The air quality in the national capital remained 'poor' on Tuesday, largely due to wind direction that changed to northwesterly on Sunday, increasing the contribution of smoke from stubble burning in neighbouring states to pollution in the city.
Westerly and northwesterly winds bring dust from western regions and smoke caused by burning of crop residue in the neighbouring Punjab and Haryana to Delhi-NCR.
After fluctuating between "poor" and "very poor" for over a week, the city's air quality had improved to "moderate" category on Saturday, mainly due to a squall in Delhi that dispersed pollutants and rainfall in neighbouring areas