Critical assessment of restrictive socioeconomic measures taken during the SARS-CoV-2 pandemic and their impact on air quality worldwide

Anna De Falco; Luciana Maria Baptista Ventura; Eduarda Santa-Helena; Guilherme Carneiro Meziat; Lígia Campos de Souza e Silva; Marcos Felipe de Souza Pedreira; Adriana Gioda

doi:10.5327/Z2176-94781270

Authors

Anna De Falco Pontifical Catholic University of Rio de Janeiro (PUC-Rio) - Brazil https://orcid.org/0000-0001-9549-2711
Luciana Maria Baptista Ventura Environmental Institute of Rio de Janeiro State (INEA) - Brazil https://orcid.org/0000-0002-2597-6830
Eduarda Santa-Helena Pontifical Catholic University of Rio de Janeiro (PUC-Rio) - Brazil https://orcid.org/0000-0003-3286-8771
Guilherme Carneiro Meziat Pontifical Catholic University of Rio de Janeiro (PUC-Rio) - Brazil https://orcid.org/0000-0002-8092-4689
Lígia Campos de Souza e Silva Pontifical Catholic University of Rio de Janeiro (PUC-Rio) - Brazil https://orcid.org/0000-0002-2765-3808
Marcos Felipe de Souza Pedreira Pontifical Catholic University of Rio de Janeiro (PUC-Rio) - Brazil https://orcid.org/0000-0002-5755-7438
Adriana Gioda Pontifical Catholic University of Rio de Janeiro (PUC-Rio) - Brazil https://orcid.org/0000-0002-5315-5650

DOI:

https://doi.org/10.5327/Z2176-94781270

Keywords:

criteria pollutants; lockdown; vehicle emission; social distancing.

Abstract

The ongoing global pandemic of the coronavirus disease 2019 has been a public health emergency of international concern. Countries have adopted several restriction measures. Because of this fateful moment, it was possible to assess the effect of anthropogenic activities on air pollutants in an unprecedented way. This work aims to outline changes in the air quality levels of several cities worldwide after the COVID-19 pandemic. Data on the criteria pollutants found in these cities before and during the pandemic were used to evaluate air quality performance. The collection of most of the data was possible thanks to the constant monitoring methods applied in some countries. The severe limitation of people’s movements significantly reduced pollutants concentration, mainly due to the traffic of vehicles. Carbon monoxide, sulfur dioxide, nitrogen dioxide, particulate matter 2.5 μm, and particulate matter 10 μm (CO, SO₂, NO₂, PM_2.5, and PM₁₀) concentration reductions were observed due to more restrictive or flexible lockdowns. In almost all cities evaluated, WHO’s air quality guidelines have been achieved, except for tropospheric ozone, which has been increasing with the reduction of nitric oxides (NOx) emissions. The increment in the concentrations of the pollutants immediately after the end of the restrictions is an indication that control strategies must be implemented to improve air quality.

Downloads

Download data is not yet available.

References

Andrade, M.F.; Kumar, P.; Freitas, E.D.; Ynoue, R.Y.; Martins, J.; Martins, L.D.; Nogueira, T.; Perez-Martinez, P.; Miranda, R.M.; Albuquerque, T.; Gonçalves, F.L.T.; Oyama, B.; Zhang, Y. 2017. Air quality in the megacity of São Paulo: Evolution over the last 30 years and future perspectives. Atmospheric Environment, v. 159, 66-82. https://doi.org/10.1016/j.atmosenv.2017.03.051.

Berman, J.D.; Ebisu, K. 2020. Changes in U.S. air pollution during the COVID-19 pandemic. Science of the Total Environment, v. 739, 139864. https://doi.org/10.1016/j.scitotenv.2020.139864.

Biswas, M.S.; Ghude, S.D.; Gurnale, D.; Prabhakaran, T.; Mahajan, A.S. 2019. Simultaneous observations of nitrogen dioxide, formaldehyde and ozone in the indo-gangetic plain. Aerosol and Air Quality Research, v. 19, (8), 1749-1764. https://doi.org/10.4209/aaqr.2018.12.0484.

Bolaño-Ortiz, T.R.; Pascual-Flores, R.M.; Puliafito, S.E.; Camargo-Caicedo, Y.; Berná-Peña, L.L.; Ruggeri, M.F.; Lopez-Noreña, A.I.; Tames, M.F.; Cereceda-Balic, F. 2020. Spread of COVID-19, meteorological conditions and air quality in the city of Buenos Aires, Argentina: two facets observed during its pandemic lockdown. Atmosphere, v. 11, (10), 1045. https://doi.org/10.3390/atmos11101045.

