Three generations of Sheldonian stone heads

Three generations of stone heads: (left to right) 1st generation head (1669) in Worcester College, Oxford (credit: Fusade); 2nd generation head (1869) in a private garden in Summertown, Oxford (credit: Fusade/Orr); 3rd generation head at the Sheldonian Theatre, Oxford (credit: Wilhelm).

Air pollution in Oxford remains one of the city's most pressing issues which harms humans and the built environment. Soiled and decaying buildings highlight the harmful effects to human and structural health where pollution particles such as soot and carcinogenic lead accumulate over time in layers of black crusts. These processes are irreversible, and thus, past pollution remains actively damaging. Our present understanding of Oxford's air quality in the past has come from scant archival evidence, from which significant periods are poorly understood. Yet, understanding past air pollution is a critical step to mediate present and future damaging effects.

Our current study builds on our pilot study, which started to improve our understanding of past air pollution. We used a unique set of three generations of stone sculptures, prominently stood in the heart of Oxford (the Heads in front of the Sheldonian Theatre and the History of Science Museum), having 'clocked' pollution for 350 years. They experienced three different periods of air pollution: the early Industrial Revolution, the Victorian period and the modern 20th century. When the first two generations of sculptures 'retired' to less polluted areas (e.g. private and college gardens; one can be visited at Wadham College), their 'pollution clocks' stopped. This enabled us for the very first time to 'tell the time' on these 'pollution clocks' and understand the links between changing air pollution sources (related to the evolution of transport and industrialisation) and their 'fingerprints' in the crusts. Our current study will use these 'fingerprints' to match them with samples of black crusts from New College Lane with a continuous 350-year history. This will allow us to develop a database of 'pollution fingerprints' which we want to use to map air pollution on a larger, regional and international scale in cooperation with partners from universities in Germany, Belgium, and the UK. Our results will help guide conservation interventions, developing healthy and sustainable cities, and generate pioneering new research.

The image shows three stone sculptures resembling bearded Roman sages which show various levels of stone decay and soiling

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