NEW DELHI (Reuters) -Residents in India's northern states woke up to another day of poor air quality on Tuesday, as a layer of dense fog shrouded most of the region and pollution in the capital Delhi remained severe.

Despite the recurrence of extreme pollution episodes and their very high health costs, the authorities are not taking any structural measures.

India's capital city of Delhi has virtually shut down as air pollution hit "severe plus" levels, according to Indian government officials in its pollution control authority.