ABSTRACT

Countries around the world introduced strict restrictions on movement and activities known as ‘lockdowns’ to restrict the spread of the novel coronavirus disease (COVID-19) from the end of 2019. A sudden improvement in air quality was observed globally as a result of these lockdowns. To provide insight into the changes in air pollution levels in response to the COVID-19 restrictions we have compared surface air quality data in Delhi during four phases of lockdown and the first phase of the restriction easing period (25 March to 30 June 2020) with data from a baseline period (2018–2019). Simultaneously, short-term exposure of PM_2.5 and O₃ attributed premature mortality were calculated to understand the health benefit of the change in air quality. Ground–level observations in Delhi showed that concentrations of PM₁₀, PM_2.5 and NO₂ dropped substantially in 2020 during the overall study period compared with the same period in previous years, with average reductions of ~49%, ~39%, and ~39%, respectively. An overall lower reduction in O₃ of ~19% was observed for Delhi. A slight increase in O₃ was found in Delhi’s industrial and traffic regions. The highest peak of the diurnal variation decreased substantially for all the pollutants at every phase. The decrease in PM_2.5 and O₃ concentrations in 2020, prevented 904 total premature deaths, a 60% improvement when compared to the figures for 2018–2019. The restrictions on human activities during the lockdown have reduced anthropogenic emissions and subsequently improved air quality and human health in one of the most polluted cities in the world.

Implications: I am submitting herewith the manuscript entitled “Unprecedented Reduction in Air Pollution and Corresponding Short-term Premature Mortality Associated with COVID-19 Forced Confinement in Delhi, India” for potential publishing in your journal.

The novelty of this research lies in: (1) we utilized ground-level air quality data in Delhi during four phases of lockdown and the first phase of unlocking period (25^th March to 30^th June) for 2020 as well as data from the baseline period (2018–2019) to provide an early insight into the changes in air pollution levels in response to the COVID-19 pandemic, (2) Chatarize the change of diurnal variation of the pollutants and (3) we assess the health risk due to PM_2.5 and O₃. Results from ground-level observations in Delhi showed that concentrations of PM₁₀, PM_2.5 and NO₂ substantially dropped in 2020 during the overall study period compared to the similar period in previous years, with an average reduction of ~49%, ~39%, and ~39%, respectively. In the case of O₃, the overall reduction was observed as ~19% in Delhi, while a slight increase was found in industrial and traffic regions. And consequently, the highest peak of the diurnal variation decreased substantially for all the pollutants. The health impact assessment of the changes in air quality indicated that 904 short-term premature deaths (~60%) were prevented due to the decline in PM_2.5 and O₃ concentrations in the study period. The restrictions on human activities during the lockdown have reduced the anthropogenic emissions and subsequently improved air quality and human health in one of the most polluted cities in the world.

摘要

从 2019 年底开始，世界各国对行动和活动实行严格限制，称为“封锁”，以限制新型冠状病毒病 (COVID-19) 的传播。由于这些措施，全球空气质量突然改善封锁。为了深入了解空气污染水平因 COVID-19 限制而发生的变化，我们将德里在四个锁定阶段和限制放松期的第一阶段（2020 年 3 月 25 日至 6 月 30 日）期间的地表空气质量数据与基线期（2018-2019 年）的数据。同时，PM _2.5和 O ₃的短期暴露计算归因于过早死亡率以了解空气质量变化对健康的益处。德里的地面观测表明，与往年同期相比，2020 年整个研究期间PM ₁₀、PM _2.5和 NO _{2 的}浓度大幅下降，平均下降了~49%、~39% 和~分别为 39%。观察到德里的O ₃总体减少约 19%。在德里的工业和交通区域发现O ₃略有增加。各阶段所有污染物的日变化最高峰均大幅下降。PM _2.5和 O ₃的减少2020 年防止了 904 人过早死亡，与 2018-2019 年的数字相比提高了 60%。封锁期间对人类活动的限制减少了人为排放，随后在世界上污染最严重的城市之一改善了空气质量和人类健康。

影响：我在此提交题为“印度德里与 COVID-19 强制监禁相关的空气污染前所未有的减少和相应的短期过早死亡率”的手稿，以便在您的期刊上发表。

本研究的新颖之处在于：（1）我们利用了 2020 年四个锁定阶段和第一阶段解锁期（3 月25^日至6月 30^日）德里的地面空气质量数据以及来自德里的数据。基线期（2018-2019）提供对空气污染水平变化的早期洞察，以应对 COVID-19 大流行，（2）Chatarize 污染物的昼夜变化变化和（3）我们评估由于到 PM _2.5和 O ₃。德里地面观测结果显示，PM ₁₀、PM _2.5和 NO _{2 的}浓度与往年同期相比，2020 年整个研究期间大幅下降，平均分别下降约 49%、约 39% 和约 39%。在 O ₃的情况下，观察到德里的总体减少约 19%，而工业和交通地区则略有增加。因此，所有污染物的昼夜变化的最高峰都大幅下降。空气质量变化的健康影响评估表明，由于 PM _2.5和 O ₃的下降，防止了 904 例短期过早死亡（约 60%）研究期间的浓度。封锁期间对人类活动的限制减少了人为排放，随后在世界上污染最严重的城市之一改善了空气质量和人类健康。