The European Commission, DG XI, has published a call for tenders for a study on cost-effective control of acidification and ground-level ozone in Europe. The EU is currently planning an acidification policy. It is also preparing a number of changes in air-pollution legislation such as a revision of the "Large combustion plants" Directive and the preparation of directives for: organic solvents, VOC emissions from filling-stations, non-road mobile sources, light-duty vehicles and the sulphur content of heavy fuel oil, bunker fuel, domestic fuel and kerosene. With a view to contributing to a cost-effective EU policy on acidification and ground-level ozone, this study should analyse the least-cost solutions for meeting a set of critical loads for acidification and critical levels for ground-level ozone in Europe. The assessment of the cost-effectiveness of effect-oriented and source-based strategies to control acidification and ground-level ozone can be subdivided into the following three areas: - Evaluation of source-based strategies and least-cost solution for acidification: Assessment of the annual costs and environmental impact (in relation to critical loads and levels) of a number of source-based scenarios for each country. In addition, the least-cost solution for meeting the critical loads for acidification (and nitrogen) in Europe should be determined, if feasible. Otherwise alternative target loads must be set. The least-cost solution is to be determined with and without source-based (policy) constraints. The purpose is to obtain initial insights into the cost and environmental impact of current policies, planned policies and other alternatives in order to guide EU policy decisions. - Least cost solution for meeting ozone critical levels: Assessment of the least-cost solution for meeting a set of (possible) critical levels for ozone across Europe, looking at both VOC and NOx emissions. The exercise should be carried out with and without constraints on national policies and source-based strategies. The purpose is to guide the EU in taking decisions on effect-based strategies towards ozone. - Least-cost solution for meeting ozone critical levels and critical loads for acidification: Assessment of the least-cost solution for meeting critical levels for ozone and critical loads for acidification simultaneously. Again the exercise has to be carried out with and without constraints. The exercise should lead to indications on the extent to which national emission reduction and source-based strategies are cost-effective from an acidification and ozone point of view. The countries to be analysed should be all EU countries as well as the 19 non-EU countries in Europe that are included in UN-ECE activities in this field. Where needed, countries might be subdivided into subregions. Transport matrices should be country-to-grid, where the relevant grid size is 150 by 150 km. The same grid size should be used for critical loads and levels and the estimation of effects. Requests for tender documentation should be sent to: European Commission DG XI - Environment, nuclear safety and civil protection Mr. B. Sinnott DG XI/A-2 200 rue de la Loi (TRMF/4-87) B-1049 Brussels Fax +32-2-2994449 Completed tenders should be sent to the same address.