For the last three years, the Penn researchers tracked the health of dogs and handlers from the World Trade Center, the Pentagon and the Fresh Kills Landfill site on Staten Island, where debris from the World Trade Center was further searched.
"Overall, the lack of clear adverse medical or behavioral effects among the 9/11 dogs is heartening, both for the animals and the human rescue workers," said lead researcher Cynthia M. Otto, associate professor of critical care in Penn's School of Veterinary Medicine. "Since dogs age more rapidly than humans, they can serve as sentinels for human disease. We are encouraged that we do not see significant increases in cancer and respiratory diseases." The Penn researchers compared the dogs to a control group of search-and-rescue dogs that were trained similarly but not deployed. Although there is no single registry of all dogs deployed to search the 9/11 sites, the Penn researchers identified 212 deployed handlers, and 97 consented to participate.
Despite rumors of numerous deaths of 9/11 search-and-rescue dogs, only one was confirmed to have died during the search period. In addition, the study was able to demonstrate that the injuries and ill effects of the search itself were minor. After the first year of surveillance, of the 97 deployed dogs enrolled in the study, only one died. During the past three years, 15 deployed dogs have died, of which eight had cancer. At the current time, neither the death rate nor the cancer rate is different from that of the control group.
"Given the mature age of these dogs and their expected lifespan, the few deaths that did occur were not statistically significant," Otto said. "We can't say that these findings preclude illness later in life, but it is clear that we don't see any trends in the current physical or behavioral wellbeing of these dogs that would be cause for alarm."
Initially, blood tests showed that the deployed dogs exhibited higher bilirubin concentration and alkaline phosphatase activity, which indicates that their livers were actively filtering toxins from their bloodstream. The serum globulins were also higher in the first year in deployed dogs, suggesting activation of the immune system. As the study progressed, however, these numbers came down to close to those of the dogs in the control group.
"Early on, it is clear that these dogs were dealing with some stress from toxins, although we don't currently have evidence of adverse effects, continued surveillance is still warranted," Otto said.
Since there was a concern about airborne pollutants, such as asbestos, Otto and her colleagues also examined X rays taken of the dogs. The examinations showed no apparent lung abnormalities. While it usually takes humans at least 20 years to develop mesothelioma after asbestos exposure - a major fear at all three sites - the shorter life span of dogs often means a relatively shorter latency period for developing cancer.
To assess the psychological wellbeing of the dogs, their handlers were given questionnaires that focused on behavioral disorders, such as aggression or fearfulness, which may have arisen since 9/11. Here also the deployed dogs seemed similar to those of the control group.
An ongoing study led by Melissa Hunt of Penn's Department of Psychology is looking at the long-term psychological consequences for the human handlers.
"Since this is the first major study on search-and-rescue dogs and their handlers, we hope this data can be used to establish a baseline for future studies," Otto said. "Not only will it help ensure the health and safety of search-and-rescue dogs, but it will also help anticipate human disease as well."
Support for the study came from the AKC Canine Health Foundation, the American Kennel Club, Ralston Purina Co., the Veterinary Pet Insurance Co. and the Geraldine R. Dodge Foundation. The study also includes researchers at Michigan State University and the Centers for Disease Control in Atlanta.