COLUMBUS JUNCTION, Iowa — Factories discharged 3.3 million pounds of toxic chemicals into Iowa’s waterways in 2007, according to a report released Wednesday by an environmental group.

Tyson Fresh Meats of Columbus Junction released more than a third of the annual Iowa total — 1,338,270 pounds into the Iowa and Cedar rivers — said Eric Nost, state associate with Environment Iowa.

The Tyson plant at Perry discharged an additional 391,000 pounds into the Raccoon River, the report said.

The report compiles toxic chemical releases reported to the U.S. Environmental Protection Agency’s Toxics Release Inventory (TRI) for 2007, the most recent data available.

Toxic chemicals harm fish and wildlife and can affect human health, with the potential to trigger cancer, reproductive and developmental problems, according to the report.

Calling the inventory report “misleading without the proper context,” Tyson spokesman Gary Mickelson said the company’s Iowa plants are in compliance with state permits that regulate their wastewater treatment systems and that they release wastewater only after it has been treated in accordance with those permits. No laws have been broken and no penalties assessed, he said.

Industrial discharges “don’t have much impact at all on nitrates,” which constitute about 90 percent of the release inventory substances, said Mary Skopec, who supervises watershed monitoring and assessment for the Department of Natural Resources.

About 95 percent of the nitrates in Iowa waters come from agricultural

sources, she said.

Nationwide, factories released 232 million pounds of toxic chemicals in 2007. The Ohio River ranked first as a recipient of toxic discharges, followed by the New River in West Virginia and the Mississippi River. Other than the Mississippi, which was third, and the Missouri, eighth, none of Iowa’s rivers or lakes made the top 50 list.

Among states, Iowa ranked 21st in total volume of toxic discharges to waterways. Indiana led the nation with 27 million pounds. Nevada, with just 144 pounds, had the best record.

In Iowa, the leading waterways receiving toxic chemicals were:

 Iowa River, 805,000 pounds.

 Des Moines River, 621,000 pounds.

 Cedar River, 586,000 pounds.

Mississippi River, 553,000 pounds.

 Raccoon River, 391,000 pounds.

 Yellow River, 150,000 pounds.

Companies with eastern Iowa connections cited in the report, in addition to Tyson, include: 

Agriprocessors Inc. of Postville (now Agri Star Meat and Poultry) for discharging into the Yellow River

 Associated Milk Producers of Arlington for discharging into Bruce Creek

 The Lansing Power Station at Lansing for discharging into the Mississippi River

Cambrex Inc. of Charles City, PMX Industries of Cedar Rapids, Prairie Creek Generating Station of Cedar Rapids and John Deere Waterloo Tractor Works, all for discharging into the Cedar River

 Exide Technologies of Manchester for discharging into the Maquoketa River

 BP Products North America of Peosta for discharging into Catfish Creek.

Nitrates account for 90 percent of the volume of all TRI discharges, the report said.

To curb toxic pollution, Environment Iowa recommends that factories find safer alternatives to hazardous chemicals and that the EPA and state agencies issue and enforce permits with strict numeric limits for toxic pollutants.