When killed in duty, it's most often due to a traffic accident. [0] Garbage men die when their own truck runs over them.[1] Additionally, trash collectors get a lot more repetitive stress injuries. The cause of death for garbage men is just as intrinsic, to their job. It's just that the sanitation workers' union isn't as politically popular.
As for firefighters, it's literally no more deadly than being a painter (8.9 fatal injuries per 100k). They're both climbing tall ladders with one hand. It may not be romantic to say that, but that's the actuarial science.
According to another post, the study attributed much of the difference to shift work and bad eating habits that may result from shift work. This also isn’t unique to police work among blue collar workers.
Police and fire employees tend to live shorter lives due to specific conditions related their occupation. It’s apples and oranges.