The Smell of Hell

The episode opens with Molly Webster and Mack Kielty presenting a live Radiolab performance from Boston’s WBUR CitySpace. The subject is sulfur, an element commonly associated with rotten eggs, decay, hell, and generally “disgusting gross awful smelly things.” Avir Mitra, an emergency-room doctor and Radiolab correspondent, says the show will argue that sulfur is not merely repulsive: it may be essential to life. The audience is given scented blotter strips and asked to smell several sulfur-related odors during the performance. The first smell is described as pungent garlic. Mitra explains that sulfur compounds are responsible for much of garlic’s sharpness, and that sulfur is unusually important to the human sense of danger. Humans can detect some sulfur compounds at concentrations as low as 0.5 parts per billion—likened to picking out four people from a crowd of eight billion. That sensitivity evolved because sulfur often signals rot, decay, or a dangerous gas leak. Natural gas itself is odorless, so sulfur compounds are added to it as an alarm. The episode’s central question is whether that alarm has caused people to misunderstand sulfur, which may be less the “smell of hell” than the “smell of life.”

Mitra tells the story of Gloria Ramirez, a 31-year-old mother of two who arrived at a Riverside, California, emergency room on February 19, 1994. Ramirez had recently been diagnosed with metastatic cancer and came in delirious, sweaty, and critically ill. While staff treated her with oxygen, defibrillation, and other emergency measures, a nurse drawing her blood suddenly passed out. A resident holding the blood sample felt burning in her face, tingling skin, nausea, and lightheadedness before also collapsing. The respiratory therapist treating Ramirez then became unconscious. Within minutes, 23 of the 37 people in the emergency room reported nausea, tingling, burning skin, or fainting. Six medical workers were hospitalized, and the emergency room was evacuated to the parking lot while a hazmat team searched for a gas leak, carbon monoxide, or another environmental toxin. Nothing was found. Ramirez died that night of kidney failure, which did not explain the workers’ symptoms. California investigators eventually concluded that the incident was probably mass hysteria, citing stress, skipped meal breaks, and the fact that many of those affected were women. The hospital staff and Ramirez’s family rejected that explanation. A second autopsy at Livermore Laboratories found unusually high levels of dimethyl sulfone, or DMSO2, in Ramirez’s tissues. Investigators proposed that she had used DMSO, a degreaser sometimes applied off-label for pain, and that oxygen, energy from defibrillation, and contact with her blood might have transformed it into toxic dimethyl sulfate. But the chemistry had never been demonstrated in a living human, and Ramirez’s family denied she had used DMSO, so the cause remains unresolved.

Although the Riverside case remains disputed, the medical staff did agree that Ramirez’s room smelled strongly of garlic. Mitra connects that odor to sulfur compounds. He presents the smell as evidence that some unusual chemical event may have occurred, but also as support for the California investigators’ mass-hysteria theory: a strange, alarming odor could have triggered fear and symptoms that spread through an already stressed emergency-room staff. The episode emphasizes that sulfur’s reputation is grounded in biology. When bacteria consume a dead body, they produce sulfur compounds, linking the element to rot and death. “Brimstone,” the traditional symbol of hell, is simply an old term for sulfur. Yet the same sensitivity that warns people about decay or a gas leak also reflects sulfur’s ubiquity in living systems. Sulfur appears in amino acids and proteins, helps determine the shape of hair, participates in turning genes on and off, and helps molecules protect cells from breaking down too quickly. The live audience’s smell experiment therefore works as a reversal: a scent that feels like a warning of death may also point toward one of the basic chemical ingredients of life.

