Not long after 9/11, rumors began to circulate about the fate of the search-and-rescue dogs that dug through the rubble in the days following the tragedy. Stories appeared about dogs dying after inhaling toxic fumes and others developing cancer.

As a practicing veterinarian and associate professor of critical care in Penn’s School of Veterinary Medicine, Cynthia Otto wanted to know if the tales were true. As someone who had spent eight wrenching days providing medical care to the dogs at the World Trade Center site—Otto is a veterinary specialist with Pennsylvania’s FEMA urban search and rescue team—she needed to know.

Otto and a team of Penn researchers have spent the last three years tracking the health of the dogs who worked at the World Trade Center and the Fresh Kills Landfill site on Staten Island. “Since dogs age more rapidly than humans,” says Otto, “they can serve as sentinels for human disease.” Besides analyzing medical records from before and after the dogs’ 9/11 mission and surveys filled out by the handlers, the team also looked at blood work and X-rays.

The good news is the 97 dogs in the study don’t seem to have suffered adversely from their 9/11 deployment. Compared with a control group who were similarly trained but not deployed, they showed no greater incidence of death or cancer. This finding surprises Otto. “I was expecting something more tangible,” she says. “At least respiratory conditions.”

The team did notice an increase in the stimulation of the dogs’ immune systems in the weeks following the attacks, but it resolved soon after. There may be no long-term effects, says Otto, “or, the immediate effects may have cleared but sometime later something could show up and it just took time for it to develop.”

The AKC Canine Health Foundation, which provided much of the funding for the study, has approved two more years of study, which Otto says is necessary. “I think that we need to be vigilant,” she says. “We’d like to follow these dogs for the duration of their lives.”

A related study, headed by Melissa Hunt, associate director of clinical training in Penn’s Department of Psychology, is looking for patterns of depression or post-traumatic stress disorder among the dogs’ handlers. When all Hunt’s data are in, Otto says she hopes to “look and see if the people who had more emotional problems had dogs with more physical problems.” It’s a chicken-and-egg situation, she says. “Handlers and dogs are always a team. The dogs are their personal pets as well as professional partners. The bond between these people and animals is incredible.”