5.1 The myth, reality, and history of mercury toxicity

Mercury has a reputation for being a dangerous element, but is its reputation deserved? Given the large-scale use of mercury today it is important to understand the risks and issues related to mercury exposure. Nowhere is this now important than with the use of mercury for small low energy fluorescent lights ( [link] ) that are being advocated by everyone from the electricity companies to Greenpeace.

When considering the issue of mercury toxicity it is important to separate the effects of mercury metal (as a liquid or vapor) from the compounds of mercury.

Mercury metal

It was found very early on that people who worked with mercury, in mining for example, had very bad health. Other jobs that exposed people to mercury were mirror makers and hatters (people who manufactured hats). The problems in this latter occupation will forever live on with one of the central characters in Lewis Carroll's Alice’s Adventures in Wonderland ; the Mad Hatter.

Hats were made from felt, which is a non-woven textile of animal hair. Wool interlocks naturally due to the surface texture of the individual hairs, but rabbit and beaver have to be artificially roughened. This process was usually accomplished with nitric acid (HNO ₃ ). It was found that if mercury was added to the nitric acid, a better quality of felt was produced. Unfortunately, when the felt was dried a fine dust was formed containing mercury. The hatters who shaped the felt inhaled large quantities of this dust were found to suffer from excessive salivation, erethism (presenting with excessive shyness, timidity and social phobia), and shaking of the limbs, which became known as hatter’s shakes . The madness that was observed is the derivation of the phrase “mad as a hatter”.

Hatters were not the only people that mercury caused a problem for. Chemists doing research using large quantities of mercury were also affected. They were given to violent headaches, tremors of the hands, “socially troublesome inflammation of the bladder”, loss of memory, and slow mental processes. In 1926 Alfred Stock ( [link] ) and his research group all suffered from symptoms. However, when the lab was cleaned of mercury the symptoms went away.

Many other notable scientists have also suffered from mercury poisoning. Faraday ( [link] ), Pascal ( [link] ), and most probably Sir Isaac Newton ( [link] ) were affected. As part of his research studies, Newton boiled several pounds of mercury a day just before his period of insanity between 1692 and 1693. It is likely that the mercury vapor was the cause of his malady. However, in each case, the symptoms (and insanity) abated once the source of mercury was removed.