Impact of the COVID-19 Lockdown on Air Quality and Resulting Public Health Benefits in the Mexico City Metropolitan Area

Abstract

Meteorology and long-term trends in air pollutant concentrations may obscure the results from short-term policies implemented to improve air quality. This study presents changes in CO, NO2, O3, SO2, PM10, and PM2.5 based on their anomalies during the COVID-19 partial (Phase 2) and total (Phase 3) lockdowns in Mexico City (MCMA). To minimise the impact of the air pollutant long-term trends, pollutant anomalies were calculated using as baseline truncated Fourier series, fitted with data from 2016 to 2019, and then compared with those from the lockdown. Additionally, days with stagnant conditions and heavy rain were excluded to reduce the impact of extreme weather changes. Satellite observations for NO2 and CO were used to contrast the ground-based derived results. During the lockdown Phase 2, only NO2 exhibited significant decreases (p < 0.05) of between 10 and 23% due to reductions in motor vehicle emissions. By contrast, O3 increased (p < 0.05) between 16 and 40% at the same sites where NO2 decreased. During Phase 3, significant decreases (p < 0.05) were observed for NO2 (43%), PM10 (20%), and PM2.5 (32%) in response to the total lockdown. Although O3 concentrations were lower in Phase 3 than during Phase 2, those did not decrease (p < 0.05) from the baseline at any site despite the total lockdown. SO2 decreased only during Phase 3 in a near-road environment. Satellite observations confirmed that NO2 decreased and CO stabilised during the total lockdown. Air pollutant changes during the lockdown could be overestimated between 2 and 10-fold without accounting for the influences of meteorology and long-term trends in pollutant concentrations. Air quality improved significantly during the lockdown driven by reduced NO2 and PM2.5 emissions despite increases in O3, resulting in health benefits for the MCMA population. A health assessment conducted suggested that around 588 deaths related to air pollution exposure were averted during the lockdown. Our results show that to reduce O3 within the MCMA, policies must focus on reducing VOCs emissions from non-mobile sources. The measures implemented during the COVID-19 lockdowns provide valuable information to reduce air pollution through a range of abatement strategies for emissions other than from motor vehicles.

COVID-19, the Built Environment, and Health

“…Within months of the initial outbreak of COVID-19, evidence emerged linking higher ambient levels of fine particulate matter and oxides of nitrogen with increased risk of COVID incidence, severity, and mortality. Within cities, neighborhoods near such sources as roadways and waste facilities-where residents are disproportionately poor and members of minority groups-were at particular risk, helping to explain part of the excess risk of COVID-19 seen in these populations (Ali and Islam 2020;Copat et al 2020;Hendryx and Luo 2020;Hernández-Paniagua et al 2021;Karan et al 2020;Kumari and Toshniwal 2020;Li et al 2020;Liang et al 2020;Naqvi et al 2021;Travaglio et al 2021;Woodby et al 2021;Wu et al 2020;Zhu et al 2020).…”

The Impact of COVID-19 Lockdowns on Air Quality—A Global Review

“…As per the results of the study, it was documented that there was a substantial improvement in air quality during lockdown periods. According to Hernández-Paniagua et al [154], the concentration of NO 2 was reduced by between 10% and 35% in Mexico during lockdown periods. Zalakeviciute et al [155] performed a study in Quito (Ecuador), and the findings of the study show that air quality improved by about 26% to 68%.…”

Air Quality during Covid-19 Lockdown

“…Moreover, Sharma et al (2020) [30] and Tobías et al (2020) [31] showed a rise of 17% and 57.7% in O 3 concentrations in India and Barcelona, respectively. Another study aimed at evaluating the Covid-19 lockdown impact on air pollutants levels in the Mexico City Metropolitan Area [32]. This study showed an increase of O 3 concentrations between 16% and 40% at the same sites where NO 2 decreased, and it suggested that in order to reduce the concentrations of O 3, the to be adopted policies should focus on the reduction of the emissions of VOCs from fixed sources.…”