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Last edited 17 Sep 2021
|This sketch depicts a man holding his nose to avoid breathing in a miasma.|
Miasma is a noxious vapour caused by decomposing particles created by moulds, dust, rotting flesh or decaying vegetation. Miasma theory is the belief that odours associated with miasma could potentially result in disease or death. Until the theory was discredited, it motivated sanitation engineers and healthcare professionals to explore issues of air quality and waste management in urban areas, hospitals and other types of buildings.
References to miasmic fumes entering the body and causing disease go back to ancient Greece. While many people during this period associated pestilence with supernatural forces, the Greek physician Hippocrates recognised the connection between bad air and epidemics, which initiated a more scientific approach to treating illnesses.
Exploration of miasma theory continued through early Christian times into the Middle Ages when bad air became the most widely accepted explanation for the spread of disease. One method of fighting miasma was to wear a mask filled with pleasantly scented flowers, which is what doctors did during periods of plague.
It was also during this time that English sanitary reform began. Based on the idea that miasma was the cause of disease in poor neighbourhoods that were undrained, toxic and foul smelling, engineers slowly introduced additional sanitation measures. Swamps were drained and the management of human waste - removing it from populated areas - was initiated.
These measures addressed the issue of smell - the basis of miasma theory - and resulted in some improvements, but failed to recognise the significance of other types of cleanliness such as proper hand washing and the use of disinfectant.
 Disproving the theory of bad air
It wasn’t until the mid 1800s that scientists discovered there was more than smell - no matter how pungent or revolting - to the spread of contagion and contamination. At the core of their research was the idea of decay (also inherently associated with the miasma theory) and its cause. It was this research that eventually led to the identification of microorganisms (or germs), not odours, as the cause of infection. With this discovery, germ theory began to replace miasma theory as the acknowledged source of disease.
In the UK, several cholera epidemics of the mid-1800s prompted germ theory-based improvements to sanitation systems, water purification and food hygiene. But some scientists still believed the miasma theory was the cause, noting the connection between lower outbreak numbers in populations where the air was better (more specifically, in remote locations at higher elevations). The miasma theory was eventually disproved and replaced by germ theory.
 More miasma theory sanitation successes and failures
In the United States, George E. Waring, Jr, a 19th-century sanitation engineer and miasmist, incorporated the theory into several noteworthy undertakings, including the complex drainage system for Central Park in New York City (designed by landscape architect Frederick Law Olmsted and architect Calvert Vaux in the 1850s). The park was built on a swamp and required an elaborate network of tubes that took the water away from the park and directed it to reservoirs and natural bodies of water.
After the American Civil War, Waring became the sanitation commissioner for New York City. After hiring numerous sanitation workers (and dressing them in white), he imposed a rigorous method of street cleaning and waste removal to address problems caused by horse manure, rubbish and other intolerable conditions.
Waring was next called upon to bring his miasma theory approach to Havana, where a yellow fever epidemic was killing American soldiers stationed in Cuba. Although Waring was able to introduce his street cleaning approach to the city, miasma theory could not protect him from the mosquitos that caused the illness. He contracted the disease in Cuba and died shortly after his return to the United States.
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