Map of life expectancy at birth from Global Education Project.

Monday, March 21, 2022

More on why we Stay Alive

A couple of days ago I referred to the doubling of human life expectancy in 100 years, and the importance of pasteurization of milk in making that happen. Our next installment is about water. There's nothing more basic than good old H2O, but it used to kill city dwellers about as often as milk. People actually figured this out even before Pasteur and Koch came up with the germ theory of disease.


Cholera is an intestinal infection caused by a bacterium called Vibrio cholera, which is spread through contaminated water or food. The disease causes severe diarrhea that can last for several days. Depending on the strain of bacteria, the fatality rate from untreated cholera can range from 5% to 50%. It was a common deadly disease in 19th Century cities. Before 1854, it was generally believed that cholera and other diseases were caused by “bad air” or “miasma,” a theory accepted from the time of Hippocrates. The miasma was supposedly created by rotting organic matter. In 1854 a cholera outbreak occurred in the Soho district of London. Physician John Snow mapped deaths from the outbreak and discovered that they mostly occurred among people whose nearest source of water was a pump on Broad Street. He persuaded the local council to remove the pump handle and the outbreak ended. (This is considered by many to be the seminal event in the history of public health.)

It was found that the water from the Broad Street well was contaminated with sewage from a cesspit. Snow also mapped outbreaks among people who received mechanically pumped water from commercial operators, and was able to associate them with water from the Thames that was contaminated with sewage. Pasteur and Koch had yet to develop the germ theory of disease, so Snow and his contemporaries had no idea of the causal mechanism. Nevertheless the idea that drinking water contaminated by sewage was a cause of cholera gradually came to be accepted.

By 1900, cities were building infrastructure to separate drinking water to sewage. But city water didn’t become fully safe until the development of chlorination. Once the germ theory of disease was understood, it became possible to experiment with chemical additives that would kill pathogens in water, and small amounts of chlorine were found to be effective. In 1899, Jersey City contracted for the construction of a new water system that would be free of contamination. The project was completed in 1904 but in a lawsuit concluded in 1908, the judge found that the Jersey City Water Company was not consistently delivering pure water.

The company’s sanitary adviser, physician John Leal, contracted for the construction of a plant to add chlorine to the Jersey City water supply. In a second trial, the judge concluded that the experiment was successful and that the water was now “pure and wholesome.” Cities rapidly adopted chlorination and by 1918 more than 1,000 North American cities were chlorinating their water. The result was a dramatic decline in deaths from waterborne disease. 

Note that nobody -- or hardly anyone, not anyone who is noticed nowadays -- demands the freedom to drink unchlorinated tap water. Some people, foolishly, don't do it, squander their money on bottled water, and throw away the plastic bottles. Now that's going back to nature! Here's a comparison of leading causes of death in the U.S. in 1900 and 2015.

 

You'll notice that back in the good old days, gastrointestinal infections were the third leading cause of death, and that's what we've mostly gotten rid of so far. (Notice they don't even who up today.) But what happened to tuberculosis, pneumonia and influenza. Stay tuned!


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