Dose–response functions for the soiling of heritage materials due to air pollution exposure

A set of materials (Portland limestone, white painted steel, white plastic and polycarbonate filter material) was exposed at locations in London, Athens and Krakow. Regular measurements of reflectance were taken over a period of twelve months. Co-located measurements of PM 10 concentrations were available. Based on these results, the relationship between soiling (measured as loss of reflectance) and ambient PM 10 concentrations was quantified leading to the development of dose–response functions for the soiling of materials. The results for limestone revealed too much scatter for a prediction to be made. Implications for air quality management and for the conservation of cultural heritage buildings are considered, including public acceptability and economic factors.