PCBs have polluted rivers and the Great Lakes of the US mid-west. Studies conducted on the Mississippi, the Ohio rivers, and the Fox have found PCBs associated with the sediments and the organic content in the water. PCBs were most concentrated in fish in the Mississippi near Pepin (Wisconsin) and in the Ohio. According to the US Fish and Wildlife Service, PCB concentrations in fish in the Mississippi remained relatively constant from 1976 to 1981, but have grown since then.

A 1995 US Geological Survey report says that while the tributaries of the Ohio river have lesser PCB concentrations in their silt than the main river, studies in Iowa show that the most severe cases of fish contamination occur near large urban areas. This has increased the likelihood of PCBs passing on into humans through fish consumption. A study of areas along the Lower Fox river, housing some six per cent of Wisconsin's population, found that it was highly contaminated with PCBs. Sediments between the mouth of the Fox and DePere dam upstream store some 29,275 kg of the chemical. According to the study, increase in concentration of PCB in river water was linked to the growth and movement of algae and phytoplankton. The study predicted that over the course of 25 years, 1,300 kg of PCB would be transported over the DePere dam and 200 kg emitted into the atmosphere.