Despite the seemingly impregnable sense of serenity and other-worldliness which clings to the Taj, in reality, India’s most famous building faces serious threats from traffic and industrial pollution, and from the millions of tourists who visit it each year. Marble is all but impervious to the onslaught of wind and rain that erodes softer sandstone, but it has no natural defence against the sulphur dioxide that lingers in a dusty haze and shrouds the monument; sometimes the smog is so dense that the tomb cannot be seen from the fort. Sulphur dioxide mixes with atmospheric moisture and settles as sulphuric acid on the surface of the tomb, making the smooth white marble yellow and flaky, and forming a subtle fungus that experts have named “marble cancer”.

The main sources of pollution are the continuous flow of vehicles along the national highways that skirt the city, and the seventeen hundred factories in and around Agra – chemical effluents belched out from their chimneys are well beyond recommended safety limits. Despite laws demanding the installation of pollution-control devices, the imposition of a ban on all petrol- and diesel-fuelled traffic within 500m of the Taj Mahal, and an exclusion zone banning new industrial plants from an area of 10,400 square kilometres around the complex, pollutants in the atmosphere have continued to rise.

Cleaning work on the Taj Mahal rectifies the problem to some extent, but the chemicals used will themselves eventually affect the marble – attendants already shine their torches on “repaired” sections of marble to demonstrate how they’ve lost their translucency. The government has responded by setting up a pollution monitoring station to check on levels of N2O and SO2 in the atmosphere, but as far back as 2007, a parliamentary committee was reporting that, aside from the threat from these acidic gases, particulate matter in the air was slowly turning the Taj yellow; the report recommended treatment with a non-corrosive clay pack – something like a building-sized face-pack – to remove particle deposits from the marble, but so far no action has been taken.

From time to time scare reports surface to the effect that the Taj’s four minarets are listing and in danger of keeling over. Luckily, this proves to be a false alarm: the minarets were deliberately constructed leaning slightly outwards in order to counteract an optical illusion which would have made them appear to lean inwards when seen from ground level if they were actually exactly vertical. Despite their lean, they are quite stable.

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