Delhi Deputy Chief Minister Manish Sisodia on Tuesday appealed to the Centre to play a "crucial role" in controlling pollution in north India and curb stubble burning. The national capital's air quality was in the "very poor" category in the morning, the first time this season, with calm winds and low temperatures allowing the accumulation of pollutants. "Stubble burning has started in neighboring states and smoke has started reaching Delhi. The Delhi government has taken several measures to reduce pollution throughout the year but why is that suddenly when stubble burning begins everybody is concerned about pollution and nothing is done throughout the year," Sisodia said. "We say it again and again that it is not just Delhi which is affected by pollution but the whole of north India," he said. By the time smoke from crop residue burning reaches Delhi, its "intensity is somewhat reduced but imagine how bad it will be affecting people living in Punjab and Haryana where stubble burning is actually taking place", the deputy chief minister said.