Fish at the top of the food chain (e.g., tuna, swordfish, or shark) may concentrate considerable mercury in their tissues.

Atmospheric elemental mercury settles in water, where it is converted by microorganisms into organic (methyl or ethyl) mercury, which is ingested by smaller creatures which are eventually consumed by larger fish. Human sources of atmospheric mercury include coal burning and mining (mercury and gold in particular).

Atmospheric exposures occur from outgassing from rock or through volcanic activity. Mercury exists in nature primarily as elemental mercury or as a sulfide and is found in the earth's crust at approximately 0.5 parts per million. Most human exposure to mercury is caused by outgassing of mercury from dental amalgam, ingestion of contaminated fish, or occupational exposure, according to the World Health Organization. It is available for compounding in the United States and is available over the counter in Germany. DMPS is considerably safer than penicillamine or British anti-Lewisite, as discussed hereinafter. The absorption of DMPS and DMSA by ingestion is highly variable from one patient to the next DMPS can be given intravenously, while DMSA cannot. Most of the authors cited hereinafter consider DMPS to be a stronger chelator than DMSA, with one exception citing evidence that DMSA is more effective at removing organic mercury. This paper is intended to review published data on these issues and to assess published clinical experience using DMPS to remove mercury from the human body. There is considerable controversy about the clinical significance of exposure to the various forms of mercury and some disagreement regarding techniques for clinical assessment of mercury burden. Low-grade chronic exposure to elemental or other forms of mercury induces subtler symptoms and clinical findings, as discussed hereinafter. Toxicity varies with dosage: large acute exposures to elemental mercury vapor induce severe pneumonitis, which in extreme cases can be fatal. Mercurous and mercuric salts chiefly damage the gut lining and kidney, while methyl mercury is widely distributed throughout the body. The target organ for inhaled mercury vapor is primarily the brain. Human toxicity varies with the form of mercury, the dose and the rate of exposure. Mercury salts, in contrast, tend to be insoluble, relatively stable, and poorly absorbed. Methyl mercury is easily absorbed through the gut and deposits in many tissues, but does not cross the blood-brain barrier as efficiently as elemental mercury however, on entering the brain it is progressively demethylated to elemental mercury. Inhaled elemental mercury vapor, for example, is easily absorbed through mucus membranes and the lung and rapidly oxidized to other forms (but not so quickly as to prevent considerable deposition of elemental mercury in the brain). There is some interconversion in vivo between the various forms of mercury. The biological behavior, pharmacokinetics, and clinical significance of the various forms of mercury vary with chemical structure. ++) or mercuric (Hg ++) salts and organic mercury, which includes compounds in which mercury is bonded to a structure containing carbon atoms (methyl, ethyl, phenyl, or similar groups). It exists in several forms: inorganic mercury, which includes metallic mercury and mercury vapor (Hg 0) and mercurous (Hg 2 The clinical impact of smaller mercury exposures remains controversial. Mercury is a heavy metal of known toxicity, noted for inducing public health disasters in Minamata Bay, Japan and in Iraq.

Castor oil for mercury poisoning