According to Wolfgang Krumbein, Professor of Geomicrobiology at the University of Oldenburg in Germany: 'Like dental caries, the uppermost layers are healthy but there is decay underneath. As a result the marble flakes off.' Parts of the Parthenon have already been badly affected, as has the Erechtheum. 'The structure is not immediately threatened, but the marble surfaces are in great danger,' Professor Krumbein said. He suggested that the sculptures on the frieze of the Parthenon should be taken down and, like the Elgin Marbles, removed to a museum 'for posterity'.
They could, he said, be preserved by immersion in ethylene dioxide, a gas which would sterilise the stones, killing all the microbes. Keeping them in a museum would isolate them from the effects of climatic changes.
The marble surface is being destroyed by several organisms - algae, bacteria and fungi. Environmental pollution increases the effects of micro-organisms: organic chemicals are absorbed on to the rock and serve as a source of nutrients for bacteria
But the main influence is climate change, Professor Krumbein believes. In the mid- 19th century, lichens stained the building red with oxalate crystals and with iron oxide. But wetter conditions led to fungi producing a black coating in the early 20th century. With the hotter, drier weather over the past 50 years the stone has been white.
Several options for treating the Acropolis are being explored. Surfaces can be treated with 'lime water', a suspension of calcium hydroxide that will plug the crevices and cracks and prevent most microbial growth. An alternative would be to wash the marble with a biocide, a combined antibiotic and fungicide. But the effect of these agents on the marble has yet to be established.