Lifesavers · No. 03
Clean water
Filtering and chlorinating city water was responsible for about 43 percent of the fall in urban death rates in early 20th-century America, and three-quarters of the drop in infant deaths.
Updated
A share of the mortality decline in US cities, not a global lives-saved count. The mechanism scaled worldwide.
How it saves lives
Much of the old urban death toll came from waterborne infections like typhoid and cholera and from the diarrhoea that killed infants. Passing drinking water through sand filters and adding a trace of chlorine removed or killed the germs before anyone drank them, quietly closing off a whole category of death.
The story
It is one of the least dramatic lifesavers and one of the largest. There was no single inventor and no ceremony, just engineers plumbing filtration and chlorination into one city after another. Economists David Cutler and Grant Miller later measured what it did to American cities in the first decades of the century and found that clean water alone explained a huge share of a sudden, historic fall in death rates, especially among babies.
From the record
clean water was responsible for about 43 percent of the total mortality decline in the 13 cities from 1900 to 1936
Asked often
How many lives did clean water save?
Economists Cutler and Miller calculated that water filtration and chlorination were responsible for about 43 percent of the total fall in death rates across 13 US cities from 1900 to 1936, including three-quarters of the drop in infant mortality.
Who invented water chlorination?
There was no single inventor. Sand filtration and chlorine disinfection were adopted by city water systems across the US and Europe in the early 1900s, one of the great unsung public-health advances.
Further reading
Read the whole story
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The history
The Ghost Map (opens Bookshop.org)
Steven Johnson · 2006
Steven Johnson recounts the 1854 Broad Street cholera outbreak, in which John Snow traced the disease to one water pump, and the sanitation reforms that followed. It predates chlorination.
The next one is being invented now.
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