Bontempi, E. 2020. First data analysis about possible COVID-19 virus airborne diffusion due to air particulate matter (PM): The case of Lombardy (Italy). Environmental Research, v. 186, 109639. https://doi.org/10.1016/j.envres.2020.109639

Carugno, M.; Lagazio, C.; Baccini, M.; Consonni, D.; Bertazzi, P.A.; Biggeri, A. 2017. Fine airborne particles: when alarming levels are the standard. Public Health, v. 143, 8-13. https://doi.org/10.1016/j.puhe.2016.10.024.

Chauhan, A.; Singh, R.P. 2020. Decline in PM2.5 concentrations over major cities around the world associated with COVID-19. Environmental Research, v. 187, 109634. https://doi.org/10.1016/j.envres.2020.109634.

Chen, T.-F.; Chang, K.-H.; Tsai, C.Y. 2017. Modeling approach for emissions reduction of primary PM 2.5 and secondary PM 2.5 precursors to achieve the air quality target. Atmospheric Research, v. 192, 11-18. https://doi.org/10.1016/j.atmosres.2017.03.018.

Cohen, A.J.; Brauer, M.; Burnett, R.; Anderson, H.R.; Frostad, J.; Estep, K.; Balakrishnan, K.; Brunekreef, B.; Dandona, L.; Dandona, R.; Feigin, V.; Freedman, G.; Hubbell, B.; Jobling, A.; Kan, H.; Knibbs, L.; Liu, Y.; Martin, R.; Morawska, L.; Pope, C.A.; Shin, H.; Straif, K.; Shaddick, G.; Thomas, M.; Van Dingenen, R.; Van Donkelaar, A.; Vos, T.; Murray, C.J.L.; Forouzanfar, M.H. 2017. Estimates and 25-year trends of the global burden of disease attributable to ambient air pollution: an analysis of data from the Global Burden of Diseases Study 2015. Lancet, v. 389, (10082), 1907-1918. https://doi.org/10.1016/s0140-6736(17)30505-6.

Collivignarelli, M.C.; Abbà, A.; Bertanza, G.; Pedrazzani, R.; Ricciardi, P.; Miino, M.C. 2020. Lockdown for CoViD-2019 in Milan: What are the effects on air quality? Science of the Total Environment, v. 732, 139280. https://doi.org/10.1016/j.scitotenv.2020.139280.

Dang, R.; Liao, H. 2019. Radiative forcing and health impact of aerosols and ozone in China as the consequence of clean air actions over 2012–2017. Geophysical Research Letters, v. 46, (21), 12511-12519. https://doi.org/10.1029/2019GL084605.

Dantas, G.; Siciliano, B.; França, B.B.; Silva, C.M.; Arbilla, G. 2020. The impact of COVID-19 partial lockdown on the air quality of the city of Rio de Janeiro, Brazil. Science of the Total Environment, v. 729, 139085. https://doi.org/10.1016/j.scitotenv.2020.139085.

da Silva, C.M.; Silva, L.L.; Correa, S.M.; Arbilla, G. 2018. A minimum set of ozone precursor volatile organic compounds in an urban environment. Atmospheric Pollution Research, v. 9, (2), 369-378. https://doi.org/10.1016/j.apr.2017.11.002.

Diário Oficial do Estado de São Paulo. 2020. Decreto nº 64.881, de 22 de março de 2020. Diário Oficial do Estado de São Paulo, São Paulo.

Donateo, A.; Dinoi, A.; Pappaccogli, G. 2021. Impact on ultrafine particles concentration and turbulent fluxes of SARS-CoV-2 lockdown in a suburban area in Italy. Atmosphere, v. 12, (3), 407. https://doi.org/10.3390/atmos12030407.

Dong, E.; Du, H.; Gardner, L. 2020. An interactive web-based dashboard to track COVID-19 in real time. The Lancet Infectious Diseases, v. 20, (5), 533-534. https://doi.org/10.1016/S1473-3099(20)30120-1.

Donzelli, G.; Cioni, L.; Cancellieri, M.; Llopis-Morales, A.; Morales-Suárez-Varela, M. 2021. Relations between air quality and Covid-19 lockdown measures in Valencia, Spain. International Journal of Environmental Research and Public Health, v. 18, (5), 2296. https://doi.org/10.3390%2Fijerph18052296.

