In the hot summer of 1858, the River Thames smelled so foul that the curtains of the Houses of Parliament were soaked in chemicals to keep out the stench. Newspapers called it the Great Stink. For decades London's toilets and cesspools had drained into the river, which was also a major source of drinking water. Lawmakers who had ignored warnings for years suddenly found the problem under their own windows, and within weeks they approved funding for a new sewer system. It was a turning point in the sanitary revolution, the nineteenth-century movement that did more to lengthen human lives than almost any medicine.
Edwin Chadwick and the sanitary idea
Industrial cities grew faster than anyone could plan them. Workers crowded into damp housing with shared privies, open drains and polluted wells. In 1842 the English reformer Edwin Chadwick published his Report on the Sanitary Condition of the Labouring Population of Great Britain. It showed that average age at death differed sharply by class and place. In Liverpool, he reported, laborers died at an average age of about 15, a figure dragged down by child deaths, while gentry in rural Rutland lived on average to 52. Chadwick still believed in miasma, but his practical conclusion was right: drain the cities, remove waste and supply clean water, and disease would fall. His work helped produce Britain's Public Health Act of 1848, one of the first national public health laws.
Bazalgette's sewers
After the Great Stink, the engineer Joseph Bazalgette built a network of intercepting sewers that carried London's waste east, away from the city center, before releasing it into the Thames further downstream. The system linked more than 1,000 miles of street sewers to about 80 miles of large main sewers. Bazalgette made his pipes much wider than the population of the day required, reasoning that the city would grow, and much of his system is still in use. When cholera returned to London in 1866, it struck mainly an eastern district not yet connected to the new system and supplied with poorly filtered water, which helped convince doubters that water had been the problem all along.
Clean hands
Sanitation also means hygiene. In 1847 the Hungarian doctor Ignaz Semmelweis, working in a Vienna maternity hospital, noticed that women on the ward staffed by doctors and medical students died of childbed fever far more often than women on the ward run by midwives. The doctors often came straight from performing autopsies. When Semmelweis required them to wash their hands in a chlorine solution, deaths dropped dramatically. Many colleagues rejected his findings, and he died in an asylum in 1865. Around the same time, Florence Nightingale, who had seen soldiers in the Crimean War die more often from disease than from wounds, used statistics and vivid charts to campaign for clean, ventilated hospitals. Hand hygiene remains one of the simplest and most effective ways to prevent infections in health care today.
Filters and chlorine
The next leap came at the water plant. Sand filtration spread in the late 1800s, and in 1908 Jersey City, New Jersey, became one of the first places in the United States to chlorinate a public water supply continuously. Typhoid fever, which spreads through contaminated water and food, plunged in cities that filtered and chlorinated their water. The economists David Cutler and Grant Miller estimated that clean water technologies were responsible for nearly half of the drop in total mortality in major American cities between 1900 and 1936, and about three quarters of the fall in infant deaths. Many historians rank water treatment among the most important public health advances of the twentieth century.
The unfinished job
Sanitation is not just history. According to the WHO and UNICEF, in 2022 about 2.2 billion people still lacked safely managed drinking water, and about 3.5 billion lacked safely managed sanitation. Diarrheal diseases linked to unsafe water, sanitation and hygiene kill hundreds of thousands of young children every year. Wealthy countries are not immune to failure. In Flint, Michigan, a 2014 decision to switch the city's water source without proper corrosion control allowed lead to leach from old pipes into homes, exposing children to a toxin that can harm brain development. The crisis showed that infrastructure needs constant care, and that communities with little political power are often the last to be heard when they say something is wrong.
Worked example: after the flood
A river floods a town and overwhelms its sewage treatment plant. What does a public health team do? First, it issues a boil-water notice so residents do not drink contaminated tap water, and it distributes bottled water to those who cannot boil it. Next it tests water samples to track bacteria levels and watches clinic reports for a rise in diarrhea, an early warning of an outbreak. It reminds residents to wash hands with safe water, throw out food touched by floodwater and keep children away from standing water. Finally, once the emergency passes, it asks the harder question Chadwick would have asked: why was the plant so vulnerable, and which neighborhoods flooded worst? Fixing that is slower and more expensive, but it is where lasting prevention lies.