Water at Long Island beaches had increased bacteria counts in 2011 and the state as a whole dropped five spots in a nationwide ranking of beach-water cleanliness, a new report concluded Wednesday.
Stormwater runoff and sewage spills dirtied water at coastal and Great Lakes beaches in New York, which ranked 24 out of 30 states in the "Testing the Waters" report issued by the environmental advocacy group Natural Resources Defense Council.
The report and local monitoring agencies blamed Tropical Storm Irene and a 200-million-gallon sewage spill in the Hudson River for the increased number of days beaches were closed or bathing advisories were issued.
States and contracted agencies measure for enterococcus in salt water and E. coli in fresh water, which are indicators of pathogens that can cause illnesses like stomach flu, skin rashes, pinkeye and dysentery.
Locally, West Beach at Heckscher State Park in East Islip had the worst record, with 29 percent of samples showing bacteria above state limits.
"When people dive into the ocean, it can make them sick with a range of health problems," said Steve Fleischli, director of the council's water program.
The rankings are based on the number of times samples exceeded state standards. The comparison is not uniform, however, as states use different standards.
Nationwide, 8 percent of beach-water samples violated public-health standards in 2011. In New York, 10 percent exceeded standards in 2011, up from 9 percent a year earlier.
The culprits: polluted runoff from roads, parking lots and buildings, pet waste, oils and grease from cars and fertilizers or pesticides from yards.
"All of these pollutants are washed off when it rains and dumped without treatment into coastal waterways," said Larry Levine, a senior attorney in the group's water program.
In 2011, New York beaches had 1,841 closings or advisory warnings, a 93 percent increase from a dry 2010 and a 3.7 percent increase from 2009.
Nassau ranked ninth out of 15 New York counties with 8 percent; Suffolk tied with Staten Island and Brooklyn at 7 percent. In 2010, Nassau ranked eighth with 7 percent and Suffolk 11th with 5 percent.
Last year, Suffolk issued 800 closings or advisory warnings and Nassau issued 307.
Beekman Beach in Oyster Bay, Nassau County, came in second at 26 percent, although swimming is not permitted at the beach, said Mary Ellen Laurain, spokeswoman for the Nassau County Department of Health.