Most barium compounds are very poisonous, especially the more soluble barium compounds such as the chlorate and nitrate. A dust mask should be worn at all times when working with barium carbonate. Unlike its soluble cousins which can be easily washed from the hands with lots of water the carbonate is not so easily removed and care to remove the powder from under finger nails is important before eating etc. Barium carbonate is soluble in stomach acid, and therefore a poison by ingestion.