My dad was a fireman, I can't give you any figures but many of his friends from the fire service left due to ill health, mostly due to back problems.
In most cases this was just the body finally giving up due to the strain of the work rather than direct incidents on the job.
A firemans life is generally boring (depending on location) filled with safety visits and getting people out of lifts. The number of fires they attend in minimal and hardly ever life threatening.