Improvements in public health

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Joseph Bazalgette designed the system. It had large intercepting sewers running alongside the Thames, which carried London's sewage east, away from the centre of the city, to outfalls at Beckton and Crossness.

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John Snow's work was significant because he used careful scientific investigation to show that cholera was spread through contaminated water, not bad air. Snow, a London doctor, doubted the miasma theory because cholera attacked the gut rather than the lungs, and he first published his ideas in 1849. During the cholera outbreak in Soho in 1854 he plotted the deaths on a map and found that they clustered around the Broad Street pump. Workers at the local brewery, who drank beer, and the inmates of the workhouse, which had its own well, were largely unaffected. He persuaded the parish authorities to remove the pump handle, and the outbreak, which was already declining, came to an end. He also compared houses supplied by two water companies and found that those receiving water from the sewage-polluted Thames had far more deaths.

At the time, however, his significance was limited. The General Board of Health and most doctors still believed in miasma and rejected his explanation, partly because he could not identify what in the water caused cholera; germ theory was not published until 1861.

In the longer term, Snow's work was very significant. When cholera struck East London in 1866, the government statistician William Farr linked it to an impure water supply in an area not yet connected to Bazalgette's new sewers, and he came to accept that cholera was waterborne. In 1883 Robert Koch identified the cholera bacterium, proving Snow right. His work strengthened the case for clean water and sewers, which the 1875 Public Health Act made compulsory, and his methods of mapping and comparing cases made him one of the founders of epidemiology.

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One similarity is that both used planned engineering to keep clean water separate from waste. Many medieval monasteries were built near springs or rivers and had piped water supplies and drains. A 12th-century plan of the waterworks of the cathedral priory at Canterbury shows water being piped from springs outside the city, through settling tanks, to the kitchen, washing places and fishponds, with the used water then flushing out the latrines. Bazalgette's sewers, built after 1859, did the same on a vast scale for London. Before them, sewage flowed into the Thames, from which many people's drinking water came. His intercepting sewers carried the sewage away from central London to outfalls at Beckton and Crossness, so the river through the city became cleaner.

A second similarity is that both depended on the wealth and organisation of a powerful body, and both worked without any understanding of germs. Monasteries were rich, well-organised communities, which is why they could plan, build and maintain water systems far better than the towns around them. Bazalgette's sewers needed the Metropolitan Board of Works, special powers from Parliament and about 3 million pounds of borrowing, granted after the Great Stink of 1858. In neither case did the builders know that germs in sewage caused disease. The monks valued cleanliness for religious reasons and believed in miasma, while Bazalgette and the MPs who paid for his sewers believed that the smell itself caused disease. In both cases, however, the systems improved health because they removed sewage from drinking water, even though no one understood why.

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Science and technology has been an important factor in improving public health, because it provided both the understanding of what caused disease and the engineering to provide clean water and remove sewage. However, scientific knowledge and technology were often available long before they were used, and it took government action to apply them to the whole population. Government has therefore been the more important factor.

In the Middle Ages there was little scientific understanding of disease, but technology could still make a difference. Monasteries built impressive systems of pipes and drains to provide clean water and remove waste; the monks at Canterbury had a piped water supply in the 12th century. Towns such as London built conduits to bring spring water. But without understanding the causes of disease, these improvements were limited, and in 1665 the measures against plague, such as killing cats and dogs, failed because no one knew that fleas spread it.

In the 19th century science and technology became much more important. Statistics collected by William Farr and used in Chadwick's report of 1842 showed the link between dirty conditions and early death. In 1854 John Snow used a scientific investigation to show that cholera spread through contaminated water. Engineering transformed London: Joseph Bazalgette's system of brick sewers and pumping stations carried sewage away from the city, and water companies began filtering water and moving their intakes upstream. Later, Pasteur's germ theory of 1861 and Koch's discovery of the cholera bacterium in 1883 explained why clean water mattered. In the 20th century vaccines, such as the diphtheria immunisation of the 1940s, and the chlorination of water supplies further reduced disease, while Doll and Hill's research in 1950 proved the link between smoking and lung cancer.

However, many improvements came before the science was understood. Chadwick and Bazalgette believed in miasma, but their sewers worked anyway. More importantly, the technology to build sewers existed for years before it was used, because government would not pay for it. Bazalgette's plans were only carried out after the Great Stink of 1858 forced Parliament to act. The 1848 Public Health Act was permissive, so few towns acted, and it was the compulsory 1875 Act that forced every council to provide clean water and sewers. In the 20th century the Clean Air Act of 1956 and the ban on smoking in public places in 2007 were government actions based on scientific evidence that had been known for years.

Other factors also mattered. Individuals such as Chadwick, Snow and Bazalgette applied science to public health. Chance events such as the Great Stink of 1858 and the Great Smog of 1952 pushed politicians into action. War, especially the Second World War, led to the Beveridge Report and the NHS.

In conclusion, science and technology has been a very important factor, because it provided the evidence and the engineering needed to improve public health. But it has not been the main factor, because scientific knowledge and technology were often ignored until government decided to act. The gap between Snow's discovery in 1854 and the compulsory Public Health Act of 1875 shows that government action was what turned science into better health for the whole population.