Explain briefly about the selenium Toxicity?

There is a narrow margin between the beneficial and harmful intakes of selenium. The level at which selenosis occurs is not well-defined but threshold for toxicity appears to be 850-900 μg per day. Symptoms of chronic toxicity include brittle hair and nails, skin lesions with secondary infections and garlic odour in the breath. Chronic selenium poisoning in people is characterized primarily by loss of hair and changes in finger nail morphology. In some cases, skin lesions may occur.