Miasma Theory: A Primer

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I recently received an unusual request—could I explain miasma theory to an NPR reporter? Miasma theory is suddenly newsworthy, roughly 150 years after germ theory displaced this explanation for the origins and spread of diseases, because of Robert F. Kennedy, Jr., Secretary of Health and Human Services. In his 2021 The Real Anthony Fauci, Kennedy wrote positively about miasma theory while disparaging “the domineering ascendancy of germ theory as the cornerstone of contemporary public health policy.”^[1] As Kennedy disrupts medical research and health guidance at the highest levels in the United States, reporters are scrambling to understand his reasoning.

If miasma theory is guiding Kennedy’s decisions, what do we need to know about it?

1. Miasma Theory is about the Air

Miasma theory offered a powerful and compelling explanation of what caused disease since first explained by the ancient Greek physician Hippocrates. In Airs, Waters, and Places, Hippocrates postulated that an interaction between air, water, and soil released miasm (Greek for pollution).^[2] By the nineteenth century, miasma was defined as “infecting substances floating in the air; the effluvia of any putrefying bodies, rising and floating in the atmosphere.”^[3] The theory held that illness resulted from inhaling miasma, a corruption of the air that was especially prominent in marshy areas. This meant that illnesses were the product of local environmental conditions, not transmitted from an infected person to another. A miasma did not have to smell, but the odors of decomposition warned of miasma’s presence.

The popular understanding of miasma theory was summed up by nineteenth-century British reformer Edwin Chadwick: “all smell is disease.”^[4] Chadwick meant, quite literally, that strong stenches made people sick. Like Kennedy, Chadwick was neither a scientist nor a physician. Chadwick’s pithy phrase is easy to understand and remember, but it is neither an accurate nor complete definition of miasma theory.

2. Anyone Could Apply Miasma Theory

Miasma theory endured because it relied on correlation and human perception. One did not need scientific training or a medical degree to locate stenches when illness struck. When yellow fever devastated Philadelphia in 1793, prominent physician Benjamin Rush blamed the stench emitted by a heap of rotting coffee beans. When cholera struck Providence, Rhode Island in 1854, physician Edwin Snow connected the two highest concentrations of deaths to local nuisances: a polluted canal and a concentration of filthy hog pens. Similarly, when encountering an illness in their family, wives and mothers could postulate its origins in a fetid barn, a stinking outhouse that needed lime, or a closed room that needed airing.

3. Scientists Refined Miasma Theory

Miasma theory also endured into the nineteenth century because it was capacious. Scientists fit new discoveries about gases into this existing paradigm throughout the eighteenth and nineteenth centuries. When eighteenth-century chemists Joseph Black, Joseph Priestly, and Antoine Lavoisier discovered that carbon dioxide was a byproduct of human respiration, they spoke of exhalations as casting out putrefaction from the lungs, essentially defining carbon dioxide as a miasma. In crowded or unventilated rooms, the act of breathing “vitiated” or ruined the air by filling it with carbon dioxide.

Similarly, when German chemist Christian Friedrich Schönbein discovered ozone in 1839, scientists measured ozone’s incidence in nature. They found high concentrations of ozone in presumably healthy environments, such as in pine forests, at higher elevations, and at the seashore. Ozone fit into miasma theory as “the natural scavenger” that “purifies the air” by “destroying noxious gases” and “oxidizing decomposing organic substances.”^[5] By the mid-nineteenth century, public health physicians such as New Orleans’s Edward H. Barton were studying the interactions between soil and air to offer increasingly precise explanations of the conditions that produced miasma.

Conversely, discoveries that did not align with miasma theory often met skepticism and derision. For example, physicians scoffed at British surgeon Joseph Lister’s realization in the 1860s that surgical instruments should be sterilized to prevent infection. As Nancy Tomes writes in The Gospel of Germs, physicians were stridently divided over Pasteur and Koch’s microbial discoveries as well.

