More than 200 years ago, hat making was a profitable business, but it could also be a deadly one!

The furs used to make felt hats were dipped in a preservative made with mercury nitrate solutions. The soaking also helped soften the animal hairs. Unfortunately, workers in the felt industry constantly absorbed mercury through their skin.

The resulting mercury poisoning exhibited as severe shaking and slurred speech, and this became known as the “Hatter’s Disease.” This condition is believed to have inspired Lewis Carroll to introduce the Mad Hatter character in his work Alice in Wonderland.

Mercury exists in three chemical forms: elemental mercury, methylmercury and mercury compounds. Each has a specific effect on human health.

In the modern world, the methylmercury form is the one that we most fear, is the most toxic and which has been reported extensively as the toxin that is present in many fish.

Because of industrial pollution in our rivers, lake and oceans with mercury-containing wastes from factories, fish absorb the elemental form and, through a biological process involving the bacteria present in fish, they transform elemental mercury into the more toxic compound known as methylmercury. It’s this toxic component that makes its way up the fish food chain and eventually to our dinner tables.

But there is an even more lethal form of mercury, dimethylmercury, a synthetic (man-made) compound. It’s used in the research industry as a reference material in certain chemical analysis procedures. Attaching an additional methyl group to methylmercury creates dimethylmercury, and this process transforms a toxic substance into a lethal one, making dimethylmercury an extremely potent neurotoxin.

So, it would seem that we’ve come full circle from the “Hatter’s Disease” of the past to another potentially lethal, present-day mercury toxin. Dimethymercury is part of the laboratory analysis process in some spectroscopy procedures and in 1996 a professor of chemistry at Dartmouth College, New Hampshire, was testing the effects of heavy metals on organisms.

She was using dimethylmercury as a reference material when she accidentally spilled a couple of drops of it onto the back of her gloved hand. Despite aggressive therapy, this laboratory worker exhibited severe neurological symptoms. Her condition deteriorated rapidly and she died less than eight months later.

Dimethylmercury is a colorless liquid at room temperature and has a faint sweet smell. It is rapidly absorbed through the skin and a lethal dose has been determined to be less than 0.1ml (about 1-2 drops). The chemical also is absorbed through most plastic and rubber glove materials, so extreme caution is required when handling dimethylmercury.

This chemical is also rapidly and completely absorbed through the GI and respiratory tracts. Since the chemical is highly vaporous (it begins to transform into a gas at warmer room temperatures), poisoning via inhalation or ingestion is especially lethal.

In the recent past, dimethylmercury has been used as the poison of choice in a couple of TV murder mysteries—and with good reason. It is stocked in several types of laboratories, is available for purchase on the Internet and is extremely lethal.

Dimethylmercury is said to be one of the most potent neurotoxins known to man because it readily crosses the blood-brain barrier by combining with the amino acid cysteine. After exposure via the skin, inhalation or ingestion, minute amounts of the chemical begin its slow kill process by affecting the immune system, altering the body’s enzyme systems and irrevocably damaging the nervous system.

The initial symptoms of exposure to this toxic chemical include abdominal pain, progressive and significant weight loss, loss of balance and slurred speech. There is eventual progression, after several months, to a vegetative state and death.

A single exposure to a couple of drops of the pure chemical will cause a person’s mercury level to soar to 80 times the toxic threshold. And aggressive therapies, such as heavy metal chelation, appear to be ineffective in stopping the progression to death.

So if your murder plot allows for a slow but dramatic advancement to death, this toxic chemical might be the perfect murder weapon. But be warned! Have your villain handle the product with heavy-duty neoprene gloves to prevent his or her accidental poisoning in the process.

Thoughts? Comments? I’d love to hear them!