Taj Mahal is being slowly disfigured and discoloured. This is primarily due to: water pollution, global warming, soil pollution, acid rain.

The primary cause of the Taj Mahal's discoloration and disfigurement is acid rain. Acid rain, formed by the reaction of pollutants like sulfur dioxide and nitrogen oxides with atmospheric water, causes chemical weathering of the marble. This leads to the discoloration and deterioration of the monument's surface.