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NIOSH Backgrounder: Alice’s Mad Hatter & Work-Related Illness


NIOSH Update:

Contact: Fred Blosser, (202) 245-0645
March 4, 2010

Tim Burton’s new movie version of Alice in Wonderland opens in theaters tomorrow, starring Johnny Depp as the Mad Hatter.

The Hatter’s erratic, agitated behavior in the classic story refers to a real industrial hazard in Lewis Carroll’s Britain of 1865. Hatters or hat-makers commonly exhibited slurred speech, tremors, irritability, shyness, depression, and other neurological symptoms; hence the expression “mad as a hatter.” The symptoms were associated with chronic occupational exposure to mercury. Hatters toiled in poorly ventilated rooms, using hot solutions of mercuric nitrate to shape wool felt hats.

In a Dec. 24, 2009, interview with the Los Angeles Times, Johnny Depp is quoted as saying that he was aware of the implications of the Hatter’s behavior: “I think [the Mad Hatter] was poisoned – very, very poisoned. And I think it just took [e]ffect in all his nerves. It was coming out through his hair and through his fingernails, through his eyes.” In the new movie, Depp’s Hatter has flamboyantly red hair. This presumably reflects the character’s chronic exposure to an orange-colored solution containing mercuric nitrate that was used in a process called “carroting.”

“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 National Institute for Occupational Safety and Health (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.”

NIOSH is the federal agency that conducts research and makes recommendations to prevent work-related illness, injury, and death. It recommends that employers, workers, and health providers use the following precautions:

  • Always be aware of the hazards that may be posed by given substances that are produced, used, or occur on the job.
  • Follow applicable regulations, guidelines, or practices to control exposures.
  • Know the symptoms of work-related illnesses, and follow appropriate treatment.
  • Prevent “take-home contamination” that may endanger family members and loved ones. This situation can occur when potentially hazardous dust, residue, or particles are inadvertently tracked home on the worker’s skin or clothes.

NIOSH collaborates with partners and stakeholders to develop effective exposure limits for potential workplace hazards, devise practical control measures, and work toward the elimination of persistent hazards in traditional industries. NIOSH also conducts pioneering research to anticipate potential risks from emerging technologies, and to help improve surveillance for work-related illnesses. More information about NIOSH can be found at

Mercury and Occupational Health Risk

Mercury is used in many industries, including use as a liquid cathode in electrolytic production of chlorine and caustic soda from brine; manufacture and repair of industrial and medical apparatus; fluorescent lights (proper recycling of fluorescent lights is important for preventing occupational and environmental exposures) ; during manufacture of inorganic and organic compounds for use as pesticides, antiseptics, germicides, and skin preparations, use in preparation of amalgams for use in tooth restorations, chemical processing, molding operations; and various other processes.

Metallic mercury readily vaporizes at room temperatures, and the vapor has no warning properties. At low levels, the onset of symptoms resulting from chronic exposure is insidious; fine tremors of the hand, eyelids, lips, and tongue are often the presenting complaint.

National data for job-related mercury poisoning are elusive

  • In 2008, 770 cases of work-related poisoning from all types of “metallic particulates, trace elements, dusts, powders, and fumes” resulted in at least one day away from the job for the worker, according to U.S. Bureau of Labor Statistics figures.
  • The 2008 Annual Report of the American Association of Poison Control Centers indicates “casescalls” for mercury thermometer cleanup (4,195 cases), and mercury (excluding thermometers) cleanup (3,842 cases); however, the report does not specify occupational or non-occupational attribution for the cases.
  • The New York State Heavy Metals Registry for 2000-2005 reported 7,952 adults with elevated levels of mercury in their blood. 63 cases were attributed to occupational exposures, 1,889 to non-occupational exposures, 25 to both kinds of exposures, and 5,975 in which the cause was unknown.

NIOSH provides recommendations, reports, and other resources for preventing hazardous exposures to mercury on the job. These can be found at