U.S. dirtiest and cleanest beaches named

The upcoming Fourth of July weekend means many Americans will be hitting their local beaches.

But a new report by the environmental action group, the Natural Resources Defense Council (NRDC) - which ranks the nation's beaches by cleanliness each year - shows that 2010 saw the second-highest number of beach closings on record - and the economic impact is devastating to communities who rely on tourism as their main source of income.

A factor in those closures, CBS News Business and Economics Correspondent Rebecca Jarvis noted on "The Early Show," has been the BP oil spill.

"One hundred and seventy million gallons of oil flowed into the Gulf as a result of the BP oil spill," Jarvis said on "The Early Show." "It affected 1,000 plus miles of shoreline, and in particular, it really hit Louisiana, Alabama, Mississippi and Florida -- those were the worst impacted but Louisiana was number one."

Louisiana alone, Jarvis said, estimates losses could exceed $295 million by 2013, according to the state's Department of Tourism.

"That is a huge number," Jarvis remarked. "Alabama has seen its beach traffic go down 41 percent. Mississippi has seen traffic go down, and in particular Mississippi, for example, they rely on revenue from the gambling industry, and they've lost more than $100 million, they expect from all of this."

In addition to the effects of oil, contamination from other forms of pollution also helped put certain beaches on the NRDC's list.

Jarvis explained, "(They're the types of things) that we see every single day in the country, the runoff from rain water, in addition to that, human and animal waste, and these are things, it sounds nasty, it can translate to significant diseases, things like respiratory problems, flu-like symptoms, and it's worse when you're a senior citizen or a child and you have an immune system that is in a worse position."

Check out the NRDC's "Top 10 Repeat Offender" beaches:

According to the NRDC, "Over the last five years of this report, sections of 10 U.S. beaches have stood out as having persistent contamination problems, with water samples exceeding health standards more than 25 percent of the time for each year from 2006 to 2010:

California: Avalon Beach in Los Angeles County (3 of 5 monitored sections):
Avalon Beach - Near Busy B Cafe
Avalon Beach - North of GP Pier
Avalon Beach - South of GP Pier

California: Cabrillo Beach in Los Angeles County

California: Doheny State Beach in Orange County (2 of 6 monitored sections):
Doheny State Beach - North of San Juan Creek
Doheny State Beach - Surfzone at Outfall

Florida: Keaton Beach in Taylor County

Illinois: North Point Marina North Beach in Lake County

New Jersey: Beachwood Beach West in Ocean County

Ohio: Villa Angela State Park in Cuyahoga County

Texas: Ropes Park in Nueces County

Wisconsin: Eichelman beach in Kenosha County

Wisconsin: South Shore Beach in Milwaukee

The NRDC also named these so-called "Superstar Beaches," ranked highly for water quality, testing and public notifications:

Delaware: Rehoboth Beach-Rehoboth Avenue Beach, in Sussex County
Delaware: Dewey Beach, in Sussex County
Minnesota: Park Point Lafayette Community Club Beach, in St. Louis County
New Hampshire: Hampton Beach State Park in Rockingham County