European emissions of acid rain-causing sulphur dioxide have declined by 65 percent since 1990, contributing to a decline in air pollution across Europe, a United Nations agency said on Friday.

The U.N. Economic Commission for Europe (UNECE) said the drop in sulphur dioxide emissions to less than 15 million tonnes meant Europe had already reached its 2010 target on cutting the amount of the colorless gas released from coal-burning power plants and heavy industry.

"Europe's air is getting cleaner," the Geneva-based agency said in a statement.

Some individual European countries have surpassed their targets, and about half still needed to reduce emissions to comply with a 1999 Gothenburg Protocol agreement.

"When this is done, the widespread 'acid rain' effects caused by sulfur will be limited to very sensitive soils and areas where damage has been severe," the agency said.

Emissions of nitrogen oxides have fallen a more meager 30 percent since 1990, the agency said, meaning another 15 percent decrease was required to meet European targets on the gases released from cars and power plants.

Emissions of volatile organic compounds, which combined with nitrogen oxides contribute to ground-level ozone production, have fallen by 38 percent in the period, making high ozone episodes less frequent, it said.