When a raving 27-year-old man was committed to Hudson River State Hospital for the Insane in April of 1887, no one thought much of it.

But 12 days later, another man arrived at the door in much the same incoherent condition. When the men regained awareness and could be interrogated, it turned out that they worked in the same nearby rubber factory.

That summer, a third man was brought to the hospital, where he was described as “in a condition of great mental excitement, disturbing the neighborhood by loud noises and violent praying.” He, too, turned out to be a co-worker.

The chief of the Nervous Department at New York’s College of Physicians and Surgeons at the time was Frederick Peterson. He knew these three cases couldn’t be a coincidence, so he set out interrogating the workers on the nature of their jobs. As he suspected, the men had all inhaled a chemical in the factory’s air: carbon disulfide.

Peterson had heard of carbon-disulfide insanity in Europe, so he alerted his colleagues in The Boston Medical and Surgical Journal (now known as The New England Journal of Medicine) that the problem had come to America. In England, the new term “gassed” had arisen, defined in the Liverpool Daily Post as “the term used in the India rubber business, and it meant dazed.” The British physician Thomas Oliver had recalled watching as people working in rubber factories left after their shifts and “simply staggered home,” apart from themselves. The effect could be deadly. “Some of them have become the victims of acute insanity,” Oliver wrote, “and in their frenzy have precipitated themselves from the top rooms of the factory to the ground.”

* * *

Rubber as it naturally occurs is a mess. In hot weather, it melts. In cold, it cracks and shatters. It was almost useless to people until 1845, when chemists invented a way to make natural rubber into tires, called vulcanization.

In the ensuing years, a fierce competition to perfect the process erupted. The initial solution involved a mix of heating the natural rubber and adding sulfur. The product was pliable but durable, able to withstand most any weather. Vulcanization could be done in massive factories, like that of Goodyear. Shortly after, the British chemist Alexander Parkes figured out a way to forego the intensive heating and produce a superior rubber. Cold vulcanization instead used a solvent to treat the natural rubber: carbon disulfide.

It’s impossible to say how many people today have benefited from this discovery—billions of users of rubber products, from shoe soles to hoses to tires—while a lower but not insignificant number suffer because of it.

“Carbon disulfide is a very unique toxin—in its manifestations, truly protean,” the physician Paul Blanc told me. “And some of them are quite startling, most especially its capacity to cause insanity. But also atherosclerosis in the heart and the brain, as well as Parkinsonism.”

The CDC adds to that list birth defects and menstrual disturbances. But before you panic and starts discarding your tires, know that tires don’t contain carbon disulfide. Exposure to carbon disulfide comes in other ways, which Blanc has been at the forefront of elucidating. At the University of California San Francisco, he chairs the department of occupational and environmental medicine—a specialty largely concerned with tracing chemical exposures and relating them to human health. He spent the last eight years tracing carbon disulfide, including the stories above, and recently published his findings in an intensive history titled Fake Silk.

Apart from the mysterious effects of the molecule on human nerves and vessels, Blanc said, “the thing that sustained my interest was how everywhere I looked, the trail seemed to go out and intersect and combine in ways that fascinated me.”

Chinese firemen decontaminate the area around a truck leaking carbon disulfide.

The trail began with the explosion of vulcanization in France. Carbon disulfide is a colorless liquid that evaporates rapidly at room temperature. As of 1849, Blanc could only find the compound mentioned in a footnote of the reigning 600-page tome on applied industrial chemistry. By 1851, the updated edition of the book mentioned carbon disulfide on its title page. The author, a chemist of note named Anselme Payen, warned that cold vulcanization can be dangerous to workers on account of the vapors.

Two years later, Payen’s warnings were corroborated by physician Guillaume Duchenne de Boulogne (for whom a major form of muscular dystrophy is named). Duchenne published the first known report of the damage carbon disulfide can do to the nervous system. In a presentation to the Medical-Surgical Society of Paris, Duchenne said that carbon disulfide exposure among vulcanization workers seemed to cause disease “resembling general paresis of the insane,” or syphilis of the brain.

Evidence piled on in 1856, when a professor of medicine at the University of Paris named Auguste Delpech reported several cases of carbon disulfide poisoning to the French Academy of Medicine. The symptoms ranged from disturbing dreams to compromised memory to mania. The cases were so fascinating that he turned the focus of his career to carbon disulfide. In a medical newspaper, he told of a 27-year-old who, after just three months of working with carbon disulfide in the rubber industry, appeared prematurely aged and whose “sexual desire and erections were abolished.”

By 1863, Delpech had accrued enough case studies to write a 100-plus-page paper on the dangers of carbon disulfide, particularly among workers in balloon and condom factories. He observed two distinct phases of intoxication: a period of mental disturbance followed by disruptions of the distal nerves, causing weakness and numbness in the extremities. Hypersexuality gave way to impotence, bypassing the middle ground. Chronicling these effects put Delpech at the front of the emerging discipline of the science of the mind.

When he died in 1880, Delpech’s mantle was taken up by the famous French neurologist Jean-Martin Charcot. He popularized the notion that “hysteria” was a medical condition that combined physical complaints (sometimes as extreme as paralysis) with patterns of weakness that didn’t follow any known anatomic logic. It was Charcot’s influence in the late 19th century that made hysteria a firm medical fact in allopathic medicine—both among female and male patients.

