Background The key European Union air quality directives include the Air Quality Directive (2008/50/EC), which merged the Air Quality Framework Directive (AQFD) and daughter directives, the Integrated Pollution Prevention and Control Directive (2008/1/EC) and the National Emission Ceilings Directive (2001/81/EC). Among other things, these directives aim to reduce air pollution associated with particulate matter, volatile organic compounds, nitrogen oxide and ozone. Depending on the extent of exposure to outdoor air pollution, the negative impact on human health can range from acute health effects and minor eye irritation, to severe chronic health issues including upper respiratory symptoms, chronic respiratory diseases, asthma, cardiovascular diseases and lung cancer. Some of these diseases require hospital treatment and can be fatal. At global level, air pollution is estimated to be responsible for approximately 800 000 premature deaths each year. It is estimated that asthma has 7-10% prevalence worldwide. Recent studies have demonstrated the existence of an explicit relationship between exposure to air pollutants and cases of childhood asthma – both the occurrence of the disease and exacerbation of childhood asthma. One proposed solution is photocatalytic technology, which can be used for air purification. Some attempts have been made to apply, at full scale, photocatalytic technology in urban agglomerations. However, it has been very difficult or even impossible to evaluate if the technique is really working. Objectives LIFE-PHOTOSCALING´s objective is to demonstrate the validity of photocatalytic technology in urban agglomerations by establishing instruments enabling scaling-up from laboratory measurements to application in cities, by developing a decision-support tool and by assessing the sustainability of different solutions in different environments to encourage the widespread use of this technology. LIFE-PHOTOSCALING intends to bridge the gap between research, policy and widespread implementation of the technology. Specific project activities will include: Development of two demonstration platforms at an intermediate pilot-plant technical scale; Technical development of a prototype for in-situ measurement of photocatalytic efficiency; Development of performance indicators for evaluation of process; Modelling of the photocatalytic processes; Development of a decision-support tool, enabling sustainability assessment using life-cycle assessment of the proposed solutions; and Validation of the tool in real conditions in the city of Madrid.The results will be submitted as draft proposals to the European Committee for Standarisation (CEN) (Technical Committee 386 “Photocatalysis”), and to other national standardisation groups. Expected results: 1. Two photocatalytic platforms made of the same representative materials in two different locations, for long-term evaluation, even beyond the end of the project; 2. Development of a technique enabling measurement of the efficiency of photocatalytic materials; 3. Detailed protocols explaining the procedure for measuring the operational performance of the photocatalytic materials, including effects of the contaminants, environmental conditions, efficiency and other parameters; 4. Indicators for the evaluation of the materials and the methodology to apply them to assess the performance of the products; and 5. A decision support tool to assess the sustainability of each particular solution in different conditions (such as type of street, dominant wind or traffic load).