptoms. Strong correlation between severity of Covid and level of air pollutants. |
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European countries – Italy, Spain, France and Germany (66 administrative regions) | NO2 | Long-term exposure to this pollutant and Covid-19 fatality | January to February 2020 |
Sentinel -5 precursor space borne satellite NCEP/NCAR reanalysis Information about fatalities from Ministry of Health (Italy) Ministry of Health, Social Services and Equality (Spain) The National Agency of Public Health (France) Robert-Koch-Institute and the State Health Offices (Germany) |
Chronic exposure to NO2 could be an important contributor to high Covid fatality rate. | |
Ontario, Canada 32 stations | PM2.5, NO2, NOX, O3 | NO2 and NOX reduced | January 3–February 6, 2020 (five weeks), compared with previous five years same period. | Ontario Ministry of the Environment, Conservation and Park's air pollution data portal | Ozone reduced and PM2.5 has not varied. | |
Rio de Janeiro, Brazil | NO2, NO, O3, NHMC | Reduction in NOx | March 1 to April 16 2020 | Automatic monitoring stations of the Municipal Department of the Environment | Increase in O3 due to increase in NMHC/NOX ratios. | |
Southeast Asian countries and Malaysia | AOD, PM2.5, PM10, SO2, NO2, and CO | Notable reduction in pollutants in urban areas | March 18–30 April for three years 2018, 2019, 2020 |
Himawari -8 satellite Aura-OMI Ground based pollution measurements |
A large decrease in NO2 levels occurred in industrial sites and urban | |
Eastern Province, Saudi Arabia | PM10, SO2, NO2, CO, O3 | Markable reduction in NO2 by 12–86%. | September 15, 2019–March 22, 2020 (pre-lockdown) March 23–June 20, 2020 (during lockdown) June 21–July 18, 2020 (post lockdown) |
General authority of Meteorology and Environment Protection Meteorological data – In -situ |
SO2 variations were not distinct. The other pollutants except O3 reduced. |
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Karachi, Pakistan | PM10, SO2, NO2, CO | PM10 reduced to 50% during lockdown SO2, NO2, CO reduced about 60%–70% | Feb25March 23, 2020 (before lockdown) |
Analysers | AQI during lockdown is either moderate or good | |
31 provinces in Iran | CO, SO2, NO2, O3 | Negative and positive correlations with density of confirmed COVID cases | Feb 19 March 22, 2020 | Sentinel 5P | SO2 was correlated more negatively | |
Almaty, Kazakhstan | PM2.5, SO2, NO2, CO, O3 Benzene, Toluene, Ethylbenzene-xylene |
CO and NO2 reduced by 49% and 35% during lockdown. O3 increased by 15% and SO2 by 7%. PM2.5 reduced by 21% compared to 2018–2019 same period. Benzene and toluene were 3 and 2 times higher and ethylbenzene and 0-xylene were 4 and 2.7 times compared to 20152019 same period |
March 19–April 14, 2020 Lockdown |
PM2.5 from Airkaz public air quality network Other air pollutants – Skymax technologies company Meteorological – Benzene, Toluene, Ethylbenzene-xylene – |
Trafic-free conditions did not improve air quality | |
Yangtze River Delta Region Shanghai, Hangzhou, Nanjing, Hefei | PM2.5, SO2, NOX, VOCs | SO2, NOX, PM2.5 and VOC's reduced by 26%,47%,46% and 57% during the most stringent level response period | January–March 2017–2020 |
Pollutants: Air Monitoring Data Centre of Ministry of Ecology and Environment of the People's Republic of China Meteorological data: NOAA, National climate data centre archive and National Data centre of Chinese Meteorology |
Daily PM2.5 during lockdown still ranged between 15 and 79 μg/m3, and O3 rebounded by 20.5% | |
Pierre Sicard et al. (2020) | Europe (Nice, France, Rome and Turin, Italy, Valencia, Spain) Wuhan, China | NOX, PM, O3 | Reduction in NOX in all cities ~56% PM in Wuhan ~42% and in Europe ~8% Increase in O3 by 17% in Europe and 36% in Wuhan | Before (1 January 2020 until start date of lockdown) and after (from start date to 8 April in Wuhan and until 18 April in European cities) lockdown | Local and regional agencies in charge of air monitoring stations | Reduction in NOX and PM and increase in O3 |
Continental United States (122 counties) | PM2.5 and NO2 | NO2 declined 25.5% and PM2.5 declined | January 8–Mach 12 (pre-lockdown) |
Open AQ API Country level Urban and rural – CDC National centre for health statistics. |
PM2.5 declined in urban counties | |
Sale city (Morocco) | PM10, SO2, NO2 | Decreased by 75%, 49%, 96% within a few days of lockdown | March 11–April 2, 2020 After and during lockdown | In-situ | Most significant variation in NO2 | |
Rome, Shanghai, Mumbai, Dubai, Delhi, Beijing, Los Angeles, New York, Zaragoza | PM2.5 | 32% reduction in New York, 4% in Los Angeles, 58% in Zaragoza, 24% in Rome, 11% in Dubai, 35% and 14% in Delhi and Mumbai, 50% in both Beijing and Shanghai. | Dec 2019–Mar 2020 compared with years 2017–2019 |
Purple Air Air Now US EPA |
In the major cities around the world suffering severely with Covid19, a decline in PM2.5 is observed. | |
Zone 1: Surat, Ankleshwar, Vadodara Zone 2: Ahmedabad, Gandhi Nagar, Zone 3: Jamnagar, Rajkot Zone 4: Bhuj and Palanpur. | PM2.5, PM10, SO2, NO2, CO, O3, AQI | Major improvements in Zones 2, 3; moderate improvements in Zones 1, 4. |
CPCB | 1 Jan 2020–20 Apr 2020 |
Overall improvement in AQI of 58% compared to previous year and increase in O3 by 16% to 58% due to less NO emissions. | |
Kolkata | PM10, NO2, SO2, O3 | Average of PM10, NO2, SO2, O3 reduced by 40% to 68%. | 24 February 2020 to 23 May 2020 (before lockdown) |
WBPCB CPCB |
Overall reduction of surface pollution in thunderstorm environment. | |
Delhi | PM2.5, PM10, SO2, NO2, CO, O3, AQI | PM10 and PM2.5 have witnessed maximum reduction >50%. | 24 Mar 2020 to 14 Apr 2020 (Same period 2019) |
CPCB DPCC |
About 54%, 49%, 43% 37% & 31% reduction in NAQI observed in Central, eastern, southern, western and northern parts of megacity Delhi. | |
Ghaziabad | PM2.5, PM10, NO2, SO2 | Major reduction in PM2.5 – 85.1% | 14 April 2020 Compared with 14 January 2020 | CPCB | Quality of air has started to improve. | |
Agra, Noida, Gurugram, Delhi | PM2.5, PM10, NO2, CO, O3 | PM2.5, PM10, CO reduced and O3 increased. | Before lockdown (02 March 2020–21 March 2020) |
CPCB ARL |
PM2.5 and PM10 for all north Indian cities were reduced more than 40%. O3 increased in Agra by 98%. |