* * *

The historian Mark Micale calls the final decades of the 19th century “the Belle Époque of hysteria.” The term had been recorded in text dating back to Plato and Hippocrates, and it was common in the Victorian era as a vague dismissal of most any symptom experienced by women, but its modern canonized form as a “scientific” entity happened in Paris. Diagnosing men with hysteria came into style, led by Charcot. And it was an equal-opportunity malady; during the 1880s, Charcot published more than 60 case histories of male “hysterics.”

It wasn’t that the behavior he described didn’t exist prior to the 1880s, Micale has explained. “It did exist. It was rampant. Men were as prone to nervous breakdown as women were. It was not diagnosed for social and political reasons. Men were believed to be more sane, more motivated by reason, more in control of themselves emotionally. If you were to diagnose it honestly, that would have pretty quickly called into the question the difference between the sexes and the idea that men were more self-possessed than their fragile, dependent female counterparts. Ultimately it came down to patriarchy and power.”

As the diagnosis came into use by doctors across Europe, the constellation of symptoms that had been for centuries attributed to an “inactive or ungratified uterus” now demanded plausible physiological explanations. Among doctors in the 19th century—all males at the time—the idea that men are too powerful to be overcome by flights of emotion did not sit well. Doctors sought a cause for the condition. This pointed some to carbon disulfide.

In one lecture in Paris, Charcot described a classic patient. The man had always been “sober and tranquil of manner.” He had worked in the rubber industry for 17 years, but only recently began manually cleaning the vulcanization vats that contained carbon disulfide. In the process, the man experienced an acute burning sensation in his scrotum—and then collapsed on the job, fully anesthetized. He was unconscious for half an hour and bedridden for two days, which were filled with nightmares and hallucinations of “terrible animals.” He did not recover fully, but remained weak and given to twitching. Charcot diagnosed the man with “toxic hysteria” secondary to carbon disulfide poisoning.

As the term hysteria faded from clinical relevance, the dangers of carbon disulfide did not. People exposed to carbon disulfide today are still at risk of disease. A 2014 study of an unnamed “rubber and plastic manufacturing plant” in New York found that workers exposed to carbon disulfide had more than twice the rate of fatal heart disease as did other workers at the plant.

Carbon disulfide is not limited to the rubber industry. It’s integral to the manufacturing of cellophane and rayon—the “fake silk” that gives name to Blanc’s book. These products are made of regenerated cellulose, which is synthesized using carbon disulfide. Rayon was a critical strategic material during WWII, and some of the most dramatic documentation of severe carbon-disulfide poisoning in workers was among slave laborers who manufactured rayon for the third reich. In one factory in Poland, a number were hospitalized as mental patients and then never heard from again.

Like handling vulcanized rubber, using cellophane or wearing rayon isn’t dangerous; the material is free of carbon disulfide by the time it hits shelves. The family of materials are called regenerated cellulose. Once you regenerate the cellulose, the carbon disulfide is gone. Cellophane involves the identical manufacturing process to rayon, except for the very last step, which yields a film instead of a thread. (Yet the cultural symbolism of cellophane has been entirely the opposite of rayon—modern and silly as opposed to cheap and tawdry. It always was. In the 1930s, a famous German novel called The Artificial Silk Girl told the story of a young woman who moved to Berlin and slept around, all the while loving nothing more than to wear rayon.)

“The current marketing avoids the term rayon,” Blanc explained. “They now go with viscose. People buy something that’s ‘30 percent viscose’ and they have no idea that it's the same thing as rayon.”

A model in a rayon blouse at a 2005 fashion show in New York
(John Smock / AP)

In agriculture over the years, carbon disulfide has been widely used to kill gophers and fumigate grains. No rayon is made in the U.S. currently, but cellophane (based in Tecumseh, Kansas, owned by Innovia), sponges, and sausage casings are. “Skinless” weenies are made by pushing meat into a tube of viscose rayon and then, after it hardens, peeling back the rayon.

Whether rayon or viscose, cellophane or sponges, products made with carbon disulfide can be an example of what health advocates call greenwashing. Cellulose is indeed a renewable and non-toxic material, and cellulose products are often positioned as green alternatives to petroleum-based or nylon products. “That's fairly disingenuous, to put it mildly—if a product was made using toxic chemicals,” said Blanc. “That makes the final product safe, but it doesn't mean it’s green.”

The process poses more than a threat to factory workers, but more subtly as an element of air pollution. A 2016 EPA report said that carbon disulfide levels in the air are 50 percent higher in urban areas than rural areas. The United States’ federal standards for carbon disulfide are “among the worst in the world—the most non-protective,” said Blanc. “Worse than China and Europe, comparable to India.”

States do have the authority to implement tougher standards, but only one routinely has: California. It follows the recommendations of the CDC; Blanc estimates these to be 20 times more protective than the federal standard (which chemical industry lobbyists have fought to maintain).

After unearthing and pouring through all these lessons from history, Blanc is more than uneasy (if not hysterical) about the prospects for carbon disulfide poisoning—both acute and low-level chronic exposures—under the Trump administration.

“Consumers shouldn’t just be worried about the Occupational Safety and Health Administration,” he added, “but about what will happen to the Consumer Product Safety Commission—which is the main agency dealing with post-marketing control of hazardous materials.” For example, the commission dealt with the importation of lead toys from China, and the exploding of smartphones. Some members have expressed concern that Trump and other Republicans will be in a position to “strangle the agency with inadequate funding, or tie the agency up in knots so it cannot adequately function.”

“And of course if you’re a factory in the United States that makes viscose products, you can stop worrying about your air pollution,” said Blanc. “In all likelihood.”