The miasma theory (also called the miasmic theory) is an abandoned medical theory that held that diseases—such as cholera, chlamydia, or plague—were caused by a miasma (, 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, the breath of humans and animals, and other odors. The theory explained why epidemics tend to happen in places with high population density, such as cities, as well as in swampy or hot and humid climates; and it addressed correlations between contagious diseases and lacking hygiene, lack of fresh air, and contacting the sick.
Though miasma theory is typically associated with the spread of contagious diseases, some academics in the early 19th 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 fifth century BC and accepted from ancient times in Europe, the Middle East, and China. The theory was eventually abandoned after 1880 and replaced by the germ theory of disease: microscopic germs, such as microorganisms and viruses, caused specific diseases, and were not only spread via the air but also via fluids and touching other objects.
Miasma theory motivated improvements in urban hygiene, such as the clean-up of waste and closing of sewers, thereby in fact reducing the spread of germs. It also encouraged the construction of well-ventilated hospital facilities, schools, and other buildings. Despite germ theory, bad air quality is still a health issue, whether it is caused by industrial pollution, exhaled air, or the airborne spread of germs.
Etymology The word "miasma" comes from ancient Greek and though conceptually, no word in English has the same exact meaning, it can be loosely translated as stain or pollution. The idea later gave rise to the name malaria (literally "bad air" in Medieval Italian).
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Miasma was considered to be a poisonous vapor or mist filled with particles from decomposed matter (miasmata) that caused illnesses. The miasmatic position was that diseases were the product of environmental factors such as contaminated water, foul air, and poor hygienic conditions. Such infection was not passed between individuals, but would affect individuals within the locale that gave rise to such vapors. It was identifiable by its foul smell. Initially miasmas were believed to be propagated through worms from ulcers within those affected by a plague.
Europe
In the fifth century BC, Hippocrates wrote about the effects of the environs over the human diseases:
In the first century BC, Roman architectural writer Vitruvius described the potential effects of miasma (Latin ) 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 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. Dr. 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 a deadly concentration of miasmata existed 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. Crimean War nurse Florence Nightingale (1820–1910) was a proponent of the theory and worked to make hospitals sanitary and fresh-smelling. Notes on Nursing for the Labouring Classes (1860) stated that Nightingale would "keep the air [the patient] breathes as pure as the external air."
Fear of miasma registered in many early 19th-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, and did not simply travel on air, but changed the air through which they 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.
China In China, miasma (; alternative names , ) is an old concept of illness, used extensively by ancient Chinese local chronicles and works of literature. Miasma has different names in Chinese culture. Most of the explanations of miasma refer to it as a kind of sickness or poison gas.
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 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, no description of miasma had been given. 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 miasmata 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。
Southern China was highly developed, though, 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。
Influence in Southern China The terrifying miasma diseases in the southern regions of China made it the primary location for relegating officials and sending criminals to exile since the Qin-Han dynasty. Poet Han Yu () of the Tang dynasty, for example, wrote to his nephew who came to see him off after his banishment to the Chao Prefecture in his poem, En Route, Translated by Arthur Waley in Chinese Poems. (左遷至藍關示姪孫湘):
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 (), a local magistrate from the Southern Song dynasty, described in his treatise Representative Answers from the South: "... 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。
India India also had a miasma theory. Gambir was considered the first antimiasmatic application. This gambir tree is found in southern India and Sri Lanka.
Developments from 19th century onwards Zymotic theory Based on zymotic theory, people believed vapors called miasmata (singular: miasma) rose from the soil and spread diseases. Miasmata were believed to come from rotting vegetation and foul water—especially in swamps and urban ghettos.
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, a general fear that cold or cool air spread disease also existed. 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. .
Contagionism versus miasmatism Prior to the late 19th century, "night air" was considered dangerous in most Western cultures. Throughout the 19th century, the medical community was divided on the explanation for disease proliferation. On one side were the contagionists, believing disease was passed through physical contact, while others believed disease was present in the air in the form of miasma, thus could proliferate without physical contact. Two members of the latter group were Dr. Thomas Southwood Smith and Florence Nightingale. Smith spent many years comparing the miasmatic theory to contagionism.
Nightingale focused on hygiene causing miasma:
The current germ theory accounts for disease proliferation by both direct and indirect physical contact.
Influence on sanitary engineering reforms