Changes in air quality in Mexico City, London and Delhi in response to various stages and levels of lockdowns and easing of restrictions during COVID-19 pandemic

Abstract

The impacts of COVID-19 lockdown restrictions have provided a valuable global experiment into the extent of improvements in air quality possible with reductions in vehicle movements. Mexico City, London and Delhi all share the problem of air quality failing WHO guideline limits, each with unique situations and influencing factors. We determine, discuss and compare the air quality changes across these cities during the COVID-19, to understand how the findings may support future improvements in their air quality and associated health of citizens. We analysed ground-level PM 10 , PM 2.5 , NO 2 , O 3 and CO changes in each city for the period 1st January to August 31, 2020 under different phases of lockdown, with respect to daily average concentrations over the same period for 2017 to 2019. We found major reductions in PM 10 , PM 2.5 , NO 2 and CO across the three cities for the lockdown phases and increases in O 3 in London and Mexico City but not Delhi. The differences were due to the O 3 production criteria across the cities, for Delhi production depends on the VOC-limited photochemical regime. Levels of reductions were commensurate with the degree of lockdown. In Mexico City, the greatest reduction in measured concentration was in CO in the initial lockdown phase (40%), in London the greatest decrease was for NO 2 in the later part of the lockdown (49%), and in Delhi the greatest decrease was in PM 10 , and PM 2.5 in the initial lockdown phase (61% and 50%, respectively). Reduction in pollutant concentrations agreed with reductions in vehicle movements. In the initial lockdown phase vehicle movements reduced by up to 59% in Mexico City and 63% in London. The cities demonstrated a range of air quality changes in their differing geographical areas and land use types. Local meteorology and pollution events, such as forest fires, also impacted the results.

Persistently high incidence rates of childhood acute leukemias from 2010 to 2017 in Mexico City: A population study from the MIGICCL

“…MC not only exhibits among the highest AL incidence rates in the world, but it has also shown variable incidence trends over time, suggesting a potential role of non-genetic factors in disease development ( 44 ), such as an effect of the diversity of environmental exposure across municipalities ( 45 ). Several studies support this possibility, exhibiting differences in exposure among areas or municipalities—for example, to air pollution ( 46 – 49 ), metalsand chemicals of industrial, agriculture, commercial, and vehicular origin ( 50 , 51 ), and to different near-surface air temperatures. This last variable has become of great epidemiological interest ( 52 – 56 ) since it is related to the atmospheric distribution of pollutants, and shows great variability between municipalities and areas of MC ( 57 ).…”

Decade-low aerosol levels over the Bohai and Yellow Seas amid the COVID-19 lockdown

“…Similar studies have been reported in India ( Lokhandwala and Gautam, 2020 , Naqvi et al, 2021 ), Poland ( Filonchyk et al, 2020 ), Mexico ( Fu et al, 2020 ), Austria ( Lovrić et al, 2021 ), and Florida ( El-Sayed et al, 2021 ). For example, during the strict restrictions period in India, NO 2, PM 2.5 and AOD all decreased by varying degrees compared to the same period in previous years, especially in metropolitan areas such as New Delhi, Mumbai, Bangalore, and Kolkata ( Ranjan et al, 2020 , Singh et al, 2020 , Vega et al, 2021 , Yadav et al, 2020 ). All these above results are consistent with this study, which showed a notable decrease in AOD over the ocean during the lockdown.…”

Research on COVID-19 and air pollution: A path towards advancing exposure science

“…Thus, research on the impact of these societal changes on indoor and outdoor air pollution levels across or even within a geographic area may be difficult to interpret due to inconsistent definitions. The differences may contribute to varying results and conclusions of studies examining restriction-related associations with air pollution levels ( Briz- Redón et al, 2022 ; Liu et al, 2021 ; Sarmadi et al, 2021 ; Vega et al, 2021 ).…”