The event on May 11 cleaned up and restored land at 62 volunteer sites along the Chicago River.

Friends of the Chicago River has organized the event every year for 27 years. This year, trash at seven locations was brought to a Waste Management facility, where it will be studied. Friends of the Chicago River wants to know where the trash comes from and how it moves along the river. The Litter Free Chicago River project is supported by a $70,000 grant from Mars Wrigley Foundation.

“After years of effort, there is less litter in the Chicago River system, but it still poses a problem,” said Margaret Frisbie, executive director of Friends of the Chicago River.

The litter, says Frisbie, blows into the Chicago River from the shore or is illegally tossed into the river. Sometimes it washes in from an overflowing sewer.

What’s in the trash? Volunteers have seen it all. “Shopping carts, boxing glove, coconut, plastic bottles and their caps – tons of caps – lots of cigarette butts, plastic shopping bags, clothes, chip bags, fishing line and...huge heavy fishing gear, hub caps, a restaurant sign, car parts, lots of glass, and sharp used needles [which] volunteer site captains are trained to handle,” says Frisbie.

The trash is often ingested by the fish. An examination of 350 fish from the Chicago River revealed bits of plastic in 90 percent of them, according to Dr. Timothy Hoellein, a biologist for Loyola University.

“In some cases, plastics may pass through the digestive system without interaction,” says Hoellein (right). “In other cases, we’ve seen that plastics disrupt and injure the digestive systems of fish. There are also chemicals that stick to plastics or are part of the plastic itself that can leach out and be absorbed into tissues.”

Sometimes, says Hoellein, plastic ingested by a larger fish makes it feel so “full” it does not continue consuming nutrients.