People participate in the Clean Beach campaign in Tallinn, Estonia, on May 4, 2019. A citywide beach action day Clean Beach was held on Saturday in the Estonian capital as part of the program of the Urban Maintenance Month from April 14 to May 15 to raise environmental awareness of citizens. (Xinhua/Guo Chunju)

A woman participates in the Clean Beach campaign in Tallinn, Estonia, on May 4, 2019. A citywide beach action day Clean Beach was held on Saturday in the Estonian capital as part of the program of the Urban Maintenance Month from April 14 to May 15 to raise environmental awareness of citizens. (Xinhua/Guo Chunju)

People participate in the Clean Beach campaign in Tallinn, Estonia, on May 4, 2019. A citywide beach action day Clean Beach was held on Saturday in the Estonian capital as part of the program of the Urban Maintenance Month from April 14 to May 15 to raise environmental awareness of citizens. (Xinhua/Guo Chunju)

People participate in the Clean Beach campaign in Tallinn, Estonia, on May 4, 2019. A citywide beach action day Clean Beach was held on Saturday in the Estonian capital as part of the program of the Urban Maintenance Month from April 14 to May 15 to raise environmental awareness of citizens. (Xinhua/Guo Chunju)

A boy participates in the Clean Beach campaign in Tallinn, Estonia, on May 4, 2019. A citywide beach action day Clean Beach was held on Saturday in the Estonian capital as part of the program of the Urban Maintenance Month from April 14 to May 15 to raise environmental awareness of citizens. (Xinhua/Guo Chunju)

People participate in the Clean Beach campaign in Tallinn, Estonia, on May 4, 2019. A citywide beach action day Clean Beach was held on Saturday in the Estonian capital as part of the program of the Urban Maintenance Month from April 14 to May 15 to raise environmental awareness of citizens. (Xinhua/Guo Chunju)