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      Changes in criteria air pollution levels in the US before, during, and after Covid-19 stay-at-home orders: Evidence from regulatory monitors

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          Abstract

          The widespread and rapid social and economic changes from Covid-19 response might be expected to dramatically improve air quality. However, national monitoring data from the US Environmental Protection Agency for criteria pollutants (PM 2.5, ozone, NO 2, CO, PM 10) provide inconsistent support for that expectation. Specifically, during stay-at-home orders, average PM 2.5 levels were slightly higher (~10% of its multi-year interquartile range [IQR]) than expected; average ozone, NO 2, CO, and PM 10 levels were slightly lower (~30%, ~20%, ~27%, and ~1% of their IQR, respectively) than expected. The timing of peak anomaly, relative to the stay-at-home orders, varied by pollutant (ozone: 2 weeks before; NO 2, CO: 3 weeks after; PM 10: 2 weeks after); but, by 5–6 weeks after stay-at-home orders, the concentration anomalies appear to have ended. For PM 2.5, ozone, CO, and PM 10, no US state had lower-than-expected pollution levels for all weeks during stay-at-home-orders; for NO 2, only Arizona had lower-than-expected levels for all weeks during stay-at-home orders. Our findings show that the enormous changes from the Covid-19 response have not lowered PM 2.5 levels across the US beyond their normal range of variability; for ozone, NO 2, CO, and PM 10 concentrations were lowered but the reduction was modest and transient.

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          Highlights

          • •

            Impacts of stay-at-home orders on air pollution were evaluated using EPA monitoring data from 100s of stations across the US.

          • •

            During stay-at-home orders, ozone, NO 2, CO and PM 10 were lower and PM 2.5 were higher than expected levels by 1%-30% of their IQR.

          • •

            Concentration anomalies ended only 5-6 weeks after stay-at-home orders were issued.

          • •

            Ozone, NO 2, and CO concentrations returned to expected levels and PM 2.5 and PM 10 levels were higher than expected.

          • •

            Reductions in ozone, NO 2, and CO levels were modest and short-lived. PM 10 levels did not change and PM 2.5 levels increased.

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          Effect of restricted emissions during COVID-19 on air quality in India

          Shubham Sharma, Mengyuan Zhang, Anshika … (2020)
          The effectiveness and cost are always top factors for policy-makers to decide control measures and most measures had no pre-test before implementation. Due to the COVID-19 pandemic, human activities are largely restricted in many regions in India since mid-March of 2020, and it is a progressing experiment to testify effectiveness of restricted emissions. In this study, concentrations of six criteria pollutants, PM10, PM2.5, CO, NO2, ozone and SO2 during March 16th to April 14th from 2017 to 2020 in 22 cities covering different regions of India were analysed. Overall, around 43, 31, 10, and 18% decreases in PM2.5, PM10, CO, and NO2 in India were observed during lockdown period compared to previous years. While, there were 17% increase in O3 and negligible changes in SO2. The air quality index (AQI) reduced by 44, 33, 29, 15 and 32% in north, south, east, central and western India, respectively. Correlation between cities especially in northern and eastern regions improved in 2020 compared to previous years, indicating more significant regional transport than previous years. The mean excessive risks of PM reduced by ~52% nationwide due to restricted activities in lockdown period. To eliminate the effects of possible favourable meteorology, the WRF-AERMOD model system was also applied in Delhi-NCR with actual meteorology during the lockdown period and an un-favourable event in early November of 2019 and results show that predicted PM2.5 could increase by only 33% in unfavourable meteorology. This study gives confidence to the regulatory bodies that even during unfavourable meteorology, a significant improvement in air quality could be expected if strict execution of air quality control plans is implemented.
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            Effect of lockdown amid COVID-19 pandemic on air quality of the megacity Delhi, India