Historian and author Jennet Conant joins the performance to discuss the Bari disaster of December 2, 1943. Bari was a major Italian harbor on the Adriatic and a staging area for the Allied invasion of France, crowded with British and American ships carrying ammunition, weapons, and fuel. German planes bombed the harbor, sinking at least 17 ships and killing about 1,000 sailors while wounding roughly as many. The press called it “the little Pearl Harbor.” The disaster became even worse over the next several days. Sailors pulled from the burning water developed enormous blisters, swollen-shut eyes, nausea, vomiting, blindness, and extreme pain. Twelve men died within 12 to 48 hours, and hundreds more suffered. Lieutenant Colonel Stuart Alexander, an American chemical-warfare doctor, noticed a garlic odor and suspected mustard gas, although British officials denied that any mustard gas was present in the harbor. By mapping casualties and ship locations, Alexander identified the American Liberty ship John Harvey as the contamination’s epicenter. A diver found fragments of American sulfur-mustard bombs, confirming that the Allies’ own secret cargo had exploded. The sailors’ rescuers had unknowingly wrapped them in blankets, trapping mustard and oil against their skin and increasing the poisoning. Alexander’s autopsies showed that mustard gas had destroyed bone marrow, lymph nodes, and white blood cells. He wondered whether a small, controlled dose could destroy malignant white blood cells in leukemia. His classified findings joined secret Yale experiments using nitrogen mustard—a chemical cousin in which nitrogen replaces sulfur—that temporarily shrank lymphoma tumors. Although the patients relapsed and died, this work helped launch the use of toxic chemicals against cancer and paved the way for modern chemotherapy. Conant notes that Cornelius “Dusty” Rhodes, who promoted the research, was also a profoundly racist figure.

The final story concerns hydrogen sulfide, the swampy, sewer-like smell associated with low tide, the Jersey Turnpike, sewers, and oil drilling. At high concentrations it can kill. In 1989, a scientist named Werenitzia exposed rats to toxic levels of the gas, dissected their brains, and found hydrogen sulfide there. He also found small amounts in unexposed control rats. For roughly a decade, researchers treated this as accidental “brainfarts”—ordinary metabolic exhaust from a hard-working organ. Japanese scientist Hideo Kumura rejected that explanation. Studying neurons in mice, he found that repeatedly activated neural pathways produced more hydrogen sulfide, which then strengthened those same connections, much as a frequently used hiking trail becomes a paved road. Researcher Bindu Paul created mice unable to produce hydrogen sulfide and found that they failed to improve in a maze: every attempt seemed like the first. The result resembled a memory disorder. In another experiment, mice with an Alzheimer’s-like condition were exposed to hydrogen sulfide and performed almost as well as normal mice; their learning and memory deficits were prevented or reversed. The work remains limited to mice, not human treatment. The episode also mentions Rotorua, New Zealand, a town rich in naturally occurring hydrogen sulfide, where residents performed better than the general population on finger-tapping tests used to screen for conditions such as Parkinson’s. Garlic, broccoli, and shiitake mushrooms contain sulfur compounds that the body can use to make hydrogen sulfide, so Mitra’s practical suggestion is mushroom-and-garlic pizza—not a medical prescription, but a joke grounded in the chemistry being discussed.

To explain why the brain might use a toxic gas, the episode turns to evolution. Bindu Paul describes hydrogen sulfide as an ancient process retained from a time before Earth’s atmosphere contained much oxygen. About three billion years ago, sulfur emerged from volcanic activity and from deep-sea vents. Simple microbes living near those vents used sulfur as an energy source, and those environments may have been among the origins of life. When oxygen later transformed the planet, sulfur did not disappear. Because it was already biologically useful, it became incorporated into complex cells, amino acids, proteins, and regulatory molecules. The episode argues that sulfur is found in nearly every form of life on Earth. Its apparent contradiction—poisonous in one concentration and essential in another—recurs throughout the stories: mustard gas harms the body but helped reveal a route to chemotherapy; hydrogen sulfide can kill but may support memory; a sulfur odor can signal danger but also come from living organisms. The closing speculation reaches beyond Earth. Astrophysicists are using the James Webb Space Telescope to look for faint sulfur signatures far away in the universe, because sulfur could be a clue that life exists elsewhere. The hosts therefore reverse the episode’s opening association: when someone smells rotten eggs, decay, or sulfur in a park or city street, the smell may still be an alarm—but sulfur itself is also “the smell of life, baby.”