On the southeastern coast of the United States, the new canary in the coal mine may be dolphins. A long-term study of two populations found extraordinarily high levels of disease, which is likely related to high levels of pesticides and other pollutants in their bodies — a sign of ecosystem-wide problems, and also a warning that people in the region may also be at risk.

Between 2003 and 2015, researchers examined 360 dolphins caught and then released off the coast of Charleston, South Carolina and in Florida’s Indian River Lagoon. The results, reviewed in the journal Diseases of Aquatic Organisms, were troubling. Only 43% of the dolphins were considered healthy. Most were infected or afflicted by virulent fungi, bacteria and viruses, a disease profile that suggests profound disturbances in their immune systems. “In other species, this type of prolonged smoldering inflammation is associated with cancer, autoimmune disease, cardiovascular disease and increased vulnerability to infectious disease,” says Greg Bossart, chief veterinary officer at the Georgia Aquarium and part of the research team.