DPCM. 2020a. Decree of the President of the Council of Ministers of the Italian Republic of March 1, 2020 - Further Implementing Provisions of the Decree-Law of 23 February 2020, n. 6, Containing Urgent Measures Regarding the Containment and Manage-ment of the Epidemiological Emergency from COVID-19. Gazzetta Ufficiale.

DPCM. 2020b. Decree of the President of the Council of Ministers of the Italian Republic of March 22, 2020 - Further Implementing Provisions of the Decree-Law of February 23, 2020, n. 6, Containing Urgent Measures Regarding the Containment and Management of the Epidemiological Emergency from COVID-19. Gazzetta Ufficiale.

Dragomir, C.M.; Voiculescu, M.; Constantin, D.-E.; Georgescu, L.P. 2015. Prediction of the NO2 concentration data in an urban area using multiple regression and neuronal networks. AIP Conference Proceedings, 1694, 040003. https://doi.org/10.1063/1.4937255.

European Space Agency (ESA). 2020. Coronavirus lockdown leading to drop in pollution across Europe. ESA, Europe.

GBD 2019 Demographics Collaborators. 2020. Global age-sex-specific fertility, mortality, healthy life expectancy (HALE), and population estimates in 204 countries and territories, 1950-2019: a comprehensive demographic analysis for the Global Burden of Disease Study 2019. Lancet, 396, (10258), 1160-1203. https://doi.org/10.1016/S0140-6736(20)30977-6.

Gioda, A.; La Cruz, A.H.; Almeida, A.C.L.B.; Justo, E.P.S.; Beringui, K.; Ventura, L.M.B.; Ramos, M.B.; Gomes, R.G.S.; Lionel-Mateus, V.; Valle, P.H.R. 2020.

Grasselli, G.; Pesenti, A.; Cecconi, M. 2020. Critical Care Utilization for the COVID-19 Outbreak in Lombardy, Italy. Jama, v. 323, (16), 1545-1546. https://doi.org/10.1001/jama.2020.4031.

Han, D.; Gao, S.; Fu, Q.; Cheng, J.; Chen, X.; Xu, H.; Liang, S.; Zhou, Y.; Ma, Y. 2018. Do volatile organic compounds (VOCs) emitted from petrochemical industries affect regional PM2.5? Atmospheric Research, v. 209, 123-130. https://doi.org/10.1016/j.atmosres.2018.04.002.

Heneghan, C.; Brassey, J.; Jefferson, T. 2020. COVID-19: What proportion are asymptomatic? The Centre for Evidence-Based Medicine.

Huang, C.; Wang, Y.; Li, X.; Ren, L.; Zhao, J.; Hu, Y.; Zhang, L.; Fan, G.; Xu, J.; Gu, X.; Cheng, Z.; Yu, T.; Xia, J.; Wei, Y.; Wu, W.; Xie, X.; Yin, W.; Li, H.; Liu, M.; Xiao, Y.; Gao, H.; Guo, L.; Xie, J.; Wang, G.; Jiang, R.; Gao, Z.; Jin, Q.; Wang, J.; Cao, B. 2020. Clinical features of patients infected with 2019 novel coronavirus in Wuhan, China, v. 395, (10223), 497-506. https://doi.org/10.1016/s0140-6736(20)30183-5.

IQAir. 2020. Covid-19 Air Quality Report (Accessed Dec, 2021) at:. https://www2.iqair.com/sites/default/files/documents/REPORT-COVID-19-Impact-on-Air-Quality-in-10-Major-Cities_V6.pdf.

IQAir. 2021. 2020 World air quality report (Accessed Dec, 2021) at:. https://www.iqair.com/world-air-quality-report.

IQAir. World's most polluted cities 2020 (PM2.5).

Jiang, X.Q.; Mei, X.D.; Feng, D. 2016. Air pollution and chronic airway diseases: what should people know and do? Journal of Thoracic Disease, v. 8, (1), E31-40. https://doi.org/10.3978/j.issn.2072-1439.2015.11.50.

Kuerban, M.; Waili, Y.; Fan, F.; Liu, Y.; Qin, W.; Dore, A.J.; Peng, J.; Xu, W.; Zhang, F. 2020. Spatio-temporal patterns of air pollution in China from 2015 to 2018 and implications for health risks. Environment Pollution, v. 258, 113659. https://doi.org/10.1016/j.envpol.2019.113659.

