Pollutants from various sources have been superficially depositing on the marble surface of Taj Mahal as particulate matter and due to scattering of light by these particles, the marble surface of Taj Mahal appears to have changed in colour.
This was stated by the government, quoting the Archaeological Survey of India (ASI), in response to questions in the Lok Sabha as to whether the marble of the Taj Mahal is getting dis-coloured due to air pollution.
Minister of State in the Ministry of Environment Mahesh Sharma, while replying to questions on Friday, said the ASI has formulated scientific cleaning and conservation plan to protect the surface of Taj Mahal from deposited pollutants.
"Accordingly, all four minarets, eight facades, four pedestal marble walls, interior portion of periphery up to human height and four chhatries at roof top of main mausoleum, have already been cleaned and treated," he said.
"However, the cleaning of main dome requires some technical studies," he added.
Asked whether the foundation of Taj Mahal was becoming weak due to polluted water of River Yamuna, Mr Sharma, citing the ASI, said the water level of the river was away from the northern wall of the monument.
"Therefore, specific study on the link between Yamuna water and strength of the foundation of Taj Mahal has not been conducted," the minister added.
The Supreme Court had in May expressed concern over the change of colour of the Mughal-era monument and asked the government what it was doing about it.
The world-famous monument was built by Shah Jahan in memory of his late wife.