4. Miasma Theory Supported Sanitary Measures

Miasma theory, whether refined with the newest chemical research or in its popularly understood form, offered useful guidance for how individuals and governments could prevent disease. By avoiding swamps, bogs, and stagnant water, people escaped marsh miasma. Nineteenth-century sanitation guided public health officers and individuals to remove filth and decaying matter from the proximity of their homes, to build sewers to carry wastes away from city centers, and to increase ventilation. Physicians warned of “crowd diseases” in overcrowded and under-ventilated spaces. Cities built public parks as “urban lungs” to purify the air of the city. And scientists designed respirators that covered the nose and mouth, filtering the air through charcoal when one could not avoid a miasmatic space.

5. Germ Theory Replaced It

By the end of the nineteenth century, germ theory was replacing miasma theory as the most prominent explanation for the cause and spread of disease. In the 1860s and 70s, chemists Louis Pasteur (France) and Robert Koch (Germany) discovered that microbes – bacteria and viruses invisible to the human eye – were the source of infectious diseases. By pairing specific microbes with particular illnesses, germ theory revolutionized medicine with the promise that eliminating pathogens would end the diseases that they caused.

By and large, twentieth-century biomedicine bore out this promise. Nineteenth-century researchers identified specific disease-causing microbes (vibrio cholera caused cholera, mycobacterium tuberculosis generated tuberculosis, variola virus spread smallpox) or the vectors along which microbes spread (mosquitoes transmit the yellow fever virus). With the knowledge of which germ that caused a disease, twentieth-century microbiologists and epidemiologists created interventions or treatments – frequently, antibiotics for bacteria and vaccines for viruses, but also pesticides that kill mosquitoes – that targeted the culprit. Germ theory has explained scores of infectious diseases, many of which, like polio and smallpox, have receded from popular memory due to effective precautions or treatments.

Germ theory does not address the causes of chronic conditions, cancers, or autoimmune disorders.

Covid-19: Miasma Theory Redux?

Miasma theory may sound plausible today because of the Covid-19 pandemic. For much of the twentieth century, physicians and scientists dismissed the idea that illness could be transmitted through the air. But when contact tracing revealed multiple outbreak clusters that could only be explained by aerial transmission, the World Health Organization (reluctantly) declared that covid was airborne. Public health guidance for preventing covid’s spread includes increasing ventilation, avoiding crowds, and wearing masks. These practices parallel nineteenth-century disease precautions, but were confusing and frustrating for those who had learned to worry about germs and nothing else. But the coronavirus is a virus. The covid pandemic was not a return to miasma theory.

RFK Jr. also is not returning to miasma theory. He does not advocate for face masks, asserts that social distancing “rested on a dubious scientific footing,” and says nothing about ventilation or indoor air quality.^[6] Kennedy has a different idea in mind when he dismisses vaccines, an idea that also got its start in the nineteenth century.

Notes

1. Robert F. Kenndy, Jr., The Real Anthony Fauci: Bill Gates, Big Pharma, and the Global War on Democracy and Public Health (New York: Skyhorse Publishing, 2021), 286. ↑
2. On Hippocrates and ancient Greek medicine, see: Jacques Jouanna, Greek Medicine from Hippocrates to Galen: Selected Essays, ed. Philip van der Eijk, tans. Neil Allies (Boston: Brill, 2012), ch. 4 & 7. ↑
3. Noah Webster, An American Dictionary of the English Language, 9th edition., s.v. “miasma” ↑
4. Select Committee on Metropolitan Sewage Manure, Report, no. 474 ([London?], 1846), 109. On Chadwick, see Christopher Hamlin, Public Health and Social Justice in the Age of Chadwick (Cambridge: Cambridge University Press, 1998); and Steven Johnson, The Ghost Map: The Story of London’s Most Terrifying Epidemic and How It Changed Science, Cities, and the Modern World (New York: Riverhead Books, 2006). ↑
5. J.C. “Ozone,” Once a Week 12, no. 290 (January 14, 1865): 94. ↑
6. Kennedy, The Real Anthony Fauci, 3 ↑

 

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Featured image caption: “The Plague of the Philistines at Ashdod,” oil painting by Pieter van Halen, 1661. In the painting, people hold their hands over their mouths and noses to avoid inhaling the poisonous miasma of plague which was thought to emerge from the bodies of the dead. (Courtesy Wellcome Collection)