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Air Quality Before and After COVID-19 Lockdown Phases Around New Delhi, India.
J Health Pollut. 2021 Jun; 11(30):210602.JH

Abstract

Background

The COVID-19 pandemic has had a deep global impact, not only from a social and economic perspective, but also with regard to human health and the environment. To restrict transmission of the virus, the Indian government enforced a complete nationwide lockdown except for essential services and supplies in phases from 25 March to 31 May 2020. Ambient air quality in and around New Delhi, one of the most polluted cities of world, was also impacted during this period.

Objective

The aim of the present study was to assess and understand the impact of four different lockdown phases (LD1, LD2, LD3 and LD4) on five air pollutants (particulate matter (PM) PM2.5, PM10, nitrogen oxide (NOx), sulfur dioxide (SO2) and ozone (O3)) compared to before lockdown (BLD) at 13 air monitoring stations in and around New Delhi.

Methods

Secondary data on five criteria pollutants for 13 monitoring stations in and around New Delhi for the period 1 March to 31 May 2020 was accessed from the Central Pollution Control Bard, New Delhi. Data were statistically analyzed across lockdown phases, meteorological variables, and prevailing air sources around the monitoring stations.

Results

Pollutant concentrations decreased during LD1 compared to BLD except for O3 at all stations. PM2.5 and PM10 remained either close to or higher than the National Ambient Air Quality Standards (NAAQS) due to prevailing high-speed winds. During lockdown phases, NO2 decreased, whereas O3 consistently increased at all stations. This was a paradoxical situation as O3 is formed via photochemical reactions among NOx and volatile organic compounds. Principal component analysis (PCA) extracted two principal components (PC1 and PC2) which explained up to 80% of cumulative variance in data. PM2.5, PM10 and NO2 were associated with PC1, whereas PC2 had loadings of either O3 only or O3 and SO2 depending upon monitoring station.

Conclusions

The present study found that air pollutants decreased during lockdown phases, but these decreases were specific to the site(s) and pollutant(s). The decrease in pollutant concentrations during lockdown could not be attributed completely to lockdown conditions as the planetary boundary layer increased two-fold during lockdown compared to the BLD phase. Such restrictions could be applied in the future to control air pollution but should be approached with caution.

Competing Interests

The authors declare no competing financial interests.

Authors+Show Affiliations

Centre of Excellence for Energy and Environmental Studies, Deenbandhu Chhotu Ram University of Science and Technology, Murthal, India.School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, India.Centre of Excellence for Energy and Environmental Studies, Deenbandhu Chhotu Ram University of Science and Technology, Murthal, India.School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, India.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

34267989

Citation

Chaudhary, Sudesh, et al. "Air Quality Before and After COVID-19 Lockdown Phases Around New Delhi, India." Journal of Health & Pollution, vol. 11, no. 30, 2021, p. 210602.
Chaudhary S, Kumar S, Antil R, et al. Air Quality Before and After COVID-19 Lockdown Phases Around New Delhi, India. J Health Pollut. 2021;11(30):210602.
Chaudhary, S., Kumar, S., Antil, R., & Yadav, S. (2021). Air Quality Before and After COVID-19 Lockdown Phases Around New Delhi, India. Journal of Health & Pollution, 11(30), 210602. https://doi.org/10.5696/2156-9614-11.30.210602
Chaudhary S, et al. Air Quality Before and After COVID-19 Lockdown Phases Around New Delhi, India. J Health Pollut. 2021;11(30):210602. PubMed PMID: 34267989.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Air Quality Before and After COVID-19 Lockdown Phases Around New Delhi, India. AU - Chaudhary,Sudesh, AU - Kumar,Sushil, AU - Antil,Rimpi, AU - Yadav,Sudesh, Y1 - 2021/05/28/ PY - 2020/09/18/received PY - 2021/01/22/accepted PY - 2021/7/16/entrez PY - 2021/7/17/pubmed PY - 2021/7/17/medline KW - air pollution KW - criteria pollutants KW - lockdown KW - meteorology SP - 210602 EP - 210602 JF - Journal of health & pollution JO - J Health Pollut VL - 11 IS - 30 N2 - Background: The COVID-19 pandemic has had a deep global impact, not only from a social and economic perspective, but also with regard to human health and the environment. To restrict transmission of the virus, the Indian government enforced a complete nationwide lockdown except for essential services and supplies in phases from 25 March to 31 May 2020. Ambient air quality in and around New Delhi, one of the most polluted cities of world, was also impacted during this period. Objective: The aim of the present study was to assess and understand the impact of four different lockdown phases (LD1, LD2, LD3 and LD4) on five air pollutants (particulate matter (PM) PM2.5, PM10, nitrogen oxide (NOx), sulfur dioxide (SO2) and ozone (O3)) compared to before lockdown (BLD) at 13 air monitoring stations in and around New Delhi. Methods: Secondary data on five criteria pollutants for 13 monitoring stations in and around New Delhi for the period 1 March to 31 May 2020 was accessed from the Central Pollution Control Bard, New Delhi. Data were statistically analyzed across lockdown phases, meteorological variables, and prevailing air sources around the monitoring stations. Results: Pollutant concentrations decreased during LD1 compared to BLD except for O3 at all stations. PM2.5 and PM10 remained either close to or higher than the National Ambient Air Quality Standards (NAAQS) due to prevailing high-speed winds. During lockdown phases, NO2 decreased, whereas O3 consistently increased at all stations. This was a paradoxical situation as O3 is formed via photochemical reactions among NOx and volatile organic compounds. Principal component analysis (PCA) extracted two principal components (PC1 and PC2) which explained up to 80% of cumulative variance in data. PM2.5, PM10 and NO2 were associated with PC1, whereas PC2 had loadings of either O3 only or O3 and SO2 depending upon monitoring station. Conclusions: The present study found that air pollutants decreased during lockdown phases, but these decreases were specific to the site(s) and pollutant(s). The decrease in pollutant concentrations during lockdown could not be attributed completely to lockdown conditions as the planetary boundary layer increased two-fold during lockdown compared to the BLD phase. Such restrictions could be applied in the future to control air pollution but should be approached with caution. Competing Interests: The authors declare no competing financial interests. SN - 2156-9614 UR - https://www.unboundmedicine.com/medline/citation/34267989/Air_Quality_Before_and_After_COVID_19_Lockdown_Phases_Around_New_Delhi_India_ DB - PRIME DP - Unbound Medicine ER -
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