Do you understand how any of this works, or do you just assume you know because you watch Mythbusters?
White smoke from the PSU is a cartridge going off to expunge any fire inside, designed as a safety mechanism to prevent the entire system from becoming a fireball. It's nothing even remotely toxic unless you're in a vacuum and don't otherwise have oxygen flowing into your lungs.
OP: If your system went POP and you got white smoke from the PSU (and you're sure it was the PSU), then your other components are *probably* safe, but the PSU is now bricked. Get another PSU and try again, and this time check the voltage switch when you plug it in.