Kumar, P.; Morawska, L. 2019. Could fighting airborne transmission be the next line of defence against COVID-19 spread? City and Environment Interactions. City and Environment Interactions, v. 4, 100033. https://doi.org/10.1016/j.cacint.2020.100033.

Kumari, P.; Toshniwal, D. 2020. Impact of lockdown on air quality over major cities across the globe during COVID-19 pandemic. Urban Climate, v. 34, 100719. https://doi.org/10.1016/j.uclim.2020.100719.

Leung, N.H.L.; Chu, D.K.W.; Shiu, E.Y.C.; Chan, K.-H.; McDevitt, J.J.; Hau, B.J.P.; Yen, H.-L.; Li, Y.; Ip, D.K.M.; Peiris, J.S.M.; Seto, W.H.; Leung, G.M.; Milton, D.K.; Cowling, B.J. 2020. Respiratory virus shedding in exhaled breath and efficacy of face masks. Nature Medicine, 26, (5), 676-680. https://doi.org/10.1038/s41591-020-0843-2.

Li, K.; Jacob, D.J.; Liao, H.; Shen, L.; Zhang, Q.; Bates, K.H. 2018. Anthropogenic drivers of 2013–2017 trends in summer surface ozone in China. Proceedings of the National Academy of Sciences, v. 116, (2), 422-427. https://doi.org/10.1073/pnas.1812168116.

Mahato, S.; Pal, S.; Ghosh, K.G. 2020. Effect of lockdown amid COVID-19 pandemic on air quality of the megacity Delhi, India. Science of The Total Environment, v. 730, 139086. https://doi.org/10.1016/j.scitotenv.2020.139086.

Man, H.; Liu, H.; Niu, H.; Wang, K.; Deng, F.; Wang, X.; Xiao, Q.; Hao, J. 2020. VOCs evaporative emissions from vehicles in China: Species characteristics of different emission processes. Environmental Science and Ecotechnology, v. 1, 100002. https://doi.org/10.1016/j.ese.2019.100002.

Maneesh P; El Alaoui, A. 2020. How countries of south mitigate COVID-19: models of Morocco and Kerala, India. Electronic Research Journal of Social Sciences and Humanities, v. 2, (2), 16-28. https://doi.org/10.2139/ssrn.3567898.

Martins, E.M.; Meireles, A.R.; Magalhaes, F.R.; Carvalho, J.B.B.; Ribeiro, M.M. 2017. Concentrações de poluentes atmosféricos no Rio de Janeiro em relação a normas nacionais e internacionais. Revista Internacional de Ciências, v. 7, (1), 32-48. https://doi.org/10.12957/ric.2017.25799.

Massarotto, F. 2021. Itália Enfrenta Novo Lockdown, mas Dessa Vez Considerado "Light". Época.

Mendez-Espinosa, J.F., Rojas, N.Y.; Vargas, J.; Pachón, J.E.; Belalcazar, L.C.; Ramírez, O. 2020. Air quality variations in Northern South America during the COVID-19 lockdown. Science Total Environment, v. 749, 141621. https://doi.org/10.1016/j.scitotenv.2020.141621.

Nakada, L.Y.K.; Urban, R.C. 2020. COVID-19 pandemic: Impacts on the air quality during the partial lockdown in São Paulo state, Brazil. Science of The Total Environment, v. 730, 139087. https://doi.org/10.1016/j.scitotenv.2020.139087.

Noda, L.; Nóbrega, A.B.E.Q.; Silva Júnior, J.B.M.; Schmidlin, F.; Labaki, L. 2021. COVID-19: Has social isolation reduced the emission of pollutants in the megacity of São Paulo—Brazil? Environment, Development and Sustainability, 1-19. https://doi.org/10.1007/s10668-020-01166-2.

Ocak, S.; Turalioglu, F. 2008. Effect of meteorology on the atmospheric concentrations of traffic- related pollutants in Erzurum, Turkey #. Journal of International Environmental Application and Science, v. 3, (5), 325-335.

Ortiz, C.; Linares, C.; Carmona, R.; Díaz, J. 2017. Evaluation of short-term mortality attributable to particulate matter pollution in Spain. Environmental Pollution, v. 224, 541-551. https://doi.org/10.1016/j.envpol.2017.02.037.

Otmani, A.; Benchrif, A.; Tahri, M.; Bounakhla, M.; Chakir, E.M.; Bouch, M.E.; Krombi, M. 2020. Impact of Covid-19 lockdown on PM10, SO2 and NO2 concentrations in Salé City (Morocco). Science of The Total Environment, v. 735, 139541. https://doi.org/10.1016/j.scitotenv.2020.139541.

