 Cobalt is an essential element for life in minute amounts . The LD50 value for soluble cobalt salts has been estimated to be between 150 and 500 mg / kg . Thus , for a 100 kg person the LD50 for a single dose would be about 20 grams . In the US , the Occupational Safety and Health Administration ( OSHA ) has designated a permissible exposure limit ( PEL ) in the workplace as a time @-@ weighted average ( TWA ) of 0 @.@ 1 mg / m3 . The National Institute for Occupational Safety and Health ( NIOSH ) has set a recommended exposure limit ( REL ) of 0 @.@ 05 mg / m3 , time @-@ weighted average . The IDLH ( immediately dangerous to life and health ) value is 20 mg / m3 . 
