A black crust is decaying Humayun's Tomb in Delhi. How the air is to blame, and what can be done

A concerning black crust is steadily decaying Delhi's iconic Humayun's Tomb, a UNESCO World Heritage site. Researchers have identified air pollution as the principal culprit behind this deterioration. The monument, a masterpiece of Mughal architecture, is suffering from the cumulative effects of environmental pollutants that are slowly eating away at its historic sandstone. The problem is not unique to Humayun's Tomb; many of Delhi's historical structures face similar threats from the city's notoriously poor air quality. To combat this decay, scientists and conservationists are recommending a multi-pronged approach. This includes implementing a schedule of regular maintenance to clean and inspect the monument, applying protective coatings that can shield the stone from pollutants, and establishing a continuous monitoring system to track any further degradation. These measures are deemed essential to preserve the integrity and beauty of this significant historical landmark for future generations.

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For Delhi's monuments, researchers recommend regular maintenance, protective coatings and then monitoring.