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Delhi's Red Fort Turns Black as Toxic Air Corrodes Historic Walls
6 Oct, 2025
Summary
- Black crusts forming on Red Fort walls due to air pollution
- Crusts contain pollutants like gypsum, quartz, and heavy metals
- Pollution chemically corroding the fort's red sandstone
In a concerning development, Delhi's iconic 17th-century Red Fort is facing a serious threat from the city's toxic air pollution. According to a study conducted by an Indo-Italian team of scientists from 2021 to 2023, the fort's iconic red sandstone walls are turning black due to the formation of 'black crusts' on the surface.
These black crusts are composed of pollutants such as gypsum, quartz, and heavy metals like lead, copper, and zinc, which are derived from traffic emissions, industrial pollution, and construction dust. The researchers found that these crusts are not only discoloring the fort but also chemically corroding the stone, weakening its structural integrity.
The study, published in June 2025 in the journal Heritage, warns that if no action is taken, other Delhi heritage sites like Humayun's Tomb could face similar damage. To conserve the Red Fort, the researchers suggest practical steps such as removing the thin black layers in the early stages, implementing a maintenance cleaning program, and applying stone protectives to prevent or slow down the crust formation.
The findings underscore the urgent need to address Delhi's air pollution crisis, which is now threatening the city's cultural heritage. As the nation's capital grapples with this environmental challenge, the preservation of its iconic landmarks like the Red Fort has become a pressing concern for authorities and conservationists alike.
