Severe air pollution in India’s capital, Delhi, is now leaving a visible scar on one of its most treasured monuments — the Red Fort.
A recent study, published in the open-access scientific journal Heritage, has revealed the formation of “black crusts” on the fort’s red sandstone walls. Conducted between 2021 and 2023 by researchers from India and Italy, the study examined air quality data and samples scraped from the monument.
The findings show that particulate matter — PM2.5 and PM10 — along with other pollutants, are chemically reacting with the fort’s stone surface, creating dark deposits ranging from 0.05mm to 0.5mm in thickness. Over time, these crusts are not only discoloring the walls but also damaging intricate carvings, vaults, arches, and other architectural elements.
Conservation experts fear this could mirror the fate of the Taj Mahal, which has turned yellow and greenish-brown due to pollution. In fact, the Supreme Court had earlier urged urgent steps to protect the Taj.
The Red Fort, built by Mughal emperor Shah Jahan in the 17th century, holds immense historical significance. From being the site where India’s first Prime Minister Jawaharlal Nehru hoisted the national flag in 1947 to serving as the backdrop for Independence Day speeches, it is both a heritage icon and a living symbol of India’s history.
The study warns that the formation of black crusts is a progressive phenomenon — initially removable, but harder to treat as they deepen. Researchers recommend preventive conservation strategies, including the application of protective stone sealants in highly affected areas, along with urgent steps to reduce pollution.
As Delhi continues to rank among the world’s most polluted cities, this latest evidence underscores not just an environmental crisis, but also a looming cultural tragedy. Without immediate intervention, the city risks losing the vibrant red glow of its Red Fort — a UNESCO World Heritage Site and one of the nation’s greatest treasures.
