Mercury exposure can cause neurological and developmental disorders in humans. Young and unborn children are at greatest risk from mercury exposure because their nervous systems are still developing. High-level exposures can cause severe birth defects, including blindness, deafness, cerebral palsy and mental retardation, and can even result in death. In low doses, mercury may delay a child's walking and talking, shorten attention span and cause learning disabilities.

In adults mercury poisoning can cause problems with fertility and blood pressure. Early symptoms of mercury poisoning include insomnia, lack of appetite, irritability, reduced peripheral vision, pins and needles feelings, numbness, loss of coordination, slowed reaction times, memory loss and slurred speech. Short-term exposure (hours) to high levels of mercury vapor can irritate lungs and airways, cause tightness of the chest, a burning sensation in the lungs and coughing. Other symptoms of mercury exposure include nausea, vomiting, diarrhea, skin rashes and eye irritation.

The most common route of exposure for humans is from eating mercury contaminated fish or, in the case of fetuses and nursing babies, from consumption of contaminated fish by the mother. Inhalation of mercury vapors is another route of exposure. There have been a number of recent accidental and deliberate releases of elemental mercury in schools, homes and other buildings. Mercury almost immediately begins to evaporate at room temperature. The speed it evaporates is usually slow, however, it also depends how much it is moved or disturbed.  Breathing the vapors can cause mercury poisoning. When inhaled, about 80 percent of the mercury enters the bloodstream directly from lungs, and then is rapidly spread to the brain and kidneys. Mercury can stay in the body for weeks or months.

The human health effects of mercury poisoning were revealed in a number of rare incidents over the past 50 years:

  • In 1956 the people of Minamata Japan, became seriously ill or died after eating fish and shellfish contaminated with extremely high levels of mercury. The pollution was traced to a chemical plant that was dumping methylmercury contaminated waste into the local bay. High percentages of severe birth defects appeared in children born to people who ate the contaminated fish. Kumamoto University estimates that 35,000 people were affected by this pollution.
  • In 1971, people in Iraq ate flour that was treated with a methylmercury fungicide. The seed was intended for planting rather than human consumption. Citizens were unaware that it was poisonous. More than 400 people died and about 6,500 were hospitalized with mercury poisoning.
  • In 1969, a pulp and paper mill in Ontario contaminated the English-Wabigoon watershed and threatened the health and livelihood of native people living in those areas. The plant is now closed but mercury levels remain dangerously high in some fish species in the area.

For further information on health effects, check out the following websites:

Return to main mercury page