A number of studies have found that firefighters have elevated cancer rates, though they have not always been consistent in the specific types of cancer.

In the current study, researchers found that professional firefighters had higher-than-expected rates of colon cancer and brain cancer. There was also evidence, albeit weaker, that they had elevated risks of bladder and kidney cancers, as well as Hodgkin's lymphoma

For their study, the researcher combed through nearly two decades' worth of data from the Massachusetts cancer registry. Between 1986 and 2003, the registry recorded 2,125 cancer diagnoses among professional male firefighters.

The researchers found that, compared with men in other occupations, firefighters had nearly twice the risk of brain cancer and a 36 percent higher risk of colon cancer. They also showed higher risks of bladder cancer, kidney cancer and Hodgkin's lymphoma, but the evidence was weaker due, in part, to the relatively small number of cases.

Other researchers have called for greater efforts to protect firefighters from the toxic substances that may be fueling these elevated cancer rates -- including less cumbersome protective equipment that firefighters can keep on when they are near a fire.

Experts also recommend that firefighters shower as soon as they return to the firehouse, in order to remove contaminated soot from their skin