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The miasma theory (also called the miasmic theory) is an abandoned medical theory that held that —such as cholera, chlamydia, or the Black Death—were caused by a miasma (μίασμα, Ancient Greek for 'pollution'), a noxious form of "bad air", also known as night air. The theory held that epidemics were caused by miasma, emanating from rotting organic matter. Though miasma theory is typically associated with the spread of contagious diseases, some academics in the early nineteenth century suggested that the theory extended to other conditions as well, e.g. one could become obese by inhaling the odor of food.
The miasma theory was advanced by Hippocrates in the fourth century BC and accepted from ancient times in Europe and China. The theory was eventually abandoned by and after 1880, replaced by the germ theory of disease: specific germs, not miasma, caused specific diseases. However, cultural beliefs about getting rid of odor made the Waste management a high priority for cities. (2025). 9780520248878, University of California Press. ISBN 9780520248878 (1995). 9780195111286, Oxford University Press. ISBN 9780195111286 It also encouraged the construction of well-ventilated hospital facilities, schools and other buildings.
The idea later gave rise to the name malaria (literally 'bad air' in Medieval Italian).
In the 1st century BC, the Roman architectural writer Vitruvius described the potential effects of miasma (Latin nebula) from fetid swamplands when visiting a city:
The miasmatic theory of disease remained popular in the Middle Ages and a sense of effluvia contributed to Robert Boyle's Suspicions about the Hidden Realities of the Air.
In the 1850s, miasma was used to explain the spread of cholera in London and in Paris, partly justifying Haussmann's later renovation of the French capital. The disease was said to be preventable by cleansing and scouring of the body and items. William Farr, the assistant commissioner for the 1851 London census, was an important supporter of the miasma theory. He believed that cholera was transmitted by air, and that there was a deadly concentration of miasmata near the River Thames' banks. Such a belief was in part accepted because of the general lack of air quality in urbanized areas. The wide acceptance of miasma theory during the cholera outbreaks overshadowed the partially correct theory brought forth by John Snow that cholera was spread through water. This slowed the response to the major outbreaks in the Soho district of London and other areas. The Crimean War nurse Florence Nightingale (1820–1910) was a proponent of the theory and worked to make hospitals sanitary and fresh-smelling. It was stated in 'Notes on Nursing for the Labouring Classes' (1860) that Nightingale would "keep the air the breathes as pure as the external air."
Fear of miasma registered in many early nineteenth-century warnings concerning what was termed "unhealthy fog". The presence of fog was thought to strongly indicate the presence of miasma. The miasmas were thought to behave like smoke or mist, blown with air currents, wafted by winds. It was thought that miasma did not simply travel on air but changed the air through which it propagated; the atmosphere was infected by miasma, as diseased people were.Valenčius, Conevery B. The Health of the Country: How American Settlers Understood Themselves and Their Land. New York: Basic Books, 2002. pp. 115–17. Print.
The ancient Chinese thought that miasma was related to the environment of parts of Southern China. The miasma was thought to be caused by the heat, moisture and the dead air in the Southern Chinese mountains. They thought that insects' waste polluted the air, the fog, and the water, and the untouched forest harbored a great environment for miasma to occur.
In descriptions by ancient travelers, soldiers, or local officials (most of them are men of letters) of the phenomenon of miasma, fog, haze, dust, gas, or poison geological gassing were always mentioned. The miasma was thought to have caused a lot of diseases such as the cold, influenza, heat strokes, malaria, or dysentery. In the medical history of China, malaria had been referred to by different names in different dynasty periods. Poisoning and psittacosis were also called miasma in ancient China because they did not accurately understand the cause of disease.
In the Sui dynasty (581–618 CE), doctor Chao Yuanfang mentioned miasma in his book On Pathogen and Syndromes (諸病源候論). He thought that miasma in Southern China was similar to typhoid fever in Northern China. However, in his opinion, miasma was different from malaria and dysentery. In his book, he discussed dysentery in another chapter, and malaria in a single chapter. He also claimed that miasma caused various diseases, so he suggested that one should find apt and specific ways to resolve problems.(隋)巢元方撰，曹赤電炳章圈點，《巢氏諸病源候論》，(台北：國立中國醫藥研究所，1996)，頁30、47–51。
The concept of miasma developed in several stages. First, before the Western Jin dynasty, the concept of miasma was gradually forming; at least, in the Eastern Han dynasty, there was no description of miasma. During the Eastern Jin, large numbers of northern people moved south, and miasma was then recognized by men of letters and nobility. After the Sui and the Tang dynasty, scholars-bureaucrats sent to be the local officials recorded and investigated miasma. As a result, the government became concerned about the severe cases and the causes of miasma by sending doctors to the areas of epidemic to research the disease and heal the patients. In the Ming dynasty and Qing dynasty, versions of local chronicles record different miasma in different places.牟重行，王彩萍，〈中國歷史上的「瘴氣」考釋〉，《國立臺灣師範大學地理研究報告》，(第38期，台北：國立臺灣師範大學地理學系，2003)，頁25。
However, Southern China was highly developed in the Ming and Qing dynasties. The environment changed rapidly, and after the 19th century, western science and medical knowledge were introduced into China, and people knew how to distinguish and deal with the disease. The concept of miasma therefore faded out due to the progress of medicine in China.牟重行，王彩萍，〈中國歷史上的「瘴氣」考釋〉，《國立臺灣師範大學地理研究報告》，(第38期，台北：國立臺灣師範大學地理學系，2003)，頁25–26。
The prevalent belief and predominant fear of the southern region with its "poisonous air and gases" is evident in historical documents.
