Herons flourish despite banned chemicals

CHICAGO, Jan. 21 (UPI) -- Veterinary scientists have found herons are thriving in the Chicago area despite still being exposed to chemicals banned in the 1970s.

University of Illinois veterinary biosciences scientist Jeff Levengood led the study that found chemicals banned 30 years ago for their deleterious effects on wildlife are showing up in the offspring of black-crowned night-herons in a southeastern Chicago wetland.

The researchers found polychlorinated biphenyls, or PCBs, and dichlorodiphenyltrichloroethane, a metabolic by-product of DDT, in the eggs of night-herons nesting in the wetlands abutting Lake Calumet.

PCBs were used in electrical transformers until banned in 1977 because of their toxicity in the environment. DDE is a metabolic by-product of DDT, a pesticide banned in 1972.

While the team found no evidence of eggshell thinning, they said they saw an increase in some liver enzymes. "But that's not unexpected because the liver is trying to detoxify these compounds," said Levengood. The long-term consequences of the rise in liver enzymes are not known.

The research by the team that included scientists from the U.S. Geological Survey, the Illinois Waste Management and Research Center and Purdue and Duke universities appears in the Journal of Great Lakes Research.