ROME, Aug. 6 (Xinhua) -- Italy's lakes are polluted by trash, microplastics, and untreated sewage, Legambiente environmentalist association said in what was its first national report on freshwater basins on Monday.

The report was based on findings by scientists aboard the environmentalist group's vessel Goletta dei Laghi (Italian for "schooner of the lakes"), which set sail in June to gather and analyze samples from 20 shore areas in Italy's great lakes, all of which are popular tourist and summer holiday destinations.

These include Italy's celebrated Lake Como at the foot of the Alps. The others are Lake Garda on the edge of the Dolomites mountain range, Lake Iseo in the northern Lombardy region, Lake Maggiore, lying between Italy and Switzerland, and Lake Trasimeno, which is located partly in Umbria and partly in Tuscany.

The scientists found an average of 2.5 items of trash in every square meter of beach, and 75.5 percent of them are plastic, Legambiente said.

Plastic breaks down into millions of microscopic particles (microplastics), which are impossible to remove completely and which enter the food chain, damaging the local biodiversity.

Cigarette butts made up the greatest number of single items of trash at 29.4 percent, followed by broken bottles and candy and potato chip wrappers, Legambiente said.

As well, the environmentalist group warned that 55 percent of water samples taken from 17 Italian lakes, including the great lakes, had excessive levels of bacteria from untreated sewage.

Legambiente also monitors Italy's celebrated sea coasts. Every summer for the past 30 years, the group's Goletta Verde (Green Schooner) vessel sails all around the Italian peninsula with volunteers and scientists on board, collecting water samples and testing them for bacteria and pollution.