The Mad Hatter Syndrome

A Quick Review of Mercury Poisoning



  • Most human exposure results from fish consumption, dental amalgam, or occupational exposure.
  • Approximately 80% of metallic mercury vapor outgassed from amalgams is absorbed through inhalation, compared with about 7 to 10% absorption of ingested metallic mercury, and about 1% absorption of metallic mercury through skin

Important Elemental Forms:

  • Mercury vapor: Most toxic form. Transported to the brain, either dissolved in serum or adherent to red cell membranes.
  • Metallic mercury: Passes easily through the blood brain barrier and through the placenta. Rapidly oxidized, although not so quickly as to prevent considerable uptake by the central nervous system


  • Poisons cellular function by altering the tertiary and quaternary structure of proteins and by binding with sulfhydryl and selenohydryl groups.
  • The chief target is the brain, but peripheral nerve function, renal function, immune function, endocrine and muscle function, and dermatitis.


  • Low-level exposures: nonspecific symptoms like weakness, fatigue, anorexia, weight loss, and gastrointestinal disturbance
  • Higher exposure levels:
    • Pneumonitis
    • Mercurial tremor: fine muscle fasciculations punctuated every few minutes by coarse shaking.
    • Erethism: severe behavior and personality changes, emotional excitability, loss of memory, insomnia, depression, fatigue
    • Acute myocardial infarction, carotid atherosclerosis


  • Blood and urine levels correlate fairly well to each other, but not to total body burden
  • It has not been possible to set a level for mercury in blood or urine below which mercury related symptoms will not occur.

Treatment: Chelation!

  • DMPS: increases in urinary mercury output; evidence of decreased body burden
  • Safer than British Anti-Lewisite and more potent than DMSA