by Neil Cummins (LSE), Morgan Kelly (University College Dublin), Cormac Ó Gráda (University College Dublin)
A repost from VoxEU.org
Between 1563 and 1665, London experienced four plagues that each killed one fifth of the city’s inhabitants. This column uses 790,000 burial records to track the plagues that recurred across London (epidemics typically endured for six months). Possibly carried and spread by body lice, plague always originated in the poorest parishes; self-segregation by the affluent gradually halved their death rate compared with poorer Londoners. The population rebounded within two years, as new migrants arrived in the city “to fill dead men’s shoes”.
For more than a century, London struggled with some of the worst air pollution on earth. But how much did air pollution affect health in London? How did these effects change as the city developed? Can London’s long experience teach us lessons that are relevant for modern cities, from Beijing to New Delhi, that are currently struggling with their own air pollution problems?
To answer these questions, I study the effects of air pollution in London across a full century from 1866 to 1965. Using new data, I show that air pollution was a major contributor to mortality in London during this century – accounting for at least one out of every 200 deaths during this century.
As London developed, the impact of air pollution changed. In the nineteenth century, Londoners suffered from a range of infectious diseases, including respiratory diseases like measles and tuberculosis. I show that being exposed to high levels of air pollution made these diseases deadlier, while the presence of these diseases made air pollution more harmful. As a result, when public health and medical improvements reduced the prevalence of these infectious diseases, they also lowered the mortality cost of pollution exposure.
This finding has implications for modern developing countries. It tells us that air pollution is likely to be more deadly in the developing world, but also that investments that improve health in other ways can lower the health costs of pollution exposure.
An important challenge in studying air pollution in the past is that direct pollution measures were not collected in a consistent way until the mid-twentieth century. To overcome this challenge, this study takes advantage of London’s famous fog events, which trapped pollution in the city and substantially increased exposure levels.
While some famous fog events are well known – such as the Great Fog of 1952 or the Cattle Show Fog of 1873, which killed the Queen’s prize bull – London experienced hundreds of lesser-known events over the century I study. By reading weather reports from the Greenwich Observatory covering over 26,000 days, we identified every day in which heavy fog occurred.
To study how these fog events affected health, I collected detailed new mortality data describing deaths in London at the weekly level. Digitised from original sources, and covering over 350,000 observations, this new data set opens the door to a more detailed analysis of London’s mortality experience than has previously been possible.
These new mortality data allow me to analyse the effects of air pollution from a variety of different angles. I provide new evidence on how the effects of air pollution varied across age groups, how the effect on different age groups evolved over time, how pollution interacted with infectious diseases and other causes of death, etc. This enriches our understanding of London’s history while opening up a range of new possibilities for studying the impact of air pollution over the long run.
Werner Troeksen (University of Pittsburgh) Nicola Tynan (Dickinson College) Yuanxiaoyue (Artemis) Yang (Harvard T.H. Chan School of Public Health)
The United Nations Sustainable Development Goals aim to ensure access to water and sanitation for all. This means not just treating water but supplying it reliably. Lives are at stake because epidemiological research shows that a reliable, constant supply of water reduces water-borne illness.
Nineteenth century London faced the same challenge. Not until 1886 did more than half of London homes have water supplied 24 hours a day, 7 days a week. The move to a constant water supply reduced mortality. For every 5% increase in the number of households with a constant supply, deaths from water-borne illnesses fell 3%.
During Victoria’s reign, eight water companies supplied the metropolis with water: 50% from the river Thames, 25% from the river Lea and 25% from wells and springs. By the 1860s, the companies filtered all surface water and Bazalgette’s intercepting sewer was under construction. Still, more than 80% of people received water intermittently, storing it in cisterns often located outside the house, uncovered or beside the toilet.
Rapid population and housing growth required the expansion of the water network and companies found it easier to introduce constant service in new neighbourhoods. Retrofitting older neighbourhoods proved challenging and risked a substantial waste of scarce water. The Metropolis Water Act of 1871 finally gave water companies the power to require waste-limiting fixtures. After 1871, new housing estates received a constant supply of water immediately, while old neighbourhoods transitioned slowly.
As constant water supply reached more people, mortality from diarrhoea, dysentery, typhoid and cholera combined fell. With 24-hour supply, water was regularly available for everyone without risk of contamination. Unsurprisingly, poorer, crowded districts had higher mortality from water-borne diseases.
Even though treated, piped water was available to all by the mid-nineteenth century, everyone benefitted from the move to constant service. By the time the Metropolitan Water Board acquired London’s water infrastructure, 95% of houses in the city received their water directly from the mains.
According to Sergio Campus, water and sanitation head at the Inter-American Development Bank, the current challenge in many places is providing a sustainable and constant supply of water. In line with this, the World Bank’s new Water Supply, Sanitation, and Hygiene (WASH) poverty diagnostic has added frequency of delivery as a measure of water quality, in addition to access, water source and treatment.
Regularity of supply varies substantially across locations. London’s experience during the late Victorian years suggest that increased frequency of water supply has the potential to deliver further reductions in mortality in developing countries beyond the initial gains from improved water sources and treatment.