By Stephanie Ebbs

BRUSSELS (Reuters) - Desert sand, sea salt, volcanic ash and other forms of natural pollution are adding to rising levels of man-made dirt sullying the air and making it harder, especially for Mediterranean countries, to meet EU environmental regulations.

A report released this week from EU body the European Environment Agency (EEA) found the highest levels of natural pollutants were in Spain, which frequently experiences forest fires, most recently this month.

Out of 42 instances, where the levels in Spain were reported above legal limits, 18 were caused by natural pollution, said the report, which is the first European study of its kind.

The Observatory of Sustainability, an independent organization in Spain, said proximity to the Sahara made the Iberian peninsula especially vulnerable.

"This will get worse by desertification caused by climate change in the peninsula, converting this topic to a very important issue in Spain," the group said in a statement.

Ten other countries -- including Cyprus, Greece and Italy -- also reported air pollution above legal limits because of natural particles.

"This analysis shows that authorities should make extra efforts to reduce the air pollution they can control, because the cumulative effect of natural and man-made particulates can damage people's health," Jacqueline McGlade, EAA executive director, said in a statement.

While pollution from sea spray and sand result from natural phenomena, 90 percent of forest fires are caused by humans, as estimated by the EU research organization.

But if wind carries the smoke and particles from fires into other countries, they are classed as natural pollution. Continued...