The magnetic fields from a ceramic or glass-topped hob can be lower than those from a traditional electric hob, but some halogen rings can give off particularly high levels.

What you can do:
It is recommended that as well as avoiding halogen rings, you avoid magnetic induction hobs because, although they are very energy efficient and fast to use, they produce significant levels of EMFs. Safest of all are gas cookers, or slow cookers which use very low power.