Lot's of things can kill us. People have been changing their car brakes for a long time. If your car breaks fails, it can kill you, your passengers and other's outside of your car. People have been fixing their electrical appliances, it can electrocute you. Gas lines and furnace can explode. There's a lot that we do that can kill us if done incorrectly. This doesn't mean that we shouldn't do it. At the end of the day it's humans that built it.