The Commission has launched an infringement procedure against Estonia, Cyprus, Germany, Italy, Poland, Portugal, Slovenia, Spain, Sweden and the United Kingdom that reportedly do not meet the bloc's air quality standards concerning coarse particles known as PM10.
EU countries were sent a request for information in June 2008 and the Commission subsequently gave a first warning to 10 member states that had failed to bring the PM10 concentration down to the required level.
Depending on a particular country's response to the warning, the Commission may decide to send it a so-called reasoned opinion explaining why it finds the country in violation of EU legislation and urging it to ensure observance of law by a set deadline which usually is two months.
If a member state fails to comply, the EU executive may refer the case to the European Court of Justice.
PM10 particles emitted by industrial enterprises, motor vehicles and household boiler houses can cause asthma, cardiovascular disease, lung cancer and premature death.
The new air quality directive that stepped into effect in June 2008 allows EU member states to apply on certain conditions for a period of grace to bring the PM10 concentration into line with the norm.