PlumeLabs. 2021. AQI World Map Air 2021 (Accessed Dec, 2021) at:. air.plumelabs.com/en/.

Rahaman, S.; Jahangir, S.; Chen, R.; Kumar, P.; Thakur, S. 2021. COVID-19’s lockdown effect on air quality in Indian cities using air quality zonal modeling. Urban Climate, v. 36, 100802. https://doi.org/10.1016/j.uclim.2021.100802.

Reid, C.E.; Considine, E.M.; Watson, G.L.; Telesca, D.; Pfister, G.G.; Jerrett, M. 2019. Associations between respiratory health and ozone and fine particulate matter during a wildfire event. Environment International, v. 129, 291-298. https://doi.org/10.1016/j.envint.2019.04.033.

Rodríguez-Urrego, D.; Rodríguez-Urrego, L. 2020. Air quality during the COVID-19: PM2.5 analysis in the 50 most polluted capital cities in the world. Environmental Pollution, 266, part 1, 115042. https://doi.org/10.1016/j.envpol.2020.115042.

Roy, S.; Singha, N. 2021. Reduction in concentration of PM2.5 in India’s top most polluted cities: with special reference to post-lockdown period. Air Quality, Atmosphere & Health, v. 14, (5), 715-723. https://doi.org/10.1007/s11869-020-00974-9.

Ryan, R.G., Silver, J.D.; Schofield, R. 2021. Air quality and health impact of 2019–20 Black Summer megafires and COVID-19 lockdown in Melbourne and Sydney, Australia. Environmental Pollution, v. 274, 116498. https://doi.org/10.1016/j.envpol.2021.116498.

Sahoo, P.K.; Salomão, G.N.; Ferreira Júnior, J.S.; Farias, D.L.; Powell, M.A.; Mittal, S.; Garg, V.K. 2021. COVID-19 lockdown: a rare opportunity to establish baseline pollution level of air pollutants in a megacity, India. Aerosol and Air Quality Research, v. 18, (5), 1269-1286. https://doi.org/10.1007%2Fs13762-021-03142-3

Sharma, S.; Zhang, M.; Anshika; Gao, J.; Zhang, H.; Kota, S.H. 2020. Effect of restricted emissions during COVID-19 on air quality in India. Science of the Total Environment, v. 728, 138878. https://doi.org/10.1016/j.scitotenv.2020.138878.

Siciliano, B.; Dantas, G.; Silva, C.M.; Arbilla, G. 2020. Increased ozone levels during the COVID-19 lockdown: Analysis for the city of Rio de Janeiro, Brazil. Science of the Total Environment, v. 737, 139765. https://doi.org/10.1016/j.scitotenv.2020.139765.

Soni, M.; Verma, S.; Jethava, H.; Payra, S.; Lamsal, L.; Gupta, P.; Singh, J. 2021. Impact of COVID-19 on the air quality over China and India using long-term (2009-2020) multi-satellite data. Aerosol and Air Quality Research, v. 21, (3), 200295. https://doi.org/10.4209/aaqr.2020.06.0295.

Sulaymon, I.D.; Zhang, Y.; Hopke, P.K.; Zhang, Y.; Hua, J.; Mei, X. 2021. COVID-19 pandemic in Wuhan: Ambient air quality and the relationships between criteria air pollutants and meteorological variables before, during, and after lockdown. Atmospheric Research, v. 250, 105362. https://doi.org/10.1016/j.atmosres.2020.105362.

Sur, K.; Verma, V.K.; Pateriya, B. 2021. Variation of tropospheric NO2 over Indo-Gangetic plain during COVID-19 outbreak in India. Spacial Information Research, v. 29, (6), 841-855. https://doi.org/10.1007%2Fs41324-021-00399-1.

Thorpe, A.; Harrison, R.M. 2008. Sources and properties of non-exhaust particulate matter from road traffic: A review. Science of the Total Environment, v. 400, (1-3), 270-282. https://doi.org/10.1016/j.scitotenv.2008.06.007.

Tobías, A.; Carnerero, C.; Reche, C.; Massagué, J.; Via, M.; Minguillón, M.C.; Alastuey, A.; Querol, X. 2020. Changes in air quality during the lockdown in Barcelona (Spain) one month into the SARS-CoV-2 epidemic. Science of the Total Environment, v. 726, 138540. https://doi.org/10.1016/j.scitotenv.2020.138540.

