Abstract
The lockdowns due to the COVID-19 pandemic have been reported to reduce ambient air pollution in many cities globally. This study aims to examine whether air pollution dropped in Memphis, a typical U.S. metropolitan city and transportation hub, during the lockdown from 25 March to 4 May, 2020. Daily air pollution data measured at five representative monitoring stations in the Memphis Metropolitan Area were downloaded from the U.S. Environmental Protection Agency’s Air Quality System. The mean concentrations of fine particulate matter (PM2.5), nitrogen dioxide (NO2), and ozone during the lockdown were compared with the baseline concentrations measured during the same periods in 2017–2019 using linear regression models. The average vehicle miles traveled (VMT) reduced by 57% in this region during the lockdown compared to that during 1–24 March, 2020. The mean (± standard deviation) concentrations of PM2.5, NO2, and ozone were 7.5 ± 2.6 μg/m3, 16.5 ± 9.4 ppb, and 44.5 ± 8.4 ppb, respectively, during the lockdown. They did not statistically differ from the baseline concentrations, nor were they lower than the mean concentrations in the prior month (25 February–24 March, 2020), after accounting for meteorological conditions. The lack of effect could be explained by the small contribution of traffic emissions to air pollution. The results suggest that the “stay-at-home” order had an insignificant impact on reducing air pollution in Memphis.
Highlights
The worldwide lockdowns and stay-at-home orders to fight the COVID-19 pandemic have caused traffic reduction and industry and business closures
The results suggest that the “stay-at-home” order had an insignificant impact on reducing air pollution in Memphis
This study aims to examine whether a reduction in air pollution occurred during the lockdown period in a typical mid-size U.S metropolitan reduction in air pollution occurred during the lockdown period in a typical mid-size U.S
Summary
The worldwide lockdowns and stay-at-home orders to fight the COVID-19 pandemic have caused traffic reduction and industry and business closures. Air pollution drops have produced a beneficial side effect observed in many major cities globally. A Google search on 7 May, 2020, using “Air pollution drops, Coronavirus” as key search terms yielded about 27,000,000 results. NASA satellite images and numerous photos clearly displayed the dramatic contrast of air pollution levels between preand post-pandemic lockdown periods in China [1]. A recent report compared fine particulate matter (PM2.5 ) concentrations before and during the pandemic in 10 major global cities under lockdown and found that nine cities experienced reductions compared to the same period in 2019 [2]. Researchers have speculated that these reductions might lower air pollution associated mortality rates [3]
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