Health and Safety Factors
Mercury has long been known to be toxic; the phrase "mad as a hatter" refers to the 19th-century occupational disease that resulted from prolonged contact with the mercury used in the manufacture of felt hats. Some workers today, especially laboratory technicians, nurses, and machine operators, continue to be exposed to mercury on the job.
Exposure typically comes from inhaling mercury vapors. For most of us, fluorescent lamps present the single greatest risk of mercury exposure in the work place. A study of exposure to broken "low mercury" lamps by the New Jersey Department of Environmental Protection entitled "Release of Mercury from Broken Fluorescent Bulbs" demonstrated that "elevated airborne levels of mercury could exist in the vicinity of recently broken lamps, and "could exceed occupational exposure limits."
Mercury & Human Health
The most common human exposure to methylmercury is through consumption of contaminated fish or animals that eat fish. Minamata disease was named after the occurrence, in the 1950s and 1960s in Minamata, Japan, of many cases of severe mercury poisoning. It was found that a chemicals factory was discharging mercury-containing wastes into the local waters, contaminating fish that residents caught for food.
Women who expect to become pregnant or are pregnant should not eat mercury-contaminated fish. Mercury affects brain and nervous system development in the fetus. Affected children show lowered intelligence, impaired hearing and poor coordination. Their verbal and motor skills may be delayed.
Mercury poisoning can cause severe neurological and kidney damage. Acute exposure can affect the respiratory and gastrointestinal systems. Organic mercury can cross the blood-brain barrier and cause irreversible nervous system and brain damage, e.g., loss of motor control, tingling sensations in the fingers and toes, numbness in limbs and around the mouth, tunnel vision or blindness, and loss of ability to speak. Long-term exposure to mercury can result in symptoms that get progressively worse and lead to personality changes, stupor and coma. Mercury poisoning can be confirmed by urine tests. Chelation therapy is used for poisoning with elemental mercury and mercury salts; there is no treatment for organic mercury poisoning.