Pollution impact on monuments slow but long lasting: Experts

Among the most evident symptoms of an affected monument, particularly those built in white marble or limestone is the gradual yellowing of the walls, similar to what has been happening to the Taj Mahal in Agra. 

Pollutants like sulphur dioxide and nitrogen dioxide, generated by vehicles and industries, react with air moisture to form acids that eat into the marble resulting in change of colour and even corrosion.

The latest casualty in Delhi is the Lotus Temple, which in the present day, stands amidst alarming traffic chaos and is subjected to vehicular emissions which may have been contributing towards the greying of the monument. 

The structure is made of porous Pentelikon marbles that was used to construct monuments in Greece. 

Activist Sohail Hashmi says that to realise the damage on an elementary level, all one has to do is to rub a wet handkerchief on the wall of the monument.

“A black, grimy muck comes off. But, it is not just dust. It is the unburnt fuel from vehicles and the sulphur fumes from the industry. These get into the cracks. The acid rain seeps in and damages the monuments,” says Hashmi.