This paper aims to examine the effects of the COVID-19 pandemic on PM2.5 emissions in eight selected US cities with populations of more than 1 million. To this end, the study employs an asymmetric Fourier causality test for the period of January 15, 2020 to May 4, 2020. The outcomes indicate that positive shocks in COVID-19 deaths cause negative shocks in PM2.5 emissions for New York, San Diego, and San Jose. Moreover, in terms of cases, positive shocks in COVID-19 cause negative shocks in PM2.5 emissions for Los Angeles, Chicago, Phoenix, Philadelphia, San Antonio, and San Jose. Overall, the findings of the study highlight that the pandemic reduces environmental pressure in the largest cities of the USA. This implies that one of the rare positive effects of the virus is to reduce air pollution. Therefore, for a better environment, US citizens should review the impact of current production and consumption activities on anthropogenic environmental problems.

中文翻译：

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COVID-19 如何影响美国城市的环境污染？来自非对称傅里叶因果检验的证据

本文旨在研究 COVID-19 大流行对美国 8 个人口超过 100 万的选定城市 PM2.5 排放的影响。为此，该研究在 2020 年 1 月 15 日至 2020 年 5 月 4 日期间采用了非对称傅立叶因果检验。结果表明，COVID-19 死亡人数的正向冲击会导致纽约、圣路易斯的 PM2.5 排放受到负向冲击迭戈和圣何塞。此外，就案例而言，COVID-19 的正面冲击会对洛杉矶、芝加哥、凤凰城、费城、圣安东尼奥和圣何塞的 PM2.5 排放造成负面冲击。总体而言，该研究的结果强调，这种流行病减轻了美国最大城市的环境压力。这意味着该病毒罕见的积极影响之一是减少空气污染。因此，为了更好的环境，