2  Methodology
In the year 2019 a study was presented on Meteosim online platform where they made an analysis on the most polluting capitals in the world (Meteosim, 2019). This research indicates that one of the most dangerous pollutants is fine particulate matter with diameters ≤2.5 μm (PM2.5), so the analysis of the fifty most contaminated capitals was carried out. Based on the above information and according to the automotive and industrial paralysis in the world by COVID-19, for this research they were collected the PM2.5 data from an online platform (WAQ Index, 2020). This tool, called World Air Quality Index (WAQI) is used for obtained the information historical of Air Quality Data in especial for this paper of PM2.5 particulate matter of each capital before quarantine and during quarantine. For each capital city, the information was corroborated with the territorial entity of data administration at the public level. For example, Bogotá, Colombia was verified on the IBOCA platform of the Secretary of the Environment (Environment, 2019). For Delhi, India was verified on the Real Time Ambient Air Quality Data Platform of the Department of Environment (Department of Environment, 2020). For Berlin, Germany was verify with the Umwelt Bundesamt platform of the German Environment Agency (2020). And so on for each city.
In this context, the research process in the paper has been divided into five main steps. 1. Identification of the 50 most polluted capital cities. 2. Review of the quarantine information. 3. Data collection of population and the weather stations. 4. PM2.5 Data extraction. 5. Graphics and analysis.