My Pop was a firefighter in NYC, so I understand your fears. Have you ever had blood tests for cancer, you can order those for specific multi-cancer early detection (MCED) tests (Galleri, Cancerguard) or specific cancer markers (colon, colorectal)?
Before beginning KLOW or GLOW Protocol,
Request a "Firefighter Physical": When seeing your doctor, specify you need an NFPA 1582/1583 physical. Most standard "annual checkups" do not include the specialized blood work or urinalysis needed for early detection of occupational cancers.
You've got rights, depending on which state you're working in, these cancer pre-screenings should alleviate some of your concerns.
National Firefighter Registry for Cancer
nfr.cdc.gov