Kathmandu, Feb. 6 -- Kathmandu Valley witnessed hazardous levels of air pollution on 4-5 January 2021, with the Air Quality Index (AQI) highest among cities in the world that week. The pollution level had been stable or slightly below the daily average in the preceding days.

Air pollution over an area is determined by emissions and their transport. Sources of pollution can be both local and remote, whereas it can be carried into and out of the area depending on its geographical setting and atmospheric condition.

Understanding the role of geography and seasonal climatic variations in altering air pollution levels in Nepal has been generally well understood. The role of weather events in air pollution fluctuation is of key importance in p...