Bacteria levels in the water at Nassau County beaches decreased slightly from 2011 to 2012, while levels at Suffolk County beaches stayed the same, according to a report released Wednesday.
The Natural Resources Defense Council study ranks New York 22nd out of 30 states for beach water quality in 2012, an improvement from 24th place in 2011.
Rankings were based on the number of times water samples exceeded state standards for bacteria levels. The NRDC reviewed state and EPA data from more than 3,000 beaches nationwide, officials said.
In New York, the percentage of water samples with bacteria levels exceeding the state limit was 9 percent for 2012, lower than 10 percent in 2011, according to the report. Nationwide, 7 percent of the water sampled exceeded limits.
Monitoring locations and the frequency are determined by local officials and can vary between jurisdictions, Levine said.
New York's slight improvement doesn't indicate any real change in water quality, NRDC officials said.
"The marginal differences of a percent from year to year are hard to interpret as meaning much," said Larry Levine, a senior attorney with the Manhattan-based environmental organization.
The difference may be in Tropical Storm Irene hitting in August 2011, during beach season when water quality measurements are taken. The storm caused a spike in bacteria at the time, Levine said. Superstorm Sandy slammed into Long Island in late October, well after beach season. Any increase in bacteria from Sandy wasn't measured, he said.
"Every year this report comes out and Nassau and Suffolk don't react," said Adrienne Esposito, executive director of Citizens Campaign for the Environment. "On Long Island, our beaches are one of the compelling reasons to live here and we would hope that government would be more aggressive stewards to protect those beaches."
Representatives of the Suffolk and Nassau county executives did not immediately respond to requests for comment.
The number of closing and advisory days at beaches in New York dropped to 1,626 days last year from 1,841 days in 2011, according to the report, which also attributed the change to Tropical Storm Irene and a fire that disabled a New York City sewage treatment plant for several days.
Nassau beaches had 350 closing or advisory days in 2012, while Suffolk had 578. In 2011, Nassau issued 307 and Suffolk issued 800.