Quicksilver Can Cure, but It Can Also Kill Insidiously
Mercury is one of the oldest and deadliest poisons, a highly toxic metal mined from a brilliant red ore, with powers that have enticed scientists for centuries.
It can cure and it can kill.
The ancient Egyptians and Chinese used mercury as a skin pigment. The Greeks used it as medicine. Until the mid-20th century, mercury salts were considered the main cure for syphilis.
Its toxic effects on workers in the hat factories in England in the 19th century, where mercury was used as a cleaning agent, gave rise to the term “mad hatter.”
Today, most of the world’s mercury is mined in Spain. Its usefulness is limited by its poisonous nature and its scarcity.
There are three main forms:
* Elemental mercury is the silvery liquid used in thermometers, thermostats, barometers and batteries--and by experimenting students in chemistry class. It also is used in folk medicine and in some religious practices. It vaporizes quickly when heated and is toxic only in its vaporized form.
* Inorganic mercury salts are used as antiseptic creams and ointments. One of the most commonly used mercury salts is calomel, a white powder employed in electrochemistry. For years, it also was used as a teething powder for infants until it was discontinued in the 1940s.
* Organic mercury compounds, such as dimethylmercury and methylmercury, are sometimes used as fungicides and herbicides, and are by far the most dangerous forms. Unlike elemental mercury, they readily can be absorbed by the body and signs of poisoning take an insidiously long time to appear.
Dimethylmercury, which killed scientist Karen Wetterhahn at Dartmouth College this year, is produced in small quantities purely for research. There is only one other documented case of dimethylmercury poisoning this century--a Czech chemist who died in 1972.
For all its ancient history, serious research on the poisonous powers of quicksilver is fairly recent.
It began in Sweden in the 1960s, when scientists first discovered how methylmercury, which is produced by small organisms in water and soil, can build up in fish and get passed on to humans.
The 1950s poisoning epidemic in Minamata Bay in Japan was caused by mercury-contaminated fish. Another outbreak occurred in Iraq in the 1970s when thousands of people were poisoned by bread made from grain treated with a methylmercury fungicide. About 500 people died and 6,000 were hospitalized.
Scientists admit they still have a lot to learn about mercury, particularly dimethylmercury.
They still don’t understand, for example, why symptoms take so long to appear. Mercury can be removed from the body with other chemicals if it is detected early enough. The horror of dimethylmercury is that the damage is irreversible before the symptoms show.
“That is what makes this field so insidious,” said Thomas Clarkson, who runs a mercury laboratory at the University of Rochester in New York and is considered one of the world’s experts on the subject. “A chemical horror can occur to someone taking all the precautions and, for months, we just don’t know.”
