Storm water and sewage runoff are the main reasons why there were 20,341 beach closing days reported in the United States in 2008, the fourth year in a row that the number has been higher than 20,000, says a Natural Resources Defense Council report released Wednesday.
Delaware, New Hampshire and Virginia had the best beach water quality while Louisiana, Ohio, Indiana and Illinois had the worst, USA Today reported.
"The waters along the Great Lakes coastline appear to the dirtiest, while the waters along the Southeast and DelMarVa (Delaware, New Hampshire and Virginia) coasts are relatively cleaner," the NRDC report said.
Rain is the main reason for polluted beaches because it carries pollutants from dirty storm water and overflowing sewage into streams and rivers, which eventually empty into oceans and lakes, Nancy Stoner, the council's water program co-director, told USA Today.
Many Great Lakes states had a wetter-than-normal summer in 2008, while Mid-Atlantic states were unusually dry, according to the National Climatic Data Center.