The COVID-19 containment response policies (CRPs) had a major impact on air quality (AQ). These CRPs have been time-varying and location-specific. So far, despite having numerous studies on the effect of COVID-19 lockdown on AQ, a knowledge gap remains on the association between stringency of CRPs and AQ changes across the world, regions, nations, and cities. Here, we show that globally across 1851 cities (each more than 300 000 people) in 149 countries, after controlling for the impacts of relevant covariates (e.g., meteorology), Sentinel-5P satellite-observed nitrogen dioxide (NO₂) levels decreased by 4.9% (95% CI: 2.2, 7.6%) during lockdowns following stringent CRPs compared to pre-CRPs. The NO₂ levels did not change significantly during moderate CRPs and even increased during mild CRPs by 2.3% (95% CI: 0.7, 4.0%), which was 6.8% (95% CI: 2.0, 12.0%) across Europe and Central Asia, possibly due to population avoidance of public transportation in favor of private transportation. Among 1768 cities implementing stringent CRPs, we observed the most NO₂ reduction in more populated and polluted cities. Our results demonstrate that AQ improved when and where stringent COVID-19 CRPs were implemented, changed less under moderate CRPs, and even deteriorated under mild CRPs. These changes were location-, region-, and CRP-specific.

中文翻译：

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COVID-19 遏制响应政策和空气质量变化的严格性：1851 个城市的全球分析

COVID-19 遏制响应政策 (CRP) 对空气质量 (AQ) 产生了重大影响。这些 CRP 是时变的和特定于位置的。到目前为止，尽管对 COVID-19 锁定对 AQ 的影响进行了大量研究，但在全球、地区、国家和城市的 CRP 严格性与 AQ 变化之间的关联方面仍存在知识差距。在这里，我们展示了全球 149 个国家的 1851 个城市（每个城市超过 30 万人），在控制了相关协变量（例如气象）的影响后，Sentinel-5P 卫星观测到的二氧化氮（NO ₂）水平下降了与之前的 CRP 相比，在严格的 CRP 之后的锁定期间为 4.9%（95% CI：2.2、7.6%）。NO ₂在中度 CRP 期间水平没有显着变化，甚至在轻度 CRP 期间增加了 2.3%（95% CI：0.7, 4.0%），在欧洲和中亚为 6.8%（95% CI：2.0, 12.0%），可能是由于民众避免公共交通，转而使用私人交通。在 1768 个实施严格 CRP 的城市中，我们观察到在人口和污染更严重的城市中 NO ₂减少最多。我们的结果表明，AQ 在实施严格的 COVID-19 CRP 的时间和地点有所改善，在中度 CRP 下变化较小，甚至在轻度 CRP 下恶化。这些变化是位置、区域和 CRP 特定的。