something to notice too is that the work and attention required to assemble Apple's products are greater than other companies thus Apple expose workers to more health damages
I do not think there is any correlation either way, but one could argue that, say, putting together a 'work fast, but the end result must be spotless' item is less risky for one's health than putting together a (purely hypothetical, for the sake of the argument) 'we do not care about shards on the glass screen; blood spots on the screen are OK, too, but do it in ten seconds or we will not make a profit' product.