National Report — They combed through more than a million tons of hazardous debris covering 16 acres with nothing more than a nose to the ground in the days after the Sept. 11, 2001, terrorist attacks on the World Trade Center in New York City, while their human counterparts were outfitted in protective gear.

A decade later, about a third of the search-and-rescue dogs remain—most showing little evidence of ill health despite the prolonged exposure to toxic fumes from the pile. To the contrary, many of the responders who worked at Ground Zero are still plagued with physical ailments and psychological scars from the tragedy.

A bright spot on a dark day: Brought to Ground Zero in the days after 9/11 to help find and recover human remains, Otto says the search dogs did much more. (Photo courtesy od Dr. Cynthia Otto)

Each year, the deployed dogs participating in the study are examined by their veterinarians. They in turn send blood samples and chest X-rays to Penn. Also included in the annual update are surveys on behavior and general health that are completed by the dog's owners. If a dog dies, a necropsy is performed and the ashes of the dogs are returned to their handlers, Otto says.

Death and cancer rates in the deployed dogs are roughly the same as in the control group, and there are no signs of respiratory disease, Otto says. Though two more dogs died the week she was interviewed, Otto says the deployed dogs most often succumb to old age—not from problems related to their work after 9/11.

"It's not like these dogs are dying young," she says, adding that most live to 14 or 15 years of age.

"They're phenomenal dogs. There's a smattering of health issues, but not what you would expect," she says.

One of the only health differences noted between the control dogs and deployed dogs was an increased chance of heart irregularities, Otto says.

"That was unexpected, so we are watching that closely," she says. "They are not physical problems, per se, more radiographic changes."

In fact, radiographic cardiac abnormalities were significantly more likely to be diagnosed in deployed vs. control dogs, Otto reports in the Journal of Environmental Health (Sept. 2010). "Of the seven dogs with cardiac lesions, five had mild left-sided cardiomegaly with atrial involvement, one had right-sided cardiomegaly, and one had mild generalized cardiomegaly," she states.

Otto says a study of dogs in Mexico City indicates that enlargement of the heart is a condition that could be triggered by environmental pollutants. "Maybe exposure to the toxic chemicals in the air at Ground Zero set those dogs up for that, but there's no way to say for sure," Otto says. "There is no hard evidence yet."

The study is revealing a lot about the aging process in dogs, as Otto explains there have been few opportunities to follow this number of dogs so closely.