If You Swim in the Hudson River, Don't Stir the Muck

Scientists have found up to 10 times as many pathogens in the Hudson River's near-shore soil than in its water, according to a new study by the Lamont-Doherty Earth Observatory at Columbia University.

Sewage discharge pipes spew fecal matter into the river estuary, which includes parts of Long Island Sound and New York harbor. Harmful micro-organisms that float in the water tend to disperse and dilute. But those that sink into the sediment have a chance to settle and thrive and, if they can feed off the river's organic muck, even reproduce.

"These fecal bacteria in the water, they typically last just a couple of days — but in the sediments, they can last for many months," said biologist and study author Andrew Juhl. He said that if those sediments are stirred up, the pathogens within can be released into the water.

Juhl and other scientists examined silt and sand at 11 spots in Rockland and Westchester counties, and in eastern Queens. Relatively high concentrations of germs were found in the murk at Piermont, NY, and at three sites around Flushing Bay in Queens. Sandy spots far from sewer pipes, such as Croton Point Beach in Westchester, had cleaner sediment. 

"While the findings make common sense," the authors wrote, "this is one of the first studies to test the idea in a river estuary, and is the first one in this region."

Most towns along the river disinfect their sewage with chlorine only in warm months, when people are likely to be swimming. The study's authors recommend they start doing it year round in order to prevent bacteria such as Enterococcus and Escherichia coli, which can cause severe respiratory infections and gastro-intestinal diseases, from building up in sediment.

Yet Juhl wanted to give perspective. "Don't panic," he said. "This is not a new danger. These bacteria were always there and, given that contamination levels in the water have been going down, presumably they're lower now in the sediments than they were 30 years ago."

That said, he admitted that after his daughter digs up rocks from the riverside near their Nyack home and skims them across the water, he makes her use hand sanitizer.