The Institute of Fiscal Studies (Ministry of Finance and Public Administration) has awarded Ignasi Puig (Fundación ENT) the research project “The effectiveness of taxes on air pollution in Spain”. The project is conducting a comparative study of the autonomic taxes that exist in the State, trying to analyze the impact they may have had. Likewise, the possibilities of its reform are discussed based on the comparative law and the limits of the community regulations, the possible generalization of these taxes to other autonomous communities, as well as their possibilities of harmonization.