The European Commission will take France, Germany, Hungary, Italy, Romania and Britain to the EU Court of Justice for failing to respect air quality limits, the EU executive said on Thursday.
The move follows a summit in January in which the Commission said it would get tough on member states that were still in breach of targets introduced for 2005 and 2010.
France, Germany and Britain will be taken to court over their failure to respect limits for nitrogen dioxide (NO2), while Hungary, Italy and Romania failed to meet required standards on the level of particulate matter.
"The Commission had to conclude that, in the case of six member states, the additional measures proposed are not sufficient to comply with air quality standards as soon as possible," EU Environment Commissioner Karmenu Vella told a news conference.
Spain, Slovakia and the Czech Republic avoided court by promising measures that would allow them to live up to EU air quality rules, Vella added.