Hafnium metal does not normally cause problems but all hafnium compounds should be regarded as toxic, although initial evidence would appear to suggest danger is limited.

Hafnium metal has no known toxicity. The metal is completely insoluble in water, saline solutions or body chemicals.

Exposure to hafnium can occur through inhalation, ingestion, and eye or skin contact.

Overexposure to hafnium and its compounds may cause mild irritation of the eyes, skin, and mucous membranes in laboratory animals. 

No signs and symptoms of chronic exposure to hafnium have been reported in humans, neither has hafnium toxicity from food been recorded.