Why the ancient monument Taj Mahal is losing its glory?

With regard to the discoloring of the monument Taj Mahal, a study was conducted by Sachchida Tripathi from IIT-Kanpur, Anu Ramaswami from University of Minnesota, Ajay Nagpure from the University of Minnesota and Raj Lal of Georgia Institute of Technology in the U.S.
Indo-American research team has found that burning of municipal solid waste in the vicinity of the iconic Taj Mahal is significantly contributing to the discoloring of the world heritage monument. Airborne particulate matter in cities poses a range of problems, including degradation in air quality leading to health concerns and also the discoloration of ancient buildings. To curb the impact of local air pollution on the world heritage site, researchers said the certain measures should be taken. This includes ┬árestricting vehicles near the complex, requiring iron foundries to install scrubbers and filters on their smokestacks, prohibiting new polluting enterprises from being built within a defined buffer zone around the mausoleum, and – most recently – banning the burning of cow dung cake as cooking fuel,