            Susanta Mahato, Swades Pal, Krishna Gopal Ghosh (2020)
            Amid the COVID-19 pandemic, a nationwide lockdown is imposed in India initially for three weeks from 24th March to 14th April 2020 and extended up to 3rd May 2020. Due to the forced restrictions, pollution level in cities across the country drastically slowed down just within few days which magnetize discussions regarding lockdown to be the effectual alternative measures to be implemented for controlling air pollution. The present article eventually worked on this direction to look upon the air quality scenario amidst the lockdown period scientifically with special reference to the megacity Delhi. With the aid of air quality data of seven pollutant parameters (PM10, PM2.5, SO2, NO2, CO, O3 and NH3) for 34 monitoring stations spread over the megacity we have employed National Air Quality Index (NAQI) to show the spatial pattern of air quality in pre and during-lockdown phases. The results demonstrated that during lockdown air quality is significantly improved. Among the selected pollutants, concentrations of PM10 and PM2.5 have witnessed maximum reduction (>50%) in compare to the pre-lockdown phase. In compare to the last year (i.e. 2019) during the said time period the reduction of PM10 and PM2.5 is as high as about 60% and 39% respectively. Among other pollutants, NO2 (−52.68%) and CO (−30.35%) level have also reduced during-lockdown phase. About 40% to 50% improvement in air quality is identified just after four days of commencing lockdown. About 54%, 49%, 43%, 37% and 31% reduction in NAQI have been observed in Central, Eastern, Southern, Western and Northern parts of the megacity. Overall, the study is thought to be a useful supplement to the regulatory bodies since it showed the pollution source control can attenuate the air quality. Temporary such source control in a suitable time interval may heal the environment.
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              Changes in air quality during the lockdown in Barcelona (Spain) one month into the SARS-CoV-2 epidemic

              Aurelio Tobías, Cristina Carnerero, Cristina Reche … (2020)
              Lockdown measures came into force in Spain from March 14th, two weeks after the start of the SARS-CoV-2 epidemic, to reduce the epidemic curve. Our study aims to describe changes in air pollution levels during the lockdown measures in the city of Barcelona (NE Spain), by studying the time evolution of atmospheric pollutants recorded at the urban background and traffic air quality monitoring stations. After two weeks of lockdown, urban air pollution markedly decreased but with substantial differences among pollutants. The most significant reduction was estimated for BC and NO2 (−45 to −51%), pollutants mainly related to traffic emissions. A lower reduction was observed for PM10 (−28 to −31.0%). By contrast, O3 levels increased (+33 to +57% of the 8 h daily maxima), probably due to lower titration of O3 by NO and the decrease of NOx in a VOC-limited environment. Relevant differences in the meteorology of these two periods were also evidenced. The low reduction for PM10 is probably related to a significant regional contribution and the prevailing secondary origin of fine aerosols, but an in-depth evaluation has to be carried out to interpret this lower decrease. There is no defined trend for the low SO2 levels, probably due to the preferential reduction in emissions from the least polluting ships. A reduction of most pollutants to minimal concentrations are expected for the forthcoming weeks because of the more restrictive actions implemented for a total lockdown, which entered into force on March 30th. There are still open questions on why PM10 levels were much less reduced than BC and NO2 and on what is the proportion of the abatement of pollution directly related to the lockdown, without meteorological interferences.
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                Author and article information

                Journal
                Journal ID (nlm-ta): Sci Total Environ
                Journal ID (iso-abbrev): Sci Total Environ
                Title: The Science of the Total Environment
                Publisher: Published by Elsevier B.V.
                ISSN (Print): 0048-9697
                ISSN (Electronic): 1879-1026
                Publication date PMC-release: 2 January 2021
                Publication date (Print): 15 May 2021
                Publication date (Electronic): 2 January 2021
                Volume: 769
                Page: 144693
                Affiliations
                [a ]Department of Civil and Environmental Engineering, University of Washington, Seattle, WA, United States of America
                [b ]Department of Civil and Environmental Engineering, University of California, Berkeley, Berkeley, CA, United States of America and School of Public Health, University of California, Berkeley, Berkeley, CA, United States of America
                [c ]Department of Soil, Water, and Climate, University of Minnesota, St. Paul, MN, United States of America
                [d ]Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, PA, United States of America
                Author notes
                [* ]Corresponding author.
                Article
                Publisher Item ID: S0048-9697(20)38226-7 Publisher ID: 144693
                DOI: 10.1016/j.scitotenv.2020.144693
                PMC ID: 7831446
                PubMed ID: 33736238
                SO-VID: f2b3cf76-7a2e-4130-867f-b3ebafabbbb9
                Copyright © © 2020 Published by Elsevier B.V.
                License:

                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
                Date received : 30 October 2020
                Date revision received : 16 December 2020
                Date accepted : 18 December 2020
                Categories
                Subject: Article

                ScienceOpen disciplines: General environmental science
                Keywords: air pollution and covid-19,air pollution and stay-at-home orders,criteria air pollution,stay-at-home orders,covid-19
                Data availability:
                ScienceOpen disciplines: General environmental science
                Keywords: air pollution and covid-19, air pollution and stay-at-home orders, criteria air pollution, stay-at-home orders, covid-19

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