Abstract
Governments’ responses to the COVID-19 pandemic provide a unique opportunity to study the effects of restricted socioeconomic activity on air quality. Here, we study the changes in air pollution levels during the lockdown in Medellín and its metropolitan area, Colombia, for periods with and without enhanced regional fire activity, considering the effects of meteorology using random forest and multiple linear regression methods. The lockdown measures, which reduced mean traffic volume by 70% compared to 2016–2019, resulted in reductions for PM2.5 (50–63%), PM10 (59–64%), NO (75–76%), NO2 (43–47%), and CO (40–47%), while O3 concentration increased by 19–22%. In contrast, when fire activity was high, the effects of the lockdown on air quality were shadowed by the long-range transport of biomass burning emissions, increasing fine particulate matter and ozone. This study shows that healthier levels are achievable through significant efforts from decision-makers and society. The results highlight the need to develop integral measures that do not only consider reductions in the local emissions from transportation and industry, but also the role of fire activity in the region, as well as the difficulties of achieving reductions in ozone from measures that are effective at reducing primary pollutants.
Highlights
Ambient air pollution is a major environmental risk factor affecting health worldwide [1], estimated to be responsible for 8.8 million excess deaths per year globally, with about 200 thousand in South America [2]
Surface data come from the air quality and meteorological ground-level networks managed by the local Early Warning System in AMVA (SIATA for its Spanish acronym; https://siata.gov.co, accessed on 30 August 2021)
To disentangle the effects of the implemented lockdown restrictions from those related to fire activity during the lockdown, we defined periods of interest considering the legislative measures, the resulting traffic variations, regional fire activity, and concentrations of fine particulate matter during March and April 2020
Summary
Ambient air pollution is a major environmental risk factor affecting health worldwide [1], estimated to be responsible for 8.8 million excess deaths per year globally, with about 200 thousand in South America [2]. AMVA has experienced episodes of air pollution exceedances, especially of fine particulate matter, and the most severe episodes tend to occur in March [6]. These exceedance episodes are related to factors including AMVA’s complex topography (located in a narrow and steep valley), meteorological dynamics [6,7,8], fire activity in Northern South America [9,10], and a high population density.
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