You have this completely backwards. The lower a job pays, the more likely it is to be dangerous or disgusting. Some of the very lowest paying jobs are the most dangerous (lumberjacks) or the most disgusting (janitors).
In the end it's all supply and demand, there is no causal connection between low pay and dangerous/disgusting work, quite the opposite. If a job is dangerous or disgusting and still low paid, it just means that the barrier to entry is even lower. Anyone with two arms and legs can be a janitor.
