Firefighters Are at Increased Risk for Many Cancers

CINCINNATI, Nov. 10 -- Firefighters acquire on-the-job elevated risks for a variety of malignancies, according to researchers here.

They are significantly more likely to develop multiple myeloma than other workers, and also appear to be at elevated risk for non-Hodgkin's lymphoma, prostate, and testicular cancers, Grace LeMasters, Ph.D., of the University of Cincinnati, and colleagues, reported in the November issue of the Journal of Occupational and Environmental Medicine.

Firefighters have a "possible" elevated risk for several additional cancers, including all including melanoma and other skin cancers, leukemia, plus cancer of the brain, rectum, buccal cavity and oral pharynx, stomach, and colon.

"We believe there's a direct correlation between the chemical exposures firefighters experience on the job and their increased risk for cancer," said Dr. LeMasters, a professor of epidemiology and biostatistics.

She and her colleagues conducted a review and meta-analysis of 32 studies, confirming earlier findings that firefighters had an elevated risk for multiple myeloma, as well as probable associations with other cancers.

In addition to the hazards inherent to putting out fires, firefighters are frequently exposed to hazardous substances both at the scene of a blaze and in the firehouse, the authors noted.

"At the fire scene, firefighters are potentially exposed to various mixtures of particulates, gases, mists, fumes of an organic and/or inorganic nature, and the resultant pyrolysis products," they wrote.

Firefighters may be exposed to heavy metals, carcinogenic chemicals, volatile gases, minerals such as asbestos, and other substances with acute toxic effects, they added.

"In some situations, respiratory protection equipment may be inadequate or not felt to be needed, resulting in unrecognized exposure," they wrote. "At the firehouse where firefighters spend long hours, exposures may occur to complex mixtures that comprise diesel exhaust, particularly if trucks are run in closed houses without adequate outside venting."

Firefighters may also be exposed to particulate matter from building debris, including pulverized cement and glass, fiberglass, asbestos, silica, heavy metals, soot, or combustion products, they wrote.

To determine quantitative and qualitative cancer risks among firefighters, the authors conducted a comprehensive data search using three criteria: pattern of meta-relative risk association, study type, and consistency among studies.

They used the criteria to assess whether risks for 21 cancers were probable, possible, or unlikely, following the model developed by the International Agency for Research on Cancer.

They identified 32 studies with data on 110,000 firefighters, mostly men, who met their criteria. The studies used either local or national worker records, or local, regional or national population records for comparison.

The investigators found that firefighters had a probable risk for multiple myeloma, with a summary risk estimate of 1.53 (95% confidence interval, 1.31-1.73). Their risk for non-Hodgkin's lymphoma was 1.51 (95% CI, 1.31-1.73), and for prostate cancer was 1.28 (95% CI, 1.15-1.43).

In addition, testicular cancer, which was reported in only four of the 32 studies and originally had a "possible" ranking, was upgraded to "probable" because of its high summary risk estimate of 2.02 (95% CI, 1.30-3.13).

Cancers deemed to be possibly associated with firefighting included skin cancer (all), melanoma, leukemia, and cancer of the brain, rectum, buccal cavity and oral pharynx, stomach, and colon.

"There's a critical and immediate need for additional protective equipment to help firefighters avoid inhalation and skin exposures to known and suspected occupational carcinogens," said co-author James Lockey, M.D., also of the University of Cincinnati. "In addition, firefighters should meticulously wash their entire bodies to remove soot and other residues from fires to avoid skin exposure."

The investigators wrote that risk for the four probably-associated cancers may be related to a combination of types of exposure, routes of toxin delivery to target organs, and, indirectly the effects of modulation of biochemical or physiologic pathways.

"In anecdotal conversations with firefighters, they report that their skin, including the groin area, is frequently covered with 'black soot'," the investigators wrote. "It is noteworthy that testicular cancer had the highest summary risk estimate (2.02) and skin cancer had a summary risk estimate (1.39) higher than prostate (1.28)."

The authors noted that the actual risks of cancer among firefighters relative to other populations may be underestimated because of a healthy worker bias. That is, firefighters must meet strict physical criteria to join the service and keep in good physical shape, and they have good health benefits.

"The healthy worker bias may be less pronounced, however, for cancer than for conditions such as coronary heart disease," they wrote. "Furthermore, tobacco is unlikely a contributing factor because cancers known to be associated with smoking such as lung, bladder, and larynx were designated as unlikely and corresponding summary risk estimates were not statistically significant."