A History of Water and Human Health
This post is part of our History of Water Supply series
We have a fairly good idea of how our ancestors judged questionable water sources: the “sniff test.” Humans have a natural ability to detect foul odors, which goes a long way in helping us tell good water from bad. But the fact that bacteria is invisible and often odorless meant that we overlooked the real culprits behind sickness until a much later period in scientific development.
It was this shortcoming of our senses that gave rise to the widespread phenomenon of what’s now named miasma theory, the long-held misconception that bad health was caused by dirty airs and poisonous vapors. In other words, people attributed the causes of physical unhealth to hazy, murky air and the associated stench, because it is what they could see and smell. They blamed bad air while ignoring bad water.
Almost 2500 years ago, Hippocrates, the “Father of Medicine,” wrote a book named “Airs, Waters, and Places,” in which he advanced the idea that water was a major factor in the health of communities. He classified water by sources—rain, spring, river, or stagnant— and developed sound methods for studying these individually, thereby establishing some of the first links between the environment and prevalence of disease. To understand the health of people, Hippocrates knew, you had to understand their water.
Despite the best efforts of Hippocrates and others like him, for thousands of years many populations were constant prey to vicious and often lethal digestive disorders. Even worse, they were ignorant to the waterborne diseases that were the cause. There is, however, evidence that some groups put Hippocrates’ ancient wisdom into practice: primitive filtration and purification techniques, usually by forming natural materials into rudimentary tools like sand, grain, and charcoal filters, have been discovered in archaeological sites. Charcoal filters, in particular, would prove to be a timeless technique and a forerunner to the activated charcoal still in use today.
Another early (and still effective) method of purifying water is boiling. Although written evidence from several historic cultures suggest that boiling was used to purify water, countless pandemics now attributed to waterborne illness suggest that boiling was not widely adopted.
In fact, waterborne illness remained a persistent threat nearly everywhere until modern times. The provision of clean, healthy water is only recently seen as an essential government service.
But how did we eventually see the “bad air” for what it really was—a red herring, and a misconception? When and why did we start to take a closer look at the invisible life inside water, and how did these advances shape the lives we enjoy today? It all started with microscopy.
Microscopy: Zooming in on Water
Everything changed once we were able to take a look at the microscopic particles within water. Amazingly, despite first appearing in the 17th century, microscopic studies were conducted for around 200 years before scientists could piece together the relationship between sickness and waterborne bacteria. At the end of the 17th century, Antonie van Leeuwenhoek first observed living particles in water after comparing various sources of water (rain water, pond water, and even his own saliva…), but he never managed to connect these microorganisms to disease.
Then came the Industrial Revolution, with its new technology and its mass urbanization. This combination created a dynamic human petri dish for studying the emergence and proliferation of disease. And there is no case more famous than that of London’s Broad Street Pump:
In 1854, during a deadly cholera outbreak in London’s Soho district, physician John Snow made a groundbreaking discovery that changed the course of public health and epidemiology. At a time when the miasma theory was still common currency, Snow hypothesized that cholera was actually waterborne. Through meticulous mapping and interviews, he traced the outbreak to a single source: the public water pump on Broad Street. He convinced the local authorities to remove the pump handle, and the number of new cholera cases plummeted. Snow’s work provided one of the earliest and most compelling pieces of evidence that contaminated water—not air—was the primary vehicle for disease transmission.
Building on Snow’s legacy, Louis Pasteur later demonstrated that microorganisms could cause fermentation and disease, and Robert Koch provided concrete proof by isolating specific bacteria responsible for illnesses like tuberculosis and cholera. Together, these advancements transformed medicine and public health, establishing the fields of microbiology and epidemiology, and forever replacing the miasma theory with today’s germ theory of disease.
Armed with the knowledge that waterborne microorganisms were the true culprits behind many diseases, cities around the world began investing in large-scale water treatment and sanitation systems. Filtration, chlorination, and the development of modern sewer networks became cornerstones of urban infrastructure, dramatically reducing the spread of waterborne illnesses.
