Herons nesting in the wetlands of southeast Chicago are still being exposed to chemicals banned in the U.S. in the 1970s, a research team reports. The chemicals do not appear to be affecting the birds? reproductive success, however.

University of Illinois veterinary biosciences scientist Jeff Levengood led the study. Levengood, a wildlife toxicologist at the Illinois Natural History Survey, said that chemicals banned 30 years ago for their deleterious effects on wildlife are still showing up in the offspring of black-crowned night-herons in a Chicago wetland.

The researchers found PCBs and DDE in the eggs of night-herons nesting in the wetlands abutting Lake Calumet, in southeast Chicago. The Lake Calumet wetlands are surrounded by industrial developments along Lake Michigan near the Illinois-Indiana border.