International Cooperative Programme on Effects of Air Pollution on Materials, including Historic and Cultural Monuments
Co-Chairs: Mr. J. Tidblad (Sweden) and Mr. P. Spezzano (Italy)
Head of Programme Centre: Mr. J. Tidblad
Several studies of materials have indicated that atmospheric corrosion influenced by acidifying pollutants is costly. Extensive damage has also been observed on historical and cultural structures and monuments calcareous stones, medieval glass and metals. For these reasons, the Materials Programme was launched in 1985 to fill some of the major gaps in our knowledge.
ICP Materials has two objectives:
- to perform a quantitative evaluation of the effect of sulphur and nitrogen compounds and other major pollutants, including the effects of low concentrations of these pollutants on the atmospheric corrosion of important materials, and
- to assess the trends of corrosion and pollution.
The quantitative evaluation aims at determining dose-response relationships as a basis for assessing acceptable and/or target levels and calculating costs due to material damage. Structural metals, stone materials, paint coatings, electric contact materials, samples of medieval stained-glass windows and polymer materials are included. The aim of the trend exposures is to serve as a confirmation of the environmental effects of previous pollutant reductions achieved under the Convention, as well as a method for identifying extraordinary environmental changes that result in materials damage
The Task Force of the programme is led by Sweden, which provides the Main Research Centre at the Corrosion and Metals Research Institute (KIMAB), Stockholm. Since 2005 Sweden and Italy (ENEA) are co-chairing the programme. The Czech Republic, Germany, the United Kingdom, Norway, Austria and Switzerland are responsible for sub-centres, which prepare and distribute specimens of particular materials and evaluate corrosion attack after exposure. In all countries, national contact persons are responsible for the exposure and withdrawal of specimens and for reporting environmental parameters to the environmental sub-centre in Norway. A network of 30 exposure sites across 18 ECE countries covers a broad band of geographic zones in Europe and North America. At these, atmospheric pollution is characterized by measuring the gases sulphur dioxide (SO2) and nitrogen dioxide (NO2) and ozone (O3) concentrations. During some periods also the nitric acid (HNO3) concentration and deposition of particulate matter (PM) are included. Wet deposition of pollutants is characterized by analysis of rainwater. The first exposure programme included evaluation of specimens after 1, 2 and 4 and 8 years (1987-1995). Statistical analysis has provided dose-response relations for several materials linking deterioration with environmental parameters.
The reduction of the sulphur pollution has created a new multipollutant situation where SO2 is no longer the dominating corrosive pollutant. Therefore, a second "multipollutant programme" was performed in 1997-2001 using a subset of test sites and materials from the original programme, along with some new test sites. A new set of dose-response functions was developed describing the deterioration of material in the new mixture of pollutants.
Both long-range transport and local emissions of pollutants are important for materials exposed to the atmosphere. In addition, the concept of a threshold of harmful pollution, a critical load or level, is not applicable to materials. Any amount of pollution leads to some deterioration. Instead an "acceptable" deterioration rate has been defined as a multiple (e.g. 1.5) of the background deterioration rate. Acceptable levels of pollution can be calculated using dose-response relations for the individual materials and the acceptable deterioration rate. This concept is now used for mapping of areas with exceedances and together with assessments of the stock of materials, especially cultural heritage objects, at risk for cost-benefit analyses in different pollution scenarios.
Further information is available from the Programme Centre.