Mad Hatter Disease is also called erethism, erethismus mercurialis or mad hatter syndrome. Caused by progressive mercury poisoning it's a neurological disorder with symptoms of personality change, irritability, low self-confidence, apathy and tremors.
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With the New World fur trade, beaver hats are in demand. In his workshop, the hatter is given an oily, dirty beaver pelt with long guard hairs. Beneath these hairs is the delicate beaver wool, known as "duvet,". Fur fibers in natural state are not suitable for felting.
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Carroting is a meticulous procedure often done in advance. The hatter uses a knife or pliers to remove guard hairs, then applies a solution of mercury nitrate to the skin. This helps lift the scales from each wool fiber, causing them to straighten and turn reddish.
Hatmakers often work in enclosed spaces, increasing exposure to toxic mercury vapors. Hazardous working conditions faced by hatters during this era underscore the lack of awareness regarding the health risks associated with mercury exposure.
The use of mercury in hat making is introduced by Huguenots in 17th-century France, despite the known risks of mercury exposure at that time. This technique is initially kept as a trade secret in France, and hatting quickly becomes a lethal profession.
Toward the end of the 17th century, the Huguenots bring this secret to England. The fur trade in the New World drives demand for beaver hats. During the Victorian era, the health issues faced by hatters become well-known, but not well-addressed.
Sayings such as "mad as a hatter" come from mercury poisoning symptoms. In the 19th century, use of inorganic mercury, specifically mercuric nitrate, prevails in manufacture of felt for hats. Mad Hatter's disease is seen as an occupational hazard.
To make the felt, hairs are amalgamated or pressed together creating a compact mass of intermeshed fur fibers. The orange-colored solution containing mercuric nitrate acts as a smoothing agent during this process, contributing to the desired texture of the felt.
After the carroting stage, the felt undergoes further treatment by being shaped into large cones, then subjected to shrinking in boiling water, and finally dried.
Over time, a slow chemical reaction within the treated felts releases volatile free mercury. Consequently, hatters, or milliners, who are in direct contact with vapors emanating from the impregnated felt, were at significant risk of mercury poisoning.
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Erethism primarily affects the central nervous system, due to prolonged exposure to mercury vapors. This toxic exposure can cause behavioral changes which significantly impact daily life.
During Roman antiquity and through the Middle Ages of Europe, the cinnabar mines in Spain are a dreaded destination for slaves, social outcasts, criminals and war prisoners. A mercury ore, cinnabar is processed through distillation.
This releases toxic vapors. Both mining and processing cinnabar exposes workers to fumes and physical poisons . The evaporation of mercury even at room temperature causes deadly fumes. Mercury poisoning tends to happen in a processing environment.
Commonly observed symptoms include
irritability
low self-confidence
depression
nervous anxiety
apathy
shyness, timidity
slurred speech
delirium
personality changes
memory loss
Moreover, individuals suffering from erethism often find it challenging to engage in social interactions due to the cognitive and emotional disturbances caused by the condition.
The impact of erethism is not limited to behavioral changes; it also presents physical symptoms that can further debilitate the affected individual. These physical manifestations may include
reduced physical strength
persistent headaches
generalized pain throughout the body
tremors
irregular heartbeats
Symptoms can cause psychological problems. These compound the overall burden of the disease. Given the complexity of symptoms associated with erethism, it is crucial for individuals experiencing these signs to seek medical attention promptly.
Early diagnosis and intervention can help manage the condition effectively and prevent further deterioration of both the physical and mental health of the individual.
In 1869, the French Academy of Medicine demonstrates the health hazards posed to hatmakers. Alternatives to mercury use in hat-making are available by 1874. In the US a hydrochloride process patented in 1888 to phase out mercury is not used.
In 1898, laws are passed in France to protect hatmakers from mercury exposure. By the turn of the 20th century, mercury poisoning among British hatters is rare. In the US, the use of mercury continues until 1941.
Women hat-makers are less likely to be exposed as they work more in the areas of style and design than in processing. The term milliner is used for men's hatters until mid-18th century, when the term becomes exclusive to makers of women's hats.
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