European Environment Commissioner Janez Potocnik recommended that Belgium be referred to the EU Court of Justice for not meeting European limits on airborne particles.
The EU set exposure limits for pollutants that Belgium hasn't yet adopted.
"Belgium has applied for time extensions for meeting the targets but, in the commission's view, the conditions required have not been met," the EC said in a statement. "Despite an earlier reasoned opinion asking Belgium to act, air quality has not improved, so the commission has decided to take Belgium to the EU Court of Justice."
Belgium is also called on to make sure that waste water in small towns and villages is treated properly. EU law requires member states to make sure towns and settlements have adequate systems in place to treat waste water. Nearly 200 such places in Belgium don't have sufficient treatment facilities, the EC said.
Belgium faces further court action if it doesn't comply within two months.