A new cinematic version of Alice in Wonderland just hit movie theatres. When one thinks of this classic tale, workplace safety isn’t usually one of the themes that comes to mind. But maybe it should be. After all, the Mad Hatter may very well be a victim of a workplace illness—exposure to mercury.

Mercury & Mad Hatter’s Disease

According to a recent NIOSH backgrounder, the Mad Hatter’s erratic, agitated behavior refers to a real industrial hazard in Lewis Carroll’s Britain of 1865. Hatters or hat-makers commonly exhibited slurred speech, tremors, loss of coordination, memory loss, irritability, shyness, depression and other neurological symptoms—hence, the expression “mad as a hatter.”  This collection of symptoms became known as Mad Hatter Syndrome. 

The cause: chronic occupational exposure to mercury. Mercury is a neurotoxin—that is, a substance that damages, destroys and impairs the functioning of nerve tissue. Hatters toiled in poorly ventilated rooms, using hot solutions of mercuric nitrate to shape wool felt hats. In addition, they sealed their hats by licking the glue they used, which contained small but dangerous amounts of mercuric salt.

“Dancing Cat Disease”

Mercury is also a threat to the environment and human health in general. For example, people can be exposed to mercury by eating food—particularly fish—that has elevated methylmercury levels. The most infamous example of mercury poisoning occurred in Minimata, Japan in 1956. Industrial sewer discharges into Minimata Bay led to the build-up of toxic levels of methylmercury in local fish. Residents ate the contaminated fish and more than 1,000 people died as a result. This type of severe mercury poisoning is now called Minimata Disease. (Cats were, in fact, the first to show signs of poisoning, including uncontrollable muscle spasms and tremors that the locals called “dancing cat disease.”)

A Cautionary Tale

“Society has made great progress in recognizing and controlling industrial hazards since Lewis Carroll’s day. For example, nearly 70 years ago, on December 1, 1941, the U.S. Public Health Service ended mercury’s use by hat manufacturers in 26 states through mutual agreements. The kinds of conditions that put hat-makers and other industrial workers at risk in 1865 are no longer tolerated,” said John Howard, M.D., Director of the NIOSH.

“However,” Dr. Howard emphasized, “the Hatter remains a cautionary figure, since exposures to mercury and other hazardous industrial substances can still occur in the workplace. Symptoms from chronic exposures to mercury, lead, and other neurotoxic substances, even at low levels, may be subtle in early stages. Sometimes, they may be mistaken for symptoms that can arise from other causes. Similar concerns exist about other adverse effects that are associated with exposures on the job. It is important to be vigilant about work-related illness, and to act decisively to protect workers’ health.”