Erosion research at iconic St Paul’s shows benefit of declining pollution levels

Erosion research at iconic St Paul's shows benefit of declining pollution levels. One of London's most iconic buildings, St Paul's Cathedral, is safer from pollution eroding its limestone façade than it has been since it was built 300 years ago, according to scientists - but it might turn green in the future. The team, including Cherith Moses , Senior Lecturer in physical geography at the University of Sussex, conducted the longest-ever study of erosion rates on a single building and found that sulphur dioxide levels - responsible for acid rain - have fallen by 95 per cent over 30 years. The drop is largely due to a decrease in industry and power generation in central London and the capital increasingly moving to cleaner energy. Acid rain is now responsible for a fraction of one per cent of the damage to St Paul's and the rate of erosion at the cathedral is now dominated by natural rainfall, which is a weak carbonic acid with a pH of about 5. The researchers conclude that the building is now safer than it has ever been, having survived the ravages of the Industrial Revolution, the nearby Bankside Power Station's plumes of sulphuric dioxide gas and smoke, and Londoners' love of coal fires. Scientists from Sussex, Portsmouth, Oxford and Cambridge monitored the rate of erosion on the balustrade between 1980 and 2010 using a Micro Erosion Meter to take periodic readings of pollutants in the natural stone.