Mercury (element) polluted water. They arise by a process known as biomethylation. Mercury is used primarily for the manufacture of industrial chemicals or for electrical and electronic applications. It is used in some thermometers, especially ones which are used to measure high temperatures. A still increasing amount is used as gaseous mercury in fluorescent lamps, while most of the other applications are slowly phased out due to health and safety regulations and is in some applications replaced with less toxic but considerably more expensive Galinstan alloy. Mercury and its compounds have been used in medicine, although they are much less common today
Demon in a Bottle he carries in his briefcase, flies out of the plane, and guides it to a safe landing in the ocean. Navy ships approach and soldiers help the passengers to safety, and bring Iron Man to an island base. They tell him the tank was thrown by Namor, who was defending a resident of the island that the soldiers were trying to remove, because the island is used as a toxic waste disposal site. Iron Man confronts and fights Namor, before it's revealed that the soldiers actually belong to the Roxxon Oil Corporation, which is secretly occupying the island to mine