The bottlenose dolphins of Georgia, USA have been found to have record levels of chemical contamination years after a chemical plant in the area was closed.

People have known about pollution in the area since the mid-1990s, when the Brunswick chemical plant went bankrupt and closed. The U.S. Environmental Protection Agency took charge of planning a clean-up at what was one of the worst sites for pollution in the American Southeast.

While most immediate hazards were cleaned years ago, the agency is still deciding what sort of long-term work is needed.

A relatively rare type of PCB (polychlorinated biphenyl) was used at Brunswick’s LCP plant, and over many years it spread through the marshes of the Turtle River and nearby creeks.

PCBs are a family of chlorine-based chemicals that were used in insulating oils for machinery. They were banned in the 1970s because of concerns about cancer risks and environmental damage.

In August, scientists examined the health of dolphins in Brunswick and around nearly undeveloped Sapelo Island farther north. They also took tissue samples from animals in both places.

The scientists discovered PCB levels in Sapelo dolphins were more than twice as high as on most of the East Coast, and came from a product called Aroclor 1268 that was used at the chemical plant.

The contamination in the area closer to the site of the factory was off the charts.

Compared to a typical East Coast count of about 64 parts per million, the Brunswick dolphins had about 400 parts per million.

Some animals had 2,900 parts per million, a level unprecedented in any other similar studies of wildlife contamination.

While the areas surrounding the closed plant have been the focus of testing up until now, it is likely to be widened to other communities over fears that the contamination could have spread.

If fish that are polluted in one place travel somewhere else before they’re eaten, then larger numbers of dolphins could suffer.

The dolphins’ PCB levels weren’t just high just from swimming near pollution, but because those chemicals became concentrated in the fat and tissue of fish that the dolphins ate.

The contamination from the pollution site “may be mobilized and move up and down the coast … as the prey move around,” said Teri Rowles, who directs a marine mammal office at the National Oceanic and Atmospheric Administration.

Because dolphins’ diets include pan fish like mullet, croaker and spot, scientists worry the same thing could be happening in people.

Sometime this year, CDC researchers will test that by collecting blood from people who eat a lot of locally caught seafood. They’ll also ask those people to keep a meal diary and to bring scientists a sample of whatever they normally eat, to test alongside the blood samples.

“What we’re very much interested in seeing is what the relationship is between what is in their food and what is in their bodies,” said Lorraine Backer, an environmental epidemiologist planning the project.

“There is potential for people to be exposed to these PCBs. Whether the levels are high enough to warrant concerns for people’s health … that is still to be determined,” said Lori Schwacke, a NOAA researcher with the Hollings Marine Laboratory in Charleston, S.C., who has led the dolphin study.

“These are such incredibly high levels,” she said, “it’s certainly enough to warrant further study.”

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