Why Taj Mahal turning yellow?

One of the world's most famous buildings-visited by world leaders, royalty and Hollywood stars is turning a sludgy yellow-brown colour, prompting calls for urgent action. The Taj Mahal, India's biggest attraction, is being

badly affected by pollution which has caused the 400-year-old monument's white marble to become discoloured. It is turning yellow mainly due to these reasons: air pollution, discoloration of marble due to oxidation of its constituents, environmental neglect and wear and tear caused by millions of tourists who visit it every year.

So some discoloring is to be expected. Marble does not exist in a pure form, so the marble in the Taj Mahal is full of minerals which become oxidized over time. Oxidization leads to the browning of these minerals, resulting in brown splotches on the beautiful mausoleum. Rain also adversely affects the monument, slowly weathering it down, leading to chipping and cracking.

Another material, iron, was used by the Indian government for work on the Taj, which could be an explanation. Iron dovels were installed to repair the marble slabs on the building. The iron in these dovels naturally became rusted, and a new layer of this rust was then deposited onto the marble of the Taj.

Now Indian judges have told ministers more must be done to protect the iconic building from the smog coming from polluting industries nearby, which conservationists have long fought to close.India's Supreme Court demanded a detailed plan to protect the historic site, warning the state government's ad hoc approach was putting it in jeopardy.

Judges told the state government of Uttar Pradesh to produce a 'vision document' outlining its plan for protecting the wonder of the world, which must be published within a month.But years of interventions-including using mudpacks to draw the stain from the stone have failed to arrest the slow decay of the iconic building.

In particular the court expressed concern about a 'sudden flurry of activities' in the buffer zone around the monument which was intended to protect it from pollution.'Leather industries and hotels are coming up there.

Why?' the court asked.

The state government was also told to notify the court how many trees had been planted in the buffer zone before any further greenery was felled for construction works.The Taj Mahal was built by Mughal emperor Shah Jahan as a tomb for his beloved wife Mumtaz Mahal, who died in childbirth in 1631.

It has attracted world leaders and royalty, including Princess Diana, who was famously photographed alone on a marble seat there in 1992.The Duke and Duchess of Cambridge sat on the same bench at the end of a week-long royal tour of India in April 2016.

Hollywood couple Catherine Zeta-Jones, 48, and Michael Douglas, 73, also posed outside the famous monument with their children Dylan, 17, and Carys, 14, in December last year. In 2016 nearly 6.5 million people visited the monument, situated in the city of Agra on the banks of the Yamuna river in the northern state of Uttar Pradesh.

But last month the government announced plans to cap visitor numbers to reduce wear and tear.Anyone wanting to see the main crypt, which houses the couple's spectacular marble graves inlaid with semi-precious stones, will also have to pay for a more expensive ticket.

Building restoration has dragged into a fourth year, leaving scaffolding clinging to the exterior, with work yet to even begin on its imposing dome.