Prague - Acid rain is damaging India's famed Taj Mahal but is becoming less of a threat to Europe's cultural monuments, scientists reported on Thursday at an international conference in Prague.

"The milky white marble of the Taj Mahal is turning pale," said SK Sharma of India's Geological Research Institute at the International Conference on Acid Deposition.

"This one-time marvel is now being subjected to all types of industrial and garbage pollution," he said.

However, while India's 17th century landmark is under attack, Europe's historic structures are faring better thanks to air pollution controls enacted over the past 50 years.

A steady reduction in sulphate emissions from coal burning and other sources was credited with cutting the acid rain-related corrosion of building materials such as stone in statues, castles, churches and concert halls.

In one study, a team of Czech, Swedish and Norwegian researchers found that rain-related "corrosion losses" to metals in 20 European cities have declined up to 60 percent since 1987.

The researchers said European emissions of two sources of acid rain corrosion namely sulphur dioxide and nitrous oxides have in recent decades declined 70 percent and 30 percent, respectively.

Europe's buildings still face pollution threats from diesel soot and nitrogen deposits, said environmental scientist Peter Brimblecombe of Britain's University of East Anglia. For example, more lichens grow on stone in nitrogen-rich rain.

Yet pollution expert Mike Holland of Britain's Ecometrics Research and Consulting said a "major fall" in emissions since the 1950s has curtailed the "widespread" damage to cultural heritage sites.

Indeed, Sharma's report on the Taj Mahal was the darkest description of a threatened monument presented at the conference.

He blamed the landmark's decay to acid rain linked to emissions from a petroleum refinery in the nearby city Mathura, and foundries in the monument's hometown Agra.

The building's minarets are corroding "year after year due to frequent acid rains, caused by the presence of gaseous effluents discharged into the atmosphere by these industrial units," Sharma said.

"Only corrective measures to make the nearby environment eco-friendly and shifting hazardous industries (away) can help in restoring the lost glory of the Taj Mahal." - Sapa-dpa