Splitting the heavy metal group may not be necessary because only a thin line exist between their beneficial effects and the toxicity so they should still be treated as one.

Paracelsus stated already centuries ago, that only the dosis determines whether something is a poison or not.

Chromium (III) is not toxic and is used as medicine.

Cr(VI) is toxic,as solution or as dispersion in drops or solid power in air.

It may gives us, dermatitis,renal failure, may be teratotoxic,, genotoxic,

Act as a carcinogen and acts over the peripheric nervous system.