Corrosion is mostly made up of Potassium hydroxide and/or lead salt and lead sulfate.
Corrosion itself is not dangerous to your health as long as you don't touch the corrosion or ingest it.
If you do get the corrosion from the battery terminals on your hands or other part of your body you need to wash it off immediately though as the acid contained in the corrosion can eat through clothing as well as skin.