By Minka Tiangco The city of Manila continues to enjoy cleaner air after residents retreated indoors amid the threat of the coronavirus disease-2019 (COVID-19) and the implementation of the enhanced community quarantine, an environmental group said. Asia Blue Skies Program, a partnership between the Manila city government, Clean Air Asia, and 3M, tracks air cleanliness in the city by measuring the amount of fine particulate matter or PM2.5. PM2.5 is atmospheric particulate matter that have a diameter of less than 2.5 micrometers. They come from power plants, motor vehicles, airplanes, burning of wood and plants, volcanic eruptions, and dust storms, among other sources. Data from Asia Blue Skies Program showed that the average PM2.5 levels at the Manila City Hall dropped by 42 percent from April 13 to 17, as compared to measurements during regular work days before the quarantine was implemented. However, other areas in the Philippine capital had slightly higher percentages of PM2.5 than before the enhanced community quarantine began. For the same period last week, the average PM2.5 levels was two percent higher at Rizal Park in Ermita and was nine percent higher at Mendiola corner Concepcion Aguila Street as compared to the days before the quarantine started. Earlier this month, a report by Clean Air Asia showed that air pollution has gone down by 74 percent at the Manila City Hall, 50 percent in Mendiola, and 61 percent at Rizal Park since the start of the enhanced community quarantine. Asia Blue Skies Program said the collected air quality monitoring data, emissions inventory, and health mapping results will be used as basis for the development of Manila City’s Clean Air Action Plan, which they are eyeing to finish by end of 2020.