Van Donkelaar, A.; Martin, R.V.; Brauer, M.; Boys, B.L. 2015. Use of satellite observations for long-term exposure assessment of global concentrations of fine particulate matter. Environmental Health Perspectives, v. 123, (2), 135-143. https://doi.org/10.1289/ehp.1408646.

Venkat Ratnam, M.; Prasad, P.; Akhil Raj, S.T.; Hoteit, I. 2021. Effect of lockdown due to COVID-19 on the aerosol and trace gases spatial distribution over India and adjoining regions. Aerosol and Air Quality Research, v. 21, (2), 200397.

Venter, Z.S.; Aunan, K.; Chowdhury, S.; Lelieveld, J. 2020. COVID-19 lockdowns cause global air pollution declines with implications for public health risk. medRxiv, 2020.04.10.20060673.

Ventura, L.M.B.; Mateus, V.L.; Almeida, A.C.S.L.; Wanderley, K.B.; Taira, F.T.; Saint’Pierre, T.D.; Gioda, A. 2017. Chemical composition of fine particles (PM2.5): water-soluble organic fraction and trace metals. Air Quality, Atmosphere & Health, v. 10, (7), 845-852. https://doi.org/10.1007/s11869-017-0474-z

Ventura, L.M.B.; Pinto, F.O.; Gioda, A.; D’Agosto, M.A. 2020. Inspection and maintenance programs for in-service vehicles: An important air pollution control tool. Sustainable Cities and Society, v. 53, 101956. https://doi.org/10.1016/j.scs.2019.101956.

Ventura, L.M.B.; Soares, L.M.; Lopes, J.S. 2019. Evolução da política do controle da poluição veicular nos últimos 30 anos. Appris, Curitiba.

Wang, Q.; Li, S. 2021. Nonlinear impact of COVID-19 on pollutions - Evidence from Wuhan, New York, Milan, Madrid, Bandra, London, Tokyo and Mexico City. Sustainable Cities and Society, v. 65, 102629. https://doi.org/10.1016/j.scs.2020.102629.

Wang, Q.; Su, M. 2020. A preliminary assessment of the impact of COVID-19 on environment – A case study of China. Science of the Total Environment, v. 728, 138915. https://doi.org/10.1016/j.scitotenv.2020.138915.

Wang, Y.; Yuan, Y.; Wang, Q.; Liu, C.; Zhi, Q.; Cao, J. 2020. Changes in air quality related to the control of coronavirus in China: Implications for traffic and industrial emissions. Science of the Total Environment, v. 731, 139133. https://doi.org/10.1016/j.scitotenv.2020.139133.

World Health Organization. (‎2021)‎. WHO global air quality guidelines: particulate matter (‎PM2.5 and PM10)‎, ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide. World Health Organization.

Zambrano-Monserrate, M.A.; Ruano, M.A.; Sanchez-Alcalde, L. 2020. Indirect effects of COVID-19 on the environment. Science of the Total Environment, v. 728, 138813. https://doi.org/10.1016/j.scitotenv.2020.138813.

Zangari, S.; Hill, D.T.; Charette, A.T.; Mirowsky, J.E. 2020. Air quality changes in New York City during the COVID-19 pandemic. Science of the Total Environment, v. 742, 140496. https://doi.org/10.1016/j.scitotenv.2020.140496.

Zeng, J.; Bao, R. 2021. The impacts of human migration and city lockdowns on specific air pollutants during the COVID-19 outbreak: A spatial perspective. Journal of Environmental Management, v. 282, 111907. https://doi.org/10.1016/j.jenvman.2020.111907.

Zhao, X.; Zhou, W.; Han, L.; Locke, D. 2019. Spatiotemporal variation in PM 2.5 concentrations and their relationship with socioeconomic factors in China's major cities. Environment International, v. 133, part A, 105145. https://doi.org/10.1016/j.envint.2019.105145.

Zhu, N.; Zhang, D.; Wang, W.; Li, X.; Yang, B.; Song, J.; Zhao, X.; Huang, B.; Shi, W.; Lu, R.; Niu, P.; Zhan, F.; Ma, X.; Wang, D.; Xu, W.; Wu, G.; Gao, G.F.; Tan, W. 2020. A novel coronavirus from patients with pneumonia in China, 2019. New England Journal of Medicine, v. 382, (8), 727-733. https://doi.org/10.1056/nejmoa2001017.