Residents in Bangkok, one of the world’s top tourist destinations, were warned on Thursday that the city’s air quality had hit dangerous levels just days after the country’s pollution control agency appealed to residents to wear face masks. The three major sources of air pollution in Bangkok are vehicular emissions in cities, biomass burning and transboundary haze in rural and border areas, and industrial discharges in concentrated industrialized zones. Previously, Greenpeace stated that people were not being informed properly about the situation since the Pollution Control Department (PCD) did not include PM2.5 in national Air Quality Index (AQI) measurements.