Firefighters are at a somewhat greater risk for developing cancer compared with the general public, but this elevated risk can't be directly related to toxic smoke inhaled during training exercises, according to a recent study.

The 10-month investigation conducted by the Johns Hopkins Bloomberg School of Public Health at the request of the Maryland Department of Health and Mental Hygiene was designed to determine if cancer clusters diagnosed among a group of Anne Arundel County, Md., firefighters could have been caused by smoke inhaled during training.

From 1971 to 1979, the department burned waste oil containing polychlorinated biphenyls during training exercises. The burning of the waste oil exposed firefighters to PCBs and other potentially carcinogenic compounds created by their combustion, such as polychlorinated dibenzo-p-dioxins.

The investigation was based on interviews with firefighters and an extensive review of research on cancer occurrence among firefighters. Seventeen Anne Arundel County firefighters told investigators they had been diagnosed with at least one cancer, nearly half of them with skin cancer. Two firefighters were diagnosed with brain cancer and three with leukemia or non-Hodgkin's lymphoma. Other cancers found were of the bladder, colon, lung and prostate.

Results indicated that, compared to the general public, firefighters were at a slightly greater risk for all cancers, and specifically those of the bladder, brain, colon, lymphatic system, kidney, pancreas, prostate, skin, rectum and testicles. Firefighters with greater exposure to fires appeared to be at a higher risk for cancers.

However, the researchers said it wasn't possible to recreate the doses of PCBs and byproducts received by the firefighters who trained at the academy in the 1970s, and therefore difficult to estimate the specific risk to this group.

These gaps in the evidence, however, don't mean there is no risk to firefighters.

“Further research on the risk of cancer and other diseases among firefighters is needed,” said Jonathan Samet, M.D., the lead investigator. The report outlines several strategies for determining the risks of cancer and other diseases among firefighters.

The report is available online at www.jhsph.edu/firefighters.