Banned decades ago, PCBs still pose a threat to wildlife


HOLDERNESS, NH – While cruising her boat to a driftwood platform in an idyllic New Hampshire lake where “On Golden Pond” was filmed, biologist Tiffany Grade spotted what she had feared.

An olive-brown loon egg with black spots sat on a nest, abandoned by its parents and with no chance of hatching. Gently picking it up with gloved hands, Grade placed the egg in a zippered bag and packaged it in a cooler.

The egg was sent to a lab in Canada to test for chemicals, including polychlorinated biphenyls, or PCBs, that were found in other Squam Lake loon eggs, fish there and a tributary of the Lake.

Grade is studying the potential link between PCBs and declining populations of fish-eating birds known for their sharp beaks, spotted black and white backs, iridescent greenish heads, and haunting calls.

The presence of PCBs on a lake in the shadow of the White Mountains shows how these heat-resistant chemicals once widely used in electrical equipment and other industrial applications continue to pose a threat to wildlife more than four decades after being banned in the USA.

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

In New York City, researchers found that chickadees and songbirds that ate PCB-contaminated insects along the Hudson River sounded a little differently than those in uncontaminated areas of the Adirondacks. Researchers at Cornell University believe that PCBs interfere with the development of a part of the bird’s brain responsible for song and could have reproductive consequences.

PCBs continue to move up the food chain, with animals at the top often harboring the highest concentrations.

The Marine Mammal Center responds to 800 marine mammals stranded each year along 600 miles (965 kilometers) of the California coast. A 2020 study of stranded adult sea lions concluded that PCBs and DDT, which were also banned decades ago, contribute to cancer rates of up to 23%.

“This cancer rate is mostly unprecedented in wildlife,” said Cara Field, medical director of the center, adding that the disease had caused “complete systemic breakdown” in the animals and their fat contained much higher levels of PCBs. higher than those without cancer.

Fish-eating birds have also suffered from exposure to PCBs.

Over the past several decades, studies at a Superfund site in Massachusetts, islands in New York Harbor, and contaminated sites in the Great Lakes have revealed significant levels of PCBs in common terns, roseate terns and others. endangered, Caspian Terns, Herring Gulls and Double-crested Cormorants. . Scientists found that PCBs, sometimes in combination with other chemicals, suppressed birds’ immune systems, increased infertility, and reduced chick survival compared to unpolluted sites.

At Squam Lake – site of the 1981 film starring Henry Fonda and Katharine Hepburn and now a tourist destination – Grade and his colleagues on the Loon Preservation Committee, which has worked since 1975 to protect New Hampshire loons, want to know why they produce so a few chicks.

The population collapsed between 2004 and 2005 – from 16 pairs to nine – and took a long time to recover. This year, there were just 14 pairs recorded on the lake, compared to 312 in other parts of the state. Only three chicks survived – still less than half the productivity of other New Hampshire lakes.

The committee, which began testing eggs from Squam Lake in 2007, found that PCBs and other contaminants were up to six times higher than eggs tested elsewhere in New Hampshire, Maine and New State. York. The association also found PCBs in a tributary flowing into the lake and their crayfish, leading to a theory that the oil containing PCBs used to control dust on dirt roads there are decades could have reached the waterways.

Contamination with loon eggs prompted the state to test smallmouth bass and lake yellow perch. And high levels of PCBs have led to a 2020 health advisory limiting the amounts of fish consumed by anglers.

“We would not have suspected that Squam Lake would have been a place where this was a problem,” said Ted Diers, administrator of the state’s Watershed Management Office. “There is no industry. It just raises a lot of questions that we really can’t answer at this point.

Loons, an endangered species in New Hampshire, face a myriad of challenges.

Predators that prowl the shore like raccoons loot their nests. Territorial conflicts kill birds. They are poisoned by ingesting lead fishing tackle. Their nesting sites are the losers in terms of development. And a warming climate can overheat loons and flood their nests.

Researchers also found PFAS flame retardants, the pesticide chlordane, and other chemicals in dive eggs. But PCBs were in the greatest concentrations, although Grade says more work is needed to assess what is causing the bird’s poor reproductive performance.

“Contaminants aren’t the only thing these loons have to deal with. They face a lot of things, ”she said. “It’s not easy to separate. It’s a lot easier if you sit a bird in the lab and dose it with contaminants and see what happens. Obviously that’s not what we’re doing.”

Anne Kuhn, a United States Environmental Protection Agency scientist who has researched contaminants in wildlife, agreed that it might be difficult to determine the impact of PCBs on Squam Lake loons.

His own work found that mercury, often from coal-fired power plants, combined with shoreline development and human activities in New Hampshire lakes, was hurting loon populations. But mercury alone was not.

Likewise, said Diane Nacci, a research biologist for the EPA, it could be that PCBs and other chemicals working together are causing the problem.

“Any single stressor might not be enough to affect reproduction in loons, but together it could be the straw that broke the camel’s back,” Nacci said.

For now, Grade is collecting abandoned eggs from Squam and other New Hampshire lakes and testing them for contaminants, looking for elusive answers that could help loons survive. “They are absolutely charismatic birds,” she said. “It’s hard to imagine a New Hampshire lake without loons.”


Follow Michael Casey on Twitter: @ mcasey1


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