PARIS/LISBON (Reuters) -The European Commission has decided to sue Portugal for its poor air quality caused by high levels of nitrogen dioxide, it said on Friday, pointing a finger at the southern European nation for failing to take appropriate measures to tackle the issue.

“Portugal has continually and persistently exceeded the annual nitrogen dioxide limit value in three air quality zones”, the Commission said in a statement, naming parts of Lisbon and Porto, the country’s biggest cities, as two of those areas.

In these zones, air pollution, which remains a huge environmental health hazard across the bloc, results mostly from road traffic, especially diesel vehicles, it explained.

Nitrogen dioxide, a noxious gas emitted by cars, power plants and factories, is blamed for some respiratory and heart conditions. It is responsible for 50,000 premature deaths in the EU every year, according to the European Environment Agency (EEA).

Almost every city-dwelling European is exposed to pollution that exceeds healthy levels, according to a 2019 report from the EEA. A satellite map by EU’s Copernicus showed high levels of nitrogen dioxide in Lisbon and Porto, as well as in other major cities in Europe over the past 14 days.

The Commission sent Portugal a notice on the issue in May 2019 and filed another warning in February 2020, giving the country two months to reply and adopt the necessary measures.

“Efforts by the Portuguese authorities have to date been unsatisfactory and insufficient,” it said. “Full implementation of the air quality standards enshrined in EU legislation is key to effectively protect human health and safeguard the natural environment.”

It is now referring Portugal to the European Court of Justice. The country’s environment ministry did not immediately reply to a Reuters request for comment.

Portugal is not a unique case. Earlier this year, the European Court of Justice ruled that Germany “systematically and persistently” exceeded the limit values ​​for nitrogen oxide in several cities, including in Berlin.

(Reporting by Marine Strauss and Benoit Van Overstraeten in Paris, Catarina Demony and Sérgio Gonçalves in Lisbon; Editing by Sabine Siebold and Jonathan Oatis)