No effect has ever been shown, nor even suspected.
Static magnetic field is even an unusual case: there never was any notable conspiracy theory or hysteria about a negative effect. Almost everything else (electricity, EM, IR, etc.) has opponents certain that they are nocive (sometimes because they really are, at much higher dosage that their normal usage).
Not for static magnetic field. The only dummy theories you'll find about static magnetic fields are positive (they are said to cure pain, even diseases, to help to communicate with spirits, to find water, etc.)
MRI use static magnets much much stronger than every thing you could buy, and nobody has never shown or even suspected any negative effects.
Now, the very strong magnets could be dangerous, but for some more pragmatical reasons: If you handle a pair of them without care, they could easily crush your finger while clapping. Plus, if you break them, I am not sure it is very healthy to breath the dust of heavy metal.