Erosion study breathes new life into St Paul's

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Erosion of St Paul's Cathedral in London has halved in the last ten years, a team of academics has found. They include Sussex geographer Dr Cherith Moses, a member of the Centre for Environmental Research in CPES.

Cherith joins scientists from five other universities and the Building Research Establishment, who have been monitoring erosion rates on the historic building for the past 20 years, in the longest-running programme of its kind in the world to monitor the decay of building stone.

The study, originally designed to provide reliable averages for long-term studies, now shows that the cathedral's life expectancy has doubled, following a reduction in pollution levels.

Parallel decreases in air pollution - notably in levels of sulphur dioxide - offer a causal explanation and the team continues to test results. One key finding is that even though erosion rates at St Paul's have halved, they are still ten times higher than rates reported for non-urban, non-industrial areas.

The results have significant implications for environmental policy. The encouraging findings that decreased pollution slows down the deterioration of building stone are tempered with the knowledge that rates of urban stone decay still outstrip those of non-urban areas.

The results are also of significance to those involved in the preservation of built heritage. The problem is universal, as scientists strive to understand the processes behind the erosion of the Sphinx and pyramids in Egypt, the water-bound buildings in Venice, temples in Asia and other monuments.

Even if scientists can determine how fast a building is eroding and why, they are left with the problem of how to protect it. Many protective resins have been found to cause more damage than they aim to prevent. "The only way to protect our buildings and health is to keep atmospheric pollution to a minimum," suggests Cherith.