Similar topics and feelings toward the miasma-infected south are often reflected in early Chinese poetry and records. Most scholars of the time agreed that the geological environments in the south had a direct impact on the population composition and growth. Many historical records reflect that females were less prone to miasma infection, and mortality rates were much higher in the south, especially for the men. This directly influenced agriculture cultivation and the southern economy, as men were the engine of agriculture production. Zhou Qufei (周去非), a local magistrate from the Southern Song dynasty, described in his treatise Lingwai Daida: "... The men are short and tan, while the women were plump and seldom came down with illness,", 宋周去非, 嶺外代答, 卷十, 276. and exclaimed at the populous female population in the Guangxi region.
This inherent environmental threat also prevented immigration from other regions. Hence, development in the damp and sultry south was much slower than in the north, where the dynasties' political power resided for much of early Chinese history.龔勝生，〈2000年來中國瘴病分布變遷的初步研究〉，《地理學報》，第48卷第4期，(西安：陜西師範大學中國歷史地理研究所，1993)，頁305–312。
Many people, especially the weak or infirm, avoided breathing night air by going indoors and keeping windows and doors shut. In addition to ideas associated with zymotic theory, there was also a general fear that cold or cool air spread disease. The fear of night air gradually disappeared as understanding about disease increased as well as with improvements in home heating and ventilation. Particularly important was the understanding that the agent spreading malaria was the mosquito (active at night) rather than miasmata.Cipolla, Carlo M. Miasmas and disease: Public health and environment in the pre-industrial age. Yale University Press, 1992. .
Thomas Southwood Smith spent many years comparing the miasmatic theory to contagionism.
Florence Nightingale:
The current germ theory accounts for disease proliferation by both direct and indirect physical contact.
Chadwick saw the problem of cholera and typhoid epidemics as being directly related to urbanization, and he proposed that new, independent sewerage systems should be connected to homes. Chadwick supported his proposal with reports from the London Statistical Society which showed dramatic increases in both morbidity and mortality rates since the beginning of urbanization in the early 19th century. Though Chadwick proposed reform on the basis of the miasma theory, his proposals did contribute to improvements in sanitation, such as preventing the reflux of noxious air from sewers back into houses by using separate drainage systems in the design of sanitation. That led, incidentally, to decreased outbreaks of cholera and thus helped to support the theory.
The miasma theory was consistent with the observation that disease was associated with poor sanitation, and hence foul odours, and that sanitary improvements reduced disease. However, it was inconsistent with the findings arising from microbiology and bacteriology in the later 19th century, which eventually led to the adoption of the germ theory of disease, although consensus was not reached immediately. Concerns over sewer gas, which was a major component of the miasma theory developed by Galen, and brought to prominence by the "Great Stink" in London in the summer of 1858, led proponents of the theory to observe that sewers enclosed the refuse of the human bowel, which medical science had discovered could teem with typhoid, cholera, and other microorganism.
The Nuisances Removal and Diseases Prevention Act 1846 was passed to identify whether the transmission of cholera was by air or by water. The act was used to encourage owners to clean their dwellings and connect them to sewers.
Even though eventually disproved by the understanding of bacteria and the discovery of , the miasma theory helped establish the connection between poor sanitation and disease. That encouraged cleanliness and spurred public health reforms which, in Britain, led to the Public Health Act 1848 the Public Health Act 1858, and the Local Government Act 1858. The latter of those enabled the instituting of investigations into the health and sanitary regulations of any town or place, upon the petition of residents or as a result of death rates exceeding the norm. Early medical and sanitary engineering reformers included Henry Austin, Joseph Bazalgette, Edwin Chadwick, Frank Forster, Thomas Hawksley, William Haywood, Henry Letheby, Robert Rawlinson, John Simon, John Snow and Thomas Wicksteed. Their efforts, and associated British regulatory improvements, were reported in the United States as early as 1865.
Particularly notable in 19th century sanitation reform is the work of Joseph Bazalgette, chief engineer to London's Metropolitan Board of Works. Encouraged by the Great Stink, Parliament sanctioned Bazalgette to design and construct a comprehensive system of sewers, which intercepted London's sewage and diverted it away from its water supply. The system helped purify London's water and saved the city from epidemics. In 1866, the last of the three great British cholera epidemics took hold in a small area of Whitechapel. However, the area was not yet connected to Bazalgette's system, and the confined area of the epidemic acted as testament to the efficiency of the system's design.
Years later, the influence of those sanitary reforms on Britain was described by Richard Rogers:
The miasma theory did contribute to containing disease in urban settlements, but did not allow the adoption of a suitable approach to the reuse of excreta in agriculture. It was a major factor in the practice of collecting human excreta from urban settlements and reusing them in the surrounding farmland. That type of resource recovery scheme was common in major cities in the 19th century before the introduction of sewer-based sanitation systems. Nowadays, the reuse of excreta, when done in a hygienic manner, is known as ecological sanitation, and is promoted as a way of "closing the loop".
Throughout the 19th century, concern about public health and sanitation, along with the influence of the miasma theory, were reasons for the advocacy of the then-controversial practice of cremation. If infectious diseases were spread by noxious gases emitted from decaying organic matter, that included decaying corpses. The public health argument for cremation faded with the eclipsing of the miasma theory of disease."USA." Encyclopedia of Cremation. Surrey: Ashgate Publishing, 2005. Credo Reference. Web. 17 September 2012.
In 1855, John Snow made a testimony against the Amendment to the "Nuisances Removal and Diseases Prevention Act" that regularized air pollution of some industries. He claimed that:
The same year, William Farr, who was then the major supporter of the miasma theory, issued a report to criticize the germ theory. Farr and the Committee wrote that:
By 1866, eight years after the death of John Snow, William Farr publicly acknowledged that the miasma theory on the transmission of cholera was wrong, by his statistical justification on the death rate.
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