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New York • The waterways surrounding New York City are a soup of plastic, ranging from discarded takeout containers down to tiny beads that end up in the food supply, according to a new report by an environmental group.

The study, by the group NY/NJ Baykeeper, estimated there are at least 165 million plastic particles floating in New York Harbor and nearby waters at any given time. The report was based on samples collected by trawlers that plied the city's East River, the mouth of the Hudson River and New Jersey's Passaic River and Raritan Bay between March and August 2015.

The average concentration of plastics was 256,322 particles per square kilometer, according to the report.

To maybe nobody's surprise, the highest concentration, 556,484 particles per square kilometer, was found in New York City's East River, which separates Manhattan from Brooklyn and Queens and is known for its floating filth.

"It just goes to show you big problems need big solutions," said Sandra Meola, a spokeswoman for Baykeeper.

The New York-New Jersey study was modeled on a pioneering study of the Great Lakes conducted by Sherri Mason, a chemistry professor at the State University of New York in Fredonia. That study found plastics pollution in all five lakes, with the highest concentration in Lakes Erie and Ontario, which are ringed by urban centers and industry.

In New York Harbor, as in the Great Lakes, tiny plastic microbeads used as a scrubbing agent in cosmetics accounted for tens of millions of the particles.

The Baykeeper study found that 85 percent of the plastic particles were smaller than 5 millimeters in diameter. Reacting to growing alarm over the tiny plastic particles, Congress passed the Microbead-Free Waters Act of 2015, which will force companies to stop using plastic beads in their products by July 2017.

Mason, who served as a consultant to the Baykeeper report, said tiny particles also include plastic shavings that are a byproduct of the manufacture of plastic bottles and other items. The shavings typically get washed down drains and end up in water systems, she said.

The proliferation of microplastics is troubling, Mason said, because fish mistake the plastic specks for food and ingest toxic chemicals that stick to the particles, as well as the particles themselves.