We're "at the mercy of a shifting chemical landscape."
Decades ago several bird species in the Great Lakes—including the iconic bald eagle—faced an uncertain future because toxic chemicals were threatening their populations.
While several bans and policies have offered some protection, the same chemicals threatening these birds 60 years ago continue to accumulate in their bodies—and new chemical threats are adding to their toxic burdens, according to two new studies.
The two studies add to evidence that pollutants not only persist in the Great Lakes, but continue to travel up food chains to reach and endanger apex predators; and suggest that birds in the Great Lakes continue to impart toxic loads to their offspring—results that do not bode well for long-term bird populations. In addition, as birds are sentinel species, the studies show how previous and existing regulations have been inadequate at protecting all biota of the Great Lakes, including humans, from the harms of these industrial chemical pollutants.
In the first study, published online in Environment International last month, researchers examined how legacy pollutants around Lake Erie such as polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and dichlorodiphenyltrichloroethane (DDT) continue to bioaccumulate in common terns. These migratory seabirds spend winters in Central and South America but stay near the Great Lakes from late April to mid-October, relying on the area as breeding grounds.
"Every common tern we looked at had some level of PCBs and PBDEs," Diana Aga, an analytical chemist at the University of Buffalo and co-author of the study, told EHN.
The U.S. phased out PBDEs in 2013, PCBs in 1979, and DDT way back in 1972. PBDEs were most commonly used as flame retardants; PCBs were used as coolants and electrical insulation; and DDT was a widely used insecticide. The chemicals were all banned because they were showing up in wildlife and humans and are linked to a variety of health impacts.
All three are persistent organic pollutants, chemicals that remain stable in the environment, lingering in sediments and plants rather than breaking down. Over the years, these chemicals move up food chains as predators eat contaminated prey, bioaccumulating in apex predators like the common tern. That is why birds of the Great Lakes region continue to feel the aftereffects of decades-old pollution.
To mitigate the accumulation of toxics in their bodies, female common terns, like other birds and animals exposed to chemical pollutants, will offload chemicals to their babies, said Aga—"out of all the birds at different life stages, tern eggs birds had the highest accumulation of these pollutants."
Persistent organic pollutants are fat soluble, and egg yolks are full of fat, so the eggs they lay provide mother terns with an opportunity to rid themselves of those harmful compounds. This results in chicks that are born with already very high loads of toxics, if they manage to hatch at all.
While there is very little research that explicitly looks at the toxicology of PBDEs and PCBs in terns, a few older studies suggest a link between these contaminants and physical abnormalities like twisted beaks or deformities in eyes and feet in several other bird species like chickens, kestrels and cormorants. DDT, on the other hand, has long been linked to egg shell thinning and reduced hatching success.
Peregrine falcons in Detroit. (Credit: pverdonk/flickr)
“It's a little bit like whack-a-mole”
The second study, published in Environmental Research this month, showed how peregrine falcons accumulate perfluorinated chemical pollutants like perfluoroalkyl substances (PFAS), which have made headlines in recent years for being "forever chemicals"—since they take exceedingly long times to break down. Human PFAS exposure is linked to cancer, endocrine disruption, and elevated cholesterol, among other health detriments.
The study's results suggest that peregrines—birds of prey and one of the most widely found bird species—get exposed to these chemicals through maternal transfer to eggs, their diets via contaminated smaller birds and mammals, and also simply by living in areas with higher levels of these substances.
"We're also at the mercy of a shifting chemical landscape," Robert Letcher, an environmental toxicologist at Environment and Climate Change Canada and co-author of the study, told EHN.
Despite being largely phased out in North America, perfluorooctanesulfonic acid (PFOS), a kind of PFAS that was officially added to the Stockholm Convention's list of persistent organic pollutants in 2010, is "still singularly the most bioaccumulative, highest level perfluorinated compound that's being reported in the environment and in the biota," said Letcher. He said the chemical industry is consistently developing new chemicals to replace those that are phased out, chemicals that stay largely secret until they are investigated and identified by scientists like himself.
"We have to do a little bit of chemical sleuthing to figure out our targets," Letcher said. Through that sleuthing, he says, scientists have been able to trace PFOS replacements like F53B, GenX, ADONA, and a number of others that are all different minor variations of PFOS, but it's hard to keep up with the sheer number of replacements that just keep coming.
This perpetual conveyor belt of toxics, on top of the already varied arsenal of legacy pollutants, makes zeroing in on what each chemical is doing to the falcons' health extremely difficult, Kim Fernie, another environmental toxicologist at Environment and Climate Change Canada and one of Letcher's co-authors, told EHN. Not to mention that there are a multitude of other environmental factors like climate change that could be acting in tandem, she added.
Despite the unknown, the results are concerning, as PFAS chemicals have been previously shown to be overtly toxic. Research in other animals reveals that PFAS decreases reproductive success, can cause developmental defects, endanger kidney and liver health, and even cause cancer—effects that researchers suspect may translate to the health of these falcons and other Great Lakes birds.
"As we continue to have these new chemicals crop up, it's a little bit like whack-a-mole," Laura Rubin, the director of the Healing Our Waters—Great Lakes Coalition, told EHN. The Coalition is a group of about 165 NGOs and nonprofits throughout the Great Lakes region that pushes for clean water and the protection of landscapes and their wildlife.
"What we need now more than ever, is a precautionary principle, the idea that we should not be introducing new pollutants or chemicals until we know the effects," said Rubin. Currently, the onus to prove that a chemical is safe does not lie with the company manufacturing it. Without a precautionary principle, industries are free to release chemicals under presumed ignorance of the harms their products cause to the environment. Scientists and activists then have to identify and raise alarms about each individual pollutant. It becomes a repetitive story with different faces.
The destructive chemical pollutants of decades past yielded a few really seminal pieces of legislation, Rubin said—The Clean Water Act, The Clean Air Act, and the National Environmental Policy Act, to name a few. "But those are starting to show their age and they need some updating in terms of responding to these newer classes of chemicals." Getting a precautionary principle in place would be a monumental step forward for protecting our landscapes, she said.
A warning for us all
Pollution in the Great Lakes has significant implications for human health as well. According to the Great Lakes regional Water Use Database, 30 million people depend on the 40.4 billion gallons of water withdrawn from the Great Lakes-St. Lawrence River Basin each day. The land around that area is also home to roughly 10 percent of the U.S. population and more than 30 percent of the Canadian population, according to the U.S. Environmental Protection Agency.
A 2016 study also found that public water supplies with PFAS concentrations at or above the EPA's recommendations reached as many as 6 million U.S. residents. PFAS in food is also of concern, especially via manufactured food, food packaging, and fish consumption. One report of PFOS concentrations in fish found the highest levels in lake trout collected from Lake Ontario.
These birds being contaminated by all these chemicals are really acting as canaries in the coal mine for us humans, Alicia Perez-Fuentetaja, an aquatic ecologist at SUNY Buffalo State University and one of Diana Aga's co-authors, told EHN.
To Perez-Fuentetaja, the birds should be a warning to us all.
"These birds are not even smoking, they're not drinking, they're not doing any of the things we do," she said "They're just eating their food in the wild, and look at the exposure they have."
Banner photo: Common terns in Hueston Woods State Park, College Corner, Ohio.(Credit: Andrew Cannizzaro/flickr)