Researchers tested five species of commonly hunted waterfowl in the northeast Atlantic Flyway and, in every sample, found contaminants that could impact the health of the birds, as well as the hunters and others who consume them.
The study, published Jan. 15 in Science of the Total Environment and conducted in collaboration with the New York State Department of Environmental Conservation (NYSDEC) and other state agencies, found detectable levels of polychlorinated biphenyls (PCBs) and at least one organochlorine pesticide (OCP) and per- or polyfluoroalkyl substance (PFAS) in each bird sampled, in a representative group of more than 100 birds collected across four states and nine ecological regions.
Among the findings, the researchers determined that current New York State Department of Health consumption advisories - of two meals per month of waterfowl - may be appropriate, but some species are more or less contaminated than others. In risk assessments, the researchers found that some of the contaminants likely expose consumers to potential cancer risk, although how this risk compares to the consumption of other foods is unclear.
Of the five species studied, Canada geese and wood ducks had lower levels of contaminants than mallards, American black ducks and American green-winged teal, probably due to differences in their feeding habits, the authors said.
"The big picture is that these chemicals are out there, and wild animals are being exposed to them," said senior author Krysten Schuler, assistant research professor of public and ecosystem health, and wildlife disease ecologist for the Cornell Wildlife Health Lab in the College of Veterinary Medicine (CVM). "We're worried about it from the wildlife population standpoint: What do these chemicals mean for the birds? But then there's also the question of what it means for human consumption."
Hunters in the four participating states - New York, Pennsylvania, New Jersey and Connecticut - harvest and consume more than a half-million wild-caught ducks and geese each year. But in New York, the guidance on safe consumption has not been updated since the early 1990s and doesn't include some of the birds most likely to be consumed. The new data can now be used by health departments in all four states to assess current guidelines and craft new human consumption recommendations, when necessary.
"This provides a really good baseline," Schuler said. "We're not telling people what to eat or do. We're just providing the numbers."
In the risk assessments, researchers found that the levels of mercury and OCPs detected posed minimal risk to health for hunters who follow the current guidance on consumption, but they found that the levels of PCBs - human-made chemicals that were banned in 1979 - may be more likely to pose health risks, including increased cancer risk, although the authors said that more research is needed. The thresholds for safe consumption are variable depending on the level of acceptable risk, they said.
"We don't know what levels make a difference in birds or whether the different contaminants matter together or separately," said Brenda Hanley, co-author and research associate in the Department of Public and Ecosystem Health (CVM). "And we don't know how these animals compare to other wild animals that people harvest and eat."
The study also lays the foundation for more research on how these contaminants affect the birds.
"It's hard to know at what level these contaminants start to impact the bird's survival or reproductive success," said co-author Joshua Stiller, small game unit leader for NYSDEC, who initially brought the project to Schuler and her team. "But just understanding the current contaminant loads in these species is important, and we can get some ideas for future research to better understand the potential impacts on waterfowl populations."
Much of the previous research on contaminants has looked at animals linked to known sources of pollution. To understand the contaminant levels at the population level, the researchers collected birds from various regions in each state. This required a massive collaborative effort, with help from state wildlife and conservation agencies, which deployed biologists to collect birds from hunters willing to participate.
The biologists then sent the birds to the Wildlife Health Lab, where they were processed and sent on to other labs for further testing.
"For each bird, we had somewhere between 200 and 300 columns of data," said first author David Dayan '23, who started working on the project as an undergraduate and did everything from handling and preparing the birds to high-level data analysis and assessment. "Trying to paint a coherent picture from all of these different perspectives and data points was a really interesting way to do science."
In terms of conservation, Schuler said the widespread contamination of waterfowl is another warning sign.
"These animals are constantly losing wetlands and habitats and being forced into less desirable locations," she said. "This just highlights the importance of protecting those areas for these species."
Other co-authors include Wayne Richter and Jesse C. Becker at NYSDEC; Ian D. Gregg of the Pennsylvania Game Commission; Nate R. Huck from the Minnesota Department of Natural Resources (formerly from the Pennsylvania Game Commission); Min T. Huang of the Connecticut Department of Energy and Environmental Protection; Theodore C. Nichols of New Jersey Fish and Wildlife; Henry M. Spliethoff of the New York State Department of Health; and Lisa A. Murphy of the Wildlife Futures Program at the University of Pennsylvania School of Veterinary Medicine.
Funding for the study came from the U.S. Fish and Wildlife Service and the Association of Fish and Wildlife Agencies.
