I have found that the most dangerous jobs are:
1) Mercury mining
2) Arctic and subarctic fishing
3) Farming
4) EOD (Explosive Ordnance Disposal)
5) Mining (below ground not strip mining)
6) Metal refining, including furnace lancing, etc
7) Industrial cleanup, including cleaning chemical reactors, heat exchangers etc
8) Deep sea diving ocean salvage
9) Shallow diving depths of less than 100ft
10) High-rise construction worker
And my main definition of 'hazardous' is directly based on the probability that the job in question will kill you if you had such a field of work.
Mercury mining one is constantly exposed to mercury vapor and rock fall.
Any kind of fishing exposes one to extreme weather conditions in which the probability of being rescued can be small to nil.
Farming can be extremely dangerous, I personally know of a farmer getting his arm ripped off, when he fell into a spinning PTO shaft, another fellow had a three quarter ton round bale fall off his front end loader onto him wile he was on his tractor and broke his back, he was on that tractor for ten hours before he was found, I my self suffered three broken ribs when I was trampled.
The main danger of EOD is being blown to pieces if you make a mistake, like removing a 2000lb UXB from a factory.
In mining there is the constant risk of rock fall, coke damp, and poison gas. Now you might be thinking "Neutrino detectors are located in mines how can they be that unsafe?" well that is because they are no longer being worked.
Metal refining exposes a person to lethal chemicals like cyanide and temperatures, and getting hit by a 20lb blob of white hot steel will make a mess out of you.
In industrial cleanup one can be exposed to all kinds of chemicals, and hydrolic cleaner rams can punch a hole through a person like a 90mil at point blank range, and fall risk such a falling in a 200ft tower or down a 500ft utility shaft (safety belts are rarely used).
Diving both shallow and deep exposes one to nitrogen narcosis, decompression sickness, equipment malfunction causing your mixture to being wrong (too much oxygen or helium during deep dives).
High-rise construction presents many hazards such as being crushed, falling, and being impaled on rebar.
And as I stated before I was a farmer for nearly 30 years (had to pay college expenses somehow) and getting your hands and arms occasionally slashed by barbed wire, getting tagged by a horse or cow, slipping and falling face first into a tractor drawbar, being nailed by a 2000lb bull, and having implements drop on ones person; and doing the job in rain, storm, snow, ice, flood, high wind, and blazing summer heat; wile are not common occurrences are rather likely to happen unless one is extremely vigilant and some times it is going to happen like wile running fence and your horse spooks and explodes under you and you are just lucky enough not to fall into the fence, split your skull, break your back, neck, other parts of your anatomy, or worse having 1200 pounds of frightened equine coming down on top of you are things that can just happen without the slightest indication.
Now there are other positions, jobs, and other dangerous jobs that are equally dangerous, such as being a firefighter, or an infantryman during time of war, to name a few but as I said before I believe that the measure of danger in this case is directly proportional to probability of mortality over time. If your a postman or post woman you are not very likely to die of a paper cut, unless it has anthrax on it.