May Cassar is Professor of Sustainable Heritage at University College London and Director of the UK Science and Heritage Research Programme; she is also a Fellow of the International Institute for Conservation of Historic and Artistic Works. Peter Brimblecombe is Professor of Atmospheric Chemistry at the University of East Anglia, an Associate Dean and a Senior Editor of the journal 'Atmospheric Environment'. Cristina Sabbioni is Research Director at the Institute of Atmospheric Sciences and Climate within the Italian National Research Council.