Mercury in any form is poisonous. Mercury is a most dangerous heavy metal to human second only to uranium. In clinical practice very seldom toxic level of uranium detected but toxic level of mercury is very prevalent. Study on polar bear in north-pole indicates toxic level of mercury due to food chain through migratory birds that feeding on sea-food. Environmental exposure usually coming from sea-food especially fish and amalgam tooth filling. Three teeth filling with amalgam (contain 51% mercury), mercury in the stool generally detected forty times higher than allowable level by WHO.
Poisoning can result from mercury vapor inhalation, mercury ingestion, mercury injection, and absorption of mercury through the skin.
Mercury toxicity most commonly affecting the neurologic, gastrointestinal and renal organ systems. Half-life of mercury in the brain is estimated to be about 25 years.
Heart muscle analysis in those who died of myocardial infarction usually contains five or more times higher mercury level than non-heart related death. In cardiomyopathy, the level of mercury in heart muscle can be higher by thousands of times. Breast cancer tissue generally much higher mercury level than in fibro-adenoma cases.
Virtually mercury can cause all kind of symptoms especially nerve and cognitive symptoms (but not all symptoms can be caused by mercury)
The most deadly form of mercury is methylmercury where 90% of any methylmercury ingested is absorbed into the bloodstream from the GastroIntestinal tract.