Mad as a Hatter – The Environmental Ramifications of the Historical Hatting Industry

By: Taryn Ramey

When people hear the phrase “mad as a hatter,” they often think of Lewis Carroll’s novel (or perhaps the animated movie) Alice’s Adventures in Wonderland. While exploring Wonderland, Alice meets the Cheshire Cat. “What sort of people live about here?” she asks.[1] The cat replies, “in that direction lives a Hatter, and in that direction, lives a March Hare. Visit either you like: they’re both mad!”[2] Later, Alice stumbles upon a strange little man donning an oversized top hat while drinking tea with the March Hare and the Dormouse.[3] The Hatter is characterized by erratically switching places at the table; making short, odd remarks; asking nonsensical riddles, and reciting strange poetry.[4] Carroll’s portrayal of the Mad Hatter is not merely an idea pulled out of a hat – he’s styled after the laborers in the hatting industry who suffered from mercury poisoning, which produces symptoms similar to insanity.

The triumphs and tribulations of the hatting industry are not exactly a “hot topic” in 2021. The age of donning a hat for every important social and formal occasion rapidly declined in the 1920s and was essentially extinct following the Second World War.[5] However, nearly 100 years later, the effects of the hat-making industry are still felt in the waterways situated adjacent to these historical factories and is an important example of why strong environmental protection regulations are imperative to ensure a clean and safe future.

Danbury, Connecticut was considered to be the hat-making city of the world.[6] By 1800, Danbury was producing nearly 20,000 hats annually – more than any other city in the U.S.[7] By 1859, this number rose to 1.5 million annually and by 1887, thirty factories were producing 5 million hats per year.[8] Danbury produced 24% of America’s hats in 1904 and supplied the industry with 75% of its hat bodies.[9] Traditional hat-making involved the use of mercury nitrate in the felting process.[10] Workers were chronically exposed and suffered the painful effects of mercury poisoning. It was such a common ailment that it was known as the “mad hatter’s disease” or the “Danbury Shakes” – named for the nervous tremors the workers experienced as a symptom of their exposure.[11] As abovementioned, the hatting industry steadily declined, and the city’s last major hat factory closed in 1964.[12] Nowadays, there are various reminders of the once-dominating industry all over town, but there is one scar from the hatting industry that has yet to heal.

The small amounts of mercury vapor or solution that the workers inhaled or ingested were minuscule compared to the tons of mercury and other substances routinely dumped directly into the Still River, a tributary of the Housatonic that flows through Danbury and eventually empties into the Long Island Sound.[13] The hatting industry existed in Danbury for over 150 years – it is nearly impossible to quantify the amount of mercury that was dumped into the Still River during that period.[14] Though Connecticut banned the use of mercury in 1940 and factories largely phased out its use before then, there is both empirical and anecdotal evidence of unused mercury supplies being dumped into the Still River as hat factory closings accelerated in the 1950s and ‘60s.[15]

Mercury exposure at high levels poses a significant danger for both humans and the environment. Nowadays, human and animal exposure is almost entirely through eating contaminated fish and wildlife that are at the top of aquatic food chains.[16] The increased exposure can harm the brain, heart, kidneys, lungs, and immune system in people of all ages.[17] Exposure in utero may impact a developing child’s nervous system, affecting their ability to think and learn.[18] Similarly, high levels of mercury exposure can cause abnormal behavior, slower growth and development, reduced reproduction, or even death in birds and mammals.[19]

The sediments that line the bottom of the Still River contain the history of Danbury’s industrial past. Studies from 2003 found mercury levels that range from 1-60 parts-per-million (ppm) – significantly greater than samples found elsewhere in Connecticut of 2-5ppm and the natural background amount of 0.5-1ppm.[20] A 2020 study of fish tissue revealed that “fish muscle tissue from six out of seven of the sites had concentrations that exceed EPA guidance levels for weekly mercury consumption…”.[21] Given the fact that the fish sampled are only about three inches in size, the fact that they are accumulating so much mercury is surprising.[22] Sediments from the Still River sites which previously hosted hatting factories also have mercury concentrations exceeding background levels of mercury found in other Connecticut sediments.[23] These sediments and the pollutants they carry still find their way, via the Housatonic, to the Long Island Sound. Trying to dredge the sediment may only free more of it to head downstream.[24] Studies are being conducted to determine whether it is best to attempt to remediate or to just let it be.[25]

The Still River is a perfect example of why environmental protection is so imperative. As of 2021, the Still River is largely neither fishable nor swimmable.[26] The hatting industry has been gone for well over 50 years and mercury has been banned for even longer, yet remnants of industry’s careless environmental practices still lurk within the Danbury waterways today. Due to the environmental concerns relating to dredging the riverbed, there is no indication that Danbury’s mercury issue will be resolved soon. That being said, the Still River is not a lost cause by any means. At one time, the river was considered to be “dead” because it was devoid of both plant and aquatic life.[27] Thanks to local organizations interested in preserving the Still River and its watershed, small fish and plant life have returned to the river and the water appears to be clean.[28] Students often take field trips to learn about the river and its history – an important way to instill environmental values in the next generation.[29]

With the mounting threat of climate change, environmental protection is more important than ever. The Still River is a reminder that pollution does not exist in a vacuum – today’s actions impact tomorrow’s inhabitants.

Image from UConnToday

[1] Lewis Carroll, Alice’s Adventures in Wonderland 90 (BookVirtual Corp. 2000) (1865).

[2] Id.

[3] Id. at 94.

[4] Id. at 94-104.

[5] John Pirro, The rise – and fall – of hatting in Danbury, newstimes (Feb. 1, 2011),

[6] Shirley T. Wajda, Ending the Danbury Shakes: A Story of Worker’s Rights and Corporate Responsibility, (Dec. 12, 2020),

[7] U.S. Dep’t. of the Interior, National Register of Historic Places Inventory – Nomination Form, FHR-8-300 (1982),

[8] Pirro, supra note 5.

[9] Id.

[10] See Wajda, supra note 6 (describing the process by which mercury is used to separate the fur from the animal pelt in the felting process).

[11] Id.

[12] William E. Devlin & Herbert F. Janick, Danbury’s Third Century: From Urban Status to Tri-Centennial 229-41 (Western Ct. State Univ., 2013).

[13] See Daniel P. Jones, Mad Hatters’ Legacy, Hartford Courant (Sept. 22, 2002),

[14] What is traditionally considered to be the first hat shop in Danbury was established in 1780, though hat making had existed in Danbury since before the Revolution. See Wajda, supra note 6.

[15] Housatonic Valley Ass’n with Still River Partners, Still River Watershed Management Plan 37 (2019),

[16] U.S. Dep’t of the Interior, Mercury in the Environment (2000),

[17] EPA, Basic Information About Mercury (last accessed Jan. 25, 2021),

[18] Id.

[19] EPA, supra note 17; See generally Kevin M. Rice et al., Environmental Mercury and Its Toxic Effects, 47 J. Prev. Med. Pub. Health74 (2014).

[20] Housatonic Valley Ass’n, supra note 15, at 29.

[21] See Mercury remains a persistent poison in Connecticut’s Still River, ScienceDaily (July 23, 2020),

[22] Id.

[23] Id.

[24] Robert Miller, Still River cleanup continues, ctpost (Aug. 21, 2011),

[25] Id.

[26] Housatonic Valley Ass’n, supra note 15, at 11.

[27] The Still River also experienced other avenues of pollution contributing to its condition, including its use as an open sewer in the 18th and 19th centuries – this article only focuses on the presence of mercury resulting from historical industrial processes. See Miller, supra note 24.

[28] Id.

[29] Id.

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