PCBs, a class of more than 200 chemicals used for almost 50 years, have been found in wildlife around the world, such as Icelandic killer whales, shorebirds along the Great Lakes and bottlenose dolphins along the East Coast and in the Mediterranean. Scientists have found they can make some animals more vulnerable to diseases including cancer and can disrupt growth, energy production and reproduction.

Four decades after PCBs were banned, These heat-resistant chemicals once used widely in electrical equipment and other industrial applications continue to pose a threat to wildlife and are still present in the environment and affecting wildlife. Researchers in New York found chickadees and song sparrows that ate contaminated insects sounded different from birds in uncontaminated areas, possibly because the chemicals interfere with the part of the brain responsible for song. At Superfund sites, researchers found high levels of PCBs in gulls and other seabirds, affecting their immune systems, fertility and survival of chicks. Sea lions (Zalophus californianus) in California have experienced elevated cancer rates. At New Hampshire’s Squam Lake, researchers wonder if PCBs are contributing to poor chick survival among common loons (Gavia immer).

“There is five decades of research showing that PCBs have had health impacts on both wildlife and humans,” Keith Grasman, a biology professor at Calvin University in Michigan, told the Associated Press. “While their concentrations in the environment have declined in many situations … we still see issues with these legacy compounds.”