BRUSSELS, June 26 (Reuters) - The European Union's top court ruled on Wednesday that cities needed to act if pollution levels were exceeded in a single black spot rather than based on an average across a region, taking a hard line in a case brought by Brussels residents.
European governments are facing pressure to reduce the level of pollution in cities to address growing concerns about the long-term damage to public health of exposure to pollutants, particularly those from vehicle diesel engines.
A report released last year by the European Court of Auditors said that air pollution causes about 400,000 premature deaths each year in the EU and hundreds of billions of euros in health-related external costs.
EU law requires countries to assess the level, notably in urban areas, of a range of pollutants, including ozone and particulate matter, and take action if certain limits are hit.
The European Court of Justice (ECJ) was asked to rule in a case brought against Brussels by residents and campaign group ClientEarth over the region's air quality plan.
The ECJ judgment came a day after a ground-breaking ruling where a local court said France was responsible for air pollution in the Ile-de-France region around Paris, although it did not award damages to a mother and daughter who had suffered respiratory ailments.
The ECJ said that while authorities could choose where to conduct sampling, this needed to include the most polluted areas and concluded that the average measurement from different parts of the city did not show the exposure to pollutants.
To determine whether a limit had been reached in a calendar year it was sufficient if the pollution level was higher than the limit at a single sampling point, the ECJ said.
It also found that national courts were empowered to review the location of air quality stations and could order local authorities to make sure they are located appropriately.
"The ostrich-like approach, where some authorities try to hide the real extent of pollution rather than ensure their citizens breathe clean air, must stop," Jens Muller, air quality manager at Brussels-based campaign group Transport and Environment, said in a statement. (Reporting by Daphne Psaledakis; editing by Philip Blenkinsop and Alexander Smith)