Policymakers have recently devoted significant attention to water in an effort to address health inequalities around the world, most notably including improving access to clean water as one of the United Nations Sustainable Development Goals (see here). While the long-run impacts of the water interventions taking place today in developing countries may not be known for many years, much can be learned by the historical experience of expanding access to clean water in the now-rich world. To this end, there are several historical studies of the relationship between water quality and mortality, though most have largely focused on the U.S. experience in the late 19th and early 20th centuries (e.g., Alsan and Goldin 2019), by which time clean water and sanitation were already widely understood to have a direct impact on health. This raises the possibility that other unobserved variables, correlated with access to clean water, might be at least partly responsible for the observed beneficial impacts. In contrast, my research evaluates the impact of an improvement in water quality on mortality during a period prior to the understanding that water contamination could compromise health, namely, the widespread adoption of tea drinking in England which began in the 18th century (see here). Since brewing tea required boiling water, now understood to be a method of water purification, the rise of tea consumption in 18th century England would have resulted in an accidental improvement in the poor quality of water available during the Industrial Revolution. Although the link between increased tea consumption, health, population, and economic growth has been hypothesized by several historians, including MacFarlane and MacFarlane (2003) and Mair and Hoh (2009), my study is the first to provide quantitative evidence on this relationship.
Evaluating the Impact of Tea Drinking on Mortality Rates
To investigate this hypothesis, I compare the period before and after the widespread adoption of tea in England, across areas that varied in their initial levels of water quality, and check whether those areas with worse water quality to begin with benefited more from the introduction of tea. I use the Tea and Windows Act of 1784 to identify when the practice of tea drinking became commonplace, since it dramatically reduced the tea tax from 119 to 12.5 percent (Mair and Hoh 2009), and thus enabled consumption even among the poorest peasants. Of course, water quality was not measured during this period, so I utilize two proxies for initial water quality based on local geographical features: parish elevation and, separately, the number of running water sources in an area, as given by the main rivers near that location.
The figures above use the latter water quality proxy to show mortality differences across high and low water quality parishes over time in relation to the 1785 drop in the tea tariff which dramatically increased the availability of tea. While both high and low water quality parishes see a decline in deaths following the widespread adoption of tea, the decline in deaths is larger in lower water quality parishes. In short, the parishes with the worst water quality saw the biggest health benefit from drinking tea. This is made clear in Panel B which graphs the difference in mortality across the two types of parishes (low-high water quality areas) and shows that difference falls below zero after the drop in the tea tariff. Together, these estimates suggest a drop in mortality rates of roughly 25% in low water quality areas and a more modest drop of 7% in better water quality parishes, implying an overall improvement in mortality rates associated with tea on the order of 18%.
Separately, I also utilize actual tea import data at the national level interacted with the aforementioned proxies for water quality to investigate whether positive shocks to tea imports resulted in larger declines in mortality rates in areas where water quality was initially worse. Again, the results are consistent with an important role for tea in improving the health of the population. In periods following larger imports of tea, parishes with high and low water quality levels both saw a reduction in mortality rates, but parishes with worse water quality saw a bigger decline. These results hold using either water quality measure and are robust to controlling for wages and interacted variables capturing distance to market and alternative imports, ruling out the possibility that the correlation was driven by some other economic factor. The magnitudes of the estimates can be interpreted to suggest that a given increase in tea imports reduced mortality by about 1.4% more in low water quality areas relative to high water quality areas.
Overall, the results from both empirical strategies suggest that tea was associated with larger declines in mortality rates in areas that had worse water quality to begin with. To provide further support for the mechanism behind these relationships, namely, boiled water, I use cause-specific death data from London to show that higher tea imports curbed deaths from water-borne diseases such as dysentery, but did not significantly affect deaths that were not directly linked to water quality . Thus, the totality of the results point to the importance of tea, and in particular the boiling of water, in reducing mortality rates across England during this important period in economic development.
Broader Impacts of Beverages on Human Health
Of course, other beverages may also have played a role in health and economic development over this period of time, as conjectured by historians elsewhere (see for example Standage, 2006). For example, beer has a long history in England and would also have represented an improved drinking water source relative to plain water which carried greater risk of contamination. In ongoing work with my coauthor James Flynn (see here), we evaluate the quantitative impact of beer on mortality in England during the Industrial Revolution and use a wide range of empirical strategies and data sources to show that beer scarcity was associated with higher mortality, especially in the summer months when mortality was more likely to be driven by water-borne illnesses related to contaminated drinking water.
Both the tea and beer studies represent an important contribution to the economics and policy literature because unlike deliberate policy experiments, in these cases water quality was improved without design or costly intervention, but instead through culture and custom that ultimately proved highly beneficial for long-run economic development. As such, public health policymakers today may draw lessons from this historical experience as to the importance of cultural adoption to any change in health practice as well as the most cost-effective strategies for improving public health in areas where changes to infrastructure or technologies may not be feasible.
- Alsan Marcella and Claudia Goldin. 2019. “Watersheds in Child Mortality: The Role of Effective Water and Sewerage Infrastructure, 1880–1920.” Journal of Political Economy, 127(2): 586-638.
- Antman, Francisca M. Forthcoming. “For Want of a Cup: The Rise of Tea in England and the Impact of Water Quality on Mortality.” Review of Economics and Statistics.
- MacFarlane, Alan and Iris MacFarlane. 2003. The Empire of Tea: The Remarkable History of the Plant that Overtook the World. New York: The Overlook Press.
- Mair, Victor H. and Erling Hoh. 2009. The True History of Tea. London: Thames and Hudson.Standage, Tom. 2006. A History of the World in Six Glasses. New York: Walker Publishing.
Associate Professor (University of Colorado Boulder)
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