Toxic chemicals from a former chemical plant near Brunswick, Georgia, have been detected in seabirds, indicating that they have spread beyond the site via the food web.

Researchers at the University of Georgia’s Savannah River Ecology Laboratory found traces of a contaminated mixture called Aroclor 1268, which is linked to the Linden Chemical Plant, in egg and tissue samples of least terns, a short-range migratory seabird.

Aroclor 1268 is composed of toxic chemical compounds known as polychlorinated biphenyls, or PCBs. The chemical was used to produce insulation materials at the Linden Chemical Plant — now a Superfund site — at the Turtle River estuary near Brunswick until 1994.

“Because its only use in the Southeast was at the now-closed Linden Chemical Plant, we know this is the original source of the contaminant,” study co-author Gary Mills explained.

Over a two-year period the researchers took samples from six nesting populations at various sites along the Georgia coast, up to 68 miles from the plant. Results showed that the tissue samples contained enough Aroclor 1268 to cause a number of adverse effects in the birds, including lower egg production, physical and physiological abnormalities in offspring and immune system disorders.

It’s thought that the least tern ingests the contaminant when it consumes fish. Senior investigator Sonia M. Hernandez noted that, because shore birds are at the top of the food chain, they are important indicators of the health of coastal environments.

Previous studies have documented the presence of the chemical in reptiles, plants, fish, invertebrates and marine mammals.

Researchers should be concerned about the potential transmission to predator and scavenger species and the population risk to the least tern, Hernandez said.

She also highlighted the lingering duration of its effects in the environment.

“Finding Aroclor 1268 in these bird tissues such a long time after its production ceased is evidence of the persistence of the contaminant,” Hernandez concluded.

The results of the study have been published in the journal Environmental Science: Processes and Impacts.