Bacteria in bodies of water cause changes that turn mercury into organic methyl mercury, which gets consumed by fish. Human exposure to mercury can come from ingesting the contaminated fish or breathing contaminated air, in addition to amalgam used in dental fillings that can contain up to 54 percent elemental mercury.
Over time, mercury can accumulate in our brain, kidneys, liver, gastrointestinal tract and lungs. Mercury vapor crosses the blood-brain barrier and damage brain cells and can be difficult to diagnose.
Elemental mercury is eliminated in feces, urine, expired air, sweat, saliva and breast milk. Exposure to broken thermometers, old paint, mirror coatings and dental amalgam are sources of inorganic toxicity.
Prior to 1991, phenylmercuric compounds were used in 30 percent of latex paints. Use of these paints resulted in human exposure to elemental mercury vapors in their homes.
Although amalgam dental fillings release mercury mainly through mechanical wear and evaporation, the risk of exposure is usually only considered significant with greater than six to eight fillings.
People who have larger numbers of dental amalgams installed or replaced at one time will exhibit transient increases in blood and urine mercury levels.
Excessive elemental mercury vapor exposure -- particularly to dentists and dental technicians when amalgams are being prepared or dental fillings removed -- might cause memory loss, intellectual decline, irritability, depression, anxiety, loss of self confidence, insomnia, excessive salivation, foul breath, metallic taste in the mouth, inflamed gums, diarrhea, blood pressure changes, cough and irregular breathing.
Inorganic mercury salts have been found in creams for skin lightening and other products like fungicides, mercurochrome and thimerosal (preservative containing mercury in some over-the-counter and prescription medications). Mercuric sulfide is found in red tattoo dyes.
Methyl mercury accumulates in fish as it passes over their gills as they swim in mercury-contaminated waters. We eat the contaminated fish and ingest the mercury. Methyl mercury concentration in sport fish can be higher than in commercial fish purchased at grocery stores.
Interestingly, cooking doesn't alter the amount of methyl mercury in the fish. Except for contaminated fish, human intake of dietary mercury is negligible.
Methyl mercury inhibits acetylcholine, a transmitter of nerve impulses, synthesis resulting in memory loss and other toxicity symptoms. Early signs and symptoms of true poisoning include decreased senses of touch, hearing, vision and taste, metallic taste in the mouth, fatigue or lack of physical endurance and increased salivation.
Symptoms can progress with chronic exposure to include anorexia, numbness of the extremities, headaches, high blood pressure, irritability and excitability and immune suppression. Advanced disease might include tremors, incoordination, anemia, psychoses, manic behaviors and kidney problems.
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