Severe air pollution in Indian capital Delhi has led to the formation of "black crusts" on the walls of the Red Fort, one of the city's most iconic Mughal-era monuments, a study has found.
Researchers found that the crusts - deposits formed due to chemical interactions between pollutants and the walls of the red sandstone fort - were between 0.05mm and 0.5mm thick, and could damage its intricate carvings if no action was taken.
The study is the first of its kind to comprehensively examine the effects of air pollution on the 17th Century monument.
One of the world's most polluted cities, Delhi frequently makes headlines for its worsening air quality, especially during the winter months.
Conservationists have frequently warned about the detrimental impact of pollution on heritage structures in the capital and a few other states.
