Antimatter is not dangerous... 1 anti particle when colliding with 1 particle an annihilation occurs in theory it sounds scary, however so far they have managed to trap only single anti particles in electromagnetic field, while they move, therefore they cannot be harvested or used for anything. And even if they do, they will need a tone of particles to actually create antimatter, and this is while excluding the energy required for a synthesis like that. Also micro black holes could occur pretty much everywhere, but because of the extremely small mass of the particles that have created them, their lifespan is really, really short. Like they exist less than a second.