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. 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. However, chronic cobalt ingestion has caused serious health problems at doses far less than the lethal dose. In 1966, the addition of cobalt compounds to stabilize beer foam in Canada led to a peculiar form of toxin-induced cardiomyopathy, which came to be known as "beer drinker's cardiomyopathy". Furthermore, cobalt metal is suspected of causing cancer (i.e., possibly carcinogenic, IARC Group 2B) as per the International Agency for Research on Cancer (IARC) Monographs. [http://publications.iarc.fr/_publications/media/download/2705/29aacee6b89ff816188dcd990b61a16ad6486eec.pdf [PDF]]  It causes respiratory problems when inhaled. It also causes skin problems when touched; after nickel and chromium, cobalt is a major cause of contact dermatitis. These risks are faced by cobalt miners. Cobalt can be effectively absorbed by charred pigs' bones; however, this process is inhibited by copper and zinc, which have greater affinities to bone char.