Well, not being a expert at physics or particularly knowledgable about quasars, I can still say the following. If a quasar at the center of the galaxy ignites in 2012, manages to spew out enough radiation to be actually dangerous at that distance, and happens to somehow be aimed to intercept earth in it's travels, we'll all still be tens of thousands of years too dead of old age to care by the time it becomes a problem.