Delhi's air quality has deteriorated, slipping back into the 'very poor' category with the AQI reaching 332 on Friday and 355 on Saturday morning. Several monitoring stations recorded 'severe' pollution levels, with AQI above 400 in some areas. Thick smog and dense fog have reduced visibility, impacting travel and daily life. Experts attribute the worsening air to calm winds and cold weather trapping pollutants, with forecasts indicating the situation may persist. Vehicular emissions are identified as a major contributor.