<unk> in humans results in a number of medical problems.<unk>  is a vital element of nutrition in very small quantities (adult male daily intake 2.3 milligrams). However poisoning may occur when greater amounts are ingested.
Manganese deficiency 
Zinc toxicity
Zinc deficiency
Biotin deficiency
Chromium deficiency
Copper deficiency
Lead poisoning
Boron deficiency 