Air pollution causing quick deterioration of Humayun's Tomb, says IIT report

A research project by IIT Kanpur and IIT Roorkee has revealed that long-term air pollution is speeding up the degradation of Humayun's Tomb. The team examined gypsum-based black crusts taken from various sandstone sections of the historic site. These crusts capture dust and metallic elements from traffic fumes and building work, which over time leads to the erosion of the sandstone.