In its usual humorously informative way, XKCD created the following chart which provides another measure of understanding radiation exposure.

Exposure to 1 Sv all at once (as opposed to spread out over time) is dangerous, and qualifies as minor radiation sickness.
1 Sv =  1,000 mSv (millisievert) / 1 mSv = 0.001 Sv
1 Sv = 1,000,000 ?Sv (microsievert) / 1 ?Sv = 0.000001 Sv

no images were found

More information can also be found HERE.

And from Wikipedia as well.