Science  /  Q&A

In 19th-Century America, Fighting Disease Meant Battling Bad Smells

The history of unpleasant odor, or miasma, has unexpected relevance in the time of COVID-19.

Atlas Obscura spoke to Kiechle about America’s olfactory anxieties, 19th-century fears of disease, and what these histories can teach us about the COVID-19 pandemic.

What did 19th-century cities smell like?

If you were dropped from the present into a 19th-century city, you would say that it stinks. Horses, cows, pigs, dogs, chickens, and a host of other animals made their homes on city streets, where they found food and deposited their waste. Cities smelled strongly of manure as well as industrial activities. I’m talking about slaughterhouses and bone boilers, fertilizer manufacturers and leather tanners, fat renderers and distillers that fermented grain to make alcohol. Nineteenth-century Americans called these the “offensive trades” because they offended the nose. After the mid-century discovery of petroleum, oil refiners joined the list.

Even though many of these odors were familiar, 19th-century Americans worried about them because they were concentrated to new intensities. Since air was supposed to be “inodorous”—even Webster’s American Dictionary said this—strong odors were a bad sign. The New York Times warned Americans: “Here, in the City, you respire disease. Odious gases regale you at every step. The air is heavy with noxious smells.”

How did bad air become synonymous with disease?

Miasma theory, which held that bad airs spread disease, was a widespread belief with a long history. At the end of the 18th century, scientists discovered that the air humans and animals exhale could kill. Experimenters such as Joseph Priestley put mice in airtight bell jars and observed that the mice died when alone, but lived longer if there was a plant inside. These experiments led doctors to warn against inhaling “carbonic acid gas” (today we call it carbon dioxide) by breathing in air that others had exhaled––a common occurrence in crowded urban spaces like theaters, schools, and churches.

In the 19th century, miasma theory no longer came from physicians, but was common sense, in that most people shared this understanding and regularly acted on it. Americans learned from a young age to cover their noses, to grow sweet-smelling plants, to close their windows against stinky breezes, and to avoid places that smelled badly to protect against everything from headaches and nausea to cholera and yellow fever. People were very attentive to changes in the air they breathed.

Now that we have a scientific understanding of microbes and bacteria, it is no longer valid to believe that miasma causes illness. However, this was the best understanding that people had before germ theory, and it often resulted in people doing the “right” thing to protect health, just for what today we know is the wrong reason. And the idea that a disease is airborne is still very much alive and valid.