According to a new study, chemicals that have not been made in the United States in years or decades are still appearing in the bodies of terns in the Great Lakes region.
The research focused on three types of compounds: polybrominated diphenyl ethers (PBDE), polychlorinated biphenyls (PCB) and the breakdown products of dichlorodiphenyltrichloroethane (DDT) known as metabolites.
Scientists discovered all three types of chemicals in the organs of over two dozen terns in breeding areas along the Niagara River and on the shores of Lake Erie. The pollutants were found at different stages of life, in chicks, adolescents and adults.
The researchers also discovered the compounds in emerald luster, a small fish that is the main food source for the terns in the region.
The study was published online on September 3 in Environment International and appears in the November issue of the journal. The authors included chemists Diana Aga and Steven Travis from the University of Buffalo and the biologist Alicia Pérez-Fuentetaja from SUNY Buffalo State.
Common Tern, North America, Copyright Frank Mantlik, from the Surfbirds Galleries
Sales of PBDE, a class of flame retardants for car seats, carpet upholstery, mattresses, and many other household products, ceased in the United States in 2013. The manufacture of printed circuit boards, formerly widely used as a coolant or insulating fluid in electrical transformers and capacitors, which ended in the country in 1979. The use of DDT, an insecticide, has been banned in the United States for nearly half a century since 1972. The metabolite of DDT that the team found in birds and fish is called dichlorodiphenyldichlorethylene (DDE).
“Those chemicals are still there. You don't just go away. With PCBs, for example, they haven't been made in the US for a long time, but you can still find them in the environment, in sediments, and in water. They have not been mined for many years. The fish eat organisms that they accumulate and then the birds eat the fish, ”says Dr. Aga, Henry M. Woodburn, Professor of Chemistry at Buffalo College of Arts and Sciences University.
“The common tern is an endangered species in New York State, and despite government efforts to find nesting sites and surveillance, their numbers have not increased much. This study shows how wildlife is affected by human pollution in aquatic systems and how the chemicals we produce can have a cross-generational effect that is passed from mother to chick, ”says Dr. Pérez-Fuentetaja, Professor of Biology at SUNY Buffalo State and Research Scientist at the Great Lakes Center in SUNY Buffalo State.
The PCB and PBDE levels in the birds were high enough to potentially affect the health of the birds and impair the recovery of the population, the authors write in their paper.
Pollutants affect terns at every stage of their life
The results illustrate how household and industrial chemicals have become ubiquitous in the environment, where they can persist for many years and pose risks to wildlife.
In terns, the threat begins in the earliest moments of their lives, even before they hatch, says Travis, the newspaper's lead author, who successfully defended his doctoral thesis at the UB in the fall.
He notes that the smallest chicks the team studied had higher concentrations of the chemicals than older birds and adults, suggesting that the compounds are passed on from parent to offspring. To test this hypothesis, Travis began work on a study to examine the levels of pollutants in the eggs of terns and other wild waterfowl.
"We see these really high levels in the smaller chicks, which suggests maternal contaminants are being carried over into the eggs," he says.
"These substances disrupt the reproductive system and are endocrine disruptors," says Pérez-Fuentetaja. “They are taxing the tern's livers as they have to try to get rid of these pollutants, but the bioaccumulative nature of PCBs, PBDEs and DDEs means that the birds cannot completely detoxify and some of their pollutants pass through body burden for the next generation. These substances can alter development and neurological processes and cause deformities, cancer and behavioral disorders. "
Research highlights the risks associated with old contaminants, as well as the urgency to protect the environment as new problems arise with other classes of persistent chemicals such as per- and polyfluoroalkyl substances (PFAS). Aga says that once they get into the water and soil, getting rid of stubborn pollutants is very difficult.
The new study shows how long banned chemicals have continued to threaten the health of the Great Lakes ecosystems.
"We can't say that all of the chemicals we see in the birds come from the Great Lakes, as the birds migrate and these compounds could also accumulate in other places along their migration route," says Travis. "But the specific types of PCBs and PBDEs we see in the emeralds are similar to those we see in birds. This pattern of chemical concentrations suggests that pollution in the Great Lakes region is causing at least some of that contamination . "
However, he adds, “One positive result of the study is that we only see the metabolite of DDT called 'DDE' in fish. This likely indicates that no new sources of DDT are being introduced on Lake Erie and the Niagara Rivers, and that the DDT present there is collapsing. "