If the mine owner/operator signed a contract with the union stating all employees have to be part of the union yes.
Not ALL jobs. Each job has different dangers and safety requirements. If I don't want to have rocks fall on my head, I shouldn't work in a mine, I should work in a restaurants, is what you seem to be saying. If there's a mine in town with compulsory union membership, if I don't want to join the union, I'll have to work elsewhere, isn't it?
As for safety. Certain jobs are by nature more dangerous then othes, even with stringent safety regulations. A prison guard is more likely to be injured then a secretary. All the safety regulations in the world will not change that. If a person is unhappy with the danger that some jobs present, then they should look for a position elsewhere.