"Agency for Research on Cancer named the occupation of firefighting as possibly carcinogenic to humans. Their analyses of multiple studies concluded that firefighters experience a 50 percent increased risk of testicular cancer, a 30 per-cent elevated risk of prostate cancer and a 21 percent elevated risk of non-Hodgkin lymphoma, compared to the general population. Chronic exposures to toxic combustion products found in the fireground environment are believed to contribute significantly to the higher cancer occurrences in firefighters. When used during fire suppression and over-haul stages, the self-contained breathing apparatus (SCBA) protects the highly susceptible respiratory tract from toxic combustion products in smoke and soot."
U.S. Department of Homeland Security: https://www.dhs.gov/